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TEPZZ¥Z98978A_T(11) EP 3 098 978 A1

(12) EUROPEAN PATENT APPLICATION

(43) Date of publication: 30.11.2016 Bulletin 2016/48

(21) Application number: 16179931.7

(22) Date of filing: 25.01.2006

(51) Int Cl.:H04B 7/06 (2006.01) H04L 1/00 (2006.01)

H04L 1/06 (2006.01) H04L 1/18 (2006.01)

H04B 7/04 (2006.01)

(84) Designated Contracting States: AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HU IE IS IT LI LT LU LV MC NL PL PT RO SE SI SK TR

(30) Priority: 28.01.2005 JP 2005021681

(62) Document number(s) of the earlier application(s) in accordance with Art. 76 EPC: 06712351.3 / 1 838 023

(71) Applicant: Godo Kaisha IP Bridge 1Tokyo 101-0051 (JP)

(72) Inventor: SUDO, HiroakiTokyo 101-0051 (JP)

(74) Representative: Grünecker Patent- und Rechtsanwälte PartG mbBLeopoldstraße 480802 München (DE)

Remarks: This application was filed on 18-07-2016 as a divisional application to the application mentioned under INID code 62.

(54) COMMUNICATION DEVICE AND COMMUNICATION METHOD

(57) There is provided a communication device ca-pable of transmitting a transfer rate request signal whilereducing it and reducing the interference and power con-sumption when the transfer rate request signal is trans-mitted substantially without lowering the transmission ef-ficiency in the MIMO communication method. In this de-vice, a modulation encoding unit (125) encodes and mod-ulates transmission data transmitted to a communicationpartner of the MIMO communication method and thetransfer rate request signal in the plurality of transmission

antennas. A transmission unit (132) and a transmissionantenna (134) transmit a signal from the modulation en-coding unit (125). A transmission control unit (120) con-trols transmission of a signal transmitted from the trans-mission antenna (134) and transmits a transfer rate re-quest signal of one transmission antenna via the trans-mission antenna (134) according to a comparison resultbetween a difference of the transfer rate request signalin the respective transmission antenna of the communi-cation partner and a predetermined value.

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Description

Technical Field

[0001] The present invention relates to a transmittingapparatus and transmitting method of a MIMO (Multi-In-put Multi-Output) communication scheme that transmitsdifferent signals from a plurality of antennas.

Background Art

[0002] In recent years, MIMO (Multi-Input/Multi-Out-put) communication attracts attention as a technique thatenables communication of large amount of data such asimage. In MIMO communication, different transmissiondata (substreams) is respectively transmitted from a plu-rality of antennas of a transmitting side, and, on the re-ceiving side, a plurality of transmission data mixed to-gether on a channel is demultiplexed to the original trans-mission data using a channel estimation value.[0003] In actuality, in MIMO communication, signalstransmitted from a transmitting apparatus are receivedat the number of antennas larger than or equal to thenumber of transmitting apparatuses, and the channelcharacteristics between the antennas are estimatedbased on pilot signals inserted in the signals received atthe antennas.[0004] The estimated channel characteristics H is ex-pressed by the matrix 232 when there are two transmit-ting antennas and two receiving antennas, for example.In MIMO communication, based on the inverse matrix ofthe obtained channel characteristics H and the receivedsignals obtained at receiving antennas, the transmissionsignals (substream) transmitted from transmitting anten-nas are obtained.[0005] The principle of MIMO communication, whenthe number of antennas of transmitter 10 and receiver20 is two, respectively, will be described using FIG. 1A.Here, the signals transmitted from antennas 11 and 12of transmitter 10 are TX1 and TX2, respectively, and thesignals received by antennas 21 and 22 of receiver 20are RX1 and RX2, respectively. At this time, the receivedsignals (RX1 and RX2) can be expressed by equation 1shown in FIG.1B.[0006] Here, in equation 1, A indicates the channelcharacteristics between transmitting antenna 11 and re-ceiving antenna 21, B indicates the channel characteris-tics between transmitting antenna 12 and receiving an-tenna 21, C indicates the channel characteristics be-tween transmitting antenna 11 and receiving antenna 22and D indicates the channel characteristics betweentransmitting antenna 12 and receiving antenna 22.[0007] At this time, when only signal TX1 is transmittedto receiver 20, for example, TX2 becomes an interferencesignal for receiver 20, and the signal received by antenna21 includes both the desired signal component and in-terference signal component. The same holds true forantenna 22.

[0008] In order to remove (compensate) the above in-terference signal component from the received signalsand obtain the transmission signals (TX1 and TX2), it isnecessary to obtain the inverse matrix of the matrixformed with four channel characteristics A, B, C and D,as shown in equation 2. Therefore, transmitter 10 trans-mits a signal where a known signal (for example, a pilotsignal) for channel estimation is inserted in the transmis-sion signal, and receiver 20 performs channel estimationbased on this known signal, obtains channel character-istics A, B, CandD, and obtains the above inverse matrix.[0009] In actuality, the steps for obtaining the trans-mission signals (TX1 and TX2) from the received signals(RX1 and RX2) include operations such as a ZF (Zero-Forcing) operation that demultiplexes substreams (eachdata) only through the inverse matrix operation ex-pressed by equation 2 or an MMSE (Minimum MeanSquare Error) operation that performs demultiplexing soas to minimize an error.[0010] Thus, in MIMO communication, theoretically, aplurality of signals transmitted at the same frequency andat the same time can be respectively demultiplexed atthe receiver, thereby enabling high-speed and high-ca-pacity communication.[0011] By the way, in a MIMO communication scheme,a plurality of transmission systems that use radio sectionsprovided with power amplifiers having large power con-sumption are required on the transmitting side. It is wellknown that, when a MIMO communication scheme is ap-plied to uplink, the power consumption of receiver 20 willbecome extremely large. Further, downlink is consideredimportant with respect to the throughput of a MIMO com-munication scheme. For these reasons, a MIMO com-munication scheme is generally used only in downlink.[0012] In such a MIMO communication scheme, as dis-closed in Non-Patent Document 1, to further improve thethroughput, a method is studied of independently settinga transmission rate per antenna and transmitting a CQI(Channel Quality Indicator), which is a transmission ratesetting signal of each antenna.[0013] A CQI is a signal that indicates the modulationscheme and coding rate of packet data that can be de-modulated in receiver 20. Transmitter 10, such as a basestation, for example, has the CQI transmitted from re-ceiver 20 at a period set by an upper apparatus such asan RNC (Radio Network Controller). Transmitter 10 re-ceiving the CQI performs scheduling using the CQI trans-mitted from receiver 20 and independently selects perantenna the optimum modulation scheme and codingrate. Then, transmitter 10 modulates and encodes thetransmission data using the selected modulation schemeand coding rate, and transmits the data to receiver 20based on the scheduling result. By this means, by adap-tively changing the transmission rate according to theradio wave propagation environment, it is possible totransmit large amount of data from transmitter 10 to re-ceiver 20.[0014] Non-Patent Document 1: 3GPP TR25.876

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Disclosure of the Invention

Problems to be Solved by the Invention

[0015] However, in a conventional MIMO communica-tion scheme that independently sets a transmission rateper antenna, the transmitter (transmitting apparatus)transmits to a communicating party the transmission raterequest signals (CQI) corresponding to the number ofantennas, and therefore the amount of transmission raterequest signals transmitted from the receiver side to thetransmitting side becomes equivalent times of thenumber of antennas. Thus, when the transmission raterequest signals are transmitted from the receiving side,there are problems that interference to other receivers(users) increases and receiver power consumption in-creases.[0016] It is therefore an object of the present inventionto provide a communication apparatus and a communi-cation method capable of reducing the transmission raterequest signals and performing transmission withoutsubstantially reducing transmission efficiency, and re-duce interference and power consumption upon trans-mission of transmission rate request signals.

Means for Solving the Problem

[0017] The communication apparatus of the presentinvention that transmits transmission data and transmis-sion rate request signals corresponding to a plurality oftransmitting antennas to a communicating party of a MI-MO communication scheme that transmits different datafrom the plurality of transmitting antennas by independ-ently setting a transmission rate per transmitting antenna,employs a configuration including: a transmitting sectionthat transmits the transmission data and the transmissionrate request signals; and a controlling section that con-trols transmission of signals to be transmitted from thetransmitting section, wherein the controlling sectiontransmits, through the transmitting section, the transmis-sion rate request signals corresponding to less transmit-ting antennas than the plurality of transmitting antennas,based on a comparison result between a difference be-tween the transmission rate request signals of the trans-mitting antennas of the communicating party and a pre-determined value.

Advantageous Effect of the Invention

[0018] As described above, according to the presentinvention, in a MIMO communication scheme, it is pos-sible to reduce the transmission rate request signals andperform transmission without substantially decreasingtransmission efficiency, and reduce interference andpower consumption upon transmission of transmissionrate request signals.

Brief Description of Drawings

[0019]

FIG. 1A illustrates the principle of MIMO communi-cation when the number of antennas of a transmitterand receiver is two, respectively;FIG.1B is an equation expressing the relationshipbetween the transmission signals and received sig-nals of FIG. 1A;FIG.2 is a block diagram showing a configuration ofa terminal apparatus, which is a communication ap-paratus, according to Embodiment 1 of the presentinvention;FIG.3 is a block diagram showing a schematic con-figuration of a transmitting apparatus, which is oneexample of a communicating party of the terminalapparatus, shown in FIG.2;FIG. 4 is a flowchart showing a communication sys-tem having a terminal apparatus according to Em-bodiment 1 of the present invention;FIG.5 is a block diagram showing a configuration ofa terminal apparatus, which is a communication ap-paratus, according to Embodiment 2 of the presentinvention;FIG.6 is a block diagram showing a configuration ofa terminal apparatus, which is a communication ap-paratus, according to Embodiment 3 of the presentinvention;FIG.7 is a block diagram showing a configuration ofa terminal apparatus, which is a communication ap-paratus, according to Embodiment 4 of the presentinvention;FIG. 8 is a flowchart showing a communication sys-tem having the terminal apparatus according to Em-bodiment 4 of the present invention; andFIG.9 is a block diagram showing a configuration ofa terminal apparatus, which is a communication ap-paratus, according to Embodiment 5 of the presentinvention.

