Radio communication apparatus and resending controlling method
View Patent ↗A synthesized gain in a resending operation can be improved significantly by relatively simple control when resending control is applied upon executing of a transmission diversity using CDD. A radio communication apparatus equipped with a plurality of antennas and for performing communication by MIMO, includes a phase shift amount assigning section 18 for executing a CDD process to assign a cyclic phase shift to a transmission signal on a frequency axis, a response signal demodulator 16 for demodulating ACK/NACK received from a destination station, and outputting control information about a resending operation when NACK is received and a reception is failed, and an initial phase controller 17 for setting an offset to a phase shift at a time of CDD process in response to a number of transmission times in resending control such that a predetermined offset, which is produced by adding a phase difference from a signal transmitted from other antenna to the phase shift, is assigned to a signal transmitted from the antenna over a full frequency band, wherein a frequency characteristic of a radio propagation path at a time of resending is changed every time of transmission times.
1. A radio communication apparatus for performing communication by MIMO (Multi Input Multi Output) using a plurality of antennas, the radio communication apparatus comprising:
a cyclic delay diversity processor which is adapted to give a phase for each of a plurality of subcarriers to a signal transmitted from at least one antenna and sets a phase for each of the plurality of subcarriers, such that the phase for each of the plurality of subcarriers is changed cyclically on a frequency domain;
a resending controller which is adapted to execute a retransmission of the signal; and
an offset controller which sets a certain offset that is included in the phase of each of the plurality of subcarriers on retransmission of the signal, wherein the offset is set according to a number of retransmissions of the signal.
2. The radio communication apparatus according to claim 1 , wherein the offset controller is adapted to set the offset to a value, from a plurality of values, and a difference between the value and a value set in a preceding transmission is substantially equal to a greatest difference between the plurality of values.
3. The radio communication apparatus according to claim 2 , wherein the greatest difference between the value and the value set in the preceding transmission is π.
4. The radio communication apparatus according to claim 1 , further comprising:
an antenna mapping controller which is adapted to set a correspondence between the plurality of antennas and the signals according to the number of retransmissions.
5. The radio communication apparatus according to claim 4 , wherein the antenna mapping controller switches the antenna for the signal every number of retransmissions.
6. The radio communication apparatus according to claim 1 , further comprising:
a phase shift amount controller which is adapted to set a difference between phases for adjacent subcarriers according to the number of retransmissions.
7. The radio communication apparatus of claim 1 , wherein the offset of a second retransmission of the signal performed by the radio communication apparatus is different from another offset of a previous retransmission of the signal performed by the radio communication apparatus.
8. A radio communication apparatus for performing communication by MIMO (Multi Input Multi Output) using a plurality of antennas, the radio communication apparatus comprising:
a demodulator which is adapted to demodulate a received signal which was transmitted from at least one antenna and underwent a cyclic delay diversity process during transmission which sets a phase for each of a plurality of subcarriers, such that the phase for each of the plurality of subcarriers is changed cyclically on a frequency domain, wherein the phase of each of the plurality of subcarriers includes a certain offset for all of the subcarriers on retransmission of the signal and the offset is set according to a number of retransmissions of the signal;
wherein the demodulator is adapted to demodulate the received signal based on offset information, wherein the offset is set according to the number of retransmissions of the signal.
9. The radio communication apparatus according to claim 8 , wherein the demodulator demodulates the signal based on a correspondence between the plurality of antenna and the signal set according to the number of retransmissions.
10. The radio communication apparatus according to claim 8 , wherein the demodulator demodulates the signal based on information indicating a difference between phases for adjacent subcarriers, wherein the phases of the adjacent subcarriers are set according to the number of retransmissions.
11. A radio communication base station apparatus equipped with the radio communication apparatus as set forth in claim 1 .
12. A radio communication mobile station apparatus equipped with the radio communication apparatus as set forth in claim 8 .
13. The radio communication apparatus of claim 8 , wherein the signal is retransmitted to the radio communication apparatus in plural retransmissions by the same transmitting device with different offsets for the different retransmissions of the signal.
14. A retransmitting controlling method employed in a radio communication apparatus that performs communication by MIMO (Multi Input Multi Output) using a plurality of antennas, the retransmitting controlling method comprising:
applying a cyclic delay diversity process to a signal transmitted from at least one antenna and sets a phase of each of a plurality of subcarriers, such that the phase is changed cyclically on a frequency domain;
executing a retransmitting operation in which the radio communication apparatus retransmits data previously sent in a previous sending operation; and
setting a certain offset for each of the plurality of subcarriers that are retransmitted, wherein the offset is included in the phase of subcarriers and is set according to a number of retransmissions of the signal.
15. A radio communication system for performing communication by MIMO (Multi Input Multi Output) using a plurality of antennas, the radio communication system comprising:
a transmitting device which includes:
a cyclic delay diversity processor which applies a cyclic delay diversity process to a signal transmitted from at least one antenna and sets a phase for each of a plurality of subcarriers, such that the phase for each of the plurality of subcarriers is changed cyclically on a frequency domain;
a resending controller which is adapted to execute a retransmission of the signal; and
an offset controller which sets a certain offset that is included in the phase of each of the plurality of subcarriers on retransmission of the signal, wherein the offset is set according to a number of retransmissions of the signal; and
the receiving device which includes:
a demodulator which demodulates the signal based on offset information indicating the offset that is set according to the number of retransmissions of the signal.
16. The retransmitting controlling method of claim 14 , wherein the offset of a second retransmission of the signal sent by the transmitting device is different from another offset of a previous retransmission of the signal performed by the transmitting device.
17. The radio communication apparatus of claim 7 , wherein the second retransmission of the signal is sent after the previous retransmission of the signal.