U.S. patent application number 15/432603 was filed with the patent office on 2017-06-15 for base station apparatus, mobile terminal apparatus and communication control method.
This patent application is currently assigned to NTT DOCOMO, INC.. The applicant listed for this patent is NTT DOCOMO, INC.. Invention is credited to Tetsushi Abe, Sangiamwong Jaturong, Nobuhiko Miki, Satoshi Nagata.
Application Number | 20170171843 15/432603 |
Document ID | / |
Family ID | 44762943 |
Filed Date | 2017-06-15 |
United States Patent
Application |
20170171843 |
Kind Code |
A1 |
Abe; Tetsushi ; et
al. |
June 15, 2017 |
BASE STATION APPARATUS, MOBILE TERMINAL APPARATUS AND COMMUNICATION
CONTROL METHOD
Abstract
A base station apparatus capable of transmitting a downlink
transmission frame at transmission timing different from another
base station apparatus is provided. The base station apparatus
includes a blank resource setting section that sets, as a blank
resource, a resource corresponding to a downlink control channel
included in a downlink transmission frame transmitted from the
other base station apparatus, a user data assigning section that
assigns user data to the downlink transmission frame while avoiding
the blank resource, and a transmission section that transmits the
downlink transmission frame assigned the user data to a mobile
terminal apparatus.
Inventors: |
Abe; Tetsushi; (Tokyo,
JP) ; Nagata; Satoshi; (Tokyo, JP) ; Miki;
Nobuhiko; (Tokyo, JP) ; Jaturong; Sangiamwong;
(Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
NTT DOCOMO, INC. |
Tokyo |
|
JP |
|
|
Assignee: |
NTT DOCOMO, INC.
Tokyo
JP
|
Family ID: |
44762943 |
Appl. No.: |
15/432603 |
Filed: |
February 14, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14858730 |
Sep 18, 2015 |
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15432603 |
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13261460 |
Dec 19, 2012 |
9179466 |
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PCT/JP2011/058609 |
Apr 5, 2011 |
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14858730 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04W 88/08 20130101;
H04W 84/045 20130101; H04W 72/082 20130101; H04W 72/042 20130101;
H04W 72/1205 20130101; H04W 88/02 20130101; H04W 24/02 20130101;
H04W 16/16 20130101 |
International
Class: |
H04W 72/04 20060101
H04W072/04; H04W 72/12 20060101 H04W072/12 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 5, 2010 |
JP |
2010-087389 |
Claims
1. Abase station apparatus capable of transmitting a downlink
transmission frame at transmission timing different from another
base station apparatus, the base station apparatus comprising: a
blank resource setting section that sets, as a blank resource, a
resource corresponding to a downlink control channel included in a
downlink transmission frame transmitted from the other base station
apparatus; a user data assigning section that assigns user data to
the downlink transmission frame while avoiding the blank resource;
and a transmission section that transmits the downlink transmission
frame assigned the user data to a mobile terminal apparatus.
2. The base station apparatus according to claim 1, wherein the
blank resource setting section sets the blank resource based on a
shift amount of transmission timing of the downlink transmission
frame with respect to the downlink transmission frame of the other
base station apparatus.
3. The base station apparatus according to claim 2, wherein the
blank resource setting section sets the blank resource based on a
set position of a blank period acquired from the other base station
apparatus, in addition to the shift amount.
4. The base station apparatus according to claim 1, wherein the
blank resource setting section sets, as the blank resource, a
resource corresponding to the downlink control channel in a
subframe consisting of the downlink control channel and a blank
period in the downlink transmission frame transmitted from the
other base station apparatus.
5. A mobile terminal apparatus connected to a base station
apparatus capable of transmitting a downlink transmission frame at
transmission timing different from another base station apparatus,
the mobile terminal apparatus comprising: a blank resource
information acquiring section that acquires blank resource
information to identify a resource corresponding to a downlink
control channel included in a downlink transmission frame
transmitted from the other base station apparatus, as a blank
resource set in the base station apparatus; and a user data
demodulation section that demodulates user data received from the
base station apparatus while avoiding the blank resource, based on
the blank resource information.
6. The mobile terminal apparatus according to claim 5, wherein the
blank resource information is a shift amount of transmission timing
of the downlink transmission frame with respect to the downlink
transmission frame from the other base station apparatus.
7. A communication control method in a base station apparatus
capable of transmitting a downlink transmission frame at
transmission timing different from another base station apparatus,
the communication control method comprising: setting, as a blank
resource, a resource corresponding to a downlink control channel
included in a downlink transmission frame transmitted from the
other base station apparatus; assigning user data to the downlink
transmission frame while avoiding the blank resource; and
transmitting the downlink transmission frame assigned the user data
to a mobile terminal apparatus.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a continuation application of
and, thereby, claims benefit under 35 U.S.C. .sctn.120 to U.S.
patent application Ser. No. 14/858,730 filed on Sep. 18, 2015,
titled, "BASE STATION APPARATUS, MOBILE TERMINAL APPARATUS AND
COMMUNICATION CONTROL METHOD," which is a divisional application of
and, thereby, claims benefit under 35 U.S.C. .sctn.120 to U.S.
patent application Ser. No. 13/261,460 filed on Oct. 4, 2012,
titled, "BASE STATION APPARATUS, MOBILE TERMINAL APPARATUS AND
COMMUNICATION CONTROL METHOD," which is a national stage
application of PCT Application No. PCT/JP2011/058609, filed on Apr.
