U.S. patent application number 16/741184 was filed with the patent office on 2020-05-14 for radio communication system, base station, and communication terminal.
This patent application is currently assigned to FUJITSU LIMITED. The applicant listed for this patent is FUJITSU LIMITED. Invention is credited to SHINICHIRO AIKAWA, Takayoshi Ode, Yoshiaki Ohta.
Application Number | 20200154284 16/741184 |
Document ID | / |
Family ID | 57247918 |
Filed Date | 2020-05-14 |
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United States Patent
Application |
20200154284 |
Kind Code |
A1 |
Ode; Takayoshi ; et
al. |
May 14, 2020 |
RADIO COMMUNICATION SYSTEM, BASE STATION, AND COMMUNICATION
TERMINAL
Abstract
A base station includes a transmitter configured to transmit to
a terminal a first message; a receiver configured to receive from
the terminal a second message including a capability information,
the capability information including information which indicates
whether or not the terminal is capable of using a first frequency
for either uplink or downlink communication; and a processor
configured to performs communication by using the first frequency
together with a second frequency when the terminal is capable of
using the first frequency for the communication.
Inventors: |
Ode; Takayoshi; (Yokohama,
JP) ; AIKAWA; SHINICHIRO; (Yokohama, JP) ;
Ohta; Yoshiaki; (Yokohama, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
FUJITSU LIMITED |
Kawasaki-shi |
|
JP |
|
|
Assignee: |
FUJITSU LIMITED
Kawasaki-shi
JP
|
Family ID: |
57247918 |
Appl. No.: |
16/741184 |
Filed: |
January 13, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15805833 |
Nov 7, 2017 |
10575186 |
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16741184 |
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PCT/JP2015/063827 |
May 13, 2015 |
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15805833 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04W 16/32 20130101;
H04W 72/04 20130101; H04W 72/0453 20130101; H04W 16/14 20130101;
H04W 72/048 20130101 |
International
Class: |
H04W 16/14 20060101
H04W016/14; H04W 72/04 20060101 H04W072/04 |
Claims
1. A base station comprising: a transmitter configured to transmit
to a terminal a first message; a receiver configured to receive
from the terminal a second message including a capability
information, the capability information including information which
indicates whether or not the terminal is capable of using a first
frequency for either uplink or downlink communication; and a
processor configured to performs communication by using the first
frequency together with a second frequency when the terminal is
capable of using the first frequency for the communication.
2. The base station according to claim 1, wherein the first
frequency is used as an unlicensed frequency, whereas the second
frequency is used as a licensed frequency.
3. The base station according to claim 1, wherein the transmitter
transmits, to the terminal, the first message for requesting
capability information of the terminal.
4. The base station according to claim 1, wherein the receiver
receives, from the terminal, the second message after transmitted
the first message.
5. A terminal comprising: a receiver configured to receive from a
base station a first message; a transmitter configured to transmit
to the base station a second message including a capability
information to the base station, the capability information
including information which indicates whether or not the terminal
is capable of using a first frequency for either uplink or downlink
communication; and a processor configured to performs communication
by using the first frequency together with a second frequency when
the terminal is capable of using the first frequency for the
communication.
6. The terminal according to claim 5, wherein the first frequency
is used as an unlicensed frequency, whereas the second frequency is
used as a licensed frequency.
7. The terminal according to claim 5, wherein the receiver receives
from the base station the first message for requesting capability
information of the terminal.
8. The terminal according to claim 5, wherein the transmitter
transmits to the base station the second message after received the
first message.
9. The terminal according to claim 5, wherein the transmitter
transmits to the base station the second message according to the
first message.
10. The communication system including a base station and a
terminal, the communication system comprising: The base station
configured to: transmit to the terminal a first message; receive
from the terminal a second message including a capability
information, the capability information including information which
indicates whether or not the terminal is capable of using a first
frequency for either uplink or downlink communication; and performs
communication by using the first frequency together with a second
frequency when the terminal is capable of using the first frequency
for the communication; and, the terminal configured to: receive
from the base station the first message; and transmit to the base
station the second message.
Description
[0001] This application is a continuation of U.S. application Ser.
No. 15/805,833, filed Nov. 7, 2017, now pending, which is a
continuation application of International Application
PCT/JP2015/063827 filed on May 13, 2015 and designating the U.S.,
the entire contents of each are incorporated herein by
reference.
FIELD
[0002] The present invention relates to a radio communication
system, a base station, a communication terminal, and a radio
communication system controlling method.
BACKGROUND
[0003] At present, 3rd Generation Partnership Project (3GPP) is
reviewing the specifications of Long Term Evolution (LTE) systems
and LTE-Advanced systems. For LTE, the specifications of LTE
Releases 8 to 12 have been defined. In Japan, various
telecommunications carriers are providing services on the basis of
Release 8.
[0004] Further, LTE-Advanced systems (release 10 and later), which
are developed forms of LTE systems, have currently been reviewed.
The specifications have been defined up to Release 12, and Release
13 is being reviewed. In Korea, services were started in June 2013.
In Japan, one telecommunications carrier started a service in June
2014, and another telecommunications carrier also started a service
in March 2015.
[0005] In LTE Release 10, i.e., LTE-Advanced systems, a
configuration described below, for example, may be used. An
LTE-Advance system includes a base station (or a base station
apparatus; both of which will hereinafter be referred to as a "base
station") called an "evolved Node B (eNB)" and a communication
terminal (or a terminal; both of which will hereinafter be referred
to as a "communication terminal") called a "User Equipment (UE)".
Further, the base station serves as a transmitting apparatus (a
transmitter or a transmitting station) that performs downlink
transmission to the communication terminal and also serves as a
receiving apparatus (a receiver or a receiving station) that
receives uplink signals from the terminal. Similarly, the
communication terminal serves as a receiving apparatus (a receiver
or a receiving station) that receives downlink transmission from
the base station and also serves as a transmitting apparatus (a
transmitter or a transmitting station) that performs uplink
transmission to the base station. Further, the LTE-Advanced system
includes a Mobility Management Entity (MME) configured with a
controlling apparatus that connects to the Internet called a core
network. Further, the LTE-Advanced system includes a Serving Gate
Way (S-GW) configured with a server used for transferred data such
as user data. Further, the LTE-Advanced system includes S1 serving
as an interface between the MME/S-GW and the eNB, as well as X2
serving as an interface between eNBs. In this situation, S1 and X2
are each an interface using Transmission Control Protocol/Internet
Protocol (TCP/IP).
[0006] Further, the base station has one cell, which is a
communication area, and performs communication with any of the
communication terminals contained in the cell. Also, as a result of
communication performed between base stations, communication
terminals contained in mutually the same cell or mutually different
cells are able to communicate with one another. In this regard,
because each base station has only one band, the terms "base
station", "cell", and "band" may be treated as having the same
meaning in the explanations below.
[0007] Further, other examples of configurations of LTE-Advanced
systems include the following: An LTE-Advanced system includes an
HeNB (Home eNB) of which the cell is smaller than regular cells and
which may be installed indoor (e.g., in a home or an office) and an
HeNB GW serving as a server for the HeNB. Further, the LTE-Advanced
system may include S1 serving as an interface between the MME/S-GW
and the eNB and HeNB. Further, the LTE-Advanced system may include
X2 serving as an interface between eNBs, between HeNBs, and among
the eNB, an X2-GW, and the HeNB. Further, for the communication
between a base station and a communication terminal, a relay
apparatus (a relay node) may be used to realize a relay
transfer.
[0008] For these LTE-Advanced systems, a technique called Carrier
Aggregation (CA) has been proposed. In LTE systems, it is possible
to set an uplink/downlink bandwidth (or a system bandwidth) to 1.4
MHz, 3 MHz, 5 MHz, 10 MHz, 15 MHz, or 20 MHz. The band set in this
situation is defined as a component carrier. The reason why the
plurality of bandwidths are set is that the configuration is based
on the premise that bandwidths allocated to conventional systems
such as Global System for Mobile communication (GSM [registered
trademark]) systems and Wideband Code Division Multiple Access
(W-CDMA) systems will be used without any modification applied
thereto.
[0009] However, it is desirable to configure LTE systems so as to
be able to transfer data at higher speeds than in the conventional
GSM and W-CDMA systems. For this reason, it is desirable to
configure LTE systems to have a wider bandwidth than the
conventional systems. Generally speaking, bands used in radio
communication systems vary in accordance with circumstances in each
country. Further, because the countries in Europe border one
another by land, the frequency bands being used are adjusted among
countries in consideration of interference. As a result, the
bandwidths that are usable in radio communication systems in each
country are small in number and chopped in small pieces. To cope
with this situation, for the purpose of realizing wider bands in
LTE systems, a method has been introduced to obtain wider bands by
integrating the small and chopped-up bands together. The method for
obtaining wider bands by integrating the small and chopped-up bands
together is the CA process. In other words, the CA is a technique
by which communication is performed between at least one
transmitting apparatus and at least one receiving apparatus by
using a plurality of frequency bands at the same time and is a
technique by which communication is performed between one
transmitting apparatus and at least one receiving apparatus by
using a plurality of communication frequency bands at the same
time. As long as these conditions are satisfied, possible
configurations of the radio communication system of the present
disclosure are not limited to those using the CA.
[0010] When a CA process is performed, a cell using a main cell is
set. This cell is called a primary cell. The primary cell may be
referred to as the first cell, the first band, a main band, or a
main cell. In the following sections, a primary cell will be
referred to as a "PCell".
[0011] In a CA process, a cell is added to or integrated with the
PCell. The additional cell is called a secondary cell. The
secondary cell may be referred to as the second cell, a secondary
band, an extended band, or a subband. In the following sections, a
secondary cell will be referred to as an "SCell".
[0012] These cells are obtained by dividing a band allocated to a
system (e.g., W-CDMA or LTE) into sections on the basis of the
frequency bandwidth structuring the system (a system bandwidth). It
is possible to multiplex users in each band, i.e., to realize
multiple access. Further, by scheduling radio resources of data
channels that use each of the bands and allocating the radio
resources to one or more terminals, it is possible to realize user
multiplex. These cells can structure one system. In other words,
these cells are different from using blocks (sets or clusters) that
are obtained by putting multiple subcarriers together to form
allocation units of radio resources for the purpose of realizing
user multiplex in an Orthogonal Frequency-Division Multiple Access
(OFDMA) scheme.
[0013] In CA processes defined in LTE Releases 10 to 12, it is
possible to set seven SCells at maximum. In other words, it is
possible to realize a CA process by using eight Component Carriers
(CCs) at maximum, including a PCell. That is to say, the CA process
is a technique used for integrating the PCell with at least one
SCell. At present, it is considered to set the maximum number of
SCells to 32. Further, CA processes may be classified depending on
whether the frequencies of the PCell and the SCell are continuous
or not continuous, and whether the frequencies are included in
mutually the same frequency band or not. Further, CA processes may
be classified depending on whether control information used for
data communication that uses an SCell is transferred by the SCell
or transferred by a PCell or another SCell. In this situation, the
data communication using an SCell uses a Physical Downlink Shared
Channel (PDSCH), which is a downlink radio shared channel. Further,
the control information for the data communication using an SCell
is transmitted by using a Physical Downlink Control Channel
(PDCCH), which is a downlink radio control channel.
[0014] In addition, as a method for further increasing the
communication capacity, it has been put into practice to reduce the
number of communication terminals contained in each cell and to
increase the communication speed of each communication terminal, by
reducing the size of each cell to a smaller area. Such cells having
a smaller area are called micro cells, pico cells, femtocells, or
small cells. Further, a configuration has been introduced in which,
when a CA process is introduced, the PCell is arranged to be a
macro cell (a large-area cell), whereas a cell having a smaller
area as described above is used as the SCell.
[0015] The configuration of the CA process in which the PCell is
configured with a macro cell, while the SCell is configured with a
cell which has a smaller area and at least a part of which overlaps
the PCell may be referred to as an umbrella cell configuration or a
hierarchical cell configuration. Examples of methods for realizing
the umbrella cell configuration include the following: One method
is to connect the PCell and the SCell to each other by using an X2
interface, which is an inter-base-station interface and to transfer
user data between the PCell and the SCell. Another method is to
perform a signal processing process in the PCell, to convert either
a baseband signal or a radio signal into an optical signal, and to
connect the PCell and the SCell to each other. Yet another method
is to connect the PCell and the SCell to each other with regular
radio communication. It is possible to select and use any of these
methods depending on the purpose of use and application.
[0016] Further, for cellular systems, the frequency bands to be
used are determined by law, in consideration of circumstances in
each country, on the basis of international allocations of
frequencies. Examples of cellular systems include Wideband Code
Division Multiple Access (W-CDMA), LTE, LTE-Advanced, and Worldwide
Interoperability for Microwave Access (WiMAX) (registered
trademark). Further, the frequency bands thereof are assigned to
telecommunications carriers by using methods such as an auction
among the telecommunications carriers. In other words, as a result
of designating a frequency band to be used and giving a license to
each telecommunications carrier, each of the telecommunications
carriers is permitted to use the designated frequency band for use.
The frequency bands of which the use is permitted in this manner
are called "licensed bands".
[0017] In contrast, there is another system in which it is possible
to perform communication without having a license, by performing
the communication with transmission power equal to or lower than a
maximum transmission power level determined by law. This system is
called a specified low power system. Further, there are also
frequency bands in which frequencies can freely be used without a
license, as long as the transmission power is equal to or lower
than a level determined by law, such as an Industry Science Medical
(ISM) band or the 5 GHz band. These frequency bands that are usable
without a license are called "unlicensed bands". Examples of
systems that use unlicensed bands include a Wireless Fidelity
(Wi-Fi) (The institute of Electrical and Electronics Engineers,
Inc. [IEEE] 802.11a).
[0018] Unlicensed bands are freely used by a large number of
systems such as a plurality of Wi-Fi systems. Accordingly, on the
basis of the philosophy of the Radio Act which states that
communication of other systems shall not be hindered, Wi-Fi uses,
for example, Carrier Sense Multiple Access/Collison Avoidance
(CSMA/CA). CSMA/CA is a scheme by which, before data or the like is
transmitted on a certain frequency, it is checked to see whether or
not the frequency is being used by any other system. With this
arrangement, it is possible to prevent the hindrance on other
communication activities. Further, in an unlicensed band, no
specific system is able to use a frequency in an exclusive
manner.
[0019] In this regard, as mentioned above, the CA process is
introduced to LTE-Advanced for the purpose of increasing the
communication volume. Further, by increasing the frequency bands in
use and by making the frequency higher, the goal of increasing the
communication volume has been addressed. An example of increasing
the frequency bands in use is realized by adding the 3.5 GHz band
to the 1.7 GHz used by mobile phones and the like. However, we are
facing a situation where only increasing the frequency bands in use
is not able to address the goal of increasing the communication
volume. In other words, because the frequency resources are finite,
a problem is arising where usable frequencies may be exhausted.
[0020] To cope with this situation, conventional techniques are
known by which an unlicensed band and a licensed band are used. For
example, according to a conventional technique, on the basis of
registered system IDs, a licensed band is used outdoor, whereas an
unlicensed band is used indoor. Further, according to another
conventional technique, a carrier aggregation process is performed
by using a licensed band and an unlicensed band. According to yet
another conventional technique, a carrier aggregation process is
performed in a licensed band and an unlicensed band while using
group IDs, and a synchronization process is performed by using the
licensed band.
[0021] Examples of techniques related to LTE include a conventional
technique by which control is exercised while using numbers or IDs
in an LTE network.
[0022] Patent Document 1: Japanese Laid-open Patent Publication No.
2003-018642
[0023] Patent Document 2: Japanese National Publication of
International Patent Application No. 2015-505436
[0024] Patent Document 3: Japanese National Publication of
International Patent Application No. 2014-500685
[0025] Patent Document 4: Japanese Patent No. 4515460
[0026] Non Patent Document 1: TS23.003V8.16.0 "3rd Generation
Partnership Project; Technical Specification Group Core Network and
Terminals; Numbering, addressing and identification (Release
8)"
[0027] Non Patent Document 2: TS23.003V8.16.0 "3rd Generation
Partnership Project; Technical Specification Radio Access Network
Meeting #65 RP-141664 Edinburgh, Scotland, 9-12 Sep. 2014"
[0028] According to the conventional techniques, however, a problem
remains as to how the communication terminal is made to recognize
the frequency of the unlicensed band as the frequency to be used in
the communication. For example, according to the conventional
technique by which a licensed band is used outdoor, while an
unlicensed band is used indoor, the procedure of having the
communication terminal recognize the frequency of the unlicensed
band is not taken into consideration. For this reason, it is
difficult to perform communication while ensuring that the
unlicensed band is used.
[0029] Further, also according to the conventional technique by
which the CA is implemented by using a licensed band and an
unlicensed band, the procedure of having the communication terminal
recognize the frequency of the unlicensed band is not taken into
consideration. For this reason, also with this conventional
technique, it is difficult to perform communication while ensuring
that the unlicensed band is used.
[0030] Further, also according to the conventional technique by
which the CA is implemented between a licensed band and an
unlicensed band while using group IDs so as to perform a
synchronization process by using the licensed band, the procedure
of having the communication terminal recognize the frequency of the
unlicensed band is not taken into consideration. For this reason,
also with this conventional technique, it is difficult to perform
communication while ensuring that the unlicensed band is used.
[0031] In view of the circumstances described above, it is an
object of the present disclosure to provide a radio communication
system, a base station, a communication terminal, and a radio
communication system controlling method capable of performing
communication while ensuring that an unlicensed band is used.
SUMMARY
[0032] According to an aspect of the embodiments, A radio
communication system including a base station and a communication
terminal, wherein the base station includes: a controlling unit
that controls whether or not a first frequency is to be used for
communication; a first communicating unit that, when the first
frequency is not to be used for the communication, performs
communication by using a second frequency and that, when the first
frequency is to be used for the communication, performs
communication by using the first frequency and the second frequency
at a same time; and a notifying unit that, when the first frequency
is to be used for the communication, notifies the communication
terminal of the first frequency, and the communication terminal
includes: a second communicating unit that, when being notified of
the first frequency by the notifying unit, performs communication
by using the first frequency and the second frequency.
[0033] The object and advantages of the invention will be realized
and attained by means of the elements and combinations particularly
pointed out in the claims.
[0034] It is to be understood that both the foregoing general
description and the following detailed description are exemplary
and explanatory and are not restrictive of the invention.
BRIEF DESCRIPTION OF DRAWINGS
[0035] FIG. 1 is a schematic diagram of a radio communication
system according to a first embodiment.
[0036] FIG. 2 is a block diagram of base stations according to the
first embodiment.
[0037] FIG. 3 is a block diagram illustrating details of a physical
layer processing unit and a licensed band controlling unit.
[0038] FIG. 4 is a drawing illustrating an example of system
information.
[0039] FIG. 5 illustrates a mapping table indicating a
correspondence relationship among a cell ID group N.sup.(1).sub.ID,
m.sub.0 values, and m.sub.1 values.
[0040] FIG. 6 is a drawing illustrating a structure of a frame.
[0041] FIG. 7 is a drawing for explaining positional arrangements
of a Primary Synchronization Signal (PSS), a Secondary
Synchronization Signal (SSS), and a pilot signal in one
subframe.
[0042] FIG. 8 is a block diagram illustrating details of a physical
layer processing unit and an unlicensed band controlling unit.
[0043] FIG. 9 is a block diagram illustrating a communication
terminal.
[0044] FIG. 10 is a sequence chart of a synchronization process and
a radio link quality measuring process.
[0045] FIG. 11A is a sequence chart of a contention based random
access procedure.
[0046] FIG. 11B is a sequence chart of a non-contention based
random access procedure.
[0047] FIG. 12 is a sequence chart of an SCell connection in the
radio communication system according to the first embodiment.
[0048] FIG. 13 is a sequence chart illustrating a schematic
configuration of a CA process performed in the radio communication
system according to the first embodiment.
[0049] FIG. 14 is a flowchart illustrating CA process performed by
a base station according to the first embodiment.
[0050] FIG. 15 is a flowchart illustrating a CA process performed
by a communication terminal according to the first embodiment.
[0051] FIG. 16 is a hardware diagram of a base station.
[0052] FIG. 17 is a hardware diagram of a communication
terminal.
[0053] FIG. 18A is a table illustrating examples of terminal
categories.
[0054] FIG. 18B is a table illustrating other examples of terminal
categories.
[0055] FIG. 19A is a sequence chart illustrating an SCell
connection in a radio communication system according to a second
embodiment.
[0056] FIG. 19B is a sequence chart illustrating details of a
terminal category notifying process.