Best Mode for Carrying Out the Invention

[0020] Now embodiments of the present invention willbe described in detail with reference to the drawings.

(Embodiment 1)

[0021] FIG.2 is a block diagram showing the configu-ration of terminal apparatus 100, which is a communica-tion apparatus, according to Embodiment 1 of the presentinvention.[0022] In a MIMO communication scheme, when thedifference between the transmission rate request signalsof the transmitting antennas of a communicating party issmaller than a predetermined value, by transmitting onlythe transmission rate request signal corresponding toone antenna, terminal apparatus 100 of Embodiment 1

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can reduce transmission rate request signals withoutsubstantially decreasing transmission efficiency and re-duce interference and power consumption upon trans-mission of transmission rate request signals. Terminalapparatus 100 of the present embodiment using a CDMA(Code Division Multiple Access) communication schemewill be described.[0023] Terminal apparatus (communication appara-tus) 100 shown in FIG.2 has transmission controlling sec-tion 120 that controls transmission of transmission data,modulating and encoding section 125 that modulates andencodes the data to be transmitted, transmitting section132 that converts the frequency to a radio frequencyband, and transmitting antenna 134. Furthermore, termi-nal apparatus 100 has receiving antennas 140 and 150,receiving sections 142 and 152, interference compen-sating section 160, transmission rate request generatingsections 144 and 154, comparing section 163, P/S (par-allel-to-serial) converting section (indicated by "P/S" inFIG.2) 164, selecting section 165, decoding section 166and S/P (serial-to-parallel) converting section (indicatedby "S/P" in FIG.2) 168.[0024] Transmission controlling section 120 controlstransmission of the transmission signal transmitted totransmitting apparatus (base station) 200, stores and out-puts the transmission signal to modulating and encodingsection 125 at the transmission time.[0025] Further, transmission controlling section 120controls transmission based on the transmission rate re-quest signals of transmitting antennas 210 and 220 ofeach communicating party inputted from transmissionrate request generating sections 144 and 154, and theretransmission request signal from S/P converting sec-tion 168.[0026] Furthermore, transmission controlling section120 controls transmission of the transmission rate re-quest signals based on the selection result inputted fromselecting section 165. To be more specific, transmissioncontrolling section 120 controls transmission of the trans-mission rate request signals corresponding to thenumber of all antennas or the transmission rate requestsignal corresponding to one transmitting antenna of thecommunicating party selected by selecting section 165.[0027] Modulating and encoding section 125 modu-lates and encodes the transmission data and outputs theresult to transmitting section 132. The modulated andencoded transmission signal is converted to a radio fre-quency band by transmitting section 132 and transmittedthrough transmitting antenna 134.[0028] Receiving antennas 140 and 150 receive thedata transmitted from a communicating party (here,transmitting apparatus 200 shown in FIG.3), and respec-tively output the data to corresponding receiving sections142 and 152.[0029] Receiving sections 142 and 152 convert the fre-quency of the received signals, which are radio frequencyband signals received at receiving antennas 140 and150, obtain baseband signals and output the signals to

interference compensating section 160.[0030] Interference compensating section 160 per-forms interference compensation processing on the re-ceived signals converted to baseband signals, obtainsthe data transmitted from transmitting antennas of thecommunicating party, and outputs the obtained transmis-sion data to transmission rate request generating sec-tions 144 and 154 and P/S converting section 164.[0031] Transmission rate request generating sections144 and 154 perform channel quality estimation per an-tenna (for example, first and second transmitting anten-nas 210 and 220 shown in FIG.3) of the communicatingparty, and generate a transmission rate request signal(CQI : Channel Quality Indicator) of each antenna.[0032] Transmission rate request generating sections144 and 154 respectively correspond to the transmittingantennas (for example, first and second transmitting an-tennas 210 and 220 shown in FIG.3) of the communicat-ing party, and outputs the quality estimation result includ-ing transmission rate request signals of antennas.[0033] As in the present embodiment, with the channelquality estimation method performed by transmissionrate request generating sections 144 and 154, calculationcan be performed based on four channel estimation re-sults, when there are two receiving antennas of terminalapparatus 100 and two transmitting antennas of trans-mitting apparatus 200 (refer to FIG.3), which is the com-municating party of terminal apparatus 100, describedlater. For example, quality information of first transmittingantenna 210 (refer to FIG. 3) and second transmittingantenna 220 (refer to FIG.3) is calculated using channelestimation results A, B, C and D of the four systems ofFIG. 1. Quality information of first transmitting antenna210 may be set to A+C, and quality information of secondtransmitting antenna 220 may be set to B+D. Further-more, the quality estimation method described here isonly one example, the present invention is not limited tothe quality estimation results described here and an ar-bitrary quality estimation method may be used.[0034] Comparing section 163 calculates the differ-ence between the quality estimation results (to be morespecific, a transmission rate signal of each transmittingantenna) inputted from transmission rate request gener-ating sections 144 and 154, compares the difference be-tween the calculated transmission rate request signal val-ues of the antennas on the transmitting side with a thresh-old value and outputs the result to selecting section 165.Here, the comparison result calculated by comparingsection 163 indicates whether or not to transmit the trans-mission rate requests corresponding to the number ofantennas of the communicating party that transmits datato terminal apparatus 100.[0035] Based on the quality estimation results (includ-ing the transmission rate request signal of each antenna)which are inputted from transmission rate request gen-erating sections 144 and 154 and respectively corre-spond to the antennas of the communicating party, andinformation inputted from comparing section 163, select-

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ing section 165 selects whether to input to transmissioncontrolling section 120 the transmission rate request sig-nals to be transmitted to the communicating party corre-sponding to all antennas or corresponding to one anten-na. The selection result determined by selecting section165 is outputted to transmission controlling section 120.Furthermore, when a retransmission request signal is in-putted from S/P converting section 168 to transmissioncontrolling section 120, transmission controlling section120 transmits the retransmission request signal to thecommunicating party and transmits transmission rate re-quest signals based on the selection result from selectingsection 165.[0036] P/S converting section 164 P/S converts the da-ta obtained by compensation by interference compen-sating section 160 and transmitted per transmitting an-tenna (for example, first and second transmitting anten-nas 210 and 220showninFIG.3) of the communicatingparty, and outputs the converted data to decoding section166.[0037] Decoding section 166 performs decodingprocessing on the data P/S converted by P/S convertingsection 164, and outputs the result to S/P converting sec-tion 168. Furthermore, when there is an error in the re-ceived signal, a retransmission request signal is extract-ed in S/P converting section 168 and outputted to trans-mission controlling section 120. Upon reception of theretransmission request signal, transmission controllingsection 120 transmits the retransmission request signalto the communicating party (here, transmitting apparatus200 shown in FIG.3).[0038] FIG.3 is a block diagram showing a schematicconfiguration of a transmitting apparatus, which is oneexample of a communicating party of terminal apparatus100, according to Embodiment 1 of the present inventionshown in FIG.2.[0039] Transmitting apparatus 200 shown in FIG. 3 isused, for example, as a base station and transmits dif-ferent data from a plurality of transmitting antennas (here,first transmitting antenna 210 and second transmittingantenna 220) to a plurality of terminal apparatuses.[0040] Transmitting apparatus 200 has modulatingand encoding sections 213 and 223, transmitting sec-tions 215 and 225, receiving antenna 240, receiving sec-tion 243, demodulating section 245, decoding section247, S/P converting section (indicated by "S/P" in FIG.3)249 and transmission controlling section 260.[0041] Transmission controlling section 260 controlstransmission of the transmission data (transmission sig-nal). To be more specific, transmission controlling section260 stores the transmission data and outputs the data tomodulating and encoding sections 213 and 223 at a pre-determined transmission time.[0042] Further, transmission controlling section 260controls retransmission based on retransmission infor-mation transmitted from the communicating party (here,terminal apparatus 100), controls the transmission ratebased on transmission rate request signals transmitted

from the communicating party and transmits transmis-sion data using transmitting antennas based on the trans-mission rate request signals.[0043] To be more specific, transmission controllingsection 260 controls retransmission based on the re-transmission request signal (information indicating thatthere is an error in the received signal) from S/P convert-ing section 168. Then, when the transmission rate re-quest signal transmitted from the communicating party(here, terminal apparatus 100) corresponds to only onetransmitting antenna, transmission controlling section260 controls the transmission rate so as to transmit dataat the same transmission rate at all transmitting antennas210 and 220. In this case, modulating and encoding sec-tions 213 and 223 select the same coding rate and mod-ulation scheme.[0044] Modulating and encoding sections 213 and 223perform encoding processing and modulating processingon the data to be transmitted--the data (indicated as"transmission signal" in FIG.3) transmitted from first andsecond transmitting antennas 210 and 220 of transmit-ting apparatus 200--and output the result to transmittingsections 215 and 225. Furthermore, in modulationprocessing of modulating and encoding sections 213 and223, normally the modulation scheme is set independ-ently per transmitting antennas 210 and 220 (3GPPTR25.876), however, when the transmission rate requestsignal from the communicating party (here, terminal ap-paratus 100) corresponds to only one antenna, the samecoding rate and modulation scheme are set.[0045] Transmitting sections 215 and 225 convert thefrequency of the modulated and encoded transmissiondata to a radio frequency band, and output the result tofirst and second transmitting antennas 210 and 220. Firstand second transmitting antennas 210 and 220 transmitthe frequency converted transmission data by transmit-ting sections 215 and 225.[0046] Receiving antenna 240 receives and outputsthe data transmitted from the communicating party to re-ceiving section 243, and receiving section 243 convertsthe frequency of the inputted received data to a basebandsignal and outputs the result to demodulating section245.[0047] Demodulating section 245 performs demodu-lating processing on the inputted received data after fre-quency conversion and outputs the result to decodingsection 247. Here, transmitting apparatus (base station)200 identifies whether the communicating party (terminalapparatus 100) transmits the transmission rate requestsignal corresponding to one transmitting antenna or thetransmission rate request signals corresponding to a plu-rality of (here, two) transmitting antennas.[0048] For example, in the present embodiment wherea MIMO communication scheme is applied to the CDMA(Code Division Multiple Access) communication scheme,demodulating section 245 compares the despreading re-sults of the transmission rate request signals of transmit-ting antennas 210 and 220, and determines that only the

