Patent ID: 12232116

DETAILED DESCRIPTION

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following embodiments, like reference numerals denote like parts, and the redundant description will not be repeated.

Embodiment 1

[Overview of Communication System]

In a communication system including base station100and terminal200which will be described later, communication using uplink unit bands and a plurality of downlink unit bands associated with the uplink unit bands is performed, that is, communication based on asymmetric carrier aggregation specific to terminal200is performed. This communication system also includes a terminal that does not have a function of performing communication based on carrier aggregation and performs communication by one downlink unit band and one uplink unit band associated with the downlink unit band (that is, communication not based on carrier aggregation), unlike terminal200.

Thus, base station100is configured to support both communications based on asymmetric carrier aggregation and communication not based on carrier aggregation.

Communication not based on carrier aggregation may be performed between base station100and terminal200according to resource assignment with respect to terminal200by base station100.

In this communication system, when communication not based on carrier aggregation is performed, the ARQ is performed as in the conventional art, whereas when communication based on carrier aggregation is performed, the channel selection is employed in the ARQ. That is, this communication system is, for example, an LTE-A system, base station100is, for example, an LTE-A base station, and terminal200is, for example, an LTE-A terminal. The terminal having no function of performing communication based on carrier aggregation is, for example, an LTE terminal.

In the following, a description will be made under the premise of the following. That is, asymmetric carrier aggregation specific to terminal200is configured between base station100and terminal200in advance, and information of a downlink unit band and an uplink unit band used by terminal200is shared between base station100and terminal200.

[Configuration of Base Station]

FIG.6is a block diagram illustrating a configuration of base station100according to Embodiment 1 of the present invention. Referring toFIG.6, base station100includes control section101, control information generating section102, coding section103, modulating section104, coding section105, data transmission control section106, modulating section107, mapping section108, IFFT section109, CP adding section110, radio transmitting section111, radio receiving section112, CP removing section113, PUCCH extracting section114, despreading section115, sequence control section116, correlation processing section117, deciding section118, and retransmission control signal generating section119.

Control section101assigns a downlink resource for transmitting control information (that is, a downlink control information assignment resource) and a downlink resource for transmitting downlink data (that is, a downlink data assignment resource) to resource assignment target terminal200. This resource assignment is performed in a downlink unit band included in a unit band group set to resource assignment target terminal200. The downlink control information assignment resource is selected from among resources corresponding to the downlink control channel (PDCCH) in each downlink unit band. Further, the downlink data assignment resource is selected from among resources corresponding to the downlink data channel (PDSCH) in each downlink unit band. Further, when a plurality of resource assignment target terminals200are present, control section101assign different resources to respective resource assignment target terminals200.

The downlink control information assignment resources are equivalent to the above-described L1/L2 CCHs. That is, each of the downlink control information assignment resources is configured with one or more CCEs. Further, the CCEs included in the downlink unit band are associated with component resources of the uplink control channel region (PUCCH region) in an uplink unit band in the unit band group in a one-to-one correspondence manner (that is, an index of each CCE is associated with an index of the PUCCH in a one-to-one correspondence manner). That is, each CCE in a downlink unit band n is associated with a component resource of a PUCCH region n in an uplink unit band in a unit band group in a one-to-one correspondence manner.

Control section101determines a coding rate used to transmit control information to resource assignment target terminal200. Since the amount of data of the control information differs according to this coding rate, control section101assigns downlink control information assignment resources having a number of CCEs to which the control information having this amount of data can be mapped.

Control section101outputs information related to the downlink data assignment resource to control information generating section102. Further, control section101outputs information related to a coding rate to coding section103. Further, control section101decides a coding rate of transmission data (that is, downlink data) and outputs the decided coding rate to coding section105. Further, control section101outputs information related to the downlink data assignment resource and information related to the downlink control information assignment resource, to mapping section108. Here, control section101performs control such that downlink data and downlink control information for the downlink data are mapped to the same downlink unit band.

Control information generating section102generates control information including information related to the downlink data assignment resource, and outputs the generated control information to coding section103. This control information is generated for each downlink unit band. When a plurality of resource assignment target terminals200are present, a terminal ID of a destination terminal is included in the control information so as to discriminate between resource assignment target terminals200. For example, the control information includes a CRC bit masked with the terminal ID of the destination terminal. This control information may be called “downlink assignment control information (control information carrying downlink assignment).”

Coding section103encodes the control information according to the coding rate received from control section101, and outputs the encoded control information to modulating section104.

Modulating section104modulates the encoded control information and outputs the modulated signal to mapping section108.

Coding section105receives transmission data (that is, downlink data) of each destination terminal200and the coding rate information from control section101as input, encodes the transmission data, and outputs the encoded transmission data to data transmission control section106. Here, when a plurality of downlink unit bands are assigned to destination terminal200, each transmission data transmitted through each downlink unit band is encoded, and the encoded transmission data is then output to data transmission control section106.

At the time of first time transmission, data transmission control section106retains the encoded transmission data and also outputs the encoded transmission data to modulating section107. The encoded transmission data is retained for each destination terminal200. Further, transmission data to one destination terminal200is retained for each downlink unit band to transmit. Thus, not only retransmission control of all data to be transmitted to destination terminal200but also retransmission control of each downlink unit band can be performed.

Further, upon receiving NACK or DTX for downlink data transmitted through a certain downlink unit band from retransmission control signal generating section119, data transmission control section106outputs retention data corresponding to the downlink unit band to modulating section107. Upon receiving ACK for downlink data transmitted in a certain downlink unit band from retransmission control signal generating section119, data transmission control section106deletes retention data corresponding to the downlink unit band.

Modulating section107modulates the encoded transmission data received from data transmission control section106, and outputs a modulated signal to mapping section108.

Mapping section108maps the modulated signal of the control information received from modulating section104to a resource represented by the downlink control information assignment resource received from control section101, and outputs a mapping result to IFFT section109.

Further, mapping section108maps the modulated signal of the transmission data received from modulating section107to a resource represented by the downlink data assignment resource received from control section101, and outputs a mapping result to IFFT section109.

The control information and the transmission data mapped to a plurality of sub carriers in a plurality of downlink unit bands by mapping section108are transformed from frequency-domain signals into time-domain signals by IFFT section109, are transformed into OFDM signals with a CP added by CP adding section110, are subjected to a transmission process such as a digital to analog (D/A) conversion process, an amplification process and an up-conversion process by radio transmitting section111, and are transmitted to terminal200through an antenna.

Radio receiving section112receives a response signal or a reference signal transmitted from terminal200through the antenna, and performs a reception process, such as a down-conversion process and an analog to digital (A/D) conversion process, on the response signal or the reference signal.

CP removing section113removes a CP added to the response signal or the reference signal that has been subjected to the reception process.

PUCCH extracting section114extracts PUCCH regions (PUCCH regions respectively corresponding to PUCCH resources) corresponding to M SR resources and N ACK/NACK resources from the PUCCH signal included in the received signal, and sorts the extracted PUCCH signals into processing systems corresponding to the respective resources. Terminal200transmits uplink control information (that is, either or both of the SR and the response signal) using any one of the PUCCH resources.

Despreading section115-xand correlation processing section117-xprocess the PUCCH signal extracted from the PUCCH region corresponding to an x-th PUCCH resource (the SR resource or the ACK/NACK resource. Here, x=1 to (M+N)). Base station100is provided with processing systems of despreading section115and correlation processing section117corresponding to each PUCCH resource x (the SR resource or the ACK/NACK resource. Here, x=1 to (M+N)) used by base station100.

Specifically, despreading section115despreads a signal of a portion corresponding to the response signal using a Walsh sequence which terminal200uses for secondary spreading in each PUCCH resource (the SR resource or the ACK/NACK resource), and outputs the despread signal to correlation processing section117. Further, despreading section115despreads a signal of a portion corresponding to the reference signal using a DFT sequence which terminal200uses for spreading of the reference signal in each PUCCH resource (the SR resource or the ACK/NACK resource), and outputs the despread signal to correlation processing section117.

Sequence control section116generates a ZAC sequence that may be possibly used to spread the response signal and the reference signal transmitted from terminal200. Further, sequence control section116specifies correlation windows that respectively correspond to (M+N) PUCCH resources (SR resources and ACK/NACK resources), based on PUCCH resource which may be possibly used by terminal200. Then, sequence control section116outputs information representing the specified correlation window and the generated ZAC sequences to correlation processing section117.

Correlation processing section117calculates a correlation value between the signal input from despreading section115and the ZAC sequence that may be possibly used for primary spreading in terminal200using the information representing the correlation window and the ZAC sequences input from sequence control section116, and outputs the calculated correlation value to deciding section118.

