U.S. patent application number 16/150403 was filed with the patent office on 2019-01-31 for user terminal, radio base station, radio communication system, and radio communication 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 Hiroki Harada, Satoshi Nagata, Kazuki Takeda.
Application Number | 20190036571 16/150403 |
Document ID | / |
Family ID | 55908944 |
Filed Date | 2019-01-31 |
![](/patent/app/20190036571/US20190036571A1-20190131-D00000.png)
![](/patent/app/20190036571/US20190036571A1-20190131-D00001.png)
![](/patent/app/20190036571/US20190036571A1-20190131-D00002.png)
![](/patent/app/20190036571/US20190036571A1-20190131-D00003.png)
![](/patent/app/20190036571/US20190036571A1-20190131-D00004.png)
![](/patent/app/20190036571/US20190036571A1-20190131-D00005.png)
![](/patent/app/20190036571/US20190036571A1-20190131-D00006.png)
![](/patent/app/20190036571/US20190036571A1-20190131-D00007.png)
![](/patent/app/20190036571/US20190036571A1-20190131-D00008.png)
![](/patent/app/20190036571/US20190036571A1-20190131-D00009.png)
![](/patent/app/20190036571/US20190036571A1-20190131-D00010.png)
View All Diagrams
United States Patent
Application |
20190036571 |
Kind Code |
A1 |
Takeda; Kazuki ; et
al. |
January 31, 2019 |
USER TERMINAL, RADIO BASE STATION, RADIO COMMUNICATION SYSTEM, AND
RADIO COMMUNICATION METHOD
Abstract
In one aspect, a user terminal is provided that includes a
transmitter that, if the user terminal is configured with a
plurality of cell groups each including one or more cells,
transmits uplink control information (UCI) including at least one
ACK/NACK bit for each of the cell groups, and a processor that
controls whether or not to bundle a plurality of ACK/NACK bits per
cell group, independently depending on whether the UCI is
transmitted by using a physical uplink control channel (PUCCH) or a
physical uplink shared channel (PUSCH). In another aspect, a radio
base station is provided.
Inventors: |
Takeda; Kazuki; (Tokyo,
JP) ; Harada; Hiroki; (Tokyo, JP) ; Nagata;
Satoshi; (Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
NTT DOCOMO, INC. |
Tokyo |
|
JP |
|
|
Assignee: |
NTT DOCOMO, INC.
Tokyo
JP
|
Family ID: |
55908944 |
Appl. No.: |
16/150403 |
Filed: |
October 3, 2018 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
15524700 |
May 5, 2017 |
10128919 |
|
|
PCT/JP2015/078743 |
Oct 9, 2015 |
|
|
|
16150403 |
|
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04B 7/0404 20130101;
H04L 27/2662 20130101; H04W 72/04 20130101; H04L 5/0055 20130101;
H04L 1/1861 20130101; H04W 28/04 20130101; H04L 5/0037 20130101;
H04L 5/001 20130101; H04L 27/2601 20130101 |
International
Class: |
H04B 7/0404 20060101
H04B007/0404 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 6, 2014 |
JP |
2014-226504 |
Claims
1. A user terminal comprising: a transmitter that, if the user
terminal is configured with a plurality of cell groups each
including one or more cells, transmits uplink control information
(UCI) including at least one ACK/NACK bit for each of the cell
groups; and a processor that controls whether or not to bundle a
plurality of ACK/NACK bits per cell group, independently depending
on whether the UCI is transmitted by using a physical uplink
control channel (PUCCH) or a physical uplink shared channel
(PUSCH).
2. The user terminal according to claim 1, wherein the PUCCH is a
PUCCH of a specific cell within a cell group corresponding to the
UCI, and the PUSCH is a PUSCH which is allocated to a given cell
within the cell group belonging to the UCI.
3. The user terminal according to claim 1, wherein when the UCI is
transmitted by using PUCCH, the processor bundles the plurality of
ACK/NACK bits and when the UCI is transmitted by using the PUSCH,
the processor cancels bundling the plurality of ACK/NACK bits.
4. A radio base station comprising: a receiving that, if a user
terminal is configured with a plurality of cell groups each
including one or more cells, receives uplink control information
(UCI) including at least one ACK/NACK bit for each of the cell
groups; and a processor that controls transmission of a physical
downlink shared channel (PDSCH) based on the ACK/NACK bit that is
controlled to be bundled or not per cell group, independently
depending on whether the user terminal transmits the UCI by using a
physical uplink control channel (PUCCH) or a physical uplink shared
channel (PUSCH).
5. The user terminal according to claim 2, wherein when the UCI is
transmitted by using PUCCH, the processor bundles the plurality of
ACK/NACK bits and when the UCI is transmitted by using the PUSCH,
the processor cancels bundling the plurality of ACK/NACK bits.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a continuation application and,
thereby, claims benefit under 35 U.S.C. .sctn. 120 to U.S. patent
application Ser. No. 15/524,700 filed on May 5, 2017, titled, "USER
TERMINAL, RADIO BASE STATION, RADIO COMMUNICATION SYSTEM, AND RADIO
COMMUNICATION METHOD," which is a national stage application of PCT
Application No. PCT/JP2015/078743, filed on Oct. 9, 2015, which
claims priority to Japanese Patent Application 2014-226504 filed on
Nov. 6, 2014. The contents of the priority applications are
incorporated by reference in their entirety.