[0057] FIG. 20 is a flowchart illustrating a CA process performed
by a base station according to a second embodiment.
[0058] FIG. 21A is a flowchart illustrating a CA process performed
by a communication terminal according to the second embodiment.
[0059] FIG. 21B is a flowchart illustrating details of a terminal
category notifying process.
[0060] FIG. 22 is a block diagram of a Centralized Base Band Unit
(CBBU) of a base station according to a third embodiment.
[0061] FIG. 23 is a block diagram of a Remote Radio Head (RRH) of
the base station according to the third embodiment.
[0062] FIG. 24 is a block diagram of a base station according to a
fourth embodiment.
[0063] FIG. 25 is a schematic diagram illustrating processing units
corresponding to layers in base stations having a PCell and an
SCell and a data transfer process.
[0064] FIG. 26A is a diagram illustrating a configuration in which
data is divided in a upper layer apparatus.
[0065] FIG. 26B is a diagram illustrating a configuration in which
a Packet Data Convergence Protocol (PDCP) processing unit is used
in common.
[0066] FIG. 26C is a diagram illustrating a configuration in which
a PDCP processing unit and a Radio Link Control (RLC) processing
unit are used in common.
[0067] FIG. 26D is a diagram illustrating a configuration in which
a PDCP processing unit, an RLC processing unit, and a Media Access
Control (MAC) processing unit are used in common.
[0068] FIG. 27A is a diagram illustrating a configuration in which
data is transferred from a PDCP processing unit of a base station
using a licensed band to an RLC processing unit of a base station
using an unlicensed band.
[0069] FIG. 27B is a diagram illustrating a configuration in which
data is transferred from a PDCP processing unit of a base station
using a licensed band to an MAC processing unit of a base station
using an unlicensed band.
[0070] FIG. 28A is a diagram illustrating a configuration in which
data is divided in a upper layer apparatus within one base
station.
[0071] FIG. 28B is a diagram illustrating a configuration in which
a PDCP processing unit is used in common within one base
station.
[0072] FIG. 28C is a diagram illustrating a configuration in which
a PDCP processing unit and an RLC processing unit are used in
common within one base station.
[0073] FIG. 28D is a diagram illustrating a configuration in which
a PDCP processing unit, an RLC processing unit, and a MAC
processing unit are used in common within one base station.
DESCRIPTION OF EMBODIMENTS
[0074] Embodiments of a radio communication system, a base station,
a communication terminal, and a radio communication system
controlling method of the present disclosure will be explained in
detail below, with reference to the drawings. The radio
communication system, the base station, the communication terminal,
and the radio communication system controlling method of the
present disclosure are not limited by the embodiments described
below. In other words, although an LTE system is explained as an
example below, possible embodiments are not limited to LTE systems.
The present disclosure is also applicable to other systems such as
W-CDMA systems or fifth-generation mobile communication systems.
Further, the present disclosure is not limited to multiple access
schemes such as Time Division Multiple Access (TDMA), CDMA, OFDMA,
Single Carrier Frequency-Division Multiple Access (SC-FDMA), and
Non-orthogonal Multiple Access (NOMA). Furthermore, the radio
communication system controlling method is not limited, either.
First Embodiment
[0075] FIG. 1 is a schematic diagram of a radio communication
system according to a first embodiment. As illustrated in FIG. 1,
the radio communication system according to the first embodiment
includes a base station 1, a base station 2, and a communication
terminal 3.
[0076] The base station 1 has a cell 10 serving as a PCell. The
base station 2 has a cell 20 serving as an SCell. Present in the
cell 10 serving as the PCell are cells 20 serving as a plurality of
SCells. The base station 1 and the base station 2 are connected to
each other in a wired manner or in a wireless manner (by radio) and
are capable of transmitting and receiving data to and from each
other. Alternatively, the base station 1 and the base station 2 may
be configured together as one base station. In that situation, the
base station 1 and the base station 2 are connected to each other
on the inside of an apparatus (e.g., via an interface within the
apparatus) so as to be able to transmit and receive data to and
from each other.
[0077] In this regard, in a conventional CA process, for example,
the base station 1 is set with a plurality of CCs so that the CA
process is performed among the CCs of mutually the same base
station (i.e., the base station 1). Currently, however, unlike the
conventional example, performing a CA process between the base
station 1 and another base station, for example, has been
discussed. It means that Dual Cell High Speed Downlink Packet
Access (DC-HSDPA) is implemented between the base station 1 and the
other station. Implementing DC-HSDPA between the base station 1 and
the other station has been defined as a specification and is called
either Dual Band (DB)-HSDPA or DB-DC-HSDPA. Further, Four Carrier
(4C)-HSDPA, which uses four frequencies, is also defined as a
specification.
[0078] The abovementioned schemes such as DC-HSDPA, DB-DC-HSDPA,
and 4C-HSDPA are considered to be equivalent to the CA. In the
following sections, although the CA is used as an example, the
present disclosure is applicable to DC-HSDPA, DB-DC-HSDPA, and
4C-HSDPA, unless noted otherwise.
[0079] Next, details of the base station 1 and the base station 2
will be explained, with reference to FIG. 2. FIG. 2 is a block
diagram of the base stations according to the first embodiment.
[0080] As illustrated in FIG. 2, the base station 1 includes a
Packet Data Convergence Protocol (PDCP) processing unit 101, a
Radio Link Control (RLC) processing unit 102, a Media Access
Control (MAC) processing unit 103, and a physical layer processing
unit 104. Further, the base station 1 includes a licensed band
controlling unit 105. The licensed band controlling unit 105
operates in collaboration with other processing units. For that
reason, the licensed band controlling unit 105 is depicted in the
drawings as extending over the processing units, for the sake of
convenience in illustration; however, in actuality, the licensed
band controlling unit 105 is a processing unit separate from the
other processing units. However, it is also acceptable to decompose
the parts collaborating with the other processing units and to
consider those parts as parts of the other processing units.
[0081] Further, the base station 2 includes a PDCP processing unit
201, an RLC processing unit 202, a MAC processing unit 203, and a
physical layer processing unit 204. In addition, the base station 2
includes an unlicensed band controlling unit 205.
[0082] The PDCP processing units 101 and 201 each communicate with
a upper layer apparatus 4 via a radio interface by using a network
protocol. The upper layer apparatus 4 includes, for example, an MME
and an S-GW. The upper layer apparatus 4 may be considered as a
core network. The PDCP processing units 101 and 201 each have
functions of compressing header information of data, ciphering and
deciphering data, providing integrity protection and integrity
verification of control information. The PDCP processing unit 101
includes a downlink signal processing unit 111 and an uplink signal
processing unit 112. Further, the PDCP processing unit 201 includes
a downlink signal processing unit 211 and an uplink signal
processing unit 212. In the following sections, the PDCP processing
unit 101 will be explained more specifically in an example.
[0083] The downlink signal processing unit 111 receives an input of
a signal such as user data from the upper layer apparatus 4.
Further, the downlink signal processing unit 111 divides a data
packet represented by the received signal into segments (called
segmentation), appends PDCP headers such as sequence numbers
thereto, and generates PDCP Protocol Data Units (PDUs) (RLC Service
Data Units (SDUs)). After that, the downlink signal processing unit
111 outputs the processed transmission signal to a downlink signal
processing unit 121 included in the RLC processing unit 102.
[0084] The uplink signal processing unit 112 receives an input of a
signal such as user data from an uplink signal processing unit 122
included in the RLC processing unit 102. Further, the uplink signal
processing unit 112 concatenates the received PDCP PDUs (RLC SDUs)
together, removes the PDCP headers, and regenerates the PDCP SDUs,
i.e., an IP packet. After that, the uplink signal processing unit
112 transmits the signal resulting from the process, to the upper
layer apparatus 4.
[0085] Further, the PDCP processing unit 101 and the PDCP
processing unit 201 communicate with each other by using PDCP
SDUs.
[0086] The RLC processing units 102 and 202 each have, among
others, an Auto Repeat Request (ARQ) function (a resending process)
and a function of controlling the resending process of signals. The
RLC processing unit 102 includes the downlink signal processing
unit 121 and the uplink signal processing unit 122. Further, the
RLC processing unit 202 includes a downlink signal processing unit
221 and an uplink signal processing unit 222. In the following
sections, the RLC processing unit 102 will be explained more
specifically in an example.
[0087] The downlink signal processing unit 121 included in the RLC
processing unit 102 receives an input of the PDCP PDUs, which are
the signal processed by the downlink signal processing unit 111
included in the PDCP processing unit 101. The downlink signal
processing unit 121 divides the received PDCP PDUs (RLC SDUs) into
segments, appends RLC headers such as sequence numbers thereto, and
generates RLC PDUs. After that, the downlink signal processing unit
121 outputs the generated RLC PDUs to a downlink signal processing
unit 131 included in the MAC processing unit 103.
[0088] The uplink signal processing unit 122 included in the RLC
processing unit 102 receives an input of the RLC PUDs (MAC SDUs),
which is the signal processed by an uplink signal processing unit
132 included in the MAC processing unit 103. The uplink signal
processing unit 122 concatenates the received RLC PDUs together,
removes the RLC headers, and regenerates the RLC SDUs (the PDCP
PDUs). After that, the uplink signal processing unit 122 outputs
the regenerated RLC SDUs to the uplink signal processing unit 112
included in the PDCP processing unit 101.
[0089] The MAC processing units 103 and 203 each have a function of
implementing a Hybrid ARQ (HARQ) with the MAC of the communication
terminal 3. Further, the MAC processing units 103 and 203 each also
have a scheduling function of determining which communication
terminal uplink and downlink data transfers are to be performed
with and selecting a data volume to be transferred, a radio
resource to be used, a modulation method, an encoding ratio, and
the like for the data transfers. Further, the MAC processing units
103 and 203 each have a function of implementing random access and
radio link control. The MAC processing unit 103 includes the
downlink signal processing unit 131 and the uplink signal
processing unit 132. Further, the MAC processing unit 203 includes
a downlink signal processing unit 231 and an uplink signal
processing unit 232. In the following sections, the MAC processing
unit 103 will be explained more specifically in an example.
[0090] The downlink signal processing unit 131 included in the MAC
processing unit 103 receives an input of the MAC SDUs (the RLC
PDUs) from the RLC processing unit 102. The downlink signal
processing unit 131 divides the MAC SDUs into segments (called
segmentation), appends MAC headers such as sequence numbers
thereto, and generates MAC PDUs. Further, according to information
about the scheduling of signals, the downlink signal processing
unit 131 performs a signal scheduling process, i.e., allocates
signals to radio resources. After that, the downlink signal
processing unit 131 outputs the MAC PDUs to a licensed band
transmitting unit 141 included in the physical layer processing
unit 104.
[0091] According to the scheduling, the uplink signal processing
unit 132 included in the MAC processing unit 103 receives an input
of the MAC PDUs from a licensed band receiving unit 142 included in
the physical layer processing unit 104. After that, the uplink
signal processing unit 132 concatenates the MAC PDUs together,
removes the MAC headers, and regenerates the MAC SDUs (the RLC
PDUs). After that, the uplink signal processing unit 132 outputs
the regenerated MAC SDUs to the uplink signal processing unit 122
included in the RLC processing unit 102.
[0092] In a radio physical layer, the physical layer processing
units 104 and 204 each perform a synchronization process, an
equalizing process, a modulating/demodulating process, an error
correction code process, and a Radio Frequency (RF) controlling
process. The physical layer processing unit 104 includes the
licensed band transmitting unit 141 and the licensed band receiving
unit 142. Further, the physical layer processing unit 204 includes
an unlicensed band transmitting unit 241 and an unlicensed band
receiving unit 242. The physical layer processing units 104 and 204
correspond to an example of the "first communicating unit".
[0093] When a W-CDMA system is used, the base station 1 is
structured with the MAC processing unit 103 and the physical layer
processing unit 104, while a Radio Network Controller (RNC)
includes the PDCP processing unit 101 and the RLC processing unit
102. In that situation, the RLC processing unit 102 further has a
function of handover control and the like. In a W-CDMA system, the
base station 2 also has the same configuration.
[0094] Next, details of the physical layer processing unit 104 will
be explained, with reference to FIG. 3. FIG. 3 is a block diagram
illustrating details of the physical layer processing unit and the
licensed band controlling unit. For the licensed band controlling
unit 105, however, FIG. 3 illustrates only some of the functions in
detail that are involved in the physical layer processing
processes.
[0095] The licensed band receiving unit 142 includes a reception
radio unit 151, a demodulating and decoding unit 152, a terminal
capability information extracting unit 153, a radio link quality
information extracting unit 154, and a radio link control
information extracting unit 155.
[0096] The reception radio unit 151 receives, via an antenna, a
signal sent from the communication terminal 3. Further, the
reception radio unit 151 amplifies the received signal and further
converts the signal on a radio frequency into a baseband signal.
After that, the reception radio unit 151 outputs the signal
converted into the baseband signal to the demodulating and decoding
unit 152.
[0097] The demodulating and decoding unit 152 receives an input of
the signal from the reception radio unit 151. After that, the
demodulating and decoding unit 152 performs a demodulating process
on the received signal. Further, the demodulating and decoding unit
152 performs a decoding process on the signal resulting from the
demodulating process. After that, the demodulating and decoding
unit 152 outputs the signal resulting from the processes, to the
uplink signal processing unit 132.
[0098] The terminal capability information extracting unit 153
extracts terminal capability information from the signal sent from
the demodulating and decoding unit 152. The terminal capability
information includes information indicating whether or not the
communication terminal 3 is capable of using an unlicensed band.
After that, the terminal capability information extracting unit 153
outputs the extracted terminal capability information to a terminal
capability information controlling unit 156. In this situation,
being capable of using an unlicensed band (hereinafter "unlicensed
band use capability/incapability") denotes whether or not the
terminal is, as a function thereof, capable of performing
communication by using an unlicensed band. Accordingly, the
capability/incapability is different from being able/unable to use
an unlicensed band based on radio environment such as radio link
quality.
[0099] The radio link quality information extracting unit 154
extracts radio link quality information including a Reference
Signal Received Power (RSRP) level from the signal sent from the
demodulating and decoding unit 152. After that, the radio link
quality information extracting unit 154 outputs the extracted radio
link quality information to a radio link controlling unit 157.
[0100] In this situation, the radio link quality is a collective
term for a reception power level, a pilot reception power level,
reception quality, and pilot reception quality. The reception power
level may be a level of reception electric field strength. Further,
the radio link quality may be referred to as channel state
information (CSI). The pilot reception power level may be expressed
by, for example, an RSRP level for an LTE system and may be
expressed by a Common Pilot Channel Received Signal Code Power
(CPICH RSCP) level for a W-CDMA system. The reception quality may
be expressed by a Signal-to-Interference Ratio (SIR), for example.
The pilot reception quality may be expressed by, for example, a
Reference Signal Received Quality (RSRQ) level for an LTE system
and may be expressed by a value called Common Pilot Channel
received energy per chip divided by the power density (CPICH Ec/NO)
for a W-CDMA system.
[0101] When the SCell is caused to select the communication
terminal 3, the radio link quality information extracting unit 154
extracts radio link quality information of one or more cells, from
the signal sent from the demodulating and decoding unit 152. After
that, the radio link quality information extracting unit 154
outputs the extracted radio link quality information to the radio
link controlling unit 157.
[0102] The radio link control information extracting unit 155
extracts a radio link control signal including a random access
preamble, from the signal sent from the demodulating and decoding
unit 152. Subsequently, the radio link control information
extracting unit 155 obtains the random access preamble from the
radio link control signal. After that, the radio link control
information extracting unit 155 outputs the random access preamble
to the radio link controlling unit 157.
[0103] Subsequently, the radio link control information extracting
unit 155 extracts an input of a scheduled transmission sent from
the communication terminal 3 as a response to the random access
preamble, from the signal sent from the demodulating and decoding
unit 152. After that, the radio link control information extracting
unit 155 outputs the scheduled transmission to the radio link
controlling unit 157.
[0104] The radio link control information extracting unit 155
extracts control information used by the cell 20 for establishing a
radio link, from the signal sent from the demodulating and decoding
unit 152. Further, the radio link control information extracting
unit 155 outputs the extracted control information to be used by
the cell 20 for establishing a radio link, to the radio link
controlling unit 157.
[0105] The licensed band controlling unit 105 includes the terminal
capability information controlling unit 156, the radio link
controlling unit 157, a system information managing and storing
unit 158, and a upper layer processing unit 159.
[0106] By using the terminal capability information, the terminal
capability information controlling unit 156 judges whether or not
the communication terminal 3 is capable of using an unlicensed
band. After that, the terminal capability information controlling
unit 156 notifies the radio link controlling unit 157 of whether or
not the communication terminal 3 is capable of using an unlicensed
band. The terminal capability information controlling unit 156
corresponds to an example of the "controlling unit".
[0107] The radio link controlling unit 157 receives an input of the
random access preamble from the radio link control information
extracting unit 155. After that, the radio link controlling unit
157 exercises control to return a random access response in
response to the random access preamble. More specifically, for
example, the radio link controlling unit 157 generates a Timing
Advanced Indicator (TAI) used for controlling transmission timing
of the communication terminal 3 and exercises control to request
aperiodic radio link measuring processes and radio link measuring
result reporting processes. Further, the radio link controlling
unit 157 outputs control information for the random access response
to a radio link control information generating unit 160.
[0108] Further, the radio link controlling unit 157 receives an
input of the scheduled transmission from the radio link control
information extracting unit 155. After that, the radio link
controlling unit 157 exercises control to transmit a contention
resolution to the communication terminal 3. Subsequently, the radio
link controlling unit 157 outputs control information for the
contention resolution to the radio link control information
generating unit 160.
[0109] When the random access is completed and a radio link has
been established between the device of its own and the
communication terminal 3, the radio link controlling unit 157
instructs a terminal capability information request generating unit
164 to transmit a terminal capability information request. After
that, the radio link controlling unit 157 receives an input of the
information indicating whether or not the communication terminal 3
is capable of using an unlicensed band, from the terminal
capability information controlling unit 156. After that, by using
the unlicensed band use capability/incapability information, the
radio link controlling unit 157 identifies the communication
terminal 3 and identifies a terminal category. For example, the
radio link controlling unit 157 has a list that has terminal
categories therein and was generated by categorizing terminals
according to the unlicensed band use capability/incapability
thereof and the like. The radio link controlling unit 157 instructs
the radio link control information generating unit 160 to generate
control information used for issuing a notification that an
unlicensed band is to be used. Further, the radio link controlling
unit 157 instructs the radio link control information generating
unit 160 to issue a notification about the terminal category of the
communication terminal 3.
[0110] After that, the radio link controlling unit 157 notifies the
system information managing and storing unit 158 that an unlicensed
band is to be used for the communication terminal 3.
[0111] Further, when having determined an aperiodic radio link
quality measuring process is to be performed, which is not
compliant with a measuring periodic cycle (or a measuring result
report periodic cycle; both of which will hereinafter be referred
to as a "measuring periodic cycle"), the radio link controlling
unit 157 notifies the radio link control information generating
unit 160 of the radio link quality measuring process. In that
situation, the radio link controlling unit 157 transmits conditions
for measuring the radio link quality to the radio link control
information generating unit 160. The conditions for measuring the
radio link quality (or issuing a notification about a radio link
quality measuring result) may include, for example, a measuring
periodic cycle and/or a radio resource (e.g., the entire system
bandwidth or a partial bandwidth in the system bandwidth) to be
measured.
[0112] Further, in response to the request for the aperiodic radio
link quality measuring process, the radio link controlling unit 157
receives an input of a radio link quality measuring and calculating
result from the radio link control information extracting unit 155.
After that, on the basis of the obtained radio link quality, the
radio link controlling unit 157 selects a communication terminal to
which downlink data is to be transmitted. In the present example, a
situation will be explained in which the radio link controlling
unit 157 selects the communication terminal 3. After that, the
radio link controlling unit 157 selects a data volume, a radio
resource to be used, a modulation method to be used, an encoding
ratio, and/or the like that are to be applied when the downlink
data is transmitted to the communication terminal 3. In this
situation, the radio resource to be used is a radio resource
structured in a frequency axis direction and a time axis direction,
when an LTE system is used. In contrast, the radio resource to be
used is a spreading code when a W-CDMA system is used.
Subsequently, the radio link controlling unit 157 outputs the
selection results to the radio link control information generating
unit 160.