Deciding section118decides whether or not the SR and the response signal are being transmitted from terminal200, based on the correlation value input from correlation processing section117. That is, deciding section118decides whether or not any of the (M+N) PUCCH resources (SR resources and ACK/NACK resources) is being used by terminal200or whether or not none of the (M+N) PUCCH resources is being used by terminal200.

For example, when it is decided that any one of the M SR resources is being used by terminal200at timing when the terminal200transmits the response signal in response to the downlink data, deciding section118decides that both the SR and the response signal are being transmitted from terminal200. Further, when it is decided that any one of the M SR resources (or a predetermined one SR resource) is being used by terminal200at timing other than timing when the terminal200transmits the response signal in response to the downlink data, deciding section118decides that only the SR is being transmitted from terminal200. Further, when it is decided that any of the N ACK/NACK resources is being used by terminal200, deciding section118decides that only the response signal is being transmitted from terminal200. Further, when it is decided that none of the resources is being used by the terminal, deciding section118decides that neither the SR nor the response signal is being transmitted from terminal200.

In addition, when it is decided that terminal200is transmitting the SR, deciding section118outputs information related to the SR to an uplink resource assignment control section (not illustrated). Further, when it is decided that terminal200is transmitting the response signal, deciding section118decides a phase point represented by the response signal through synchronization detection. In detail, deciding section118first determines a PUCCH resource from which a maximum correlation value has been detected among PUCCH resources corresponding to correlation processing sections117-1to117-(M+N). Next, deciding section118specifies a phase point of the response signal transmitted through the PUCCH resource from which the maximum correlation value has been detected, and specifies a reception status pattern that corresponds to the PUCCH resource, the specified phase point, and the number of downlink unit bands through which its own station has transmitted downlink data to terminal200. Then, deciding section118individually generates an ACK signal or a NACK signal on data transmitted in each downlink unit band based on the specified reception status pattern, and outputs the ACK signal or the NACK signal to retransmission control signal generating section119. Here, when all of correlation values obtained corresponding to the respective PUCCH resources are equal to or smaller than a specific threshold value, deciding section118decides that non response signal has been transmitted from terminal200, generates DTX for all downlink data, and outputs the DTX to retransmission control signal generating section119.

Further, when the uplink resource assignment control section (not illustrated) receives the SR, base station100transmits the uplink assignment control information (which may be also referred to as “uplink grant”) that notifies an uplink data assignment resource, to terminal200so that terminal200can transmit uplink data. Thus, base station100decides whether or not a resource for uplink data needs to be assigned to terminal200, based on the uplink control channel. The details of an operation in the uplink resource assignment control section and the details of an operation of base station100of assigning a resource for uplink data to terminal200will not be described.

Retransmission control signal generating section119generates a retransmission control signal for data (downlink data) transmitted at each downlink unit band based on the information input from deciding section118. Specifically, when the response signal representing NACK or the DTX is received, retransmission control signal generating section119generates retransmission control signal representing a retransmission command, and outputs the retransmission control signal to data transmission control section106. Further, when the response signal representing ACK is received, retransmission control signal generating section119generates a retransmission control signal representing that retransmission is not necessary, and outputs the retransmission control signal to data transmission control section106.

[Configuration of Terminal]

FIG.7is a block diagram illustrating a configuration of terminal200according to Embodiment 1 of the present invention. Referring toFIG.7, terminal200includes radio receiving section201, CP removing section202, fast Fourier transform (FFT) section203, extracting section204, demodulating section205, decoding section206, deciding section207, control section208, demodulating section209, decoding section210, CRC section211, response signal generating section212, modulating section213, primary spreading section214, secondary spreading section215, IFFT section216, CP adding section217, and radio transmitting section218.

Radio receiving section201receives an OFDM signal transmitted from base station100through an antenna, and performs a reception process, such as a down-conversion process, an A/D conversion process, on the received OFDM signal.

CP removing section202removes a CP added to the OFDM signal after the reception processing.

FFT section203transforms the received OFDM signal into a frequency domain signal by FFT and outputs the received signal to extracting section204.

Further, extracting section204extracts the downlink control channel signal (the PDCCH signal) from the received signal received from FFT section203according to input coding rate information. That is, since the number of CCEs configuring the downlink control information assignment resource changes depending on the coding rate, extracting section204extracts the downlink control channel signal using the number of CCEs which corresponds to the coding rate as an extraction unit. Furthermore, the downlink control channel signal is extracted for each downlink unit band. The extracted downlink control channel signal is output to demodulating section205.

Further, extracting section204extracts downlink data from the received signal based on the information related to the downlink data assignment resource, which is addressed to its own terminal, received from deciding section207, and outputs the extracted downlink data to demodulating section209.

Demodulating section205demodulates the downlink control channel signal received from extracting section204, and outputs the obtained demodulation result to decoding section206.

Decoding section206decodes the demodulation result received from demodulating section205according to the input coding rate information, and outputs the obtained decoding result to deciding section207.

Deciding section207makes a blind decision as to whether or not control information included in the decoding result received from decoding section206is control information addressed to its own terminal. This decision is made using the decoding result corresponding to the extraction unit as a unit. For example, deciding section207demasks a CRC bit using the terminal ID of its own terminal, and decides control information with CRC=OK (no error) as the control information addressed to its own terminal. Then, deciding section207outputs information related to the downlink data assignment resource for its own terminal, which is included in the control information addressed to its own terminal, to extracting section204.

Further, deciding section207specifies each CCE to which the control information addressed to its own terminal is mapped in the downlink control channel of each downlink unit band, and outputs an identification number (that is, CCE index) of the specified CCE to control section208.

Control section208specifies a PUCCH resource (frequency/code) corresponding to the CCE to which the downlink control information received at an n-th (n=first to N-th) unit band is mapped, that is, a PUCCH resource n (That is, an ACK/NACK resource n) in a PUCCH region n, based on the CCE identification number received from deciding section207. Then, control section208decides a PUCCH resource to be used to transmit the response signal, among the specified N ACK/NACK resources and the M SR resources previously notified from base station100.

Specifically, control section208decides a PUCCH resource to be used and a phase point to be set so as to transmit a signal according to a transmission rule (a mapping rule) of the response signal, which will be described later, based on the generation status information of the SR received from an uplink data generating section (not illustrated) and an error detection result (that is, a reception success/failure pattern) of downlink data at each downlink unit band received from CRC section211.

Then, control section208outputs information related to the phase point to be set, to response signal generating section212, outputs the ZAC sequence and the cyclic shift index corresponding to the PUCCH resources to be used to primary spreading section214and outputs frequency resource information to IFFT section216. Here, when there is no response signal to be transmitted through the sub frame having received the SR from the uplink data generating section (that is, when the downlink assignment control information is not detected at all), control section208instructs response signal generating section212to output “NACK” to modulating section213. Further, control section208outputs a Walsh sequence and a DFT sequence corresponding to the PUCCH resources to be used to secondary spreading section215. The details of control on the PUCCH resource and the phase points by control section208will be described later.

Demodulating section209demodulates the downlink data received from extracting section204, and outputs the demodulated downlink data to decoding section210.

Decoding section210decodes the downlink data received from demodulating section209, and outputs the decoded downlink data to CRC section211.

CRC section211generates the decoded downlink data received from decoding section210, and performs error detection for each downlink unit band using a CRC. Then, CRC section211outputs ACK to control section208when CRC=OK (no error), but outputs NACK to control section208when CRC=NG (error). Further, when CRC=OK (no error), CRC section211outputs the decoded downlink data as received data.

Response signal generating section212generates the response signal and the reference signal based on the phase point of the response signal instructed from control section208, and outputs the response signal and the reference signal to modulating section213.

Modulating section213modulates the response signal and the reference signal input from response signal generating section212, and outputs the modulated response signal and the modulated reference signal to primary spreading section214.

Primary spreading section214performs primary-spreading on the response signal and the reference signal based on the ZAC sequence and the cyclic shift index set by control section208, and outputs the primary-spread response signal and the primary-spread reference signal to secondary spreading section215. That is, primary spreading section214performs primary-spreading on the response signal and the reference signal according to an instruction from control section208. Here, “spreading” specifically means multiplying the response signal represented by information of one symbol by the ZAC sequence.

Secondary spreading section215performs secondary-spreading on the response signal and the reference signal using a Walsh sequence and a DFT sequence set by control section208, and outputs the secondary-spread signal to IFFT section216. That is, secondary-spreading section215performs secondary-spreading on the primary-spread response signal and the primary-spread reference signal using the Walsh sequence and the DFT sequence corresponding to the PUCCH resources selected by control section208, and outputs the spread signal to IFFT section216. That is, secondary spreading section215multiplies the response signal and the reference signal which have been subjected to primary spreading by a component of the Walsh sequence or a component of the DFT sequence.

