U.S. patent application number 14/148225 was filed with the patent office on 2014-05-22 for system and method for controlling high-speed wireless packet between uplink and downlink transmissions.
This patent application is currently assigned to NEC CORPORATION. The applicant listed for this patent is Nahoko KURODA, Jinsock LEE. Invention is credited to Nahoko KURODA, Jinsock LEE.
Application Number | 20140140274 14/148225 |
Document ID | / |
Family ID | 36203119 |
Filed Date | 2014-05-22 |
United States Patent
Application |
20140140274 |
Kind Code |
A1 |
KURODA; Nahoko ; et
al. |
May 22, 2014 |
SYSTEM AND METHOD FOR CONTROLLING HIGH-SPEED WIRELESS PACKET
BETWEEN UPLINK AND DOWNLINK TRANSMISSIONS
Abstract
The mobile station 2-1 determines whether a current maximum
transmission rate is sufficient or not in a predetermined cycle by
using a maximum transmission rate R indicated by a pointer, a
volume Q of data accumulated in the buffer 22-1 and a requested
delay T determined according to service of data. The mobile station
2-1 transmits a determination result as an RR signal in a
predetermined control signal field within an uplink E-DPCH to the
base station 1. The base station 1 receives an RR signal from the
mobile station 2-1, determines an increment/decrement of the
maximum transmission rate allowed for the mobile station 2-1 to use
such that a noise rise fails to exceed a predetermined threshold
value and notifies the mobile station 2-1 of the determination as
an RG signal by a downlink E-DPCCH. The mobile station 2-1 ups or
downs the position of the pointer according to the RG signal.
Inventors: |
KURODA; Nahoko; (Tokyo,
JP) ; LEE; Jinsock; (Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
KURODA; Nahoko
LEE; Jinsock |
Tokyo
Tokyo |
|
JP
JP |
|
|
Assignee: |
NEC CORPORATION
Tokyo
JP
|
Family ID: |
36203119 |
Appl. No.: |
14/148225 |
Filed: |
January 6, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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11577490 |
Jun 15, 2007 |
8654744 |
|
|
PCT/JP2005/019648 |
Oct 19, 2005 |
|
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14148225 |
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Current U.S.
Class: |
370/328 |
Current CPC
Class: |
H04W 52/16 20130101;
H04W 52/286 20130101; H04W 52/367 20130101; H04L 5/0091 20130101;
H04W 52/267 20130101 |
Class at
Publication: |
370/328 |
International
Class: |
H04L 5/00 20060101
H04L005/00 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 20, 2004 |
JP |
2004-305054 |
Claims
1. A radio communication system enabling execution of high-speed
packet transmission on an uplink and a downlink between a base
station and a mobile station, in which said base station comprises
a first transmission means for transmitting a downlink packet
transmission notification signal to the mobile station and a second
transmission means for transmitting a downlink packet to the mobile
station after a predetermined time after the transmission of the
downlink packet transmission notification signal, and said mobile
station comprises a reception means for, upon receiving a downlink
packet transmission notification signal directed to its own
station, receiving a corresponding downlink packet, a first
determination means for determining power usable in each
transmission time unit of a first channel of the uplink according
to the number of downlink packet transmission notification signals
directed to its own station which have been received in a first
predetermined time interval prior to the relevant transmission time
unit, a second determination means for determining a transmission
rate of the first channel based on the usable power, and a
transmission means for transmitting an uplink packet by the first
channel by using a determined transmission rate and transmitting a
reception result notification signal of a downlink packet by a
second channel of the uplink.
2. A mobile station which enables execution of high-speed packet
transmission on an uplink and a downlink provided between the
station and the base station, comprising: a reception means for,
upon receiving a downlink packet transmission notification signal
directed to its own station, receiving a corresponding downlink
packet; a first determination means for determining power usable in
each transmission time unit of a first channel of the uplink
according to the number of downlink packet transmission
notification signals directed to its own station which have been
received in a first predetermined time interval prior to the
relevant transmission time unit; a second determination means for
determining a transmission rate of the first channel based on the
usable power; and a transmission means for transmitting an uplink
packet by the first channel by using a determined transmission rate
and transmitting a reception result notification signal of a
downlink packet by a second channel of the uplink.
3. A base station enabling packet transmission between the base
station and a mobile station to be activated, comprising: a first
transmission means for transmitting a downlink packet transmission
notification signal to the mobile station; a second transmission
means for transmitting a downlink packet to the mobile station
after a predetermined time after the transmission of the downlink
packet transmission notification signal; and a determination means
for determining whether transmission of a downlink packet to the
mobile station in each transmission time unit of a first channel of
the uplink is allowed or not according to the number of the
downlink packet transmission notification signals transmitted to
the mobile station in a first predetermined time interval prior to
the relevant transmission time unit.
4. A radio communication system controlling method of controlling a
radio communication system enabling execution of high-speed packet
transmission on an uplink and a downlink between a base station and
a mobile station, in which said base station transmits a downlink
packet transmission notification signal and transmits a downlink
packet after a predetermined time after the transmission of the
downlink packet transmission notification signal, and said mobile
station, upon receiving a downlink packet transmission notification
signal directed to its own station, receives a corresponding
downlink packet, determines power usable in each transmission time
unit of a first channel of the uplink according to the number of
downlink packet transmission notification signals directed to its
own station which have been received in a first predetermined time
interval prior to the relevant transmission time unit, determines a
transmission rate of the first channel based on the usable power,
transmits an uplink packet by the first channel by using a
determined transmission rate and transmits a reception result
notification signal of a downlink packet by a second channel of the
uplink.
5. A program of a radio communication system controlling method of
controlling a radio communication system that enables execution of
high-speed packet transmission on an uplink and a downlink between
a base station and a mobile station, which causes a computer of the
mobile station to execute processing of, upon receiving a downlink
packet transmission notification signal directed to its own
station, receiving a corresponding downlink packet, processing of
determining power usable in each transmission time unit of a first
channel of the uplink according to the number of downlink packet
transmission notification signals directed to its own station which
have been received in a first predetermined time interval prior to
the relevant transmission time unit, processing of determining a
transmission rate of the first channel based on the usable power,
and processing of transmitting an uplink packet by the first
channel by using a determined transmission rate and transmitting a
reception result notification signal of a downlink packet by a
second channel of the uplink.
6. A program of a radio communication system controlling method of
controlling a radio communication system that enables execution of
high-speed packet transmission on an uplink and a downlink between
a base station and a mobile station, which causes a computer of the
mobile station to execute processing of transmitting a downlink
packet transmission notification signal to the mobile station,
processing of transmitting a downlink packet to the mobile station
after a predetermined time after the transmission of the downlink
packet transmission notification signal, and processing of
determining whether transmission of a downlink packet to the mobile
station in each transmission time unit of a first channel of the
uplink is allowed or not according to the number of the downlink
packet transmission notification signals transmitted to the mobile
station in a first predetermined time interval prior to the
relevant transmission time unit.
7. A radio communication system enabling execution of high-speed
packet transmission on an uplink and a downlink between a base
station and a mobile station, in which said base station comprises
a means for transmitting a downlink packet transmission
notification signal to the mobile station and transmitting a
downlink packet to the mobile station after the transmission of the
downlink packet transmission notification signal, and said mobile
station comprises a means for, upon receiving a downlink packet
transmission notification signal directed to its own station,
receiving a corresponding downlink packet, a means for determining
power usable in each transmission time unit of a channel of the
uplink according to the number of downlink packet transmission
notification signals directed to its own station which have been
received in a predetermined time interval prior to the relevant
transmission time unit, a means for determining a transmission rate
of the channel based on the usable power, and a means for
transmitting an uplink packet by the channel by using a determined
transmission rate and transmitting a reception result notification
signal of a downlink packet by a channel of the uplink.
8. A mobile station which enables execution of high-speed packet
transmission on an uplink and a downlink provided between the
station and the base station, comprising: a means for receiving a
downlink packet corresponding to a downlink packet transmission
notification signal directed to its own station, a means for
determining power usable in each transmission time unit of a
channel of the uplink according to the number of downlink packet
transmission notification signals directed to its own station which
have been received in a predetermined time interval prior to the
relevant transmission time unit; a means for determining a
transmission rate of the channel based on the usable power; and a
means for transmitting an uplink packet by the channel by using a
determined transmission rate and transmitting a reception result
notification signal of a downlink packet by a channel of the
uplink.
9. A base station enabling packet transmission between the base
station and a mobile station to be activated, comprising: a means
for transmitting a downlink packet transmission notification signal
to the mobile station and transmitting a downlink packet to the
mobile station after a predetermined time after the transmission of
the downlink packet transmission notification signal; and a means
for determining whether transmission of a downlink packet to the
mobile station in each transmission time unit of a channel of the
uplink is allowed or not according to the number of the downlink
packet transmission notification signals transmitted to the mobile
station in a predetermined time interval prior to the relevant
transmission time unit.