5, 2011, which claims priority to Japanese Patent Application No.
2010-087389 filed on Apr. 5, 2010. The contents of the priority
applications are incorporated by reference in their entirety.
TECHNICAL FIELD
[0002] The present invention relates to abase station apparatus,
mobile terminal apparatus and communication control method in the
next-generation mobile communication system.
BACKGROUND ART
[0003] In UMTS (Universal Mobile Telecommunications System)
networks, for the purpose of improving spectral usage efficiency
and further improving data rates, by adopting HSDPA (High Speed
Downlink Packet Access) and HSUPA (High Speed Uplink Packet
Access), it is performed exploiting maximum features of the system
based on W-CDMA (Wideband Code Division Multiple Access). For the
UMTS network, for the purpose of further increasing high-speed data
rates, providing low delay and the like, Long Term Evolution (LTE)
has been studied (Non-patent Literature 1). In LTE, as a
multiplexing scheme, OFDMA (Orthogonal Frequency Division Multiple
Access) different from W-CDMA is used in downlink, while SC-FDMA
(Single Carrier Frequency Division Multiple Access) is used in
uplink.
[0004] In the 3G system, a fixed band of 5 MHz is substantially
used, and it is possible to achieve transmission rates of
approximately maximum 2 Mbps in downlink. Meanwhile, in the LTE
system, using variable bands ranging from 1.4 MHz to 20 MHz, it is
possible to achieve transmission rates of maximum 300 Mbps in
downlink and about 75 Mbps in uplink. Further, in the UMTS network,
for the purpose of further increasing the wide-band and high speed,
successor systems to LTE have been studied (for example, LTE
Advanced (LTE-A)). In LTE-A (LTE Release 10), a Heterogeneous
network configuration is studied in which importance is attached to
a local area environment in addition to conventional cellular
environments.
CITATION LIST
Non-Patent Literature
[0005] Non-Patent Literature 1: 3GPP, TR25.912 (V7.1.0),
"Feasibility Study for Evolved UTRA and UTRAN", September 2006
SUMMARY OF THE INVENTION
Technical Problem
[0006] The present invention was made in view of such a respect,
and it is an object of the invention to provide a base station
apparatus, mobile terminal apparatus and communication control
method for enabling control adapted to interference inside a
Heterogeneous network to be performed to support the
next-generation mobile communication system.
Solution to Problem
[0007] A base station apparatus of the invention is a base station
apparatus which shares at least a part of a frequency band with
another base station apparatus that covers a large-scale cell,
covers a small-scale cell, and is capable of transmitting a
downlink transmission frame at transmission timing different from
the another base station apparatus, and is characterized by having
a blank resource setting section configured to set resources, in
which the downlink transmission frame undergoes interference from
another downlink transmission frame including a blank period
transmitted from the another base station apparatus, as blank
resources, a user data assigning section configured to assign user
data to the downlink transmission frame while avoiding the blank
resources, and a transmission section configured to transmit the
downlink transmission frame assigned the user data to a mobile
terminal apparatus.
[0008] A base station apparatus of the invention is a base station
apparatus which shares at least a part of a frequency band with
another base station apparatus that covers a small-scale cell,
covers a large-scale cell, and is capable of transmitting a
downlink transmission frame at transmission timing different from
the another base station apparatus, and is characterized by having
a blank resource setting section configured to set resources, in
which the downlink transmission frame interferes with a downlink
control channel of another downlink transmission frame transmitted
from the another base station apparatus, as blank resources, a user
data assigning section configured to assign user data to the
downlink transmission frame while avoiding the blank resources, and
a transmission section configured to transmit the downlink
transmission frame assigned the user data to a mobile terminal
apparatus.
