Apparatus and method for diversity transmission in a wireless communications system

1. A communication apparatus comprising:

a receiver which, in operation, receives a signal that includes a non-legacy preamble and a data field, the non-legacy preamble comprising a first field for indicating a number of spatial streams (Nss) in the data field and a second field for indicating one of a plurality of modulation and coding schemes (MCSs), wherein two or more frequency diversity transmission schemes are supported and one of the two or more frequency diversity transmission schemes is applied based on a value of the Nss; and

circuitry which, in operation, decodes the signal.

2. The communication apparatus according to claim 1 , wherein the non-legacy preamble comprises a third field for indicating whether at least one of the two or more frequency diversity transmission schemes is applied to the data field.

3. The communication apparatus according to claim 1 , wherein the two or more frequency diversity transmission schemes include a first scheme which is a frequency diversity scheme without spatial diversity.

4. The communication apparatus according to claim 3 , wherein if the value of the Nss equals to a first determined value and the non-legacy preamble indicates that the first scheme is applied to the data field, the first scheme is applied to at least one of the spatial streams.

5. The communication apparatus according to claim 4 , wherein the first determined value is an odd number.

6. The communication apparatus according to claim 3 , wherein the two or more frequency diversity transmission schemes include a second scheme which is a space-frequency diversity scheme (SFDS).

7. The communication apparatus according to claim 6 , wherein the first scheme and the second scheme are applied if the value of the Nss is an odd value.

8. The communication apparatus according to claim 7 , wherein more than two spatial streams are paired into Np=floor (Nss/2) spatial stream pairs and one of spatial streams is unpaired if the value of the Nss is larger than 3.

9. The communication apparatus according to claim 8 , wherein the first scheme is applied to the unpaired spatial stream and the second scheme is applied to each of the Np spatial stream pairs.

10. The communication apparatus according to claim 8 , wherein the spatial streams can be paired based on physical antenna configuration and mapping of spatial streams to antennas.

11. The communication apparatus according to claim 1 , wherein the spatial streams are grouped into Ng=floor (Nss/2) spatial stream groups if the value of the Nss is an odd value, wherein one of the Ng groups comprises three spatial streams and each of the remaining (Ng−1) groups comprises two spatial streams.

12. The communication apparatus according to claim 11 , wherein an enhanced Space Frequency Diversity Scheme (e-SFDS) is applied to a three-spatial-stream group and a SFDS is applied to each of the remaining (Ng−1) two-spatial-stream groups.

13. The communication apparatus according to claim 11 , wherein the spatial streams can be grouped based on physical antenna configuration and mapping of the spatial streams to antennas.

14. The communication apparatus according to claim 6 , wherein the second scheme is applied to the data field if the value of the Nss is an even value.

15. A communication apparatus comprising:

a receiver which, in operation, receives a signal that includes a non-legacy preamble and a data field, the non-legacy preamble comprising a first field for indicating a number of spatial streams (Nss) in the data field and a second field for indicating one of a plurality of modulation and coding schemes (MCSs), wherein two or more frequency diversity transmission schemes are supported; and

circuitry which, in operation, decodes the signal, wherein:

a first scheme of the two or more frequency diversity transmission schemes is a frequency diversity scheme without spatial diversity and

a second scheme of the two or more frequency diversity transmission schemes is a space-frequency diversity scheme, and

the first scheme is applied to at least one spatial stream if the non-legacy preamble indicates that at least one of the two or more frequency diversity transmission schemes is applied to the data field and the value of the Nss is an odd number.

16. A reception method comprising:

receiving a signal that includes a non-legacy preamble and a data field, the non-legacy preamble comprising a first field for indicating a number of spatial streams (Nss) in the data field and a second field for indicating one of a plurality of modulation and coding schemes (MCSs), wherein two or more frequency diversity transmission schemes are supported and one of the two or more frequency diversity transmission schemes is applied based on a value of the Nss; and

decoding the signal.

17. The reception method to claim 16 , wherein the non-legacy preamble comprises a third field for indicating whether at least one of the two or more frequency diversity transmission schemes is applied to the data field.

18. The reception method according to claim 16 , wherein the two or more frequency diversity transmission schemes include a first scheme which is a frequency diversity scheme without spatial diversity.

19. The reception method according to claim 18 , wherein if the value of the Nss equals to a first determined value and the non-legacy preamble indicates that the first scheme is applied to the data field, the first scheme is applied to at least one of the spatial streams.

20. The reception method according to claim 19 , wherein the first determined value is an odd number.