[0113] Further, the radio link controlling unit 157 receives inputs
of pilot signals transmitted from communication terminals including
the communication terminal 3, from the radio link control
information extracting unit 155. After that, the radio link
controlling unit 157 measures and calculates uplink radio link
quality from the received pilot signals. Subsequently, on the basis
of the radio link quality, the radio link controlling unit 157
selects a communication terminal that is to perform an uplink data
transfer. This process may generally be referred to as a scheduling
process. Only the part of the process to select a terminal may be
referred to as a scheduling process. In the present example, a
situation will be explained in which the radio link controlling
unit 157 selects the communication terminal 3 as a communication
terminal that is to perform the uplink data transfer, on the basis
of the radio link quality.
[0114] Subsequently, the radio link controlling unit 157 selects a
data volume, a radio resource to be used, a modulation method to be
used, an encoding ratio, and/or the like that are to be applied
when the communication terminal 3 transmits the uplink data. In
this situation, the radio resource to be used is a radio resource
structured in a frequency axis direction and a time axis direction,
when an LTE system is used. In contrast, the radio resource to be
used is a spreading code when a W-CDMA system is used.
Subsequently, the radio link controlling unit 157 outputs the
selection results to the radio link control information generating
unit 160.
[0115] Further, the radio link controlling unit 157 monitors the
radio link quality extracted by the radio link quality information
extracting unit 154. After that, when the radio link quality
satisfies a predetermined condition such as the condition where the
difference between the transfer speed to or from the communication
terminal 3 and a predetermined transfer speed exceeds a threshold
value, the radio link controlling unit 157 determines that a CA
process is to be performed. After that, the radio link controlling
unit 157 notifies the upper layer processing unit 159 that the CA
process is to be performed.
[0116] Subsequently, the radio link controlling unit 157 receives
an input of radio link quality information between one or more
cells and the communication terminal 3 from the radio link quality
information extracting unit 154. After that, the radio link
controlling unit 157 selects an SCell on the basis of the obtained
radio link quality information. In the present example, a situation
will be explained in which the radio link controlling unit 157
selects the cell 20 as an SCell. Subsequently, the radio link
controlling unit 157 instructs the radio link control information
generating unit 160 to request control information used for
establishing a radio link from the base station 2. In this
situation, the control information used for establishing a radio
link may be, for example, a dedicated random access preamble
(hereinafter, "dedicated preamble") to be individually assigned to
a terminal or control information used for random access. Further,
the control information used for establishing a radio link includes
system information. The system information includes conditions for
measuring the radio link quality, cell selection information,
neighboring cell information including one or more cell IDs,
Multicast Broadcast Single Frequency Network (MBSFN)-related
information, network identification information, and CA-related
information. Further, the system information include: information
that is broadcast (or transmitted) as control information used in
common among any communication terminals 3 that are either
connected to the cell or attempting to connect to the cell; and
information that is issued as a notification (transmitted) to serve
as control information provided for the individual communication
terminal 3 that is either connected to the cell or attempting to
connect to the cell. The system information may be considered as
control information. Further, in LTE systems (including
LTE-advanced systems) and W-CDMA systems, what corresponds to the
system information is referred to as a system information block
(e.g., a Master Information Block (MIB) or a System Information
Block (SIB)) obtained by putting pieces of system information
together.
[0117] Subsequently, the radio link controlling unit 157 receives
an input of the control information to be used by the cell 20 for
establishing a radio link, from the radio link control information
extracting unit 155. After that, the radio link controlling unit
157 instructs the radio link control information generating unit
160 to issue a notification about the control information to be
used for establishing a radio link.
[0118] After that, the radio link controlling unit 157 receives an
input of the random access preamble for the cell 20 from the radio
link control information extracting unit 155. Further, the radio
link controlling unit 157 exercises control to return a random
access response in response to the random access preamble for the
cell 20. After that, the radio link controlling unit 157 outputs
the control information for the random access response related to
the cell 20, to the radio link control information generating unit
160. As a result of this process, the base station 1 establishes a
radio link with the communication terminal 3, while using the cell
20 as an SCell. The radio link controlling unit 157 corresponds to
an example of the "notifying unit".
[0119] The upper layer processing unit 159 performs a controlling
process over the PDCP processing unit 101, the RLC processing unit
102, and the MAC processing unit 103.
[0120] The licensed band transmitting unit 141 includes the
terminal capability information request generating unit 164, the
radio link control information generating unit 160, a pilot
generating unit 161, a synchronization signal generating unit 162
and a system information generating unit 163, a transmission radio
unit 165, and an encoding and modulating unit 166.
[0121] When the random access is completed and the radio link has
been established between the device of its own and the
communication terminal 3, the terminal capability information
request generating unit 164 receives an instruction from the radio
link controlling unit 157 instructing that a terminal capability
information request be transmitted. After that, the terminal
capability information request generating unit 164 generates a
terminal capability information request. Subsequently, the terminal
capability information request generating unit 164 outputs the
generated terminal capability information request to the encoding
and modulating unit 166 so as to transmit the request to the
communication terminal 3.
[0122] The radio link control information generating unit 160
receives an input of the control information for the random access
response, from the radio link controlling unit 157. After that, the
radio link control information generating unit 160 generates the
random access response by using the obtained control information.
Subsequently, the radio link control information generating unit
160 outputs the generated random access response to the encoding
and modulating unit 166 so as to transmit the random access
response to the communication terminal 3.
[0123] The radio link control information generating unit 160
receives an input of the control information for the contention
resolution from the radio link controlling unit 157. After that, by
using the obtained control information, the radio link control
information generating unit 160 generates the contention
resolution. Subsequently, the radio link control information
generating unit 160 outputs the generated contention resolution to
the encoding and modulating unit 166 so as to transmit the
contention resolution to the communication terminal 3.
[0124] The radio link control information generating unit 160
receives the notification about a radio link quality measuring
process that is not compliant with the measuring periodic cycle,
from the radio link controlling unit 157. In that situation, the
radio link control information generating unit 160 also obtains the
conditions for measuring the radio link quality, from the radio
link controlling unit 157. After that, the radio link control
information generating unit 160 generates a radio link measuring
request by using the conditions for measuring the radio link
quality. Subsequently, the radio link control information
generating unit 160 outputs the generated radio link measuring
request to the encoding and modulating unit 166 so as to transmit
the request to the communication terminal 3.
[0125] Further, the radio link control information generating unit
160 receives, from the radio link controlling unit 157, an input of
the selection results regarding the data volume, the radio resource
to be used, the modulation method to be used, the encoding ratio,
and/or the like that are to be applied when the downlink data is
transmitted to the communication terminal 3. After that, the radio
link control information generating unit 160 generates downlink
control information including the selection results. Subsequently,
the radio link control information generating unit 160 outputs the
generated downlink control information including the selection
results to the encoding and modulating unit 166 so as to transmit
the downlink control information to the communication terminal
3.
[0126] Further, the radio link control information generating unit
160 receives, from the radio link controlling unit 157, an input of
the selection results regarding the data volume, the radio resource
to be used, the modulation method to be used, the encoding ratio,
and/or the like that are to be applied when the communication
terminal 3 transmits the uplink data. After that, the radio link
control information generating unit 160 generates uplink control
information including the selection results. Subsequently, the
radio link control information generating unit 160 outputs the
generated uplink control information including the selection
results to the encoding and modulating unit 166 so as to transmit
the uplink control information to the communication terminal 3.
[0127] Further, the radio link control information generating unit
160 receives an instruction from the radio link controlling unit
157 instructing that control information used for issuing a
notification that an unlicensed band is to be used be generated.
After that, the radio link control information generating unit 160
generates an unlicensed band use notification. Subsequently, the
radio link control information generating unit 160 outputs the
generated unlicensed band use notification to the encoding and
modulating unit 166 so as to transmit the notification to the
communication terminal 3. Further, the radio link control
information generating unit 160 receives an instruction from the
radio link controlling unit 157 instructing that the communication
terminal 3 be notified of the terminal category. After that, the
radio link control information generating unit 160 generates
control information for issuing a notification about the terminal
category. Subsequently, the radio link control information
generating unit 160 outputs the control information for issuing the
notification about the terminal category to the encoding and
modulating unit 166 so as to transmit the control information to
the communication terminal 3.
[0128] Further, when a CA process is to be performed, the radio
link control information generating unit 160 receives an
instruction from the radio link controlling unit 157 instructing
that the control information used for establishing the radio link
be requested from the base station 2. After that, the radio link
control information generating unit 160 generates the request for
the control information used for establishing the radio link.
Subsequently, the radio link control information generating unit
160 outputs the generated request for the control information used
for establishing the radio link to the encoding and modulating unit
166 so as to transmit the request to the base station 2.
[0129] Further, the radio link control information generating unit
160 receives an instruction from the radio link controlling unit
157 instructing that the control information used by the cell for
establishing the radio link be issued as a notification. After
that, the radio link control information generating unit 160
generates control information for issuing the notification about
the control information used by the cell 20 for establishing the
radio link. Subsequently, the radio link control information
generating unit 160 outputs the generated control information for
issuing the notification about the control information used by the
cell 20 for establishing the radio link, to the encoding and
modulating unit 166 so as to transmit the control information to
the base station 2. In that situation, together with the control
information, the radio link control information generating unit 160
may also provide the communication terminal 3 with a notification
about the cell information of the cell 20 including, for example,
cell control information such as a cell ID. Alternatively, the
radio link control information generating unit 160 may separately
provide a notification about information related to the network to
which the cell 20 is connected such as network identification
information.
[0130] Further, the radio link control information generating unit
160 receives an input of the control information for the random
access response related to the cell 20, from the radio link
controlling unit 157. After that, the radio link control
information generating unit 160 generates a random access response
related to the cell 20, by using the obtained control information.
Subsequently, the radio link control information generating unit
160 outputs the generated random access response related to the
cell 20 to the encoding and modulating unit 166 so as to transmit
the random access response to the communication terminal 3.
[0131] The system information managing and storing unit 158 stores
therein and manages system information including the conditions for
measuring the radio link quality, the cell selection information,
the neighboring cell information including one or more cell IDs,
the MBSFN-related information, the network identification
information, the CA-related information, and/or the like. The
contents of the system information stored in the system information
managing and storing unit 158 are illustrated in FIG. 4, for
example. FIG. 4 is a drawing illustrating an example of the system
information. The conditions for measuring the radio link quality
include, for example, a bandwidth to be measured, a measuring
periodic cycle, information about the cell to be measured, and/or
the like. The network identification information is information
identifying the network to which the base station 1 belongs.
[0132] In this situation, the cell IDs may be referred to as cell
identifiers, C(cell)-IDs, physical cell IDs, PC (physical
cell)-IDs, or PCIDs. Each of the cell IDs is an ID used for
identifying a cell. The cell IDs are each used for identifying a
cell in the radio link quality measuring process or a handover
process. In an LTE system, by receiving a synchronization signal in
a standby cell or a connected cell, the communication terminal 3 is
able to recognize the cell ID of the cell.
[0133] For example, the cell IDs may be configured in an LTE system
in the following manner: There are 168 groups each made up of three
cell IDs, so that it is possible to set 504 cell IDs in total. The
cell IDs are calculated by using Mathematical Formula (1) presented
below.
N.sub.ID.sup.cell=3N.sub.ID.sup.(1)+N.sub.ID.sup.(2)
N.sub.ID.sup.(1) 0 to 167
N.sub.ID.sup.(2) 0 to 2 (2)
[0134] 3 GPP does not define how to assign cell IDs. In other
words, even for a single LTE system, for example, the method for
assigning cell IDs may be different among different
telecommunications carriers. In the formula above, N.sup.(2).sub.ID
is considered as the group number of the cell ID, whereas
N.sup.(1).sub.ID is considered as a number within the group.
[0135] After the link is established or before the random access
process is performed, the system information generating unit 163
obtains the network identification information from the system
information managing and storing unit 158. After that, the system
information generating unit 163 generates system information by
using the obtained network identification information. The system
information also includes control information related to random
access. Subsequently, the system information generating unit 163
outputs the generated system information including the network
identification information to the encoding and modulating unit 166
so as to transmit the system information to the communication
terminal 3.
[0136] Further, the system information generating unit 163 obtains
the conditions for measuring the radio link quality from the system
information managing and storing unit 158. After that, the system
information generating unit 163 generates the obtained measuring
conditions for measuring the radio link quality, into system
information. Subsequently, the system information generating unit
163 outputs the generated system information including the
measuring conditions for measuring the radio link quality to the
encoding and modulating unit 166 so as to transmit the system
information to the communication terminal 3. In this situation, the
system information generating unit 163 may provide the
communication terminal with the system information as a
notification serving as individual control information for each of
the communication terminals or may transmit the system information
as common control information that is provided in common to all or
a part of the communication terminals that are standing by
(camping) in the cell 10 or being connected to the cell 10.
Further, the system information may include a measured bandwidth,
priority levels for selecting cells, and/or the like.
[0137] The synchronization signal generating unit 162 calculates a
synchronization signal (a synchronization signal sequence) on the
basis of the cell IDs stored in the system information managing and
storing unit 158. A synchronization signal unit may be configured
with one signal (symbol), but is usually configured with a
plurality of signals (symbols). Accordingly, the synchronization
signal can be called a synchronization signal sequence, but will
hereinafter be generally referred to as a "synchronization signal".
After that, the synchronization signal generating unit 162 outputs
the generated synchronization signal to the encoding and modulating
unit 166 so as to transmit the synchronization signal to the
communication terminal 3. In an LTE system, two types of
synchronization signals are defined as the synchronization signal.
One is called the first synchronization signal (a Primary
Synchronization Signal [PSS]); whereas the other is called the
second synchronization signal (a Secondary Synchronization Signal
[SSS]). In an LTE system, no synchronization channel is present,
and only the synchronization signal is defined. It is noted,
however, that the two types of synchronization signals are, in
actuality, each configured with a plurality of symbols. The present
disclosure is similarly applicable to synchronization channels to
transfer synchronization signals.
[0138] The pilot generating unit 161 calculates a pilot signal (a
pilot signal sequence). Similarly, a pilot signal unit (a pilot or
a pilot symbol) may be configured with one signal (symbol), but is
usually configured with a plurality of signals (symbols).
Accordingly, the pilot signal can be called a pilot signal
sequence, but will hereinafter be generally referred to as a "pilot
signal". After that, the pilot generating unit 161 outputs the
generated pilot signal to the encoding and modulating unit 166 so
as to transmit the pilot signal to the communication terminal 3.
The present disclosure is similarly applicable to a pilot channel
that transfers the pilot signal.
[0139] Next, a process of calculating the PSS and the SSS will be
explained. A method for calculating the PSS can be defined in
Mathematical Formula (2) and Table (1) presented below. In other
words, the PSS is calculated on the basis of the group number
N.sup.(2).sub.ID of the cell ID.
d u ( n ) = { e - j .pi. un ( n + 1 ) 63 n = 0 , 1 , , 30 e - j
.pi. u ( n + 1 ) ( n + 2 ) 63 n = 31 , 32 , , 61 ( 2 )
##EQU00001##
TABLE-US-00001 TABLE 1 N.sub.ID.sup.(2) Root index .sup.u 0 25 1 29
2 34
[0140] Further, the PSS is a Zadoff-Chu sequence (Zadoff-Chu
codes). The Zadoff-Chu sequence represents a Constant Amplitude
Zero Auto Correlation waveform (CAZAC) and is a sequence that is
made of periodic complex signals of the complement of 1 and has an
autocorrelation of zero. In this situation, the PSS is expressed by
mapping the signals of the 62 complex numbers calculated from the
above in the frequency axis direction (a sub-carrier direction) of
Orthogonal Frequency-Division Multiple Access (OFDMA). The PSS is
not scrambled.
[0141] The process of mapping the signals of the 62 complex numbers
is performed according to Mathematical Formula (3) below.
a k , l = d ( n ) , n = 0 , , 61 k = n - 31 + N RB DL N sc RB 2 ( 3
) ##EQU00002##
[0142] In Mathematical Formula (3), (k,l) is a resource element in
the symbols in OFDMA used for transmitting the PSS.
[0143] Further, for example, when the frame structure is of Type 1,
the PSS is mapped in the frequency direction (i.e., the sub-carrier
direction), at the last symbols of slots 0 and 10, i.e., at 1=6 in
a normal subframe. More specifically, the PSS is arranged in the
range of .+-.31 symbols from the frequency center of the six
Resource Blocks (RBs) positioned at the center. The PSS is not
arranged in the five symbols at each of the two ends.
[0144] Due to the positional arrangement at the last symbol in the
time axis direction, the communication terminal 3 is able to
identify the head of each slot. In other words, by using
Mathematical Formula (4) presented below, the communication
terminal 3 is able to bring slots into synchronization.
a k , l = d ( n ) , n = 0 , , 61 k = n - 31 + 6 .times. 12 2 = n +
5 ( 4 ) ##EQU00003##
[0145] Further, a method for calculating the SSS can be implemented
in the following procedure: The expressions d(0), . . . d(61) can
be expressed with two binary sequences having a length of 31 that
can be calculated by using a scramble sequence derived from the
PSS. The two binary sequences having a length of 31 and defining
the SSS can be defined between subframes 0 and 5 by using
Mathematical Formula (5) presented below. The binary sequences may
also be considered as sequences obtained by scrambling sequences
derived from calculations.
d ( 2 n ) = { s 0 ( m 0 ) ( n ) c 0 ( n ) in subframe 0 s 1 ( m 1 )
( n ) c 0 ( n ) in subframe 5 d ( 2 n + 1 ) = { s 1 ( m 1 ) ( n ) c
1 ( n ) z 1 ( m 0 ) ( n ) in subframe 0 s 0 ( m 0 ) ( n ) c 1 ( n )
z 1 ( m 1 ) ( n ) in subframe 5 ( 5 ) ##EQU00004##
[0146] In Mathematical Formula (5), 0.ltoreq.n.ltoreq.30 is
satisfied. Further, it is possible to express m.sub.0 and m.sub.1
by using the cell ID group N.sup.(1).sub.ID as indicated in
Mathematical Formula (6) below.
m 0 = m ' mod 31 m 1 = ( m 0 + m ' / 31 + 1 ) mod 31 m ' = N ID ( 1
) + q ( q + 1 ) / 2 , q = N ID ( 1 ) + q ' ( q ' + 1 ) / 2 30 , q '
= N ID ( 1 ) / 30 ( 6 ) ##EQU00005##
[0147] These expressions can be represented as indicated in the
mapping table in FIG. 5. FIG. 5 illustrates a mapping table
indicating a correspondence relationship among the cell ID groups
N.sup.(1).sub.ID, m.sub.0 values, and m.sub.1 values.
[0148] Further, it is possible to express S.sub.0.sup.(m0) (n) and
S.sub.1.sup.(m1) (n) as indicated in Mathematical Formula (7).
s.sub.0.sup.(m.sup.0.sup.)(n)={tilde over (s)}((n+m.sub.0) mod
31)
s.sub.1.sup.(m.sup.1.sup.)(n)={tilde over (s)}((n+m.sub.1) mod 31)
(7)
[0149] Further, the terms in Mathematical Formula (7) satisfy
Mathematical Formula (8) presented below.
{tilde over (s)}(i)=1-2x(i), 0.ltoreq.i.ltoreq.30
x( +5)=(x( +2)+x( )) mod 2, 0.ltoreq. .ltoreq.25 (8)
[0150] In Mathematical Formula (8), the initial values are x(0)=0,
x(1)=0, x(2)=0, x(3)=0, and x(4)=1.
[0151] Further, it is possible to express c.sub.0(n) and
c.sub.1(n), which are two scramble sequences dependent on the PSS,
by using Mathematical Formula (9) presented below.
c.sub.0(n)={tilde over (c)}((n+N.sub.ID.sup.(2)) mod 31)
c.sub.1(n)={tilde over (c)}((n+N.sub.ID.sup.(2)+3) mod 31) (9)
[0152] In Mathematical Formula (9), N.sup.(2).sub.ID .di-elect
cons.{0, 1, 2}corresponds to one element of the cell ID group
N.sup.(1).sub.ID. Further, the terms in Mathematical Formula (9)
satisfy Mathematical Formula (10) presented below.
{tilde over (c)}(i)=1-2x(i), 0.ltoreq.i.ltoreq.30
x( +5)=(x( +3)+x( )) mod 2, 0.ltoreq. .ltoreq.25 (10)
[0153] In Mathematical Formula (10), the initial values are x(0)=0,
x(1)=0, x(2)=0, x(3)=0, and x(4)=1.
[0154] Further, it is possible to express the scramble sequences
Z.sub.1.sup.(m0) (n) and Z.sub.1.sup.(m1) (n) by using Mathematical
Formula (11) presented below.
z.sub.1.sup.(m.sup.0.sup.)(n)={tilde over (z)}((n+(m.sub.0 mod 8))
mod 31)
z.sub.1.sup.(m.sup.1.sup.)(n)={tilde over (z)}((n+(m.sub.1 mod 8))
mod 31) (11)
[0155] In Mathematical Formula (11), m.sub.0 and m.sub.1 are values
obtained from the mapping table in FIG. 5. Further, the terms in
Mathematical Formula (11) satisfy Mathematical Formula (12)
presented below.
