U.S. patent application number 11/121028 was filed with the patent office on 2005-09-08 for base station apparatus and radio communication method.
This patent application is currently assigned to MATSUSHITA ELECTRIC INDUSTRIAL CO., LTD.. Invention is credited to Hiramatsu, Katsuhiko, Hoshino, Masayuki, Miya, Kazuyuki, Miyoshi, Kenichi, Uehara, Toshiyuki.
Application Number | 20050197161 11/121028 |
Document ID | / |
Family ID | 26608021 |
Filed Date | 2005-09-08 |
United States Patent
Application |
20050197161 |
Kind Code |
A1 |
Uehara, Toshiyuki ; et
al. |
September 8, 2005 |
Base station apparatus and radio communication method
Abstract
A base station transmits downlink signals to mobile terminals of
users A to C with respective transmission power corresponding to
downlink quality. A downlink quality estimating section (106) uses
the transmission power from a transmission power control section to
compare transmission power between the users, and estimates that a
terminal with low transmission power has high downlink quality. The
priorities are determined so that the priority is increased as the
transmission power is lower. Thus determined priority information
is output to a scheduling section (107). The scheduling section
(107) performs scheduling based on the priority information. The
section (107) assigns DSCH to terminals in ascending order of
transmission power. User A is first assigned DSCH, user B is second
assigned DSCH, and user C is third assigned DSCH. It is thus
possible to perform scheduling and MCS selection of DSCH with the
need of information from a terminal eliminated.
Inventors: |
Uehara, Toshiyuki;
(Yokosuka-shi, JP) ; Hiramatsu, Katsuhiko;
(Yokosuka-shi, JP) ; Miyoshi, Kenichi;
(Yokohama-shi, JP) ; Miya, Kazuyuki;
(Kawasaki-shi, JP) ; Hoshino, Masayuki;
(Yokosuka-shi, JP) |
Correspondence
Address: |
STEVENS, DAVIS, MILLER & MOSHER, LLP
1615 L. STREET N.W.
SUITE 850
WASHINGTON
DC
20036
US
|
Assignee: |
MATSUSHITA ELECTRIC INDUSTRIAL CO.,
LTD.
Osaka
JP
|
Family ID: |
26608021 |
Appl. No.: |
11/121028 |
Filed: |
May 4, 2005 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
11121028 |
May 4, 2005 |
|
|
|
10204221 |
Aug 19, 2002 |
|
|
|
6909881 |
|
|
|
|
10204221 |
Aug 19, 2002 |
|
|
|
PCT/JP02/00329 |
Jan 18, 2002 |
|
|
|
Current U.S.
Class: |
455/561 |
Current CPC
Class: |
H04W 72/14 20130101;
H04L 1/0015 20130101; H04W 52/40 20130101; H04W 52/24 20130101;
H04L 1/0032 20130101; H04W 84/04 20130101; H04L 1/0034 20130101;
H04W 28/14 20130101; H04L 1/0009 20130101; H04W 72/085
20130101 |
Class at
Publication: |
455/561 |
International
Class: |
H04B 007/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 19, 2001 |
JP |
2001/012451 |
Feb 16, 2001 |
JP |
2001/040413 |
Claims
1-12. (canceled)
13. A base station apparatus comprising: a monitoring section that
is adapted to measure, for each of a plurality of communication
terminals, transmission power of a dedicated channel associated
with a shared channel which is shared by the plurality of
communication terminals; a selection section that is adapted to
select a modulation scheme and a coding rate of the shared channel
based on the result of the measurement in the monitoring section; a
coding section that is adapted to code a signal using the selected
coding rate; and a modulation section that is adapted to modulate
the signal using the selected modulation scheme.
14. The based station apparatus according to claim 13, wherein the
dedicated channel is DPCH (dedicated physical channel) and the
shared channel is SDCH (downlink shared channel).
15. The base station apparatus according to claim 13, further
comprising: a scheduling section that is adapted to perform
scheduling for the shared channel based on the result of the
measurement in the monitoring section.
16. The base station apparatus according to claim 13, further
comprising: a transmission power control section that is adapted to
correct the transmission power of the dedicated channel using
information obtained by upper layer signaling.
17. A MCS (modulation and coding scheme) selection method in a
mobile communication system said method comprising: (a) measuring,
for each of a plurality of communication terminals, transmission
power of a dedicated channel associated with a shared channel which
is shared by the plurality of communication terminals; (b)
selecting a modulation scheme and a coding rate of the shared
channel based on the result of the measurement in the step (a); (c)
coding a signal using the selected coding rate; and (d) modulating
the signal using the selected modulation scheme.
Description
TECHNICAL FIELD
[0001] The present invention relates to a base station apparatus
and radio transmission method used in a digital radio communication
system, in particular, in a CDMA (Code Division Multiple Access)
system.
BACKGROUND ART
[0002] In recent years, introduction of a shared channel such as
DSCH (Downlink Shared CHannel) used by a plurality of communication
terminals (users) has been studied to transmit a large amount of
packet data over the downlink. For example, when transmission is
performed using DSCH, on a dedicated channel, each user transmits
control data, performs transmission power control and maintains
synchronization, while receiving information indicating a
transmitted DSCH signal is to the user and information on
transmission rate of DSCH signal.
[0003] In DSCH transmission, scheduling as to determine users and
their priority to transmission data is performed corresponding to
the downlink quality. For example, a base station monitors downlink
qualities for all the users under control of the base station, and
preferentially assigns DSCH to users providing higher quality. A
terminal obtains CIR (Carrier to Interference Ratio) based on a
CPICH (Common PIlot CHannel) signal, and notifies the base station
of the CIR information, whereby the base station is capable of
monitoring the downlink quality.
[0004] Further, selection of MCS (Modulation and Coding Scheme) is
performed corresponding to the downlink quality. Also in this case,
a terminal obtains CIR based on a CPICH signal, and notifies the
base station of the CIR information, whereby the base station is
capable of selecting a scheme.
[0005] However, when performing the scheduling and MCS selection
based on CIR obtained from a CPICH signal in a terminal, the
terminal should notify CIR. It is thus necessary for the terminal
to always transmit CIR for the scheduling and MCS selection.
Therefore, a problem arises that information to be transmitted
using uplink signals is increased.