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transmission rate request signal corresponding to onetransmitting antenna is transmitted when the differenceof the two is large.[0049] In this way, even if terminal apparatus 100 doesnot necessarily report information indicating correspond-ing to how many transmitting antennas the transmissionrate request signals are transmitted by the communicat-ing party (terminal apparatus 100), transmitting appara-tus 200 can determine corresponding to how many trans-mitting antennas the transmission rate request signalsare transmitted by terminal apparatus 100.[0050] The received data, which is inputted from de-modulating section 245 and configured in this way, isdecoded by decoding section 247 and outputted to S/Pconverting section 249.[0051] S/P converting section 249 extracts the data,retransmission information and transmission rate re-quest information from the transmission signal transmit-ted from the communicating party, and inputs the resultto transmission controlling section 260. That is, S/P con-verting section 249 sorts the received data (received sig-nal) and the retransmission request, quality informationand information indicating the data to be retransmittedthat are reported by the communicating party, and out-puts the result to transmission controlling section 260.[0052] Next, the operation of a system having terminalapparatus 100 having the above configuration, and trans-mitting apparatus 200 as a base station will be describedusing FIG.4. FIG. 4 is a flowchart of a communicationsystem having communication apparatus (terminal ap-paratus) 100 according to Embodiment 1 of the presentinvention.[0053] First, in step S1, terminal apparatus 100 re-ceives a transmission signal from transmitting apparatus(base station) 200, which is a communicating party,through receiving antennas 140 and 150, and the flowproceeds to step S2.[0054] To be more specific, in step S1, in terminal ap-paratus 100, the received signals received through re-ceiving antennas 140 and 150 are converted to basebandsignals by receiving sections 142 and 152, subjected tointerference compensation processing by interferencecompensating section 160, and become data transmittedfrom each transmitting antenna of the communicatingparty.[0055] In terminal apparatus 100, by using the trans-mission data from interference compensating section160, transmission rate request generating sections 144and 154 perform channel quality estimation per antenna(for example, first and second transmitting antennas 210and 220 shown in FIG.3) of the communicating party,and generate a transmission rate request signal of eachantenna.[0056] In step S2, terminal apparatus 100 determineswhether or not the generated transmission rate requestsignal (transmission rate request value) difference issmaller than a threshold value, the flow proceeds to stepS3 when the difference is larger than or equal to the

threshold value, and the flow proceeds to step S4 whenthe difference is smaller than the threshold value. To bemore specific, in comparing section 163 of terminal ap-paratus 100, the difference between the transmissionrate request values inputted from transmission rate re-quest generating sections 144 and 154 is calculated, thecalculated transmission rate request value differenceand a threshold value are compared, and it is determinedwhether the calculated difference is larger or smaller thanthe threshold value (here, it is determined whether or notthe difference is smaller than the threshold value) is de-termined. Based on this determination, comparing sec-tion 163 outputs to selecting section 165 information in-dicating whether or not to transmit the transmission raterequests corresponding to the number of antennas. Theflow proceeds to step S3 when comparing section 163outputs to selecting section 165 information indicatingthat the transmission rate requests corresponding to thenumber of antennas are transmitted, and the flow pro-ceeds to step S4 when comparing section 163 outputsto selecting section 165 information indicating that thetransmission rate requests corresponding to the numberof antennas are not transmitted.[0057] In step S3, terminal apparatus 100 transmitsthe transmission rate request values of all transmittingantennas of the communicating party to the communi-cating party (transmitting apparatus 200), and the flowproceeds to step S5. To be more specific, in step S3,comparing section 163 outputs information indicatingwhether or not to transmit the transmission rate requestscorresponding to the number of antennas to selectingsection 165, and selecting section 165 selects informa-tion indicating the transmission rate requests corre-sponding to the number of antennas are transmitted fromthis information. Then, selecting section 165 outputs theselected information and the transmission rate requestvalues inputted from transmission rate request generat-ing sections 144 and 154 to transmission controlling sec-tion 120. Through modulating and encoding section 125,transmitting section 132 and transmitting antenna 134,transmission controlling section 120 transmits to trans-mitting apparatus 200 the transmission rate request val-ues of all antennas (here, first and second transmittingantennas 210 and 220 shown in FIG.3) based on infor-mation from selecting section 165.[0058] In step S4, terminal apparatus 100 comparesthe transmission rate request values of the antennas (forexample, first and second transmitting antennas 210 and220) of the communicating party. To be more specific, instep S4, the transmission rate request values of firsttransmitting antenna 210 and second transmitting anten-na 220 are compared, and it is determined whether ornot quality of first transmitting antenna 210 is worse. Theflow proceeds to step S6 when quality of first transmittingantenna 210 is worse, and the flow proceeds to step S7when quality of second transmitting antenna 220 isworse.[0059] To be more specific, in step S4, information in-

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dicating that the transmission rate requests correspond-ing to the number of antennas are not transmitted is in-putted from comparing section 163 to selecting section165 of terminal apparatus 100. Then, selecting section165 compares information inputted from transmissionrate request generating sections 144 and 154 (transmis-sion rate request signal values of first and second trans-mitting antennas 210 and 220 of the communicating par-ty). Next, when quality of first transmitting antenna 210is poor, selecting section 165 outputs the transmissionrate request value of first transmitting antenna 210 totransmission controlling section 120, and the flow pro-ceeds to step S6. When quality of second transmittingantenna 200 is poor, selecting section 165 outputs thetransmission rate request value of second transmittingantenna 220 to transmission controlling section 120, andthe flow proceeds to step S7.[0060] In step S6, in terminal apparatus 100, transmis-sion controlling section 120 transmits a retransmissionrequest signal to transmitting apparatus 200, which is thecommunicating party, transmits the transmission rate re-quest value of first transmitting antenna 210 of transmit-ting apparatus 200 based on the information from select-ing section 165, and then the flow proceeds to step S8.[0061] In step S7, in terminal apparatus 100, transmis-sion controlling section 120 transmits to transmitting ap-paratus 200, which is the communicating party, the trans-mission rate request value of second transmitting anten-na 220 of transmitting apparatus 200 based on informa-tion from selecting section 165, and the flow proceeds tostep S8.[0062] After terminal apparatus 100 performs process-ing of the above steps S1 to S3, S7 and S8, transmittingapparatus 200 receives through receiving antenna 240the transmission signal including the transmission raterequest value transmitted from terminal apparatus 100through these steps. Transmitting apparatus 200 that re-ceives the transmission signal from terminal apparatus100 obtains the transmission rate request values throughreceiving section 243, demodulating section 245, decod-ing section 247 and S/P converting section 249, and per-forms processing of steps S5 and S8.[0063] To be more specific, in step S5, upon receptionof the transmission rate request values of all transmittingantennas from terminal apparatus 100, transmitting ap-paratus 200 (refertoFIG.3) independently sets the trans-mission rate for each antenna (first and second transmit-ting antennas 210 and 220) and transmits data.[0064] To be more specific, in step S5, transmissioncontrolling section 260 of transmitting apparatus 200 setsthe transmission rates of transmitting antennas 210 and220 and controls transmission of data based on the trans-mission rate request obtained from the transmission sig-nal of terminal apparatus 100 through receiving antenna240, receiving section 243, demodulating section 245,decoding section 247 and S/P converting section 249.That is, based on the transmission rate request valuefrom terminal apparatus 100, transmission controlling

section 260 transmits the same data from first and secondtransmitting antennas 210 and 220 through modulatingand encoding sections 213 and 223, and transmittingsections 215 and 225.[0065] Further, in step S8, transmitting apparatus 200sets, as the transmission rate of all transmitting antennas,the transmission rate request value from terminal appa-ratus 100 obtained through receiving antenna 240, re-ceiving section 243, demodulating section 245, decodingsection 247 and S/P converting section 249, and trans-mits the transmission data at the same transmission rate.[0066] Thus, terminal apparatus 100 according to thepresent invention transmits the transmission rate requestsignals corresponding to all antennas of the communi-cating party (transmitting apparatus 200) when the dif-ference between the transmission rate request values(CQI values) for the communicating party (transmittingapparatus 200) is larger than a threshold value. The com-municating party (transmitting apparatus 200) receivingthe transmission rate request signal independently setsthe transmission rate per antenna (here, first and secondtransmitting antennas 210 and 220) and performs trans-mission.[0067] On the other hand, when the difference betweenthe transmission rate request values (CQI values) for thecommunicating party (transmitting apparatus 200) issmaller than a threshold value, terminal apparatus 100transmits the transmission rate request signals corre-sponding to the number of antennas less than the totalnumber of antennas of the communicating party (trans-mitting apparatus 200). The communicating party (trans-mitting apparatus 200) receiving the transmission raterequest signal sets the transmission rate based on thetransmission rate request signal from terminal apparatus100 as the same transmission rate for all antennas, andtransmits transmission data from all antennas.[0068] To be more specific, when it is determined thatthe difference between transmission rate requests issmaller than a threshold value and quality of first trans-mitting antenna 210 is worse, terminal apparatus 100transmits the transmission rate request signal of firsttransmitting antenna 210 to transmitting apparatus 200,which is the communicating party, and transmitting ap-paratus 200 sets the reported transmission rate requestvalue of first transmitting antenna 210 as the same trans-mission rate for all antennas and transmits the transmis-sion data.[0069] Further, when it is determined that the differ-ence between transmission rate requests is smaller thana threshold value and quality of second transmitting an-tenna 220 is worse, terminal apparatus 100 transmits thetransmission rate request signal of second transmittingantenna 220 to transmitting apparatus 200, which is thecommunicating party, and transmitting apparatus 200sets the reported transmission rate request value of sec-ond transmitting antenna 220 as the same transmissionrate for all antennas and transmits the transmission data.[0070] Furthermore, when the difference between the