[0009] Technical Advantages of the Invention
[0010] According to the invention, interference is suppressed which
is imposed on a downlink transmission frame transmitted from a base
station apparatus of a small-scale cell by a downlink transmission
frame transmitted from a base station apparatus of a large-scale
cell. Thus, it is possible to cause the base station apparatus of
the large-scale cell and the base station apparatus of the
small-scale to perform control adapted to interference inside a
Heterogeneous network having the large-scale cell and the
small-scale cell.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is an explanatory view of a system band of an LTE
system;
[0012] FIG. 2 is an explanatory view of the outline of a
Heterogeneous network;
[0013] FIG. 3 is an explanatory view of interference of radio
frames of a macro-cell and a pico-cell;
[0014] FIG. 4 is an explanatory view of an interference suppression
method for radio frames of the micro-cell and the pico-cell;
[0015] FIG. 5 is an explanatory view showing an example of
transmission control processing in a base station apparatus of the
pico-cell;
[0016] FIG. 6 is an explanatory view of transmission control
processing in a base station apparatus of the macro-cell;
[0017] FIG. 7 is an explanatory view of a configuration of a radio
communication system;
[0018] FIG. 8 is an explanatory view of the entire configuration of
the base station apparatus;
[0019] FIG. 9 is an explanatory view of the entire configuration of
a mobile terminal apparatus;
[0020] FIG. 10 is a conceptual diagram of a process of generating a
downlink transmission frame in the base station apparatus of the
pico-cell;
[0021] FIG. 11 is a conceptual diagram of a process of receiving
the downlink transmission frame in the mobile terminal apparatus
that communicates via the pico-cell;
[0022] FIG. 12 is a conceptual diagram of a process of generating a
downlink transmission frame in the base station apparatus of the
macro-cell; and
[0023] FIG. 13 is a conceptual diagram of a process of receiving
the downlink transmission frame in the mobile terminal apparatus
that communicates via the macro-cell.
DESCRIPTION OF EMBODIMENTS
[0024] FIG. 1 is a diagram to explain a frequency usage state when
mobile communications are performed in downlink. In addition, in
the following descriptions, a base frequency block is described as
a component carrier. The example as shown in FIG. 1 is of the
frequency usage state in the case of coexistence of LTE-A systems
that are first mobile communication systems having first relatively
wide system bands comprised of a plurality of component carriers,
and LTE systems that are second mobile communication systems having
a second relatively narrow system band (herein, comprised of a
single component carrier). In the LTE-A systems, for example, radio
communications are performed with a variable system bandwidth of
100 MHz or less, and in the LTE systems, radio communications are
performed with a variable system bandwidth of 20 MHz or less. The
system band of the LTE-A system is at least one base frequency
region (component carrier: CC) with a system band of the LTE system
as a unit. Thus integrating a plurality of base frequency regions
to broaden the band is referred to as carrier aggregation.
[0025] For example, in FIG. 1, the system band of the LTE-A system
is a system band (20 MHz.times.5=100 MHz) containing bands of five
component carriers where the system band (base band: 20 MHz) of the
LTE system is one component carrier. In FIG. 1, a mobile terminal
apparatus UE (User Equipment) #1 is a mobile terminal apparatus
supporting the LTE-A system (also supporting the LTE system), and
has the system band of 100 MHz, UE#2 is a mobile terminal apparatus
supporting the LTE-A system (also supporting the LTE system), and
has the system band of 40 MHz (20 MHz.times.2=40 MHz), and UE#3 is
a mobile terminal apparatus supporting the LTE system (not
supporting the LTE-A system), and has the system band of 20 MHz
(base band).
[0026] In addition, in the LTE-A system, a Heterogeneous network
(hereinafter, referred to as HetNet) configuration is studied in
which importance is attached to a local area environment. As shown
in FIG. 2, the HetNet is a hierarchical network for overlaying
various forms of cells of a pico-cell C1, femto-cell and the like
(small-scale cells) in addition to a conventional macro-cell C2
(large-scale cell). In the HetNet, a base station apparatus B2 of
the macro-cell C2 for covering a relatively large area is set for
downlink transmission power higher than a base station apparatus B1
of the pico-cell C1 for covering a relatively narrow area.
[0027] Accordingly, when the macro-cell C2 and the pico-cell C1 are
operated with close frequency bands, as shown in FIG. 3, there is a
problem that a radio frame from the base station apparatus B1 of
the pico-cell C1 undergoes large interference from a radio frame
from the base station apparatus B2 of the macro-cell C2. Therefore,
in the pico-cell C1, coverage is narrowed by large interference
from the macro-cell C2.
[0028] Further, particularly a downlink control channel (PDCCH:
Physical Downlink Control Channel) arranged at the beginning of a
subframe is basically not retransmitted as distinct from a downlink
data channel (PDSCH: Physical Downlink Shared Channel), and
therefore, is given a significant effect by interference from the
macro-cell C2. Furthermore, a broadcast channel (PBCH: Physical
Broadcast Channel) shown by B in the subframe and cell-search
synchronization signal (PSS: Primary Synchronization Signal, SSS:
Secondary Synchronization Signal) are also not basically
retransmitted, and therefore, are given a significant effect by
interference from the macro-cell C2.
[0029] To solve the problems, as shown in FIG. 4, considered is a
method of using an MBSFN (Multimedia Broadcast multicast service
Single Frequency Network) subframe and subframe shift. The MBSFN
frame is specified in the LTE system, and is a subframe for
enabling signals except a control channel to be a blank interval
(blank period). According to this configuration, overlap of
downlink control channels is canceled by radio frames of the
macro-cell C2 and the pico-cell C1 being shifted in the time-axis
direction. Further, the radio frame of the macro-cell C2 is
partially provided with the blank periods by the MBSFN subframes,
and suppresses interference to the downlink control channels,
broadcast channels and synchronization signals of the subframes
enclosed by dashed lines of the pico-cell C1. As a result, coverage
of the downlink control channel, broadcast channel and
synchronization signal of the pico-cell C1 is ensured. Further,
interference is also reduced to downlink data channels of the
subframes enclosed by dashed lines of the pico-cell C1 by the blank
periods of the radio frame of the macro-cell C2, and improvements
in the data rate are expected.