{tilde over (z)}(i)=1-2x(i), 0.ltoreq.i.ltoreq.30
x( +5)=(x( +4)+x( +2)+x( +1)+x( ))mod2, 0.ltoreq. .ltoreq.25
(12)
[0156] In Mathematical Formula (12), the initial values are x(0)=0,
x(1)=0, x(2)=0, x(3)=0, and x(4)=1.
[0157] As explained above, it is possible to express the SSS by
using the mutually-different calculation formulae between when the
transmission is performed by using subframe number 0 (i.e., slot
number 0) and when the transmission is performed by using subframe
number 5 (i.e., slot number 10). Further, the calculation formulae
for the SSS are different between the generated complex signals
identified with odd ordinal numbers and the generated complex
signals identified with even ordinal numbers. Further, similarly to
the PSS, the SSS is a signal sequence configured with 62 complex
numbers.
[0158] Further, c.sub.0(n) and c.sub.1(n) each denote either a
maximal length sequence (an M sequence) or a Pseudo Noise (PN)
sequence and are calculated by using the number N.sup.(1).sub.ID
which is a number in the group number N.sup.(2).sub.ID to which the
cell ID belongs.
[0159] Similarly, S.sub.0.sup.(m0) (n) and S.sub.1.sup.(m1) (n) are
also M sequences and are calculated from the number
N.sup.(1).sub.ID of the group to which the cell ID belongs as well
as m.sub.0 and m.sub.1 derived from N.sup.(1).sub.ID and the
mapping table in FIG. 5.
[0160] Next, a process of mapping the SSS will be explained. The
sequence d(n) expressing the SSS is mapped over resource elements
as indicated in Mathematical Formula (13) presented below.
a k , l = d ( n ) , n = 0 , , 61 k = n - 31 + N RB DL N sc RB 2 l =
{ N symb DL - 2 in slots 0 and 10 for frame structure type 1 N symb
DL - 1 in slots 1 and 11 for frame structure type 2 ( 13 )
##EQU00006##
[0161] In Mathematical Formula (13), it is possible to express the
resource elements (k,l) by using Mathematical Formula (14)
presented below.
k = n - 31 + N RB DL N sc RB 2 l = { N symb DL - 2 in slots 0 and
10 for frame structure type 1 N symb DL - 1 in slots 1 and 11 for
frame structure type 2 n = - 5 , - 4 , , - 1 , 62 , 63 , , 66 ( 14
) ##EQU00007##
[0162] Accordingly, for example, when Type 1 (i.e., Frequency
Division Duplex [FDD]) is used, the SSS is arranged at the
second-to-last symbol of slots 0 and 10. In this situation, the
last symbol is N.sup.DL.sub.symb-1, where "DL" denotes downlink,
while "symb" stands for symbol and denotes a symbol in the time
axis direction. Further, similarly to the PSS, the SSS is arranged
at the center in the frequency axis direction, i.e., in the range
of .+-.31 symbols from the center frequency of the six RBs
positioned at the center of the bandwidth. Further, because the
transmitted SSS is different between slot 0 and slot 10, it is
possible to identify the head of each radio frame.
[0163] Next, a process of calculating the pilot signal will be
explained. In the present example, a Cell-specific Reference Signal
(CRS), which is a pilot signal used in common to the cells, i.e.,
used in common among the terminals that are either connected to the
cell or attempting to connect to the cell, will be explained.
Although not explained below, a method for calculating a pilot
signal is also similarly defined for a UE-specific reference
signal, which is a pilot signal for an individual terminal (which
may be referred to as a Dedicated Reference Signal [DRS]).
Furthermore, a method for calculating a pilot signal is also
similarly defined for a pilot used for transmitting Multimedia
Broadcast and Multicast Service (MBMS) data. The present disclosure
is also applicable to any of these pilot signals, unless noted
otherwise.
[0164] It is possible to express the pilot signal by using
Mathematical Formula (15) presented below.
r l , n s ( m ) = 1 2 ( 1 - 2 c ( 2 m ) ) + j 1 2 ( 1 - 2 c ( 2 m +
1 ) ) , m = 0 , 1 , , 2 N RB max , DL - 1 ( 15 ) ##EQU00008##
[0165] In Mathematical Formula (15), n.sub.s denotes a slot number
of the radio frame, whereas 1 denotes the OFDMA symbol number of
the slot. In Mathematical Formula (15), c(i) denotes a gold
sequence among Pseudo-random Noise (PN) sequences (or Pseudo-random
sequences) of which the initial value is equal to a value expressed
in Mathematical Formula (16A) presented below. The gold sequence is
generated by connecting together two PN sequences having
mutually-different initial values.
c init = 2 10 ( 7 ( n s + 1 ) + l + 1 ) ( 2 N ID cell + 1 ) + 2 N
ID cell + N CP N CP = { 1 for normal CP 0 for extended CP ( 16 A )
##EQU00009##
[0166] It is possible to calculate Mathematical Formula (16A) on
the basis of the slot number Ns, the ID, and 1-bit information
indicating the CP length.
[0167] In this situation, it is possible to calculate the gold
sequence by using Mathematical Formula (16B) presented below.
c(n)=(x.sub.1(n+N.sub.C)+x.sub.2(n+N.sub.C)) mod 2
x.sub.1(n+31)=(x.sub.1(n+3)+x.sub.1(n)) mod 2
x.sub.2(n+31)=(x.sub.2(n+3)+x.sub.2(n+2)+x.sub.2(n+1)+x.sub.2(n))
mod 2 (16B)
[0168] In this situation, the gold sequence has two initial values.
One of the two initial values can be expressed by Mathematical
Formula (16A). The other initial value of the gold sequence is
X.sub.1(0)=1, X.sub.1(n)=0.
[0169] Further, the pilot signal is mapped over a.sup.(p).sub.k,l,
which is used as a reference symbol related to an antenna port p in
the slot ns and can be defined as indicated in Mathematical Formula
(17) presented below.
a k , l ( p ) = r l , n s ( m ' ) k = 6 m + ( v + v shift ) mod 6 l
= { 0 , N symb DL - 3 if p .di-elect cons. { 0 , 1 } 1 if p
.di-elect cons. { 2 , 3 } m = 0 , 1 , , 2 N RB DL - 1 m ' = m + N
RB max , DL - N RB DL ( 17 ) ##EQU00010##
[0170] In Mathematical Formula (17), it is possible to express v as
indicated in Mathematical Formula (18) presented below. The same is
true with v.sub.shift.
v = { 0 if p = 0 and l = 0 3 if p = 0 and l .noteq. 0 3 if p = 1
and l = 0 0 if p = 1 and l .noteq. 0 3 ( n s mod 2 ) if p = 2 3 + 3
( n s mod 2 ) if p = 3 ( 18 ) ##EQU00011##
[0171] Further, processes of mapping the PSS, the SSS, and the
pilot signal will be explained, with reference to FIGS. 6 and 7.
FIG. 6 is a drawing illustrating a structure of a frame. FIG. 7 is
a drawing for explaining positional arrangements of the PSS, the
SSS, and the pilot signal in one subframe. In the following
sections, an example of FDD will be explained.
[0172] In FIG. 6, the numbers in the upper row are numbers of
subframes. In FIG. 6, the numbers in the lower row are slot numbers
of the time slots. As illustrated in FIG. 6, a 10-ms radio frame
includes ten subframes. Further, two slots are assigned to each of
the subframes.
[0173] Further, over slots 0 and 10 indicated with the reference
numerals 501 and 502, the PSS and the SSS are mapped as indicated
in FIG. 7. FIG. 7 illustrates an enlarged view of slot 0. A grid
frame 511 in FIG. 7 indicates a resource element. Further, in FIG.
7, the vertical direction expresses frequencies, whereas the
horizontal direction expresses time. A region 512 denotes the sixth
symbol in slot 0 over which the SSS is mapped. A region 513 denotes
the seventh symbol in slot 0 over which the PSS is mapped. The
pilot signal is mapped over A region 514.
[0174] The encoding and modulating unit 166 receives inputs of
various types of signals from the downlink signal processing unit
131, the terminal capability information request generating unit
164, the radio link control information generating unit 160, the
pilot generating unit 161, the synchronization signal generating
unit 162, and the system information generating unit 163. The
encoding and modulating unit 166 performs an encoding process and a
modulating process on the input signals. Further, the encoding and
modulating unit 166 maps each of the input signals over a radio
frame, a slot, or a subframe. The encoding and modulating unit 166
outputs the mapped signals to the transmission radio unit 165.
[0175] The transmission radio unit 165 receives an input of each of
the signals mapped over a radio frame, a slot, or a subframe, from
the encoding and modulating unit 166. After that, the transmission
radio unit 165 converts the frequency of each of the mapped signals
into a radio frequency. Furthermore, the transmission radio unit
165 amplifies the mapped signals. Subsequently, the transmission
radio unit 165 transmits the mapped signals to the communication
terminal 3, via an antenna.
[0176] Next, details of the physical layer processing unit 204
included in the base station 2 will be explained, with reference to
FIG. 8. FIG. 8 is a block diagram illustrating details of the
physical layer processing unit and the unlicensed band controlling
unit. For the unlicensed band controlling unit 205, however, FIG. 8
illustrates only some of the functions in detail that are involved
in the physical layer processing processes. The base station 2
performs the following processes on the SCell.
[0177] The unlicensed band receiving unit 242 includes a reception
radio unit 251, a demodulating and decoding unit 252, a radio link
quality information extracting unit 254, and a radio link control
information extracting unit 255.
[0178] The reception radio unit 251 receives a signal sent from the
communication terminal 3 via an antenna. After that, the reception
radio unit 251 amplifies the received signal and further converts
the signal on a radio frequency to a baseband signal. After that,
the reception radio unit 251 outputs the signal converted into the
baseband signal to the demodulating and decoding unit 252.
[0179] The demodulating and decoding unit 252 receives an input of
the signal from the reception radio unit 251. After that, the
demodulating and decoding unit 252 performs a demodulating process
on the received signal. Further, the demodulating and decoding unit
252 performs a decoding process on the signal resulting from the
demodulating process. After that, the demodulating and decoding
unit 252 outputs the signal resulting from the processes, to the
uplink signal processing unit 232.
[0180] The radio link quality information extracting unit 254
extracts radio link quality information including an RSRP level
from the signal sent from the demodulating and decoding unit 252.
After that, the radio link quality information extracting unit 254
outputs the extracted radio link quality information to a radio
link controlling unit 257.
[0181] The radio link control information extracting unit 255
extracts a radio link control signal including a random access
preamble, from the signal sent from the demodulating and decoding
unit 252. Subsequently, the radio link control information
extracting unit 255 obtains the random access preamble from the
radio link control signal. After that, the radio link control
information extracting unit 255 outputs the random access preamble
to the radio link controlling unit 257.
[0182] Subsequently, the radio link control information extracting
unit 255 extracts an input of a scheduled transmission sent from
the communication terminal 3 as a response to the random access
preamble, from the signal sent from the demodulating and decoding
unit 252. After that, the radio link control information extracting
unit 255 outputs the scheduled transmission to the radio link
controlling unit 257.
[0183] The unlicensed band controlling unit 205 includes the radio
link controlling unit 257, a system information managing and
storing unit 258, and a upper layer processing unit 259.
[0184] The radio link controlling unit 257 receives a request for
the control information used for establishing a radio link such as
a dedicated preamble from the radio link control information
extracting unit 255. After that, the radio link controlling unit
257 outputs the control information used for establishing a radio
link to a radio link control information generating unit 260.
Further, the radio link controlling unit 257 obtains a system
information request from within the request for the control
information used for establishing a radio link. After that, the
radio link controlling unit 257 outputs the system request to a
system information generating unit 263 via the system information
managing and storing unit 258.
[0185] Further, when having determined that a radio link quality
measuring process that is not compliant with the measuring periodic
cycle is to be performed, the radio link controlling unit 257
notifies the radio link control information generating unit 260 of
the radio link quality measuring process. In that situation, the
radio link controlling unit 257 transmits conditions for measuring
the radio link quality to the radio link control information
generating unit 260.
[0186] In response to the request for the aperiodic radio link
quality measuring process, the radio link controlling unit 257
receives an input of a radio link quality measuring and calculating
result from the radio link control information extracting unit 255.
After that, on the basis of the obtained radio link quality, the
radio link controlling unit 257 selects a communication terminal to
which downlink data is to be transmitted. In the present example, a
situation will be explained in which the radio link controlling
unit 257 selects the communication terminal 3. After that, the
radio link controlling unit 257 selects a data volume, a radio
resource to be used, a modulation method to be used, an encoding
ratio, and/or the like that are to be applied when the downlink
data is transmitted to the communication terminal 3. Subsequently,
the radio link controlling unit 257 outputs the selection results
to the radio link control information generating unit 260.
[0187] Further, the radio link controlling unit 257 receives inputs
of pilot signals transmitted from communication terminals including
the communication terminal 3, from the radio link control
information extracting unit 255. After that, the radio link
controlling unit 257 measures and calculates uplink radio link
quality from the received pilot signals. Subsequently, on the basis
of the radio link quality, the radio link controlling unit 257
selects a communication terminal that is to perform an uplink data
transfer. In the present example, a situation will be explained in
which the radio link controlling unit 257 selects the communication
terminal 3 as a communication terminal that is to perform the
uplink data transfer, on the basis of the radio link quality.
[0188] Subsequently, the radio link controlling unit 257 selects a
data volume, a radio resource to be used, a modulation method to be
used, an encoding ratio, and/or the like that are to be applied
when the communication terminal 3 transmits the uplink data.
Subsequently, the radio link controlling unit 257 outputs the
selection results to the radio link control information generating
unit 260.
[0189] The upper layer processing unit 259 performs a controlling
process over the PDCP processing unit 201, the RLC processing unit
202, and the MAC processing unit 203.
[0190] The unlicensed band transmitting unit 241 includes the radio
link control information generating unit 260, a pilot generating
unit 261, a synchronization signal generating unit 262, the system
information generating unit 263, a transmission radio unit 265, and
an encoding and modulating unit 266.
[0191] The radio link control information generating unit 260
receives the notification about the radio link quality measuring
process that is not compliant with the measuring periodic cycle,
from the radio link controlling unit 257. In that situation, the
radio link control information generating unit 260 also obtains the
conditions for measuring the radio link quality, from the radio
link controlling unit 257. After that, the radio link control
information generating unit 260 generates a radio link measuring
request by using the conditions for measuring the radio link
quality. Subsequently, the radio link control information
generating unit 260 outputs the generated radio link measuring
request to the encoding and modulating unit 266 so as to transmit
the request to the communication terminal 3.
[0192] Further, the radio link control information generating unit
260 receives, from the radio link controlling unit 257, an input of
selection results regarding the data volume, the radio resource to
be used, the modulation method to be used, the encoding ratio,
and/or the like that are to be applied when the downlink data is
transmitted to the communication terminal 3. After that, the radio
link control information generating unit 260 generates downlink
control information including the selection results. Subsequently,
the radio link control information generating unit 260 outputs the
generated downlink control information including the selection
results to the encoding and modulating unit 266 so as to transmit
the downlink control information to the communication terminal
3.
[0193] Further, the radio link control information generating unit
260 receives, from the radio link controlling unit 257, an input of
selection results regarding the data volume, the radio resource to
be used, the modulation method to be used, the encoding ratio,
and/or the like that are to be applied when the communication
terminal 3 transmits the uplink data. After that, the radio link
control information generating unit 260 generates uplink control
information including the selection results. Subsequently, the
radio link control information generating unit 260 outputs the
generated uplink control information including the selection
results to the encoding and modulating unit 266 so as to transmit
the uplink control information to the communication terminal 3.
[0194] The system information managing and storing unit 258 stores
therein and manages the conditions for measuring the radio link
quality, the cell selection information, the neighboring cell
information, the MBSFN-related information, the network
identification information, the CA-related information, and/or the
like.
[0195] The system information generating unit 263 receives the
system information request from the radio link controlling unit 257
via the system information managing and storing unit 258. After
that, the system information generating unit 263 obtains
information such as the network identification information from the
system information managing and storing unit 258. Further, the
system information generating unit 263 generates system information
by using the obtained network identification information and the
like. Subsequently, the system information generating unit 263
outputs the generated system information including the network
identification information to the encoding and modulating unit 266
so as to transmit the system information to the base station 1.
[0196] Further, the system information generating unit 263 obtains
the conditions for measuring the radio link quality from the system
information managing and storing unit 258. After that, the system
information generating unit 263 generates the obtained measuring
conditions for measuring the radio link quality, into system
information. Subsequently, the system information generating unit
263 outputs the generated system information including the
measuring conditions for measuring the radio link quality to the
encoding and modulating unit 266 so as to transmit the system
information to the base station 1.
[0197] The synchronization signal generating unit 262 obtains the
cell IDs of peripheral cells of the communication terminal 3, from
the system information managing and storing unit 258. After that,
the synchronization signal generating unit 262 calculates a
synchronization signal (a synchronization signal sequence).
Subsequently, the synchronization signal generating unit 262
outputs the generated synchronization signal to the encoding and
modulating unit 266, so as to transmit the synchronization signal
to the communication terminal 3.
[0198] After the unlicensed band use notification is transmitted to
the communication terminal 3, the pilot generating unit 261
calculates a pilot signal (a pilot signal sequence). After that,
the pilot generating unit 261 outputs the generated pilot signal to
the encoding and modulating unit 266, so as to transmit the pilot
signal to the communication terminal 3.
[0199] It is noted, however, that the base station 2 using an
unlicensed band performs processes that are different from those
performed in a cell using a licensed band. The unlicensed band may
also be used by another system. Accordingly, when an unlicensed
band is used, i.e., when a transmission is performed by using a
frequency in an unlicensed band, it is checked to see whether the
frequency is not being used. More specifically, the radio link
controlling unit 257 receives, from the radio link quality
information extracting unit 254, an input of radio link quality
information of the signal received by the reception radio unit 251
on a frequency in the unlicensed band. After that, the radio link
controlling unit 257 judges whether or not such a radio signal that
is not noise and is significant is present in the signal received
on the frequency in the unlicensed band. For example, the radio
link controlling unit 257 determines that a significant radio
signal is present, i.e., the frequency is being used by another
party, when a Received Signal Strength Indicator (RSSI) obtained by
using an amplifier is equal to or larger than a threshold value or
when the output of a wave detector is equal to or larger than a
threshold value. In that situation, the radio link controlling unit
257 does not perform transmission using the frequency for a certain
period of time. The "significant radio signal" means that the
signal is not noise such as thermal noise.
[0200] When having determined that the unlicensed band is being
used by another party and that transmission is impossible, the
radio link controlling unit 257 further checks to see whether or
not another frequency in the unlicensed band is similarly being
used by another party. Alternatively, the radio link controlling
unit 257 may check to see whether or not the frequency is similarly
being used by another party when a predetermined period of time has
elapsed. The predetermined period of time may be regulated as
certain time intervals by law.
[0201] On the contrary, when having determined that the unlicensed
band is not being used by any other party, the radio link
controlling unit 257 instructs the synchronization signal
generating unit 262 and the pilot generating unit 261, via the
system information managing and storing unit 258, to transmit (to
broadcast) the synchronization signal and the pilot. The method of
confirming prior to transmission, in this manner, that no collision
will occur is called "Listen before Talk (LBT)" or "CSMA/CA".
[0202] The encoding and modulating unit 266 receives inputs of
various types of signals from the downlink signal processing unit
231, the radio link control information generating unit 260, the
pilot generating unit 261, the synchronization signal generating
unit 262, and the system information generating unit 263. The
encoding and modulating unit 266 performs an encoding process and a
modulating process on the input signals. Further, the encoding and
modulating unit 266 maps each of the input signals over a radio
frame, a slot, or a subframe. The encoding and modulating unit 266
outputs the mapped signals to the transmission radio unit 265.
[0203] The transmission radio unit 265 receives an input of each of
the signals mapped over a radio frame, a slot, or a subframe, from
the encoding and modulating unit 266. After that, the transmission
radio unit 265 converts the frequency of each of the mapped signals
into a radio frequency. Furthermore, the transmission radio unit
265 amplifies the mapped signals. Subsequently, the transmission
radio unit 265 transmits the mapped signals to the communication
terminal 3, via an antenna.