10. A radio communication system controlling method of controlling
a radio communication system enabling execution of high-speed
packet transmission on an uplink and a downlink between a base
station and a mobile station, in which said base station transmits
a downlink packet transmission notification signal and transmits a
downlink packet after the transmission of the downlink packet
transmission notification signal, and said mobile station receives
a downlink packet corresponding to the downlink packet transmission
notification signal directed to its own station, determines power
usable in each transmission time unit of a channel of the uplink
according to the number of downlink packet transmission
notification signals directed to its own station which have been
received in a predetermined time interval prior to the relevant
transmission time unit, determines a transmission rate of the
channel based on the usable power, transmits an uplink packet by
the channel by using a determined transmission rate and transmits a
reception result notification signal of a downlink packet by a
channel of the uplink.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This is a continuation application of application Ser. No.
11/577,490 filed Jun. 15, 2007, which is a National Stage of
PCT/JP2005/019648 filed Oct. 19, 2005, which claims priority based
on Japanese Patent Application No. 2004-305054, filed Oct. 20,
2004, the contents of all of which are incorporated herein by
reference in their entirety.
FIELD OF THE INVENTION
[0002] The present invention relates to a radio communication
system, a mobile station and a base station, and a radio
communication system controlling method used therefor and a program
thereof and, more particularly, to a radio communication system
controlling method in a case where high-speed packet transmission
between an uplink and a downlink is executed.
DESCRIPTION OF THE RELATED ART
[0003] In a direct code spread multiple system used in WCDMA
(Wideband Code Division Multiple Access), an information signal is
spread by using a spread code on a transmission side and the signal
is inversely spread by using the same code on a reception side,
thereby increasing a ratio of desired wave power to interference or
noise power (hereinafter referred to as SNIR (Signal to Noise
Interference Ratio)).
[0004] Since with the SNIR being above predetermined quality, the
reception side is allowed to receive a desired signal accurately,
even when signals of a plurality of lines are transmitted in the
same frequency band by using spreading, decoding of a signal on
each line is enabled. Although in general, the lower the spread
factor becomes, the larger the number of information bits which can
be transmitted within a unit time becomes, resulting in increasing
an information transmission rate, because an SNIR gain by inverse
spreading is decreased to increase required power necessary for
meeting predetermined quality. A desired wave of a certain mobile
station, however, interferes a signal of other mobile station.
[0005] Accordingly, in WCDMA, transmission power of a mobile
station and a base station is controlled by closed-loop type
transmission power control such that SNIR will have the minimum
power meeting desired quality (see e.g. 3GPP TS25.214 v6.2.0
"Physical Layer Structure (FDD" (2004 June)). When the number of
connected mobile stations is excessively large or when a set
maximum transmission rate is high, an interference component is
increased, so that normal decoding might be impossible even by
inverse spreading.
[0006] As to an uplink, it is accordingly necessary for a base
station to measure a noise rise (reception power to noise power)
and set the number of connected mobile stations and a maximum
transmission rate such that the noise rise fails to exceed a
predetermined threshold value. In a conventional WCDMA system, a
base station control device is notified of a noise rise measurement
value by a base station to control mobile station connection or
reset a maximum transmission rate, thereby controlling the noise
rise to be not more than a threshold value. This is relatively slow
control because it is executed through the base station control
device and it is necessary to set a mean value of a noise rise at
the base station to be sufficiently smaller than a predetermined
threshold value and take a good margin in preparation for a rapid
noise rise increase.
[0007] In 3GPP (3rd Generation Partnership Projects), currently
studied is EUDCH [Enhanced Uplink DCH (Dedicated Channel): uplink
high-speed packet transmission system] (see e.g. 3GPP TR25.896
v6.0.0 "Feasibility Study for Enhanced Uplink for UTRA FDD" (2004
March)).
[0008] Studied in EUDCH is enabling a base station to control a
maximum transmission rate of a mobile station such that a noise
rise fails to exceed a predetermined threshold value. This enables
higher-speed control than noise rise control by a base station
control device and a noise rise variation to be reduced, thereby
allowing a means value of a noise rise to be set to be higher
accordingly. As a result, the number of connected mobile stations
and a maximum transmission rate of a mobile station can be set
higher than those by conventional art to improve uplink coverage
and capacity.
[0009] Other than those described above, also studied in EUDCH is
introducing HARQ (Hybrid Automatic Repeat Request) between a base
station and a mobile station to enable the base station to make a
retransmission request immediately upon detection of a block error.
HARQ enables a retransmission request delay to be reduced, as well
as increasing a probability of proper decoding of a re-transmitted
packet by soft-composing the same with a preceding packet. It is
therefore possible to reduce a delay caused by retransmission to
improve a throughput more than that by a current WCDMA system in
which a base station control device makes a retransmission
request.
[0010] On the other hand, in EUDCH, it is highly probable that
larger transmission power is required in order to support
high-speed transmission. On an uplink, however, there occurs a case
where transmitted other than an EUDCH channel [E-DPCH: Enhanced
DPCH (Dedicated Physical Channel)] are individual channels [DPCCH
(Dedicated Physical Control Channel), DPDCH (Dedicated Physical
Data Channel)] and a control channel of HSDPA (High Speed Data
Packet Access) [HS-DPCCH: Dedicated Physical Control Channel
(uplink) for HS-DSCH (High Speed Down link Shared Channel)] as a
downlink high-speed packet transmission (see e.g. 3GPP TS25.211
v6.1.0 "Physical Channels and Mapping of Transport Channels onto
Physical Channels (FDD)" (2004 June)).
[0011] In general, a control signal of a higher layer whose
requested delay is severe and the like are transmitted by DPDCH as
a circuit switch. In HS-DPCCH, a control signal for HSDPA is
transmitted. In general, a failure of transmission of a control
signal of a higher layer at desired timing might cause line cut-off
or the like and a failure of proper reception of a control signal
of HSDPA prevents proper notification of packet reception
completion/non-completion, resulting in requesting useless
retransmission or requiring retransmission at the base station
control device, thereby increasing a delay. For giving preference
to control signal transmission over data transmission, therefore,
first ensure required power of DPDCH, DPCCH and HS-DPCCH, and then
make remaining power obtained by subtracting power of these
channels from maximum power of the mobile station be power usable
for E-DPCH.
[0012] FIG. 10 shows a schematic diagram of power variation when
DPCCH, DPDCH and E-DPCH are transmitted. Here, a transmission time
unit of DPDCH and E-DPCH is set to be one frame (=15 slots) and a
transmission rate can not be changed within each transmission time
unit. The mobile station first decides on a transmission rate of
DPDCH in a subsequent frame immediately before start of each frame,
and calculates desired power P.sub.w,DPDCH [mW] of the decided
transmission rate.
[0013] Thereafter, set power obtained by subtracting required power
P.sub.w,DPDCH [mW] and P.sub.w,DPCCH [mW] of DPDCH and DPCCH from
the maximum power P.sub.w,max [mW] of the mobile station to be
power P.sub.w,EDPCH [mW] which can be used by E-DPCH to decide on a
transmission rate whose power is not more than usable power and
which satisfies a required transmission rate of E-DPCH. In the
subsequent frame, transmit DPCCH, DPDCH and E-DPCH with required
power of the determined transmission rate.
[0014] Assume here as a power value expression that in a case where
with a first subscript as "w", that is, P.sub.w,name, represents a
true value ([mW]) and with the first subscript as "d", that is,
P.sub.d,name represents a decibel value ([dBm]). Such conversion
expression as follows is applied between them:
P.sub.d,name [dBm]=10 log(P.sub.w,name [mW])
[0015] With the above-described direct code spread multiple system,
however, there is a case where HS-DPCCH is transmitted on an
uplink. On HS-DPCCH, an ACK (Acknowledgement)/NACK (Negative
Acknowledgement) signal which notifies a reception result of a
packet received on a downlink and a CQI (Channel Quality Indicator)
signal which notifies reception quality of a downlink are
transmitted.
[0016] These signals are transmitted by power obtained by adding
power offsets .DELTA..sub.CQI, .DELTA..sub.ACK and .DELTA..sub.NACK
[dB] notified by the network in advance to power P.sub.d,DPCCH
[dBm] of DPCCH, to which .DELTA..sub.CQI, .DELTA..sub.ACK and
.DELTA..sub.NACK, difference values can be set. Although since the
ACK/NACK signal is in particular required to have a low error rate,
.DELTA..sub.ACK and .DELTA..sub.NACK are in many cases set to be
higher than .DELTA..sub.CQI, its transmission will be irregular
because the ACK/NACK signal is generated in response to downlink
packet reception. As shown in FIG. 11, therefore, required power
P.sub.w,HS [mW] of HS-DPCCH is irregularly increased or decreased
within a frame by the ACK/NACK signal to make determination of
power which can be used for E-DPCH before starting the frame
difficult.