[0030] However, in the aforementioned method, although interference
to the downlink control channels is suppressed in the subframes of
the pico-cell C1 enclosed by dashed lines, there is a problem that
a part of user data undergoes interference from the radio frame of
the macro-cell C2. Further, control channels of subframes that are
not enclosed by dashed lines of the pico-cell C1 are affected by
interference of the radio frame of the macro-cell C2.
[0031] Therefore, to solve the problem, the inventors of the
invention arrived at the invention. In other words, it is the gist
of the invention that a base station apparatus of a pico-cell
assigns user data to a subframe while avoiding resources that
undergo interference from a macro-cell, and that a base station
apparatus of the macro-cell assigns user data to a subframe while
avoiding resources that interfere with a control channel of the
pico-cell.
[0032] An Embodiment of the invention will specifically be
described below with reference to accompanying drawings. Referring
to FIG. 5, described is suppression of interference to a downlink
radio frame of the pico-cell by transmission control in a base
station apparatus of the pico-cell. FIG. 5 is an explanatory view
showing an example of transmission control processing in the base
station apparatus of the pico-cell according to this Embodiment of
the invention.
[0033] As shown in FIG. 5, a downlink radio frame of the macro-cell
C2 is comprised of 10 subframes of subframes #0 to #9, and a
control channel (PDCCH) is multiplexed into OFDM symbols on the
beginning side of each subframe. Further, the downlink radio frame
of the macro-cell C2 has the above-mentioned MBSFN subframes, and
blank periods are set except control channels of subframes except
subframes #0, #4, #5 and #9. The broadcast channel (PBCH) and
synchronization signals (PSS, SSS) for cell search are multiplexed
into subframes #0 to #5.
[0034] Meanwhile, a downlink radio frame of the pico-cell C1 has
the same radio frame configuration as the downlink radio frame of
the macro-cell C2, but the subframe is not set for the blank
period. Further, the downlink radio frame of the pico-cell C1 is
subframe-shifted in the time-axis direction relatively to the radio
frame of the macro-cell C2. By this means, a part of control
channels, broadcast channels, synchronization signals and the like
in the downlink radio frame of the pico-cell C1 are coincident with
the blank periods of the downlink radio frame of the macro-cell C2,
and interference from the macro-cell C2 is suppressed. In the
downlink radio frame of the pico-cell C1, subframes with
interference to the control channel and the like suppressed are
used.
[0035] As described above, the blank periods of the downlink radio
frame of the macro-cell C2 are set except the downlink control
channels. Further, the subframe of the pico-cell C1 is shifted in
the time-axis direction with respect to the MBSFN subframe of the
macro-cell C2. Therefore, in the subframe of the pico-cell C1,
although interference to the control channel is suppressed by the
blank period of the MBSFN subframe of the macro-cell C2, the data
channel partially undergoes interference. For example, interference
to the control channel is suppressed in the subframe #6 of the
pico-cell C1, but the subframe #6 undergoes interference from the
subframe #9 of the macro-cell C2. Further, the subframes #4 and #5
of the pico-cell C1 undergo interference respectively by downlink
control channels of the subframes #7 and #8 of the macro-cell C2.
In this Embodiment, the base station apparatus 20 (see FIG. 7) of
the pico-cell C1 transmits the downlink radio frame to a mobile
terminal apparatus 10 while avoiding resources that undergo
interference from the downlink radio frame of the macro-cell
C2.
[0036] In other words, in the downlink radio frame of the pico-cell
C1, resources that undergo interference from the downlink radio
frame of the macro-cell C2 are set as blank resources, and user
data is assigned except the blank resources. The user data is
assigned to each mobile terminal apparatus on a resource block
basis in each subframe by a scheduler. One resource block is
comprised of 12 contiguous subcarriers, and is configured with a
resource element as a minimum unit. In the resource block, first 3
symbols are used for the downlink control channel, and downlink
reference signals for each transmission antenna are arranged in a
part thereof. Accordingly, in the resource block of the pico-cell
C1, the user data is assigned to resource elements that avoid the
downlink control channel, downlink reference signals and blank
resources. For example, in the subframe #4 of the pico-cell C1, the
5th to 7th symbols undergo interference by the control channel of
the subframe #7 of the macro-cell C2. Therefore, in the subframe #4
of the pico-cell C1, the user data is assigned to resource elements
in the regions that avoid the 1st to 3rd symbols, 5th to 7th
symbols, downlink reference signals, and the like.