CP adding section217adds the same signal as the tail part of the signal which has been subjected to IFFT, to the head of the signal as a CP.

Radio transmitting section218performs transmission processing, such as a D/A conversion process, an amplification process, and an up-conversion process, on the input signal. Then, radio transmitting section218transmits the signal to base station100through the antenna.

[Operation of Terminal200]

An operation of terminal200having the above configuration will be described.

<Reception of Downlink Assignment Control Information and Downlink Data by Terminal200>

Terminal200makes a blind decision as to whether or not downlink assignment control information addressed to its own terminal has been transmitted for each sub frame in all downlink unit bands of a unit band group set to its own terminal.

Specifically, deciding section207decides whether or not the downlink assignment control information addressed to its own terminal is included in the downlink control channel of each downlink unit band. Then, when it is decided that the downlink assignment control information addressed to its own terminal is included, deciding section207outputs the downlink assignment control information to extracting section204. Further, deciding section207outputs the identification information of the downlink unit band in which the downlink assignment control information addressed to its own terminal has been detected, to control section208. Thus, control section208is notified of the downlink unit band in which the downlink assignment control information addressed to its own terminal has been detected.

Extracting section204extracts downlink data from the received signal based on the downlink assignment control information received from deciding section207. Extracting section204extracts the downlink data from the received signal based on the resource information included in the downlink assignment control information.

For example, downlink assignment control information transmitted at downlink unit band1includes information related to a resource used for transmission of downlink data (DL data) transmitted at downlink unit band1, and downlink assignment control information transmitted at downlink unit band2includes information related to a resource used for transmission of downlink data transmitted at downlink unit band2.

Thus, terminal200can receive downlink data at both downlink unit band1and downlink unit band2by receiving the downlink assignment control information transmitted at downlink unit band1and the downlink assignment control information transmitted at downlink unit band2. On the other hand, when the terminal is difficult to receive the downlink assignment control information at a certain downlink unit band, terminal200is difficult to receive downlink data at the corresponding downlink unit band.

<Transmission of Response and SR by Terminal200>

CRC section211performs error detection on downlink data corresponding to the successfully received downlink assignment control information, and outputs an error detection result to control section208.

Then, control section208performs transmission control of the response signal as follows, based on the generation status of the SR received from the uplink data generating section (not illustrated) and the error detection result received from CRC section211.FIGS.8and9are diagrams for describing a method of transmitting an SR and a response signal through terminal200when two downlink unit bands are set to terminal200.FIGS.10and11are diagrams for describing a method of transmitting an SR and a response signal through terminal200when three downlink unit bands are set to terminal200.

<Transmission of Response and SR by Terminal200: When There are Two Downlink Unit Bands>

A description will be made below in connection with an example in which two downlink unit bands (downlink unit bands1and2) are set to terminal200. Here, an ACK/NACK resource (PUCCH resource) associated with a downlink control information assignment resource used for downlink assignment control information for downlink data transmitted in downlink unit band1is defined as ACK/NACK resource1. Further, an ACK/NACK resource (PUCCH resource) associated with a downlink control information assignment resource used for downlink assignment control information for downlink data transmitted in downlink unit band2is defined as ACK/NACK resource2.

Further, in the following description, base station100independently notifies terminal200of information related to a resource (an SR resource illustrated inFIG.8A) for transmitting an SR in an uplink unit band illustrated inFIG.4(an uplink unit band set to terminal200). That is, control section208of terminal200retains information related to an SR resource notified from base station100through a separate signaling unit (for example, higher layer signaling).

Further, terminal200specifies an ACK/NACK resource associated with a CCE, which is occupied by downlink assignment control information received by its own terminal, among a plurality of CCEs configuring PDCCHs of downlink unit bands1and2, as ACK/NACK resource1or2.

Here, inFIG.8A, an SR resource and ACK/NACK resources1and2are different code resources from each other that at least one of a ZAC sequence (primary spreading) or a Walsh sequence/DFT sequence is different.

An operation of terminal200at this time is described in detail with reference toFIGS.9A and9B. Here, ACK/NACK resources1and2illustrated inFIG.9Aand an SR resource illustrated inFIG.9Bcorrespond to ACK/NACK resources1and2and an SR resource illustrated inFIGS.8A to8D, respectively. Further, inFIGS.9A and9B, “A” represents ACK, “N” represents NACK, and “D” represents DTX. InFIGS.9A and9B, for example, “A/N” represents a state in which a response signal corresponding to downlink unit band1(CC1) is ACK but a response signal corresponding to downlink unit band2(CC2) is NACK. Further, “N/D” represents a state in which a response signal corresponding to downlink unit band1(CC1) is NACK and it was difficult to detect downlink assignment control information corresponding to downlink data transmitted in downlink unit band2(CC2) (that is, DTX corresponding to downlink unit band2(CC2)). Further, inFIG.9B, for example, “SR+A/N” represents a state in which “A/N” is transmitted using an SR resource. At this time, base station100detects an SR from terminal200side based on whether or not the SR resource is being used, and determines that a response signal is “A/N” based on a phase point to which the signal is mapped.

First, when terminal200transmits only the response signal (“when only response signal is transmitted” illustrated inFIG.8B), terminal200performs an operation of the channel selection using ACK/NACK resources1and2associated with CCEs occupied by downlink assignment control information corresponding to downlink data transmitted in downlink unit bands1and2as illustrated inFIG.9A. Specifically, control section208of terminal200transmits the response signal using a transmission rule (a mapping rule) of the response signal illustrated inFIG.9A, based on a pattern (state) as to whether or not downlink data addressed to its own terminal, which correspond to downlink assignment control information and have been transmitted in downlink unit bands1and2, have been successfully received (error detection result).

Here, it should be noted that states (D/A and D/N) in which DTX has been generated for downlink unit band1(CC1) are all notified by the phase point of ACK/NACK resource2other than ACK/NACK resource1illustrated inFIG.9A. This is because when terminal200did not detect downlink assignment control information corresponding to downlink data in downlink unit band1(that is, in case of DTX), it is difficult to specify ACK/NACK resource1to be used at terminal200side. Similarly, states (A/D and N/D) in which DTX has been generated on downlink unit band2(CC2) are all notified by the phase point of ACK/NACK resource1, not by ACK/NACK resource2illustrated inFIG.9A. This is because when terminal200did not detect downlink assignment control information corresponding to downlink data in downlink unit band2(that is, in case of DTX), it is difficult to specify ACK/NACK resource2to be used at terminal200side. As described above, in the ACK/NACK resource, there is a limitation to a resource which can be used to notify a state in which DTX has been generated.

InFIG.9A, if all of three states (N/D, D/N, and N/N) in which all is NACK or DTX can be notified through the same resource and at the same phase point, a total of four phase points become necessary to notify all states (8 states illustrated inFIG.9A(a total of 8 reception success/failure patterns). That is, any one of the two ACK/NACK resources illustrated inFIG.9Amay be reduced. However, due to the limitation of the ACK/NACK resource, when terminal200transmits only the response signal as illustrated inFIG.8B, two ACK/NACK resources1and2(that is, resources the number of which is equal to the number of downlink unit bands set to terminal200) become necessary.

On the other hand, when terminal200simultaneously transmits the SR and the response signal in the same sub frame (“when SR and response signal are transmitted” illustrated inFIG.8C), terminal200transmits the response signal using the SR resource notified from base station100by a separate signaling technique as illustrated inFIG.9B. Specifically, control section208of terminal200transmits the response signal using the transmission rule (the mapping rule) of the response signal illustrated inFIG.9Bbased on the pattern (state) as to whether or not downlink data corresponding to downlink assignment control information addressed to its own terminal has been successfully received (error detection result).

Here, a description will be made in connection with the transmission rule (mapping rule) (FIG.9B) of the response signal used when the SR and the response signal have been simultaneously generated in the same sub frame (“when SR and response signal are transmitted” illustrated inFIG.8C).

InFIG.9B, when all of two pieces of downlink assignment control information and downlink data transmitted in downlink unit bands1and2corresponding to the respective downlink assignment control information have been successfully received, a phase point (−1, 0) is used. That is, inFIG.9B, “A/A” is associated with the phase point (−1, 0) of the SR resource.

Further, when, of downlink data of downlink unit bands1and2corresponding to the two pieces of downlink assignment control information, downlink data of downlink unit band1has been successfully received but downlink data of downlink unit band2has been failed in reception, a phase point of (0, −j) is used. That is, inFIG.9B, “A/N” and “A/D” are associated with the phase point (0, −j) of the SR resource.

Further, when, of downlink data of downlink unit bands1and2corresponding to the two pieces of downlink assignment control information, downlink data of downlink unit band1has been failed in reception but downlink data of downlink unit band2has been successfully received, a phase point of (0, j) is used. That is, inFIG.9B, “N/A” and “D/A” are associated with the phase point (0, j) of the SR resource.