[0017] Assume in FIG. 11, for example, that power obtained by
subtracting the required power P.sub.w,HS, P.sub.w,DPDCH and
P.sub.w,DPCCH [mW] of HS-DPCCH, DPDCH and DPCCH at the start of
each frame from the maximum power P.sub.w,MAX [mW] of the mobile
station is power which can be used for E-DPCH. Although in such a
case where no transmission of the ACK/NACK signal exists at the
start of a frame as a frame 2 in the figure, the power which can be
used for E-DPCH will be P.sub.1 [mW], when transmission of E-DPCH
is started at a transmission rate whose required power is P.sub.1,
a total of required power will exceed maximum power of the mobile
station at the occurrence of transmission of the ACK/NACK signal in
the frame.
[0018] With conventional WCDMA, when required power exceeds maximum
power, power of each channel is evenly reduced to make the required
power be the maximum power while maintaining a power ratio of all
the channels to be constant (all channel even reduction). Executing
all channel even reduction leads to deterioration of reception
quality not only of E-DPCH but also of DPDCH or HS-DPCCH.
[0019] As described in the conventional art, a control signal of a
higher layer or HSDPA is transmitted on DPDCH and HS-DPCCH and when
these develop an error, such a problem occurs as line cut-off or an
increase in an HSDPA transmission delay. On the other hand, in a
case not of all channel even reduction but of preferential
reduction of E-DPCH, when transmission of the ACK/NACK signal
occurs frequently within a frame, for example, when a downlink
packet is successively transmitted, five slots in one frame (15
slots), that is, one-third of the frame will have reduced power to
have a possibility that E-DPCH quality will considerably
deteriorate. As a result, no E-DPCH will be properly received to
increase retransmission, thereby increasing a transmission
delay.
[0020] Furthermore, as another simple expansion, also possible is
ensuring power of the ACK/NACK signal all the time. More
specifically, it is a method in which power P.sub.d,MAX-HS [dBm]
obtained by adding a maximum power offset of HS-DPCCH:
.DELTA..sub.max
[dB]=max(.DELTA..sub.CQI,.DELTA..sub.ACK,.DELTA..sub.NACK) [dB]
to the DPCCH power is used as required power P.sub.d,HS [dBm] of
HS-DPCCH and the remaining power obtained by subtracting the power
P.sub.w,DPDCH, P.sub.w,DPCCH and P.sub.w,HS [mW] of DPDCH, DPCCH
and HS-DPCCH from the maximum power P.sub.w,MAX [mW] is used as
power which can be used for E-DPCH (see FIG. 12).
[0021] In this case, while such a problem of excess over maximum
power as described above is resolved, because power is ensured for
the ACK/NACK signal even when no AKC/NACK signal is transmitted at
all as in a frame 3, power which can be used for E-DPCH is reduced
to degrade a throughput of E-DPCH.
[0022] Thus, an object of the present invention is to provide a
radio communication system, a mobile station and a base station,
and a radio communication system controlling method used therefor
and a program thereof which solve the above-described problems and
enable reception quality of DPDCH and HS-DPCCH to be improved, as
well as enabling a throughput of E-DPCH to be increased.
SUMMARY OF THE INVENTION
[0023] A radio communication system according to the present
invention is a radio communication system enabling execution of
high-speed packet transmission on an uplink and a downlink between
a base station and a mobile station, in which
[0024] the base station includes a first transmission means for
transmitting a downlink packet transmission notification signal to
the mobile station and a second transmission means for transmitting
a downlink packet to the mobile station after a predetermined time
after the transmission of the downlink packet transmission
notification signal, and
[0025] the mobile station includes a reception means for, upon
receiving a downlink packet transmission notification signal
directed to its own station, receiving a corresponding downlink
packet, a first determination means for determining power usable in
each transmission time unit of a first channel of the uplink
according to the number of downlink packet transmission
notification signals directed to its own station which have been
received in a first predetermined time interval prior to the
relevant transmission time unit, a second determination means for
determining a transmission rate of the first channel based on the
usable power, and a transmission means for transmitting an uplink
packet by the first channel by using a determined transmission rate
and transmitting a reception result notification signal of a
downlink packet by a second channel of the uplink.
[0026] The mobile station according to the present invention is a
mobile station which enables execution of high-speed packet
transmission on an uplink and a downlink provided between the
station and the base station and includes a reception means for,
upon receiving a downlink packet transmission notification signal
directed to its own station, receiving a corresponding downlink
packet, a first determination means for determining power usable in
each transmission time unit of a first channel of the uplink
according to the number of downlink packet transmission
notification signals directed to its own station which have been
received in a first predetermined time interval prior to the
relevant transmission time unit, a second determination means for
determining a transmission rate of the first channel based on the
usable power, and a transmission means for transmitting an uplink
packet by the first channel by using a determined transmission rate
and transmitting a reception result notification signal of a
downlink packet by a second channel of the uplink.
[0027] The base station according to the present invention is a
base station which enables execution of high-speed packet
transmission on an uplink and a downlink provided between the
station and the mobile station and includes a first transmission
means for transmitting a downlink packet transmission notification
signal to the mobile station, a second transmission means for
transmitting a downlink packet to the mobile station after a
predetermined time after the transmission of the downlink packet
transmission notification signal, and a determination means for
determining whether transmission of a downlink packet to the mobile
station in each transmission time unit of a first channel of the
uplink is allowed or not according to the number of the downlink
packet transmission notification signals transmitted to the mobile
station in a first predetermined time interval prior to the
relevant transmission time unit.
[0028] A radio communication system controlling method according to
the present invention is a radio communication system controlling
method of controlling a radio communication system enabling
execution of high-speed packet transmission on an uplink and a
downlink between a base station and a mobile station, in which
[0029] the base station transmits a downlink packet transmission
notification signal to transmit a downlink packet after a
predetermined time after the transmission of the downlink packet
transmission notification signal,
[0030] and the mobile station, upon receiving a downlink packet
transmission notification signal directed to its own station,
receives a corresponding downlink packet, determines power usable
in each transmission time unit of a first channel of the uplink
according to the number of downlink packet transmission
notification signals directed to its own station which have been
received in a first predetermined time interval prior to the
relevant transmission time unit, determines a transmission rate of
the first channel based on the usable power, transmits an uplink
packet by the first channel by using a determined transmission rate
and transmits a reception result notification signal of a downlink
packet by a second channel of the uplink.
[0031] A program of a radio communication system controlling method
according to the present invention is a program of a radio
communication system controlling method of controlling a radio
communication system that enables execution of high-speed packet
transmission on an uplink and a downlink between a base station and
a mobile station, which causes a computer of the mobile station to
execute processing of, upon receiving a downlink packet
transmission notification signal directed to its own station,
receiving a corresponding downlink packet, processing of
determining power usable in each transmission time unit of a first
channel of the uplink according to the number of downlink packet
transmission notification signals directed to its own station which
have been received in a first predetermined time interval prior to
the relevant transmission time unit, processing of determining a
transmission rate of the first channel based on the usable power,
and processing of transmitting an uplink packet by the first
channel by using a determined transmission rate and transmitting a
reception result notification signal of a downlink packet by a
second channel of the uplink.
[0032] Another program of a radio communication system controlling
method according to the present invention is a program of a radio
communication system controlling method of controlling a radio
communication system which enables execution of high-speed packet
transmission on an uplink and a downlink between a base station and
a mobile station, which causes a computer of the base station to
execute processing of transmitting a downlink packet transmission
notification signal to the mobile station, processing of
transmitting a downlink packet to the mobile station after a
predetermined time after the transmission of the downlink packet
transmission notification signal, and processing of determining
whether transmission of a downlink packet to the mobile station in
each transmission time unit of a first channel of the uplink is
allowed or not according to the number of the downlink packet
transmission notification signals transmitted to the mobile station
in a first predetermined time interval prior to the relevant
transmission time unit.
[0033] More specifically, in the radio communication system of the
present invention, the base station includes a means for
transmitting a downlink packet transmission notification signal and
a means for transmitting a downlink packet after a predetermined
time after the transmission of the downlink packet transmission
notification signal, and the mobile station includes a means for,
upon receiving a downlink packet transmission notification signal
directed to its own station, receiving a corresponding downlink
packet, a means for determining power usable in each transmission
time unit of the first channel of the uplink according to the
number of downlink packet transmission notification signals
directed to its own station which have been received in a first
predetermined time interval prior to the relevant transmission time
unit, a means for determining a transmission rate of the first
channel based on the usable power, and a means for transmitting an
uplink packet by the first channel by using a determined
transmission rate and transmitting a reception result notification
signal of a downlink packet by a second channel of the uplink.