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transmission rate request value of each transmitting an-tenna of the communicating party calculated by terminalapparatus 100 is smaller than a threshold value, in theabove description, to prevent a decrease in the error rate,out of transmission antennas provided with the commu-nicating party, a transmission rate request signal havingthe worst quality is transmitted.[0071] Thus, according to the present embodiment,when the difference between the transmission rate re-quest values of transmitting antennas 210 and 220 oftransmitting apparatus 200 is smaller than a thresholdvalue, the transmission rate request values transmittedfrom terminal apparatus 100 corresponding to all trans-mission antennas of transmitting apparatus 200 are nottransmitted, and the transmission rate request value cor-responding to only one antenna is transmitted. Upon re-ception of the transmission rate request value, transmit-ting apparatus 200 performs communication using thesame transmission rate for all antennas. Thus, terminalapparatus 100 can reduce the transmission rate requestsignals without substantially decreasing transmission ef-ficiency and reduce interference and power consump-tion. Further, transmitting apparatus 200 can reduce theamount of control information of downlink without sub-stantially decreasing the throughput.[0072] For example, in a communication scheme thatadaptively changes the transmission rate, regardless ofa MIMO communication scheme, it is necessary to trans-mit, to the communicating party, information indicatingat which transmission rate data is transmitted.[0073] Particularly, in a MIMO communication schemethat sets transmission rates per antenna, when informa-tion indicating at which transmission rate data is trans-mitted is transmitted to a transmitting apparatus, infor-mation and the amount of control signals of downlink be-come equivalent times of the number of antennas.[0074] Conversely, in the present embodiment, whentransmitting apparatus 200 performs communication atthe same transmission rate for all transmitting antennas,only control information corresponding to one antennaneeds to be transmitted from terminal apparatus 100,which i s the communicating party of transmitting appa-ratus 200, thereby reducing the amount of control infor-mation of downlink without substantially decreasing thethroughput.[0075] Furthermore, although the case has been de-scribed in the present embodiment where the number oftransmitting antennas of transmitting apparatus 200,which is the communicating party of terminal apparatus100, is two, the number of transmitting antennas of thetransmitting apparatus is not limited to this and may bearbitrarily set.[0076] Furthermore, in contrast to the present embod-iment, a method of transmitting the transmission rate re-quest signal of the transmitting antenna having the bestquality is also possible. To improve the capacity of theoverall system, it is better to transmit the transmissionrate request signal of the transmitting antenna having the

best quality. An example of the above method will bedescribed in Embodiment 4. Also, a method of changingthe transmission rate signal to be transmitted betweenupon first transmission and upon retransmission is alsopossible (upon first transmission, the transmission raterequest signal of the antenna having the best quality istransmitted , and upon retransmission, the transmissionrate request signal of the antenna having the worst qualityis transmitted).

(Embodiment 2)

[0077] FIG.5 is a block diagram showing the configu-ration of terminal apparatus 300, which is a communica-tion apparatus, according to Embodiment 2 of the presentinvention.[0078] Terminal apparatus 300 of Embodiment 2 canfurther reduce false detection of transmission rate re-quest signals by the communicating party than terminalapparatus 100 of Embodiment 1 by transmitting to a com-municating party information indicating whether thetransmission rate request signals corresponding to thenumber of transmitting antennas of the communicatingparty are transmitted or the transmission rate requestsignal corresponding to only one antenna is transmitted.[0079] First, the transmitting apparatus, such as a basestation, which is a communicating party of terminal ap-paratus 300 of Embodiment 2 will be described.[0080] The transmitting apparatus, which is a commu-nicating party of terminal apparatus 300 of Embodiment2 has the same configuration with slight difference in op-eration, compared to transmitting apparatus 200 of Em-bodiment 1 (refer to FIG.3). Thus, only the different op-eration will be described, and the operations of othercomponents will be omitted.[0081] The operation of the transmitting apparatus,which is a communicating party of terminal apparatus300 of Embodiment 2, differs from that of transmittingapparatus 200 of FIG.3 in the operation of S/P convertingsection 249. That is, in the transmitting apparatus of Em-bodiment 2, when transmitting apparatus 200 of FIG.3 isreferred to, S/P converting section 249 outputs a retrans-mission request signal (information indicating whether ornot there is an error in the received signal) to transmissioncontrolling section 320, and, based on information whichis reported by terminal apparatus 300 and indicates cor-responding to how many antennas the transmission raterequest signals are transmitted, extracts and outputs thetransmission rate request signals to transmission con-trolling section 260.[0082] Further, the transmitting apparatus of Embodi-ment 2, similar to transmitting apparatus 200 of Embod-iment 1, is used as, a base station, or the like of a MIMOcommunication scheme applied to a CDMA communica-tion scheme, and can identify whether terminal apparatus300 transmits the transmission rate request signal cor-responding to one antenna or the transmission rate re-quest signals corresponding to a plurality of (here, two)

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antennas. For identification at the transmitting apparatus,a method is used of, for example, comparing the resultsof despreading the transmission rate request signals oftransmitting antennas and determining that the transmis-sion rate request signal corresponding to only one an-tenna is transmitted when the difference between the twois large.[0083] In this way, even if terminal apparatus 300 doesnot necessarily report information indicating correspond-ing to how many transmitting antennas the transmissionrate request signals are transmitted by terminal appara-tus 300, the base station can determine the transmissionrate request signals corresponding to how many anten-nas are transmitted by the terminal. However, to reducefalse detection of transmission rate request signals bythe transmitting apparatus, the method is effective oftransmitting to the transmitting apparatus information in-dicating corresponding to how many antennas the trans-mission rate request signals are transmitted by terminalapparatus 300.[0084] Here, information indicating corresponding tohow many antennas the transmission rate request sig-nals are transmitted by terminal apparatus 300 may beone bit if there are two antennas, for example, and issufficiently small compared to a transmission rate re-quest signal (for example, the transmission rate requestsignal in 3GPP requires 5 bits), so that the amount ofuplink control information does not substantially in-crease.[0085] Terminal apparatus 300 shown in FIG.5 has theconfiguration that removes selecting section 165 from aconfiguration of terminal apparatus 100 of Embodiment1 (refer to FIG.2), and basically has the same configura-tion. Thus, in terminal apparatus 300 of the present em-bodiment, different components from terminal apparatus100 (refer to FIG.2) will be described, and other samecomponents will be assigned the same reference numer-als without further explanations.[0086] In terminal apparatus 300 shown in FIG.5,transmission rate request generating sections 144 and154 output the quality estimation results respectively cor-responding to the antennas of the communicating party(including the transmission rate request signal of eachtransmitting antenna) to comparing section 163 andtransmission controlling section 320. Furthermore, thechannel quality estimation method used by transmissionrate request generating sections 144 and 154 is the sameas described in Embodiment 1, and therefore descriptionthereof will be omitted.[0087] Comparing section 163 calculates the differ-ence between the quality estimation results (to be morespecific, transmission rate signals of the transmitting an-tennas) inputted from transmission rate request gener-ating sections 144 and 154, compares the transmissionrate request signal value of each antenna on the trans-mitting side with a threshold value, and outputs the resultto transmission controlling section 320. Here, the com-parison result calculated by comparing section 163 indi-

cates corresponding to how many transmission antennasof the communicating party, the transmission rate re-quest signals to be transmitted to the communicating par-ty that transmits data to terminal apparatus 300 are trans-mitted.[0088] Transmission controlling section 320 controlstransmission of the transmission signal transmitted to thecommunicating party (for example, transmitting appara-tus 200) and, similar to transmission controlling section120, stores and outputs the transmission signal to mod-ulating and encoding section 125 at the transmissiontime.[0089] Further, transmission controlling section 320controls transmission based on the transmission rate re-quest signals of the transmitting antennas (for example,per first and second transmitting antennas 210 and 220)of the communicating party, which are inputted fromtransmission rate request generating sections 144 and154 and information which is inputted from comparingsection 163 and indicates whether or not the transmissionrate requests corresponding to the number of antennasare transmitted. To be more specific, transmission con-trolling section 320 controls transmission of informationwhich is inputted from comparing section 163 and indi-cates whether or not the transmission rate requests cor-responding to the number of antennas are transmitted,and the transmission of transmission rate request signalsof the transmitting antennas corresponding to this infor-mation, to the transmitting apparatus, which is the com-municating party.[0090] Thus, in Embodiment 2, terminal apparatus 300transmits to the communicating party information indicat-ing whether or not the transmission rate requests corre-sponding to the number of antennas are transmitted. Asa result, it is possible to further reduce false detection oftransmission rate request signals, compared to a casewhere terminal apparatus 100 of Embodiment 1 is used.[0091] Furthermore, in transmitting apparatus (basestation) 200 (refer to FIG.3) receiving a signal from ter-minal apparatus 300, S/P converting section 249 extractsthe retransmission request signal and transmission raterequest signals based on information which is reportedby terminal apparatus 300 and indicates correspondingto how many antennas the transmission rate request sig-nals are transmitted, and outputs the extraction result totransmission controlling section 260 (refer to FIG. 3). Thetransmission rates based on this information are set forpredetermined transmitting antennas, and data transmis-sion is performed from the transmitting antennas.

(Embodiment 3)

[0092] FIG.6 is a block diagram showing the configu-ration of terminal apparatus 400, which is a communica-tion apparatus, according to Embodiment 3 of the presentinvention.[0093] Terminal apparatus 400 of Embodiment 3, hasa variable threshold value used to select whether the

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transmission rate request signals corresponding to thenumber of transmitting antennas of the communicatingparty are transmitted or the transmission rate requestsignal corresponding to one antenna is transmitted, incomparing section 163 of transmitting apparatus 300 ofEmbodiment 2.[0094] As shown in FIG.6, terminal apparatus 400 hasa configuration where the threshold value inputted tocomparing section 163 of terminal apparatus 300 (referto FIG.5) is selected by selecting section 465. Terminalapparatus 400 has a configuration that further adds se-lecting section 465 in the configuration of terminal appa-ratus 300 corresponding to Embodiment 2 shown in FIG.5, and other configuration is basically the same as ter-minal apparatus 300. Thus, the same components willbe assigned the same reference numerals without furtherexplanations.[0095] In terminal apparatus 400, comparing section163 receives from selecting section 465 as input a thresh-old value for comparing the difference between the qual-ity estimation results (to be more specific, transmissionrate signals of the transmitting antennas) inputted fromtransmission rate request generating sections 144 and154, and a threshold value.[0096] Selecting section 465 receives a predeterminednumber of threshold values as input. Selecting section465 selects a predetermined threshold value from theinputted predetermined number of threshold values andoutputs the selection result to comparing section 163.[0097] In Embodiment 3, the threshold values of theselection targets in selecting section 465 are two thresh-old values "threshold value 1" and "threshold value 2."Furthermore, although a case of two threshold valueshas been described in the present embodiment, thepresent invention is not limited to this, and an arbitrarynumber of threshold values may be used. In this case aswell, the comparison result calculated by comparing sec-tion 163 is outputted to transmission controlling section420, and indicates whether or not to transmit the trans-mission rate requests to be transmitted to the communi-cating party that transmits data to terminal apparatus 400corresponding to the number of antennas of the commu-nicating party.[0098] The other components of terminal apparatus400 and advantages obtained by the other componentsare the same as terminal apparatus 300 of Embodiment2, and description thereof will be omitted.[0099] Furthermore, in selecting section 465, the opti-mum value of the threshold value used for selecting cor-responding to how many transmission antennas thetransmission rate request signals are transmitted to thetransmitting apparatus of a base station, which is thecommunicating party, is changed according to variouscommunication conditions. For example, in the followingcase, threshold values are set, and selecting section 465selects and outputs a threshold value to comparing sec-tion 163.