TECHNICAL FIELD
[0002] The present invention relates to a user terminal, a radio
base station, a radio communication system, and a radio
communication method for a next-generation mobile communication
system.
BACKGROUND ART
[0003] For the universal mobile telecommunication system (UMTS)
network, the long term evolution (LTE) has been specified for
further enhanced data rates and less delay (see Non-Patent
Literature 1). The LTE advanced has been specified for achieving
even wider bands and higher speed than those of LTE, and the
succeeding systems of LTE, such as future radio access (FRA), are
under study.
[0004] The system band LTE Rel.10/11 includes at least one
component carrier (CC) that uses an LTE system band as one unit.
Band expansion through the aggregation of multiple component
carriers is referred to as carrier aggregation (CA).
[0005] For LTE Rel.12, which is a more recent LTE system, various
scenarios are under study to use a plurality of cells in different
frequency bands (carriers). When essentially identical radio base
stations are used for a plurality of cells, aforementioned carrier
aggregation can be used. When completely different radio base
stations are used for a plurality of cells, dual connectivity (DC)
can be used.
[0006] LTE Rel.8 to Rel.12 have been specified assuming the
exclusive use of frequency bands given to providers, i.e., licensed
bands. For licensed bands, 800 MHz, 2 GHz, and 1.7 GHz, for
example, are used.
[0007] LTE Rel.13 or later also target the use of frequency bands
that do not require licenses, i.e., unlicensed bands. Unlicensed
bands include 2.4 GHz and 5 GHz, which are the same bands as Wi-Fi.
LTE Rel.13 aims at carrier aggregation of licensed bands and
unlicensed bands (license-assisted access (LAA)) and will possibly
aim at dual connectivity and stand-alone unlicensed bands in
future.
CITATION LIST
Non Patent Literature
[0008] Non Patent Literature 1
[0009] 3GPP TS 36.300 "Evolved Universal Terrestrial Radio Access
(E-UTRA) and Evolved Universal Terrestrial Radio Access Network
(E-UTRAN); Overall description; Stage 2"
SUMMARY OF INVENTION
Technical Problem
[0010] Carrier aggregation according to LTE Rel.10/11/12 limits the
maximum number of component carriers that can be allocated to each
user terminal to five. LTE Rel.13 or later can allocate at least
six component carriers to each user terminal in order to achieve
more flexible and higher-speed wireless communication and is
studying use of extended carrier aggregation of these component
carriers.
[0011] However, extension of PUCCHs and change of the MAC system
would be required to achieve extended carrier aggregation that can
allocate at least six component carriers to each user terminal.
[0012] An object of the present invention, which has been made to
solve this problem, is to provide a user terminal, a radio base
station, a radio communication system, and a radio communication
method that enable proper operation of extended carrier aggregation
that can allocate at least six component carriers to each user
terminal.
Solution to Problem
[0013] A user terminal of the present invention communicates with a
radio base station that configures a plurality of cell groups each
of which including one or more cells. The user terminal includes: a
control unit that controls six or more component carriers
configured by the radio base station; and a transmitting/receiving
unit that receives information on a plurality of component carriers
configured by the radio base station and feedbacks ACK/NACK
information to one of the component carriers in each cell
group.
Advantageous Effect of Invention
[0014] The present invention enables proper operation of extended
carrier aggregation that can allocate at least six component
carriers to each user terminal.
BRIEF DESCRIPTION OF DRAWINGS
[0015] FIGS. 1A, 1B, and 1C are diagrams for explaining
conventional carrier aggregation.
[0016] FIG. 2 is a diagram for explaining extended carrier
aggregation.
[0017] FIGS. 3A and 3B are diagrams for explaining an example of
extended carrier aggregation according to the first embodiment.
[0018] FIG. 4 is a diagram for explaining an example of extended
carrier aggregation according to the first embodiment.
[0019] FIGS. 5A and 5B are diagrams for explaining an example of
extended carrier aggregation according to the first embodiment.
[0020] FIG. 6 is a diagram for explaining an example of extended
carrier aggregation according to the second embodiment.
[0021] FIG. 7 is a diagram for explaining an example of extended
carrier aggregation according to the second embodiment.
[0022] FIG. 8 is a diagram for explaining an example of extended
carrier aggregation according to the second embodiment.
[0023] FIGS. 9A and 9B are diagrams for explaining an example of
extended carrier aggregation according to the second
embodiment.
[0024] FIGS. 10A and 10 B are diagrams for explaining MAC CE for
controlling activation/deactivation according to the third
embodiment.
[0025] FIGS. 11A and 11B are diagrams for explaining
activation/deactivation of a cell group according to the third
embodiment.
[0026] FIG. 12 is a diagram showing an example schematic
configuration of a radio communication system according to this
embodiment.
[0027] FIG. 13 is a diagram showing an example overall
configuration of a radio base station according to this
embodiment.
[0028] FIG. 14 is a diagram showing an example functional
configuration of a radio base station according to this
embodiment.
[0029] FIG. 15 is a diagram showing an example overall
configuration of a user terminal according to this embodiment.
[0030] FIG. 16 is a diagram showing an example functional
configuration of a user terminal according to this embodiment.