[0034] The mobile station, when receiving the downlink packet
transmission notification signal directed to its own station,
receives a corresponding downlink packet, determines power usable
in each transmission time unit of the first channel of the uplink
according to the number of downlink packet transmission
notification signals directed to its own station which have been
received in the first predetermined time interval prior to the
relevant transmission time unit, and determines a transmission rate
of the first channel based on the determined usable power, as well
as transmitting an uplink packet by the first channel by using the
determined transmission rate and transmitting a reception result
notification signal of a downlink packet by the second channel of
the uplink.
[0035] In addition, the base station transmits a downlink packet
transmission notification signal, transmits a downlink packet after
a predetermined time after the transmission of the downlink packet
transmission notification signal, and determines whether
transmission of a downlink packet to the mobile station in each
transmission time unit of the first channel of the uplink is
allowed or not according to the number of the downlink packet
transmission notification signals transmitted to the mobile station
in the first predetermined time interval prior to the relevant
transmission time unit.
[0036] In a first radio communication system controlling method of
the present invention, a base station transmits a downlink packet
transmission notification signal and transmits a downlink packet
after a predetermined time after the transmission of the downlink
packet transmission notification signal, and a mobile station, upon
receiving a downlink packet transmission notification signal
directed to its own station, receives a corresponding downlink
packet, determines power usable in each transmission time unit of a
first channel of an uplink according to the number of downlink
packet transmission notification signals directed to its own
station which have been received in a first predetermined time
interval prior to the relevant transmission time unit, determines a
transmission rate of the first channel based on the usable power,
transmits an uplink packet by the first channel by using a
determined transmission rate and transmits a reception result
notification signal of a downlink packet by a second channel of the
uplink.
[0037] In a second radio communication system controlling method of
the present invention, when in the first predetermined time
interval, the number of received downlink packet transmission
notification signals directed to its own station is larger than the
first predetermined threshold value, remaining power obtained by
subtracting required transmission power of a reception result
notification signal from maximum power of the mobile station is
assumed to be power usable for the first channel.
[0038] In a third radio communication system controlling method of
the present invention, when required transmission power of the
uplink exceeds maximum power of the mobile station, power of the
first channel is preferentially reduced.
[0039] In a fourth radio communication system controlling method of
the present invention, according to the number of downlink packet
transmission notification signals transmitted to the mobile station
in the first predetermined time interval, the base station
determines whether transmission of a downlink packet to the mobile
station is allowed or not.
[0040] In a fifth radio communication system controlling method of
the present invention, when in the first predetermined time
interval, the number of downlink packet transmission notification
signals transmitted to the mobile station is larger than a second
predetermined threshold value, the base station refrains from
transmitting the packet transmission notification signal to the
mobile station in a second predetermined time interval after the
first predetermined time interval.
[0041] In a sixth radio communication system controlling method of
the present invention, the mobile station transmits a third channel
of the uplink, controls transmission power of the third channel to
satisfy required quality by closed loop type transmission power
control and assumes power obtained by adding a predetermined power
offset to power of the third channel as required transmission power
of the reception result notification signal.
[0042] In a seventh radio communication system controlling method
of the present invention, when in the first predetermined time
interval, the number of received downlink packet transmission
notification signals directed to its own station is not less than
one, remaining power obtained by subtracting required transmission
power of the reception result notification signal from the maximum
power of the mobile station is assumed to be power usable for the
first channel.
[0043] In an eighth radio communication system controlling method
of the present invention, when in the first predetermined time
interval, the number of downlink packet transmission notification
signals transmitted to the mobile station is not less than one, the
base station refrains from transmitting the packet transmission
notification signal to the mobile station in the second
predetermined time interval after the first predetermined time
interval.
[0044] Thus, the radio communication system controlling method of
the present invention increases power usable for E-DPCH [Enhanced
DPCH (Dedicated Physical Channel)] while reducing a probability
that a total of required power will exceed maximum power of the
mobile station due to transmission of an ACK (Acknowledgement)/NACK
(Negative Acknowledgement) signal, thereby improving reception
quality of DPDCH (Dedicated Physical Data Channel) and HS-DPCCH
[Dedicated Physical Control Channel (uplink) for HS-DSCH (High
Speed Downlink Shared Channel)] and increasing a throughput of
E-DPCH.
BRIEF DESCRIPTION OF THE DRAWINGS
[0045] FIG. 1 is a block diagram showing a structure of a radio
communication system according to a mode of implementation of the
present invention;
[0046] FIG. 2 is a diagram for use in explaining a structure of an
HSDPA channel and a relationship of transmission timing;
[0047] FIG. 3 is a diagram for use in explaining one example of a
scheduling method used in EUDCH;
[0048] FIG. 4 is a diagram showing a time relationship of channels
used in the mode of implementation of the present invention;
[0049] FIG. 5 is a diagram showing power variation of a channel in
the mode of implementation of the present invention;
[0050] FIG. 6 is a block diagram showing a structure of a mobile
station according to one embodiment of the present invention;
[0051] FIG. 7 is a block diagram showing a structure of a base
station according to one embodiment of the present invention;
[0052] FIG. 8 is a flow chart showing processing of determining
power which can be used for E-DPCH at the mobile station according
to one embodiment of the present invention;
[0053] FIG. 9 is a flow chart showing processing of determining
whether downlink packet transmission is allowed or not at the base
station according to one embodiment of the present invention;
[0054] FIG. 10 is a diagram for use in explaining a method of
determining power which can be used for E-DPCH in conventional
art;
[0055] FIG. 11 is a diagram for use in explaining a problem in
conventional art; and
[0056] FIG. 12 is a diagram for use in explaining a problem in
conventional art.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0057] Next, a mode of implementation of the present invention will
be described with reference to the drawings. FIG. 1 is a block
diagram showing a structure of a radio communication system
according to a mode of implementation of the present invention.
Shown in FIG. 1 is such a radio communication system as
simultaneously provides services of HSDPA (High Speed Data Packet
Access) and EUDCH [Enhanced Uplink DCH (Dedicated Channel): uplink
high-speed packet transmission system] by using a WCDMA (Wideband
Code Division Multiple Access) system.
[0058] The radio communication system according to the mode of
implementation of the present invention includes a base station 1,
a plurality of mobile stations 2-1 and 2-2, and a base station
control device 3 to which the base station 1 is connected.
[0059] The base station 1 and the mobile station 2-1 execute
transmission and reception with an individual control channel
(DPCCH: Dedicated Physical Control Channel) and an individual data
channel (DPDCH: Dedicated Physical Data Channel) set. With both
uplink/downlink DPCCH including a pilot signal and a TPC
(Transmission Power Control) signal, the mobile station 2-1 and the
base station 1 each measure reception quality of the pilot signal
and transmit the TPC signal which instructs on increment/decrement
of power so as to close to a predetermined target SIR (Signal to
Interference Ratio) to execute high-speed closed-loop type
transmission power control.
[0060] In addition, DPCCH also includes a transmission rate
information signal (TFCI: Transport Format Combination Indicator)
of DPDCH.
[0061] On the other hand, with HS-SCCH (High Speed-Shared Control
Channel), HS-PDSCH (High Speed-Physical Data Shared Channel),
HS-DPCCH (High Speed-Dedicated Physical Control Channel), E-DPCH
(Enhanced-Dedicated Physical Channel) and E-DPCCH
(Enhanced-Dedicated Physical Control Channel) set together with the
individual channels, the base station 1 and the mobile station 2-2
execute high-speed packet transmission on downlink/uplink.
[0062] Assume here that between the base station 1 and the mobile
station 2-2, downlink high-speed packet transmission is executed by
HSDPA and uplink high-speed packet transmission is executed by
EUDCH. In addition, HS-SCCH is a downlink control channel of HSDPA,
HS-PDSCH is a data channel of HSDPA, HS-DPCCH is an uplink control
channel of HSPDA, E-DPCH is an uplink channel which transmits data
and a control signal of EUDCH, and E-DPCCH is a downlink channel
which transmits a control signal of EUDCH.
[0063] Furthermore, the base station 1 transmits a common pilot
channel (CPICH) to all the mobile stations 2-1 and 2-2 in the cell.
The mobile stations 2-1 and 2-2 in the cell establish and ensure
synchronization by using CPICH and measure reception quality of a
propagation path.