DISCLOSURE OF INVENTION
[0006] It is an object of the present invention to provide a base
station apparatus and radio transmission method enabling scheduling
and MCS selection of DSCH to be performed with the need of
information from a terminal side eliminated.
[0007] The object is achieved by performing scheduling and MCS
selection of DSCH using transmission power of DPCH or DPCCH that a
transmit side is capable of monitoring, and thereby eliminating the
need of information from the terminal side in performing the
scheduling and MCS selection of DSCH.
BRIEF DESCRIPTION OF DRAWINGS
[0008] FIG. 1 is a block diagram showing a configuration of a base
station apparatus according to Embodiment 1 of the present
invention;
[0009] FIG. 2 is a diagram showing a slot configuration of a
downlink signal;
[0010] FIG. 3A is a diagram showing a case that a base station
transmits signals using DSCH;
[0011] FIG. 3B is another diagram showing a case that a base
station transmits signals using DSCH;
[0012] FIG. 3C is another diagram showing a case that abase station
transmits signals using DSCH;
[0013] FIG. 4 is a diagram to explain DSCH scheduling;
[0014] FIG. 5 is a block diagram showing a configuration of a
transmission power monitoring section in a base station apparatus
according to Embodiment 2 of the present invention;
[0015] FIG. 6 is a diagram showing a slot configuration of a
downlink signal;
[0016] FIG. 7 is a block diagram showing a configuration of a base
station apparatus according to Embodiment 3 of the present
invention;
[0017] FIG. 8 is a view showing a table used in MCS selection;
[0018] FIG. 9 is a block diagram showing a configuration of a base
station apparatus according to Embodiment 4 of the present
invention;
[0019] FIG. 10 is a block diagram showing a configuration of a base
station apparatus according to Embodiment 5 of the present
invention;
[0020] FIG. 11 is a block diagram showing a configuration of a base
station apparatus according to Embodiment 6 of the present
invention; and
[0021] FIG. 12 is a view showing a correspondence table in the base
station apparatus according to Embodiment 6 if the present
invention.
BEST MODE FOR CARRYING OUT THE INVENTION
[0022] Embodiments of the present invention will be described below
with reference to accompanying drawings.
[0023] A base station apparatus naturally knows transmission power
used in transmitting signals to a terminal apparatus communicating
with the base station apparatus. The transmission power is of
parameter to estimate the downlink quality. In other words, the
transmission power is low when the downlink quality is high, while
being high when the downlink quality is low. The transmission power
is controlled by transmission power control so as to maintain the
reception quality at a constant level. The inventor of the present
invention noted this point, found out that scheduling and MCS
selection of DSCH can be performed with the need of information
from a terminal side eliminated by using transmission power of DPCH
(Dedicated Physical Channel) in performing the scheduling and MCS
selection of DSCH performed with the downlink quality estimated,
and carried out the present invention.
[0024] That is, it is a gist of the present invention to perform
scheduling and MCS selection of DSCH using transmission power of
DPCH or DPCCH that a transmit side is capable of monitoring, and
thereby eliminates the need of information from a terminal side in
performing scheduling and MCS selection of DSCH.
[0025] Embodiments of the present invention will be described below
specifically with reference to accompanying drawings.
Embodiment 1
[0026] This embodiment explains a case of performing DSCH
scheduling using transmission power of DPCH accompanying DSCH.
Specifically, a case will be described that DSCH is preferentially
assigned to a user with low DPCH transmission power (high downlink
quality).
[0027] FIG. 1 is a block diagram showing a configuration of a base
station apparatus according to Embodiment 1 of the present
invention. For simplified explanation, FIG. 1 shows a single
transmit-section sequence and a single reception-section
sequence.
[0028] An uplink signal transmitted from a terminal apparatus as a
communicating party is received in radio reception section 102 via
antenna 101. Radio reception section 102 performs predetermined
radio reception processing (for example, downconverting and A/D
conversion) on the uplink signal. The signal subjected to the radio
reception processing is output to despreading section 103.
Despreading section 103 performs despreading on the signal
subjected to the radio reception processing using a spreading code
used in spreading in the terminal apparatus. The despread signal is
output to demodulation section 104.
[0029] Demodulation section 104 performs demodulation processing
(for example, coherent detection and RAKE combining) on the
despread signal, and obtains received data. Further, a TPC command
is extracted in the demodulation processing in demodulation section
104. The TPC command is output to transmission power control
section 105.
[0030] Downlink quality estimating section 106 monitors
transmission power for each of all the terminals under control of
the base station, assigns priorities to users in ascending order of
transmission power, and outputs priority information to scheduling
section 107. Based on the priority information from downlink
quality estimating section 106, scheduling section 107 performs
scheduling to determine users assigned DSCH. The scheduling
information determined in scheduling section 107 is output to frame
configuring section 108.
[0031] Based on the scheduling information, frame configuring
section 108 configures a frame using transmission data, and outputs
a signal with a frame configuration to modulation section 109.
Modulation section 109 performs digital modulation on the signal
with the frame configuration, and outputs the modulated signal to
spreading section 110.
[0032] Spreading section 110 performs spreading on the modulated
signal using a spreading code, and outputs the spread signal to
radio transmission section 111. Radio transmission section 111
performs predetermined transmission processing (for example, D/A
conversion and upconverting) on the spread signal. The signal
subjected to the radio transmission processing is transmitted to a
terminal apparatus as a downlink signal via antenna 101.
[0033] The scheduling operation in the base station apparatus with
the above configuration will be described below. Herein, a case
will be described that there are three terminal apparatuses, i.e.,
three users (user A, user B and user C) under control of the base
station.
[0034] The base station (BS) transmits downlink signals to mobile
terminals (MS) of users A to C with respective transmission power
corresponding to downlink quality. Downlink quality estimating
section 106 monitors the transmission power of a slot in
transmission power control section 105, compares transmission power
between the users, and estimates that a terminal with low
transmission power has high downlink quality. Then, the section 106
determines priorities so that the priority is increased as the
transmission power is lower. As shown in FIG. 2, with a one-slot
period set as a transmission power monitoring period as shown in
FIG. 2, the transmission power is obtained by calculating an
average value of transmission power of the transmission power
monitoring period (DPCCH (Dedicated Physical Control CHannel) and
DPDCH (Dedicated Physical Data CHannel)). Thus determined priority
information is output to scheduling section 107.
