U.S. patent application number 14/431529 was filed with the patent office on 2015-10-01 for radio communication system, base station apparatus, user terminal 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 Yuichi Kakishima, Yoshihisa Kishiyama, Kazuaki Takeda.
Application Number | 20150282102 14/431529 |
Document ID | / |
Family ID | 50387762 |
Filed Date | 2015-10-01 |
United States Patent
Application |
20150282102 |
Kind Code |
A1 |
Kakishima; Yuichi ; et
al. |
October 1, 2015 |
RADIO COMMUNICATION SYSTEM, BASE STATION APPARATUS, USER TERMINAL
AND RADIO COMMUNICATION METHOD
Abstract
The present invention is designed to make it possible to apply
power scaling to a period where the upper limit value is exceeded,
while maintaining uplink transmission quality. In a radio
communication system 1 in which multiple cells (C1 and C2) are
formed, a base station apparatus (20) forms a first cell C1, which
is one of the multiple cells, and has a control section (234) that
controls uplink transmission times per timing group, which includes
one component carrier or a plurality of component carriers, and a
transmission section (106) that signals a timing group or a
component carrier determined as a target of power scaling, as power
scaling target information, in which the timing group or the
component carrier, to which power scaling is applied, is expressly
determined, to a the user terminal (10).
Inventors: |
Kakishima; Yuichi; (Tokyo,
JP) ; Takeda; Kazuaki; (Tokyo, JP) ;
Kishiyama; Yoshihisa; (Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
NTT DOCOMO, INC. |
Tokyo |
|
JP |
|
|
Assignee: |
NTT DOCOMO, INC.
Tokyo
JP
|
Family ID: |
50387762 |
Appl. No.: |
14/431529 |
Filed: |
August 16, 2013 |
PCT Filed: |
August 16, 2013 |
PCT NO: |
PCT/JP2013/072008 |
371 Date: |
March 26, 2015 |
Current U.S.
Class: |
370/329 |
Current CPC
Class: |
H04W 88/08 20130101;
H04W 52/146 20130101; H04W 52/343 20130101; H04W 52/16 20130101;
H04W 52/32 20130101; H04W 72/0413 20130101; H04L 27/2601 20130101;
H04W 88/02 20130101; H04W 56/00 20130101; H04W 52/40 20130101; H04W
52/325 20130101; H04W 72/0453 20130101; H04W 52/346 20130101 |
International
Class: |
H04W 52/32 20060101
H04W052/32; H04L 27/26 20060101 H04L027/26; H04W 52/34 20060101
H04W052/34; H04W 72/04 20060101 H04W072/04 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 28, 2012 |
JP |
2012-218198 |
Claims
1. A radio communication system, in which multiple cells are
formed, and which comprises a plurality of base station apparatuses
that each form a cell included in the multiple cells, and a user
terminal that can connect to at least a first cell and a second
cell included in the multiple cells, wherein: the base station
apparatuses comprises: a control section that controls uplink
transmission times per timing group including one component carrier
or a plurality of component carriers; and a transmission section
that signals a timing group or a component carrier determined as a
target of power scaling, as power scaling target information, in
which the timing group or the component carrier, to which power
scaling is applied, is expressly determined, to the user terminal;
and the user terminal comprises: a receiving section that receives
the power scaling target information signaled from the base station
apparatus; a transmission section that transmits uplink signals at
different transmission times per timing group; and a power control
section that, when a total of uplink signal transmission power over
the first cell and the second cell exceeds a predetermined value,
applies power scaling to the timing group or the component carrier
determined in the power scaling target information.
2. The radio communication system according to claim 1, wherein the
base station apparatus signals the timing group or the component
carrier determined as the target of power scaling to the user
terminal through higher layer signaling.
3. The radio communication system according to claim 1, wherein the
base station apparatus expressly determines the timing group or the
component carrier, to which power scaling is applied, by using, as
an indicator, at least one of transmission quality and traffic of
the multiple cells, to which the user terminal is connected at the
same time.
4. The radio communication system according to claim 1, wherein:
when component carriers included in each cell, to which the user
terminal is connected at the same time, are classified into a
plurality of timing groups, the base station apparatus expressly
determines a specific physical uplink channel in each timing group
as a physical channel, to which power scaling is applied, and
signals the target of power scaling per physical channel; and when
the total of uplink signal transmission power over multiple cells,
to which the user terminal is connected at the same time, exceeds
the predetermined value, the user terminal applies power scaling to
the physical channels reported as the target of power scaling.
5. The radio communication system according to claim 1, wherein,
when the user terminal is connected to the first cell and the
second cell at the same time, the first cell is managed for control
signals, the second cell is managed for data transmission, a
component carrier included in the first cell is classified as a
first timing group, and a component carrier included in the second
cell is classified as a second timing group, the base station
apparatus expressly determines a physical uplink control channel
(PUCCH) of the first timing group, a physical uplink shared channel
(PUSCH) of the second timing group, and/or a reference signal (SRS)
for channel quality measurement, as physical channels, to which
power scaling is applied.
6. The radio communication system according to claim 1, wherein,
when the total of uplink signal transmission power over multiple
cells, to which the user terminal is connected at the same time,
exceeds the predetermined value, the user terminal allocates power
to a specific physical uplink channel preferentially, and,
excluding the specific physical uplink channel, applies power
scaling to the timing group or the component carrier determined as
the target of power scaling.
7. A base station apparatus that forms a cell in a radio
communication system where multiple cells are formed, the base
station apparatus comprising: a control section that controls
uplink transmission times per timing group including one component
carrier or a plurality of component carriers; and a transmission
section that signals a timing group or a component carrier
determined as a target of power scaling, as power scaling target
information, in which the timing group or the component carrier, to
which power scaling is applied, is expressly determined, to the a
user terminal, wherein the user terminal is connected to multiple
cells and controlled to different transmission times per timing
group.
8. A user terminal that connects to multiple cells in a radio
communication system where a plurality of base station apparatuses
form multiple cells, the user terminal comprising: a receiving
section that receives power scaling target information signaled
from the base station apparatus; a transmission section that
transmits uplink signals at different transmission times per timing
group; and a power control section that, when a total of uplink
signal transmission power over connecting cells exceeds a
predetermined value, applies power scaling to the timing group or
the component carrier determined in the power scaling target
information.
9. A radio communication method in a radio communication system
where multiple cells are formed, wherein: the radio communication
system comprises a plurality of base station apparatuses that each
form a cell included in the multiple cells, and a user terminal
that can connect to at least a first cell and a second cell
included in the multiple cells; and the radio communication method
comprises the steps of: controlling uplink transmission times per
timing group including one component carrier or a plurality of
component carriers; signaling a timing group or a component carrier
determined as a target of power scaling, as power scaling target
information, in which the timing group or the component carrier, to
which power scaling is applied, is expressly determined, to the
user terminal; in the user terminal, receiving the power scaling
target information signaled from the base station apparatus;
transmitting uplink signals at different transmission times per
timing group; and when a total of uplink signal transmission power
over multiple cells, to which the user terminal is connected at the
same time, exceeds a predetermined value, applying power scaling to
the timing group or the component carrier determined in the power
scaling target information.
Description
TECHNICAL FIELD
[0001] The present invention relates to a radio communication
system, a base station apparatus, a user terminal and a radio
communication method to carry out multi-carrier transmission with a
plurality of connecting cells at different times on the uplink.
BACKGROUND ART
[0002] LTE (Long Term Evolution) has been under study heretofore,
for the purposes of achieving improved spectral efficiency and peak
data rates, reducing delays and so on in UMTS (Universal Mobile
Telecommunications System) (non-patent literature 1). As a result
of this, in Release-8 LTE (hereinafter referred to as "Rel.
8-LTE"), as radio access schemes, a scheme that is based on
orthogonal frequency division multiplexing access (OFDMA) was
employed for the downlink, and a scheme that is based on
single-carrier frequency division multiple access (SC-FDMA) was
employed for the uplink. In Rel. 8-LTE, it is possible to achieve
transmission rates of approximately maximum 300 Mbps on the
downlink and 75 Mbps on the uplink, by using a variable band that
ranges from 1.4 MHz to 20 MHz. Presently, in 3GPP, successor
systems of LTE (referred to as "LTE advanced" ("LTE-A")) are under
study for the purpose of achieving further broadbandization and
faster speed beyond the UMTS network.