[0064] In the mode of implementation of the present invention, used
as a time unit related to transmission processing are a frame and a
sub-frame. In the mode of implementation of the present invention,
a frame length is assumed to be 10 ms (=15 slots) and a sub-frame
length is assumed to be 2 ms (=3 slots). In addition, a data
transmission rate can be determined for each transmission time unit
and it can not be changed within the transmission time unit. A
transmission time interval (TTI) of the transmission time unit can
be set to have a different value for each channel and in the mode
of implementation of the present invention, TTI of channels
(HS-SCCH, HS-PDSCH, HS-DPCCH) related to HSDPA is assumed to be one
sub-frame and TTI of channels (E-DPCCH, E-DPCH) related to EUDCH,
and DPDCH and DPCCH is assumed to be one frame.
[0065] FIG. 2 is a diagram for use in explaining structures of
HSDPA channels and a relationship of transmission timing. Shown in
FIG. 2 are frame structures and transmission timing of channels
(HS-SCCH, HS-PDSCH, HS-DPCCH) related to HSDPA.
[0066] HS-SCCH is a shared channel for transmitting a downlink
packet transmission notification signal which notifies transmission
of HS-PDSCH, on which signals to a plurality of mobile stations are
time-multiplexed on a sub-frame basis for transmission. In
addition, the downlink packet transmission notification signal
includes control signals (transport block size, modulation, coding
rate, the number of codes, etc) necessary for receiving HS-PDSCH
data, which are classified into two control signal sets (.left
brkt-top.control signal set 1.right brkt-bot. and .left
brkt-top.control signal set 2.right brkt-bot.).
[0067] The .left brkt-top.control signal set 1.right brkt-bot.
includes information (modulation, the number of codes) necessary
for the mobile stations 2-1 and 2-2 to execute inverse spreading
and is transmitted in the first slot of each HS-SCCH sub-frame. The
.left brkt-top.control signal set 2.right brkt-bot. includes a
control signal related to HARQ which is necessary for decoding
processing and is transmitted in second and third slots of each
HS-SCCH sub-frame. Thus, the reason why the signals are divided
into two control signals sets is to enable inverse spread of
HS-PDSCH to be started at a stage of receiving the first slot of
HS-SCCH to reduce a reception delay of HS-PDSCH.
[0068] In addition, since HS-SCCH transmits signals of the
plurality of mobile stations 2-1 and 2-2 in time-multiplexing
manner, each of the mobile stations 2-1 and 2-2 needs to determine
whether it is a downlink packet transmission notification signal
directed to its own station or not. Therefore, the base station 1
transmits a data block of the .left brkt-top.control signal set
1.right brkt-bot. as being masked with mobile station ID
(identification information) of the mobile stations 2-1 and 2-2 to
which transmission is made. The mobile station ID is notified to
the base station 1 and each of the mobile stations 2-1 and 2-2 by
the base station control device 3 in advance, and upon receiving a
first slot of the HS-SCCH sub-frame, the mobile station 2-1, 2-2
removes masking by its own station ID and when obtaining the .left
brkt-top.control signal set 1.right brkt-bot., determines that it
is a control signal directed to its own station to start reception
of the corresponding HS-PDSCH.
[0069] HS-PDSCH is a shared channel for executing high-speed data
transmission, on which transmission is made with a delay of two
slots from HS-SCCH. HS-DPCCH is a control channel of an uplink,
which transmits a CQI (Channel Quality Indicator) signal for
notifying a downlink reception quality measurement result and an
ACK (Acknowledgement)/NACK (Negative Acknowledgement) signal for
notifying a packet reception result. The ACK/NACK signal is
transmitted in the first slot of the HS-DPCCH sub-frame after about
7.5 slots after the reception of the packet by HS-PDSCH, and the
CQI signal is transmitted in the second and third slots of the
HS-DPCCH sub-frame in a cycle instructed in advance by the network.
Transmission power of HS-DPCCH is determined based on offset power
.DELTA..sub.CQI, .DELTA..sub.ACK and .DELTA..sub.NACK which are
notified in advance by the network similarly to the above-described
conventional art.
[0070] FIG. 3 is a diagram for use in explaining one example of a
scheduling method used in EUDCH. Description made in FIG. 3 is one
example of a method of controlling a maximum transmission rate of
EUDCH. Shown in FIG. 3 is a control method at the mobile station
2-1, with the other mobile stations 2-2 and 2-3 adopting the same
control method as that of the mobile station 2-1, and the control
executed at the mobile station 2-1 will be described in the
following.
[0071] Similarly to the above-described conventional art, the
maximum transmission rate of EUDCH is controlled by the base
station 1. The base station control device 2 notifies the mobile
station 2-1 and the base station 1 of a set of transmission rates
(32 kbps, 64 kbps, 128 kbps, 256 kbps, 384 kbps) in advance and the
mobile station 2-1 holds a pointer indicative of a maximum
transmission rate currently allowed to use in the transmission rate
set (See 21-1 in FIG. 3).
[0072] The mobile station 2-1 determines whether a current maximum
transmission rate is sufficient or not in a predetermined cycle
according to the following conditions by using a maximum
transmission rate R indicated by the pointer, a volume of data Q
accumulated in a buffer 22-1 and a requested delay T determined
according to service of data (see 23-1 in FIG. 3):
Q/T.gtoreq.R: maximum transmission rate increase request (Up)
Q/T<R: maximum transmission rate decrease request (Down)
[0073] The mobile station 2-1 transmits a determination result as
an RR (Rate Request) signal in a predetermined control signal field
in the uplink E-DPCH to the base station 1. The base station 1
receives the RR signal from the mobile station 2-1, determines an
increment or a decrement of the maximum transmission rate allowed
for the mobile station 2-1 to use such that a noise rise fails to
exceed a predetermined value and notifies the mobile station 2-1 of
the determination as an RG (Rate Grant) signal by the downlink
E-DPCCH. The mobile station 2-1 ups or downs a position of the
pointer according to the RG signal.
[0074] The mobile stations 2-1 to 2-3 and the base station 1 in the
mode of implementation of the present invention are characterized
in that i) the mobile stations 2-1 to 2-3 determine, according to a
reception result of the first slot of HS-SCCH, power which can be
used for E-DPCH in a subsequent frame, ii) an HSDPA scheduler of
the base station schedules downlink packet transmission taking
power which can be used for E-DPCH into consideration, and iii)
when the total required power of the uplink exceeds maximum power
of the mobile stations 2-1 to 2-3, the mobile stations 2-1 to 2-3
preferentially reduce power of E-DPCH.
[0075] FIG. 4 is a diagram showing a time relationship of channels
used in the mode of implementation of the present invention. Shown
in FIG. 4 is transmission timing of each of HS-SCCH, HS-DPCCH and
E-DPCH.
[0076] .left brkt-top.1.right brkt-bot. .left brkt-top.2.right
brkt-bot., . . . .left brkt-top.10.right brkt-bot. of HS-SCCH
represent a first slot of each HS-SCCH sub-frame. As described
above, a control signal block contained in the first slot of
HS-SCCH is masked with an ID of the mobile stations 2-1 to 2-3 as a
destination of the control signal.
[0077] Accordingly, each of the mobile stations 2-1 to 2-3 receives
the first slot of each HS-SCCH sub-frame to determine whether it is
a downlink packet transmission notification signal directed to its
own station or not according to whether the .left brkt-top.control
signal set 1.right brkt-bot. is obtained by removing, in the
subsequent one slot, the masking by the ID of its own station. When
determining that it is a downlink packet transmission notification
signal directed to its own station, each of the mobile stations 2-1
to 2-3 receives one sub-frame of the HS-PDSCH whose transmission is
started with a delay of two slots (illustration is omitted in the
figure) to transmit the ACK/NACK signal in the sub-frame of the
HS-DPCCH after about 7.5 slots after the reception of the HS-PDSCH
sub-frame.
[0078] Accordingly, using a determination result of the downlink
packet transmission notification signal of HS-SCCH enables each of
the mobile stations 2-1 to 2-3 to predict whether transmission of
the ACK/NACK signal will exist or not about 10.5 slots before
transmission of the ACK/NACK signal. Therefore, each of the mobile
stations 2-1 to 2-3 counts the number of the ACK/NACK transmissions
in a subsequent E-DPCH frame by using the time difference based on
a reception result of the first slot of HS-SCCH.
[0079] More specifically, among determination results .left
brkt-top.1.right brkt-bot. to .left brkt-top.5.right brkt-bot. of
HS-SCCH corresponding to the ACK/NACK fields .left brkt-top.1.right
brkt-bot. to .left brkt-top.5.right brkt-bot. of HS-DPCCH, count
the number of transmissions determined to be directed to its own
station. As is clear from FIG. 4, due to a relationship of a time
offset of transmission timing between HS-SCCH and E-DPCH, there
exists an ACK/NACK by which no determination of HS-SCCH can be made
before timing of determination of usable power for E-DPCH (.left
brkt-top.5.right brkt-bot. in FIG. 4).