1) Selecting a threshold value according to the number of users using the channel

[0100] When there are a large number of users, it isnecessary to reduce interference to other users, andtherefore a large threshold value is set, and, preferablya transmission rate request signal corresponding to onlyone antenna is transmitted.

2) Selecting a threshold value according to battery power of a terminal

[0101] When there is low battery power, it is necessaryto reduce power consumption, and therefore a largethreshold value is set, and, preferably a transmission raterequest signal corresponding to only one antenna istransmitted.[0102] Furthermore, the threshold value selectionmethod of terminal apparatus 400 of Embodiment 3 isonly one example, the present invention is not limited tothis, and each threshold value may be changed basedon arbitrary conditions.

(Embodiment 4)

[0103] FIG.7 is a block diagram showing the configu-ration of terminal apparatus 500, which is a communica-tion apparatus, according to Embodiment 4 of the presentinvention.[0104] Terminal apparatus 500 of Embodiment 4 hasbasically the same configuration as terminal apparatus100 corresponding to Embodiment 1 shown in FIG.2, andthe same components will be assigned the same refer-ence numerals without further explanation. To be morespecific, in terminal apparatus 500, compared to terminalapparatus 100 (refer to FIG.2), the advantages of trans-mission controlling section 520, selecting section 565and comparing section 563 are different, and the advan-tages of other components are almost the same. Further-more, the communicating party of terminal apparatus 500has the same basic configuration as transmitting appa-ratus 200 (refer to FIG. 3). Thus, only the difference ofthe transmitting apparatus according to the present em-bodiment will be described, and the same configurationwill be omitted.[0105] In terminal apparatus 500 shown in FIG.7, atransmission signal is first stored in transmission control-ling section 520 and then inputted to modulating and en-coding section 125 at the transmission time. Here, trans-mission controlling section 520 controls transmission ofthe transmission rate request signals and retransmissionrequest signals based on the selection result of whetherthe transmission rate request signals, which are inputtedfrom selecting section 565, are inputted to the transmis-sion controlling section, corresponding to all antennas orcorresponding to one antenna.[0106] Next, modulating and encoding section 125 per-forms modulating and encoding processing on the trans-

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mission data inputted from transmission controlling sec-tion 520 and outputs the result to transmitting section132. Transmitting section 132 converts to a radio fre-quency band the frequency of the transmission signalsubjected to modulating and encoding processing, out-puts the converted signal to transmitting antenna 134and transmits the result to the communicating partythrough transmitting antenna 134.[0107] When terminal apparatus 500 receives trans-mission data from the communicating party (for example,a base station having the configuration of transmittingapparatus 200 shown in FIG.3), terminal apparatus 500performs the following operation.[0108] The data transmitted from the base station isreceived by receiving antennas 140 and 150, and con-verted to a baseband signal by receiving sections 142and 152. The transmission data converted to a basebandsignal is outputted to interference compensating section160 and subjected to interference compensation by in-terference compensating section 160. Thus, interferencecompensating section 160 obtains the data transmittedper transmitting antenna of the communicating party.Then, the data outputted from interference compensatingsection 160 is outputted to P/S converting section 164,is subjected to P/S conversion, is outputted to transmis-sion rate request generating sections 144 and 154 andis subjected to quality estimation per transmitting anten-na of the base station, and quality estimation results in-cluding the transmission rate request signal of eachtransmitting antenna are calculated.[0109] The P/S converted data in P/S converting sec-tion 164 is subjected to decoding processing by decodingsection 166. In decoding section 166, when there is anerror in the received signal, data including a retransmis-sion request signal is outputted to S/P converting section168. Furthermore, the retransmission request signal isextracted by S/P converting section 168 and inputted totransmission controlling section 520.[0110] On the other hand, quality estimation is per-formed per transmitting antenna of the communicatingparty by transmission rate request generating sections144 and 154, and the estimation results are outputted toselecting section 565. Further, the quality estimation re-sults by transmission rate request generating sections144 and 154 are outputted to comparing section 563 andcompared. The comparison result calculated in compar-ing section 563 is outputted to selecting section 565 asinformation indicating from which antenna the communi-cating party performs transmission. Then, selecting sec-tion 565 selects, based on the input information, whetherto input the transmission rate request signals to trans-mission controlling section 520 corresponding to all an-tennas or corresponding to one antenna having goodquality.[0111] Now, the configuration of the communicatingparty of terminal apparatus 500 of Embodiment 4 will bedescribed.[0112] The base station, which is the communicating

party of terminal apparatus 500 of Embodiment 4, hasthe same configuration as transmitting apparatus 200 (re-fer to FIG.3). Thus, the base station, which is the com-municating party of terminal apparatus 500 of Embodi-ment 4, will now be described with reference to FIG.3.[0113] In the base station of the present embodiment,when, in the configuration shown in FIG.3, transmissioncontrolling section 260 receives the transmission rate re-quest signal, which is transmitted from the terminal, cor-responding to only one transmitting antenna, transmis-sion controlling section 260 controls the transmissionrates of transmitting antennas 210 and 220 so as to per-form transmission using the same transmission rate. Inthis case, modulating and encoding sections 213 and223 select the same coding rate and modulation scheme.Further, transmission controlling section 260 also con-trols retransmission when a retransmission request sig-nal is reported by terminal apparatus 500 (refer to FIG.7).Then, the transmission data is subjected to modulatingand encoding processing by modulating and encodingsections 213 and 223.[0114] Furthermore, although modulating and encod-ing sections 213 and 223 independently set the codingrate and modulation scheme per transmitting antennas210 and 220 (3GPP TR25,876), modulating and encod-ing sections 213 and 223 select the same coding rateand modulation scheme when the transmission rate re-quest signal, which is transmitted from terminal appara-tus 500, corresponds to one transmitting antenna only.Then, the frequency of the encoded and modulated trans-mission signal is converted to a radio frequency band bytransmitting sections 215 and 225, and transmittedthrough transmitting antennas 210 and 220. Here, whenthe quality (channel quality) difference between transmit-ting antennas 210 and 220 is large and terminal appara-tus 500 transmits the transmission rate request signalcorresponding to only one antenna, data is transmittedonly from the transmitting antenna having good quality,and no data is transmitted from the other transmittingantenna having poor quality.[0115] Here, when the base station performs transmis-sion only from one antenna having good quality, methodsof selecting from which antenna transmission is per-formed, may include, for example, using the transmissionrate request signals, which are transmitted from the ter-minal upon previous transmission corresponding to allantennas and selecting from which antenna transmissionis performed. That is, in the previous transmission raterequest signals, when first transmitting antenna 210 hasa larger transmission rate request value, transmission isperformed from only first transmitting antenna 210, andwhen second transmitting antenna 220 has a largertransmission rate request value, transmission is per-formed from only second transmitting antenna 220. How-ever, the selection method is not limited to this.[0116] Next, FIG.8 illustrates operation of a systemhaving terminal apparatus 500 will be described. FIG. 8is a flowchart of a communication system having com-

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munication apparatus (terminal apparatus) 500 accord-ing to Embodiment 4 of the present invention.[0117] First, in step S21, terminal apparatus 500 (referto FIG.7) receives transmission signals from a base sta-tion, which is a communicating party, through receivingantennas 140 and 150, and the flow proceeds to stepS22.[0118] To be more specific, in step S21, in terminalapparatus 500, the received signals received through re-ceiving antennas 140 and 150 are converted to basebandsignals by receiving sections 142 and 152, subjected tointerference compensation processing by interferencecompensating section 160 and transmitted from thetransmitting antennas of the communicating party.[0119] In terminal apparatus 500, by using the trans-mission data from interference compensating section160, transmission rate request generating sections 144and 154 perform channel quality estimation per antenna(for example, per first and second transmitting antennas210 and 220 shown in FIG.3) of the communicating party,and generate a transmission rate request signal of eachantenna.[0120] In step S22, terminal apparatus 500 determineswhether or not the difference of the generated transmis-sion rate request signals (transmission rate request val-ue) is larger than a threshold value. The flow proceedsto step S23 when the difference is equal to or smallerthan the threshold value, and the flow proceeds to stepS24 when the difference is larger than the threshold val-ue.[0121] To be more specific, comparing section 563 ofterminal apparatus 500 calculates the difference be-tween the transmission rate request values inputted fromtransmission rate request generating sections 144 and154, compares the difference of the calculated transmis-sion rate request value with a threshold value and deter-mines whether the difference is larger or smaller than thethreshold value (here, whether or not the difference islarger than the threshold value). Based on this determi-nation, comparing section 563 outputs to selecting sec-tion 565 information indicating from which antenna thecommunicating party performs transmission. Comparingsection 563 proceeds to step S23 or step S24 based oninformation outputted to selecting section 565.[0122] In step S23, terminal apparatus 500 transmitsthe transmission rate request values of all transmittingantennas of the communicating party to the communi-cating party (for example, transmitting apparatus 200),and the flow proceeds to step S25.[0123] To be more specific, in step S23, informationinputted from comparing section 563 is transmitted fromall antennas of the communicating party, and outputtedto selecting section 565. Based on information indicatingthat the transmission rate requests corresponding to allantennas are transmitted, selecting section 565 selectsall transmission rate request values inputted from trans-mission rate request generating sections 144 and 154,and outputs the selection result to transmission control-

