Terminal apparatus and method for transmitting a response signal at a terminal

Abstract

A terminal includes a decoder to decode a downlink control channel transmitted on one or more control channel element(s) (CCE(s)) in a search space including a plurality of CCEs. Processing circuitry in the terminal determines an uplink channel resource index based on the one or more CCEs, the uplink channel resource index having an association with a first uplink channel transmission spreading sequence and a second different uplink channel transmission spreading sequence. A transmitter transmits a response signal on an uplink channel using the first and second uplink channel transmission spreading sequences.

1 . (canceled) 
     
     
         2 . A terminal apparatus comprising:
 a deciding section, embodied on a processor, configured to decide a resource index of an uplink control channel to which a response signal to downlink data is mapped; and   a control section, embodied on a processor, configured to determine a plurality of sequences useable for the response signal, from the resource index of the uplink control channel,   wherein:   a downlink control channel is allocated to one or multiple control channel element(s) (CCE(s)) in a search space, where the search space includes CCEs corresponding to downlink control channel candidates;   the deciding section is configured to decide the resource index of the uplink control channel based on the CCE(s) to which the downlink control channel is allocated;   the search space for an aggregation size corresponding to a number of the CCE(s) to which the downlink control channel is allocated, is comprised of CCEs that are defined by starting on a CCE with a CCE number that depends on a total number of CCEs in a subframe and the aggregation size; and   at least part of the search space for the aggregation size is comprised of CCEs with consecutive CCE numbers.   
     
     
         3 . The terminal apparatus according to  claim 2 , wherein the plurality of sequences includes first spreading codes sequences and second spreading code sequences. 
     
     
         4 . The terminal apparatus according to  claim 3 , further comprising:
 a spreading section, embodied on a processor, configured to spread the response signal using one of the first spreading code sequences and one of the second spreading code sequences.   
     
     
         5 . The terminal apparatus according to  claim 4 , wherein the spreading section is configured to spread the response signal with the one of the first spreading code sequences to generate a first spread signal and then to spread the first spread signal with the one of the second spreading code sequences to generate a second spread signal for transmission. 
     
     
         6 . The terminal apparatus according to  claim 4 , wherein the first spreading codes sequences are one of the following: zero auto correlation sequences, Generalized Chirp Like (GCL) sequences, Constant Amplitude Zero Auto Correlation (CAZAC) sequences, Zadoff-Chu (ZC) sequences, or pseudo-noise (PN) sequences, and
 wherein the second spreading codes sequences are block-wise spreading sequences including Walsh or Fourier sequences.   
     
     
         7 . The terminal apparatus according to  claim 2 , further comprising:
 a receiver configured to receive the downlink control channel transmitted on the one or multiple CCE(s) from a base station, and   a decoding section, embodied on a processor, configured to decode the received downlink control channel in the search space.   
     
     
         8 . The terminal apparatus according to  claim 2 , further comprising:
 a transmitter configured to transmit the response signal on an uplink control channel,   wherein the resource index of the response signal is based on a CCE number of CCE(s) to which the downlink control channel is allocated.   
     
     
         9 . The terminal apparatus according to  claim 8 , wherein the resource index of the response signal is based on a CCE number of the first CCE of the one or multiple consecutive CCE(s) to which the downlink control channel is allocated. 
     
     
         10 . The terminal apparatus according to  claim 2 , wherein the starting CCE number is specific to both the total number of CCEs in the subframe and the aggregation size. 
     
     
         11 . The terminal apparatus according to  claim 2 , wherein the CCE number is different between at least two aggregation sizes. 
     
     
         12 . The terminal apparatus according to  claim 2 , wherein a first search space with a first aggregation size includes a CCE different from a CCE included in a second search space with a second aggregation size. 
     
     
         13 . The terminal apparatus according to  claim 2 , wherein a first search space with a first aggregation size does not overlap at least part of a second search space with a second aggregation size. 
     
     
         14 . The terminal apparatus according to  claim 2 , further comprising:
 a receiver configured to receive a control format indicator (CFI) indicating a number of symbols used for control channels in the subframe,   wherein the total number of CCEs in the subframe is based on the CFI.   
     
     
         15 . The terminal apparatus according to  claim 2 , wherein the total number of CCEs in the subframe depends on a system bandwidth, a number of symbols used for control channels, and a number of ACK/NACK channels for uplink data. 
     
     
         16 . The terminal apparatus according to  claim 2 , wherein the total number of CCEs in the subframe is larger than a maximum number of the aggregation size. 
     
     
         17 . A method comprising:
 deciding, at a user equipment, a resource index of a uplink control channel to which a response signal to downlink data is mapped; and   determining, at a user equipment, a plurality of sequences useable for the response signal, from the resource index of the uplink control channel,   wherein:   a downlink control channel is allocated to one or multiple control channel element(s) (CCE(s)) in a search space, where the search space includes CCEs corresponding to downlink control channel candidates;   the resource index of the uplink control channel is decided based on the CCE(s) to which the downlink control channel is allocated;   the search space for an aggregation size corresponding to a number of the CCE(s) to which the downlink control channel is allocated, is comprised of CCEs that are defined by starting on a CCE with a CCE number that depends on a total number of CCEs in a subframe and the aggregation size; and   at least part of the search space for the aggregation size is comprised of CCEs with consecutive CCE numbers.   
     
     
         18 . The method according to  claim 17 , wherein the plurality of sequences includes first spreading codes sequences and second spreading code sequences. 
     
     
         19 . The method according to  claim 18 , further comprising spreading the response signal using one of the first spreading code sequences and one of the second spreading code sequences. 
     
     
         20 . The method according to  claim 19 , further comprising:
 spreading the response signal with the one of the first spreading code sequences to generate a first spread signal, and   spreading the first spread signal with the one of the second spreading code sequences to generate a second spread signal for transmission,   wherein the first spreading codes sequences are one of the following: zero auto correlation sequences, Generalized Chirp Like (GCL) sequences, Constant Amplitude Zero Auto Correlation (CAZAC) sequences, Zadoff-Chu (ZC) sequences, Of pseudo-noise (PN) sequences, and   wherein the second spreading codes sequences are block-wise spreading sequences including Walsh or Fourier sequences.   
     
     
         21 . A non-transitory, computer-readable storage storing program code, which when executed by one or more processors, causes the one or more processors to:
 decide a resource index of a uplink control channel to which a response signal to downlink data is mapped; and   determine a plurality of sequences useable for the response signal, from the resource index of the uplink control channel,   wherein:   a downlink control channel is allocated to one or multiple control channel element(s) (CCE(s)) in a search space, where the search space includes CCEs corresponding to downlink control channel candidates;   the resource index of the uplink control channel is decided based on the CCE(s) to which the downlink control channel is allocated;   the search space for an aggregation size corresponding to a number of the CCE(s) to which the downlink control channel is allocated, is comprised of CCEs that are defined by starting on a CCE with a CCE number that depends on a total number of CCEs in a subframe and the aggregation size; and   at least part of the search space for the aggregation size is comprised of CCEs with consecutive CCE numbers.