[0080] In the mode of implementation of the present invention,
therefore, the HS-SCCH from .left brkt-top.1.right brkt-bot. to
.left brkt-top.4.right brkt-bot. excluding the HS-SCCH for such an
ACK/NACK signal is considered as a target of count. In other words,
the mobile stations 2-1 to 2-3 are set to count a number N.sub.mine
of received downlink packet transmission notification signals
directed to its own station within a count time T starting 12.5
slots to one slot before the subsequent E-DPCH frame starting
timing. Then, by using a predetermined threshold value N.sub.thr,
required power P.sub.d,HS [dBm] which is ensured for HS-DPCCH is
determined as follows in the subsequent E-DPCH frame:
N.sub.mine.ltoreq.N.sub.thr:P.sub.d,HS=P.sub.d,DPCCH+.DELTA..sub.CQI
[dBm]
N.sub.mine>N.sub.thr:
P.sub.d,HS=P.sub.d,DPCCH+.DELTA..sub.max-HS [dBm],
.DELTA..sub.max-HS=max(.DELTA..sub.CQI,.DELTA..sub.ACK,.DELTA..sub.NACK)
[dB]
[0081] Thereafter, as power P.sub.w,EDCH [mW] which can be used for
E-DPCH, the mobile stations 2-1 to 2-3 determine power obtained by
subtracting required power P.sub.w,DPCCH, P.sub.w,DPDCH and the
determined P.sub.w,HS [mW] of DPCCH, DPDCH and HS-DPCCH from the
maximum power P.sub.w,MAX [mW]. Here, when the first subscript is
"w" as a manner of expressing a power value, P.sub.w,name is
assumed to indicate a true value ([mW]) and when the first
subscript is "d", P.sub.d,name is assumed to indicate a decibel
value ([dBm]). Between these, the following conversion expression
is applied:
P.sub.d,name [dBm]=10 log(P.sub.w,name [mW])
The foregoing is detailed content of the characteristic of the
above i).
[0082] Furthermore, the base station 1 also counts the number of
transmissions of the downlink packet transmission notification
signal to the mobile stations 2-1 to 2-3 from .left
brkt-top.1.right brkt-bot. to .left brkt-top.4.right brkt-bot. of
HS-SCCH similarly to the above. In other words, the base station 1
counts the number N.sub.MS#m of the downlink packet transmission
notification signals transmitted to a mobile station #m within the
count time T of each EUDCH mobile station (mobile station #m).
[0083] Then, when N.sub.MS#m.ltoreq.N.sub.thr, refrain from
transmitting the downlink packet transmission notification signal
to the mobile station #m in a time T' before the subsequent count
time start. As a result, since in a frame in which the mobile
station fails to ensure required power of the ACK/NACK signal, no
downlink packet transmission notification signal can be transmitted
in the HS-SCCH frame at the timing at which the mobile station is
not allowed to detect existence/non-existence of the ACK/NACK
signal transmission, it is possible to prevent required power from
exceeding maximum power due to ACK/NACK transmission which can not
be expected by the mobile station. The foregoing is the detailed
content of the characteristics of the above ii).
[0084] When the threshold value N.sub.thr is set to be not less
than 1, although transmission of the ACK/NACK signal occurs
N.sub.mine times, the required power of the ACK/NACK signal is not
ensured when determining power used for E-DPCH. Accordingly, there
occurs a case where the power might exceed maximum power at the
transmission of the ACK/NACK signal which occurs N.sub.mine times.
In such a case, the mobile station preferentially reduces power of
E-DPCH. As a result, neither power of DPDCH nor that of HS-DPCCH
will be reduced to avoid their deterioration.
[0085] In this case, reception quality of E-DPCH might be degraded,
while the characteristics of i) of the present invention enables
the number of occurrences of such condition to be suppressed below
the N.sub.thr times. Setting the threshold value N.sub.thr to be a
small value enables a rate of deterioration of E-DPCH to be reduced
and even when reception data of E-DPCH is erroneous, only the
number of HARQ (Hybrid Automatic Repeat Request) retransmissions
will be slightly increased, so that effects exerted on a throughput
of E-DPCH can be minimized. The foregoing is the detailed content
of the characteristic of the above iii).
[0086] Thus, in the present embodiment, use of the mobile stations
2-1 to 2-3 and the base station 1 having thus described
characteristics enables power for transmission of the ACK/NACK
signal to be ensured in a frame in which transmission of the
ACK/NACK signal occurs the number of times equal to or more than a
threshold value, resulting in reducing power accordingly which can
be used for E-DPCH. Therefore, in the mode of implementation of the
present invention, a probability that a total of required power
will exceed maximum power at the transmission of the ACK/NACK
signal is reduced to decrease a rate of erroneous reception of
uplink channels (DPCCH, DPDCH, HS-DPCCH, EUDCH). As a result, it is
possible by the mode of implementation of the present invention to
avoid line connection caused by a reception error of a control
signal of an upper layer or a transmission delay increase, useless
retransmission, a transmission delay increase and the like caused
by a reception error of a control signal of HSDPA.
[0087] In addition, while in the mode of implementation of the
present invention, reduction in power which can be used for E-DPCH
leads to reduction in a transmission rate of E-DPCH, a reception
error rate of E-DPCH is also decreased to reduce the number of
retransmissions by HARQ, resulting in decreasing a transmission
delay.
[0088] Furthermore, as to transmission of the ACK/NACK signal whose
existence/non-existence can not be detected by the mobile stations
2-1 to 2-3, the mode of implementation of the present invention
enables the HSDPA scheduler of the base station 1 to execute
scheduling taking it into consideration. Accordingly, in the mode
of implementation of the present invention, when the mobile
stations 2-1 to 2-3 fail to ensure power required for transmission
of the ACK/NACK signal, no transmission of the ACK/NACK signal will
occur at such timing, so that further reduction is possible in a
probability that a total of required power will exceed maximum
power.
[0089] Moreover, the threshold value N.sub.thr can be set to a
value not less than 1. With the threshold value N.sub.thr set to 0,
even when the ACK/NACK signal is transmitted only once within one
frame, transmission power for the ACK/NACK signal will be ensured
and in this case, 14 slots out of one frame (15 slots) use only a
part of the ensured power which power accordingly will not be used
for E-DPCH. This is low-efficient power use which has a possibility
of inviting a decrease in a system throughput.
[0090] On the other hand, with the threshold value N.sub.thr set to
be small not less than 1, when the ACK/NACK signal transmission
occurs only a few times, without ensuring transmission power for
the ACK/NACK signal, increasing power which can be used for E-DPCH
accordingly enables selection up to a high transmission rate. The
mode of implementation of the present invention therefore enables a
throughput of E-DPCH to be improved more.
[0091] FIG. 5 is a diagram showing power variation of a channel in
the mode of implementation of the present invention. Shown in FIG.
5 is a time variation of transmitted power obtained when the
above-described operation is applied. Here, the threshold value
N.sub.thr is set to 2. The mobile stations 2-1 to 2-3 determine
whether a count result in the count time T is not less than the
threshold value N.sub.thr immediately before start of each frame
and when the determination result is YES (frame 1, frame 4), with
required power P.sub.w,HS [mW] of HS-DPCCH as:
P W , HS [ mW ] = 10 P d , DPCCH + .DELTA. max - HS 10
##EQU00001##
and when the determination result is No (frame 2, frame 3), with
required power P.sub.w,HS [mW] of HS-DPCCH as:
P W , HS [ mW ] = 10 P d , DPCCH + .DELTA. CQI 10 ##EQU00002##
calculate power which can be used for E-DPCH in the subsequent
frame and determine a transmission rate of E-DPCH based on the
calculation.
[0092] In addition, since in the frame 2 and the frame 3, the
required power of the ACK/NACK signal might not be ensured at the
mobile stations 2-1 to 2-3, the HSDPA scheduler of the base station
1 refrains from packet transmission corresponding to timing at
which the mobile stations 2-1 to 2-3 are not allowed to detect
existence/non-existence of transmission of the ACK/NACK signal.
[0093] Moreover, although in the frame 2, a total of required power
exceeds the maximum power at the transmission of the ACK/NACK
signal, the mobile stations 2-1 to 2-3 adjust the power to be the
maximum power by preferentially reducing E-DPCH to be
P'.sub.w,EDPCH (<P.sub.w,EDPCH).
[0094] More specifically, since the mode of implementation of the
present invention enables power which can be used for uplink packet
transmission to be increased while reducing a probability that a
total of required power of the uplink will exceed the maximum power
of the mobile stations 2-1 to 2-3 due to transmission of the
ACK/NACK signal of the downlink packet, reception quality of a
channel other than that for uplink packet transmission can be
improved and also a throughput of the uplink packet transmission
can be effectively increased.