[0035] Scheduling section 107 performs scheduling based on the
priority information. In other words, the section 107 assigns DSCH
to terminals in ascending order of transmission power (in
descending order of downlink quality). Herein, since the
transmission power to user A is the lowest, the transmission power
to user B is second lowest, and the transmission power to user C is
third lowest,
[0036] it is estimated that the downlink quality is higher in the
order of user C to A. Therefore, as shown in FIG. 4, user A is
first assigned DSCH, user B is second assigned DSCH, and user C is
third assigned DSCH.
[0037] In addition, in scheduling it may be possible to assign DSCH
to users in another order corresponding to transmission power,
instead of assigning starting from a user with low transmission
power and high quality. The another order is not limited
particularly, and for example, it may be possible to determine the
priority using service and data rate.
[0038] Then, according to the scheduling, DSCH signals are
transmitted. In other words, as shown in FIG. 3A DSCH signals are
first transmitted to user A, next as shown in FIG. 3B, transmitted
to user B, and then as shown in FIG. 3C, transmitted to user C.
Further, with respect to DSCH transmission, as mentioned above, it
may be possible to transmit signals on DSCH separately according to
priority or to a plurality of terminals to share.
[0039] In DSCH scheduling, when the scheduling is once determined,
it may be possible to newly perform scheduling after completing the
DSCH transmission according to the scheduling, or to update a
result of scheduling for each slot because the transmission power
is monitored for each slot. By updating a result of scheduling
while monitoring the transmission power of a predetermined period,
it is possible to estimate the downlink quality with accuracy even
when propagation environments vary due to the effect of fading, and
to perform DSCH assignment more suitably.
[0040] On DPCH, each of users A to C transmits control data,
performs transmission power control, and maintains synchronization,
while receiving information indicating a transmitted DSCH signal is
to the user and information on transmission rate of the DSCH
signal. Then, the terminal receives the DPCH signal to determine
whether a DSCH signal is to the terminal, and when the signal is to
the terminal, interprets DSCH transmission rate information from
the DPCH signal to receive and demodulate signals transmitted on
DSCH.
[0041] Thus, according to this embodiment, since it is possible to
perform DSCH scheduling using transmission power of DPCH that can
be monitored at a side of a base station, DSCH scheduling is
performed with the need of information from a side of a terminal
eliminated.
[0042] This embodiment explains the case where downlink quality
estimating section 106 determines a priority to each terminal based
on transmission power, and based on the determined priority
information, scheduling section 107 performs the scheduling.
However, it may be possible in this embodiment that downlink
quality estimating section 106 monitors transmission power to each
terminal, and associates the monitored transmission power with each
terminal to output to scheduling section 107, and based on the
information, scheduling section 107 performs the scheduling.
Embodiment 2
[0043] As shown in FIG. 2, on DPCH are timewise multiplexed DPDCH
for transmitting data (DATA 1 and DATA 2) and DPCCH for
transmitting control data (TPC (Transmission Power control), TFCI
(Transport Format Combination Indicator) and PL (Pilot)). The
transmission power of DPDCH varies corresponding to data rate,
while the transmission power of DPCCH is constant not depending on
the data rate. Therefore, when transmission power of a single slot
is obtained using DPDCH and DPCCH, it is considered that the
transmission power of a single slot differs for each slot due to
variations in data rate of DPDCH. In addition, the transmission
power of DPDCH and DPCCH is controlled by transmission power
control so that the reception quality is constant.
[0044] Accordingly, this embodiment explains a case of performing
DSCH scheduling using transmission power f DPCCH that is constant
independent of data rate.
[0045] FIG. 5 is a block diagram showing a configuration of a
transmission power monitoring section in a base station apparatus
according to Embodiment 2 of the present invention. The other
structural sections in the base station apparatus having the
transmission power monitoring section shown in FIG. 5 are the same
as in the base station apparatus shown in FIG. 1.
[0046] Downlink quality estimating section 106 has DPCCH detecting
section 1061 that detects a period of DPCCH, and DPCCH power
calculating section 1062 that calculates transmission power of a
single DPCCH slot detected in DPCCH detecting section 1061.
[0047] The scheduling operation in the base station apparatus with
the above configuration will be described below. Herein, a case
will be described that there are three terminal apparatuses, i.e.,
three users (user A, user B and user C) under control of the base
station.
[0048] The base station transmits downlink signals to the terminals
of users A to C with respective transmission power corresponding to
downlink quality. Downlink quality estimating section 106 monitors
the transmission power of a slot in transmission power control
section 105, compares the transmission power between the users, and
estimates that a terminal with low transmission power has high
downlink quality. Then, the section 106 determines priorities so
that the priority is increased as the transmission power is
lower.
[0049] Herein, as shown in FIG. 6, a period of DPCCH in one slot is
set as a transmission power monitoring period, and the transmission
power is obtained from the transmission power of the transmission
power monitoring period (DPCCH).
[0050] Specifically, DPCCH detecting section 1061 detects the DPCCH
period, and outputs the transmission power of the detected DPCCH
period for each terminal to DPCCH power calculating section 1062.
DPCCH power calculating section 1062 calculates the transmission
power of the DPCCH period when necessary, compares the transmission
power between the users, and estimates that a terminal with low
transmission power has high downlink quality. Then, the section
1062 determines priorities so that the priority is increased as the
transmission power is lower. Thus determined priority information
is output to scheduling section 107.
[0051] In addition, DPCCH power calculating section 1062 executes
calculation when necessary, instead of executing general
transmission power calculation. For example, a case sometimes
happens that the transmission power varies for each symbol when
M-ary modulation is used as a modulation scheme, and in such a
case, the average transmission power may be calculated. Further,
the transmission power is calculated when scheduling section 107
obtains desired parameters using the transmission power in the
scheduling.
[0052] Scheduling section 107 performs scheduling based on the
priority information. In other words, the section 107 assigns DSCH
to terminals in ascending order of transmission power (in
descending order of downlink quality). Herein, since the
transmission power to user A is the lowest, the transmission power
to user B is second lowest, and the transmission power to user C is
third lowest, it is estimated that the downlink quality is higher
in the order of user C to A. Therefore, as shown in FIG. 4, user A
is first assigned DSCH, user B is second assigned DSCH, and user C
is third assigned DSCH.