[0003] Recently, a study is progress to achieve increased network
capacity by building a heterogeneous network (HetNet), in which
low-power nodes (LPN) of low transmission power are overlaid in the
area of a macro cell, and applying carrier aggregation (CA) to the
HetNet. Carrier aggregation refers to the technique of achieving
broadbandization by using a frequency band (1.4 MHz to 20 MHz) that
is supported in LTE as one component carrier (CC) and using
multiple CCs at the same time. In the HetNet, it is possible to
realize efficient user terminal control, traffic off-loading and so
on, by changing the connecting cell to which a user terminal is
connected, on a per CC basis.
[0004] FIG. 1 shows, as an example, a state in which a user
terminal UE is connected with two cells of a base station apparatus
eNB (macro cell) and a low power node LPN (low power cell) in a
HetNet. The user terminal UE is allocated component carriers CC #1
and CC #2 by carrier aggregation, and connects with the macro cell
via component carrier CC #1 and connects with the low power cell
via component carrier CC #2. Since the low power node LPN 2 has a
small cell, the user terminal UE is located in a position closer to
the low power node LPN than to the base station apparatus eNB. In
Rel. 11-LTE, which is the latest standard of LTE-A, an MTA
(Multiple Timing Advance) function to make it possible to define a
plurality of transmission times for a plurality of CCs on the
uplink is introduced (up to Rel. 10, a user terminal is subject to
single-transmission time control (which is referred to as "TA" or
"single TA")), for the purpose of coordinating the times of
reception between separate nodes (base station apparatus, low power
node and so on). In the example shown in FIG. 1, the macro cell
carries out uplink transmission at a transmission time T1, and the
low power cell carries out uplink transmission at a transmission
time T2, which is a predetermined time delayed from transmission
time T1.
[0005] In LTE-A, carrier aggregation to use maximum five CCs is
realized. In MTA, which is introduced in Rel. 11-LTE, maximum five
CC are classified into maximum four TA groups (TAGs), and the times
of transmission are controlled on a per TAG basis.
[0006] As an example, FIG. 2 shows a state in which five CCs are
classified into four TAGs. Five of CC #1 to CC #5 are classified
into four of TAG #1 to TAG #4. TAG #1 is assigned to CC #1, one TAG
#2 is assigned to two of CC #2 and CC #3, TAG #3 is assigned to CC
#4, and TAG #4 is assigned to CC #5.
[0007] When the times of uplink transmission are controlled on a
per TAG basis in a user terminal UE where MTA is applied, as shown
in FIG. 3, the difference between the transmission times of the
TAGs may develop to approximately 30 .mu.s at a maximum. FIG. 3
shows a state in which the transmission times of TAG #1 and TAG #2
are, for example, 30 .mu.s different.
CITATION LIST
Non-Patent Literature
[0008] Non-Patent Literature 1: 3GPP, TR25.912 (V7.1.0),
"Feasibility Study for Evolved UTRA and UTRAN," September 2006
[0009] Non-Patent Literature 2: 3GPP, TS36.211 Sec. 8.1, "Timing
Advance"
SUMMARY OF THE INVENTION
Technical Problem
[0010] In the uplink in the LTE-A system, transmission power is
controlled in CC units and in subframe units, and is controlled so
that the total transmission power in each subframe does not exceed
an upper limit.
[0011] When the MTA function introduced in Rel. 11-LTE is applied
to a user terminal, there is a concern that parts (PO: Partial
Overlap) where subframes overlap between TAGs may be produced, and
there is also a possibility that the upper limit of transmission
power is exceeded in the PO periods. For example, even if, as shown
in FIG. 4, transmission power is controlled in subframe units, on a
per TAG basis, such that, when one TAG enters a high power subframe
period, the other TAG enters a low power subframe period, if a PO
period in which high power subframes overlap between the TAGs is
produced, the upper limit of transmission power is exceeded in the
PO period. So, when there is a possibility that the total
transmission power in a PO period exceeds the upper limit, it is
necessary to apply power scaling to the PO period or to the entire
subframe period, and reduce the total transmission power. When
"power scaling" is mentioned herein, this refers not only to
reducing power, but also covers cases where power is made zero.
[0012] However, when power scaling is applied to a PO period,
signal power decreases, and therefore a problem arises that uplink
transmission quality is deteriorated.
[0013] The present invention has been made in view of the above,
and it is therefore an object of the present invention to provide a
radio communication system, a user terminal, a base station
apparatus and a radio communication method whereby it is possible
to apply power scaling to PO periods while maintaining uplink
transmission quality.
Solution to Problem
[0014] The radio communication system according to the present
invention is a radio communication system, in which multiple cells
are formed, and which has a plurality of base station apparatuses
that each form a cell included in the multiple cells, and a user
terminal that can connect to at least a first cell and a second
cell included in the multiple cells, and, in this radio
communication system, the base station apparatuses has a control
section that controls uplink transmission times per timing group
including one component carrier or a plurality of component
carriers, and a transmission section that signals a timing group or
a component carrier determined as a target of power scaling, as
power scaling target information, in which the timing group or the
component carrier, to which power scaling is applied, is expressly
determined, to the user terminal, and the user terminal has a
receiving section that receives the power scaling target
information signaled from the base station apparatus, a
transmission section that transmits uplink signals at different
transmission times per timing group, and a power control section
that, when a total of uplink signal transmission power over the
first cell and the second cell exceeds a predetermined value,
applies power scaling to the timing group or the component carrier
determined in the power scaling target information.
[0015] The base station apparatus according to the present
invention is a base station apparatus that forms a cell in a radio
communication system where multiple cells are formed, and this base
station apparatus has a control section that controls uplink
transmission times per timing group including one component carrier
or a plurality of component carriers, and a transmission section
that signals a timing group or a component carrier determined as a
target of power scaling, as power scaling target information, in
which the timing group or the component carrier, to which power
scaling is applied, is expressly determined, to the a user
terminal, and the user terminal is connected to multiple cells and
controlled to different transmission times per timing group.
[0016] The user terminal according to the present invention is a
user terminal that connects to multiple cells in a radio
communication system where a plurality of base station apparatuses
form multiple cells, and this user terminal has a receiving section
that receives power scaling target information signaled from a base
station apparatus, a transmission section that transmits uplink
signals at different transmission times per timing group, and a
power control section that, when a total of uplink signal
transmission power over connecting cells exceeds a predetermined
value, applies power scaling to the timing group or the component
carrier determined in the power scaling target information.
[0017] The radio communication method according to the present
invention is a radio communication method in a radio communication
system where multiple cells are formed, and the radio communication
system has a plurality of base station apparatuses that each form a
cell included in the multiple cells, and a user terminal that can
connect to at least a first cell and a second cell included in the
multiple cells, and the radio communication method includes the
steps of controlling uplink transmission times per timing group
including one component carrier or a plurality of component
carriers, signaling a timing group or a component carrier
determined as a target of power scaling, as power scaling target
information, in which the timing group or the component carrier, to
which power scaling is applied, is expressly determined, to the
user terminal, in the user terminal, receiving the power scaling
target information signaled from the base station apparatus,
transmitting uplink signals at different transmission times per
timing group, and, when a total of uplink signal transmission power
over multiple cells, to which the user terminal is connected at the
same time, exceeds a predetermined value, applying power scaling to
the timing group or the component carrier determined in the power
scaling target information.
Technical Advantage of the Invention
[0018] According to the present invention, it is possible to apply
power scaling to periods in which uplink transmission power exceeds
an upper limit value, while maintaining uplink transmission
quality.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] FIG. 1 is a diagram to explain a HetNet;
[0020] FIG. 2 is a diagram to show the relationship between
component carriers and TAGs;
[0021] FIG. 3 is a diagram to show a state in which the time of
transmission is different between TAGs;
[0022] FIG. 4 is a diagram to show a PO period in which high power
subframes overlap between TAGs;
[0023] FIG. 5 is a diagram to explain an example of application of
power scaling;
[0024] FIG. 6 is a diagram to explain a system structure of a radio
communication system according to an embodiment;
[0025] FIG. 7 is a block diagram to show a schematic configuration
of a base station apparatus according to an embodiment;
[0026] FIG. 8 is a block diagram to show a configuration of a
baseband signal processing section in a base station apparatus;
[0027] FIG. 9 is a block diagram to show a schematic configuration
of a mobile terminal apparatus according to an embodiment;
[0028] FIG. 10 is a block diagram to show a configuration of a
baseband signal processing section in a mobile station apparatus;
and
[0029] FIG. 11 is a block diagram to show a configuration of a
layer 1 processing section in a baseband signal processing section
of a mobile station apparatus.