Embodiment 1
[0095] Next, an embodiment of the present invention will be
described with reference to the drawings. FIG. 6 is a block diagram
showing a structure of a mobile station according to one embodiment
of the present invention. In FIG. 6, a mobile station 2 according
to one embodiment of the present invention includes a reception
unit 24, a control signal separation unit 25, a counter 26, a
processing unit 27, an error determination unit 28, a control
signal generation unit 29, a transmission processing unit 30, a
DPDCH transmission rate deciding unit 31, an E-DPCH usable power
deciding unit 32, an E-DPCH transmission rate deciding unit 33,
buffers 34 and 35 and a CPICH reception quality measuring unit
36.
[0096] The reception unit 24 receives DPCCH, HS-SCCH and E-DPCCH
and subjects the same to inversely spreading, from which a control
signal is separated at the control signal separation unit 25. At
this time, the control signal separation unit 25 removes the
masking applied to HS-SCCH by using the mobile station ID of its
own station and determines whether it is a control signal directed
to its own station to notify the counter 26 of the determination
result.
[0097] When determining that it is directed to its own station, the
control signal separation unit 25 sends information such as a
modulation and the number of codes contained in the first slot of
HS-SCCH to the reception unit 24 and sends HARQ control information
contained in the second and third slots to the processing unit 27.
Furthermore, the control signal separation unit 25 sends an RG
signal contained in E-DPCCH to the E-DPCH transmission rate
deciding unit 33.
[0098] Based on the information such as a modulation and the number
of codes received from the control signal separation unit 25, the
reception unit 24 receives the corresponding HS-PDSCH and subjects
the same to inverse spreading to send the result to the processing
unit 27 through the control signal separation unit 25. The
processing unit 27 executes decoding processing based on the HARQ
control signal information received from the control signal
separation unit 25 and the error determination unit 28 determines
whether a data error exists or not from CRC (Cyclic Redundancy
Check). The error determination unit 28 sends the determination
result to the control signal generation unit 29, so that the
control signal generation unit 29 generates the ACK/NACK signal and
sends the same to the transmission processing unit 30.
[0099] The counter 26 counts the number of transmissions of the
ACK/NACK signal occurring in the subsequent E-DPCH frame. More
specifically, based on a determination result of HS-SCCH received
within the count time T which has been described with reference to
FIG. 4, count the number of downlink packet transmission
notification signals transmitted to its own station during the
time. When the count time T ends, the counter 26 sends the count
result to the E-DPCH usable power deciding unit 32 to reset the
count value.
[0100] Furthermore, the transmission processing unit 30
periodically sends information about a current DPDCH transmission
rate and its required transmission power to the DPDCH transmission
rate deciding unit 33, so that the DPDCH transmission rate deciding
unit 33 decides a transmission rate at which transmission is
allowed with currently usable power based on these information. The
DPDCH transmission rate deciding unit 33 further decides a DPDCH
transmission rate in a subsequent frame among transmission rates
enabling transmission based on the volume of data accumulated in
the buffer 34 for DPDCH. Thereafter, the DPDCH transmission rate
deciding unit 33 notifies the E-DPCH usable power deciding unit 32
of the decided transmission rate, its required power of DPDCH and
information about required power of DPCCH.
[0101] The E-DPCH usable power deciding unit 32 decides, as usable
power of E-DPCH, remaining power obtained by subtracting the
notified required power P.sub.w,DPDCH, P.sub.w,DPCCH and P.sub.w,HS
[mW] of DPDCH, DPCCH and HS-DPCCH from the maximum power
P.sub.w,max [mW]. At this time, the required power of HS-DPCCH is
decided by using the method described above with reference to FIG.
4 and FIG. 5 based on information about the number of transmissions
of the ACK/NACK signal occurring in the subsequent E-DPCCH frame
notified by the counter 26. Thereafter, the E-DPCH usable power
deciding unit 32 notifies the E-DPCH transmission rate deciding
unit 33 of the decided E-DPCH usable power.
[0102] The E-DPCH transmission rate deciding unit 33 receives
information about the E-DPCH usable power and the RG signal to
update a pointer based on the RG and further selects a transmission
rate which is not more than the maximum transmission rate indicated
by the pointer and whose required power is not more than the E-DPCH
usable power to consider the selected rate as a transmission rate
of E-DPCH in the subsequent frame.
[0103] The information of the DPDCH transmission rate and the
E-DPCH transmission rate decided by the DPDCH transmission rate
deciding unit 31 and the E-DPCH transmission rate deciding unit 33
are notified to each of the buffers 34 and 35, respectively, so
that a data block of a size corresponding to the transmission rate
is sent from among the data accumulated in the respective buffers
34 and 35 to the transmission processing unit 30.
[0104] In addition, the buffer 35 cyclically sends information
about a current volume of accumulated data and a maximum
transmission rate to the control signal generation unit 29, so that
the control signal generation unit 29 generates an RR signal based
on these information in a manner as described above with reference
to FIG. 4 and sends the generated signal to the transmission
processing unit 30.
[0105] Furthermore, the CPICH reception quality measuring unit 36
cyclically receives a reception quality measurement value of CPICH
from the reception unit 24 and notifies the control signal
generation unit 29 of a mean value of a predetermined time. The
control signal generation unit 29 generates a CQI signal as a
downlink reception quality notification signal from mean reception
quality of CPICH and sends the signal to the transmission
processing unit 30.
[0106] The transmission processing unit 30 subjects the received
DPDCH and E-DPCH data blocks and the control signals received from
the control signal generation unit 29 to necessary processing such
as coding, rate matching, interleaving and spreading and transmits
the result with codes multiplexed.
[0107] FIG. 7 is a block diagram showing a structure of a base
station according to one embodiment of the present invention. In
FIG. 7, the base station 1 according to one embodiment of the
present invention includes a reception unit 12, a control signal
separation unit 13, an HSDPA scheduler 11a, an EUDCH scheduler 11b,
a processing unit 14, an error determination unit 15, a buffer 16,
a control signal generation unit 17 and a transmission processing
unit 18.
[0108] The reception unit 12 receives HS-DPCCH, E-DPCH, DPDCH and
DPCCH and subjects them to inverse spreading to send the result to
the control signal separation unit 13. The control signal
separation unit 13 separates data and a control signal, sends data
contained in the DPDCH and E-DPCH, the HARQ control signal of the
E-DPCH and DPDCH transmission rate information contained in the
DPCCH to the processing unit 14, and sends the ACK/NACK signal and
the CQI signal contained in the HS-DPCCH to the HSDPA scheduler 11a
and the RR signal to the EUDCH scheduler 11b.
[0109] The processing unit 14 executes decoding processing of
E-DPCH and DPDCH by using the HARQ information and the DPDCH
transmission rate information and the error determination unit 15
makes error determination by using a CRC. Thereafter, the
determination result of E-DPCH is sent to the control signal
generation unit 17, so that the control signal generation unit 17
generates the ACK/NACK signal and sends the same to the
transmission processing unit 18.
[0110] On the other hand, the HSDPA scheduler 11a receives the CQI
signal and the ACK/NACK signal from the control signal separation
unit 13 to schedule packet transmission based on these information
and the volume of data accumulated in the buffer 16. Any scheduling
method may be used as a scheduling method used in this case such as
a method of assigning transmission occasions in order, a method of
assigning transmission occasions in descending order of reception
quality, or an intermediate method between the two methods.
Thereafter, the HSDPA scheduler 11a sends scheduling information to
the buffer 16, so that a data block is accordingly sent from the
buffer 16 to the transmission processing unit 18.
[0111] In addition, the HSDPA scheduler 11a includes a counter 111a
provided for each of the mobile stations 2-1 to 2-3 to count the
number of downlink packet transmission notification signals
transmitted to the mobile stations 2-1 to 2-3 within the count time
T of each of the mobile stations 2-1 to 2-3. Then, based on a count
result, determine whether a packet transmission notification can be
transmitted to the mobile stations 2-1 to 2-3 during the time T'
before the subsequent count time starts or not according to the
method described above with reference to FIG. 4 and FIG. 5. After
the determination, the counter 111a has its count number reset.
[0112] On the other hand, the EUDCH scheduler 11b receives the RR
signal from the control signal separation unit 13 to execute
scheduling such that a noise rise goes not more than the threshold
value. Any scheduling method may be used in this case such as a
method of allowing a transmission rate increase request in order, a
method of allowing a transmission rate increase request in
descending order of reception quality, or an intermediate method
between the two methods. Thereafter, the EUDCH scheduler 11b sends
the scheduling information to the control signal generation unit
17, so that the control signal generation unit 17 generates an RG
signal based on the information and sends the same to the
transmission processing unit 18.
