Reporting power headroom for aggregated carriers

1. A method for reporting power headroom-related information for a plurality of aggregated carriers, comprising:

reporting in a media access control (MAC) control element power headroom-related information for a number of the aggregated carriers that is less than or equal to the total number of aggregated carriers, wherein the power headroom-related information is one of a power headroom for at least one of the aggregated carriers and a path loss for at least one of the aggregated carriers; and

reporting in the MAC control element a bitmap, each bit in the bitmap corresponding to one of the aggregated carriers, one value in the bitmap indicating that the power headroom-related information for a corresponding carrier is being reported, and another value in the bitmap indicating that the power headroom-related information for a corresponding carrier is not being reported.

2. The method of claim 1 , wherein the power headroom-related information is reported for a representative carrier in a frequency band, the representative carrier being one of the aggregated carriers, and wherein the representative carrier is selected based on a rule known by a user agent and an access node to which the user agent sends the power headroom-related information.

3. The method of claim 1 , wherein an access node to which a user agent sends the power headroom-related information specifies a set of carriers from the total number of aggregated carriers for which the power headroom-related information is to be reported and informs the user agent of the set of carriers.

4. The method of claim 1 , wherein the reporting of the power headroom-related information is triggered by one of:

a change in the path loss of a reporting carrier among the aggregation of carriers greater than a pre-defined amount since a previous power headroom report;

addition of a carrier to the aggregation of carriers; and

expiration of a timer that controls periodic power headroom reports.

5. The method of claim 1 , wherein the power headroom-related information is reported as a result of one of:

a difference in path loss between consecutive measurements of path loss for one of the carriers exceeding a threshold;

a transmission on a carrier's physical uplink shared channel being scheduled; and

a power headroom for a carrier exceeding a threshold.

6. The method of claim 1 , wherein a physical uplink control channel (PUCCH)-related power headroom is transmitted in the MAC control element when power headroom reporting is triggered and a physical uplink shared channel (PUSCH) resource is scheduled.

7. The method of claim 6 , wherein, when the PUCCH is transmitted in the same subframe in which the PUCCH-related power headroom is reported, the PUCCH-related power headroom is calculated based on an actual transmit power of the PUCCH.

8. A user agent (UA), comprising:

a processor; and

a computer readable medium configured to store instructions such that when executed by the processor, the UA transmits in a media access control (MAC) control element power headroom-related information for a number of aggregated carriers that is less than or equal to the total number of aggregated carriers in a plurality of aggregated carriers, wherein the power headroom-related information is one of a power headroom for at least one of the aggregated carriers and a path loss for at least one of the aggregated carriers, and

wherein the UA transmits in the MAC control element a bitmap, each bit in the bitmap corresponding to one of the aggregated carriers, one value in the bitmap indicating that the power headroom-related information for a corresponding carrier is being transmitted, and another value in the bitmap indicating that the power headroom-related information for a corresponding carrier is not being transmitted.

9. The UA of claim 8 , wherein the power headroom-related information is transmitted for a representative carrier in a frequency band, the representative carrier being one of the aggregated carriers, and wherein the representative carrier is selected based on a rule known by the UA and an access node to which the UA sends the power headroom-related information.

10. The UA of claim 8 , wherein an access node to which the UA sends the power headroom-related information specifies a set of carriers from the total number of aggregated carriers for which the power headroom-related information is to be reported and informs the UA of the set of carriers.

11. The UA of claim 8 , wherein the transmitting of the power headroom-related information is triggered by one of:

a change in the path loss of a reporting carrier among the aggregation of carriers greater than a pre-defined amount since a previous power headroom report;

addition of a carrier to the aggregation of carriers; and

expiration of a timer that controls periodic power headroom reports.

12. The UA of claim 8 , wherein the power headroom-related information is transmitted as a result of one of:

a difference in path loss between consecutive measurements of path loss for one of the carriers exceeding a threshold;

a transmission on a carrier's physical uplink shared channel being scheduled; and

a power headroom for a carrier exceeding a threshold.

13. The UA of claim 8 , wherein a physical uplink control channel (PUCCH)-related power headroom is transmitted in the MAC control element when power headroom reporting is triggered and a physical uplink shared channel (PUSCH) resource is scheduled.

14. The UA of claim 13 , wherein, when the PUCCH is transmitted in the same subframe in which the PUCCH-related power headroom is reported, the PUCCH-related power headroom is calculated based on an actual transmit power of the PUCCH.

15. An access node in a wireless telecommunications system, comprising:

a component configured such that the access node receives in a media access control (MAC) control element power headroom-related information for a number of aggregated carriers that is less than or equal to the total number of aggregated carriers in a plurality of aggregated carriers, wherein the power headroom-related information is one of a power headroom for at least one of the aggregated carriers and a path loss for at least one of the aggregated carriers;

the component further configured to receive in the MAC control element a bitmap, each bit in the bitmap corresponding to one of the aggregated carriers, one value in the bitmap indicating that the power headroom-related information for a corresponding carrier is being transmitted, and another value in the bitmap indicating that the power headroom-related information for a corresponding carrier is not being transmitted.

16. The access node of claim 15 , wherein the power headroom-related information is reported for a representative carrier in a frequency band, the representative carrier being one of the aggregated carriers, and wherein the representative carrier is selected based on a rule known by the access node and a user agent from which the access node receives the power headroom-related information.

17. The access node of claim 15 , wherein the access node specifies a set of carriers from the total number of aggregated carriers for which the power headroom-related information is to be reported and informs a user agent from which the access node receives the power headroom-related information of the set of carriers for which the power headroom-related information is to be reported.

18. The access node of claim 15 , wherein the reporting of the power headroom-related information is triggered by one of:

a change in the path loss of a reporting carrier among the aggregation of carriers greater than a pre-defined amount since a previous power headroom report;

addition of a carrier to the aggregation of carriers; and

expiration of a timer that controls periodic power headroom reports.

19. The access node of claim 15 , wherein the power headroom-related information is received as a result of one of:

a difference in path loss between consecutive measurements of path loss for one of the carriers exceeding a threshold;

a transmission on a carrier's physical uplink shared channel being scheduled; and

a power headroom for a carrier exceeding a threshold.

20. The access node of claim 15 , wherein a physical uplink control channel (PUCCH)-related power headroom is received in the MAC control element when power headroom reporting is triggered and a physical uplink shared channel (PUSCH) resource is scheduled.

21. The access node of claim 20 , wherein, when the PUCCH is received in the same subframe in which the PUCCH-related power headroom is reported, the PUCCH-related power headroom is calculated based on an actual transmit power of the PUCCH.