DESCRIPTION OF EMBODIMENTS
[0031] Embodiments of the present invention will now be described
with reference to the drawings.
[0032] LTE Rel.10 has employed carrier aggregation of up to five
component carriers to widen the band, achieving a higher data rate
(see FIG. 1A).
[0033] LTE Rel.11 has employed multiple timing advance (MTA) in
which component carriers under inter-band carrier aggregation can
be independently controlled in different timings, achieving
optimization of carrier aggregation of non-co-located component
carriers (see FIG. 1B).
[0034] Carrier aggregation using multiple timing advance supports
timing advance groups (TAGs) classified according to their
transmission timings. Referring to FIG. 1B, CC #1 to CC #3 are
grouped into TAG #1, and CC #4 and CC #5 are grouped into TAG #2.
Transmission timing control based on timing advance values is
independently performed TAG by TAG. Accordingly, in carrier
aggregation using multiple timing advances, a user terminal adjusts
transmission timings for component carriers in each multiple timing
advance group, so that the times when the radio base station
receives uplink signals from the user terminal can be synchronized.
For instance, it is possible to individually control the timings of
transmission of uplink signals from the user terminal through CC #1
to CC #3 formed by the radio base station and through CC #4 and CC
#5 formed by the remote radio head (RRH) connected to the radio
base station.
[0035] LTE Rel.12 has employed dual connectivity that aggregates
cell groups (CGs) provided by a plurality of radio base stations
connected through non-ideal backhaul which cannot neglect delays,
achieving more flexible arrangement (see FIG. 1C).
[0036] Dual connectivity assumes that scheduling is performed for
the individual schedulers of the plurality of radio base stations.
Each user terminal is given a plurality of cell groups (CGs) by a
radio base station, and scheduling and HARQ control are performed
separately for the individual cell groups. This enables carrier
aggregation of component carriers in cell groups formed by radio
base stations, which are placed in different positions and perform
scheduling independently. Note that dual connectivity supports
multiple timing advance in the given cell group.
[0037] Referring to FIG. 1C, CC #1 to CC #3 are grouped into Cell
group #1, and CC #4 and CC #5 are grouped into Cell group #2. In
Cell group #1, CC #1 and CC #2 are grouped into TAG #1, and CC #3
is grouped into TAG #2. In cell group #3, CC #4 and CC #5 are
grouped into TAG #3. Accordingly, with dual connectivity and
carrier aggregation using multiple timing advance, independent
schedulers control signals transmitted through CC #1 to CC #3
formed by the first radio base station and the RRH connected
thereto and signals transmitted through CC #4 and CC #5 formed by
the second radio base station, for example. Further, for each cell
group, transmission timings for component carriers in different
timing advance groups are adjusted by coordination between the
schedulers in the radio base stations, so that the times when the
radio base station receives uplink signals from the user terminal
can be synchronized.
[0038] However, as shown in FIGS. 1A to 1C, LTE Rel.12 or earlier
limits the maximum number of component carriers that can be
allocate (configured) to each user terminal to five.
[0039] In contrast, LTE Rel.13 aims at extended carrier aggregation
(CA enhancement) without limiting the number of component carriers
that can be allocated to each user terminal. For example, as shown
in FIG. 2, extended carrier aggregation aims at aggregation of 16
component carriers. Such extended carrier aggregation achieves more
flexible and higher-speed wireless communication. Thus, such
extended carrier aggregation can aggregate a large number of
component carriers of continuous ultra-wide bands.
[0040] Such extended carrier aggregation has a problem in that it
requires a larger size of overhead for feedback data required in an
uplink control channel. Examples of control data fed back through
uplink control channels include hybrid automatic repeat
request-acknowledge (HARQ-ACK) and channel quality indicator (CQI).
However, since conventional carrier aggregation assumes up to five
component carriers, HARQ-ACK of only up to five component carriers
can be multiplexed with a format of an existing physical uplink
control channel (PUCCH). Similarly, as for CQI feedback, CQI of
only a single component carrier can be transmitted through a
PUCCH.
[0041] Besides, such extended carrier aggregation has another
problem in that it complicates user terminal control related to
downlinks. In existing carrier aggregation, physical downlink
control channels (PDCCHs), physical downlink shared channels
(PDSCHs), or physical uplink shared channels (PUSCHs) are
independently processed for each component carrier. For this
reason, as the number of component carriers increases, more
channels (several times the number of component carries) need to be
controlled.
[0042] As described above, extended carrier aggregation requires
PUCCH extension and change of the medium access control (MAC)
system.
[0043] To solve this problem, the present inventors found a
configuration for achieving extended carrier aggregation without
requiring PUCCH extension and change of the MAC control system and
limiting the number of component carriers that can be allocated to
each user terminal.
First Embodiment
[0044] In the first embodiment, extended carrier aggregation uses
Dual-PUCCHs defined by existing dual connectivity.
[0045] With dual connectivity, a PUCCH is allocated to one of the
component carriers in each cell group. Thus, uplink control
information (UCI) feedback is performed for each cell group
separately. A component carrier given a PUCCH is a primary cell
(PCell), for example.
[0046] Accordingly, a combination of dual connectivity and
conventional carrier aggregation that can aggregate up to five
component carriers achieves extended carrier aggregation that can
support up to 10 component carriers (see FIG. 3A).