[0113] In addition, the control signal generation unit 17
cyclically generates a predetermined bit series for a pilot signal
to be transmitted by CPICH and sends the same to the transmission
processing unit 18. The transmission processing unit 18 subjects
the HSDPA data block received from the buffer 16 and the control
signal received from the control signal generation unit 17 to
necessary processing such as decoding, rate matching, interleaving
and spreading and transmits the obtained result with codes
multiplexed.
[0114] FIG. 8 is a flow chart showing processing of determining
power which can be used for E-DPCH at the mobile station 2
according to one embodiment of the present invention. Shown in FIG.
8 is the processing executed until power which can be used for
E-DPCH in a subsequent frame is determined by the mobile station 2.
When the mobile station 2 is structured to include a CPU (Central
Processing Unit), a ROM (Read Only Memory) for storing a program to
be executed on the CPU and a RAM (Random Access Memory) used as a
working region of the CPU, the above processing shown in FIG. 8 is
realized by executing the program of the ROM expanded to the RAM by
the CPU.
[0115] The mobile station 2 determines whether it is within the
count time T (12.5 slots to 1 slot before the start timing of the
subsequent frame) (Step S1 in FIG. 8) and when it is within the
count time T (Step S2 in FIG. 8), increments the count number
N.sub.mine by one upon receiving a downlink packet transmission
notification signal directed to its own station (Step S3 in FIG.
8).
[0116] When the count time T ends (Step S2 in FIG. 8), the mobile
station 2 compares the count value N.sub.mine with the threshold
value N.sub.thr notified in advance by the base station control
device 3 (Step S4 in FIG. 8) and when the count number N.sub.mine
is larger, decides the required power P.sub.d,HS [dBm] of HS-DPCCH
to be as follows (Step S5 in FIG. 8):
P.sub.d,HS=P.sub.d,DPCCH+.DELTA..sub.CQI
[0117] When the count number N.sub.mine is smaller, the mobile
station 2 sets the required power P.sub.d,HS [dBm] of HS-DPCCH to
be as follows:
P.sub.d,HS=P.sub.d,DPCCH+.DELTA..sub.max-HS
.DELTA..sub.max-HS=max(.DELTA..sub.CQI,.DELTA..sub.ACK,.DELTA..sub.NACK)
Here, .DELTA..sub.max-HS is assumed to be the maximum power offset
among .DELTA..sub.CQI, .DELTA..sub.ACK and .DELTA..sub.NACK (Step
S6 in FIG. 8).
[0118] Thereafter, the mobile station 2 calculates remaining power
which is obtained by subtracting the required power P.sub.w,DPCCH,
P.sub.w,DPDCH and P.sub.w,HS [mW] of DPCCH, DPDCH and HS-DPCCH from
the maximum power P.sub.w,MAX [mW] to determine power which can be
used for E-DPCH (Step S7 in FIG. 8). Thereafter, the mobile station
2 resets the count number N.sub.mine to 0 (Step S8 in FIG. 8).
[0119] The mobile station 2 executes the above operation for each
E-DPCH frame and selects a transmission rate whose required power
is not more than the power which can be used for E-DPCH to transmit
E-DPCH in the subsequent frame.
[0120] FIG. 9 is a flow chart showing processing of determining
whether downlink packet transmission is allowed or not at the base
station 1 according to one embodiment of the present invention.
Shown in FIG. 9 is the processing of determining whether
transmission of a downlink packet transmission notification signal
to the mobile station #m is allowed or not by the base station 1.
When the base station 1 is structured to include a CPU, a ROM for
storing a program to be executed on the CPU and a RAM used as a
working region of the CPU, the above processing shown in FIG. 9 is
realized by executing the program of the ROM expanded to the RAM by
the CPU.
[0121] The base station 1 determines whether it is within the count
time T (Step S11 in FIG. 9) and when it is within the count time
(Step S11 in FIG. 9), transmission of the downlink packet
transmission notification signal to the mobile station #m is
allowed (Step S12 in FIG. 9). When transmitting the downlink packet
transmission notification signal (Step S13 in FIG. 9), the base
station 1 increments a count number N.sub.MS#m by one (Step S14 in
FIG. 9).
[0122] When not within the count time (Step S11 in FIG. 9), the
base station 1 compares the count value N.sub.MS#m with the
threshold value N.sub.thr notified in advance by the base station
control device 3 and when N.sub.MS#m is smaller (Step S15 in FIG.
9), refrain from transmitting the downlink packet transmission
notification signal to the mobile station #m until the subsequent
count time starts (Step S16 in FIG. 9). In other cases, the
downlink packet transmission notification signal may be transmitted
(Step S17 in FIG. 9). Thereafter, the base station 1 resets the
count number N.sub.MS#m (Step S18 in FIG. 9).
[0123] The base station 1 executes the above operation for each
E-DPCH frame and when transmission of the downlink packet
transmission notification signal is allowed, considers the station
as a target of HSDPA scheduling. Otherwise, count the relevant
mobile stations 2-1 to 2-3 out as a target of HSDPA scheduling.
[0124] While in the present invention, the same value is used as
the threshold value N.sub.thr both in the mobile station 2 and the
base station 1, it is not limited thereto and different threshold
values may be set at the mobile station 2 and the base station
1.
[0125] In addition, while in the present invention, the CQI signal
is transmitted on a sub-frame basis, it is not limited thereto and
it may be intermittently transmitted according to a cycle set by
the network in advance. In this case, in a frame whose count number
N.sub.MS#m is not more than the threshold value and in which no CQI
signal transmission exists, required power of HS-DPCCH may be set
to 0 [mW].
[0126] Furthermore, while in the present invention, TTI of an
individual channel and that of a channel related to EUDCH are
assumed to be one frame, they are not limited thereto. For example,
TTI of a channel related to EUDCH may be one sub-frame and TTI of
E-DPCH and E-DPCCH may be different from each other.
[0127] Thus, according to the present embodiment, when transmission
of the ACK/NACK signal occurs more than the number of the threshold
value in a subsequent transmission time unit, power for
transmitting the ACK/NACK signal is ensured to enable reduction in
power which can be used for E-DPCH accordingly. The present
embodiment therefore enables reduction in a probability that a
total of required power will exceed the maximum power at the time
of transmission of the ACK/NACK signal to decrease a reception
error rate of uplink channels (DPCCH, DPDCH, HS-DPCCH and EUDCH).
As a result, the present embodiment makes it possible to avoid line
connection caused by erroneous reception of a control signal of an
upper layer or a transmission delay increase, useless
retransmission, an increase in a retransmission delay and the like
due to an HSDPA control signal reception error.
[0128] While in the present embodiment, reduction in power which
can be used for E-DPCH leads to reduction in an E-DPCH transmission
rate, an E-DPCH reception error rate can be also reduced, so that
the number of retransmissions by HARQ can be decreased, resulting
in enabling reduction in a transmission delay.
[0129] Furthermore, as to ACK/NACK transmission whose
occurrence/non-occurrence can not be detected by the mobile station
2, the HSDPA scheduler 11a of the base station 1 is allowed to
execute scheduling taking it into consideration. Thus, when the
mobile station 2 fails to ensure required power of the ACK/NACK
transmission, no transmission of the ACK/NACK signal will occur at
such timing, thereby further reducing a probability that a total of
required power will exceed the maximum power.
[0130] Also possible is setting the threshold value N.sub.thr to be
a value not less than 1. Setting the threshold value N.sub.thr to 0
results in obtaining transmission power for the ACK/NACK signal
even when the ACK/NACK signal is transmitted only once in one TTI.
In a case where TTI of a transmission time unit is one frame, for
example, 14 out of 15 slots use only a part of the ensured power
which power accordingly can not be used for E-DPCH. This is
low-efficient power use which has a possibility of inviting a
reduction in a system throughput.
[0131] On the other hand, with the threshold value N.sub.thr set to
be a small value not less than 1, when transmission of the ACK/NACK
signal occurs a few times, without ensuring transmission power for
the ACK/NACK signal, power which can be used for E-DPCH can be
accordingly increased to enable selection up to a high transmission
rate. As a result, the present embodiment enables improvement of a
throughput of E-DPCH.
[0132] More specifically, since the present embodiment enables
power which can be used for uplink packet transmission to be
increased while reducing a probability that a total of required
power of the uplink will exceed the maximum power of the mobile
station 2 due to transmission of the ACK/NACK signal of a downlink
packet, it is possible to improve reception quality of a channel
other than those of uplink packet transmission and effectively
increase a throughput of uplink packet transmission.
[0133] Thus structured to operate as described in the following,
the present invention obtains the effect of improving reception
quality of DPDCH and HS-DPCCH and increasing a throughput of
E-DPCH.
* * * * *