ling section 520. Through modulating and encoding sec-tion 125, transmitting section 132 and transmitting an-tenna 134, transmission controlling section 520 transmitsto transmitting apparatus 200 the transmission rate re-quest values of all antennas (here, first and second trans-mitting antennas 210 and 220 shown in FIG.3) based onthe information from selecting section 565, and the flowproceeds to step S25.[0124] On the other hand, in step S24, terminal appa-ratus 500 compares the transmission rate request valuesof the antenna (for example, first and second transmittingantennas 210 and 220) of the communicating party. Tobe more specific, in step S24, comparing section 563compares the transmission rate request values of firsttransmitting antenna 210 and second transmitting anten-na 220 and determines whether or not quality of firsttransmitting antenna 210 is better. The flow proceeds tostep S26 when quality of first transmitting antenna 210is better, and the flow proceeds to step S27 when qualityof second transmitting antenna 220 is better.[0125] To be more specific, in step S24, selecting sec-tion 565 of terminal apparatus 500 receives as input fromcomparing section 563 information indicating from whichantenna the communicating party performs transmis-sion, that is, information indicating an antenna having thebest quality. Then, based on information from comparingsection 563, selecting section 565 selects informationinputted from transmission rate request generating sec-tions 144 and 154 (the transmission rate request signalvalues of first and second transmitting antennas 210 and220 of the communicating party), and outputs the selec-tion result to transmission controlling section 520.[0126] To be more specific, selecting section 565 out-puts the transmission rate request value of first transmit-ting antenna 210 to transmission controlling section 520when quality of first transmitting antenna 210 is good,and the flow proceeds to step S26. Selecting section 565outputs the transmission rate request value of secondtransmitting antenna 210 to transmission controlling sec-tion 520 when quality of second transmitting antenna 220is good, and the flow proceeds to step S27.[0127] In step S26, in terminal apparatus 500, trans-mission controlling section 520 transmits to the base sta-tion, which is the communicating party (to be more spe-cific, transmitting apparatus 200), the transmission raterequest value of first transmitting antenna 210 of trans-mitting apparatus 200 based on information from select-ing section 565, and the flow proceeds to step S28.[0128] In step S27, in terminal apparatus 500, trans-mission controlling section 520 transmits to the base sta-tion which is the communicating party (here, transmittingapparatus 200), the transmission rate request value of apredetermined antenna (here, second transmitting an-tenna 220) of the base station (transmitting apparatus200) based on information from selecting section 565,and the flow proceeds to step S28.[0129] After processing of the above steps S21 to S23,S27 and S28 in terminal apparatus 500, the transmission

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signal that is transmitted from terminal apparatus 500through these steps and includes the transmission raterequest values is received by the base station and is sub-jected to processing of step S25 and step S28. When thebase station has the same configuration as transmittingapparatus 200 (refer to FIG.3), the base station (trans-mitting apparatus 200) receives the transmission signalfrom terminal apparatus 500 through receiving antenna240. Then, through receiving section 243, demodulatingsection 245, decoding section 247 and S/P convertingsection 249, the base station obtains the transmissionrate request values, and the processing of step S25 andstep S28 is performed.[0130] That is, in step S25, upon reception of the trans-mission rate request values of all transmitting antennasfrom terminal apparatus 500, the base station (transmit-ting apparatus 200 shown in FIG. 3) independently setsthe transmission rate for the antennas (first and secondtransmitting antennas 210 and 220) and transmits thesame data. Furthermore, processing in step S25 is thesame as step S5 shown inFIG.4, anddetaileddescriptionthereof will be omitted.[0131] Further, in step S28, the base station havingthe same configuration as transmitting apparatus 200shown in FIG. 3 sets as the transmission rate of all trans-mitting antennas the transmission rate request valuefrom terminal apparatus 500 obtained through receivingantenna 240, receiving section 243, demodulating sec-tion 245, decoding section 247 and S/P converting sec-tion 249, and transmits transmission data at the sametransmission rate. That is, in step S28, the base stationperforms transmission only from the transmitting antennahaving good quality corresponding to the transmissionrate request value transmitted from terminal apparatus500.[0132] Thus, in terminal apparatus 500 according tothe present invention, when the difference between thetransmission rate request values (CQI values) for thecommunicating party (transmitting apparatus 200) isequal to or smaller than a threshold value, the transmis-sion rate request signals of all antennas of the commu-nicating party (transmitting apparatus 200) are transmit-ted. The communicating party (transmitting apparatus200) receiving the transmission rate request signals in-dependently sets the transmission rate per antenna(here, first and second transmitting antennas 210 and220), and performs transmission.[0133] On the other hand, in terminal apparatus 500,when the difference between the transmission rate re-quest values (CQI values) for the communicating party(transmitting apparatus 200) is larger than a thresholdvalue, the transmission rate request signals correspond-ing to less antennas than the total number of antennasof the communicating party (transmitting apparatus 200)are transmitted. The communicatingparty (transmittingapparatus 200) receiving the transmission rate requestsignals sets a transmission rate based on the transmis-sion rate request signals from terminal apparatus 500 for

the requested number of transmitting antennas, andtransmits transmission data. Further, the communicatingparty sets the transmission rate corresponding to thetransmitted transmission rate request value as the sametransmission rate for all antennas, and transmits trans-mission data from all antennas.[0134] To be more specific, in terminal apparatus 500,when it is determined that the difference between trans-mission rate requests is larger than a threshold value andquality of first transmitting antenna 210 is better, terminalapparatus 500 transmits the transmission rate requestsignal of first transmitting antenna 210 to transmitting ap-paratus 200, which is the communicating party. Trans-mitting apparatus 200 sets the reported transmission raterequest value of first transmitting antenna 210 for re-quested first transmitting antenna 210 and transmitstransmission data. Further, the communicating party setsthe transmitted transmission rate request value as thesame transmission rate for all antennas, and transmitstransmission data from all antennas.[0135] Further, in terminal apparatus 500, when it isdetermined that the difference between transmission raterequests is larger than a threshold value and quality ofsecond transmitting antenna 220 is better, terminal ap-paratus 500 transmits the transmission rate request sig-nal of second transmitting antenna 220 to transmittingapparatus 200, whish is the communicating party. Trans-mitting apparatus 200 sets the reported transmission raterequest value of second transmitting antenna 220 for sec-ond transmitting antenna 220, and transmits transmis-sion data. Further, the communicating party sets thetransmission rate corresponding to the transmitted trans-mission rate request value as the same transmission ratefor all antennas, and transmits transmission data from allantennas.[0136] When the difference between the transmissionrate request signals of the transmitting antennas of thecommunicating party (for example, transmitting appara-tus 200 shown in FIG.3) is larger than a predeterminedvalue, terminal apparatus 500 transmits only the trans-mission rate request signal corresponding to one anten-na, so that it is possible to reduce the amount of trans-mission rate request signals without substantially de-creasing uplink transmission efficiency and reduce inter-ference and power consumption.[0137] Thus, terminal apparatus 500 has a communi-cating party having the same configuration as terminalapparatus 100--a plurality of transmitting antennas--, andreceives transmission signals from the communicatingparty of a MIMO communication scheme where a trans-mission rate is set per transmitting antenna. When trans-mission rate request value of each transmission antennareceiving and extracting signals in this way is large, thetransmission rate request signal corresponding to oneantenna is transmitted, and the communicating party per-forms transmission only from an antenna having goodquality. As a result, it is possible to reduce the amountof transmission rate request signals without substantially

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decreasing throughput.[0138] That is, in a communication scheme that adap-tively changes the transmission rate, regardless of a MI-MO communication scheme, information indicating atwhich transmission rate transmission is performed needsto be transmitted to the communicating party.[0139] Particularly, in a MIMO communication schemethat sets a transmission rate per antenna, when informa-tion indicating at which transmission rate transmission isperformed is transmitted to the transmitting apparatus,information and the amount of control signals in downlinkbecome equivalent times of the number of antennas. Incontrast to this, in the present embodiment, when trans-mitting apparatus 200 performs communication using thesame transmission rate at all transmitting antennas, onlythe control information corresponding to one antennaneeds to be transmitted from terminal apparatus 500,which is the communicating party of transmitting appa-ratus 200, so that it is possible to reduce the amount ofcontrol information in downlink without substantially de-creasing the throughput.[0140] In general, when the difference between trans-mission rate request values of the transmitting antennasreceiving and extracting signals from a base station islarge, the data transmission amount that can be trans-mitted from the transmitting antenna of the communicat-ing party having the worst quality is much less than thedata transmission amount that can be transmitted froma transmitting antenna having good quality. In such acase, the throughput does not substantially improve evenif the transmission rate is set independently per antennaand the transmission rate request signals correspondingto all antennas are transmitted to the base station. Con-versely, by transmitting the transmission rate request sig-nals corresponding to all transmitting antennas to thecommunicating party, the amount of transmission raterequest signals becomes equivalent times of the numberof antennas, thereby increasing interference and powerconsumption. For this reason, when the difference be-tween the transmission rate request values per transmit-ting antenna is large, even if the transmission rate requestsignals corresponding to all antennas are transmitted tothe base station, the advantage becomes small, and theproblem becomes substantial. The present embodimentimproves this problem.[0141] Furthermore, although the case has been de-scribed in the present embodiment where the number oftransmitting antennas of transmitting apparatus 200,which is the communicating party of terminal apparatus500, is two, the present invention is not limited to this,and the number of transmitting antennas of the transmit-ting apparatus may be arbitrarily set.[0142] Furthermore, in the present embodiment, whenthe communicating party (for example, a base station) ofterminal apparatus 500 performs transmission only fromone antenna having good quality, methods of selectingfrom which antenna transmission is performed include,for example, selecting from which antenna transmission

is performed using the transmission rate request signalscorresponding to all antennas transmitted from the ter-minal upon previous transmission. That is, in the previoustransmission rate request signals, transmission is per-formed only from first transmitting antenna 210 when firsttransmitting antenna 210 has a larger transmission raterequest value, and transmission is performed only fromsecond transmitting antenna 220 when second transmit-ting antenna 220 has a larger transmission rate requestvalue.[0143] Thus, even if terminal apparatus 500 does notnecessarily reports to the base station information indi-cating whether or not a signal indicating a transmittingantenna is transmitted, the base station can select fromwhich antenna transmission is performed. However, in acommunication system having above terminal apparatus500 and the above transmitting apparatus, when terminalapparatus is moving fast, the channel state upon reportof the previous transmission rate request values maygreatly differ from the channel state upon transmissionat the base station (the communicating party of terminalapparatus 500).[0144] When a signal is transmitted from the base sta-tion under such circumstances, it is not likely to performtransmission from the transmitting antenna having thebest quality, and the throughput decreases.[0145] To prevent a decrease in the throughput undersuch circumstances, a method is effective of transmittinga signal including information indicating the transmittingantenna from the terminal apparatus, and selecting thetransmitting antenna using the information indicating thetransmitting antenna at the base station. A terminal ap-paratus capable of realizing such a method is describedin Embodiment 5.

