Radio communication system, radio communication apparatus, and retransmission control method
View Patent ↗In a multiuser MIMO system, entire system throughput achieved during retransmission is significantly enhanced. When an interference signal addressed to another user equipment (UE 2 ) 200 b has been demodulated successfully, a user equipment (UE 1 ) 200 a holds the demodulated data pertaining to the interference signal, and feeds back ACK information about the UE 2 and CQI information achieved after elimination of the interference signal to a radio base station (BS) 100 . When the UE 2 performs retransmission after ended in a receiving failure and when the UE 1 has demodulated the interference signal addressed to the UE 2 successfully, the BS changes the distribution of communication resources in such a way that communication resources for the UE 2 become larger than those for the UE 1 . At the time of retransmission, the UE 1 eliminates the interference signal from a newly-received signal by use of previously-held demodulated data pertaining to the interference signal, and the UE 2 combines data pertaining to the desired signal held during previous receiving failure with data pertaining to the retransmitted signal by means of soft combining.
1. A radio transmission apparatus, comprising:
a resource allocator wherein, in a case where data is previously transmitted by the radio transmission apparatus to a second radio reception apparatus, and then subsequently retransmission of the data is performed by the radio transmission apparatus to the second radio reception apparatus based on a receiving failure by the second radio reception apparatus of the previously transmitted data, the resource allocator allocates communication resources in accordance with whether or not a first radio reception apparatus has successfully demodulated a signal, comprising the previously transmitted data, transmitted by the radio transmission apparatus and addressed to the second radio reception apparatus; and
a transmitter which performs the retransmission to the second radio reception apparatus by use of the allocated communication resources, the retransmission providing a desired signal to the second radio reception apparatus.
2. The radio transmission apparatus according to claim 1 ,
wherein the resource allocator that, when the first radio reception apparatus has successfully demodulated the signal addressed to the second radio reception apparatus, allocates the communication resources in such a way that the communication resource for the second radio reception apparatus becomes larger than the communication resource for the first radio reception apparatus.
3. The radio transmission apparatus according to claim 2 ,
wherein the resource allocator reduces the communication resource to the first radio reception apparatus when the first radio reception apparatus has successfully demodulated the signal addressed to the second radio reception apparatus.
4. The radio transmission apparatus according to claim 1 ,
wherein the radio transmission apparatus receives, from the first radio reception apparatus, quality information concerning signal quality achieved after elimination of a previous interference signal addressed to the second radio reception apparatus, and
wherein the resource allocator reduces in number a quantity of subcarriers allocated to the first radio reception apparatus based on said quality information, such that a communication resource for the second radio reception apparatus becomes larger than a communication resource for the first radio reception apparatus.
5. The radio transmission apparatus according to claim 1 ,
wherein when a plurality of radio reception apparatuses which have failed to demodulate desired signals have successfully demodulated an interference signal addressed to other radio reception apparatus, the resource allocator compares receiving qualities for the radio reception apparatuses and allocates the communication resource to the second radio reception apparatus exhibiting poor receiving quality in preference to the first radio reception apparatus exhibiting superior receiving quality.
6. The radio transmission apparatus according to claim 3 , comprising:
a retransmission information notification section that, when information showing unsuccessful receipt of a desired signal to the own station is received from the second radio reception apparatus, notifies respective radio reception apparatuses of retransmission information about performance of retransmission.
7. The radio transmission apparatus according to claim 1 ,
wherein, the resource allocator changes allocation of subcarriers.
8. The radio transmission apparatus according to claim 1 ,
wherein, the resource allocator changes allocation of transmission power.
9. The radio transmission apparatus according to claim 1 ,
wherein the resource allocator allocates the communication resources in accordance with a receiving quality information of the signal addressed to the second radio reception apparatus in the first radio reception apparatus.
10. A radio reception apparatus, comprising:
a demodulator that demodulates a signal transmitted from a radio transmission apparatus and addressed to another station;
an error determiner that determines whether the signal addressed to the other station has been demodulated successfully, and generates information indicating a determination result;
a quality calculator that calculates quality information concerning receiving signal quality that is achieved after the radio reception apparatus eliminates the signal addressed to the other station as an interference signal; and
a notification section that notifies the radio transmission apparatus of both of the information indicating the determination result and the quality information.
11. The radio reception apparatus according to claim 10 , comprising:
an other-addressed signal buffer section that holds demodulated data pertaining to the signal addressed to the other station when the signal addressed to the other station has been demodulated successfully; and
an interference eliminator that performs an interference elimination by use of the held and demodulated data when a next signal transmitted from the radio transmission apparatus is received.
12. The radio reception apparatus according to claim 11 , comprising:
a retransmission information receiver that receives retransmission information transmitted by the radio transmission apparatus to the other station,
wherein the interference eliminator performs an interference elimination by use of demodulated data held in the other-addressed signal buffer section when transmission to the other station is retransmission.
13. The radio reception apparatus according to claim 11 , comprising:
an own-addressed signal buffer section that, when an error is in a result of receipt of a signal addressed to the own station and transmitted from the radio transmission apparatus, holds data pertaining to the signal addressed to the own station; and
a combiner that receives a signal retransmitted from the radio transmission apparatus, and combines the held data pertaining to the signal addressed to the own station with data pertaining to the retransmitted signal.
14. The radio reception apparatus according to claim 11 , comprising:
an other-addressed signal information response section that, when the signal addressed to the other station has been demodulated successfully, feeds back to the radio transmission apparatus information showing successful receipt of the signal addressed to the other station.
15. The radio reception apparatus according to claim 14 , comprising:
a receiving status determiner that determines a receiving status of the signal addressed to the own station,
wherein the other-addressed signal buffer section and the other-addressed signal information response section performs operations, respectively, only when the receiving status is a predetermined threshold value or more.
16. The radio reception apparatus according to claim 14 , comprising:
a retransmission information receiver that receives retransmission information transmitted from the radio transmission apparatus to another radio reception apparatus,
wherein the other-addressed signal buffer section and the other-addressed signal information response section performs operations, respectively, only when received information whose retransmission is required by the other radio reception apparatus.
17. A radio communication base station equipped with the radio transmission apparatus according to claim 1 .
18. A radio communication mobile station equipped with the radio transmission apparatus according to claim 1 .
19. A retransmission control method, comprising:
allocating, in a case where data is previously transmitted by a radio transmission apparatus to a second radio reception apparatus, and then subsequently retransmission of the data is performed by the radio transmission apparatus to the second radio reception apparatus based on a receiving failure by the second radio reception apparatus of the previously transmitted data, communication resources in accordance with whether or not a first radio reception apparatus has successfully demodulated a signal, comprising the previously transmitted data, transmitted by the radio transmission apparatus and addressed to the second radio reception apparatus; and
performing retransmission to the second radio reception apparatus by use of the allocated communication resources, the retransmission providing a desired signal to the second radio reception apparatus.
20. The retransmission control method of claim 19 , wherein the step of allocating includes reducing in number a quantity of subcarriers allocated to the first radio reception apparatus based on quality information concerning signal quality achieved at the first radio reception apparatus upon its elimination of the signal addressed to the second radio reception apparatus as an interference signal, such that a communication resource for the second radio reception apparatus becomes larger than a communication resource for the first radio reception apparatus.