[0047] In FIG. 3A showing Cell group #1 including 5 CC of Component
carriers #1 to #5, and Cell group #2 including 5 CC of Component
carriers #6 to #10, Component carriers #1 and #6 are each given a
PUCCH. The user terminal performs UCI feedback using the mechanism
of existing LTE with up to five component carriers in each cell
group.
[0048] MTA, i.e., TA groups (TAGs) may be allocated to each cell
group (see FIG. 3B).
[0049] Increasing the number of component carriers to be given a
PUCCH by one from five achieves extended carrier aggregation that
can support up to 15 or 20 component carriers, for example (see
FIG. 4). To be specific, a combination of conventional carrier
aggregation and dual connectivity can increase the maximum number
of component carriers that can be supported by extended carrier
aggregation.
[0050] In the case shown in FIG. 4, extended carrier aggregation is
performed for Cell groups #1 to #4. Each cell group includes up to
five component carriers. To be specific, this extended carrier
aggregation supports 20 component carriers. A PUCCH is allocated to
one of the component carriers in each cell group. The user terminal
performs UCI feedback using the mechanism of existing LTE with up
to five component carriers in each cell group.
[0051] In the case shown in FIG. 4, dual connectivity may be
applied to two or more cell groups.
[0052] A user terminal may report band combinations that the user
terminal supports for downlink carrier aggregation and uplink
carrier aggregation, to the network. The user terminal may report
combinations of bands that can be allocated to different cell
groups, component carriers that can be given PUCCHs (capability),
and the like to the network.
[0053] The network transmits information on component carriers to
undergo downlink carrier aggregation or uplink carrier aggregation,
cell group allocation, and a component carrier to be given a PUCCH
in each cell group, to the user terminal by upper layer
signaling.
[0054] The user terminal initiates communication by extended
carrier aggregation based on the received information and feedbacks
uplink control information (UCI) using the mechanism of existing
LTE with up to five component carries in each cell group.
[0055] According to LTE Rel.11, up to four TAGs can be set.
However, with extended carrier aggregation, the maximum number of
assignable TAGs may be increased as the number of component
carriers increases. For example, eight TAGs may be allocated as
shown in FIG. 5A.
[0056] In general, a plurality of TAGs is allocated when radio base
stations with which the user terminal communicates use different
transmission/reception points. For this reason, in actuality, a
large number of (e.g., eight) TAGs are rarely required; thus,
existing specifications can probably support an adequate number of
TAGs. The number of TAGs may therefore be limited to below a
certain level, unlike the number of component carriers and cell
groups. For example, as shown in FIG. 5B, a plurality of cell
groups may be contained in the same TAG. In this case, the number
of component carriers to undergo carrier aggregation can be
increased without increasing the number of TAGs whose timing should
be separately controlled by the user terminal, thereby improving
the peak communication data rate while suppressing increases in the
cost of the user terminal and the consumption of battery.
Second Embodiment
[0057] In the second embodiment, extended carrier aggregation uses
Single-PUCCHs defined by existing carrier aggregation.
[0058] As described above, an existing PUCCH can only transmit
HARQ-ACK of up to five component carriers. In use of extended
carrier aggregation, to solve the problem of an excess number of
ACK/NACK (A/N) bits that can be multiplexed into a single PUCCH, a
plurality of component carriers may be collected into one group in
which A/N is bundled (bundling).
[0059] In the case shown in FIG. 6, 20 component carriers to
undergo extended carrier aggregation are grouped into A/N groups #1
to #4. An A/N group corresponds to a TAG or cell group. This means
that the user terminal may regard a TAG or cell group as an A/N
group. The component carriers in an A/N group receive a PDCCH or
enhanced PDCCH (EPDCCH) containing downlink assignment information
(DL assignment) on the respective component carriers, and
acknowledgement (ACK) or negative-acknowledgement (NACK) indicating
the results are bundled group by group. The user terminal transmits
UCI (A/N bundling) by using the PUCCH resource of a PCell. In the
case shown in FIG. 6, the A/N bit count is four. In use of
multiple-input and multiple-output (MIMO) for each component
carrier, to transmit/receive double data, for example, the maximum
A/N bit count is eight.
[0060] In this case, however, upon an error of reception of
downlink assignment information on any component carrier in an A/N
group, although not properly receiving downlink data assigned to
the component carrier of the A/N group, the user terminal may
determine that the result is acknowledgement (ACK) because it
cannot even check the presence of data. To solve this problem, a
radio base station may transmit downlink assignment information not
to individual component carriers but to individual A/N groups (or
TAGs or cell groups). To be specific, downlink control information
(DL assignment) and uplink control information (HARQ-ACK) may be
transmitted to individual A/N groups. Upon detection of downlink
assignment information, the user terminal bundles A/N of all
assignments and if no downlink assignment information is detected,
all assignments are discontinuous transmission (DTX).
[0061] In the case shown in FIG. 7, 20 component carriers to
undergo extended carrier aggregation are grouped into A/N groups #1
to #4, and downlink assignment and A/N bundling (bundling) are
performed for each group. Downlink assignment information (DL
assignment) is transmitted to one in an A/N group or a plurality of
component carriers. The user terminal may decode downlink
assignment information on one or more component carriers by blind
detection and component carriers through which transmission is
performed may be pre-specified by, for example, upper layer
signaling.