DESCRIPTION OF EMBODIMENTS
[0030] A gist of the present invention is that a base station
apparatus eNB expressly determines a TAG (or a cell, a CC, an
uplink physical channel, etc.), to which a user terminal UE should
apply power scaling preferentially, and signals power scaling
target information for specifying the TAG and/or the like, to which
power scaling is to be applied preferentially, to the user terminal
UE. By this means, it is possible to determine the TAG and/or the
like, to which the user terminal UE should apply power scaling, in
the base station apparatus eNB, so that it is possible to improve
the flexibility in network management. The base station apparatus
eNB can flexibly determine the TAG (or cell, CC, uplink physical
channel, etc.) to apply power scaling to, such that the
deterioration of uplink transmission quality is reduced, by taking
into account the communication environment (cell configurations,
the conditions of carrier aggregation, transmission quality,
traffic, transmission power, transport block size, and so on).
[0031] Now, the details will be described with reference to the
network configuration shown in FIG. 1. A user terminal UE is
connected with a macro cell (base station apparatus eNB), which
serves as a first cell, and is also connected with a low power cell
(low power node LPN), which serves as a second cell. It is not an
essential requirement of the present invention that the first cell
should be a macro cell and the second cell should be a low power
cell. The present invention by no means limits the number of cells
to which a user terminal can be connected at the same time to two
cells. The base station apparatus eNB and the low power node LPN
are connected via a backhaul link, and the base station apparatus
eNB controls the low power node LPN. The low power node LPN
receives information (for example, TAG information) that is
required for communication with user terminals UE from the base
station apparatus eNB via the backhaul link.
[0032] The base station apparatus eNB allocates a plurality of
component carriers CC #1 and CC #2 to the user terminal UE by
carrier aggregation, and also commands the cell configurations to
the user terminal UE so that one component carrier CC #1 is
allocated to the macro cell and the other component carrier CC #2
is allocated to the low power cell. When the cells are configured
such that the user terminal UE is assigned a plurality of component
carriers and is connected with a plurality of cells at the same
time, the base station apparatus eNB classifies the plurality of
component carriers assigned to the user terminal UE into TAGs, and
controls the times of transmission on a per TAG basis. In the
example shown in FIG. 1, CC #1 that is allocated to the macro cell
is classified as TAG #1, and CC #2 that is allocated to the low
power cell is classified as TAG #2.
[0033] The user terminal UE can transmit an uplink physical control
channel and an uplink physical data channel via a plurality of
component carriers CC #1 and CC #2. To be more specific, the user
terminal UE controls the time to transmit uplink subframes to
transmission time T1 in communication with the macro cell (TAG #1
and CC #1), and controls the time to transmit uplink subframes to
transmission time T2 in communication with the low power cell (TAG
#2 and CC #2). At this time, TAG #1 and TAG #2 offer different
times for uplink transmission (T1 and T2), and therefore a PO
period is produced (see FIG. 4).
[0034] The base station apparatus eNB expressly determines the TAG
to which power scaling is applied in the user terminal UE. For
example, in order to determine the TAG to apply power scaling to,
it may be possible to use transmission quality as a basis for
decision making. For example, although the deterioration of the
transmission quality of TAG #1 (CC #1) might cause severe
difficulties in radio communication, a communication environment
may be designed, in which the transmission quality of TAG #2 (CC
#2), even when deteriorated, can be recovered. In this case, the
base station apparatus eNB can determine TAG #2 (CC #2) as the TAG
to which power scaling is applied. Alternatively, it is also
possible to use traffic as a basis for decision making in order to
determine the TAG to apply power scaling to. For example, assume a
case where the traffic in TAG #1 (CC #1) is very low and the
traffic in TAG #2 (CC #2) is kept to a high value. In this case,
the base station apparatus eNB can determine TAG #1 (CC #1) as the
TAG to which power scaling is applied. By using transmission
quality and traffic as basis for decision making, it is possible to
apply power scaling to a PO period so that the deterioration of
uplink transmission quality can be reduced.
[0035] The base station apparatus eNB can also use the cell
configurations as a basis for decision making and expressly
determine the TAG where power scaling is applied in the user
terminal UE. Carrier aggregation refers to the kind of
communication by multiple cells using a plurality of component
carriers. It is also possible to define multiple cells (component
carriers) as two different types of cells by defining one cell as a
primary cell (Pcell) and the other cell as a secondary cell
(Scell). The base station apparatus eNB independently configures
the primary cell and the secondary cell for the user terminal UE
that adopts where carrier aggregation. The primary cell is always
formed with a set (combination) of one downlink component carrier
and one uplink component carrier. The secondary cell is formed with
at least one downlink component carrier, and there are cases where
an uplink component carrier is incorporated or not incorporated.
Here, the secondary cell is also formed with an uplink component
carrier.
[0036] A case will be assumed here where, in the HetNet shown in
FIG. 1, the primary cell (TAG #1 and CC #1) is managed for control
signals and the secondary cell (TAG #2 and CC #2) is managed for
data transmission. In Rel. 10-LTE, the following uplink physical
channel configurations are defined in component carrier units. As
uplink physical channels, a physical random access channel (PRACH),
a physical uplink control channel (PUCCH), a physical uplink shared
channel (PUSCH), and a channel quality measurement reference signal
(SRS: Sounding Reference Signal) are defined. The PRACH is used
when the user terminal makes initial access to the network. From
the downlink component carrier that is detected in cell search, the
user terminal receives, as broadcast information that is necessary,
the parameters of the PRACH (the frequency position, the subframe
position, the Zadoff-Chu sequence index and so on), information
about the uplink component carrier (the center frequency, the
bandwidth and so on), and so on, and transmits the PRACH using the
uplink component carrier that correspond to the downlink. The PUCCH
is multiplexed at both ends of the band (intra-subframe frequency
hopping is applied), and carries ACKs/NACKs, which are response
signals (responses) to downlink transmission signals, CQI (Channel
Quality Indicator) reports, scheduling requests and so on. CQI
refers to quality information that shows the quality of data as
received, or the quality of communication channels. The PUSCH is
mapped a UL-SCH (an uplink shared channel, which is one transport
channel).
[0037] The base station apparatus eNB expressly determines the cell
(the primary cell or the secondary cell) to apply power scaling to,
as an example of using cell configurations as a basis for decision
making. For example, when the first cell is managed for control
signals and the second cell is operated for data transmission and
the component carriers included in the first cell are classified as
the first timing group, and the component carriers included in the
second cell are classified as the second timing group, the base
station apparatus eNB expressly determines the physical uplink
control channel (PUCCH) of the first timing group, the physical
uplink shared channel (PUSCH) of the second timing group, and the
reference signal (SRS) for channel quality measurement, as physical
channels to apply power scaling to.
[0038] If the primary cell for control signals (TAG #1 and CC #1)
becomes the target of power scaling, the transmission power for the
control signal (PUCCH) in the primary cell (TAG #1 and CC #1)
decreases. If the secondary cell for data transmission (TAG #2 and
CC #2) becomes the target of power scaling, the transmission power
of the data signal (PUSCH) in the secondary cell decreases. Since
the cell to which power scaling is applied (the primary cell or the
secondary cell) is reported to the user terminal UE, it is possible
to apply power scaling to the control signal (PUCCH) or the data
signal (PUSCH) by signaling in cell units in the HetNet
environment.
[0039] The base station apparatus eNB may expressly determine the
cell to apply power scaling to, by linking physical channels with
the cells, as an example of using cell configurations as a basis
for decision making. To be more specific, if the primary cell for
control signals (TAG #1 and CC #1) becomes the target of power
scaling, the data signal (PUSCH) in the primary cell may be
determined to be subject to power scaling, and, similarly, if the
secondary cell for data transmission (TAG #2 and CC #2) becomes the
target of power scaling, the control signal (PUCCH) in the
secondary cell is may be determined to be subject to power scaling.
By this means, power scaling in physical channel units is made
possible by reporting the cell to apply power scaling to (the
primary cell or the secondary cell), to the user terminal UE.
[0040] The base station apparatus eNB expressly determines the
physical channels to apply power scaling to, in physical channel
units. For example, in the primary cell (TAG #1 and CC #1), it is
assumed that the transmission quality of the PRACH and the PUCCH is
prioritized over the PUSCH, and, in the secondary cell (TAG #2 and
CC #2), it is assumed that the transmission quality of the PUSCH
and the SRS is prioritized over the PUCCH. In this case, the base
station apparatus eNB expressly determines the PUSCH of TAG #1 (CC
#1) as the target to which apply power scaling is applied, and
expressly determines the PUCCH of TAG #2 (CC #2) as the target to
which power scaling is applied to.
