Uplink power headroom reporting for carrier aggregation
A method for reporting power headroom is disclosed. Power headroom may be reported across all carriers (wideband), for a specific carrier, or for a carrier group. The formula used to calculate the power headroom depends on whether the carrier (or a carrier in the carrier group) has a valid uplink grant. If the carrier or carrier group does not have a valid uplink grant, the power headroom may be calculated based on a reference grant. The power headroom is calculated by a wireless transmit/receive unit and is reported to an eNodeB.
1. A method comprising:
determining, via a wireless transmit/receive unit (WTRU), a carrier that does not have a physical uplink shared channel (PUSCH) transmission in a subframe i from a plurality of aggregated carriers; and
calculating, via the WTRU, a power headroom for the carrier according to the formula:
PH ( k,i )= P CMAX _ carrier ( k )− P PUSCH _ REF ( k,i )
where PH(k,i) is the power headroom for the carrier, k is a carrier number, P CMAX _ carrier (k) is a maximum power for the carrier, and P PUSCH _ REF (k,i) is a transmit power determined according to a reference grant allocation.
2. The method of claim 1 , wherein the reference grant allocation is a pre-defined allocation.
3. The method of claim 2 , wherein the pre-defined allocation is a pre-defined number of resource blocks.
4. The method according to claim 1 , wherein P CMAX _ carrier (k) is less than or equal to a P CMAX , where P CMAX is a total maximum transmit power.
5. The method of claim 1 , further comprising reporting, via the WTRU, the power headroom for the carrier.
6. The method according to claim 1 , wherein the carrier does not have a valid uplink grant.
7. A method for comprising:
determining, via a wireless transmit/receive unit (WTRU), a carrier that does not have a physical uplink shared channel (PUSCH) transmission in a subframe from one or more aggregated carriers;
determining, via the WTRU, a maximum power for the carrier; and
calculating, via the WTRU, a power headroom for the carrier using the maximum power for the carrier and a reference grant.
8. The method of claim 7 , wherein the reference grant is a pre-defined allocation.
9. The method of claim 8 , wherein the pre-defined allocation is a pre-defined number of resource blocks.
10. The method of claim 7 , further comprising reporting, via the WTRU, the power headroom.
11. The method of claim 7 , wherein the carrier does not have a valid uplink grant.
12. The method of claim 7 , further comprising calculating, via the WTRU, a reference transmit power using the reference grant.
13. The method of claim 12 , wherein calculating, via the WTRU, the power headroom for the carrier using the maximum power for the carrier and the reference grant comprises determining, via the WTRU, a difference between the maximum power for the carrier and the reference transmit power.
14. The method of claim 7 , further comprising calculating, via the WTRU, a reference transmit power using a predetermined number of resource blocks associated with the reference grant.
15. The method of claim 7 , wherein calculating, via the WTRU, the power headroom for the carrier using the maximum power for the carrier and the reference grant comprises:
calculating, via the WTRU, a reference transmit power using the reference grant; and
calculating, via the WTRU, the power headroom for the carrier using the maximum power for the carrier and the reference transmit power.
16. A wireless transmit/receive unit (WTRU) comprising:
a processor configured to:
determine a carrier that does not have a physical uplink shared channel (PUSCH) transmission in a subframe from one or more aggregated carriers;
calculate a maximum power for the carrier; and
calculate a power headroom for the carrier using the maximum power for the carrier and a reference grant.
17. The WTRU of claim 16 , wherein the reference grant is a previous grant allocation for the carrier.
18. The WTRU of claim 16 , wherein the reference grant is a grant allocation for another carrier.
19. The WTRU of claim 16 , wherein the processor is further configured to report the power headroom.
20. The WTRU of claim 16 , wherein the carrier does not have a valid uplink grant.
21. The WTRU of claim 16 , wherein the processor is further configured to calculate a reference transmit power using the reference grant.
22. The WTRU of claim 21 , wherein the processor is configured to calculate the power headroom for the carrier using the maximum power for the carrier and the reference grant by determining a difference between the maximum power for the carrier and the reference transmit power.
23. The WTRU of claim 16 , wherein the processor is configured to calculate the power headroom for the carrier using the maximum power for the carrier and the reference grant by calculating a reference transmit power using a predetermined value associated with the reference grant.
24. The WTRU of claim 16 , wherein the processor is configured to calculate the power headroom for the carrier using the maximum power for the carrier and the reference grant by:
calculating a reference transmit power using the reference grant; and
calculating the power headroom for the carrier using the maximum power for the carrier and the reference transmit power.
25. The WTRU of claim 18 , wherein the processor is further configured to calculate a reference transmit power using a pathloss estimate for the carrier, and a transmit power for another carrier.
26. The WTRU of claim 16 , wherein the processor is further configured to calculate a reference transmit power using at least one parameter of at least one carrier that has a valid uplink grant.