[0062] A user terminal performs blind detection on multiple blocks
of downlink assignment information and determines which cyclic
redundancy check (CRC)-checked blocks become downlink assignment
information that is allocated to that user terminal. This downlink
assignment information includes information on assignment to
multiple component carriers. This information specifies component
carriers assigned with data and includes link adaptation
information (e.g., frequency resource, the number of MIMO ranks,
modulation and coding scheme (MCS) level, and transport block (TB)
size) concerning each component carrier assigned with data. Link
adaptation information may be common to, or different between, the
component carriers in the same group. As common information
increases, overhead decreases. Greater numbers of different blocks
of information result in more detailed link adaptation, leading to
an improvement in throughput.
[0063] It should be noted that as shown in FIG. 8, if there is only
ACK/NACK for the component carriers in one A/N group, a fallback to
Rel.10/11 carrier aggregation may be carried out. To be specific,
when only the component carriers in one A/N group detect downlink
assignment information, the user terminal may transmit A/N for the
CCs in the A/N group without bundling.
[0064] Alternatively, when the user terminal detects a PDCCH
indicating assignment information for one component carrier, a
fallback to Rel.10/11 carrier aggregation may be carried out. The
user terminal performs blind detection of both a PDCCH indicating
assignment information for one component carrier and a PDCCH
containing assignment information for a plurality of
A/N-grouping-applied component carriers. In addition, upon
detection of a PDCCH indicating assignment information for one
component carrier, the user terminal may transmit A/N without
bundling.
[0065] The PUCCH resource and PUCCH format may be changed between
conventional carrier aggregation, which supports up to five
component carriers, and extended carrier aggregation, which
supports more than five component carriers. To be specific,
different PUCCH resources and PUCCH formats may be used to transmit
PUCCHs, depending on whether or not A/N bundling is used.
[0066] As shown in FIG. 9A, when a PUSCH is assigned to a given
target component carrier, the user terminal may transmit UCI
(ACK/NACK) by using a PUSCH resource without A/N bundling. This is
because a PUSCH, which has large capacity that can contain a large
number of bits, does not need compression by A/N bundling. In this
case, the A/N bit count is 20 to 40. As shown in FIG. 9B, when no
component carrier is assigned with a PUSCH, the user terminal may
perform A/N bundling and transmit UCI (A/N bundling) using a PUCCH
resource.
Third Embodiment
[0067] In the third embodiment, a method will be described of
deactivating unnecessary component carriers when there is no
traffic during extended carrier aggregation.
[0068] With extended carrier aggregation, carrier aggregation of a
large number of component carriers achieves high peak rates but
increases power consumption. It is therefore important to
deactivate unnecessary component carriers (de-activation) when
there is no traffic. With existing LTE, however, a MAC control
element (MAC CE) instructing activation/deactivation has only seven
bits (see FIG. 10A). To be specific, activation/deactivation
instructions are made with only seven cells.
[0069] To solve this problem, activation/deactivation instructions
may be made for individual groups of cells, such as TAGs, cell
groups, or A/N groups. In this case, C.sub.i in the MAC CE shown in
FIG. 10A may be regarded as representing an activation/deactivation
command for a cell group called SCell group index i. Notification
of the SCell group index is notified via an upper layer.
[0070] In a conventional scheme based on SCell index i, PCells and
PSCells under dual connectivity are not deactivated. Accordingly,
the MAC CE does not include C.sub.i (=SCell index i) corresponding
to a PCell. Therefore, if the conventional scheme based on SCell
index i is replaced with a scheme based on SCell group index i, an
activation/deactivation command cannot be transmitted to the cell
group including the PCell. Consequently, the cell group including
the PCell is always active (see FIG. 11A).
[0071] However, in order to suppress power consumption while there
is no traffic, it is preferable that deactivation of SCells be
possible even in the cell group including the PCell. Accordingly,
the third embodiment may allow an activation/deactivation command
to be transmitted to a cell group including a PCell or PSCell. Upon
reception of an instruction to deactivate the cell group including
a PCell or PSCell, the user terminal may deactivate only the SCells
in the cell group (see FIG. 11B). As shown in FIG. 11B, the PCell
or PSCell is always kept active independently of a command.
[0072] It should be noted that in addition to
activation/deactivation of individual cell groups, group-by-group
deactivation timer management may be carried out. Upon selection of
the cell group, the user terminal performs total management,
including deactivation timer control, on a group basis, although it
is traditionally carried out on a component carrier basis. This
facilitates implementation of the user terminal.
[0073] In existing LTE, a MAC CE, which provides a power headroom
report (PHR), reports activated/deactivated cells (see FIG. 10B).
In particular, a MAC CE, which provides a PHR, reports
activated/deactivated cells and the maximum transmission
power.sub.PCMAX,c and PHR for each activated cell. For C.sub.0,
which does not exist in an existing PHR MAC CE, a new line may be
added to extend the MAC CE so that up to 16 activated/deactivated
cells can be reported, or the reserved bit (R) may be set to 0 or
1.