Further, when none of downlink data of downlink unit bands1and2corresponding to the two pieces of downlink assignment control information have been received, a phase point of (1, 0) is used. That is, inFIG.9B, “N/N”, “D/N”, and “N/D” are associated with the phase point (1, 0) of the SR resource.

That is, in the transmission rule (mapping rule) illustrated inFIG.9B(when the SR and the response signal have been simultaneously generated in the same sub frame), a reception success/failure (error detection result) pattern candidate is associated with the phase point of the response signal in the SR resource, and different phase points in the SR resource are associated with pattern candidate groups which differ in at least one of the number of ACKs included in the pattern and the position of ACK (that is, the downlink unit band to which successfully received downlink data is assigned) in the pattern. That is, inFIG.9B, the reception success/failure (error detection result) pattern candidate is associated with the phase point of the response signal in the SR resource, different phase points in the SR resource are associated with pattern candidate groups which differ in the number of ACKs included in the pattern, and different phase points in the SR resource are associated with pattern candidate groups which are equal in the number of ACKs included in the pattern but differ in the position of ACK (that is, the downlink unit band to which successfully received downlink data is assigned) in the pattern. Thus, even in the case in which all downlink data corresponding to the detected downlink assignment control information have been successfully received, when the number of successfully received downlink data (the number of ACKs) is different or when the downlink unit band to which successfully received downlink data has been assigned (the position of ACK) is different even though the number of successfully received downlink data (the number of ACKs) is the same, different phase points in the SR resource are used for the response signal.

For example, inFIG.9B, when downlink data has been successfully received in all of downlink unit bands (“A/A”), the phase point (−1, 0) is used. Further, when downlink data has been successfully received in downlink unit band1but downlink data has failed in reception in downlink unit band2(“A/N” and “A/D”), the phase point (0, −j) is used. Further, when downlink data has failed in reception in downlink unit band1but downlink data has been successfully received in downlink unit band2(“N/A” and “D/A”), the phase point (0, j) is used. Further, when downlink data has not been received in all of downlink unit bands (“N/N”, “D/N”, and “N/D”), the phase point (−1, 0) is used.

Here, the SR resource illustrated inFIG.9Bis notified by a separate signaling technique (for example, higher layer signaling) from base station100to terminal200. Thus, inFIG.9B(“when SR and response signal are transmitted” illustrated inFIG.8C), there is no limitation as inFIG.9A(“when only response signal is transmitted” illustrated inFIG.8B), and all of the three states “N/D”, “D/N”, and “N/N” can be associated with the same resource and the same phase point (here, the phase point (1, 0)). Thus, inFIG.9B, a total of 4 phase points are necessary for notifying all states (a total of 8 states illustrated inFIG.9B(8 reception success/failure patterns)).

That is, inFIG.9A, due to the limitation, a total of 5 phase points are necessary for notifying all states (reception success/failure patterns), and two ACK/NACK resources are necessary for notifying the response signals of downlink unit bands1and2. On the other hand, inFIG.9B, a single SR resource (PUCCH resource) may be used to simultaneously notify the SR and the response signals of downlink unit bands1and2.

As described above, when terminal200simultaneously transmits the SR and the response signal, mapping illustrated inFIG.9Bis used. Thus, even when the channel selection is applied as a method of transmitting the response signal, the number of SR resources can be reduced. For example, whenFIG.5Ais compared withFIG.8A, four PUCCH resources (SR resources and ACK/NACK resources) are necessary inFIG.5A, whereas three PUCCH resources (SR resources and ACK/NACK resources) are necessary inFIG.8A. That is, inFIG.8A, one PUCCH resource is deleted compared toFIG.5A, thus an increase in the overhead of the uplink control channel (PUCCH) can be suppressed.

InFIG.9B, it should be noted that a case (“A/A” illustrated inFIG.9B) in which all response signals to downlink unit bands1and2at terminal200side are ACK and cases (“N/N”, “D/N”, and “N/D” illustrated inFIG.9B) in which all response signals to downlink unit bands1and2at terminal200side are NACK or DTX are associated with phase points farthest from each other, among phase points (4 phase points) which can be selected by the reception success/failure (error detection result) pattern candidate group.

That is, inFIG.9B, the states (the reception success/failure pattern candidate group) of the response signals notified using adjacent phase points (that is, phase points having a phase difference of 90° (π/2 radians)) in the SR resource are different from each other only in the reception status in one downlink unit band. For example, in the SR resource illustrated inFIG.9B, the state “A/A” notified using the phase point (−1, 0) and the states “N/A” and “D/A” notified using the phase point (0, j) (having a phase difference of 90° with the phase point (−1, 0)) are different from each other only in the reception status of downlink unit band1(CC1). Similarly, in the SR resource illustrated inFIG.9B, the state “A/A” notified using the phase point (−1, 0) and the states “A/N” and “A/D” notified using the phase point (0, −j) (having a phase difference of 90° with the phase point (−1, 0)) are different from each other only in the reception status of downlink unit band2(CC2). This is similarly applied to the other phase points.

As a result, even when the phase point is erroneously decided, base station100side (deciding section118) can suppress the number of unit bands erroneous in a retransmission control to a minimum, thereby minimizing degradation in retransmission efficiency.

Further, when terminal200transmits only the SR (“when only SR is transmitted” illustrated inFIG.8D), terminal200transmits the SR using the SR resource separately notified from base station100as illustrated inFIG.9B. At this time, control section208of terminal200transmits the SR using the same phase point (1, 0) as the state (the reception success/failure pattern) in which all is NACK (or DTX), which is illustrated inFIG.9B.

<Transmission of Response and SR by Terminal200: When There are Three Downlink Unit Bands>

The following description will be made in connection with an example in which three downlink unit bands (downlink unit bands1,2, and3) are set to terminal200. Here, an ACK/NACK resource (PUCCH resource) associated with a downlink control information assignment resource used for downlink assignment control information for downlink data transmitted in downlink unit band1is defined as ACK/NACK resource1. Further, an ACK/NACK resource (PUCCH resource) associated with a downlink control information assignment resource used for downlink assignment control information for downlink data transmitted at downlink unit band2is defined as ACK/NACK resource2. Further, an ACK/NACK resource (PUCCH resource) associated with a downlink control information assignment resource used for downlink assignment control information for downlink data transmitted at downlink unit band3is defined as ACK/NACK resource3.

Further, in the following description, base station100separately notifies terminal200of information related to two resources (SR resources1and2illustrated inFIG.10A) for transmitting an SR in an uplink unit band illustrated inFIG.4(an uplink unit band set to terminal200). That is, control section208of terminal200retains information related to SR resources1and2notified from base station100.

Further, terminal200specifies an ACK/NACK resource associated with a CCE, which is occupied by downlink assignment control information received by its own terminal, among a plurality of CCEs configuring PDCCHs of downlink unit bands1,2, and3as ACK/NACK resource1,2, or3.

Here, inFIG.10A, SR resources1and2and ACK/NACK resources1,2, and3are different code resources from each other such that at least one of a ZAC sequence (primary spreading) or a Walsh sequence/DFT sequence is different.

An operation of terminal200at this time is described in detail with reference toFIGS.11A and11B. Here, ACK/NACK resources1,2, and3illustrated inFIG.11Aand SR resources1and2illustrated inFIG.11Bcorrespond to ACK/NACK resources1,2, and3and SR resources1and2illustrated inFIGS.10A to10D, respectively. InFIGS.11A and11B, for example, “A/N/N” represents a state in which a response signal corresponding to downlink unit band1(CC1) is ACK but response signals corresponding to downlink unit band2(CC2) and downlink unit band3(CC3) are NACK. Further, “N/D/D” represents a state in which a response signal corresponding to downlink unit band1(CC1) is NACK and it was difficult to detect downlink assignment control information corresponding to downlink data transmitted in downlink unit band2(CC2) and downlink unit band3(CC3) (that is, DTXs corresponding to downlink unit band2(CC2) and downlink unit band3(CC3)). Further, inFIG.11B, for example, “SR+A/N/N” represents a state in which “A/N/N” is transmitted using an SR resource.

First, when terminal200transmits only the response signal (“when only response signal is transmitted” illustrated inFIG.10B), terminal200performs an operation of the channel selection using ACK/NACK resources1,2, and3associated with CCEs occupied by downlink assignment control information corresponding to downlink data transmitted in downlink unit bands1,2, and3as illustrated inFIG.11A. Specifically, control section208of terminal200transmits the response signal using a transmission rule (a mapping rule) of the response signal illustrated inFIG.11Abased on a pattern (state) as to whether or not downlink data associated with downlink assignment control information corresponding to downlink data addressed to its own terminal, which have been transmitted in downlink unit bands1,2, and3, have been successfully received (error detection result).