[0037] The blank resources of the downlink radio frame of the
pico-cell C1 are set based on the shift amount of transmission
timing of downlink radio frames of the pico-cell C1 and the
macro-cell C2, and a set position of the blank period of the
downlink radio frame of the macro-cell C2. The shift amount
indicates a shift of the downlink control channel in each subframe
of the pico-cell C1 and the macro-cell C2. Therefore, in the
subframe of the pico-cell C1, resources undergoing interference
from the downlink control channel of the macro-cell C2 are
specified by the shift amount. The set position of the blank period
enables a subframe with no interference to the control channel of
the pico-cell C1 to be specified by combining with the shift
amount. In this case, in the subframe of the pico-cell C1, as in
the subframe #6, in the subframe with no interference to the
control channel, resources undergoing interference from the
downlink control channel and the downlink data channel of the
macro-cell C2 are specified. Thus, resources undergoing
interference from the downlink radio frame of the macro-cell C2 are
specified, and the resources are set as blank resources.
[0038] In addition, the blank resources set by the base station
apparatus of the pico-cell are resources set on the premise of
undergoing interference from the radio frame of the micro-cell C2.
In this case, the blank resources may be resources to which any
data is not assigned at all, or may be defined as resources to
which unnecessary data is assigned. Further, the blank resources
may be defined as resources transmitted with transmission power of
predetermined transmission power or less.
[0039] In addition, the shift amount may be configured so that the
base station apparatus 20 of the pico-cell C1 (see FIG. 7) receives
signaling of the base station apparatus 40 of the macro-cell,
alternatively, the reverse may be possible. Further, the base
station apparatus 40 of the macro-cell notifies the base station
apparatus 20 of the pico-cell of the set position of the blank
period. In addition, in the case of suppressing only interference
by the control channel of the macro-cell C2, the base station
apparatus 40 of the macro-cell does not need to notify the base
station apparatus 20 of the pico-cell of the set position of the
blank period.
[0040] Further, the mobile terminal apparatus 10 of the pico-cell
C1 is notified of the allocation position of the blank resources of
the downlink radio frame of the pico-cell C1 as blank resource
information. By this configuration, the mobile terminal apparatus
10 of the pico-cell C1 is capable of demodulating the user data
while avoiding the blank resources of the downlink radio frame. In
this case, the blank resource information may be notified to the
mobile terminal apparatus 10 for each subframe. Further, when the
blank resource information is stored in the mobile terminal
apparatus 10 in association with the shift amount of transmission
timing of downlink radio frames of the pico-cell C1 and the
macro-cell C2, notification to the mobile terminal apparatus 10 is
not necessary. This is because the mobile terminal apparatus 10 is
capable of estimating the allocation position of the blank
resources from the shift amount. By this configuration, the base
station apparatus 20 of the pico-cell C1 notifies the mobile
terminal apparatus 10 of only the shift amount, and it is possible
to reduce overhead.
[0041] Described next is suppression of interference to downlink
control channels of a downlink radio frame of the pico-cell by
transmission control in the base station apparatus of the
macro-cell. FIG. 6 is an explanatory view showing an example of
transmission control processing in the base station apparatus of
the macro-cell according to this Embodiment of the invention.
[0042] In the above-mentioned transmission control in the pico-cell
C1, interference is suppressed only to a part of control channels
by the blank periods of the downlink radio frame of the macro-cell
C2. Therefore, in the pico-cell C1, used is a part of subframes
with interference to control channels suppressed. In this
Embodiment, the base station apparatus 40 of the macro-cell C2
transmits a downlink radio frame to a mobile terminal apparatus 30
while avoiding resources that interfere with control channels of a
downlink radio frame of the pico-cell C1.
[0043] In other words, in the downlink radio frame of the
macro-cell C2, resources that interfere with downlink control
channels of the downlink radio frame of the pico-cell C1 are set as
blank resources, and user data is assigned to resources except the
blank resources. Accordingly, the user data is assigned to resource
elements that avoid the downlink control channel, downlink
reference signals, and blank resources that interfere with downlink
control channels of the pico-cell in the subframe of the macro-cell
C2. For example, in the subframe #4 of the macro-cell C2, the 5th
to 7th symbols interfere with the control channel of the subframe
#2 of the pico-cell C1. Therefore, in the subframe #4 of the
macro-cell C2, the user data is assigned to resource elements in
regions that avoid the 1st to 3rd symbols, 5th to 7th symbols,
downlink reference signals and the like.
[0044] The blank resources of the downlink radio frame of the
macro-cell C2 are set based on the shift amount of transmission
timing of downlink radio frames of the pico-cell C1 and the
macro-cell C2. The shift amount indicates a shift of the downlink
control channel in each subframe of the pico-cell C1 and the
macro-cell C2. Therefore, in the subframe of the macro-cell C2,
resources that interfere with the downlink control channel of the
pico-cell C1 are specified by the shift amount. Thus, resources
that interfere with the downlink radio frame of the pico-cell C1
are specified, and the resources are set as blank resources. In
addition, the shift amount may be configured so that the base
station apparatus 40 of the macro-cell C2 (see FIG. 7) receives
signaling of the base station apparatus 20 of the pico-cell,
alternatively, the reverse may be possible.