[0053] In addition, in scheduling it may be possible to assign DSCH
to users in another order corresponding to transmission power,
instead of assigning starting from a user with low transmission
power and high quality. The another order is not limited
particularly, and for example, it may be possible to determine the
priority using service and data rate.
[0054] Then, according to the scheduling, DSCH signals are
transmitted. In other words, as shown in FIG. 3A DSCH signals are
first transmitted to user A, next as shown in FIG. 3B, transmitted
to user B, and then as shown in FIG. 3C, transmitted to user C.
Further, with respect to DSCH transmission, as mentioned above, it
may be possible to transmit signals on DSCH separately according to
priority or to a plurality of terminals to share.
[0055] In DSCH scheduling, when the scheduling is once determined,
it may be possible to newly perform scheduling after completing the
DSCH transmission according to the scheduling, or update a result
of scheduling for each slot because the transmission power is
monitored for each slot. By updating a result of scheduling while
monitoring the transmission power of a predetermined period, it is
possible to estimate downlink quality with accuracy even when
propagation environments vary due to the effect of fading, and to
perform DSCH assignment more suitably.
[0056] Thus, according to this embodiment, since it is possible to
perform DSCH scheduling using transmission power of DPCCH that can
be monitored at a side of a base station, DSCH scheduling is
performed with the need of information from a side of a terminal
eliminated. Further according to this embodiment, since the
scheduling is performed using the transmission power of DPCCH that
is constant independent of data rate, it is possible to estimate
the downlink quality with more accuracy, and to perform DSCH
assignment suitably.
Embodiment 3
[0057] This embodiment explains a case of performing MCS selection
of DSCH using transmission power of DPCH or transmission power of
DPCCH accompanying DSCH. Specifically, a case will be described
that MCS selection of DSCH is performed corresponding to
transmission power level of DPCH.
[0058] FIG. 7 is a block diagram showing a configuration of a base
station apparatus according to Embodiment 3 of the present
invention. In FIG. 7, the same sections as in FIG. 1 are assigned
the same reference numerals as in FIG. 1 to omit specific
descriptions thereof.
[0059] The base station apparatus shown in FIG. 7 is provided with
MCS selecting section 701, instead of scheduling section 107.
Downlink quality estimating section 106 monitors transmission power
for each of all the terminals under control of the base station,
and outputs transmission power levels for each terminal to MCS
selecting section 701. Based on the transmission power levels from
downlink quality estimating section 106, MCS selecting section 701
performs MCS selection of DSCH. MCS selected in MCS selecting
section 701 is outputs to coding section 702 and modulation section
109.
[0060] Coding section 702 performs coding on transmission data
according to a coding rate of MCS selected in MCS selecting section
701. A coded signal is output to modulation section 109. Modulation
section 109 performs digital modulation on the coded signal
according to a modulation scheme of MCS selected in MCS selecting
section 701, and outputs the modulated signal to spreading section
110.
[0061] MCS selecting section 701 selects MCS using the transmission
power level output from downlink quality estimating section 106,
for example, by comparing the level with a threshold. For example,
MCS selecting section 701 compares a transmission power level with
thresholds (herein, seven thresholds are provided), and selects MCS
referring to a table associating MCS with the transmission power as
shown in FIG. 8 with respect to a result of determination with the
thresholds. Herein, the MCS number is associated with a range of
transmission power level, and when a range of transmission power
level is specified by the determination with the thresholds, the
MCS number is specified using the table. For the MCS numbers,
respective modulation schemes and coding rates are predetermined,
and therefore, specifying the MCS number specifies a modulation
scheme and coding rate. In addition, as long as MCS is selected
corresponding to transmission power, the number of thresholds in
the determination and a structure of the table are not limited to
the above description.
[0062] As described above, MCS is selected for each terminal, and
signals are processed according to modulation schemes and coding
rates selected for each terminal and assigned to DSCH, thereby
performing the downlink transmission. DSCH transmission is the same
as in Embodiment 1.
[0063] Thus, according to this embodiment, since it is possible to
perform MCS selection of DSCH using the transmission power of DPCH
that can be monitored at a side of a base station, it is possible
to perform MCS selection of DSCH without the need of information
from a side of a terminal eliminated.
[0064] In addition, as in Embodiment 2, downlink quality estimating
section 106 may be composed of DPCCH detecting section 1061 that
detects a period of DPCCH, and DPCCH power calculating section 1062
that calculates transmission power of a single DPCCH slot detected
in DPCCH detecting section 1061. In other words, as shown in FIG.
6, it may be possible that a period of DPCCH in one slot is set as
a transmission power monitoring period, and that the transmission
power is obtained from the transmission power of the transmission
power monitoring period (DPCCH).
[0065] Specifically, DPCCH detecting section 1061 detects the DPCCH
period, and outputs the transmission power of the detected DPCCH
period for each terminal to DPCCH power calculating section 1062.
DPCCH power calculating section 1062 averages the transmission
power of the DPCCH period, and outputs the averaged transmission
power to MCS selecting section 701.
[0066] In this way, since MCS selection of DSCH is performed using
the transmission power of DPCCH that is constant independent of
data rate, it is possible to estimate the downlink quality with
more accuracy, and to perform MCS selection of DSCH suitably.
[0067] This embodiment explains the case where MCS selecting
section 701 makes a determination with thresholds based on the
transmission power from downlink quality estimating section 106 to
select MCS. However, it may be possible in this embodiment that
downlink quality estimating section 106 monitors transmission power
to each terminal, compares the monitored transmission power with a
threshold, and outputs the determination result to MCS selecting
section 701, and based on the determination result, MCS selecting
section 701 selects MCS.
Embodiment 4
[0068] This embodiment explains a case of performing scheduling and
MCS selection of DSCH using transmission power of DPCH accompanying
DSCH or transmission power of DPCH. Specifically, a case will be
described that MCS selection of DSCH is performed corresponding to
transmission power level of DPCH or DPCCH.
[0069] FIG. 9 is a block diagram showing a configuration of a base
station apparatus according to Embodiment 4 of the present
invention. In FIG. 9, the same sections as in FIG. 1 are assigned
the same reference numerals as in FIG. 1 to omit specific
descriptions thereof.