[0204] In the explanation above, the data transfer is controlled in
the same manner for both the PCell and the SCell. However, another
arrangement is also acceptable in which the user data is not
transferred in the PCell, whereas the user data is transferred only
in the SCell. Yet another arrangement is also acceptable in which
the system information is transferred only in the PCell, whereas
the system information is not transferred in the SCell.
[0205] Next, the communication terminal 3 will be explained with
reference to FIG. 9. FIG. 9 is a block diagram illustrating the
communication terminal. The communication terminal 3 includes a
receiving unit 31, a controlling unit 32, a transmitting unit 33,
and a baseband processing unit 34. Another arrangement is also
acceptable in which the system information is transferred only in
the PCell, whereas the system information is not transferred in the
SCell.
[0206] The receiving unit 31 includes a reception radio unit 301, a
demodulating and decoding unit 302, a system information extracting
unit 303, a radio link control information extracting unit 304, a
pilot extracting unit 305, a synchronization controlling unit 306,
and a synchronization signal extracting unit 307. Further, the
receiving unit 31 includes a cell ID extracting unit 308, a
terminal capability information request extracting unit 309, a
radio link quality measuring and calculating unit 310, a
synchronization signal generating unit 311, and a pilot calculating
unit 312.
[0207] The reception radio unit 301 receives signals sent from the
base stations 1 and 2 via an antenna. In this situation, the
reception radio unit 301 receives, from a terminal setting
controlling unit 321, an instruction about the frequency band to be
received. After that, the reception radio unit 301 amplifies the
received signal and further converts the signal at a radio
frequency into a baseband signal. After that, the reception radio
unit 301 outputs the signal converted into the baseband signal to
the demodulating and decoding unit 302.
[0208] The demodulating and decoding unit 302 receives an input of
the signal from the reception radio unit 301. After that, the
demodulating and decoding unit 302 performs a demodulating process
on the received signal. Further, the demodulating and decoding unit
302 performs a decoding process on the signal resulting from the
demodulating process. By using either predetermined modulating and
encoding schemes or methods corresponding to modulating and
encoding schemes instructed by the terminal setting controlling
unit 321, the demodulating and decoding unit 302 performs the
demodulating process and the decoding process. After that, the
demodulating and decoding unit 302 outputs the signal resulting
from the processes, to the baseband processing unit 34.
[0209] The system information extracting unit 303 extracts the
system information regularly transmitted from the base station 1 or
2, from the signal sent from the demodulating and decoding unit
302. After that, the system information extracting unit 303 stores
the extracted system information into a system information storing
unit 323. Further, the system information extracting unit 303
outputs the extracted system information to the terminal setting
controlling unit 321, a cell selection controlling unit 322, and a
radio link controlling unit 324.
[0210] The radio link control information extracting unit 304
extracts control information of Layer 1 (L1)/Layer 2(L2)
transmitted by the base station 1 or 2 while using PDCCH, from the
signal sent from the demodulating and decoding unit 302. The
control information includes information indicating an allocation
of uplink (UL) radio resources and the modulating and encoding
schemes that are applied. Also, the control information includes an
unlicensed band use notification. Further, the radio link control
information extracting unit 304 outputs the extracted control
information to the radio link controlling unit 324.
[0211] Further, the radio link control information extracting unit
304 extracts the radio link quality measuring request from the
signal sent from the demodulating and decoding unit 302. After
that, the radio link control information extracting unit 304
outputs the extracted radio link quality measuring request to the
radio link controlling unit 324.
[0212] Further, the radio link control information extracting unit
304 extracts a radio link control request transmitted from the base
station 1 or 2, from the signal sent from the demodulating and
decoding unit 302. After that, the radio link control information
extracting unit 304 outputs the radio link control request to the
radio link quality measuring and calculating unit 310 and the radio
link controlling unit 324.
[0213] On the basis of the timing of the radio frame or the slot
detected by the synchronization controlling unit 306, The pilot
extracting unit 305 extracts the pilot signal from the signal sent
from the demodulating and decoding unit 302. After that, the pilot
extracting unit 305 outputs the extracted pilot signal to the
synchronization controlling unit 306 and the radio link quality
measuring and calculating unit 310. For example, when an LTE system
is used, the pilot signal is a Reference Signal (RS).
[0214] The synchronization signal extracting unit 307 extracts the
synchronization signals transmitted by the base station 1 as the
PSS and the SSS, from the signal sent from the demodulating and
decoding unit 302 for each of the CCs. After that, the
synchronization signal extracting unit 307 outputs the
synchronization signals to the cell ID extracting unit 308 and the
synchronization controlling unit 306.
[0215] The synchronization controlling unit 306 detects the timing
of the radio frame and the timing of the slot on the basis of the
synchronization signals extracted by the synchronization signal
extracting unit 307. After that, the synchronization controlling
unit 306 notifies the terminal setting controlling unit 321 and the
pilot extracting unit 305 of the detected timing of the radio frame
and the slot. Further, the synchronization controlling unit 306
feeds the detected timing of the radio frame and the slot back to
the synchronization signal extracting unit 307.
[0216] Further, the synchronization controlling unit 306 receives
an input of the pilot calculated by the pilot calculating unit 312.
After that, on the basis of the pilot signal extracted by the pilot
extracting unit 305 and the pilot calculated by the pilot
calculating unit 312, the synchronization controlling unit 306
performs a symbol synchronization process. The symbol
synchronization process is to realize synchronization by using the
timing at the head of symbols.
[0217] The cell ID extracting unit 308 receives an input of the
synchronization signals from the synchronization signal extracting
unit 307. Subsequently, the cell ID extracting unit 308 identifies
the cell ID from the PSS and the SSS used by the base station 1.
More specifically, on the basis of the two synchronization signals,
namely the PSS and the SSS transmitted from the base station 1, the
cell ID extracting unit 308 is able to derive the cell ID. After
that, the cell ID extracting unit 308 outputs the identified cell
ID to the synchronization signal generating unit 311, the pilot
calculating unit 312, and the cell selection controlling unit
322.
[0218] The synchronization signal generating unit 311 receives an
input of the cell ID from the cell ID extracting unit 308. Further,
the synchronization signal generating unit 311 generates a
synchronization signal on the basis of the obtained cell ID.
Subsequently, the synchronization signal generating unit 311
outputs the generated synchronization signal to the synchronization
controlling unit 306.
[0219] The pilot calculating unit 312 receives an input of the cell
ID from the cell ID extracting unit 308. After that, on the basis
of the obtained cell ID, the pilot calculating unit 312 calculates
a pilot. Further, the pilot calculating unit 312 outputs the
calculated pilot to the synchronization controlling unit 306 and
the radio link quality measuring and calculating unit 310.
[0220] Next, a synchronization process will be explained in detail.
In the following sections, an example in which the communication
terminal 3 synchronizes with the base station 1 will be explained.
For the radio link quality measuring process performed by the radio
link quality measuring and calculating unit 310, the
synchronization controlling unit 306 performs, in advance, a
synchronization process to synchronize with the base station 1
subject to the measuring process. The synchronization process is
performed for the purpose of discriminating the pilot signal from
other signals or identifying the pilot signal itself.
[0221] According to a synchronization method, the synchronization
controlling unit 306 identifies the head of the radio frame on the
basis of the synchronization signals transmitted from the base
station 1. This process may be referred to as a frame
synchronization process. Further, by using the synchronization
signals, the synchronization controlling unit 306 identifies the
head of the radio frame or the head of subframes or the head of
slots structuring the radio frame. The process of identifying the
head of the subframes or the head of the slots structuring the
radio frame may be referred to as a frame synchronization process
or a slot synchronization process.
[0222] According to a synchronization signal generating method that
is shared in advance between the base station 1 and the
communication terminal 3, the synchronization controlling unit 306
identifies a synchronization signal sequence by calculating a
correlation between the synchronization signal generated by the
synchronization signal generating unit 311 and the synchronization
signals received from the base station 1 and further finds the head
of the sequence. As a result, the synchronization controlling unit
306 calculates the head of the frames or the slots. In this
situation, the synchronization signal is usually structured with a
plurality of signals and is a signal sequence that is not
structured with one signal (one symbol) but is structured with a
plurality of symbols. For example, in an LTE system, the
communication terminal 3 is able to either calculate or identify
cell information by identifying the synchronization signal
sequence. In the present example, the synchronization signal
sequence includes a CCell ID and a Physical Cell Identification
(PCell-ID).
[0223] Further, the synchronization controlling unit 306 performs a
symbol synchronization process by using the pilot signal. In this
situation, the method for calculating the pilot signal sequence is
shared in advance between the base station 1 and the communication
terminal 3, similarly to the process of identifying the
synchronization signal. After that, the synchronization controlling
unit 306 performs a symbol synchronization process by making a
comparison and calculating a correlation between the pilot signal
received from the base station 1 and the pilot calculated by the
pilot calculating unit 312.
[0224] In an LTE system, the pilot calculating unit 312 is able to
calculate the pilot signal on the basis of the cell ID derived from
the synchronization signal by the cell ID extracting unit 308. It
is therefore possible to shorten the time period spent on the
symbol synchronization process. In other words, the time period
spent on the symbol synchronization process would become longer, if
the cell ID were not derived by receiving the synchronization
signal.
[0225] Further, when having received an instruction to execute the
synchronization process from the radio link quality measuring and
calculating unit 310, the pilot extracting unit 305, the
synchronization controlling unit 306, and the synchronization
signal extracting unit 307 perform the synchronization process by
receiving synchronization signals and pilot signals from peripheral
cells.
[0226] From the signal sent from the demodulating and decoding unit
302, the terminal capability information request extracting unit
309 extracts the terminal capability information request
transmitted from the base station 1. After that, the terminal
capability information request extracting unit 309 outputs the
extracted terminal capability information request to a terminal
capability information controlling unit 326.
[0227] The radio link quality measuring and calculating unit 310
receives an input of the pilot calculated by the pilot calculating
unit 312. Further, the radio link quality measuring and calculating
unit 310 receives an input of the pilot signal from the pilot
extracting unit 305. After that, by using the obtained pilot signal
and the pilot calculated by the pilot calculating unit 312, the
radio link quality measuring and calculating unit 310 measures the
radio link quality. In this situation, as the radio link quality,
the radio link quality measuring and calculating unit 310 measures,
for example, a pilot reception power level (RSRP), a pilot
reception quality level (RSRQ), radio link quality (channel
quality), and a Signal to Interference Ratio (SIR) and further
calculates the radio link quality from the measuring results. As an
index indicating the reception quality, for example, a radio link
quality index called a Channel Quality Indicator (CQI) or a Signal
to Interference and Noise Ratio (SINR) may be used. After that, the
radio link quality measuring and calculating unit 310 notifies a
radio link quality information generating unit 334 of the measuring
and calculating result of the radio link quality. Further, the
radio link quality measuring and calculating unit 310 feeds the
measuring and calculating result of the radio link quality back to
the pilot extracting unit 305.
[0228] Further, by using the pilot signal, the radio link quality
measuring and calculating unit 310 measures a reception power level
(a reception electric field strength). After that, the radio link
quality measuring and calculating unit 310 notifies the cell
selection controlling unit 322 of the measuring result.
[0229] In an LTE system, defined as pilot signals are: a
common-to-cell pilot signal that is common to a plurality of
terminals in the cell (called a Cell-specific Reference Signal
[CRS]) and an individual pilot signal assigned to each individual
terminal (called a Dedicated Reference Signal [DRS]). Further, in
an LTE system, a pilot signal used for measuring positions (called
a Positioning Reference Signal [PRS]) and a pilot used for
measuring radio link quality (radio link state information) (called
a Channel State Information Reference Signal [CSI RS]) are defined.
In this situation, the common pilot may be referred to as a common
reference signal, a cell-specific pilot, or a common pilot.
Further, the individual pilot may be referred to as a dedicated
pilot or a UE-specific RS. Further, the pilot used for measuring
positions may be referred to as a positioning pilot or a
positioning RS. Further, the pilot signal used for measuring the
radio link quality may be referred to as a channel state
information pilot.
[0230] The radio link quality measuring and calculating unit 310
may perform the measuring and calculating process by using any of
these pilot signals. In other words, the radio link quality
measuring and calculating unit 310 may measure and calculate the
radio link quality by using a known signal, i.e., a signal that is
determined in advance either between the base station 1 or 2 and
the communication terminal 3 or in the radio communication
system.
[0231] Regular pilot signals may be a signal used for the purpose
of demodulation or a signal used for the purpose of measuring radio
link quality. The signal used for the purpose of demodulation may
be referred to as an individual pilot signal. Further, the signal
used for the purpose of measuring radio link quality may be
referred to as a common pilot signal.
[0232] Either when the radio link control request is obtained from
the radio link control information extracting unit 304 or when a
periodic cycle to measure the radio link quality has arrived, the
radio link quality measuring and calculating unit 310 instructs the
synchronization controlling unit 306 and the synchronization signal
extracting unit 307 to perform the synchronization process, via the
pilot extracting unit 305.
[0233] The controlling unit 32 includes the terminal setting
controlling unit 321, the cell selection controlling unit 322, the
system information storing unit 323, the radio link controlling
unit 324, a terminal capability information storing unit 325, and
the terminal capability information controlling unit 326.
[0234] The terminal setting controlling unit 321 receives an input
of the system information from the system information extracting
unit 303. Further, the terminal setting controlling unit 321
exercises control as described below, on the basis of the system
information.
[0235] On the basis of the control information designated by the
radio link controlling unit 324, the terminal setting controlling
unit 321 judges the radio resource allocated to the communication
terminal 3, and also, judges the modulating and encoding schemes
being applied. After that, the terminal setting controlling unit
321 controls operations of the reception radio unit 301, the
demodulating and decoding unit 302, a transmission radio unit 331,
and an encoding and modulating unit 332.
[0236] Further, the terminal setting controlling unit 321 receives
the unlicensed band use notification from the radio link
controlling unit 324. After that, the terminal setting controlling
unit 321 determines that the communication terminal 3 is to use a
radio resource in an unlicensed band. After that, the terminal
setting controlling unit 321 configures a frequency setting
corresponding to the unlicensed band into the reception radio unit
301, the demodulating and decoding unit 302, the transmission radio
unit 331, and the encoding and modulating unit 332.
[0237] The cell selection controlling unit 322 receives an input of
the system information from the system information extracting unit
303. After that, the cell selection controlling unit 322 exercises
control as described below, on the basis of the system information.
In this situation, the cell selection controlling unit 322 may
obtain, prior to the selecting of a cell, the control information
indicating the measured bandwidth and the priority level for
selecting cells from the received system information, so as to use
the obtained pieces of information for the selecting of a cell.
[0238] The cell selection controlling unit 322 receives an input of
the measuring and calculating result of the radio link quality from
the radio link quality measuring and calculating unit 310. Further,
the cell selection controlling unit 322 receives an input of the
cell ID from the cell ID extracting unit 308. Further, the cell
selection controlling unit 322 obtains the control information of
the communication terminal 3 extracted by the radio link control
information extracting unit 304.
[0239] By using the measuring and calculating result of the radio
link quality, the cell IDs, and the control information of the
communication terminal 3 that were input thereto, the cell
selection controlling unit 322 identifies the cell ID of a cell
having the best radio link quality. More specifically, the cell
selection controlling unit 322 performs the cell selecting process
by using at least one selected from between the RSRP and the RSRQ
described above which were measured by the radio link quality
measuring and calculating unit 310. Further, the cell selection
controlling unit 322 outputs the cell ID of the selected cell to
the radio link controlling unit 324. In this situation, the cell
selection controlling unit 322 repeatedly performs the cell
selecting process until a cell satisfying cell selection conditions
is found. In the present embodiment, an example will be explained
in which the cell selection controlling unit 322 selects the cell
10 of the base station 1.
[0240] For example, in an LTE system, the cell selection
controlling unit 322 selects a base station having the best radio
link quality by using the RSRP and the RSRQ. The cell 10 to which a
link connection as the first link is made by the cell selection
controlling unit 322 will serve as a PCell. Subsequently, the
communication terminal 3 performs a standby process and a link
connecting process in the cell 10. In a W-CDMA system or an LTE
system, the standby process is called a "camp on" process. Further,
the radio communication system according to the present embodiment
performs a CA process, so that the cell selection controlling unit
322 selects and makes a connection as the second link, to the cell
20 which will serve as an SCell.
[0241] The radio link controlling unit 324 obtains the cell ID
extracted by the cell ID extracting unit 308. Further, the radio
link controlling unit 324 obtains the control information extracted
by the radio link control information extracting unit 304. Further,
the radio link controlling unit 324 receives an input of the cell
ID of the cell selected as a connection destination, from the cell
selection controlling unit 322. Further, the radio link controlling
unit 324 receives an input of the system information from the
system information extracting unit 303. After that, the radio link
controlling unit 324 exercises control as described below, on the
basis of the system information.
[0242] For example, the radio link controlling unit 324 receives an
input of the cell ID from the radio link control information
extracting unit 304. After that, the radio link controlling unit
324 judges whether or not the cell ID provided in the notification
issued by the base station 1 or 2 is the same as the calculated
cell ID. When the two cell IDs are the same as each other, the
radio link controlling unit 324 stores information about the cell
into the system information storing unit 323.
[0243] After that, when a connection is to be made to a licensed
band, the radio link controlling unit 324 instructs the radio link
quality information generating unit 334 to generate radio link
quality information.
[0244] In contrast, when a connection is to be made to an
unlicensed band, the radio link controlling unit 324 obtains, from
the system information extracting unit 303, the system information
broadcast from the cell 20 having the cell ID obtained from the
radio link control information extracting unit 304. After that, the
radio link controlling unit 324 compares network identification
information received from the cell 10 with network identification
information received from the cell 20. When the network
identification information from the cell 10 is not the same as the
network identification information from the cell 20, the radio link
controlling unit 324 notifies the radio link quality measuring and
calculating unit 310 that radio link quality of a cell in another
unlicensed band is to be measured.
[0245] On the contrary, when the network identification information
from the cell 10 is the same as the network identification
information from the cell 20, the radio link controlling unit 324
instructs the radio link quality information generating unit 334 to
generate radio link quality information.
[0246] Further, as the control information extracted by the radio
link control information extracting unit 304, the radio link
controlling unit 324 obtains the control information related to
random access. After that, when data to be transmitted has accrued
during a standby in the cell 10 (i.e., when a call is to be made),
the radio link controlling unit 324 controls implementation of the
random access on the basis of the control information related to
the random access. More specifically, the radio link controlling
unit 324 selects a random access preamble from among a plurality of
preambles determined in advance. After that, the radio link
controlling unit 324 transmits the selected random access preamble
to the base station 1.
[0247] Subsequently, as the control information extracted by the
radio link control information extracting unit 304, the radio link
controlling unit 324 obtains a random access response. After that,
the radio link controlling unit 324 exercises control to transmit a
scheduled transmission according to the random access response.
Subsequently, the radio link controlling unit 324 instructs a radio
link control information generating unit 333 to generate the
scheduled transmission.
[0248] Further, when having received, from the radio link control
information extracting unit 304, control information used for
establishing a radio link, such as the dedicated preamble
transmitted from the cell 10 and the control information used for
the random access, the radio link controlling unit 324 exercises
control as described below. The radio link controlling unit 324
implements random access with the cell 10 or 20 from which a
control signal was transmitted, by using the dedicated preamble.
When the dedicated preamble is used, because there is no
possibility that another communication terminal may use the
preamble at the same time, no preamble collision will occur. For
this reason, the radio link controlling unit 324 performs a
"non-contention based random access procedure", which is different
from the "contention based random access procedure" that is
performed when the communication terminal 3 selects the preamble as
described above. In this situation, a message notifying the
terminal of the dedicated preamble transmitted from the cell 10
serves as message 0 and is called a "random access preamble
assignment".
[0249] The radio link controlling unit 324 instructs the radio link
control information generating unit 333 to transmit a random access
preamble to the cell 20 by using a dedicated preamble.
[0250] The terminal capability information storing unit 325 stores
therein information indicating whether or not the communication
terminal 3 is capable of using an unlicensed band.
[0251] The system information storing unit 323 receives an input of
the system information transmitted from the base station 1, from
the system information extracting unit 303. After that, the system
information storing unit 323 stores the obtained system information
therein.
[0252] The terminal capability information controlling unit 326
obtains the terminal capability information request extracted by
the terminal capability information request extracting unit 309.
After that, the terminal capability information controlling unit
326 obtains the information indicating whether or not the
communication terminal 3 is capable of using an unlicensed band,
from the terminal capability information storing unit 325.
Subsequently, the terminal capability information controlling unit
326 instructs a terminal capability information generating unit 335
to transmit the terminal capability information to the base station
1, together with the information indicating whether or not the
communication terminal 3 is capable of using an unlicensed
band.