[0041] The base station apparatus eNB reports the TAG (or the cell,
the CC, the uplink physical channel, etc.) to be the target of
power scaling, determined by one of the above-described methods, to
the user terminal UE by higher layer signaling. By this means, it
is possible to minimize the overhead, which increases by signaling
the TAG (or the cell, the CC, the uplink physical channel, etc.),
to which power scaling is applied.
[0042] The TAG (or the cell, the CC, the uplink physical channel,
the packet, etc.) to apply power scaling to is reported from the
base station apparatus eNB to the user terminal UE through the
downlink. In the state in which MTA is applied to the user
terminal, if the total transmission power exceeds the upper limit,
the user terminal UE applies power scaling to the TAG (or the cell,
the CC, the uplink physical channel, etc.) and reduces the
transmission power.
[0043] Assume that, in the state the user terminal UE is connected
to multiple cells, the TAG to apply power scaling to is reported.
In this case, if MTA is applied to the user terminal UE and the
total transmission power exceeds the upper limit in a PO period,
the transmission power of the CC that is included in the TAG
reported in advance is reduced.
[0044] Assume that, in the state in which the user terminal UE is
connected to the primary cell and the secondary cell, for example,
the primary cell (or the secondary cell) is reported as the cell to
which power scaling is applied. In this case, if MTA is applied to
the user terminal UE and the total transmission power exceeds the
upper limit in a PO period, the transmission power of the primary
cell (or the secondary cell) that is reported in advance is
reduced.
[0045] The user terminal UE may acquire information that links
physical channels with cells, in advance, and have the cell where
power scaling is applied reported from the base station apparatus
eNB. For example, assume that, when the primary cell for control
signals (TAG #1 and CC #1) becomes the target of power scaling, the
data signal (PUSCH) in the primary cell is determined to be subject
to power scaling. When the total transmission power exceeds the
upper limit in the PO period, if the primary cell (TAG #1 and CC
#1) is reported in advance as the target of power scaling, the user
terminal UE reduces the transmission power of the PUSCH of the
primary cell. Alternatively, assume that, when the secondary cell
for data transmission (TAG #2 and CC #2) becomes the target of
power scaling, the control signal (PUCCH) in the secondary cell is
determined to be subject to power scaling. When the total
transmission power exceeds the upper limit in the PO period, if the
secondary cell (TAG #2 and CC #2) is reported in advance as the
target of power scaling, the user terminal UE reduces the
transmission power of the PUCCH of the secondary cell.
[0046] When the base station apparatus eNB expressly determines the
PUSCH of TAG #1 (CC #1) as the target to apply power scaling to,
and expressly determines the PUCCH of TAG #2 (CC #2) as the target
to apply power scaling to, the user terminal UE has information
about the targets of power scaling determined in this way reported
from the base station apparatus eNB. In this case, when the total
transmission power in the PO period exceeds the upper limit, the
user terminal UE reduces the transmission power of the physical
channels that are reported in advance. For example, if the PUSCH of
TAG #1 (CC #1) is determined to be the target to apply power
scaling to, the transmission power of the PUSCH of TAG #1 (CC #1)
is reduced.
[0047] It is possible to combine the above-method of applying power
scaling with one of methods A and B, which will be shown below.
[0048] The power scaling method A applies power scaling on a per
physical channel basis based on the priority of each uplink
physical channel (PUSCH/PUCCH/PRACH/SRS). For example, the
priorities are determined such that:
PRACH>PUCCH>PUSCH>SRS.
[0049] The power scaling method B applies power scaling by
prioritizing the primary cell over the secondary cell.
[0050] Another aspect of the present invention provides a method of
maintaining transmission quality by implicitly determining the TAG
and/or the like, to which power scaling is applied, without
signaling. Specific power signaling methods (1) to (5) will be
described below.
[0051] (1) The user terminal UE may be configured to apply power
scaling to a TAG having large transmission power. By this means,
the probability that power scaling is applied to a TAG having low
transmission power decreases, and it is possible to prevent the
significant quality deterioration due to the severe reduction of
power to allocate to the TAG having low transmission power.
[0052] Assume a case where, in the state in which the user terminal
UE is connected to multiple cells, MTA to provide a plurality of
transmission times for a plurality of connecting cells on the
uplink is applied to the user terminal UE. TAG configurations (the
component carrier numbers, information corresponding to the TAG
numbers, and so on) related to the component carriers allocated by
the base station apparatus eNB is reported to the user terminal
UE.
[0053] As shown in FIG. 5, a plurality of component carriers,
allocated to the uplink of the user terminal UE, are classified to
TAG #1 and TAG #2. A state is shown here where the transmission
power of TAG #1 is greater than the transmission power of TAG #2 in
a stage before power scaling is applied.
[0054] When the total transmission power on the uplink exceeds the
upper limit in the PO period, the user terminal UE applies power
scaling to TAG #1 having the greater transmission power. As a
result of this, as shown in FIG. 5, the transmission power of TAG
#1 decreases, and the total transmission power is reduced to or
below the upper limit. At this time, the transmission power of TAG
#2, to which power scaling is not applied, is maintained.
[0055] (2) The user terminal UE may be configured to apply power
scaling to a PUSCH where the transport block size (the number of
transmission bits) is small. By this means, the small-sized
transport block can prevent quality deterioration by means of power
scaling, and reduce the overhead upon retransmissions, unlike
large-sized transport blocks that cause quality deterioration.
[0056] In LTE, data on an uplink transport channel (for example,
the UL-SCH) is incorporated into transport blocks of certain size.
In each subframe (transmission time interval: TTI), transport
blocks are transmitted on the radio interface between the user
terminal UE and the base station apparatus eNB. The transport
blocks are divided into codewords and transmitted by physical
channels. In the event of one-antenna transmission, one transport
block of variable size is transmitted on per TTI. In the event of
multiple-antenna transmission, maximum two transport blocks of
variable size are transmitted per TTI. The transport block size is
defined in the transport format that accompanies the transport
blocks. In the transport format, the modulation scheme and antenna
mapping are defined, besides the transport block size.
[0057] When the user terminal UE is connected to the first cell and
the second cell and the total transmission power on the uplink
exceeds the upper limit in the PO period, between the transport
block allocated to the PUSCH of the first cell and the transport
block allocated to the PUSCH of the second cell, the user terminal
UE applies power scaling to the PUSCH of the smaller transport
block size.
[0058] (3) The user terminal UE may be configured to apply power
scaling to a TAG where the total allocation bandwidth is small. By
this means, it is possible to reduce the frequency bandwidth to
consume.
[0059] One component carrier or a plurality of component carriers
are classified into one TAG, so that there is a possibility that
the total allocation bandwidth varies between TAGs. For example,
TAG #1 is allocated only one component carrier CC #1, and TAG #2 is
allocated two component carriers CC #2 and CC #3.
[0060] Assume a case where, in the state in which the user terminal
UE is connected to multiple cells, MTA to provide a plurality of
transmission times for a plurality of connecting cells on the
uplink is applied to the user terminal UE. TAG configurations (the
component carrier numbers, information corresponding to the TAG
numbers, and so on) related to the component carriers allocated by
the base station apparatus eNB is reported to the user terminal UE.
When the total transmission power on the uplink exceeds the upper
limit in the PO period, the user terminal UE applies power scaling
to TAG #1 where the total bandwidth is smaller.
[0061] (4) The user terminal UE may be configured to apply power
scaling to new uplink packets. By this means, although there is a
possibility that, when the transmission power of uplink
retransmission packets is reduced, reception errors occur again and
the delays accumulate, since the transmission power of new packets
is reduced, it is possible to minimize the delay time even if
retransmissions occur.
[0062] As noted earlier, in each uplink component carrier, uplink
channels such as the PUCCH, the PUSCH and so on are placed. The
user terminal UE transmits channel state information (CSI) that
represents downlink channel states, information that represents
ACKs/NACKs (positive acknowledgement/negative acknowledgement) in
hybrid ARQ in response to downlink transport blocks, uplink control
information (UCI) such as scheduling requests (SRs), to the base
station apparatus eNB, by using the PUCCH and/or the PUSCH.
