Method and apparatus for performing HARQ in a wireless communication system
The present invention provides a method and apparatus for performing hybrid automatic repeat request (HARQ) in a wireless communication system. A terminal transmits a plurality of code words on a physical uplink shared channel (PUSCH) and receives a plurality of acknowledgement/non-acknowledgement (ACK/NACK) signals, which indicates if each of the plurality of code words has been received, on each physical hybrid-ARQ indicator channel (PHICH) corresponding to the respective code words. A downlink resource for which each of the PHICHs is mapped is determined based on the smallest physical resource block (PRB) index (I PRB — RA lowest — index ) among PRBs mapped by the PUSCH and on an uplink demodulation reference signal (DMRS) circular shift parameter (n DMRS ), and those downlink resources for which PHICHs are mapped respectively do not overlap each other.
1. A method of determining a physical hybrid-ARQ indicator channel (PHICH) resource in a wireless communication system, the method comprising:
transmitting a first codeword and a second codeword through a physical uplink shared channel (PUSCH); and
determining a first PHICH resource and a second PHICH resource respectively corresponding to the first codeword and the second codeword,
wherein the first PHICH resource is determined based on a lowest physical resource block (PRB) index I PRB — RA lowest — index among PRBs in a first slot to which the PUSCH is mapped, and
wherein the second PHICH resource is determined based on the lowest PRB index I PRB — RA lowest — index and an offset β according to the equation below:
n PHICH group =(( I PRB —RA lowest — index +β)+ n DMRS )mod N PHICH group +I PHICH N PHICH group ,
where n PHICH group is an index of a PHICH group, n DMRS is a cyclic shift field for a demodulation reference signal (DMRS), I PRB — RA lowest — index is the lowest PRB index among PRBs in a first slot to which the PUSCH is mapped, β is the offset, N PHICH group is the number of PHICH groups, and I PHICH is a value 0 or 1.
2. The method of claim 1 , wherein the offset β is 1 with respect to the second PHICH resource.
3. The method of claim 1 , wherein the offset β is predetermined or is signaled by a higher layer.
4. The method of claim 1 ,
wherein the first PHICH resource corresponds to a first transport block (TB) of the PUSCH, and
wherein the second PHICH resource corresponds to a second TB of the PUSCH.
5. The method of claim 4 ,
wherein the first TB corresponds to any one of the first codeword and the second codeword, and
wherein the second TB corresponds to the remaining one codeword between the first codeword and the second codeword.
6. The method of claim 1 , further comprising:
receiving a first acknowledgement/non-acknowledgement (ACK/NACK) signal corresponding to the first codeword through the first PHICH resource; and
receiving a second ACK/NACK signal corresponding to the second codeword through the second PHICH resource.
7. The method of claim 6 , wherein the first codeword and the second codeword and the first ACK/NACK signal and the second ACK/NACK signal are transmitted through a plurality of carriers.
8. The method of claim 7 ,
wherein a carrier for transmitting the first codeword is equal to a carrier for transmitting the first ACK/NACK signal, and
wherein a carrier for transmitting the second codeword is equal to a carrier for transmitting the second ACK/NACK signal.
9. The method of claim 7 , wherein the plurality of carriers are managed by at least one media access control (MAC).
10. The method of claim 6 , wherein the first ACK/NACK signal and the second ACK/NACK signal are transmitted through a plurality of antennas.
11. The method of claim 1 , wherein the second PHICH resource is further determined according to the equation below:
n PHICH seq =(└( I PRB — RA lowest — index +β)/ N PHICH group ┘+n DMRS )mod 2 N SF PHICH ,
where n PHICH seq is an orthogonal sequence index in the PHICH group, n DMRS is the cyclic shift field for the DMRS, N SF PHICH is a size of a spreading factor (SF), I PRB — RA lowest — index is the lowest PRB index among PRBs in a first slot to which the PUSCH is mapped, and β is the offset.
12. A wireless communication system comprising:
a radio frequency (RF) unit for transmitting or receiving a radio signal; and
a processor coupled to the RF unit,
wherein the processor is configured for:
transmitting a first codeword and a second codeword through a physical uplink shared channel (PUSCH); and
determining a first physical hybrid-ARQ indicator channel (PHICH) resource and a second PHICH resource respectively corresponding to the first codeword and the second codeword,
wherein the first PHICH resource is determined based on a lowest physical resource block (PRB) index I PRB — RA lowest — index among PRBs in a first slot to which the PUSCH is mapped, and
wherein the second PHICH resource is determined based on the lowest PRB index I PRB — RA lowest — index , and an offset according to the equation below:
n PHICH group =(( I PRB —RA lowest — index +β)+ n DMRS )mod N PHICH group +I PHICH N PHICH group ,
where n PHICH group is an index of a PHICH group, n DMRS is a cyclic shift field for a demodulation reference signal (DMRS), I PRB — RA lowest — index is the lowest PRB index among PRBs in a first slot to which the PUSCH is mapped, β is the offset, N PHICH group is the number of PHICH groups, and I PHICH is a value 0 or 1.
13. The system of claim 12 , wherein the offset β is 1 with respect to the second PHICH resource.
14. The system of claim 12 , wherein the second PHICH resource is further determined according to the equation below:
n PHICH seq =(└( I PRB — RA lowest — index +β)/ N PHICH group ┘+n DMRS )mod 2 N SF PHICH ,
where n PHICH seq is an orthogonal sequence index in the PHICH group, n DMRS is the cyclic shift field for the DMRS, N SF PHICH is a size of a spreading factor (SF), I PRB — RA lowest — index is the lowest PRB index among PRBs in a first slot to which the PUSCH is mapped, and β is the offset.
15. A method of transmitting a physical hybrid-ARQ indicator channel (PHICH) sequence in a wireless communication system, the method comprising:
generating a first PHICH sequence and a second PHICH sequence respectively corresponding to a first codeword and a second codeword which are transmitted through a physical uplink shared channel (PUSCH); and
transmitting the first PHICH sequence and the second PHICH sequence to a user equipment respectively through a first PHICH resource and a second PHICH resource,
wherein the first PHICH resource is determined based on a lowest physical resource block (PRB) index I PRB — RA lowest — index among PRBs in a first slot to which the PUSCH is mapped, and
wherein the second PHICH resource is determined based on the lowest PRB index I PRB — RA lowest — index , and an offset β according to the equation below:
n PHICH group =(( I PRB —RA lowest — index +β)+ n DMRS )mod N PHICH group +I PHICH N PHICH group ,
where n PHICH group is an index of a PHICH group, n DMRS is a cyclic shift field for a demodulation reference signal (DMRS), I PRB — RA lowest — index is the lowest PRB index among PRBs in a first slot to which the PUSCH is mapped, β is the offset, N PHICH group is the number of PHICH groups, and I PHICH is a value 0 or 1.