[0045] In addition, the blank resources set in the base station
apparatus of the macro-cell are resources set not to interfere with
the control channel of the radio frame of the pico-cell C1. In this
case, the blank resources may be resources to which any data is not
assigned at all, or may be defined as resources to which
unnecessary data is assigned. Further, the blank resources may be
defined as resources transmitted with transmission power of
predetermined transmission power or less.
[0046] Further, the mobile terminal apparatus 30 of the macro-cell
C2 is notified of the allocation position of the blank resources of
the downlink radio frame of the macro-cell C2 as blank resource
information. By this configuration, the mobile terminal apparatus
30 of the macro-cell C2 is capable of demodulating the user data
while avoiding the blank resources of the downlink radio frame. In
this case, the blank resource information may be notified to the
mobile terminal apparatus 30 for each subframe. Further, when the
blank resource information is stored in the mobile terminal
apparatus 30 in association with the shift amount of transmission
timing of downlink radio frames of the pico-cell C1 and the
macro-cell C2, notification to the mobile terminal apparatus 30 is
not necessary. This is because the mobile terminal apparatus 30 is
capable of estimating the allocation position of the blank
resources from the shift amount. By this configuration, the base
station apparatus 40 of the macro-cell C2 notifies the mobile
terminal apparatus 30 of only the shift amount, and it is possible
to reduce overhead.
[0047] Herein, a radio communication system according to the
Embodiment of the invention will be described specifically. FIG. 7
is an explanatory view of a system configuration of the radio
communication system according to this Embodiment. In addition, for
example, the radio communication system as shown in FIG. 7 is a
system including the LTE system, or SUPER 3G. Further, the radio
communication system may be called IMT-Advanced or may be called
4G.
[0048] As shown in FIG. 7, the radio communication system is the
HetNet, and a hierarchical network is constructed using the first
system having the macro-cell C2 and the second system having the
pico-cell C1. The first system includes the base station apparatus
40 that covers the macro-cell C2, and mobile terminal apparatuses
30 (only one is shown) that communicate with the base station
apparatus 40 and is comprised thereof. The second system includes
the base station apparatus 20 that covers the pico-cell C1, and
mobile terminal apparatuses 10 (only one is shown) that communicate
with the base station apparatus 20 and is comprised thereof. In the
base station apparatuses 20, 40, each scheduler allocates radio
resources on a resource block basis for each user. Further, each of
the base station apparatuses 20, 40 is connected to an upper
station apparatus, not shown, and is connected to a core network 50
via the upper station apparatus. In addition, for convenience in
description, the description is given while assuming that
equipments that perform radio communication with the base station
apparatuses 20, 40 are mobile terminal apparatuses, and more
generally, the equipments may be user equipments (UEs) including
mobile terminal apparatuses and fixed terminal apparatuses.
[0049] In the radio communication system, as a radio access scheme,
OFDMA (Orthogonal Frequency Division Multiple Access) is applied in
downlink, while SC-FDMA (Single-Carrier Frequency Division Multiple
Access) is applied in uplink. OFDMA is a multicarrier transmission
scheme for dividing a frequency band into a plurality of narrow
frequency bands (subcarriers), and mapping data to each subcarrier
to perform communication. SC-FDMA is a single-carrier transmission
scheme for dividing the system band into bands comprised of a
single or consecutive resource blocks for each terminal so that a
plurality of terminals uses mutually different bands, and thereby
reducing interference among the terminals.
[0050] Described herein are communication channels in the LTE
system. Communication channels in downlink have the PDSCH as a
downlink data channel shared among mobile terminal apparatuses, and
downlink L1/L2 control channels (PDCCH, PCFICH, PHICH). User data
and higher control information is transmitted on the PDSCH.
Scheduling information of the PDSCH and PUSCH and others are
transmitted on the PDCCH. The number of OFDM symbols used in the
PDCCH is transmitted on the PCFICH (Physical Control Format
[0051] Indicator Channel). ACK/NACK of HARQ (Hybrid Automatic
Repeat reQuest) to the PUSCH is transmitted on the PHICH (Physical
Hybrid-ARQ Indicator Channel).
[0052] Uplink communication channels have the PUSCH (Physical
Uplink Shared Channel) as an uplink data channel shared among
mobile terminal apparatuses, and the PUCCH (Physical Uplink Control
Channel) that is an uplink control channel. User data and higher
control information is transmitted on the PUSCH. Further, downlink
radio quality information (CQI: Channel Quality Indicator),
ACK/NACK and others are transmitted on the PUCCH.
[0053] Referring to FIG. 8, described next is the entire
configuration of the base station apparatus that covers the
pico-cell according to this Embodiment. In addition, the base
station apparatus that covers the macro-cell has the same
configuration as that of the base station apparatus of the
pico-cell, and the description thereof is omitted herein. Further,
for convenience in description, the processing of signals
transmitted from the mobile terminal apparatus to the base station
apparatus in uplink is omitted.
[0054] The base station apparatus 20 is provided with a
transmission/reception antenna 201, amplifying section 202,
transmission/reception section 203, baseband signal processing
section 204, call processing section 205 and transmission path
interface 206. The user data transmitted from the base station
apparatus 20 to the mobile terminal apparatus 10 in downlink is
input to the baseband signal processing section 204 via the
transmission path interface 206 from the upper station
apparatus.