[0070] The base station apparatus shown in FIG. 9 is provided with
MCS selecting section 701 in addition to scheduling section 107.
Downlink quality estimating section 106 monitors transmission power
for each of all the terminals under control of the base station,
assigns priorities to users in ascending order of transmission
power, and outputs priority information to scheduling section 107.
Based on the priority information from downlink quality estimating
section 106, scheduling section 107 performs scheduling to
determine users assigned DSCH. The scheduling information
determined in scheduling section 107 is output to frame configuring
section 108.
[0071] Based on the scheduling information, frame configuring
section 108 configures a frame using transmission data, and outputs
a signal with a frame configuration to modulation section 109.
Modulation section 109 performs digital modulation on the signal
with the frame configuration, and outputs the modulated signal to
spreading section 110.
[0072] Further, downlink quality estimating section 106 outputs the
monitored transmission power levels for each terminal to MCS
selecting section 701. Based on the transmission power levels from
downlink quality estimating section 106, MCS selecting section 701
performs MCS selection of DSCH. MCS selected in MCS selecting
section 701 is output to coding section 702 and modulation section
109.
[0073] Coding section 702 performs coding on the transmission data
according to a coding rate of MCS selected in MCS selecting section
701. A coded signal is output to modulation section 109. Modulation
section 109 performs digital modulation on the coded signal
according to a modulation scheme of MCS selected in MCS selecting
section 701, and outputs the modulated signal to spreading section
110.
[0074] MCS selecting section 701 selects MCS using the transmission
power level output from downlink quality estimating section 106,
for example, by comparing the level with a threshold. For example,
MCS selecting section 701 compares a transmission power level with
thresholds (herein, seven thresholds are provided), and selects MCS
referring to a table associating MCS with the transmission power as
shown in FIG. 8 with respect to a result of determination with the
thresholds. Herein, the MCS number is associated with a range of
transmission power level, and when a range of transmission power
level is specified by the determination with the thresholds, the
MCS number is specified using the table. For the MCS numbers,
respective modulation schemes and coding rates are predetermined,
and therefore, specifying the MCS number specifies a modulation
scheme and coding rate. In addition, as long as MCS is selected
corresponding to transmission power, the number of thresholds in
the determination and a structure of the table are not limited to
the above description. Further, it may be possible to calculate
using DSP or the like every time instead of using a table.
[0075] As described above, the scheduling is performed, MCS is
selected for each terminal, and signals are processed according to
modulation schemes and coding rates selected for each terminal and
assigned to DSCH according to the scheduling, thereby performing
the downlink transmission. DSCH transmission is the same as in
Embodiment 1.
[0076] Thus, according to this embodiment, since it is possible to
perform scheduling and MCS selection of DSCH using the transmission
power of DPCH that can be monitored at a side of a base station, it
is possible to perform scheduling and MCS selection of DSCH with
the need of information from a side of a terminal eliminated.
[0077] In addition, as in Embodiment 2, downlink quality estimating
section 106 may be composed of DPCCH detecting section 1061 that
detects a period of DPCCH, and DPCCH power calculating section 1062
that calculates transmission power of a single DPCCH slot detected
in DPCCH detecting section 1061. In other words, as shown in FIG.
6, it may be possible that a period of DPCCH in one slot is set as
a transmission power monitoring period, and that the transmission
power of the transmission power monitoring period (DPCCH) is
obtained (averaged when necessary).
[0078] Specifically, DPCCH detecting section 1061 detects the DPCCH
period. Since the numbers of chips of control data (TPC, TFCI and
PL) are predetermined, when a head of a slot is once identified,
the transmission power monitoring period can be obtained readily.
The section 1061 outputs the transmission power of the detected
DPCCH period for each terminal to DPCCH power calculating section
1062. DPCCH power calculating section 1062 calculates the
transmission power of the DPCCH period when necessary, compares the
transmission power between the users, and estimates that a terminal
with low transmission power has high downlink quality. Then, the
section 1062 determines priorities so that the priority is
increased as the transmission power is lower. Thus determined
priority information is output to scheduling section 107. Further,
the averaged transmission power is output to MCS selecting section
701.
[0079] In addition, in scheduling it may be possible to assign DSCH
to users in another order corresponding to transmission power,
instead of assigning starting from a user with low transmission
power and high quality. The another order is not limited
particularly, and for example, it may be possible to determine the
priority using service and data rate.
[0080] In this way, since MCS selection of DSCH is performed using
the transmission power of DPCCH that is constant independent of
data rate, it is possible to estimate the downlink quality with
more accuracy, and to perform the scheduling and MCS selection of
DSCH suitably.
[0081] This embodiment explains the case where downlink quality
estimating section 106 determines a priority to each terminal based
on transmission power, and based on the determined priority
information, scheduling section 107 performs the scheduling.
However, it may be possible in this embodiment that downlink
quality estimating section 106 monitors transmission power to each
terminal, and associates the monitored transmission power with each
terminal to output to scheduling section 107, and based on the
information, scheduling section 107 performs the scheduling.
[0082] This embodiment explains the case where MCS selecting
section 701 makes a determination with thresholds based on the
transmission power from downlink quality estimating section 106 to
select MCS. However, it may be possible in this embodiment that
downlink quality estimating section 106 monitors transmission power
to each terminal, compares the monitored transmission power with a
threshold, and outputs the determination result to MCS selecting
section 701, and based on the determination result, MCS selecting
section 701 selects MCS.
Embodiment 5
[0083] During a soft handover, a communication terminal combines
signals transmitted from a plurality of base stations, and based on
the combined signal, generates a transmission power control bit so
as to satisfy required quality, thereby performing transmission
power control using the transmission power control bit.
[0084] It is assumed that a communication terminal is connected
with base station (A), has moved and is connected on DPCH with
another base station (B) in soft handover. It is further assumed
that the communication quality between the communication terminal
and base station (B) is lower than that between the communication
terminal and base station (A). In such a state, the TPC bit error
tends to occur in transmission between the communication terminal
and base station (B).