(Embodiment 5)

[0146] FIG.9 is a block diagram showing the configu-ration of terminal apparatus 600, which is a communica-tion apparatus, according to Embodiment 5 of the presentinvention.[0147] By transmitting to the communicating party in-formation indicating the transmitting antenna of the com-municating party, terminal apparatus 600 can further pre-vent a decrease in the throughput particularly duringhigh-speed movement compared to Embodiment 4.[0148] Terminal apparatus 600 shown in FIG.9 has aconfiguration that removes selecting section 565 from aconfiguration of terminal apparatus 500 of Embodiment4 (refer to FIG. 7) and has basically the same configura-tion. Thus, in terminal apparatus 600 of the present em-bodiment, the different components from terminal appa-ratus 500 (refer to FIG.7) will be described, and othersame components are assigned the same reference nu-merals and will not be described.[0149] In terminal apparatus 600 shown in FIG.9,transmission rate request generating sections 144 and154 output the quality estimation results respectively cor-

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responding to the antennas of the communicating party(including the transmission rate request signal of eachantenna) to comparing section 563 and transmissioncontrolling section 620. Furthermore, the channel qualityestimation method performed by transmission rate re-quest generating sections 144 and 154 is the same asmethods described in Embodiments 1 and 4, and de-scription thereof will be omitted.[0150] Comparing section 563 calculates the differ-ence between the quality estimation results (to be morespecific, transmission rate signals of the transmitting an-tennas) inputted from transmission rate request gener-ating sections 144 and 154, compares the difference be-tween the transmission rate request signal values of theantennas on the transmitting side with a threshold valueand outputs the result to transmission controlling section620. Here, the comparison result calculated by compar-ing section 563 includes information indicating fromwhich transmitting antenna the communicating party thattransmits data to terminal apparatus 100 performs trans-mission.[0151] Transmission controlling section 620 controlstransmission of the transmission signal transmitted to thecommunicating party (transmitting apparatus 200), and,similar to transmission controlling section 120 (refer toFIG.2), stores and outputs the transmission signal tomodulating and encoding section 125 at the transmissiontime.[0152] Further, based on information which is inputtedfrom comparing section 563 and indicates from whichtransmitting antenna the base station, which is the com-municating party, performs transmission, transmissioncontrolling section 620 controls transmission by trans-mitting information indicating corresponding to how manyantennas the transmission rate request signals are trans-mitted to the base station in addition to the transmissionrate request signal.[0153] Further, the configuration of the base stationthat receives a signal fromterminal apparatus 600 differsonly in the operation of each section of transmitting ap-paratus 200 shown in FIG.3, and has basically the sameconfiguration. Thus, the configuration of the base stationof Embodiment 5 will be described with reference toFIG.3.[0154] In the base station (here, transmitting apparatus200 shown in FIG.3), which is a communicating party ofterminal apparatus 600, S/P converting section 249 ex-tracts transmission rate request signals based on infor-mation which is reported by terminal apparatus 600 andindicates corresponding to how many antennas the trans-mission rate request signals are transmitted, and outputsthe extraction result to transmission controlling section260.[0155] According to terminal apparatus 600 havingsuch a configuration, by transmitting information indicat-ing the transmitting antenna of the base station to thebase station, which is the communicating party (for ex-ample, transmitting apparatus 200 shown in FIG.3), it is

possible to set the transmitting antenna and transmissionrate of the transmitting antenna and transmit data at thebase station, based on the transmission rate request val-ue having the best channel quality and information indi-cating corresponding to how many transmitting antennasthe transmission rate request signals are transmitted tothe base station.[0156] As a result, even during high-speed movementof terminal apparatus 600 where the channel state uponreport of the previous transmission rate request valuesubstantially differs from the channel state upon trans-mission, the base station (the communicating party ofterminal apparatus 600) side can transmit data usingtransmitting antennas corresponding to the number oftransmitting antennas requested by terminal apparatus600. It is thereby possible to prevent a decrease in thethroughput.[0157] Furthermore, when the number of transmittingantennas is two, information indicating from which an-tenna the base station performs transmission may beone bit, which is sufficiently small compared to a trans-mission rate request signal (for example, the transmis-sion rate request signal in 3GPP requires 5 bits), so thatthe amount of control information in uplink does not sub-stantially increase.[0158] Further, although the case has been describedin Embodiment 5 where the communicating party of ter-minal apparatus 600, for example, a base station thatperforms MIMO transmission, performs transmission on-ly from one transmitting antenna, the present inventionis not limited to this, and same information may be trans-mitted from a plurality of transmitting antennas. In thiscase, it is not necessary to report information indicatingwhich transmitting antenna has good channel quality tothe communicating party. However, it is preferable to per-form transmission only from one transmitting antenna soas to reduce transmission power at the base station.[0159] The communication apparatus according toEmbodiment 1 of the present invention that transmitstransmission data and transmission rate request signalscorresponding to a plurality of transmitting antennas toa communicating party of a MIMO communicationscheme that transmits different data from the plurality oftransmitting antennas by independently setting a trans-mission rate per transmitting antenna employs a config-uration including: a transmitting section that transmits thetransmission data and the transmission rate request sig-nals; and a controlling section that controls transmissionof signals to be transmitted from the transmitting section,wherein the controlling section transmits, through thetransmitting section, the transmission rate request sig-nals corresponding to less transmitting antennas thanthe plurality of transmitting antennas, based on a com-parison result between a difference between the trans-mission rate request signals of the transmitting antennasof the communicating party and a predetermined value.[0160] According to this configuration, transmissionrate request signals corresponding to less antennas than

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a plurality of antennas are transmitted based on a com-parison result with a predetermined value to a commu-nicating party of a MIMO communication scheme thattransmits different data from the plurality of transmittingantennas by independently setting a transmission rateper transmitting antenna, so that transmission rate re-quest signals transmitted to the communicating party donot become equivalent times of the number of transmit-ting antennas of the communicating party. Thus, it is pos-sible to perform transmission by reducing transmissionrate request signals without substantially decreasingtransmission efficiency, so that it is possible to reduceinterference to other receivers (users) and reduce powerconsumption upon transmission of rate request signals.[0161] The communication apparatus according toEmbodiment 2 of the present invention employs a con-figuration wherein the controlling section compares thedifference between the transmission rate request signalsof the transmitting antennas of the communicating partywith the predetermined value, and, when the differenceis smaller than the predetermined value, transmits thetransmission rate request signals corresponding to lesstransmitting antennas than the plurality of transmittingantennas.[0162] According to this configuration, it is possible toreduce transmission rate request signals without sub-stantially decreasing transmission efficiency upon trans-mission of the transmission rate request signals, and re-duce interference and power consumption.[0163] The communication apparatus according toEmbodiment 3 of the present invention employs a con-figuration wherein the controlling section compares thedifference between the transmission rate request signalsof the transmitting antennas of the communicating partywith the predetermined value, and, when the differenceis larger than the predetermined value, transmits thetransmission rate request signals corresponding to lesstransmitting antennas than the plurality of transmittingantennas.[0164] According to this configuration, it is possible toreduce transmission rate request signals without sub-stantially decreasing transmission efficiency upon trans-mission of the transmission rate request signals, and re-duce interference and power consumption.[0165] The communication apparatus according toEmbodiment 4 of the present invention employs a con-figuration wherein the controlling section transmits thetransmission rate request signal corresponding to onetransmitting antenna out of the plurality of transmittingantennas, based on a comparison result between thedifference between the transmission rate request signalsof the transmitting antennas of the communicating partyand the predetermined value.[0166] According to this configuration, the transmis-sion rate request signal corresponding to one transmit-ting antenna out of the plurality of transmitting antennasis transmitted to a communicating party that transmitstransmission rate request signals, so that it is possible

at the communicating party to reduce the amount of thethroughput upon reception of the transmission rate re-quest signal compared to a case where the transmissionrate request signals corresponding to all transmitting an-tennas are received, and reduce power consumption up-on transmission of the transmission rate request signalcompared to a case where the transmission rate requestsignals corresponding to all transmitting antennas aretransmitted.[0167] The communication apparatus according toEmbodiment 5 of the present invention employs a con-figuration wherein the controlling section compares thedifference between the transmission rate request signalsof the transmitting antennas of the communicating partywith the predetermined value, and, when the differenceis smaller than the predetermined value, transmits onlythe transmission rate request signal having the smallesttransmission rate request value out of the transmissionrate request values at the plurality of transmitting anten-nas.[0168] According to this configuration, it is possible atthe communicating party to set the transmission rate ofthe transmitting antenna based only on the smallesttransmission rate request signal of each transmitting an-tenna, so that it is only necessary to extract the smallesttransmission rate request signal of each transmitting an-tenna from the transmitted signal and it is possible toprevent deterioration of the error rate upon extraction.[0169] The communication apparatus according toEmbodiment 6 of the present invention employs a con-figuration wherein the controlling section transmits, to thecommunicating party, information indicating whether thetransmission rate request signals are transmitted corre-sponding to the number of transmitting antennas of thecommunicating party or corresponding to only one trans-mitting antenna of the communicating party.[0170] According to this configuration, in received da-ta, the communicating party can perform detection uponextraction of transmission rate request signals based oninformation indicating whether the transmission rate re-quest signals are transmitted corresponding to thenumber of transmitting antennas of the communicatingparty or corresponding to only one transmitting antennaof the communicating party, so that it is possible to furtherreduce false detection of transmission rate request sig-nals by the communicating party compared to the em-bodiment having the above configuration.[0171] The communication apparatus of Embodiment7 of the present invention employs a configuration where-in the predetermined value is variable.[0172] According to this configuration, when transmis-sion rate request signals are transmitted, it is possible tofurther reduce interference to other communication ap-paratuses (users) compared to a case where a commu-nication apparatus of the above configuration is used.[0173] The communication apparatus according toEmbodiment 8 of the present invention employs a con-figuration wherein the controlling section transmits only