[0063] In LTE, retransmissions of damaged/lost data or data that
has errors are first processed in MAC layer hybrid ARQ, and, if
recovery fails even by this processing, handled in the RLC
retransmission protocol. Hybrid ARQ is designed for the purpose of
allowing quick retransmissions, so that decoding process results
are fed back in response to every transmission. The base station
apparatus eNB and the user terminal UE each have a hybrid ARQ
entity, and each hybrid ARQ entity is comprised of the hybrid ARQ
process. On the receiving side, when a transport block intended for
the hybrid ARQ process is received, decoding of the block is tried,
and the result--that is, whether or not the block has been received
correctly--is reported to the transmitting side by way of an
ACK/NACK.
[0064] On the uplink, which subframes are retransmitted is always
known. In the event of FDD, a retransmission is carried out eight
subframes after a data transmission is tried. Whether or not
retransmission should be carried out on the uplink is controlled
based on new data indicators (NDIs) included in scheduling grants
for the uplink transmitted by the PDCCH. The new data indicators
are configured separately for each transport block to be
transmitted. The user terminal UE can decide whether or not to
transmit new packets based on the new data indicators included in
the PDCCH.
[0065] When the user terminal UE is connected with the first cell
and the second cell and the total transmission power on the uplink
exceeds the upper limit in the PO period, the user terminal UE
applies power scaling to new uplink packets and reduces the uplink
transmission power.
[0066] (5) The user terminal UE may be configured to apply power
scaling to retransmission packets. By this means, power scaling is
applied to retransmission packet more preferentially than new
packets, so that it is possible to reduce the probability of
retransmissions of new packets.
[0067] (6) It is also possible to combine one of methods (1) to (5)
above, with the power scaling methods A and B described earlier.
For example, when applying power scaling to TAGs having large
transmission power, the user terminal UE may apply power scaling on
a per uplink physical channel basis, in the order of priorities of:
PRACH>PUCCH>PUSCH>SRS. When applying power scaling to TAGs
having large transmission power, the user terminal UE may apply
power scaling by prioritizing Pcell over Scell.
[0068] Next, examples of the base station apparatus and the user
terminal, to which the radio communication method described above
is applied, will be described. Although a radio access system
designed for LTE and LTE-A will be described as an example, this by
no means limits application to other systems.
[0069] FIG. 6 is a network configuration diagram of a mobile
communication system where a radio communication method according
to an embodiment of the present invention is applied. The radio
communication system 1 is configured to include base station
apparatuses 20A and 20B, and a plurality of first and second mobile
station apparatuses 10A and 10B that communicate with these base
station apparatuses 20A and 20B. The base station apparatuses 20A
and 20B are connected with a higher station apparatus 30, and this
higher station apparatus 30 is connected with a core network 40.
The base station apparatuses 20A and 20B are connected with each
other by wire connection or by wireless connection. The first and
second mobile station apparatuses 10A and 10B can communicate with
the base station apparatuses 20A and 20B in cells C1 and C2. The
higher station apparatus 30 may be, for example, an access gateway
apparatus, a radio network controller (RNC), a mobility management
entity (MME) and so on, but is by no means limited to these.
[0070] Although the first and second mobile station apparatuses 10A
and 10B may be both LTE terminals and LTE-A terminals, the
following description will be given simply with respect to the
"mobile station apparatus 10," unless specified otherwise.
Although, for ease of explanation, the first and second mobile
station apparatuses 10A and 10B will be described to perform radio
communication with the base station apparatuses 20A and 20B, more
generally, it is also possible to use user equipment (UE), which
may cover both mobile terminal apparatuses and fixed terminal
apparatus.
[0071] In the radio communication system 1, as radio access
schemes, OFDMA (Orthogonal Frequency Division Multiple Access) is
adopted on the downlink, and SC-FDMA
(Single-Carrier-Frequency-Division Multiple Access) is adopted on
the uplink, but the uplink radio access scheme is not limited to
this. OFDMA is a multi-carrier transmission scheme to perform
communication by dividing a frequency band into a plurality of
narrow frequency bands (subcarriers) and mapping data to each
subcarrier. SC-FDMA is a single carrier transmission scheme to
reduce interference between terminals by dividing, per terminal,
the system band into bands formed with one or continuous resource
blocks, and allowing a plurality of terminals to use mutually
different bands.
[0072] Now, communication channels in evolved UTRA and UTRAN will
be described. On the downlink, a physical downlink shared channel
(PDSCH), which is used by each mobile station apparatus 10 on a
shared basis, and a physical downlink control channel, which is a
downlink control channel (PDCCH, or also referred to as a "downlink
L1/L2 control channel") are used. By the above physical downlink
shared channel, user data--that is, normal data signals--is
transmitted. Precoding information for uplink MIMO transmission,
information about the IDs of users that communicate using the
physical downlink shared channel and the users' data transport
formats (that is, downlink scheduling information), and information
about the IDs of users that communicate using the physical uplink
shared channel and information about the users' data transport
formats (that is, uplink scheduling grants) and so on are fed back
by means of the physical downlink shared channel.
[0073] On the downlink, broadcast channels such as the P-BCH
(Physical-Broadcast CHannel) and the D-BCH (Dynamic Broadcast
CHannel) are transmitted. Information that is transmitted by means
of the P-BCH includes MIBs (Master Information Blocks), and
information that is transmitted by means of the D-BCH includes SIBs
(System Information Blocks). The D-BCH is mapped to the PDSCH, and
transmitted from the base station apparatus 20 to the mobile
station apparatuses 10.
[0074] As for the uplink, a physical uplink shared channel (PUSCH),
which is used by each mobile station apparatus 10 on a shared
basis, and a physical uplink control channel (PUCCH), which is an
uplink control channel, are used. By means of the physical uplink
shared channel, user data--that is, normal data signals--is
transmitted. By means of the physical uplink control channel,
precoding information for downlink MIMO transmission, delivery
acknowledgment information for downlink shared channels, downlink
radio quality information (CQI) and so on are transmitted.
[0075] On the uplink, a physical random access channel (PRACH) for
initial access and so on is defined. The mobile terminal apparatus
10 is designed to transmit random access preambles to the base
station apparatus 20 in the PRACH.
[0076] An overall configuration of a base station apparatus
according to the present embodiment will be described with
reference to FIG. 7. The base station apparatuses 20A and 20B have
the same configuration and therefore will be described as the "base
station apparatus 20." The first and second mobile station
apparatuses 10A and 10B also have the same configuration and
therefore will be described as the "mobile station apparatus
10."
[0077] The base station apparatus 20 has a plurality of
transmitting/receiving antenna 202a, 202b . . . for MIMO
transmission, amplifying sections 204a, 204b . . . ,
transmitting/receiving sections 206a, 206b . . . , a baseband
signal processing section 208, a call processing section 210, and a
transmission path interface 212. The transmitting/receiving
antennas 202a and 202b . . . are, for example, eight antennas, and
the amplifying sections 204a, 204b . . . and the
transmitting/receiving sections 206a and 206b . . . are provided in
numbers to match the number of antennas.
[0078] User data that is transmitted from the base station
apparatus 20 to the mobile station apparatus 10 on the downlink is
input from the higher station apparatus 30 placed above the base
station apparatus 20--for example, the access gateway apparatus
30--into the baseband signal processing section 208, via the
transmission path interface 212.
[0079] The baseband signal processing section 208 performs a PDCP
layer process, division and coupling of user data, RLC (Radio Link
Control) layer transmission processes such as an RLC retransmission
control transmission process, MAC (Medium Access Control)
retransmission control, including, for example, an HARQ (Hybrid
Automatic Repeat reQuest) transmission process, scheduling,
transport format selection, channel coding, an inverse fast Fourier
transform (IFFT) process, and a precoding process, and transfers
the result to the transmitting/receiving sections 206a and 206b.
The signal of the physical downlink control channel is also
subjected to transmission processes such as channel coding and an
inverse fast Fourier transform, and then transferred to the
transmitting/receiving sections 206a and 206b.
[0080] The baseband signal processing section 208 feeds back
control information for communication in the cell to the mobile
station apparatus 10, through the broadcast channels mentioned
earlier. The control information for communication in the cell
includes, for example, the uplink or downlink system bandwidth,
resource block information allocated to the mobile station
apparatus 10, root sequence identification information (root
sequence index) for generating random access preamble signals in
the PRACH and so on.