[0253] The transmitting unit 33 includes the transmission radio
unit 331, the encoding and modulating unit 332, the radio link
control information generating unit 333, the radio link quality
information generating unit 334, and the terminal capability
information generating unit 335. The transmitting unit 33 and the
receiving unit 31 correspond to examples of the "second
communicating unit".
[0254] The radio link control information generating unit 333
receives information indicating generation of the scheduled
transmission from the radio link controlling unit 324. After that,
the radio link control information generating unit 333 generates
the scheduled transmission according to the control exercised by
the radio link controlling unit 324. Subsequently, the radio link
control information generating unit 333 outputs the scheduled
transmission to the encoding and modulating unit 332 so as to
transmit the scheduled transmission to the base station 1.
[0255] Further, when the cell 20 is to be connected, the radio link
control information generating unit 333 receives the instruction
from the radio link controlling unit 324 instructing that the
random access preamble be transmitted by using the dedicated
preamble. After that, the radio link control information generating
unit 333 transmits the random access preamble to the cell 20 by
using the dedicated preamble. In this situation, the contents of
the random access preamble may only be the dedicated preamble.
[0256] The radio link quality information generating unit 334
receives an input of the measuring result of the radio link quality
from the radio link quality measuring and calculating unit 310.
Subsequently, the radio link quality information generating unit
334 generates control information (a measuring report) indicating
reception quality from the measuring result of the radio link
quality. As the measuring report, for example, a Channel Quality
Indication (CQI) expressing the reception quality by using a
discrete value may be used.
[0257] The terminal capability information generating unit 335
receives the instruction from the terminal capability information
controlling unit 326 instructing that the terminal capability
information be transmitted to the base station 1, together with the
unlicensed band use capability/incapability information. After
that, the terminal capability information generating unit 335
generates terminal capability information including the unlicensed
band use capability/incapability information, according to the
instruction. After that, the terminal capability information
generating unit 335 outputs the generated terminal capability
information to the encoding and modulating unit 332 so as to
transmit the terminal capability information to the base station
1.
[0258] The encoding and modulating unit 332 receives inputs of
signals from the baseband processing unit 34, the radio link
control information generating unit 333, the radio link quality
information generating unit 334, and the terminal capability
information generating unit 335. After that, the encoding and
modulating unit 332 encodes each of the received signals. Further,
the encoding and modulating unit 332 performs a modulating process
on each of the encoded signals. The encoding and modulating unit
332 performs the encoding process and the modulating process by
using either predetermined modulating and encoding schemes or
methods corresponding to modulating and encoding schemes instructed
by the terminal setting controlling unit 321. After that, the
encoding and modulating unit 332 outputs the signals resulting from
the processes, to the transmission radio unit 331.
[0259] The transmission radio unit 331 receives an input of each of
the signals processed by the encoding and modulating unit 332.
Further, the transmission radio unit 331 receives an instruction
about the frequency band used for transmission from the terminal
setting controlling unit 321. After that, the transmission radio
unit 331 amplifies the signal and further converts the baseband
signal into a signal on a radio frequency. After that, the
transmission radio unit 331 transmits the signal converted onto the
radio frequency to the base stations 1 and 2 via an antenna.
[0260] The baseband processing unit 34 receives an input of the
baseband signal from the demodulating and decoding unit 302. After
that, the baseband processing unit 34 processes the signal in
accordance with the processing designated in the received signal.
For example, the baseband processing unit 34 stores the data into a
storing location designated in the received signal. In another
example, the baseband processing unit 34 converts the signal into
audio and outputs the audio through a speaker.
[0261] When transmitting the signal, the baseband processing unit
34 obtains data according to an instruction input from an operator.
For example, the baseband processing unit 34 reads the data from a
memory. After that, the baseband processing unit 34 outputs a
signal containing the obtained data to the encoding and modulating
unit 332. In another example, the baseband processing unit 34
receives an input of audio from a microphone, converts the audio
into a signal, and outputs the signal to the encoding and
modulating unit 332.
[0262] Next, a flow in the synchronization process and the radio
link quality measuring process will be explained with reference to
FIG. 10. FIG. 10 is a sequence chart of the synchronization process
and the radio link quality measuring process. In the following
sections, an example will be explained in which the communication
terminal 3 connects to the cell 10 of the base station 1.
[0263] The synchronization signal generating unit 162 of the base
station 1 transmits a PSS and an SSS serving as synchronization
signals, to the communication terminal 3 (step S1).
[0264] The synchronization controlling unit 306 included in the
communication terminal 3 performs a frame synchronization process
by using the PSS and the SSS extracted by the synchronization
signal extracting unit 307 (step S2).
[0265] Subsequently, the cell ID extracting unit 308 included in
the communication terminal 3 extracts a cell ID by using the PSS
and the SSS (step S3).
[0266] Subsequently, the pilot calculating unit 312 included in the
communication terminal 3 calculates a pilot signal on the basis of
the cell ID (step S4).
[0267] The pilot generating unit 161 included in the base station 1
generates a pilot signal and transmits the generated pilot signal
to the communication terminal 3 (step S5).
[0268] The synchronization controlling unit 306 included in the
communication terminal 3 performs a symbol synchronization process
by using the pilot signal extracted by the pilot extracting unit
305 (step S6).
[0269] Subsequently, the radio link quality measuring and
calculating unit 310 included in the communication terminal 3
measures and calculates radio link quality by using the radio link
control information extracted by the radio link control information
extracting unit 304 (step S7).
[0270] Subsequently, the cell selection controlling unit 322
included in the communication terminal 3 selects a cell to be
connected, by using the radio link quality measured and calculated
by the radio link quality measuring and calculating unit 310 (step
S8).
[0271] Next, a flow in random access procedures will be explained
with reference to FIGS. 11A and 11B. FIG. 11A is a sequence chart
of a contention based random access procedure. FIG. 11B is a
sequence chart of a non-contention based random access procedure.
In the following sections, the flow will be explained while using
the communication terminal 3 and the base stations 1 and 2 as the
subjects of the operation. In actuality, however, the functional
units described above perform the operation.
[0272] When performing the contention based random access
procedure, the communication terminal 3 transmits a random access
preamble to the base station 1 (step S11).
[0273] When having received the random access preamble, the base
station 1 transmits a random access response to the communication
terminal 3 (step S12).
[0274] When having received the random access response, the
communication terminal 3 transmits a scheduled transmission to the
base station 1 (step S13).
[0275] When having received the scheduled transmission, the base
station 1 returns a contention resolution to the communication
terminal 3 (step S14). As a result, a connection has been
established between the communication terminal 3 and the base
station 1.
[0276] In contrast, when performing a non-contention based random
access procedure, the base station 2 transmits a random access
assignment to the communication terminal 3 (step S21).
[0277] When having received the random access assignment, the
communication terminal 3 transmits a random access preamble to the
base station 2 (step S22).
[0278] When having received the random access preamble, the base
station 2 transmits a random access response to the communication
terminal 3 (step S23). As a result, a connection has been
established between the communication terminal 3 and the base
station 2.
[0279] Next, a flow in an SCell connection in the radio
communication system according to the present embodiment will be
explained, with reference to FIG. 12. FIG. 12 is a sequence chart
of the SCell connection in the radio communication system according
to the first embodiment.
[0280] The terminal capability information request generating unit
164 included in the base station 1 transmits a terminal capability
information request to the communication terminal 3 (step
S101).
[0281] The terminal capability information controlling unit 326
included in the communication terminal 3 receives the terminal
capability information request extracted by the terminal capability
information request extracting unit 309 and obtains the information
indicating whether or not the communication terminal 3 is capable
of using an unlicensed band, from the terminal capability
information storing unit 325. After that, the terminal capability
information generating unit 335 generates terminal capability
information including the unlicensed band use
capability/incapability information provided in the notification
issued by the terminal capability information controlling unit 326.
Subsequently, the terminal capability information generating unit
335 notifies the base station 1 of the unlicensed band use
capability/incapability by transmitting the generated terminal
capability information to the base station 1 (step S102). In the
following sections, an example will be explained in which the
communication terminal 3 is capable of using an unlicensed
band.
[0282] The radio link controlling unit 157 included in the base
station 1 receives the unlicensed band use capability/incapability
information from the terminal capability information controlling
unit 156. After that, the radio link controlling unit 157
identifies the terminal category of the communication terminal 3 on
the basis of the unlicensed band use capability/incapability
information (step S103).
[0283] Having received an instruction from the radio link
controlling unit 157, the radio link control information generating
unit 160 included in the base station 1 notifies the communication
terminal 3 of the terminal category of the communication terminal 3
(step S104).
[0284] Further, the radio link controlling unit 157 included in the
base station 1 exercises unlicensed band use control including a
process of judging whether or not an unlicensed band is to be used
and a process of generating a request to measure the radio link
quality of the unlicensed band (step S105). After that, the radio
link controlling unit 157 instructs the radio link control
information generating unit 160 to notify the communication
terminal 3 that an unlicensed band is to be used.
[0285] When having received the instruction from the radio link
controlling unit 157, the radio link control information generating
unit 160 included in the base station 1 generates control
information used for issuing a notification that an unlicensed band
is to be used. After that, the radio link control information
generating unit 160 notifies the communication terminal 3 that an
unlicensed band is to be used, by transmitting the generated
control information to the communication terminal 3 (step
S106).
[0286] The pilot generating unit 261 of the base station 2
calculates and generates a pilot signal. After that, the pilot
generating unit 261 transmits the pilot signal to the communication
terminal 3 (step S107).
[0287] By using the pilot signal transmitted from the base station
2, the radio link quality measuring and calculating unit 310
included in the communication terminal 3 measures and calculates
the radio link quality to and from the base station 2 (step S108).
After that, the radio link quality measuring and calculating unit
310 outputs the measuring and calculating result of the radio link
quality to the radio link quality information generating unit
334.
[0288] The radio link quality information generating unit 334
generates radio link quality information by using the received
measuring and calculating result of the radio link quality. After
that, the radio link quality information generating unit 334
transmits the generated radio link quality information to the base
station 1 (step S109).
[0289] The radio link controlling unit 157 included in the base
station 1 obtains the radio link quality information between the
communication terminal 3 and the base station 2, from the radio
link quality information extracting unit 154. Also, the radio link
controlling unit 157 similarly obtains radio link quality
information from other peripheral base stations of the
communication terminal 3 using an unlicensed band. After that, the
radio link controlling unit 157 selects a cell on the basis of the
obtained radio link quality information (step S110). In the
following sections, an example will be explained in which the radio
link controlling unit 157 has selected the base station 2.
[0290] When the radio link controlling unit 157 has selected the
base station 2, it means that a random access procedure is
performed among the base stations 1 and 2 and the communication
terminal 3, and a radio link is established to connect the
communication terminal 3 and the base station 2 to each other (step
S111).
[0291] Subsequently, the base station 2 and the communication
terminal 3 transmit and receive user data and control information
by using the established radio link (step S112).
[0292] Next, a flow in a CA process performed in the radio
communication system according to the present embodiment will be
explained, with reference to FIG. 13. FIG. 13 is a sequence chart
illustrating a schematic configuration of the CA process performed
in the radio communication system according to the first
embodiment. To illustrate the schematic configuration of the flow
in the entire CA process, detailed processes such as the
synchronization process and the category notifying process, for
example, are omitted from FIG. 13.
[0293] The pilot generating unit 161 included in the base station 1
generates a pilot signal and transmits the pilot signal to the
communication terminal 3 (step S201). Further, the pilot generating
unit 261 of the base station 2 generates a pilot signal and
transmits the pilot signal to the communication terminal 3 (step
S202).
[0294] The radio link quality measuring and calculating unit 310 of
the communication terminal 3 measures and calculates the radio link
quality to and from the base stations 1 and 2 by using the pilot
signals transmitted from the base stations 1 and (step S203). The
cell selection controlling unit 322 selects a cell by using the
measuring and calculating result of the radio link quality obtained
by the radio link quality measuring and calculating unit 310 (step
S204). In the present example, the cell selection controlling unit
322 selects the cell 10 as a PCell.
[0295] After that, the system information generating unit 163
included in the base station 1 transmits the system information to
the communication terminal 3 (step S205).
[0296] The base station 1 and the communication terminal 3 perform
a random access procedure and establish a radio link (step
S206).
[0297] Subsequently, the terminal capability information
controlling unit 326 of the communication terminal 3 obtains the
unlicensed band use capability/incapability information of the
communication terminal 3 from the terminal capability information
storing unit 325. After that, the terminal capability information
generating unit 335 generates terminal capability information
including the unlicensed band use capability/incapability
information provided in the notification issued by the terminal
capability information controlling unit 326. Subsequently, the
terminal capability information generating unit 335 notifies the
base station 1 of the unlicensed band use capability/incapability
by transmitting the generated terminal capability information to
the base station 1 (step S207). In the following sections, an
example will be explained in which the communication terminal 3 is
capable of using an unlicensed band.
[0298] The radio link controlling unit 157 included in the base
station 1 receives the notification about the unlicensed band use
capability/incapability. After that, the radio link controlling
unit 157 exercises unlicensed band use control including a process
of judging whether or not an unlicensed band is to be used and a
process of generating a request to measure the radio link quality
of the unlicensed band (step S208). After that, the radio link
controlling unit 157 instructs the radio link control information
generating unit 160 to notify the communication terminal 3 that an
unlicensed band is to be used.
[0299] Having received the instruction from the radio link
controlling unit 157, the radio link control information generating
unit 160 included in the base station 1 generates control
information used for issuing a notification that an unlicensed band
is to be used. After that, by transmitting the generated control
information to the communication terminal 3, the radio link control
information generating unit 160 notifies the communication terminal
3 that an unlicensed band is to be used (step S209).
[0300] Subsequently, the base station 1 and the communication
terminal 3 transmit and receive user data and control information
by using the established radio link (step S210).
[0301] Subsequently, the pilot generating unit 261 included in the
base station 2 generates a pilot signal and transmits the pilot
signal to the communication terminal 3 (step S211).
[0302] The base station 1 determines to add a cell on the basis of
the data volume and link quality to and from the communication
terminal 3 (step S212).
[0303] The radio link quality measuring and calculating unit 310
included in the communication terminal 3 measures and calculates
the radio link quality to and from the base station 2 by using the
pilot signal transmitted from the base station 2 (step S213). After
that, the radio link quality measuring and calculating unit 310
outputs the measuring and calculating result of the radio link
quality to the radio link quality information generating unit
334.
[0304] The radio link quality information generating unit 334
generates radio link quality information by using the received
measuring and calculating result of the radio link quality. After
that, the radio link quality information generating unit 334
transmits the generated radio link quality information to the base
station 1 (step S214).
[0305] The radio link controlling unit 157 obtains the radio link
quality information between the communication terminal 3 and the
base station 2 and the radio link quality information between the
communication terminal 3 and another base station extracted by the
radio link quality information extracting unit 154. After that, the
radio link controlling unit 157 selects the cell 20 of the base
station 2 as a cell to perform communication using an unlicensed
band (step S215). In the present example, the radio link
controlling unit 157 selects the cell 20 as an SCell.
[0306] After that, the, radio link controlling unit 157 instructs
the radio link control information generating unit 160 to transmit
a system information request to the base station 2. Having received
the instruction from the radio link controlling unit 157, the radio
link control information generating unit 160 generates control
information used for making a system information request. After
that, the radio link control information generating unit 160
transmits the system information request to the base station 2, by
transmitting the generated control information to the base station
2 (step S216).
[0307] The system information generating unit 263 included in the
base station 2 generates system information by using the
information stored in the system information managing and storing
unit 258. After that, the system information generating unit 263
transmits the generated system information to the base station 1
(step S217). The radio link controlling unit 157 included in the
base station 1 transmits the received system information of the
base station 2 to the communication terminal 3 via the radio link
control information generating unit 160 (step S218).
[0308] The base station 2 and the communication terminal 3 perform
a random access procedure and establish a radio link (step
S219).
[0309] Subsequently, the base station 1 and the communication
terminal 3 transmit and receive user data and control information
by using the radio link established between the base station 1 and
the communication terminal 3 (step S220). Further, the base station
2 and the communication terminal 3 transmit and receive user data
and control information by using the radio link established between
the base station 2 and the communication terminal 3 (step
S221).
[0310] Next, a flow in the CA process performed by the base station
1 according to the present embodiment will be explained, with
reference to FIG. 14. FIG. 14 is a flowchart illustrating the CA
process performed by the base station according to the first
embodiment.
[0311] The radio link controlling unit 157, the pilot generating
unit 161, the synchronization signal generating unit 162, and the
radio link control information generating unit 160 implement random
access with the communication terminal 3 (step S301). As a result,
a radio link is established between the base station 1 and the
communication terminal 3.
[0312] Subsequently, the system information generating unit 163
generates system information by using the information stored in the
system information managing and storing unit 158. After that, the
system information generating unit 163 transmits the generated
system information to the base station 1 (step S302).
[0313] Subsequently, the terminal capability information request
generating unit 164 generates a terminal capability information
request. After that, the terminal capability information request
generating unit 164 transmits the generated terminal capability
information request to the communication terminal 3 (step
S303).
[0314] Subsequently, the radio link controlling unit 157 receives,
from the terminal capability information controlling unit 156, the
unlicensed band use capability/incapability information included in
the terminal capability information received from the communication
terminal 3 (step S304). After that, the radio link controlling unit
157 judges the unlicensed band use capability/incapability (step
S305). Subsequently, the radio link controlling unit 157 instructs
the radio link control information generating unit 160 to notify
the communication terminal 3 that an unlicensed band is to be used.
The radio link control information generating unit 160 notifies the
communication terminal 3 that an unlicensed band is to be used
(step S306).
[0315] Having received the instruction from the radio link
controlling unit 157, the radio link control information generating
unit 160 generates a radio link quality measuring request to the
communication terminal 3 about the radio links between the
communication terminal 3 and peripheral base stations thereof
including the base station 2 each used for communication using an
unlicensed band. After that, the radio link control information
generating unit 160 transmits the generated radio link quality
measuring request to the communication terminal 3 (step S307).
[0316] Subsequently, the radio link controlling unit 157 receives
radio link quality measuring results from the peripheral base
stations of the communication terminal 3 including the base station
2 (step S308).
[0317] After that, the radio link controlling unit 157 selects an
additional cell on the basis of the received radio link quality
measuring results (step S309). In the following sections, an
example will be explained in which the radio link controlling unit
157 has selected the cell 20 of the base station 2.
[0318] Having received the instruction from the radio link
controlling unit 157, the radio link control information generating
unit 160 generates control information used for making a system
information request to the base station 2. After that, the radio
link control information generating unit 160 makes the system
information request to the base station 2, by transmitting the
generated control information to the base station 2 (step
S310).
[0319] The radio link controlling unit 157 obtains the system
information transmitted from the base station 2, from the radio
link control information extracting unit 155. After that, the radio
link controlling unit 157 transmits the obtained system information
of the base station 2 to the communication terminal 3 via the radio
link control information generating unit 160 (step S311).
[0320] Subsequently, the radio link controlling unit 157 instructs
the radio link control information generating unit 160 to transmit
a cell addition request to the communication terminal 3. The radio
link control information generating unit 160 generates control
information used for making the cell addition request. After that,
the radio link control information generating unit 160 transmits
the cell addition request to the communication terminal 3 by
transmitting the generated control information to the communication
terminal 3 (step S312).
[0321] Next, a flow in a CA process performed by the communication
terminal 3 according to the present embodiment will be explained,
with reference to FIG. 15. FIG. 15 is a flowchart illustrating the
CA process performed by the communication terminal according to the
first embodiment.
[0322] The cell selection controlling unit 322 performs a cell
selecting process to select a PCell by using pilot signals received
from the peripheral base stations including the base station 1
(step S321). In the present example, the cell selection controlling
unit 322 selects the cell 10 of the base station 1 as a PCell.
[0323] After that, the pilot extracting unit 305, the
synchronization controlling unit 306, the synchronization signal
extracting unit 307, the cell ID extracting unit 308, the terminal
setting controlling unit 321, and the radio link controlling unit
324 implement random access with the base station 1 (step S322). As
a result, a radio link is established between the communication
terminal 3 and the base station 1.
[0324] Subsequently, the radio link controlling unit 324 receives
the system information of the base station 1 extracted by the
system information extracting unit 303 (step S323).
[0325] Subsequently, the terminal capability information
controlling unit 326 receives a terminal capability information
request from the terminal capability information request extracting
unit 309 (step S324). The terminal capability information
controlling unit 326 obtains the information indicating whether or
not the communication terminal 3 is capable of using an unlicensed
band from the terminal capability information storing unit 325.