[0085] When the TPC bit error thus occurs, the transmission power
in base station (B) differs. Since the transmission power control
is performed while combining signals from both base stations during
the soft handover, the difference of the transmission power in base
station (B) does not affect much. However, in such a state, when
the communication quality between the communication terminal and
base station (B) becomes higher than that between the communication
terminal and base station (A) and the communication terminal starts
communicating on DSCH with base station (B), it is not possible to
perform scheduling and MCS determination accurately because the
transmission power of base station (B) differs.
[0086] Then, this embodiment explains a case of performing
scheduling and MCS determination on DSCH more accurately based on
the transmission power subjected to transmission power adjustment
using a technique such as Adjustment Loop performed during a soft
handover. In addition, this embodiment explains a configuration for
performing both scheduling and MCS determination on DSCH based on
the transmission power subjected to transmission power adjustment.
However, a configuration may be possible which performs only either
scheduling or MCS determination based on the transmission power
subjected to transmission power adjustment.
[0087] FIG. 10 is a block diagram showing a configuration of a base
station apparatus according to Embodiment 5 of the present
invention. In FIG. 10, the same sections as in FIG. 9 are assigned
the same reference numerals as in FIG. 9 to omit specific
descriptions thereof.
[0088] The base station apparatus shown in FIG. 10 is provided with
downlink quality estimating section 106 that estimates the downlink
quality using the transmission power of a current control unit
calculated in transmission power controlling section 105 using the
transmission power of a last control unit, transmission power
control information of a last control unit, reference power
notified from an upper layer, transmission power balance, etc. The
control unit includes a slot or frame per which basis the control
is performed.
[0089] In the base station apparatus with the above configuration,
transmission power control section 105 outputs transmission power
control bit of a last control unit to downlink quality estimating
section 106. Transmission power control section 105 outputs the
transmission power of the last control unit to downlink quality
estimating section 106. Further, reference power PREF and
transmission power balance Pbalmax is notified (by signaling) to
transmission power control section 105 from an upper layer.
[0090] Transmission power control section 105 calculates the
transmission power of the current control unit with following
equations (1) and (2), using the transmission power of the last
control unit, transmission power control information of the last
control unit, reference power P.sub.REF, and transmission power
balance P.sub.balmax:
P(i+1)=P(i)P.sub.TPC(i)+P.sub.bal(i) Eq.(1)
P.sub.bal(i)=sign{(1-r)(P.sub.REF-P(i))}.times.min{.vertline.(1-r)(P.sub.R-
EF-P(i)).vertline., P.sub.balmax} Eq.(2)
[0091] where P.sub.REF indicates the reference power, and
P.sub.balmax indicates a maximum value of transmission power
balance Pbal(k).
[0092] In equation (1), an increase or decrease in transmission
power control is added to the transmission power of the last
control unit, and the transmission power balance is increased or
decreased, thereby balancing with the reference power. In other
words, the transmission power is corrected using P.sub.REF and
P.sub.balmax notified by the upper layer signaling.
[0093] Transmission power control section 105 corrects transmission
power for each of the terminals under control of the base station
to calculate, and outputs the corrected transmission power to
downlink quality estimating section 106. Downlink quality
estimating section 106 assigns priorities to users in ascending
order of transmission power, and outputs priority information to
scheduling section 107. Based on the priority information from
downlink quality estimating section 106, scheduling section 107
performs scheduling to determine users assigned DSCH. The
scheduling information determined in scheduling section 107 is
output to frame configuring section 108.
[0094] Based on the scheduling information, frame configuring
section 108 configures a frame using transmission data, and outputs
a signal with a frame configuration to modulation section 109.
Modulation section 109 performs digital modulation on the signal
with the frame configuration, and outputs the modulated signal to
spreading section 110.
[0095] Further, downlink quality estimating section 106 outputs the
transmission power levels for each terminal to MCS selecting
section 701. Based on the transmission power levels from downlink
quality estimating section 106, MCS selecting section 701 performs
MCS selection of DSCH. MCS selected in MCS selecting section 701 is
output to coding section 702 and modulation section 109.
[0096] Coding section 702 performs coding on the transmission data
according to a coding rate of MCS selected in MCS selecting section
701. A coded signal is output to modulation section 109. Modulation
section 109 performs digital modulation on the coded signal
according to a modulation scheme of MCS selected in MCS selecting
section 701, and outputs the modulated signal to spreading section
110. MCS selecting section 701 selects MCS using the transmission
power level output from downlink quality estimating section 106,
for example, by comparing the level with a threshold as in
Embodiments 3 and 4.
[0097] As described above, the scheduling is performed, MCS is
selected for each terminal, and signals are processed according to
modulation schemes and coding rates selected for each terminal and
assigned to DSCH according to the scheduling, thereby performing
the downlink transmission. DSCH transmission is the same as in
Embodiment 1.
[0098] Thus, according to this embodiment, it is possible to
control the transmission power while compensating for a difference,
occurring during a soft handover, of the transmission power of
downlink signals from each base station and preventing the
difference from increasing. Since the scheduling and MCS selection
of DSCH is performed using thus controlled transmission power, it
is possible to perform scheduling and MCS selection of DSCH with
accuracy.
[0099] In addition, as in Embodiment 2, downlink quality estimating
section 106 may be composed of DPCCH detecting section 1061 that
detects a period of DPCCH, and DPCCH power calculating section 1062
that calculates transmission power of a single DPCCH slot detected
in DPCCH detecting section 1061. In other words, as shown in FIG.
6, it may be possible that a period of DPCCH in one slot is set as
a transmission power monitoring period, and that the transmission
power of the transmission power monitoring period (DPCCH) is
obtained (averaged when necessary).
[0100] Specifically, DPCCH detecting section 1061 detects the DPCCH
period. Since the numbers of chips of control data (TPC, TFCI and
PL) are predetermined, when a head of a slot is once identified,
the transmission power monitoring period can be obtained readily.
The section 1061 outputs the transmission power of the detected
DPCCH period for each terminal to DPCCH power calculating section
1062. DPCCH power calculating section 1062 calculates the
transmission power of the DPCCH period when necessary, compares the
transmission power between the users, and estimates that a terminal
with low transmission power has high downlink quality. Then, the
section 1062 determines priorities so that the priority is
increased as the transmission power is lower. Thus determined
priority information is output to scheduling section 107. Further,
the averaged transmission power is output to MCS selecting section
701.