[0081] Baseband signals that are pre-coded and output from the
baseband signal processing section 208 on a per antenna basis are
subjected to a frequency conversion process and converted into a
radio frequency band in the transmitting/receiving sections 206a
and 206b, and, after that, amplified in the amplifying sections
204a and 204b and transmitted from the transmitting/receiving
antennas 202a and 202b.
[0082] As for data to be transmitted from the mobile terminal
apparatus 10 to the radio base station apparatus 20 on the uplink,
radio frequency signals that are received in the
transmitting/receiving antennas 202a and 202b are amplified in the
amplifying sections 204a and 204b, converted into baseband signals
through frequency conversion in the transmitting/receiving sections
206a and 206b, and input in the baseband signal processing section
208.
[0083] The baseband signal processing section 208 applies, to the
user data included in the baseband signals received as input, an
FFT process, an IDFT process, error correction decoding, a MAC
retransmission control receiving process and RLC layer and PDCP
layer receiving processes, and transfers the result to the access
gateway apparatus 30 via the transmission path interface 212.
[0084] The call processing section 210 performs call processing
such as setting up and releasing communication channels, manages
the state of the base station apparatus 20, and manages the radio
resources.
[0085] A configuration of the baseband signal processing section
208 of the radio base station apparatus 20 according to the present
embodiment will be described with reference to FIG. 8. FIG. 8 is a
functional block diagram of the baseband signal processing section
208 in the radio base station apparatus 20 according to the present
embodiment. In FIG. 8, configurations such as a scheduler 234 and
others are also included for ease of explanation.
[0086] Reference signals (quality measurement reference signals)
included in received signals are input in a channel quality
measurement section 221. The channel quality measurement section
221 measures uplink channel quality information (CQI) based on the
received state of the reference signals received from the mobile
station apparatus 10. Received signals that are input in the
baseband signal processing section 208 have the cyclic prefixes
attached to the received signals removed in CP (Cyclic Prefix)
removing sections 222a and 222b, and, after that, converted into
frequency domain information through a Fourier transform in fast
Fourier transform sections 224a and 224b. Symbol synchronization
sections 223a and 223b estimate the synchronization time from the
reference signals included in the received signals, and report the
estimation result to the CP removing sections 222a and 222b.
[0087] The received signals, converted into frequency domain
information, are demapped in the frequency domain in the subcarrier
demapping sections 225a and 225b. The subcarrier demapping sections
225a and 225b perform the demapping in accordance with the mapping
in the mobile station apparatus 10. Here, among the received
signals received on the uplink, the received signal that is input
in the subcarrier demapping section 225b is comprised of two uplink
data codewords #2 and #3 combined. The frequency domain
equalization section 226 equalizes the received signals based on
channel estimation values provided from a channel estimation
section 227. The channel estimation section 227 estimates channel
states on a per component carrier basis from the reference signals
included in the received signals, and the frequency domain
equalization section 226 equalizes the received signals (codewords)
on a per component carrier basis.
[0088] The inverse discrete Fourier transform sections (IDFT) 228a,
228b and 228c apply an inverse discrete Fourier transform to the
received signal and converts the frequency domain signals back to
time domain signals. The data demodulation sections 229a, 229b and
229c and the data decoding sections 230a, 230b and 230c reconstruct
uplink user data based on the transport format of each component
carrier (the coding rate, the modulation scheme and so on). By this
means, the transmission data of codeword #1 corresponding to the
first transport block, the transmission data of codeword #2
corresponding to the second transport block, and the transmission
data of codeword #3 corresponding to the third transport block are
reconstructed.
[0089] The re-constructed transmission data of codewords #1, #2 and
#3 is output to a retransmission information channel selection
section 233. The retransmission information channel selection
section 233 determines whether or not it is necessary to retransmit
the transmission data of codewords #1, #2 and #3 (ACK/NACK). Then,
based on whether or not it is necessary to retransmit the
transmission data of codewords #1, #2 and #3,
retransmission-related information such as NDI information and RV
information is generated. The retransmission information channel
selection section 231 selects the channel (the PHICH or the PDCCH
(UL grants)) to transmit the retransmission information.
[0090] The scheduler 234 determines uplink and downlink resource
allocation information based on channel quality information (CQI)
given from the channel quality measurement section 221, and PMI
information and RI information given from a precoding weight/rank
selection section 235, which will be described later.
[0091] The precoding weight/rank selection section 235 determines
precoding weights (PMIs) for controlling the phase and/or amplitude
of transmission signals on a per antenna basis in the mobile
station apparatus 10, from the uplink received quality in the
resource blocks allocated to the mobile station apparatus 10, based
on the channel quality information (CQI) given from the channel
quality measurement section 221. The precoding weight/rank
selection section 235 determines the rank (RI), which represents
the number of space multiplexing layers in the uplink, based on the
channel quality information (CQI) given from the channel quality
measurement section 221.
[0092] An MCS selection section 236 selects the modulation
scheme/channel coding rate (MCS) based on the channel quality
information (CQI) given from the channel quality measurement
section 221.
[0093] A dedicated user data generating section 237 generates
dedicated downlink transmission data (dedicated user data) for each
mobile station apparatus 10, from user data that is input from the
higher station apparatus 30 such as the access gateway apparatus
30, in accordance with resource allocation information given from
the scheduler 234.
[0094] With the present embodiment, the dedicated user data
generating section 237 functions as a control section that
expressly indicates the TAG, to which power scaling should be
applied, to the mobile station apparatus 10, based on control
signals input from the higher station apparatus or information
given from the scheduler 234, and signals power scaling target
information such as the TAG to apply power scaling to, to the
mobile station apparatus 10. The target to apply power scaling to
is not limited to being provided in TAG units, but may also be
provided in component carrier units, in uplink physical channel
units, or in packet units.
[0095] For example, it is possible to use the transmission quality
and/or the traffic of the connecting cells where the mobile station
apparatus 10 is connected, as a basis for decision making. The
dedicated user data generating section 237 may expressly determine
the TAG, to which power scaling is applied in the mobile station
apparatus 10, by using cell configurations as a basis for decision
making. The dedicated user data generating section 237 may
expressly determine the uplink physical channels to apply power
scaling to, in physical channel units. For example, in the primary
cell (TAG #1 and CC #1), the transmission quality of the PRACH and
the PUCCH may be prioritized over the PUSCH, and, in the secondary
cell (TAG #2 and CC #2), the transmission quality of the PUSCH and
the SRS may be prioritized over the PUCCH. In this case, the base
station apparatus 20 expressly determines the PUSCH of TAG #1 (CC
#1) as the target to apply power scaling to, and expressly
determines the PUCCH of TAG #2 (CC #2) as the target to apply power
scaling to.
[0096] When cell C1 as the first cell is managed for control
signals and cell C2 as the second cell is managed for data
transmission, and the component carriers included in the first cell
C1 are classified as the first timing group and the component
carriers included in the second cell C2 are classified as the
second timing group, the PUCCH of the first timing group, the PUSCH
and/or the SRS of the second timing group are expressly determined
as physical channels to which power scaling is applied.
[0097] The dedicated user data generating section 237 generates
user data for reporting the TAG (or the cell, the CC, the uplink
physical channel, the packet, etc.), to which power scaling is
applied to, expressly determined by one of the above-described
methods, to the mobile station apparatus 10 by higher layer
signaling.
[0098] The UL grant information generating section 238 generates a
DCI format, which includes the above-described UL grant, based on
ACK/NACK information and retransmission-related information (NDI
information and RV information) given from the retransmission
information channel selection section 233, resource allocation
information given from the scheduler 234, PMI and RI information
given from precoding weight/rank selection section 233, and MCS
information given from the MCS selection section 236.
[0099] The PHICH signal generating section 239 generates the PHICH
signal, which includes a hybrid ARQ acknowledgement response for
showing whether or not a transport block needs to be retransmitted
to the mobile station apparatus 10, based on the ACK/NACK
information and retransmission-related information (NDI information
and RV information) given from the retransmission information
channel selection section 233.
[0100] The PDSCH signal generating section 240 generates the
downlink transmission data to actually transmit by the physical
downlink shard channel (PDSCH), based on the downlink transmission
data (dedicated user data) generated in the dedicated user data
generating section 237. The PDCCH signal generating section 241
generates the PDCCH signal to multiplex over the PDCCH based on the
DCI format including the UL grant, generated in the UL grant
information generating section 238.