Here, it should be noted that states (D/D/A and D/D/N) in which DTXs have been generated for downlink unit band1(CC1) and downlink unit band2(CC2) are all notified by the phase point of ACK/NACK resource3, not by ACK/NACK resources1and2illustrated inFIG.11A. This is because when terminal200did not detect downlink assignment control information corresponding to downlink data transmitted in downlink unit bands1and2(that is, in case of DTX), it is difficult to specify ACK/NACK resources1and2to be used at terminal200side. Similarly, states (A/D/D and N/D/D) in which DTXs have been generated for downlink unit band2(CC2) and downlink unit band3(CC3) are all notified by the phase point of ACK/NACK resource1. States (D/A/D and D/N/D) in which DTXs have been generated for downlink unit band1(CC1) and downlink unit band3(CC3) are all notified by the phase point of ACK/NACK resource2. Further, a state in which DTX has been generated for downlink unit band1is notified by phase points of ACK/NACK resources2and3other than ACK/NACK resource1illustrated inFIG.11A. It is similarly applied to a state in which DTX has been generated for downlink unit bands2and3. As described above, in the ACK/NACK resource, there is a limitation to a resource which can be used to notify a state in which DTX has been generated.

InFIG.11A, if all of seven states (“N/N/N”, “N/N/D”, “N/DN”, “N/D/D”, “D/N/N”, and “D/N/D”) in which all is NACK or DTX can be notified through the same resource and at the same phase point, a total of 8 phase points are necessary to notify all states (a total of 26 states illustrated inFIG.11A(26 reception success/failure patterns)). That is, it is possible to reduce any one of the three ACK/NACK resources illustrated inFIG.11A. However, due to the limitation of the ACK/NACK resource, when terminal200transmits only the response signal as illustrated inFIG.10B, three ACK/NACK resources1,2, and3(that is, resources of which the number is equal to that of downlink unit bands set to terminal200) are necessary.

On the other hand, when terminal200simultaneously transmits the SR and the response signal in the same sub frame (“when SR and response signal are transmitted” illustrated inFIG.10C), terminal200transmits the response signal using the SR resource separately notified from base station100as illustrated inFIG.11B. Specifically, control section208of terminal200transmits the response signal using the transmission rule (the mapping rule) of the response signal illustrated inFIG.11B, based on the pattern (state) as to whether or not downlink data corresponding to downlink assignment control information addressed to its own terminal has been successfully received (error detection result).

Here, a description will be made in connection with the transmission rule (mapping rule) (FIG.11B) of the response signal used when the SR and the response signal have been simultaneously generated in the same sub frame (“when SR and response signal are transmitted” illustrated inFIG.10C).

In the transmission rule (mapping rule) illustrated inFIG.11B(when the SR and the response signal have been simultaneously generated in the same sub frame), a reception success/failure (error detection result) pattern candidate is associated with the SR resource to which the response signal is assigned and the phase point of the response signal, and SR resources and phase points which differ in at least one of the SR resource and the phase point are associated with pattern candidate groups which differ in at least one of the number of ACKs included in the pattern and the position of ACK (that is, the downlink unit band to which successfully received downlink data is assigned) in the pattern. That is, inFIG.11B, the reception success/failure (error detection result) pattern candidate is associated with a pair of the SR resource and the phase point of the response signal, different pairs (pairs of the SR resources and the phase points) are associated with pattern candidate groups which differ in the number of ACKs included in the pattern, and different pairs (pairs of the SR resources and the phase points) are associated with pattern candidate groups which are equal in the number of ACKs included in the pattern but differ in the position of ACK (that is, the downlink unit band to which successfully received downlink data is assigned) in the pattern. Thus, even in the case in which all downlink data corresponding to the detected downlink assignment control information have been successfully received, when the number of successfully received downlink data (the number of ACKs) is different or when the downlink unit band to which successfully received downlink data has been assigned (the position of ACK) is different even though the number of successfully received downlink data (the number of ACKs) is the same, different SR resources and different phase points are used for the response signal.

For example, inFIG.11B, when downlink data has been successfully received in all of downlink unit bands (“A/A/A”), the phase point (−1, 0) of SR resource2is used. Further, when downlink data has been successfully received in downlink unit bands1and2but downlink data has not been received in downlink unit band3(“A/A/N” and “A/A/D”), the phase point (−1, 0) of SR resource1is used. Further, when downlink data has been successfully received in downlink unit bands1and3but downlink data has not been successfully received in downlink unit band2(“A/N/A” and “A/D/A”), the phase point (0, j) of SR resource2is used. Further, when downlink data has been successfully received in downlink unit band1but downlink data has not been received in downlink unit bands2and3(“A/N/N”, “A/N/D”, “A/D/N”, and “A/D/D”), the phase point (0, j) of SR resource1is used. Further, when downlink data has not been received in downlink unit band1but downlink data has been successfully received in downlink unit bands2and3(“N/A/A” and “D/A/A”), the phase point (0, −j) of SR resource2is used. Further, when downlink data has not been received in downlink unit bands1and3but downlink data has been successfully received in downlink unit band2(“N/A/N”, “N/A/D”, “D/A/N”, and “D/A/D”), the phase point (0, −j) of SR resource1is used. Further, when downlink data has not been received in downlink unit bands1and2but downlink data has been successfully received in downlink unit band3(“N/N/A”, “N/D/A”, “D/N/A”, and “D/D/A”), the phase point (1, 0) of SR resource2is used. Further, when downlink data has not been received in all of downlink unit bands (“N/N/N”, “NN/D”, “N/D/N”, “N/D/D”, “D/N/N”, “D/N/D”, and “D/DN”), the phase point (1, 0) of SR resource1is used.

Here, the SR resource illustrated inFIG.11Bis notified from base station100to terminal200in advance, similarly toFIG.9B. Thus, inFIG.11B(“when SR and response signal are transmitted” illustrated inFIG.10C), there is no limitation as inFIG.11A(“when only response signal is transmitted” illustrated inFIG.10B), and all of the seven states (“N/N/N”, “N/N/D”, “N/D/N”, “N/D/D”, “D/N/N”, and “D/N/D”) can be associated with the same resource and the same phase point (inFIG.11B, the phase point (1, 0) of SR resource1). Thus, inFIG.11B, a total of 8 phase points are necessary for notifying all states (a total of 26 states illustrated inFIG.11B(26 reception success/failure patterns)).

That is, inFIG.11A, due to the limitation, a total of 10 phase points are necessary for notifying all states (reception success/failure patterns), and three ACK/NACK resources are necessary for notifying the response signals of downlink unit bands1,2, and3. On the other hand, inFIG.11B, two SR resources (PUCCH resources) may be used to notify the SR and the response signals of downlink unit bands1,2, and3.

As described above, when terminal200simultaneously transmits the SR and the response signal, mapping illustrated inFIG.11Bis used. Thus, even when the channel selection is applied as a method of transmitting the response signal, the number of SR resources can be suppressed. InFIG.10A, two SR resources, which are less by one resource than three ACK/NACK resources, are preferably prepared. That is, inFIG.10A, five PUCCH resources (SR resources and ACK/NACK resources) are enough for transmitting the SR and the response signal.

InFIG.11B, it should be noted that the states (the reception success/failure pattern candidate group) of the response signals notified using adjacent phase points (that is, phase points having a phase difference of 90° (π/2 radians)) in the same resource are different from each other only in the reception status in one downlink unit band. For example, in SR resource2illustrated inFIG.11B, the state “A/A/A” notified using the phase point (−1, 0) and the states “A/N/A” and “A/D/A” notified using the phase point (0, j) (having a phase difference of 90° with respect to the phase point (−1, 0)) are different from each other only in the reception status of downlink unit band2(CC2). Similarly, in SR resource2illustrated inFIG.11B, the state “A/A/A” notified using the phase point (−1, 0) and the states “N/A/A” and “D/A/A” notified using the phase point (0, −j) (having a phase difference of 90° with respect to the phase point (−1, 0)) are different from each other only in the reception status of downlink unit band1(CC1). This is similarly applied to the other phase points.

As a result, similarly toFIG.9B, even when the phase point is erroneously decided, base station100side (deciding section118) can suppress the number of unit bands having a retransmission control error to a minimum, thereby minimizing degradation in retransmission efficiency.

Further, when terminal200transmits only the SR (“when only SR is transmitted” illustrated inFIG.10D), terminal200transmits the SR using the same resource (SR resource1) and the same phase point (1, 0) as in the state (reception success/failure pattern) in which all is NACK (or DTX), as illustrated inFIG.11B.