After that, the terminal capability information controlling unit
326 instructs the terminal capability information generating unit
335 to transmit terminal capability information including the
unlicensed band use capability/incapability information, to the
base station 1.
[0326] Having received the instruction from the terminal capability
information controlling unit 326, the terminal capability
information generating unit 335 generates the terminal capability
information including the unlicensed band use
capability/incapability information. After that, the terminal
capability information generating unit 335 notifies the base
station 1 of the unlicensed band use capability/incapability, by
transmitting the generated terminal capability information to the
base station 1 (step S325).
[0327] Subsequently, the radio link controlling unit 324 receives
the notification about using an unlicensed band transmitted from
the base station 1, from the radio link control information
extracting unit 304 (step S326).
[0328] After that, the radio link controlling unit 324 receives the
radio link quality measuring request transmitted from the base
station 1, from the radio link control information extracting unit
304 (step S327).
[0329] The pilot extracting unit 305, the synchronization
controlling unit 306, and the synchronization signal extracting
unit 307 perform a synchronization process with the base station
(step S328). Subsequently, the cell ID extracting unit 308 extracts
the cell ID of the base station 2 (step S329). After that, the
radio link quality measuring and calculating unit 310 measures and
calculates the radio link quality to and from the base station 2
(step S330).
[0330] Subsequently, the radio link quality measuring and
calculating unit 310 instructs the radio link quality information
generating unit 334 to notify the base station 1 of the radio link
quality. The radio link quality information generating unit 334
notifies the base station 1 of the measuring and calculating result
of the radio link quality, according to the instruction from the
radio link quality measuring and calculating unit 310 (step
S331).
[0331] The radio link controlling unit 324 judges whether or not a
cell addition request has been received from the base station 1
(step S332). When no cell addition request has been received (step
S332: No), the process returns to step S328.
[0332] On the contrary, when a cell addition request has been
received (step S332: Yes), the terminal setting controlling unit
321 receives the system information of the base station 2 from the
system information extracting unit 303 (step S333).
[0333] After that, the pilot extracting unit 305, the
synchronization controlling unit 306, the synchronization signal
extracting unit 307, the cell ID extracting unit 308, the terminal
setting controlling unit 321, and the radio link controlling unit
324 implement random access with the base station 2 (step S334). As
a result, a radio link is established between the communication
terminal 3 and the base station 2.
[0334] In the description above, the example is explained in which,
having received the terminal capability information request from
the base station 1, the communication terminal 3 sends the terminal
capability information including the unlicensed band use
capability/incapability information to the base station 1; however,
the timing of the sending is not limited to the timing in this
example. For instance, the communication terminal 3 may send pieces
of terminal capability information to the base station 1 in a
predetermined periodic cycle. In that situation, the base station 1
may wait for a piece of terminal capability information to be sent
from the communication terminal 3, without sending the terminal
capability information request to the communication terminal 3.
[0335] Further, in the description above, the example is explained
in which the base station 1 obtains the capability information of
the communication terminal 3, judges the unlicensed band use
capability/incapability, and transmits the notification about using
an unlicensed band and the system information of the base station 2
to the communication terminal 3; however, other configurations are
also possible. For instance, another arrangement is also acceptable
in which the base station 2 obtains the capability information of
the communication terminal 3, judges the unlicensed band use
capability/incapability, and transmits the notification about using
an unlicensed band and the system information of the base station 2
to the communication terminal 3. In that situation, it is desirable
to configure the base station 2 to have the same configuration as
that of the base station 1 according to the first embodiment. Also,
in that situation, the base station 1 may have the same
configuration as that of the base station in a second embodiment
described below.
[0336] <A Hardware Configuration>
[0337] Next, hardware configurations of the base stations 1 and 2
and the communication terminal 3 according to the present
embodiment will be explained. FIG. 16 is a hardware diagram of a
base station. For example, the base stations 1 and 2 each have the
hardware configuration illustrated in FIG. 16.
[0338] As illustrated in FIG. 16, each of the base stations 1 and 2
includes a Digital Signal Processor (DSP)/Central Processing Unit
(CPU) 91, a Large Scale Integration (LSI) 92, and a memory 93.
[0339] The DSP/CPU 91 includes an Interface (I/F) 911 and a
controlling unit 912. The I/F 911 is a communication interface for
the controlling unit 912 and a upper layer network.
[0340] When being included in the base station 1, the memory 93
stores therein various types of computer programs (hereinafter,
"programs") including programs that realize the functions of the
terminal capability information controlling unit 156, the radio
link controlling unit 157, the system information managing and
storing unit 158, and the upper layer processing unit 159
illustrated in FIG. 3. Further, the memory 93 realizes the
functions of the system information managing and storing unit
158.
[0341] Further, when being included in the base station 1, the
controlling unit 912 realizes the functions of the terminal
capability information controlling unit 156, the radio link
controlling unit 157, the system information managing and storing
unit 158, and the upper layer processing unit 159, by reading and
executing the various types of programs stored in the memory
93.
[0342] Further, when being included in the base station 2, the
memory 93 stores therein various types of programs including
programs that realize the functions of the radio link controlling
unit 257, the system information managing and storing unit 258, and
the upper layer processing unit 259 illustrated in FIG. 8. Further,
the memory 93 realizes the functions of the system information
managing and storing unit 258.
[0343] Further, when being included in the base station 2, the
controlling unit 912 realizes the functions of the radio link
controlling unit 257, the system information managing and storing
unit 258, and the upper layer processing unit 259, by reading and
executing the various types of programs stored in the memory
93.
[0344] The LSI 92 includes a reception radio circuit 921 and a
transmission radio circuit 922. When being included in the base
station 1, the reception radio circuit 921 realizes the functions
of the reception radio unit 151, the demodulating and decoding unit
152, the terminal capability information extracting unit 153, the
radio link quality information extracting unit 154, and the radio
link control information extracting unit 155 illustrated in FIG. 3.
Further, when being included in the base station 1, the
transmission radio circuit 922 realizes the functions of the
terminal capability information request generating unit 164, the
radio link control information generating unit 160, the pilot
generating unit 161, the synchronization signal generating unit
162, the system information generating unit 163, the transmission
radio unit 165, and the encoding and modulating unit 166.
[0345] Further, when being included in the base station 2, the
reception radio circuit 921 realizes the functions of the reception
radio unit 251, the demodulating and decoding unit 252, the radio
link quality information extracting unit 254, and the radio link
control information extracting unit 255 illustrated in FIG. 8.
Further, when being included in the base station 2, the
transmission radio circuit 922 realizes the functions of the radio
link control information generating unit 260, the pilot generating
unit 261, the synchronization signal generating unit 262, the
system information generating unit 263, the transmission radio unit
265, and the encoding and modulating unit 266.
[0346] FIG. 17 is a hardware diagram of the communication terminal.
The communication terminal 3 includes an LSI 94, a DSP 95, a memory
96, a display 97, a microphone 98, and a loudspeaker 99. The LSI 94
includes a reception radio circuit 941 and a transmission radio
circuit 942.
[0347] The display 97 is a display device such as a liquid crystal
screen. Further, the microphone 98 is a device to which the
operator inputs audio when performing audio communication or the
like. Further, the loudspeaker 99 is a device such as a speaker
that provides the operator with audio when performing audio
communication or the like.
[0348] The reception radio circuit 941 realizes the functions of
the reception radio unit 301, the demodulating and decoding unit
302, the system information extracting unit 303, the radio link
control information extracting unit 304, the pilot extracting unit
305, the synchronization controlling unit 306, the synchronization
signal extracting unit 307, and the cell ID extracting unit 308
illustrated in FIG. 9. Further, the reception radio circuit 941
realizes the functions of the terminal capability information
request extracting unit 309, the synchronization signal generating
unit 311, the pilot calculating unit 312, and the radio link
quality measuring and calculating unit 310 illustrated in FIG.
9.
[0349] The transmission radio circuit 942 includes the transmission
radio unit 331, the encoding and modulating unit 332, the radio
link control information generating unit 333, the radio link
quality information generating unit 334, and the terminal
capability information generating unit 335 illustrated in FIG.
9.
[0350] The memory 96 stores therein various types of programs
including programs that realizes the functions of the terminal
setting controlling unit 321, the cell selection controlling unit
322, the radio link controlling unit 324, and the terminal
capability information controlling unit 326. Further, the memory 96
realizes the functions of the system information storing unit 323
and the terminal capability information storing unit 325.
[0351] Further, the DSP 95 realizes the functions of the terminal
setting controlling unit 321, the cell selection controlling unit
322, the radio link controlling unit 324, and the terminal
capability information controlling unit 326 by reading and
executing the various types of programs from the memory 96.
Further, the DSP 95 realizes the functions of the baseband
processing unit 34. Further, although FIG. 17 illustrates the
configuration using the DSP 95, the configuration may be realized
by using a CPU.
[0352] As explained above, in the radio communication system
according to the present embodiment, the base station notifies the
communication terminal of the frequency of the unlicensed band as
the frequency to be used for the communication, so that the
communication terminal performs the communication using the
unlicensed band according to the provided information. With this
arrangement, it is possible to perform the communication while
ensuring that the unlicensed band is used. Further, it is possible
to implement the carrier aggregation process while using the
unlicensed band for the SCell. As a result, by using the unlicensed
band, the radio communication system according to the present
embodiment is able to increase the frequencies that are usable. It
is therefore possible to improve the transfer speeds.
[0353] Further, in the above description, the example is explained
in which the PCell and the SCell are connected to each other by
radio (in a wireless manner); however, the connecting method may be
another method. For example, the PCell and the SCell may be
connected to each other in a wired manner. In that situation,
between the PCell and the SCell, signals are transferred by using
an interface between the base stations, or signals are transferred
after converting radio signals to optical signals.
[0354] Further, the data transfer between the PCell and the SCell
is performed by using PDCP SDUs. In this regard, as a radio access
scheme, in the fields of LTE and LTE-Advanced, a femto using LTE
and LTE-Advanced is called an "HeNB". In contrast, in the fields
other than the fields of LTE and LTE-Advanced, the term "femto"
refers to communication using Wi-Fi, and not LTE. In Wi-Fi
communication, PDCP is not present, and only MAC is present of
which operations are different from those of the MAC in LTE and
LTE-Advanced. For this reason, it is difficult to transfer data in
units of PDCP SDUs. As a result, it is possible to divide data of
the same service into pieces and transmit the pieces of data from a
base station and from a femto.
Second Embodiment
[0355] Next, a second embodiment will be explained. A radio
communication system according to the second embodiment is
different from the first embodiment in that a communication
terminal transmits a terminal category to a base station. A base
station serving as a PCell in the present embodiment may also be
illustrated in FIG. 2. Further, a communication terminal according
to the present embodiment may also be illustrated in FIG. 9. In the
following sections, explanations of some of the functional units
having the same functions as those in the first embodiment will be
omitted.
[0356] The terminal capability information controlling unit 156
stores therein a list of terminal categories indicating a category
classification organized according to capabilities of communication
terminals as illustrated in FIG. 18A. FIG. 18A is a table
illustrating examples of the terminal categories. The "Maximum
number of DL-SCH transport block bits received within a TTI"
indicates the maximum number of bits that can be transmitted
through a downlink shared channel at a time. The "Maximum number of
bits of a DL-SCH transport block received within a TTI" indicates a
value of, for example, the maximum number of bits that can be
transferred at a time through a shared channel when MIMO is not
implemented. In another example, the value may be the maximum
number of bits that can be transferred at a time through a shared
channel, when two layers, i.e., 2.times.2 MIMO is implemented. In
yet another example, the value may be the maximum number of bits
that can be transferred at a time through a supply channel when
four layers, i.e., 4.times.4 MIMO is implemented. The "Total number
of soft channel bits" indicates the maximum number of bits when a
previously-received signal is combined with a newly-received
signal. The "Maximum number of supported layers for spatial
multiplexing in DL" indicates the number of streams in "spatial
multiplexing", i.e., MIMO. For example, when the "Maximum number of
supported layers for spatial multiplexing in DL" is four, the
transmission is performed in four streams (4.times.4 MIMO).
Further, indicated under the heading "Unlicensed band" is the
unlicensed band use capability/incapability. In other words, the
terminal categories stored in the terminal capability information
controlling unit 156 include categorization using the unlicensed
band use capability/incapability.
[0357] Further, the illustration in FIG. 18A is merely an example.
As long as an element used for judging the unlicensed band use
capability/incapability is included, the elements of the
categorization in FIG. 18A may include one or more other elements
and does not need to include any other elements. For example, FIG.
18B illustrates another example of terminal categories. In the
terminal categories illustrated in FIG. 18B, the terminals are
further categorized according to the unlicensed band use
capability/incapability depending on the frequency band being
used.
[0358] The terminal capability information controlling unit 156
obtains the terminal capability information of the communication
terminal 3 extracted by the terminal capability information
extracting unit 153. After that, the terminal capability
information controlling unit 156 obtains the terminal category to
which the communication terminal 3 belongs, on the basis of the
terminal capability information.
[0359] The terminal capability information controlling unit 156
judges whether or not the communication terminal 3 is capable of
using an unlicensed band on the basis of the obtained terminal
category. After that, the terminal capability information
controlling unit 156 notifies the radio link controlling unit 157
of whether or not the communication terminal 3 is capable of using
an unlicensed band. In this situation, in the present embodiment,
because the judging process is performed by using the terminal
categories illustrated in FIG. 18A, it is simply judged whether or
not the communication terminal 3 is capable of using an unlicensed
band. In contrast, for example, when the terminal categories
illustrated in FIG. 18B are used, the terminal capability
information controlling unit 156 judges whether or not the
communication terminal 3 is capable of using an unlicensed band,
depending on the frequency to be used in the unlicensed band.
[0360] The terminal capability information storing unit 325
included in the communication terminal 3 stores therein the
terminal category to which the communication terminal 3
belongs.
[0361] The terminal capability information controlling unit 326
obtains the terminal capability information request extracted by
the terminal capability information request extracting unit 309.
Further, the terminal capability information controlling unit 326
obtains the terminal category to which the device of its own
belongs, from the terminal capability information storing unit 325.
Subsequently, the terminal capability information controlling unit
326 transmits the obtained terminal category to the terminal
capability information generating unit 335, and also, instructs the
terminal capability information generating unit 335 to notify the
base station 1 of the terminal capability information.
[0362] The terminal capability information generating unit 335
obtains the terminal category of the device of its own from the
terminal capability information controlling unit 326. After that,
the terminal capability information generating unit 335 generates
terminal capability information including the terminal category.
After that, the terminal capability information generating unit 335
transmits the generated terminal capability information to the base
station 1 and notifies the base station 1 of the terminal category
of the device of its own.
[0363] Next, a flow in an SCell connection in a radio communication
system according to the present embodiment will be explained, with
reference to FIG. 19A. FIG. 19A is a sequence chart of the SCell
connection in the radio communication system according to the
second embodiment.
[0364] The terminal capability information request generating unit
164 included in the base station 1 transmits a terminal capability
information request to the communication terminal 3 (step
S401).
[0365] The terminal capability information controlling unit 326
included in the communication terminal 3 receives the terminal
capability information request extracted by the terminal capability
information request extracting unit 309 and obtains, from the
terminal capability information storing unit 325, the terminal
category of the communication terminal 3 of which the
categorization includes the unlicensed band use
capability/incapability (step S402). After that, the terminal
capability information generating unit 335 generates terminal
capability information including the terminal category provided in
the notification issued by the terminal capability information
controlling unit 326. Subsequently, the terminal capability
information generating unit 335 notifies the base station 1 of the
terminal category of the communication terminal 3 by transmitting
the generated terminal capability information to the base station 1
(step S403). In the following sections, an example will be
explained in which the communication terminal 3 is capable of using
an unlicensed band.
[0366] The radio link controlling unit 157 included in the base
station 1 receives the information about the terminal category of
the communication terminal 3 from the terminal capability
information controlling unit 156. After that, the radio link
controlling unit 157 checks to see whether or not the communication
terminal 3 is capable of using an unlicensed band, on the basis of
the terminal category of the communication terminal 3 (step
S404).
[0367] The radio link controlling unit 157 included in the base
station 1 exercises unlicensed band use control including a process
of judging whether or not an unlicensed band is to be used and a
process of generating a request to measure the radio link quality
of the unlicensed band (step S405). After that, the radio link
controlling unit 157 instructs the radio link control information
generating unit 160 to notify the communication terminal 3 that an
unlicensed band is to be used.
[0368] Having received the instruction from the radio link
controlling unit 157, the radio link control information generating
unit 160 included in the base station 1 generates control
information used for issuing the notification that an unlicensed
band is to be used. After that, the radio link control information
generating unit 160 notifies the communication terminal 3 that an
unlicensed band is to be used, by transmitting the generated
control information to the communication terminal 3 (step
S406).
[0369] The pilot generating unit 261 included in the base station 2
calculates and generates a pilot signal. After that, the pilot
generating unit 261 transmits the pilot signal to the communication
terminal 3 (step S407).
[0370] The radio link quality measuring and calculating unit 310
included in the communication terminal 3 measures and calculates
the radio link quality to and from the base station 2 by using the
pilot signal transmitted from the base station 2 (step S408). After
that, the radio link quality measuring and calculating unit 310
outputs the measuring and calculating result of the radio link
quality to the radio link quality information generating unit
334.
[0371] The radio link quality information generating unit 334
generates radio link quality information by using the received
measuring and calculating result of the radio link quality. After
that, the radio link quality information generating unit 334
transmits the generated radio link quality information to the base
station 1 (step S409).
[0372] The radio link controlling unit 157 included in the base
station 1 obtains the radio link quality information between the
communication terminal 3 and the base station 2 from the radio link
quality information extracting unit 154. Also, the radio link
controlling unit 157 similarly obtains radio link quality
information from other peripheral base stations of the
communication terminal using an unlicensed band. After that, the
radio link controlling unit 157 selects a cell on the basis of the
obtained radio link quality information (step S410). In the
following sections, an example will be explained in which the radio
link controlling unit 157 has selected the base station 2.
[0373] When the radio link controlling unit 157 has selected the
base station 2, a random access procedure is performed among the
base stations 1 and 2 and the communication terminal 3, and a radio
link is established to connect the communication terminal 3 and the
base station 2 to each other (step S411).
[0374] Subsequently, the base station 2 and the communication
terminal 3 transmit and receive user data and control information
by using the established radio link (step S412).
[0375] Next, the notification about the terminal category will be
explained in detail, with reference to FIG. 19B. FIG. 19B is a
sequence chart illustrating details of the terminal category
notifying process.
[0376] The terminal capability information request extracting unit
309 included in the communication terminal 3 extracts a terminal
capability information request from the signal transmitted from the
base station 1 (step S421). Subsequently, the terminal capability
information controlling unit 326 receives the terminal capability
information request extracted by the terminal capability
information request extracting unit 309. After that, having
received the terminal capability information request, the terminal
capability information controlling unit 326 obtains the terminal
category to which the communication terminal 3, which is the device
of its own, belongs, from the terminal capability information
storing unit 325 (step S422). The terminal category includes the
unlicensed band use capability/incapability.
[0377] Subsequently, the terminal capability information generating
unit 335 obtains the information about the terminal category from
the terminal capability information controlling unit 326. After
that, the terminal capability information generating unit 335
generates capability information including the terminal category
(step S423).
[0378] Subsequently, the terminal capability information generating
unit 335 transmits the capability information including the
terminal category to the base station 1 (step S424).
[0379] The terminal capability information extracting unit 153
included in the base station 1 extracts the terminal capability
information from the signal sent from the communication terminal 3.
Subsequently, the terminal capability information controlling unit
156 obtains the terminal capability information of the
communication terminal 3 from the terminal capability information
extracting unit 153. After that, from the terminal capability
information, the terminal capability information controlling unit
156 obtains the terminal category to which the communication
terminal 3 belongs (step S425).
[0380] Next, a flow in a CA process performed by the base station 1
according to the present embodiment will be explained, with
reference to FIG. 20. FIG. 20 is a flowchart illustrating the CA
process performed by the base station according to the second
embodiment.
[0381] The radio link controlling unit 157, the radio link control
information generating unit 160, the pilot generating unit 161, and
the synchronization signal generating unit 162 implement random
access with the communication terminal 3 (step S501). As a result a
radio link is established between the base station 1 and the
communication terminal 3.
[0382] Subsequently, the system information generating unit 163
generates system information by using the information stored in the
system information managing and storing unit 158. After that, the
system information generating unit 163 transmits the generated
system information to the base station 1 (step S502).