[0101] The PHICH signal, the PDSCH signal and the PDCCH signal
generated in these PHICH signal generating section 239, PDSCH
signal generating section 240 and PDCCH signal generating section
241 are input in an OFDM modulation section 242. The OFDM
modulation section 242 applies an OFDM modulation process to two
sequences of signals including these PHICH signal, PDSCH signal and
PDCCH signal, and transmits the results to the
transmitting/receiving sections 206a and 206b.
[0102] In this way, the base station apparatus 20 expressly
indicates the TAG (or the CC, the uplink physical channel, the
packet, etc.), to which power scaling is applied, to the mobile
station apparatus 10, and signals power scaling target information
such as the TAG to apply power scaling to, to the mobile station
apparatus 10, by higher layer signaling. By this means, it becomes
possible to determine the TAG and/or the like, to which the mobile
station apparatus 10 should apply power scaling, in the base
station apparatus 20, so that it is possible to improve the
flexibility in network management. The base station apparatus 20
can flexibly determine the TAG (or the cell, the CC, the uplink
physical channel, the packet, etc.), to which power scaling should
be applied, by taking into account the communication environment
(the cell configurations, the conditions of carrier aggregation,
transmission quality, traffic, transmission power, transport block
size, packet type and so on), and reduce the deterioration of
uplink transmission quality due to application of power scaling.
Since power scaling target information is reported to the mobile
station apparatus 10 through higher layer signaling, it is also
possible to reduce the overhead.
[0103] Next, a configuration of a mobile station apparatus 10
according to the present embodiment will be described with
reference to FIG. 9. As shown in FIG. 9, the mobile station
apparatus 10 according to the present embodiment has two
transmitting/receiving antennas 102a and 102b for MIMO
transmission, amplifying sections 104a and 104b,
transmitting/receiving sections 106a and 106b, a baseband signal
processing section 108, and an application section 110.
[0104] As for downlink data, radio frequency signals that are
received in the two transmitting/receiving antennas 102a and 102b
are amplified in the amplifying sections 104a and 104b, and
converted into baseband signals through frequency conversion in the
transmitting/receiving sections 106a and 106b. The baseband signals
are subjected to an FFT process, error correction decoding, a
retransmission control receiving process and so on in the baseband
signal processing section 108. In this downlink data, downlink user
data is transferred to the application section 110. The application
section 110 performs processes related to higher layers above the
physical layer and the MAC layer. In the downlink data, broadcast
information is also transferred to the application section 110.
[0105] Uplink user data is input from the application section 110
to the baseband signal processing section 108. The baseband signal
processing section 108 performs a retransmission control (H-ARQ:
Hybrid ARQ) transmission process, channel coding, precoding, DFT
process, IFFT process and so on, and transfers the result to the
transmitting/receiving sections 106a and 106b. The baseband signals
output from the baseband signal processing section 108 are
subjected to a frequency conversion process and converted into a
radio frequency band in the transmitting/receiving sections 106a
and 106b, and, after that, amplified in the amplifying sections
104a and 104b and transmitted from the transmitting/receiving
antennas 102a and 102b.
[0106] FIG. 10 is a block diagram showing a configuration of the
baseband signal processing section 108. The baseband signal
processing section 108 is primarily formed with a layer 1
processing section 1081, a MAC processing section 1082, an RLC
processing section 1083, a transmission power setting section 1084,
a TPC command received processing section 1085 and a TPC command
format receiving processing section 1086.
[0107] The layer 1 processing section 1081 mainly performs
processes related to the physical layer. The layer 1 processing
section 1081, for example, applies processes such as channel
decoding, a discrete Fourier transform, frequency demapping, an
inverse Fourier transform and data demodulation to signals received
on the downlink. The layer 1 processing section 1081 performs
processes for signals to transmit on the downlink, including
channel coding, data modulation, frequency mapping and an inverse
fast Fourier transform (IFFT).
[0108] The MAC processing section 1082 performs, for the signals
received on the downlink, MAC layer retransmission control (hybrid
ARQ), an analysis of downlink scheduling information (specifying
the PDSCH transport format and specifying the PDSCH resource
blocks) and so on. The MAC processing section 1082 performs, for
the signals to transmit on the uplink, MAC retransmission control,
an analysis of uplink scheduling information (specifying the PUSCH
transport format and specifying the PUSCH resource blocks and so
on) and so on.
[0109] The RLC processing section 1043 performs, for packets
received on the downlink/packets to transmit on the uplink, packet
division, packet combining, RLC layer retransmission control, and
so on.
[0110] The TPC command receiving process section 1085 receives TPC
commands reported from the base station apparatus 20, and detects
the contents of the TPC commands. The TPC command receiving process
section 1085 detects the contents of the TPC commands based on TPC
command formats received in the TPC command format receiving
process section 1086. Information about the TPC commands is sent to
the transmission power setting section 1084.
[0111] The TPC command format receiving process section 1086
receives the signals of TPC command formats reported from the radio
base station apparatus. The TPC command format receiving process
section 1086 receives a TPC command format signal with an expanded
number of bits (for example, three bits) upon uplink MU-MIMO
transmission. When uplink MU-MIMO transmission is not carried out,
the TPC command format receiving process section 1086 receives the
TPC command format signal that is defined in the LTE system.
Information about the TPC command formats is sent to the
transmission power setting section 1084.
[0112] The transmission power setting section 1084 sets
transmission power using transmission power control information
(TPC command formats and TPC commands). To the mobile station
apparatus 10, the TAG (or the cell, the CC, the uplink physical
channel, the packet, etc.), to which power scaling is applied, is
reported from the base station apparatus 20 on the downlink. If, in
the state in which MTA is applied, the total transmission power
exceeds the upper limit value defined, the transmission power
setting section 1084 applies power scaling to the TAG (the cell,
the CC, the uplink physical channel or the packet) that is reported
in advance, and reduces the transmission power.
[0113] For example, assume that the TAG to apply power scaling to
is reported as the target of power scaling in the state in which
the mobile station apparatus 10 is connected with multiple cells C1
and C2. In this case, if MTA is applied to the mobile station
apparatus 10 and the total transmission power exceeds the upper
limit in the PO period (see FIG. 4), the transmission power setting
section 1084 reduces the transmission power of the CCs included in
the TAG reported in advance.
[0114] Assume that, in the state in which the mobile station
apparatus 10 is reported to cell C1 that serves as the primary cell
and to cell C2 that serves as the secondary cell, for example, the
primary cell is reported as the cell to which power scaling is
applied. In this case, if MTA is applied to the mobile station
apparatus 10 and the total transmission power exceeds the upper
limit in the PO period, the transmission power setting section 1084
reduce the transmission power of the primary cell that is reported
in advance.
[0115] The mobile station apparatus 10 may acquire information that
links physical channels with cells, in advance, and have the cell
where power scaling is applied reported from the base station
apparatus 20. For example, assume that, when the primary cell C1
for control signals (TAG #1 and CC #1) becomes the target of power
scaling, the data signal (PUSCH) in the primary cell C1 is
determined to be subject to power scaling. When the total
transmission power exceeds the upper limit in the PO period, if the
primary cell C1 (TAG #1 and CC #1) is reported in advance as the
target of power scaling, the mobile station apparatus 10 reduces
the transmission power of the PUSCH of the primary cell C1.
Alternatively, assume that, when the secondary cell for data
transmission (TAG #2 and CC #2) becomes the target of power
scaling, the control signal (PUCCH) in the secondary cell is
determined to be subject to power scaling. When the total
transmission power exceeds the upper limit in the PO period, if the
secondary cell (TAG #2 and CC #2) is reported in advance as the
target of power scaling, the user terminal UE reduces the
transmission power of the PUCCH of the secondary cell.
[0116] When the base station apparatus 20 expressly determines the
PUSCH of TAG #1 (CC #1) as the target to apply power scaling to,
and expressly determines the PUCCH of TAG #2 (CC #2) as the target
to apply power scaling to, the mobile station apparatus 10 has
information about these targets of power scaling determined in this
way reported from the base station apparatus 20. In this case, in
the mobile station apparatus 10, when the total transmission power
in the PO period exceeds the upper limit, the transmission power
setting section 1084 reduces the transmission power of the physical
channels that are reported in advance. For example, if the PUSCH of
TAG #1 (CC #1) is determined to be the target to apply power
scaling to, the transmission power of the PUSCH of TAG #1 (CC #1)
is reduced.