As described above, according to the present embodiment, control section208of terminal200performs transmission control of the SR and the response signal, based on the generation status of the SR and the pattern as to whether or not downlink data has been successfully received in the downlink unit band included in the unit band group set to its own terminal (error detection result). Further, when the SR and the response signal have been simultaneously generated in the same sub frame, control section208causes a pair of the PUCCH resource (SR resource) for notifying the response signal and the phase point of the response signal to be different according to the number of successfully received downlink data (that is, the number of ACKs) and the downlink unit band (that is, the position of ACK in the reception success/failure pattern) to which successfully received downlink data has been assigned in each reception success/failure (error detection result) pattern. That is, a pair of the PUCCH resource (SR resource) and the phase point of the response signal selected by terminal200differs according to the number of successfully received downlink data (that is, the number of ACKs) and the downlink unit band (that is, the position of ACK in the reception success/failure pattern) to which successfully received downlink data has been assigned in each reception success/failure pattern.

As a result, base station100which is a reception side of the response signal can specify a combination of downlink unit bands in which downlink data has been successfully received, based on the PUCCH resource through which the response signal has been received and the phase point of the response signal. Further, terminal200changes the PUCCH resource (the ACK/NACK resource or the SR resource) and the transmission rule (mapping rule) according to the generation status of the SR at terminal200side. At this time, when the SR and the response signal have been simultaneously generated in the same sub frame, terminal200notifies the response signal using all phase points (constellation points) of the SR resource. Thus, the number of SR resources necessary for notifying the SR and the response signal can be reduced. That is, the number of SR resources to be notified from base station100to terminal200can be reduced. As described above, according to the present embodiment, even when the channel selection is applied as a method of transmitting the response signal in the LTE-A, the amount of an increase in the overhead of the uplink control channel (PUCCH) can be suppressed, and the SR and the response signal can be simultaneously transmitted.

Embodiment 2

In Embodiment 2, the terminal cancels transmission of ACK information in some of downlink unit bands so as to further reduce the overhead of the uplink control channel (PUCCH) compared to Embodiment 1. That is, the terminal drops ACK information in some downlink unit bands. Thus, in Embodiment 2, the overhead of the uplink control channel (PUCCH) can be further reduced compared to Embodiment 1.

A concrete description will be made below. Basic configurations of the base station and the terminal according to Embodiment 2 are the same as in Embodiment 1, and thus a description will be made with reference toFIG.6(base station100) andFIG.7(terminal200).

[Operation of Terminal200: When There are Three Downlink Unit Bands]

The following description will be made in connection with an example in which three downlink unit bands (downlink unit bands1,2, and3) are set to terminal200. Here, similarly to Embodiment 1, an ACK/NACK resource (PUCCH resource) associated with a downlink control information assignment resource used for downlink assignment control information for downlink data transmitted in downlink unit band1is defined as ACK/NACK resource1. Further, an ACK/NACK resource (PUCCH resource) associated with a downlink control information assignment resource used for downlink assignment control information for downlink data transmitted in downlink unit band2is defined as ACK/NACK resource2. Further, an ACK/NACK resource (PUCCH resource) associated with a downlink control information assignment resource used for downlink assignment control information for downlink data transmitted in downlink unit band3is defined as ACK/NACK resource3.

Further, in the following description, base station100notifies terminal200of information related to one resource (an SR resource illustrated inFIG.12A) for transmitting an SR in an uplink unit band set to terminal200by a separate signaling technique (for example, higher layer signaling). That is, control section208of terminal200retains information related to the SR resource notified from base station100.

Further, terminal200specifies an ACK/NACK resource associated with a CCE, which is occupied by downlink assignment control information received by its own terminal, among a plurality of CCEs configuring PDCCHs of downlink unit bands1,2, and3as ACK/NACK resource1,2, or3.

Here, inFIG.12A, an SR resource and ACK/NACK resources1,2, and3are different code resources from each other such that at least one of a ZAC sequence (primary spreading) or a Walsh sequence/DFT sequence is different.

Next, a description will be made in connection with mapping examples 1 to 4 of the response signal in terminal200for suppressing the number of SR resources to one, even when three downlink unit bands (downlink unit bands1to3) are set to terminal200.

MAPPING EXAMPLE 1

FIGS.13A and13B

In mapping example 1, when the SR and the response signal are simultaneously transmitted (“when SR and response signal are transmitted” illustrated inFIG.12C), terminal200decides a resource, to which the response signal is to be mapped, and a phase point according to an error detection result pattern on downlink unit band1(CC1) and downlink unit band2(CC2), regardless of whether or not downlink unit band3(CC3) is in a state of any one of ACK, NACK, and DTX. That is, terminal200uses the mapping rule (FIG.9B) used when there are two downlink unit bands in Embodiment 1. Here, it is assumed that priorities, among downlink unit bands1to3, which base station100uses to transmit downlink data, are set to be higher in ascending order of downlink unit bands1,2, and3.

Specifically, when only the response signal is transmitted (“when only response signal is transmitted” illustrated inFIG.12B), it is similar to Embodiment 1 (FIG.11A) as illustrated inFIG.13A.

On the other hand, when the SR and the response signal have been simultaneously generated (“when SR and response signal are transmitted” illustrated inFIG.12C), reception success/failure (error detection result) pattern candidates of downlink unit band1(CC1) and downlink unit band2(CC2) are associated with a phase point of the response signal in the SR resource as illustrated inFIG.13B. That is, inFIG.13B, a resource for transmitting the response signal and a phase point are decided, regardless of the reception status of downlink unit band3(CC3) in terminal200. That is, the response signal for downlink unit band3is not actually notified from terminal200to base station100and dropped. That is, downlink data transmitted from base station100to terminal200using downlink unit band3is necessarily re-transmitted.

However, it is rare for terminal200side to simultaneously generate the SR and the response signal in the same sub frame. Further, even though base station100has set three downlink unit bands for terminal200, it is actually enough for base station100to transmit downlink data to terminal200using only one downlink unit band (for example, downlink unit band1having a highest priority) in most cases, and thus base station100needs not necessarily use downlink unit band3. That is, there are few cases in which base station100has to transmit downlink data to the terminal using downlink unit band3. When these are taken into consideration, a possibility that terminal200would not detect downlink assignment control information in downlink unit band3is high (that is, a possibility of DTX is high). Thus, as illustrated inFIG.13B, even though terminal200does not transmit (drops) information related to the response signal for downlink unit band3, retransmission efficiency is hardly affected.

Further, when terminal200transmits only the SR (“when only SR is transmitted” illustrated inFIG.12D), terminal200transmits the SR using the same phase point (1, 0) as in a state (reception success/failure pattern) in which all reception statuses for downlink unit bands1and2are NACK (or DTX) as illustrated inFIG.13B.

Thus, in mapping example 1, only when the SR and the response signal are simultaneously generated in the same sub frame, terminal200(control section208) does not transmit (drops) information related to the response signal for some downlink unit bands (information related to the response signal of downlink unit band3inFIG.13B). That is, only when the SR and the response signal are simultaneously generated in the same sub frame, terminal200bundles ACK for some downlink unit bands into NACK. Here, since terminal200drops the response signal for the downlink unit band having a low priority among a plurality of downlink unit bands set to terminal200, the dropping of some response signals does not much affect retransmission efficiency. Thus, in the above described way, the overhead of the uplink control channel (PUCCH) can be reduced without lowering retransmission efficiency.

MAPPING EXAMPLE 2

FIGS.14A and14B

In mapping example 2, when the SR and the response signal are simultaneously transmitted (“when SR and response signal are transmitted” illustrated inFIG.12C), terminal200bundles states in which the number of ACKs among reception success/failure (error detection result) pattern candidates (states) is small, and the terminal200maps a bundling result to the same phase point as the SR resource. That is, when the SR and the response signal are simultaneously transmitted, terminal200bundles reception success/failure (error detection result) pattern candidates (states) which are relatively low in probability of occurrence, and maps a bundling result to the same phase point as the SR resource.

Generally, base station100performs adaptive modulation so that an error rate (block error rate) of downlink data can range from about 10% to about 30%. For this reason, a probability that terminal200will generate ACK as an error detection result on certain downlink data is higher than a probability that terminal200will generate NACK. That is, a reception success/failure (error detection result) pattern (state) which is large in the number of ACKs is in a state in which a probability of occurrence is relatively high, and a reception success/failure (error detection result) pattern (state) which is small in the number of ACKs is in a state in which a probability of occurrence is relatively low.

In this regard, when the SR and the response signal have been simultaneously generated (“when SR and response signal are transmitted” illustrated inFIG.12C), terminal200transmits a state in which the number of ACKs is one (a state in which the number of ACKs is small) using the same phase point (the phase point (1, 0) of the SR resource inFIG.14B) as a state in which all is NACK (or DTX). That is, inFIG.14B, terminal200bundles a state in which the number of ACKs is one (a state in which the number of ACKs is small) into a state in which all is NACK (or DTX).