[0055] The baseband signal processing section 204 performs, on a
signal of the downlink data channel, PDCP layer processing,
segmentation and concatenation of the user data, RLC (Radio Link
Control) layer transmission processing such as transmission
processing of RLC retransmission control, MAC (Medium Access
Control) retransmission control e.g. transmission processing of
HARQ, scheduling, transmission format selection, channel coding,
Inverse Fast Fourier Transform (IFFT) processing and precoding
processing. Further, with respect to a signal of the downlink
control channel, the transmission processing such as channel coding
and Inverse Fast Fourier Transform is also performed. Furthermore,
on the broadcast channel, the baseband signal processing section
204 notifies the mobile terminal apparatuses 10 connected to the
same cell C1 of control information for each mobile terminal
apparatus 10 to perform radio communication with the base station
apparatus 20.
[0056] The transmission/reception section 203 converts the
frequency of the baseband signal output from the baseband signal
processing section 204 into a radio frequency band. The amplifying
section 202 amplifies the transmission signal with the frequency
converted to output to the transmission/reception antenna 201.
[0057] Referring to FIG. 9, described next is the entire
configuration of the mobile terminal apparatus located in the
pico-cell according to this
[0058] Embodiment. In addition, the mobile terminal apparatus
located in the macro-cell has the same configuration as that of the
mobile terminal apparatus located in the pico-cell, and the
description thereof is omitted herein. Further, for convenience in
description, the processing of signals transmitted from the mobile
terminal apparatus to the base station apparatus in uplink is
omitted.
[0059] The mobile terminal apparatus 10 is provided with a
transmission/reception antenna 101, amplifying section 102,
transmission/reception section 103, baseband signal processing
section 104 and application section 105. With respect to
transmission data in downlink, a radio frequency signal received in
the transmission/reception antenna 101 is amplified in the
amplifying section 102, subjected to frequency conversion in the
transmission/reception section 103, and is converted into a
baseband signal.
[0060] The baseband signal processing section 104 performs, on the
baseband signal, FFT processing, error correcting decoding,
reception processing of retransmission control, etc. Among the data
in downlink, user data in downlink is transferred to the
application section 105. The application section 105 performs
processing concerning layers higher than the physical layer and MAC
layer and the like. Further, among the data in downlink, broadcast
information is also transferred to the application section 105.
[0061] Referring to FIG. 10, described is a process of generating a
downlink transmission frame in the base station apparatus that
covers the pico-cell. FIG. 10 is a conceptual diagram of the
process of generating a downlink transmission frame in the base
station apparatus that covers the pico-cell according to this
Embodiment.
[0062] As shown in FIG. 10, the process of generating a
transmission frame has a blank resource position determining
section 211 and a transmission frame generating section 212. The
blank resource position determining section 211 determines an
allocation position of blank resources, based on the set position
of the blank period notified from the base station apparatus 40 of
the macro-cell C2 and the shift amount as described above. In this
case, the blank resource position determining section 211
identifies a subframe of which the downlink control channel does
not undergo interference by the shift amount and the set position
of the blank period. Further, in the subframe, the blank resource
position determining section 211 identifies the resource position
that undergoes interference from the downlink control channel and
downlink data channel of the downlink transmission frame of the
macro-cell C2, and determines the allocation position of blank
resources. Thus, resources in which the downlink transmission frame
of the macro-cell C2 undergoes interference are set as blank
resources.
[0063] Next, the transmission frame generating section 212 arranges
user data while avoiding downlink control channels, downlink
reference signals, blank resources, etc. based on the allocation
position of the blank resources, and applies the other transmission
processing to generate a downlink transmission frame.
[0064] Referring to FIG. 11, described is a process of receiving
the downlink transmission frame in the mobile terminal apparatus
that communicates via the pico-cell. FIG. 11 is a conceptual
diagram of the process of receiving the downlink transmission frame
in the mobile terminal apparatus that communicates via the
pico-cell according to this Embodiment.
[0065] As shown in FIG. 11, the process of receiving the
transmission frame has a blank resource information acquiring
section 111, and a user data demodulation section 112. The blank
resource information acquiring section 111 acquires the blank
resource information indicative of the allocation position of the
blank resources from the base station apparatus 20. The blank
resource information may be information that directly indicates the
allocation position of the blank resources, or may be the shift
amount of downlink radio frames of the pico-cell C1 and the
macro-cell C2 as described above. Further, the mobile terminal
apparatus 10 may acquire the blank resource information for each
subframe.
[0066] The user data demodulation section 112 demodulates the user
data from the transmission frame based on the blank resource
information. In this case, the user data demodulation section 112
demodulates the user data, while ignoring resources indicated by
the blank resource information.
[0067] Thus, the base station apparatus 20 of the pico-cell C1
assigns the user data to subframes while avoiding resources that
undergo interference from the downlink radio frame of the
macro-cell C2. Therefore, in the downlink transmission frame of the
pico-cell C1, interference to downlink data channels is suppressed
in subframes with interference to downlink control channels from
the macro-cell C2 suppressed.