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the transmission rate request signal having the largesttransmission rate request value when the difference be-tween the transmission rate request signals of the trans-mitting antennas of the communicating party is largerthan the predetermined value.[0174] According to this configuration, the communi-cating party can further prevent error rate deteriorationcompared to a case where the communicating party re-ceives transmission rate request signals from a commu-nication apparatus having the above configuration.[0175] The communication apparatus according toEmbodiment 9 of the present invention employs a con-figuration wherein the controlling section transmits to thecommunicating party information indicating a transmit-ting antenna at which a transmission rate is set corre-sponding to the transmission rate request signals to betransmitted to the communicating party.[0176] According to this configuration, based on infor-mation indicating the transmitting antenna at which atransmission rate corresponding to transmission rate re-quest signals is set, the communicating party performstransmission after setting a transmission rate at prede-termined antennas, so that it is possible to transmit datafrom a plurality of transmitting antennas at the transmis-sion rate desired by the communication apparatus andfurther prevent a decrease in the throughput during high-speed movement compared to the communication ap-paratus of the above configuration.[0177] The communication method according to Em-bodiment 10 of the present invention of transmittingtransmission data and transmission rate request signalscorresponding to a plurality of transmitting antennas toa communicating party that transmits different data fromthe plurality of transmitting antennas by independentlysetting a transmission rate per transmitting antenna in-cludes: a transmission step of transmitting the transmis-sion data and the transmission rate request signals; anda control step of controlling transmission of signals to betransmitted from the transmission step, wherein, the con-trol step transmits the transmission rate request signalscorresponding to less transmitting antennas than the plu-rality of transmitting antennas, based on a comparisonresult between a difference between the transmissionrate request signals of the transmitting antennas of thecommunicating party and a predetermined value.[0178] According to this configuration, when the trans-mission rate request signals are transmitted to the com-municating party employing a MIMO communicationscheme, it is not necessary to transmit the transmissionrate request signals corresponding to all transmitting an-tennas of the communicat ingparty, so that it is possibleto reduce the transmission rate request signals withoutsubstantially decreasing transmission efficiency and re-duce interference and power consumption.[0179] The present application is based on JapanesePatent Application No.2005-21681, filed on January 28,2005, the entire content of which is expressly incorporat-ed by reference herein.

Industrial Applicability

[0180] The communication apparatus and communi-cation method of the present invention can reduce trans-mission rate request signals and perform transmissionwithout substantially reducing transmission efficiency,have the effect of reducing interference and power con-sumption upon transmission of transmission rate requestsignals and are useful for transmitting data in a MIMOcommunication scheme.[0181] A first example is a communication apparatusthat transmits transmission data and transmission raterequest signals corresponding to a plurality of transmit-ting antennas to a communicating party of a MIMO com-munication scheme that transmits different data from theplurality of transmitting antennas by independently set-ting a transmission rate per transmitting antenna, thecommunication apparatus comprising a transmitting sec-tion that transmits the transmission data and the trans-mission rate request signals, and a controlling sectionthat controls transmission of signals to be transmittedfrom the transmitting section, wherein the controlling sec-tion transmits, through the transmitting section, the trans-mission rate request signals corresponding to less trans-mitting antennas than the plurality of transmitting anten-nas, based on a comparison result between a differencebetween the transmission rate request signals of thetransmitting antennas of the communicating party and apredetermined value.[0182] A second example is the communication appa-ratus according to the first example, wherein the control-ling section compares the difference between the trans-mission rate request signals of the transmitting antennasof the communicating party with the predetermined value,and, when the difference is smaller than the predeter-mined value, transmits the transmission rate request sig-nals corresponding to less transmitting antennas thanthe plurality of transmitting antennas.[0183] A third example is the communication appara-tus according to the first example, wherein the controllingsection compares the difference between the transmis-sion rate request signals of the transmitting antennas ofthe communicating party with the predetermined value,and, when the difference is larger than the predeterminedvalue, transmits the transmission rate request signalscorresponding to less transmitting antennas than the plu-rality of transmitting antennas.[0184] A fourth example is the communication appa-ratus according to the first example, wherein the control-ling section transmits the transmission rate request signalcorresponding to one transmitting antenna out of the plu-rality of transmitting antennas, based on a comparisonresult between the difference between the transmissionrate request signals of the transmitting antennas of thecommunicating party and the predetermined value.[0185] A fifth example is the communication apparatusaccording to the first example, wherein the controllingsection compares the difference between the transmis-

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sion rate request signals of the transmitting antennas ofthe communicating party with the predetermined value,and, when the difference is smaller than the predeter-mined value, transmits only the transmission rate requestsignal having the smallest transmission rate request val-ue out of the transmission rate request values at the plu-rality of transmitting antennas.[0186] A sixth example is the communication appara-tus according to the first example, wherein the controllingsection transmits, to the communicating party, informa-tion indicating whether the transmission rate request sig-nals are transmitted corresponding to the number oftransmitting antennas of the communicating party or cor-responding to only one transmitting antenna of the com-municating party.[0187] A seventh example is the communication ap-paratus according to the first example, wherein the pre-determined value is variable.[0188] An eighth example is the communication appa-ratus according to the first example, wherein the control-ling section transmits only the transmission rate requestsignal having the largest transmission rate request valuewhen the difference between the transmission rate re-quest signals of the transmitting antennas of the commu-nicating party is larger than the predetermined value.[0189] A ninth example is the communication appara-tus according to the first example, wherein the controllingsection transmits to the communicating party informationindicating a transmitting antenna at which a transmissionrate is set corresponding to the transmission rate requestsignals to be transmitted to the communicating party.[0190] A tenth example is a communication method oftransmitting transmission data and transmission rate re-quest signals corresponding to a plurality of transmittingantennas to a communicating party that transmits differ-ent data from the plurality of transmitting antennas byindependently setting a transmission rate per transmit-ting antenna, the communication method comprising atransmission step of transmitting the transmission dataand the transmission rate request signals, and a controlstep of controlling transmission of signals to be transmit-ted from the transmission step, wherein, the control steptransmits the transmission rate request signals corre-sponding to less transmitting antennas than the pluralityof transmitting antennas, based on a comparison resultbetween a difference between the transmission rate re-quest signals of the transmitting antennas of the commu-nicating party and a predetermined value.

Claims

1. A communication apparatus comprising:

a receiving unit configured to receive a pluralityof data transmitted from a plurality of antennasof a communicating party;a generating section configured to generate a

CQI calculated for at least one of the receivedplurality of data;a modulating and encoding section configuredto modulate and encode transmission data in-cluding the CQI; anda transmitting unit configured to transmit thetransmission data to the communicating party;wherein said transmitting unit transmits, to thecommunicating party, information indicating anumber corresponding to a number of CQIs in-cluded in the transmission data.

2. The communication apparatus according to claim 1further comprising a control unit configured to controla transmission of the CQI in said transmitting unit,wherein said control unit control, based on a certaincondition, whether the CQI is transmitted for each ofthe plurality of data or data, a number of which isless than a number of the plurality of data.

3. The communication apparatus according to claim 1or 2, wherein said receiving unit receives the pluralityof data, which are modulated per data in the com-municating party.

4. The communication apparatus according to one ofclaims 1 to 3, wherein said control unit compare adifference between CQIs for the plurality of data witha predetermined value and control the transmissionof the CQI such that the CQI is transmitted for data,a number of which is less than a number of the plu-rality of data when the difference is less than thepredetermined value.

5. The communication apparatus according to one ofclaims 1 to 4, wherein said control unit compare adifference between CQIs for the plurality of data witha predetermined value and control the transmissionof the CQI such that the CQI is transmitted for data,a number of which is less than a number of the plu-rality of data when the difference is greater than thepredetermined value.

6. The communication apparatus according to one ofclaims 1 to 5, wherein said control unit control thetransmission of the CQI based on the certain condi-tion such that the CQI is transmitted for one of theplurality of data.

7. The communication apparatus according to one ofclaims 1 to 6, wherein said control unit compare adifference between CQIs for the plurality of data witha predetermined value and control the transmissionof the CQI such that the minimum or maximum CQIis transmitted among the CQIs for the plurality ofdata when the difference is less than the predeter-mined value.

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8. The communication apparatus according to one ofclaims 1 to 7, wherein said control unit compare adifference between CQIs for the plurality of data witha predetermined value and control the transmissionof the CQI such that the maximum CQI is transmittedamong the CQIs for the plurality of data when thedifference is greater than the predetermined value.

9. A communication method comprising:

receiving a plurality of data transmitted from aplurality of antennas of a communicating party;generating a CQI calculated for at least one ofthe received plurality of data;modulating and encoding transmission data in-cluding the CQI;transmitting the transmission data to the com-municating party; andtransmitting, to the communicating party, infor-mation indicating a number corresponding to anumber of CQIs included in the transmission da-ta.

10. The communication method according to claim 9 fur-ther comprising controlling, based on a certain con-dition, whether the CQI is transmitted for each of theplurality of data or data, a number of which is lessthan a number of the plurality of data.

11. A transmitting apparatus comprising:

a transmitting unit configured to transmit a plu-rality of data from a plurality of antennas to acommunicating party; anda receiving unit configured to receive a CQI,which is calculated for at least one of the pluralityof data and transmitted at the communicatingparty, and receive information indicating anumber corresponding to a number of CQIs in-cluded in transmission data received from thecommunicating party.

12. The transmitting apparatus according to claim 11,wherein said receiving unit receives the CQI, whichis controlled, based on a certain condition, whetherthe CQI is transmitted for each of the plurality of dataor data, a number of which is less than a number ofthe plurality of data and transmitted at the commu-nicating party.

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REFERENCES CITED IN THE DESCRIPTION

This list of references cited by the applicant is for the reader’s convenience only. It does not form part of the Europeanpatent document. Even though great care has been taken in compiling the references, errors or omissions cannot beexcluded and the EPO disclaims all liability in this regard.

Patent documents cited in the description

• JP 2005021681 A [0179]