On the other hand, terminal200notifies states in which the number of ACKs is 2 or 3 (a state in which the number of ACKs is large) using different phase points in the SR resource as illustrated inFIG.14B. Here, in order to suppress the number of SR resources to one, some states (“N/A/A” and “D/A/A”) among states in which the number of ACKs is 2 are also bundled into a state in which all is NACK (or DTX) as illustrated inFIG.14B. Here, similarly to mapping example 1, priorities, among downlink unit bands1to3, which base station100uses to transmit downlink data, are set to be higher in ascending order of downlink unit bands1,2, and3. In this case, a state (“N (or D)/A/A”) in which the response signals for downlink unit bands2and3are ACK is lower in probability of occurrence than other states (“A/A/N(or D)” and “A/N(or D)/A”) in which the number of ACKs is 2. That is, inFIG.14B, in order to suppress the number of SR resources to one, some states (“N/A/A” and “D/A/A”), which are low in probability of occurrence, among states in which the number of ACKs is 2 are also bundled into a state in which all is NACK (or DTX).

Thus, a state in which the number of ACKs is 1 (and some of states in which the number of ACKs is 2) is not actually notified from terminal200to base station100. That is, downlink data, which has been transmitted from base station100to terminal200using a downlink unit band whose response signal is ACK in a state in which the number of ACKs is 1 (and some of states in which the number of ACKs is 2), is necessarily retransmitted.

However, it is rare for terminal200side to simultaneously generate the SR and the response signal in the same sub frame, similarly to mapping example 1. Further, as described above, a possibility that ACK will be generated for certain downlink data is higher than a possibility that NACK will be generated. When these are taken into consideration, even though a state in which the number of ACKs is 1 (and some of states in which the number of ACKs is 2), that is, a state in which a probability of occurrence is low, is bundled into a state in which all is NACK (or DTX), retransmission efficiency is hardly affected.

Further, in mapping example 2, when terminal200transmits only the response signal (“when only response signal is transmitted” illustrated inFIG.12B), it is similar to Embodiment 1 (FIG.11A) as illustrated inFIG.14A. Further, when terminal200transmits only the SR (“when only SR is transmitted” illustrated inFIG.12D), terminal200transmits the SR using the same phase point (1, 0) as in the state in which all is NACK (or DTX) (and some of states in which the number of ACKs is 2), as illustrated inFIG.14B.

In the above-described way, in mapping example 2, only when the SR and the response signal have been simultaneously generated in the same sub frame, terminal200(control section208) does not transmit ACK for some downlink unit bands. Specifically, terminal200(control section208) bundles a state in which the number of ACKs is small (the state in which the number of ACKs is 1 inFIG.14B) into a state in which all is NACK (or DTX). Here, since the state in which the number of ACKs is small is lower in probability of occurrence than the state in which the number of ACKs is large, even though the state in which the number of ACKs is small is bundled into the state in which all is NACK (DTX), retransmission efficiency is not much affected. Thus, in the above-described way, the overhead of the uplink control channel (PUCCH) can be reduced without lowering retransmission efficiency.

MAPPING EXAMPLE 3

FIGS.15A and15B

In mapping example 3, when the SR and the response signal are simultaneously transmitted (“when SR and response signal are transmitted” illustrated inFIG.12C), among the reception success/failure (error detection result) pattern candidates (states), terminal200bundles a state including ACK for downlink data transmitted using a downlink unit band which is not important to terminal200into a state in which all is NACK (or DTX), and maps a bundling result to the same phase point of the same resource. That is, when the SR and the response signal are simultaneously transmitted, terminal200does not bundle a state including ACK for downlink data transmitted using a downlink unit band which is important to terminal200into NACK, and performs transmission using different phase points.

Here, examples of the downlink unit band which is important to terminal200include (1) a downlink unit band onto which broadcast information (BCH) to be received by terminal200has been mapped, (2) a downlink unit band received when terminal200is initially connected to base station100, that is, before carrier aggregation communication starts, or (3) a downlink unit band which is explicitly notified from base station100to terminal200as an important carrier (anchor carrier). In the following description, it is assumed that downlink unit band1(CC1) is an important downlink unit band (for example, anchor carrier).

In this regard, when the SR and the response signal have been simultaneously generated (“when SR and response signal are transmitted” illustrated inFIG.12C), terminal200bundles some ACKs for downlink unit bands2and3(unimportant downlink unit bands) other than important downlink unit band1into NACK. On the other hand, terminal200notifies ACK and NACK for downlink data transmitted by using important downlink unit band1(anchor carrier, CC1), using different phase points, as illustrated inFIG.15B. That is, when the SR and the response signal have been simultaneously generated, terminal200decides a resource for transmitting the response signal and a phase point, based on only the reception status of downlink unit band1(CC1) independent of the reception statuses of downlink unit band2(CC2) and downlink unit band3(CC3) in terminal200as illustrated inFIG.15B.

Thus, base station100can reliably decide which of ACK and NACK has been generated for downlink data transmitted using important downlink unit band1(anchor carrier) in terminal200. Further, when only the response signal is transmitted (“when only response signal is transmitted” illustrated inFIG.12B) as illustrated inFIG.15A, base station100can decide the reception status by terminal200on all downlink unit bands, similarly to Embodiment 1 (FIG.11A).

Meanwhile, when the SR and the response signal have been simultaneously generated, even though ACK has been generated in downlink unit bands2and3, several situations in which base station100is difficult to decide ACK and NACK (states notified using the phase point (1, 0) illustrated inFIG.15B) occur.

However, similarly to mapping example 1, it is rare for terminal200side to simultaneously generate the SR and the response signal in the same sub frame. Further, base station100transmits important information (for example, control information of a higher layer) using important downlink unit band1(anchor carrier). Thus, even when terminal200has simultaneously generated the SR and the response signal, base station100can reliably decide ACK and NACK for downlink unit band1(anchor carrier), and terminal200can receive important information with the small number of transmission times (the small number of retransmission times). When these are taken into consideration, even though it is difficult to normally notify base station100of information related to the response signal for unimportant downlink unit bands2and3depending on circumstances, influence on the whole system is small.

In mapping example 3, when terminal200transmits only the SR (“when only SR is transmitted” illustrated inFIG.12D), terminal200transmits the SR using the same phase point (1, 0) as a state in which the reception status of downlink unit band1is NACK or DTX (that is, a state in which some ACKs of unimportant downlink unit bands2and3are bundled into NACK) as illustrated inFIG.15B.

Thus, in mapping example 3, only when the SR and the response signal have been simultaneously generated in the same sub frame, terminal200(control section208) does not transmit information related to some response signals for downlink unit bands (unimportant downlink unit bands) other than an important downlink unit band (anchor carrier). Specifically, terminal200bundles some ACKs for downlink unit bands (unimportant downlink unit bands) other than an important downlink unit band (anchor carrier) into NACK. Thus, when the SR and the response signal have been simultaneously generated in the same sub frame, terminal200preferentially notifies the response signal for the important downlink unit band (anchor carrier) among a plurality of downlink unit bands set to terminal200. In the above described way, the overhead of the uplink control channel (PUCCH) can be reduced without adversely influencing the whole system.

MAPPING EXAMPLE 4

FIGS.16A and16B

In mapping example 4, when the SR and the response signal are simultaneously transmitted (“when SR and response signal are transmitted” illustrated inFIG.12C), terminal200decides a resource onto which the response signal is mapped and a phase point even from among the ACK/NACK resource as well as the SR resource.

Specifically, inFIGS.16A and16B, when the SR and the response signal have been simultaneously generated (“when SR and response signal are transmitted” illustrated inFIG.12C), a state in which the number of ACKs is large (here, a state in which the number of ACKs is 2 or more) is associated with a resource and a phase point which are different from other states, similarly to mapping example 2 (FIG.14B). That is, respective states (reception success/failure (error detection result) patterns) are associated with resources and phase points of the response signal, so as to prevent a state in which the number of ACKs is large from being bundled into other states.

Further, inFIGS.16A and16B, when the SR and the response signal have been simultaneously generated (“when SR and response signal are transmitted” illustrated inFIG.12C), ACK and NACK for an important downlink unit band (here, downlink unit band1(for example, anchor carrier)) are associated with different resources and different phase points, similarly to mapping example 3 (FIG.15B). That is, respective states (reception success/failure (error detection result) patterns) are associated with resources and phase points of the response signal so as to prevent ACK for an important downlink unit band (here, downlink unit band1(for example, anchor carrier)) from being bundled into NACK.