[0074] In the third embodiment, C.sub.i reported by the PHR MAC CE
may be regarded as a group index i. With C.sub.i activated groups
and maximum transmission power P.sub.CMAX,c and transmission power
headroom PHR for active component carriers may be reported. PHR
timer and the like may also be managed on a group basis.
[0075] Alternatively, in addition to group-by-group
activation/deactivation, group-by-group PHR may be used. The user
terminal may report, through C.sub.i, activated groups and maximum
allowable power (e.g. P.sub.CMAX,g) and PHR for the individual
activated groups. PHR for each group is determined by subtracting
the total assignment power in the group from P.sub.CMAX,g.
(Configuration of Radio Communication System)
[0076] The configuration of a radio communication system according
to this embodiment will now be described. This radio communication
system employs a radio communication method in which uplink
transmission operation for LAA is performed in unlicensed
bands.
[0077] FIG. 12 is a diagram showing an example schematic
configuration of a radio communication system according to this
embodiment. This radio communication system can employ one or both
of dual connectivity and carrier aggregation that unites a
plurality of basic frequency blocks (component carriers) using a
system band width for an LTE system as one unit. Moreover, this
radio communication system includes radio base stations that can
use unlicensed bands.
[0078] As shown in FIG. 12, a radio communication system 1 includes
a plurality of radio base stations 10 (11 and 12) and a plurality
of user terminals 20 in cells formed by the radio base stations 10
and configured to communicate with the radio base stations 10. The
radio base stations 10 are connected to a higher station apparatus
30 and to a core network 40 via the higher station apparatus
30.
[0079] Referring to FIG. 12, the radio base station 11 is a macro
base station with relatively high coverage, forming a macro cell
C1. The radio base stations 12 are small base stations with low
coverage, forming small cells C2. It should be noted that the
number of the radio base stations 11 and 12 is not limited that in
FIG. 12.
[0080] For example, the macro cell C1 may be operated in a licensed
band, and the small cells C2 in an unlicensed band. Alternatively,
part of the small cells C2 may be operated in an unlicensed band,
and the rest of the small cells C2 in a licensed band. The radio
base stations 11 and 12 are connected to each other via an
inter-base station interface (e.g., optical fiber and X2
interface).
[0081] The user terminal 20 can be connected to both the radio base
station 11 and the radio base station 12. The user terminal 20 is
assumed to concurrently use the macro cell C1 and the small cell
C2, which use different frequencies, by carrier aggregation or dual
connectivity. For example, the radio base station 11 using a
licensed band can transmit the user terminal 20 assistance
information (e.g., downlink signal configuration) on the radio base
station 12 which uses an unlicensed band. To achieve carrier
aggregation between a licensed band and an unlicensed band, one
radio base station (e.g., the radio base station 11) may control
the schedules of licensed band cells and unlicensed band cells.
[0082] The user terminal 20 may be connected not to the radio base
station 11 but to the radio base station 12. For example, the radio
base station 12 using an unlicensed band may be connected to the
user terminal 20 in a standalone manner. In this case, the radio
base station 12 controls the schedules of unlicensed band
cells.
[0083] Examples of the higher station apparatus 30 include, but
should not be limited to, access gateway devices, wireless network
controllers (RNCs), and mobility management entities (MMEs).
[0084] Examples of the downlink channels used in the radio
communication system 1 include physical downlink shared channels
(PDSCHs) shared among user terminals 20, downlink control channels
(physical downlink control channels (PDCCHs) and enhanced physical
downlink control channels (EPDCCHs)), and physical broadcast
channels (PBCHs). User data, upper layer control information, and
predetermined system information blocks (SIBs) are transmitted
through PDSCHs. Downlink control information (DCI) is transmitted
through PDCCHs or EPDCCHs.
[0085] Examples of the uplink channels used in the radio
communication system 1 include physical uplink shared channels
(PUSCHs) shared among the user terminals 20 and physical uplink
control channels (PUCCHs). User data and upper layer control
information are transmitted through PUSCHs.
[0086] FIG. 13 is a diagram showing an overall configuration of the
radio base station 10 according to this embodiment. As shown in
FIG. 13, the radio base station 10 includes a plurality of
transmitting/receiving antennas 101 for multiple-input and
multiple-output (MIMO) transmission, amplifiers 102,
transmitting/receiving units (transmitting units and receiving
units) 103, a baseband signal processing unit 104, a call
processing unit 105, and an interface unit 106.
[0087] User data transmitted from the radio base station 10 to the
user terminals 20 through the downlink channel is input from the
higher station apparatus 30 to the baseband signal processing unit
104 through the interface unit 106.
[0088] The baseband signal processing unit 104 performs packet data
convergence protocol (PDCP) layer processing, user data
division/combination, transmission processing for an RLC layer,
such as transmission processing for radio link control (RLC)
retransmission control, medium access control (MAC) retransmission
control, such as transmission processing, scheduling, transmission
format selection, channel coding, inverse fast Fourier transform
(IFFT) processing, and pre-coding for hybrid automatic repeat
request (HARQ), and transfers the results to each
transmitting/receiving unit 103. Downlink control signals are also
subjected to transmission processing, such as channel coding and
inverse fast Fourier transform, and the results are transferred to
each transmitting/receiving unit 103.
