Signalling of channel information

1. An apparatus comprising:

a processor configured to generate a request for providing aperiodic channel information with respect to a selected downlink component carrier of a plurality of non-contiguous component carriers of an orthogonal frequency-division multiple access (OFDMA) communication system; and

a transmitting unit configured to send the request for providing the aperiodic channel information on the selected downlink component carrier for which the aperiodic channel information is to be provided.

2. The apparatus according to claim 1 , further comprising a receiver configured to receive aperiodic channel information sent in response to the request for providing aperiodic channel information.

3. The apparatus according to claim 1 , wherein the processor is further configured to generate an indicator for determining the selected downlink component carrier, and the transmitting unit is configured to send the indicator with the request for providing aperiodic channel information.

4. The apparatus according to claim 3 , wherein the request for providing aperiodic channel information and the indicator are included in an uplink grant.

5. The apparatus according to claim 1 , wherein the selected downlink component carrier is a predetermined downlink component carrier.

6. The apparatus according to claim 5 , wherein the predetermined downlink component carrier is a primary downlink component carrier.

7. The apparatus according to claim 5 , wherein the predetermined downlink component carrier is configured using control signaling.

8. The apparatus according to claim 1 , wherein the processor is further configured to include the request for providing aperiodic channel information in an uplink grant, the uplink grant comprising a combined indication of a scheduled uplink component carrier and the selected downlink component carrier.

9. The apparatus according to claim 8 , wherein the processor is further configured to include the combined indication in a carrier indicator field.

10. The apparatus according to claim 1 , wherein the processor is further configured to include the request for providing aperiodic channel information in an uplink grant, and to include, when the aperiodic channel information is requested to be transmitted without simultaneous uplink data, the request for providing aperiodic channel information in unused signaling bits or states, or some of the signaling bits or states are reinterpreted with the request for providing aperiodic channel information.

11. The apparatus according to claim 1 , wherein the processor is further configured to generate a request for providing channel information for at least one of the other component carriers than the selected component carrier.

12. The apparatus according to claim 11 , wherein the channel information for the at least one of the other component carriers is a wideband channel information.

13. The apparatus according to claim 1 , wherein the processor is further configured to include the request for providing aperiodic channel information in an uplink grant.

14. A method comprising:

generating a request for providing aperiodic channel information with respect to a selected downlink component carrier of a plurality of non-contiguous component carriers of an orthogonal frequency-division multiple access (OFDMA) communication system; and

sending the request for providing the aperiodic channel information on the selected downlink component carrier for which the aperiodic channel information is to be provided.

15. The method according to claim 14 , further comprising receiving aperiodic channel information sent in response to the request for providing aperiodic channel information.

16. The method according to claim 14 , further comprising generating an indicator for determining the selected downlink component carrier, the indicator being sent with the request for providing aperiodic channel information.

17. The method according to claim 16 , wherein the request for providing aperiodic channel information and the indicator are included in an uplink grant.

18. The method according to claim 14 , wherein the selected downlink component carrier is a predetermined downlink component carrier.

19. The method according to claim 18 , wherein the predetermined downlink component carrier is a primary downlink component carrier.

20. The method according to claim 18 , wherein the predetermined downlink component carrier is configured using control signaling.

21. The method according to claim 14 , further comprising including the request for providing aperiodic channel information included in an uplink grant, the uplink grant comprising a combined indication of a scheduled uplink component carrier and the selected downlink component carrier.

22. The method according to claim 21 , wherein the combined indication is included in a carrier indicator field.

23. The method according to claim 14 , further comprising including the request for providing aperiodic channel information in an uplink grant, and, including the request for providing aperiodic channel information in unused signaling bits or states or some of the signaling bits or states are reinterpreted with the request for providing aperiodic channel information, when the aperiodic channel information is requested to be transmitted without simultaneous uplink data.

24. The method according to claim 14 , further comprising generating a request for providing channel information for at least one of the other component carriers than the selected component carrier.

25. The method according to claim 24 , wherein the channel information for the at least one of the other component carriers is a wideband channel information.

26. The method according to claim 14 , wherein the request for providing aperiodic channel information is included in an uplink grant.