At this time, the respective states (reception success/failure (error detection result) patterns) are grouped into 6 types of states (6 reception success/failure (error detection result) pattern candidate groups). Specifically, the respective states are grouped into 6 types of pattern candidate groups including “A/A/A”, “A/A/N(D)”, “A/N(D)/A”, “A/N(D)/N(D)”, “N(D)/A/A”, and the other states, which are indicated by white circles “∘” illustrated inFIGS.16A and16B.

In this regard, when the SR and the response signal have been simultaneously generated (“when SR and response signal are transmitted” illustrated inFIG.12C), terminal200transmits the response signal using phase points (0, −j) of ACK/NACK resources1and2which are not used when only the response signal is transmitted (“when only response signal is transmitted” illustrated inFIG.12B) among ACK/NACK resources1and2illustrated inFIG.16Ain addition to 4 phase points of the SR resource illustrated inFIG.16B. That is, terminal200transmits information related to the response signal using a total of 6 phase points including 4 phase points of the SR resource illustrated inFIG.16B, and 2 phase points (0, −j) of ACK/NACK resources1and2illustrated inFIG.16A. In the above-described way, when the SR and the response signal have been simultaneously generated (“when SR and response signal are transmitted” illustrated inFIG.12C), even though there are 6 error detection result candidate pattern groups, since the phase point which is not used by the ACK/NACK resource is used, the number of SR resources necessary for transmitting the SR and the response signal can be suppressed to one.

That is, when the SR and the response signal have been simultaneously generated (“when SR and response signal are transmitted” illustrated inFIG.12C), terminal200bundles only a state which is a state including ACK for unimportant downlink unit bands2and3and which is small in the number of ACKs (a state in which the number of ACKs is 1) into a state in which all is NACK (or DTX).

Thus, when the SR and the response signal have been simultaneously generated (“when SR and response signal are transmitted” illustrated inFIG.12C), base station100can reliably decide a state in which the number of ACKs is large (here, a state in which the number of ACKs is 2 or more) similarly to mapping example 2, and can reliably decide the response signal for the important downlink unit band (for example, anchor carrier) similarly to mapping example 3.

Further, in mapping example 4, when terminal200transmits only the response signal (“when only response signal is transmitted” illustrated inFIG.12B), it is similar to Embodiment 1 (FIG.11A), as illustrated inFIG.16A(black circles “●”). Further, when terminal200transmits only the SR (“when only SR is transmitted” illustrated inFIG.12D), terminal200transmits the SR using the same phase point (1, 0) as in the state in which all is NACK (or DTX) (and the state including ACK dropped only when the SR is generated), as illustrated inFIG.16B.

In the above-described way, in mapping example 4, when the SR and the response signal have been simultaneously generated in the same sub frame, terminal200associates information related to the response signal for some downlink unit bands with the phase point which is not used by the ACK/NACK resource. As a result, the number of error detection result pattern candidates which can be decided by the base station can be increased, without increasing the number of SR resources. That is, the number of ACKs dropped by terminal200(the number of ACKs bundled into NACK) can be reduced. That is, influence on retransmission efficiency caused by the dropping of the response signal at terminal200side can be further reduced compared to mapping examples 2 and 3. In the above-described way, the overhead of the uplink control channel (PUCCH) can be reduced without lowering retransmission efficiency.

The mapping examples of the response signal in terminal200have been described above.

In the above-described way, according to the present embodiment, by dropping ACK information in some downlink unit bands at terminal200, the overhead of the uplink control channel (PUCCH) can be further reduced compared to Embodiment 1.

The embodiments of the present invention have been described above.

The above embodiments have been described in connection with an example in which all ACK/NACK resources are notified in association with CCEs occupied by the downlink assignment control information for the terminal (that is, implicitly), however, the present invention is not limited thereto. For example, the mapping rule of the response signal inFIG.11Amay be applied to the case in which some ACK/NACK resources are explicitly notified from the base station, as illustrated inFIGS.17A and17B.FIG.17Bis identical toFIG.11B. However, inFIG.17A, since ACK/NACK resource2is explicitly notified, the terminal side already knows information of ACK/NACK resource2regardless of whether or not the terminal has successfully received the downlink assignment control information. Thus, the terminal can map the state such as “N/D/A” or “D/D/A” (that is, the state in which DTX has been generated for downlink unit band2) to ACK/NACK resource2. That is, even when three downlink unit bands are set to the terminal, the number of ACK/NACK resources necessary for transmitting only the response signal at the terminal can be reduced to two, compared toFIG.11A(three ACK/NACK resources).

The above embodiments have been described in connection with the example in which the ZAC sequence is used for primary spreading in the PUCCH resource, and the Walsh sequence and the DFT sequence are used for secondary spreading as OC indices. However, in the present invention, non-ZAC sequences which are mutually separable by different cyclic shift indices may be used for primary-spreading. For example, a generalized chirp like (GCL) sequence, a constant amplitude zero auto correlation (CAZAC) sequence, a Zadoff-Chu (ZC) sequence, a pseudo-noise (PN) sequence such as an M sequence or an orthogonal gold code sequence, a sequence which is randomly generated by a computer and has a steep auto-correlation characteristic on the time axis, or the like may be used for primary-spreading. The ZAC sequence may be expressed as “base sequence” in English, which means a base sequence for giving a cyclic shift. Further, sequences orthogonal to each other or any sequences which are recognized as being substantially orthogonal to each other may be used as OC indices for secondary-spreading. In the above description, a resource of a response signal (for example, a PUCCH resource) is defined by a cyclic shift index of a ZAC sequence and a sequence number of an OC index.

Further, the above embodiments have been described in connection with the example in which secondary spreading is performed after primary spreading, as an order of processing at the terminal side. However, an order of processing of primary spreading and secondary spreading is not limited thereto. That is, since both primary spreading and secondary spreading are the processing represented by multiplication, for example, even when primary spreading is performed on the response signal after secondary spreading, the same effect as in the present embodiment is obtained.

Further, the above embodiments have been described in connection with the example in which control section101of base station100performs control such that downlink data and downlink assignment control information for the downlink data are mapped to the same downlink unit band, however, the present embodiment is not limited thereto. That is, even when downlink data and downlink assignment control information for the downlink data are mapped to separate downlink unit bands, the present embodiment can be applied as long as a correspondence relation between the downlink assignment control information and the downlink data is clear. In this case, the terminal side obtains ACK/NACK resource1as a PUCCH resource corresponding to “a resource (CCE) occupied by downlink assignment control information for downlink data transmitted through downlink unit band1.”

Further, the above embodiments have been described in connection with the example in which the response signal transmitted by the terminal is modulated using a quadrature phase shift keying (QPSK) scheme. However, the present invention is not limited to the case in which the response signal is modulated using the QPSK scheme and can be applied, for example, even when the response signal is modulated using the BPSK scheme or a 16 quadrature amplitude modulation (QAM).

Further, the above embodiments have been described in connection with the example in which the present invention is implemented in hardware, however, the present invention may be implemented in software.

The functional blocks used for description of the above embodiments are typically implemented as large scale integration (LSI) which is an integrated circuit (IC). The functional blocks may be individually implemented as one chip, or some or all of the functional blocks may be implemented as one chip. Here, “LSI” is adopted here but this may also be referred to as “IC,” “system LSI,” “super LSI” or “ultra LSI” depending on a difference in integration.

A circuit integration technique is not limited to the LSI, and implementation by a dedicated circuit or a universal processor may be adopted. After LSI manufacture, a field programmable gate array (FPGA) which is programmable or a reconfigurable processor in which connections and settings of circuit cells within an LSI can be reconfigured may be used.

Further, if a circuit integration technique of replacing the LSI by another technique advanced or derived from a semiconductor technology appears, the functional blocks may be integrated using the technique. There may be a possibility that a biotechnology will be applied.

The disclosure of Japanese Patent Application No. 2009-230727, filed on Oct. 2, 2009, including the specification, drawings and abstract, is incorporated herein by reference in its entirety.

INDUSTRIAL APPLICABILITY

A terminal apparatus and a retransmission method according to the present invention are useful in simultaneously transmitting an SR and a response signal while suppressing an increase in the overhead of an uplink control channel, when channel selection is applied as a method of transmitting a response signal when carrier aggregation communication is performed using a plurality of downlink unit bands.

REFERENCE SIGNS LIST

100Base station101Control section102Control information generating section103,105Coding section104,107,213Modulating section106Data transmission control section108Mapping section109,216IFFT section110,217CP adding section111,218Radio transmitting section112,201Radio receiving section113,202CP removing section114PUCCH extracting section115Despreading section116Sequence control section117Correlation processing section118Deciding section119Retransmission control signal generating section200Terminal203FFT section204Extracting section205,209Demodulating section206,210Decoding section207Deciding section208Control section211CRC section212Response signal generating section214Primary spreading section215Secondary spreading section