[0089] Each transmitting/receiving unit 103 converts a downlink
signal, which is pre-coded for the corresponding antenna and output
from the baseband signal processing unit 104, to a
wireless-frequency signal. Each amplifier 102 amplifies the
wireless-frequency signal generated by frequency conversion and
transmits it through the corresponding transmitting/receiving
antenna 101. Each transmitting/receiving unit 103 is a
transmitter/receiver, a transmitting/receiving circuit, or a
transmitting/receiving device based on common understanding within
the technical field of the present invention.
[0090] The transmitting/receiving unit 103 transmits information on
six or more component carriers configured to a user terminal 20 and
receives ACK/NACK information fed back from one of the component
carriers in each cell group.
[0091] As for uplink signals, a wireless-frequency signal received
at each transmitting/receiving antenna 101 is amplified by the
corresponding amplifier 102, frequency-converted in the
corresponding transmitting/receiving unit 103 for conversion to a
baseband signal, and then input to the baseband signal processing
unit 104.
[0092] In the baseband signal processing unit 104, user data in the
received uplink signal is subjected to fast Fourier transform (FFT)
processing, inverse discrete Fourier transform (IDFT) processing,
error correction decoding, reception processing for MAC
retransmission control, and reception processing for RLC layers and
PDCP layers, and then transferred to the higher station apparatus
30 through the interface unit 106. The call processing unit 105
performs call processing, such as communication channel allocation
and release, management of the radio base station 10, and
management of the wireless resource.
[0093] The interface unit 106 transmits/receives signals (backhaul
signaling) to/from the adjacent radio base station through an
inter-BS interface (e.g., optical fiber and X2 interface).
Alternatively, the interface unit 106 transmits/receives signals
to/from the higher station apparatus 30 through a predetermined
interface.
[0094] FIG. 14 is a diagram showing a main functional configuration
of the baseband signal processing unit 104 included in the radio
base station 10 according to this embodiment. As shown in FIG. 14,
the baseband signal processing unit 104 included in the radio base
station 10 includes at least a control unit 301, a downlink control
signal generating unit 302, a downlink data signal generating unit
303, a mapping unit 304, a demapping unit 305, a channel estimating
unit 306, an uplink control signal decoding unit 307, an uplink
data signal decoding unit 308, and a judgment unit 309.
[0095] The control unit 301 controls scheduling for downlink user
data transmitted through a PDSCH, downlink control information
transmitted through one or both of a PDCCH and an extended PDCCH
(EPDCCH), downlink reference signals, and the like. Further, the
control unit 301 controls scheduling (assignment control) for RA
preambles transmitted through a PRACH, unlink data transmitted
through a PUSCH, uplink control information transmitted through a
PUCCH or PUSCH, and uplink reference signals. Information on
assignment control of uplink signals (uplink control signals and
uplink user data) is transmitted to user terminals 20 with the use
of downlink control signals (DCI).
[0096] The control unit 301 controls assignment of wireless
resources to downlink signals and uplink signals in accordance with
instructions from the higher station apparatus 30 and feedback
information from the user terminals 20. Thus, the control unit 301
serves as a scheduler. The control unit 301 is a controller, a
control circuit, or a control device based on common understanding
within the technical field of the present invention.
[0097] The downlink control signal generating unit 302 generates
downlink control signals (one or both of PDCCH signals and EPDCCH
signals) which are assigned by the control unit 301. To be
specific, the downlink control signal generating unit 302
generates, in accordance with instructions from the control unit
301, downlink assignment that provides assignment information on
downlink signals, and uplink grants that provide assignment
information on uplink signals. The downlink control signal
generating unit 302 is a signal generator or a signal generating
circuit based on common understanding within the technical field of
the present invention.
[0098] The downlink data signal generating unit 303 generates
downlink data signals (PDSCH signals) assigned to resources by the
control unit 301. Data signals generated by the downlink data
signal generating unit 303 are coded and modulated according to
coding rates and modulation methods determined by CSI and the like
sent from the user terminals 20.
[0099] The mapping unit 304 controls assignment of downlink control
signals generated in the downlink control signal generating unit
302 and downlink data signals generated in the downlink data signal
generating unit 303 to wireless resources in accordance with
instructions from the control unit 301. The mapping unit 304 is a
mapping circuit or a mapper based on common understanding within
the technical field of the present invention.
[0100] The demapping unit 305 performs demapping on uplink signals
transmitted from the user terminals 20, thereby dividing the uplink
signals. The channel estimating unit 306 estimates the channel
state from reference signals included in the received signals
resulting from division performed by the demapping unit 305, and
feeds the estimated channel state to the uplink control signal
decoding unit 307 and the uplink data signal decoding unit 308.
[0101] The uplink control signal decoding unit 307 decodes feedback
signals (e.g., arrival confirmation signals) transmitted from the
user terminals through uplink control channels (PRACHs, PUCCHs),
and feeds the results to the control unit 301. The uplink data
signal decoding unit 308 decodes uplink data signals transmitted
from the user terminals through physical uplink shared channels
(PUSCHs), and feeds the results to the judgment unit 309. The
judgment unit 309 performs retransmission control judgement (A/N
judgement) based on decoding results given by the uplink data
signal decoding unit 308 and feeds the results to the control unit
301.