[0068] Referring to FIG. 12, described is a process of generating a
downlink transmission frame in the base station apparatus that
covers the macro-cell. FIG. 12 is a conceptual diagram of the
process of generating a downlink transmission frame in the base
station apparatus that covers the macro-cell according to this
Embodiment.
[0069] As shown in FIG. 12, the process of generating a
transmission frame has a blank resource position determining
section 411 and a transmission frame generating section 412. The
blank resource position determining section 411 determines an
allocation position of blank resources, based on the shift amount
of radio frames in the macro-cell C2 and the pico-cell C1. In this
case, the blank resource position determining section 411
identifies a resource position that interferes with the downlink
control channel of the downlink radio frame of the pico-cell C1 by
the shift amount, and determines the allocation position of blank
resources. Thus, resources that interfere with the control channel
of the transmission frame of the pico-cell C1 are set as blank
resources.
[0070] Next, the transmission frame generating section 412 arranges
user data while avoiding downlink control channels, downlink
reference signals, blank resources, etc. based on the allocation
position of the blank resources, and applies the other transmission
processing to generate a downlink transmission frame.
[0071] Referring to FIG. 13, described is a process of receiving
the downlink transmission frame in the mobile terminal apparatus
that communicates via the macro-cell. FIG. 13 is a conceptual
diagram of the process of receiving the downlink transmission frame
in the mobile terminal apparatus that communicates via the
macro-cell according to this Embodiment.
[0072] As shown in FIG. 13, the process of receiving the
transmission frame has a blank resource information acquiring
section 311, and a user data demodulation section 312. The blank
resource information acquiring section 311 acquires the blank
resource information indicative of the allocation position of the
blank resources from the base station apparatus 40. The blank
resource information may be information that directly indicates the
allocation position of the blank resources, or may be the shift
amount of downlink radio frames of the pico-cell C1 and the
macro-cell C2 as described above. Further, the mobile terminal
apparatus 30 may acquire the blank resource information for each
subframe.
[0073] The user data demodulation section 312 demodulates the user
data from the transmission frame based on the blank resource
information. In this case, the user data demodulation section 312
demodulates the user data, while ignoring resources indicated by
the blank resource information.
[0074] Thus, the base station apparatus 40 of the macro-cell C2
assigns the user data to subframes while avoiding resources that
interfere with the control channel of the downlink radio frame of
the pico-cell C1. Therefore, in the downlink transmission frame of
the pico-cell C1, interference to the downlink control channel from
the macro-cell C2 is suppressed.
[0075] As described above, according to the base station
apparatuses 20, 40 according to this Embodiment, interference is
suppressed which a downlink transmission frame transmitted from the
base station apparatus of the pico-cell undergoes from a downlink
transmission frame transmitted from the base station apparatus of
the macro-cell. In other words, interference of data channels is
suppressed in subframes with interference of control channels of
the pico-cell C1 suppressed by MBSFN subframes of the downlink
transmission frame of the macro-cell C2. Further, in subframes
except the MBSFN subframes of the downlink transmission frame of
the macro-cell C2, interference to control channels of the downlink
transmission frame of the pico-cell is suppressed. Accordingly,
interference to the downlink transmission frame of the pico-cell is
sufficiently suppressed. Thus, it is possible to cause the base
station apparatuses 20, 40 to perform control adapted to
interference inside the Heterogeneous network having the macro-cell
C2 and the pico-cell C1.
[0076] In addition, the aforementioned Embodiment describes the
base station apparatus that covers the pico-cell as a small-scale
cell, but the invention is not limited to this configuration. It is
essential only that the base station apparatus covers a cell that
undergoes interference from the macro-cell, and the base station
apparatus may be small-sized base station apparatuses that cover a
femto-cell, micro-cell and the like.
[0077] Further, in the above-mentioned Embodiment, the blank period
indicates a period during which the radio frame of the pico-cell is
not affected by interference from the radio frame of the
macro-cell. In the radio frame of the macro-cell, the blank period
may be a period during which no data is transmitted, or may be
defined as a period during which data is transmitted to the extent
that does not affect interference. Further, in the radio frame of
the macro-cell, the blank period may be defined as a period during
which transmission is performed with transmission power of the
extent that does not have any effect of interference on the radio
frame of the pico-cell. Furthermore, in the radio frame of the
macro-cell, the blank period may be defined as a period during
which transmission is performed with an interfering amount of the
extent that does not affect the radio frame of the pico-cell.
[0078] The present invention is not limited to the above-mentioned
Embodiment, and is capable of being carried into practice with
various modifications thereof. For example, without departing from
the scope of the invention, assignment of component carriers, the
number of processing sections, processing procedures, the number of
component carriers, and the number of aggregated component carriers
in the above-mentioned description are capable of being carried
into practice with modifications thereof as appropriate. Further,
the invention is capable of being carried into practice with
modifications thereof as appropriate without departing from the
scope of the invention.
* * * * *