[0101] In addition, in scheduling it may be possible to assign DSCH
to users in another order corresponding to transmission power,
instead of assigning starting from a user with low transmission
power and high quality. The another order is not limited
particularly, and for example, it may be possible to determine the
priority using service and data rate.
[0102] In this way, since MCS selection of DSCH is performed using
the transmission power of DPCCH that is constant independent of
data rate, it is possible to estimate the downlink quality with
more accuracy, and to perform scheduling and MCS selection of DSCH
suitably.
[0103] This embodiment explains the case where downlink quality
estimating section 106 determines a priority to each terminal based
on transmission power, and based on the determined priority
information, scheduling section 107 performs the scheduling.
However, it may be possible in this embodiment that downlink
quality estimating section 106 estimates the downlink quality of
each terminal, and outputs the estimated information for each
terminal to scheduling section 107, and based on the information,
scheduling section 107 performs the scheduling.
[0104] This embodiment explains the case where MCS selecting
section 701 makes a determination with thresholds based on the
transmission power from downlink quality estimating section 106 to
select MCS. However, it may be possible in this embodiment that
downlink quality estimating section 106 calculates transmission
power to each terminal, compares the calculated transmission power
with a threshold, and outputs the determination result to MCS
selecting section 701, and based on the determination result, MCS
selecting section 701 selects MCS.
[0105] In addition, the calculation in downlink quality estimating
section 106 is not limited to the case of using reference power as
described above. A method may be possible of correcting the
transmission power based on the information notified by upper layer
signaling or from a communication terminal.
Embodiment 6
[0106] During a soft handover, a communication terminal receives
signals transmitted from a plurality of base stations to combine,
and based on the combined signal, generates a transmission power
control bit so as to satisfy required quality, thereby performing
transmission power control using the transmission power control
bit.
[0107] Accordingly, during a soft handover, the required quality is
satisfied from signals transmitted from a plurality of base
stations. In such a state, when performing scheduling and MCS
determination on DSCH based on the transmission power from only one
base station, it is not possible to accurately perform scheduling
and MCS determination on DSCH.
[0108] Then, this embodiment explains a case where during a soft
handover, the upper layer signaling includes the number of
connected base stations, the downlink quality is estimated using
the transmission power and margin corresponding to the number, and
based on the estimated result, the scheduling and MCS determination
on DSCH is performed.
[0109] FIG. 11 is a block diagram showing a configuration of a base
station apparatus according to Embodiment 6 of the present
invention. In FIG. 11, the same sections as in FIG. 9 are assigned
the same reference numerals as in FIG. 9 to omit specific
descriptions thereof.
[0110] The base station apparatus shown in FIG. 11 is provided with
downlink quality estimating section 106 that calculates
transmission power of a current control unit using the information
on the number of connected base stations notified from an upper
layer. The control unit includes a slot or frame per which basis
the control is performed.
[0111] In the base station apparatus with the above configuration,
the information on the number of connected base stations is
notified to downlink quality estimating section 106 from an upper
layer (by signaling). Downlink quality estimating section 106
calculates transmission power to estimate the downlink quality (or
downlink quality (for example, CIR) estimated using the
transmission power) using the margin corresponding to the number of
connected base stations. The margin is obtained referring to a
correspondence table shown in FIG. 12. The information targeted for
the upper layer signaling is not limited to the information on the
number of connected base stations, as long as the information
enables a base station that transmits DSCH signals to recognize
(estimate) a degree of contribution of the base station to the
received quality on the combined DPCH signal.
[0112] For example, when there are two connected base stations,
downlink quality estimating section 106 calculates the transmission
power corresponding to the margin of 3 dB referring to the
correspondence table in FIG. 12. In other words, since there are
two connected base stations, the base station assumes that the
required quality is satisfied in a communication terminal by
transmission power twice that of the base station, and as a margin,
adds 3 dB corresponding to twice the transmission power, and
estimates the downlink quality. Then, based on the estimated
result, the base station performs the scheduling and MCS
determination on DSCH.
[0113] Further, when there are three connected base stations,
downlink quality estimating section 106 calculates the transmission
power corresponding to the margin of 4.8 dB referring to the
correspondence table in FIG. 12. In other words, since there are
three connected base stations, the base station assumes that the
required quality is satisfied in a communication terminal by
transmission power three times that of the base station, and as a
margin, adds 4.8 dB corresponding to three times the transmission
power, and calculates the transmission power. Then, based on the
transmission power, the base station performs the scheduling and
MCS determination on DSCH.
[0114] Downlink quality estimating section 106 estimates the
downlink quality for each of all the terminals under control of the
base station, assigns priorities to users in ascending order of
transmission power, and outputs priority information to scheduling
section 107. Based on the priority information from downlink
quality estimating section 106, scheduling section 107 performs
scheduling to determine users assigned DSCH. The scheduling
information determined in scheduling section 107 is output to frame
configuring section 108.
[0115] Based on the scheduling information, frame configuring
section 108 configures a frame using transmission data, and outputs
a signal with a frame configuration to modulation section 109.
Modulation section 109 performs digital modulation on the signal
with the frame configuration, and outputs the modulated signal to
spreading section 110.
[0116] Further, downlink quality estimating section 106 outputs the
transmission power levels for each terminal to MCS selecting
section 701. Based on the transmission power levels from downlink
quality estimating section 106, MCS selecting section 701 performs
MCS selection of DSCH. MCS selected in MCS selecting section 701 is
output to coding section 702 and modulation section 109.
[0117] Coding section 702 performs coding on the transmission data
according to a coding rate of MCS selected in MCS selecting section
701. A coded signal is output to modulation section 109. Modulation
section 109 performs digital modulation on the coded signal
according to a modulation scheme of MCS selected in MCS selecting
section 701, and outputs the modulated signal to spreading section
110. MCS selecting section 701 selects MCS using the transmission
power level output from downlink quality estimating section 106,
for example, by comparing the level with a threshold as in
Embodiments 3 and 4.
[0118] As described above, the scheduling is performed, MCS is
selected for each terminal, and signals are processed according to
modulation schemes and coding rates selected for each terminal and
assigned to DSCH according to the scheduling, thereby performing
the downlink transmission. DSCH transmission is the same as in
Embodiment 1.