[0102] FIG. 15 is a diagram showing an overall configuration of the
user terminal 20 according to this embodiment. As shown in FIG. 15,
the user terminal 20 includes a plurality of transmitting/receiving
antennas 201 for MIMO transmission, amplifiers 202,
transmitting/receiving units (transmitting units and receiving
units) 203, a baseband signal processing unit 204, and an
application unit 205.
[0103] For downlink data, wireless-frequency signals received at a
plurality of transmitting/receiving antennas 201 are amplified by
the respective amplifiers 202, frequency-converted in the
respective transmitting/receiving units 203 for conversion to
baseband signals. These baseband signals are subjected to FFT
processing, error correction decoding, retransmission control
reception processing, and the like in the baseband signal
processing unit 204. Downlink user data in this downlink data is
transferred to the application unit 205. The application unit 205
performs processing related to layers upper than physical layers
and MAC layers. System information in the downlink data is also
transferred to the application unit 205. Each
transmitting/receiving unit 203 is a transmitter/receiver, a
transmitting/receiving circuit, or a transmitting/receiving device
based on common understanding within the technical field of the
present invention.
[0104] Meanwhile, uplink user data is input from the application
unit 205 to the baseband signal processing unit 204. The baseband
signal processing unit 204 performs retransmission control (HARQ)
transmission processing, channel coding, pre-coding, discrete
Fourier transform (DFT) processing, inverse fast Fourier transform
(IFFT) processing, and the like, and the results are transferred to
each transmitting/receiving unit 203. Each transmitting/receiving
unit 203 converts a baseband signal, which is output from the base
band signal processing unit 204, to a wireless-frequency signal.
Subsequently, each amplifier 202 amplifies the frequency-converted
wireless-frequency signal which is then transmitted through the
corresponding transmitting/receiving antenna 201.
[0105] The transmitting/receiving unit 203 receives information on
a plurality of component carriers configured by the radio base
station 10 and feedbacks ACK/NACK information to one of the
component carriers in each cell group.
[0106] FIG. 16 is a diagram showing a main functional configuration
of the baseband signal processing unit 204 included in the user
terminal 20. As shown in FIG. 16, the baseband signal processing
unit 204 included in the user terminal 20 includes at least a
control unit 401, an uplink control signal generating unit 402, an
uplink data signal generating unit 403, a mapping unit 404, a
demapping unit 405, a channel estimating unit 406, a downlink
control signal decoding unit 407, a downlink data signal decoding
unit 408, and a judgment unit 409.
[0107] The control unit 401 controls generation of uplink control
signals (e.g., A/N signals) and uplink data signals on the basis of
downlink control signals (PDCCH signals) transmitted from the radio
base station 10 and the retransmission control judgement results
for the received PDSCH signals. Downlink control signals received
from the radio base station are output from the downlink control
signal decoding unit 407, and the retransmission control judgement
results are output from the judgment unit 409. The control unit 401
is a controller, a control circuit, or a control device based on
common understanding within the technical field of the present
invention.
[0108] The control unit 401 can control six or more component
carriers configured by the radio base station 10.
[0109] The uplink control signal generating unit 402 generates
uplink control signals (feedback signals such as arrival
confirmation signals and channel state information (CSI)) in
accordance with instructions from the control unit 401. The uplink
data signal generating unit 403 generates uplink data signals in
accordance with instructions from the control unit 401. It should
be noted that the control unit 401 instructs the uplink data signal
generating unit 403 to generate an uplink data signal when the
downlink control signal received from the radio base station
includes an uplink grant. The uplink control signal generating unit
402 is a signal generator or a signal generating circuit based on
common understanding within the technical field of the present
invention.
[0110] The mapping unit 404 controls assignment of uplink control
signals (e.g., arrival confirmation signals) and uplink data
signals to wireless resources (PUCCH, PUSCH) in accordance with
instructions from the control unit 401.
[0111] The demapping unit 405 performs demapping on downlink
signals transmitted from the radio base station 10 and divides the
downlink signals. The channel estimating unit 406 estimates the
channel state from reference signals contained in the received
signals resulting from division performed by the demapping unit
405, and feeds the estimated channel state to the downlink control
signal decoding unit 407 and the downlink data signal decoding unit
408.
[0112] The downlink control signal decoding unit 407 decodes
downlink control signals (PDCCH signals) transmitted through
physical downlink control channels (PDCCHs), and feeds scheduling
information (information on assignment to uplink resources) to the
control unit 401. It is also output to the control unit 401 when
any downlink control signal includes information on a cell to
feedback an arrival confirmation signal or information on the
necessity of RF adjustment.
[0113] The downlink data signal decoding unit 408 decodes downlink
data signals transmitted through physical downlink shared channels
(PDSCHs) and feeds the results to the judgment unit 409. The
judgment unit 409 performs retransmission control judgement (A/N
judgement) based on the decoding results provided by the downlink
data signal decoding unit 408, and feeds the judgement to the
control unit 401.
[0114] It should be noted that the present invention is not limited
to the above embodiments and various modifications can be made for
its implementation. In the above embodiments, the sizes and shapes
are not limited to those shown in the attached drawings and can be
modified in various ways without departing from a range in which
the advantageous effects of the present invention can be obtained.
Aside from that, various modifications can be made without
departing from the scope of the present invention.
* * * * *