[0383] Subsequently, the terminal capability information request
generating unit 164 generates a terminal capability information
request including a terminal category transmission request. After
that, the terminal capability information request generating unit
164 requests that the terminal category be transmitted by
transmitting the generated terminal capability information request
to the communication terminal 3 (step S503).
[0384] Subsequently, the radio link controlling unit 157 receives
the information about the terminal category of the communication
terminal 3 included in the terminal capability information received
from the communication terminal 3, from the terminal capability
information controlling unit 156 (step S504). After that, the radio
link controlling unit 157 judges whether or not the communication
terminal 3 is capable of using an unlicensed band (step S505).
Subsequently, the radio link controlling unit 157 instructs the
radio link control information generating unit 160 to notify the
communication terminal 3 that an unlicensed band is to be used. The
radio link control information generating unit 160 notifies the
communication terminal 3 that an unlicensed band is to be used
(step S506).
[0385] Having received the instruction from the radio link
controlling unit 157, the radio link control information generating
unit 160 generates a radio link quality measuring request to the
communication terminal 3 about the radio links between the
communication terminal 3 and peripheral base stations thereof
including the base station 2 each used for communication using an
unlicensed band. After that, the radio link control information
generating unit 160 transmits the generated radio link quality
measuring request to the communication terminal 3 (step S507).
[0386] Subsequently, the radio link controlling unit 157 receives
the radio link quality measuring results from the peripheral base
stations of the communication terminal 3 including the base station
2 (step S508).
[0387] After that, the radio link controlling unit 157 selects an
additional cell on the basis of the received radio link quality
measuring results (step S509). In the following sections, an
example will be explained in which the radio link controlling unit
157 has selected the cell 20 of the base station 2.
[0388] Having received the instruction from the radio link
controlling unit 157, the radio link control information generating
unit 160 generates control information used for requesting the
system information from the base station 2. After that, the radio
link control information generating unit 160 requests the system
information from the base station 2 by transmitting the generated
control information to the base station 2 (step S510).
[0389] The radio link controlling unit 157 obtains the system
information transmitted from the base station 2, from the radio
link control information extracting unit 155. After that, the radio
link controlling unit 157 transmits the obtained system information
of the base station 2 to the communication terminal 3 via the radio
link control information generating unit 160 (step S511).
[0390] Subsequently, the radio link controlling unit 157 instructs
the radio link control information generating unit 160 to transmit
a cell addition request to the communication terminal 3. The radio
link control information generating unit 160 generates control
information for making the cell addition request. After that, the
radio link control information generating unit 160 transmits the
cell addition request to the communication terminal 3 by
transmitting the generated control information to the communication
terminal 3 (step S512).
[0391] Next, a flow in a CA process performed by the communication
terminal 3 according to the present embodiment will be explained
with reference to FIG. 21A. FIG. 21A is a flowchart illustrating
the CA process performed by the communication terminal according to
the second embodiment.
[0392] The cell selection controlling unit 322 performs a cell
selecting process to select a PCell by using pilot signals received
from the peripheral base stations including the base station 1
(step S521). In the present example, the cell selection controlling
unit 322 selects the cell 10 of the base station 1 as a PCell.
[0393] After that, the pilot extracting unit 305, the
synchronization controlling unit 306, the synchronization signal
extracting unit 307, the cell ID extracting unit 308, the terminal
setting controlling unit 321, and the radio link controlling unit
324 implement random access with the base station 1 (step S522). As
a result, a radio link is established between the communication
terminal 3 and the base station 1.
[0394] Subsequently, the radio link controlling unit 324 receives
the system information of the base station 1 extracted by the
system information extracting unit 303 (step S523).
[0395] Subsequently, the terminal capability information
controlling unit 326 receives a terminal capability information
request from the terminal capability information request extracting
unit 309 (step S524). The terminal capability information
controlling unit 326 obtains the information about the terminal
category of the communication terminal 3 from the terminal
capability information storing unit 325. After that, the terminal
capability information controlling unit 326 instructs the terminal
capability information generating unit 335 to transmit terminal
capability information including the information about the terminal
category, to the base station 1.
[0396] Having received the instruction from the terminal capability
information controlling unit 326, the terminal capability
information generating unit 335 generates terminal capability
information including the information about the terminal category.
After that, the terminal capability information generating unit 335
notifies the base station 1 of the terminal category, by
transmitting the generated terminal capability information to the
base station 1 (step S525).
[0397] Subsequently, the radio link controlling unit 324 receives
the notification about using an unlicensed band transmitted from
the base station 1, from the radio link control information
extracting unit 304 (step S526).
[0398] Subsequently, the radio link controlling unit 324 receives
the radio link quality measuring request transmitted from the base
station 1 from the radio link control information extracting unit
304 (step S527).
[0399] The pilot extracting unit 305, the synchronization
controlling unit 306, and the synchronization signal extracting
unit 307 perform a synchronization process with the base station
(step S528). Subsequently, the cell ID extracting unit 308 extracts
the cell ID of the base station 2 (step S529). After that, the
radio link quality measuring and calculating unit 310 measures and
calculates the radio link equality to and from the base station 2
(step S530).
[0400] Subsequently, the radio link quality measuring and
calculating unit 310 instructs the radio link quality information
generating unit 334 to notify the base station 1 of the radio link
quality. According to the instruction from the radio link quality
measuring and calculating unit 310, the radio link quality
information generating unit 334 notifies the base station 1 of the
measuring and calculating result of the radio link quality (step
S531).
[0401] The radio link controlling unit 324 judges whether or not a
cell addition request has been received from the base station 1
(step S532). When no cell addition request has been received (step
S532: No), the process returns to step S528.
[0402] On the contrary, when a cell addition request has been
received (step S532: Yes), the terminal setting controlling unit
321 receives the system information of the base station 2 from the
system information extracting unit 303 (step S533).
[0403] After that, the pilot extracting unit 305, the
synchronization controlling unit 306, the synchronization signal
extracting unit 307, the cell ID extracting unit 308, the terminal
setting controlling unit 321, and the radio link controlling unit
324 implement random access with the base station 2 (step S534). As
a result, a radio link is established between the communication
terminal 3 and the base station 2.
[0404] Next, the notification about the terminal category will be
explained in detail, with reference to FIG. 21B. FIG. 21B is a
flowchart illustrating details of the terminal category notifying
process.
[0405] The terminal capability information request extracting unit
309 included in the communication terminal 3 extracts the terminal
capability information request from the signal transmitted from the
base station 1. Subsequently, the terminal capability information
controlling unit 326 receives the terminal capability information
request extracted by the terminal capability information request
extracting unit 309 (step S541).
[0406] After that, having received the terminal capability
information request, the terminal capability information
controlling unit 326 obtains the terminal category to which the
communication terminal 3, which is the device of its own, belongs,
from the terminal capability information storing unit 325 (step
S542). The terminal category includes the unlicensed band use
capability/incapability information.
[0407] Subsequently, the terminal capability information generating
unit 335 obtains the information about the terminal category from
the terminal capability information controlling unit 326. After
that, the terminal capability information generating unit 335
generates capability information including the terminal category
(step S543).
[0408] Subsequently, the terminal capability information generating
unit 335 transmits the capability information including the
terminal category to the base station 1 (step S544).
[0409] The terminal capability information extracting unit 153
included in the base station 1 extracts the terminal capability
information from the signal sent from the communication terminal 3.
Subsequently, the terminal capability information controlling unit
156 obtains the terminal capability information of the
communication terminal 3 from the terminal capability information
extracting unit 153. After that, from the terminal capability
information, the terminal capability information controlling unit
156 obtains the terminal category to which the communication
terminal 3 belongs (step S545).
[0410] As explained above, in the radio communication system
according to the present embodiment, the communication terminal
notifies the base station of the terminal category thereof.
Subsequently, the base station notifies the communication terminal
of the frequency of the unlicensed band as the frequency to be used
in the communication. With this arrangement, it is possible to
perform the communication while ensuring that an unlicensed band is
used.
Third Embodiment
[0411] Next, a third embodiment will be explained. A radio
communication system according to the present embodiment is
different from those in the first and the second embodiments in
that a base station is separated into two devices, namely a
Centralized Base Band Unit (CBBU) and a Remote Radio Head (RRH).
FIG. 22 is a block diagram of the CBBU of the base station
according to the third embodiment. FIG. 23 is a block diagram of
the RRH of the base station according to the third embodiment. In
the following sections, explanations of some of the functional
units having the same functions as those in the first or the second
embodiment will be omitted.
[0412] A CBBU 11 included in the base station 1 according to the
present embodiment has an Electrical/Optical (E/O) converting unit
167, in the position of the reception radio unit 151 included in
the base station 1 according to the first embodiment. Further, the
CBBU 11 has an Optical/Electrical (O/E) converting unit 168, in the
position of the transmission radio unit 165 included in the base
station 1 according to the first embodiment.
[0413] The E/O converting unit 167 receives an optical signal sent
thereto from an RRH 12. After that, the E/O converting unit 167
converts the received optical signal to an electrical signal.
Subsequently, the E/O converting unit 167 outputs the electrical
signal resulting from the conversion, to the demodulating and
decoding unit 152.
[0414] The demodulating and decoding unit 152 performs a
demodulating process and a decoding process on the signal input
thereto from the E/O converting unit 167 and sends out the
result.
[0415] The encoding and modulating unit 166 performs an encoding
process and a modulating process on the received signal and outputs
the result to the O/E converting unit 168.
[0416] The O/E converting unit 168 converts the signal (the
electrical signal) input thereto from the encoding and modulating
unit 166 into an optical signal. After that, the O/E converting
unit 168 transmits the optical signal resulting from the conversion
to the RRH 12.
[0417] The RRH 12 includes an E/O converting unit 169 and an O/E
converting unit 170, in addition to the reception radio unit 151
and the transmission radio unit 165 included in the base station 1
according to the first embodiment.
[0418] The E/O converting unit 169 receives a signal from the
reception radio unit 151. After that, the E/O converting unit 169
converts the received signal (the electrical signal) into an
optical signal. Subsequently, the E/O converting unit 169 transmits
the optical signal resulting from the conversion to the CBBU
11.
[0419] The O/E converting unit 170 receives a signal from the CBBU
11. After that, the O/E converting unit 170 converts the received
signal (the optical signal) into an electrical signal.
Subsequently, the O/E converting unit 170 outputs the electrical
signal resulting from the conversion to the transmission radio unit
165.
[0420] As explained above, the base station according to the
present embodiment is separated into the CBBU and the RRH. In this
manner, even when the base station is separated into two units, the
base station is able to operate in the same manner as in the first
and the second embodiments. It is therefore possible to perform the
communication while ensuring that an unlicensed band is used.
Fourth Embodiment
[0421] Next, a fourth embodiment will be explained. A radio
communication system according to the present embodiment is
different from that in the first or the second embodiment in that
one base station has a PCell and an SCell. FIG. 24 is a block
diagram of a base station according to the fourth embodiment. In
the following sections, explanations of some of the functional
units having the same functions as those in the first or the second
embodiment will be omitted.
[0422] The base station 1 according to the present embodiment
includes, as illustrated in FIG. 24, the PDCP processing unit 101,
the RLC processing unit 102, the MAC processing unit 103, and the
physical layer processing unit 104. Further, the base station 1
includes the PDCP processing unit 201, the RLC processing unit 202,
the MAC processing unit 203, and the physical layer processing unit
204 that perform communication while using the cell 20, which is an
SCell.
[0423] The PDCP processing unit 101, the RLC processing unit 102,
the MAC processing unit 103, and the physical layer processing unit
104 perform communication while using the cell 10. In other words,
when the communication terminal 3 has selected the cell 10 as a
PCell, the PDCP processing unit 101, the RLC processing unit 102,
the MAC processing unit 103, and the physical layer processing unit
104 perform communication with the communication terminal 3 as the
PCell.
[0424] The PDCP processing unit 201, the RLC processing unit 202,
the MAC processing unit 203, and the physical layer processing unit
204 perform communication by using the cell 20 while using an
unlicensed band. In other words, when the communication terminal 3
has selected the cell 20 as an SCell, the PDCP processing unit 201,
the RLC processing unit 202, the MAC processing unit 203, and the
physical layer processing unit 204 perform communication with the
communication terminal 3 as the SCell.
[0425] As explained above, it is possible to provide within the one
base station (the base station 1), both the function of performing
communication by using the PCell and the function of performing
communication by using the SCell. In this situation also, the
physical layer processing units 104 and 204 have the same functions
as those in the first or the second embodiment. As a result, even
when the one base station has the PCell and the SCell as explained
in the present embodiment, it is possible to perform communication
while ensuring that an unlicensed band is used.
[0426] Further, even when the one base station has the PCell and
the SCell as explained in the present embodiment, it is also
possible to separate the base station into a CBBU and an RRH, as
explained in the third embodiment.
Fifth Embodiment
[0427] Next, a fifth embodiment will be explained. In the
embodiments described above, the example is explained in which, as
illustrated in FIG. 25, the base station 1 having the PCell and the
base station 2 having the SCell each have the processing units
corresponding to the layers. FIG. 25 is a schematic diagram
illustrating the processing units corresponding to the layers in
the base stations having the PCell and the SCell, respectively, and
a data transfer process. Further, the data transfer between the
base station 1 having the PCell and the base station 2 having the
SCell was explained above by using the example in which the PDCP
processing unit 101 and the PDCP processing unit 201 transfer data
therebetween by using the PDCP SDUs. However, the configurations of
the processing units corresponding to the layers and the data
transfer method are not limited to those explained above.
[0428] Further, it is also possible to vary the data transfer
positions. For example, as illustrated in FIG. 26A, it is also
possible to divide data in the upper layer apparatus 4 to the base
stations 1 and 2, by using a dividing function 41, for example.
FIG. 26A is a diagram illustrating a configuration in which data is
divided in the upper layer apparatus. In other words, the upper
layer apparatus 4 may include the dividing function 41 that divides
the data into pieces to be output in downlink transfer and that
concatenates together pieces of data received in uplink transfer,
for the base station 1 using a licensed band and for the base
station 2 using an unlicensed band. For example, when a
conventional HeNB (femto) is used as the base station 2, no data
transfer is performed between the base station 1 and the HeNB (the
femto). In other words, for example, the S-GW serving as the upper
layer apparatus 4 of the base stations 1 and 2 is different from
the S-GW of the HeNB. In that situation, it is desirable to use the
configuration illustrated in FIG. 26A.
[0429] Further, it is also possible to combine together two or more
functions selected from among the functions corresponding to the
layers in the base station 1 using a licensed band and the
functions corresponding to the layers in the base station 2 using
an unlicensed band.
[0430] For example, when PDCP is used in common, it is possible to
arrange the PDCP processing unit 101 to be used in common, as
illustrated in FIG. 26B. FIG. 26B is a diagram illustrating a
configuration in which the PDCP processing unit is used in common.
When the PDCP is used in common, the data transfer is performed
between the base station 1 and the base station 2, by using either
RLC SDUs (PDCP PDUs) or RLC PDUs (PDCP SDUs). In that situation,
the RLC processing units 102 and 202 each have a new RLC function
to which a data transfer function has newly been added.
[0431] Further, when PDCP and RLC are used in common, it is
possible to arrange the PDCP processing unit 101 and the RLC
processing unit 102 to be used in common, as illustrated in FIG.
26C. FIG. 26C is a diagram illustrating a configuration in which
the PDCP processing unit and the RLC processing unit are used in
common. When the PDCP and the RLC are used in common, the data
transfer between the base station functions is performed by using
either MAC SDUs (RLC PDUs) or MAC PDUs (RLC SDUs). In that
situation, the MAC processing units 103 and 203 each have a new MAC
function to which a data transfer function has newly been
added.
[0432] Further, when PDCP, RLC, and MAC are used in common, it is
possible to arrange the PDCP processing unit 101, the RLC
processing unit 102, and the MAC processing unit 103 to be used in
common, as illustrated in FIG. 26D. FIG. 26D is a diagram
illustrating a configuration in which the PDCP processing unit, the
RLC processing unit, and the MAC processing unit are used in
common. When PDCP, RLC, MAC are used in common, the data transfer
between the base station functions is performed by using MAC PDUs.
In that situation, the physical layer processing units 104 and 204
each have a new function to which a data transfer function has
newly been added.
[0433] In these situations, when any of the configurations
illustrated in FIGS. 26A to 26D is used, there is a high
possibility that it may be impossible to re-send the data at
conventional HARQ re-sending time intervals. Accordingly, it is
desirable to implement new MAC that is different from the
conventional MAC and that, in particular, exercises different HARQ
control. Further, because the frequency being used is different and
because Listen Before Talk (LBT) (CSMA/CA) is implemented, it is
desirable to use a new physical layer that is different from the
conventional physical layer.
[0434] Further, as illustrated in FIG. 27A, it is also possible to
transfer data from the PDCP processing unit 101 of the base station
1 using a licensed band to the RLC processing unit 202 of the base
station 2 using an unlicensed band. FIG. 27A is a diagram
illustrating a configuration in which data is transferred from the
PDCP processing unit of the base station using a licensed band to
the RLC processing unit of the base station using an unlicensed
band. In this situation, the RLC processing unit 202 has a new RLC
processing function that includes both the conventional PDCP
processing function and the conventional RLC processing
function.
[0435] Further, as illustrated in FIG. 27B, it is also possible to
transfer data from the PDCP processing unit 101 of the base station
1 using a licensed band to the MAC processing unit 203 of the base
station 2 using an unlicensed band. FIG. 27B is a diagram
illustrating a configuration in which data is transferred from the
PDCP processing unit of the base station using a licensed band to
the MAC processing unit of the base station using an unlicensed
band. In this situation, the RLC processing unit 202 and the MAC
processing unit 203 have a new RLC processing function and a new
MAC processing function, respectively, that include all of the
conventional PDCP processing functions, the conventional RLC
processing functions, and the conventional MAC processing
functions.
[0436] As explained above, by arranging a part of the functions of
the base station using the licensed band and the functions of the
base station using the unlicensed band to be used in common, it is
possible to arrange the single base station to have a part of the
functions of the base station using the licensed band and the
functions of the base station using the unlicensed band.
Consequently, it is possible to reduce the circuit scale of the
base station and to decrease electric power consumption. Further,
it is possible to make the base station compact. By making the base
station compact, it is possible to reduce the installation cost of
the base station.
[0437] Further, in the above description, the example is explained
in which the base station 1 using a licensed band and the base
station 2 using an unlicensed band are separate base stations.
However, it is also possible, as illustrated in FIGS. 28A to 28D,
to incorporate the function of performing communication by using an
unlicensed band into one of the base stations (the base station 1,
in the present example).
[0438] FIG. 28A is a diagram illustrating a configuration in which
data is divided in a upper layer apparatus within one base station.
FIG. 28B is a diagram illustrating a configuration in which a PDCP
processing unit is used in common within one base station. FIG. 28C
is a diagram illustrating a configuration in which a PDCP
processing unit and an RLC processing unit are used in common
within one base station. FIG. 28D is a diagram illustrating a
configuration in which a PDCP processing unit, an RLC processing
unit, and a MAC processing unit are used in common within one base
station.
[0439] Further, when the functions of the base station using a
licensed band and the functions of the base station using an
unlicensed band are configured into separate apparatuses, wiring
equipment such as an interface and an optical line to connect these
apparatuses to each other would be provided. In contract, when a
part of the functions of the base station using a licensed band and
the functions of the base station using an unlicensed band are
configured into one apparatus, there is no need to provide the
interface or the wiring equipment. It is therefore possible to
reduce the costs.
[0440] According to at least one aspect of the radio communication
system, the base station, the communication terminal, and the radio
communication system controlling method of the present disclosure,
an advantageous effect is achieved where it is possible to perform
communication while ensuring that an unlicensed band is used.
Further, because it is possible to perform communication while
ensuring that an unlicensed band is used, another advantageous
effect is achieved where it is possible to realize a high-speed
transfer. Further, it is possible to implement the carrier
aggregation process while using the unlicensed band for the SCell.
In addition, by using the unlicensed band, it is possible to
increase the frequencies that are usable. It is therefore possible
to improve the transfer speeds. Furthermore, it is possible to
divide data of mutually the same service into pieces of data and to
transmit the pieces of data from a base station and from a
femto.
[0441] All examples and conditional language provided herein are
intended for the pedagogical purposes of aiding the reader in
understanding the invention and the concepts contributed by the
inventors to further the art, and are not to be construed as
limitations to such specifically recited examples and conditions,
nor does the organization of such examples in the specification
relate to a showing of the superiority and inferiority of the
invention. Although one or more embodiments of the present
invention have been described in detail, it should be understood
that the various changes, substitutions, and alterations could be
made hereto without departing from the spirit and scope of the
invention.
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