[0119] Thus, according to this embodiment, the transmission power
is controlled with the number of connected base stations considered
in a during handover. Since the scheduling and MCS selection of
DSCH is performed using thus calculated transmission power, it is
possible to perform scheduling and MCS selection of DSCH with
accuracy.
[0120] In addition, as in Embodiment 2, downlink quality estimating
section 106 may be composed of DPCCH detecting section 1061 that
detects a period of DPCCH, and DPCCH power calculating section 1062
that calculates transmission power of a single DPCCH slot detected
in DPCCH detecting section 1061. In other words, as shown in FIG.
6, it may be possible that a period of DPCCH in one slot is set as
a transmission power monitoring period, and that the transmission
power of the transmission power monitoring period (DPCCH) is
obtained (averaged when necessary).
[0121] Specifically, DPCCH detecting section 1061 detects the DPCCH
period. Since the numbers of chips of control data (TPC, TFCI and
PL) are predetermined, when a head of a slot is once identified,
the transmission power monitoring period can be obtained readily.
The section 1061 outputs the transmission power of the detected
DPCCH period for each terminal to DPCCH power calculating section
1062. DPCCH power calculating section 1062 calculates the
transmission power of the DPCCH period when necessary, compares the
transmission power between the users, and estimates that a terminal
with low transmission power has high downlink quality. Then, the
section 1062 determines priorities so that the priority is
increased as the transmission power is lower. Thus determined
priority information is output to scheduling section 107. Further,
the averaged transmission power is output to MCS selecting section
701.
[0122] In addition, in scheduling it may be possible to assign DSCH
to users in another order corresponding to transmission power,
instead of assigning starting from a user with low transmission
power and high quality. The another order is not limited
particularly, and for example, it may be possible to determine the
priority using service and data rate.
[0123] In this way, since MCS selection of DSCH is performed using
the transmission power of DPCCH that is constant independent of
data rate, it is possible to estimate the downlink quality with
more accuracy, and to perform scheduling and MCS selection of DSCH
suitably.
[0124] This embodiment explains the case where downlink quality
estimating section 106 determines a priority to each terminal based
on transmission power, and based on the determined priority
information, scheduling section 107 performs the scheduling.
However, it may be possible in this embodiment that downlink
quality estimating section 106 calculates transmission power to
each terminal, and associates the calculated transmission power
with each terminal to output to scheduling section 107, and based
on the information, scheduling section 107 performs the
scheduling.
[0125] This embodiment explains the case where MCS selecting
section 701 makes a determination with thresholds based on the
transmission power from downlink quality estimating section 106 to
select MCS. However, it may be possible in this embodiment that
downlink quality estimating section 106 calculates transmission
power to each terminal, compares the calculated transmission power
with a threshold, and outputs the determination result to MCS
selecting section 701, and based on the determination result, MCS
selecting section 701 selects MCS.
[0126] In addition, the method of calculating a margin with the
number of connected base stations considered is not limited to the
above case, and is capable of being carried out with various
modifications thereof. Further, values of margin are not limited to
this embodiment.
[0127] Moreover, while this embodiment explains the case of using
the information on the number of connected base stations notified
by the upper layer signaling, in the present invention the
information on the number of connected base stations may be
obtained from a terminal apparatus. The information to calculate
the margin is not limited to information on the number of connected
base stations, as long as the information enables the margin to be
calculated. Examples of the information include a ratio of power of
a base station that transmit DSCH signals to power of all the base
stations to be connected on DPCH.
[0128] Above-mentioned embodiments 1 to 6 are capable of being
carried into practice in a combination thereof as appropriate. The
present invention is not limited to the above-mentioned
embodiments, and is capable of being carried into practice with
various modifications thereof. For example, each of the
above-mentioned embodiments explains the case of performing
scheduling and MCS selection of DSCH using the transmission power
of DPCH or DPCCH. However, the present invention is applicable to a
case of performing scheduling and MCS selection of DSCH using the
transmission power of a dedicated channel besides DPCH.
[0129] Each of the above-mentioned embodiments explains the case of
three users with which the base station communicates. However, the
present invention is similarly applicable to a case of three or
more users.
[0130] While each of the above-mentioned embodiments explains the
case of using transmission power of a slot for scheduling and MCS
selection of DSCH, the present invention is similarly applicable to
a case of using transmission power of a period longer than a slot
for scheduling and MCS selection of DSCH.
[0131] Each of the above-mentioned embodiments explains the case of
performing scheduling and MCS selection of DSCH using the
transmission power of DPCH or DPCCH. However, in the present
invention it may be possible to execute processing other than the
scheduling and MCS selection using the transmission power of DPCH
or DPCCH as long as the processing is executed while estimating the
downlink quality.
[0132] While each of above-mentioned embodiments explains the case
of performing scheduling and MCS determination using the
transmission power, in the present invention it may be possible to
perform the scheduling and MCS determination using the downlink
quality (for example, CIR) estimated using the transmission power.
Also in such a case, it is possible to obtain the same effect as in
the present invention.
[0133] Each of above-mentioned embodiments explains the case of
performing scheduling and MCS selection using only the transmission
power. However, in the present invention it may be possible to
perform scheduling and MCS determination using both the
transmission power and information (for example, CIR information or
quality information indicative of a transmission rate judged to
enable the reception) transmitted from a terminal. It is thereby
possible to increase the reliability of the scheduling and MCS
determination. Further, it is possible to apply to determining the
number of codes and/or coding rate associated with the transmission
rate and transmission power.
[0134] As is apparent from the foregoing, the base station
apparatus and radio transmission method of the present invention
are capable of performing scheduling and MCS selection of DSCH
using transmission power of DPCH or DPCCH that can be monitored at
a transmitting side, whereby it is possible to performing
scheduling and MCS selection of DSCH with the need of information
from a terminal side eliminated.
[0135] This application is based on the Japanese Patent
Applications No. 2001-012451 filed on Jan. 19, 2001, and No.
2001-040413 filed on Feb. 16, 2001, entire contents of which are
expressly incorporated by reference herein.
INDUSTRIAL APPLICABILITY
[0136] The present invention is suitable for use in a digital radio
communication system, particularly, in a CDMA system.
* * * * *