[0117] Alternatively, by implicitly determining the TAG, to which
power scaling is applied, even when the above power scaling methods
(1) to (5) to maintain transmission quality are applied, without
carrying out signaling, the transmission power setting section 1084
reduces the transmission power of the TAG (the cell, the CC, the
uplink physical channel, or the packet) by applying one of the
power scaling methods (1) to (5) described above, in the PO period
in which the total transmission power exceeds the upper limit.
[0118] For example, when power scaling is determined to be applied
to a TAG having large transmission power, the transmission power
setting section 1084 calculates the sum of transmission power per
TAG, and applies power scaling to the TAG of the largest
transmission power. At this time, signaling of power scaling target
information from the base station apparatus 20 is not
necessary.
[0119] When power scaling is determined to be applied to the PUSCH
of a small transport block size (with a small number of
transmission bits), for example, if transport blocks are allocated
to cell C1 and cell C2, the transmission power setting section 1084
reduces the transmission power of the cell where the transport
block of the larger size is allocated. By this means, it is
possible to reduce the overhead upon retransmissions. At this time,
signaling of power scaling target information from the base station
apparatus 20 is not necessary.
[0120] When power scaling is determined to be applied to a TAG
where the total allocation bandwidth is small, if CC #1 alone is
allocated to cell C1 and CC #2 and CC #3 are allocated to cell C2,
the transmission power setting section 1084 applies power scaling
to the TAG of cell C1.
[0121] When power scaling is determined to be applied to new uplink
packets, the transmission power setting section 1084 applies power
scaling to new packets in accordance with detection results in the
new data transmission/retransmission determining section 115. When
power scaling is determined to be applied to retransmission
packets, the transmission power setting section 1084 applies power
scaling to retransmission packets in accordance with detection
results in the new data transmission/retransmission determining
section 115. Whether the target packets to apply power scaling to
are new packets or retransmission packets on the uplink depends on
system management.
[0122] The configuration of the layer 1 processing section 1081 in
the baseband signal processing section 108 of the mobile station
apparatus 10 will be described with reference to FIG. 11. A shown
in this drawing, received signals output from the
transmitting/receiving sections 106a and 106b are demodulated in
the OFDM demodulation section 111. Of the downlink received signals
demodulated in the OFDM demodulation section 111, the PDSCH signal
is input in the downlink PDSCH decoding section 112, the PHICH
signal is input in the downlink PHICH decoding section 113, and the
PDCCH signal is input in the downlink PDCCH decoding section 114.
The downlink PDSCH decoding section 112 decodes the PDSCH signal,
and reconstructs the PDSCH transmission data. The downlink PHICH
decoding section 113 decodes the downlink PHICH signal. The
downlink PDCCH decoding section 114 decodes the PDCCH signal. DCI
format to include UL grants is included in the PDCCH signal. When
power scaling target information is signaled from the base station
apparatus 20 to the mobile station apparatus 10 through higher
layer signaling, the power scaling target information is included
in the transmission data that is given by decoding the PDSCH
signal.
[0123] When a hybrid ARQ acknowledgment response (ACK/NACK) is
included in the PHICH signal decoded in the downlink PHICH decoding
section 113, the new data transmission/retransmission determining
section 115 decides between a new data transmission or a
retransmission based on this hybrid ARQ acknowledgment response
(ACK/NACK). When a hybrid ARQ acknowledgement (ACK/NACK) is
included in the UL grant of the PDCCH signal, the new data
transmission/retransmission determining section 115 decides between
a new data transmission or a retransmission based on this hybrid
ARQ acknowledgment response (ACK/NACK). The determined results are
reported to a new transmission data buffer section 116 and a
retransmission data buffer section 117.
[0124] The new transmission data buffer section 116 buffers uplink
transmission data input from the application section 110. The
retransmission data buffer section 117 buffers transmission data
output from the new transmission data buffer section 116. When a
determined result to the effect of a new data transmission is
reported from the data new transmission/retransmission determining
section 115, uplink transmission data is generated from the
transmission data in the new transmission data buffer section 116.
When a determined result to the effect of a data retransmission is
reported from the data new transmission/retransmission determining
section 115, uplink transmission data is generated from the
transmission data in the retransmission data buffer section
117.
[0125] The uplink transmission data that is generated is input in a
serial-to-parallel conversion section, which is not illustrated. In
this serial-to-parallel conversion section, the uplink transmission
data is subjected to serial-to-parallel conversion and converted
into a number of codewords to match the uplink rank. The codewords
represent the coding unit in channel coding, and the number thereof
(the number of codewords) is determined uniquely from the rank
and/or the number of transmitting antennas. A case is shown here
where the number of codewords is determined to be three. The number
of codewords and the number of layers (rank) do not always become
equal. Uplink codeword #1 transmission data, uplink codeword #2
transmission data and uplink codeword #3 transmission data are
input in the data coding sections 118a, 118b and 118c.
[0126] The data coding section 118a encodes the uplink codeword #1
transmission data. The uplink codeword #1 transmission data encoded
in the data coding section 118a is modulated in the data modulation
section 119a, and multiplexed in the multiplexing section 120a,
and, after that, time sequence information having been subjected to
a discrete Fourier transform in the discrete Fourier transform
section (DFT) 121a is converted into frequency domain information.
The data coding section 118a and the data modulation section 119a
perform the coding and modulation processes of the uplink codeword
#1 transmission data based on MCS information from the downlink
PDCCH decoding section 114. The subcarrier mapping section 112a
performs frequency domain mapping based on scheduling information
(resource allocation information) from the downlink PDCCH decoding
section 114. In the data coding sections 118b and 118c to the
subcarrier mapping sections 122b and 122c, the same processes are
applied to uplink codewords #2 and #3 as those applied to uplink
codeword #1.
[0127] Then, with the uplink codeword #1 transmission data after
the mapping, the transmission signals are subjected to an inverse
fast Fourier transform in the inverse fast Fourier transform
sections (IFFT) 123a, 123b and 123c, and converted from frequency
domain signals to time domain signals. Then, in cyclic prefix (CP)
attaching sections 124a, 124b and 124c, cyclic prefixes are
attached to the transmission signals. Here, the cyclic prefixes
function as guard intervals for cancelling multipath propagation
delays and differences in the times of reception between a
plurality of users in the base station apparatus 20.
[0128] Assume that CC #1 is allocated to cell C1, two CC #2 and CC
#3 are allocated to cell C2, CC #1 is classified as TAG #1, and CC
#2 and CC #3 are classified as TAG #2. Assume that MTA is applied
to the mobile station apparatus 10 that is connected to cell C1 and
cell C2, TAG #1 is set at transmission time T1, and TAG #2 is set
at transmission time T2. With the present embodiment, uplink data
(codeword #1) is transmitted on the uplink of cell C1, and uplink
data (codewords #2 and #3) is transmitted on the uplink of cell
C2.
[0129] Under the above circumstances, for the transmission signal
(codeword #1) of the uplink data of cell C1, the transmission time
is controlled to time T1 in the MTA processing section 125a. For
the transmission signal (codeword #2) of the uplink data of cell
C2, the transmission time is controlled to time T2 in the MTA
processing section 125b, and, for the transmission signal (codeword
#3), the transmission time is controlled to time T2 in the MTA
processing section 125c. The transmission signal (codeword #2) and
the transmission signal (codeword #3), which are the uplink data of
cell C2, are both controlled to time T2, and furthermore combined
in a combiner 126.
[0130] In this way, the TAG and/or the like, to which the mobile
station apparatus 10 should apply power scaling, are expressly
determined in the base station apparatus 20 and signaled, so that
the mobile station apparatus 10 is able to apply power scaling to
the power scaling target that is reported. As a result of this, it
is possible to apply power scaling to the power scaling target,
which the base station apparatus 20 determines taking into account
the communication environment (cell configurations, the conditions
of carrier aggregation, transmission quality, traffic, transmission
power, transport block size, packet type and so on), so that it is
possible to reduce the deterioration of uplink transmission quality
due to application of power scaling.
[0131] Although the present invention has been described in detail
with reference to the above embodiment, it should be obvious to a
person skilled in the art that the present invention is by no means
limited to the embodiment described herein. The present invention
can be implemented with various corrections and in various
modifications, without departing from the spirit and scope of the
present invention defined by the recitations of the claims.
Consequently, the descriptions herein are provided only for the
purpose of explaining examples, and should by no means be construed
to limit the present invention in any way.
[0132] The disclosure of Japanese Patent Application No.
2012-218198, filed on Sep. 28, 2012, including the specification,
drawings and abstract, is incorporated herein by reference in its
entirety.
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