Forming carrier aggregation timing advance groups in a heterogeneous network

1. An apparatus of an eNodeB operable to maintain timing advance groups (TAGs), the apparatus comprising one or more processors and memory configured to:

form, at the eNodeB, a timing advance group (TAG) for one or more serving cells;

map, at the eNodeB, each of the one or more serving cells to the TAG using signaling from the eNodeB; and

assign, from the eNodeB, a timing advance group identifier (TAG ID) to the one or more serving cells mapped to the TAG.

2. The apparatus of claim 1 , wherein the one or more processors and memory are further configured to form the TAG for the one or more serving cells when a same timing advance applies to the one or more serving cells.

3. The apparatus of claim 1 , wherein the one or more processors and memory are further configured to map each of the one or more serving cells to the TAG using radio resource control (RRC) signaling from the eNodeB.

4. The apparatus of claim 1 , wherein the one or more processors and memory are further configured to assign the TAG ID to the one or more serving cells mapped to the TAG to enable a user equipment (UE) to maintain a separate timing advance timer for each TAG for a selected period of time.

5. The apparatus of claim 1 , wherein the one or more processors and memory are further configured to: instruct a user equipment (UE) to select a serving cell from the TAG to use as a timing reference at the UE for the one or more serving cells in the TAG.

6. The apparatus of claim 1 , wherein the TAG ID has a field length of 2 bits.

7. The apparatus of claim 1 , wherein the TAG ID is included in a timing advance command medium access control (MAC) control element (CE).

8. At least one non-transitory machine readable storage medium having instructions embodied thereon for flushing one or more hybrid automatic retransmission request (HARQ) buffers at a user equipment (UE), the instructions when executed by one or more processors performs the following:

identifying, at the UE, a timing advance group (TAG) for one or more serving cells;

determining, at the UE, when a timing advance timer for the TAG expires; and

flushing, at the UE, selected HARQ buffers for selected serving cells when the timing advance timer for the TAG expires.

9. The at least one non-transitory machine readable storage medium of claim 8 , further comprising instructions when executed by the one or more processors performs the following: flushing all HARQ buffers for all serving cells when the timing advance timer for the TAG expires.

10. The at least one non-transitory machine readable storage medium of claim 8 , wherein a TAG ID is assigned to the one or more serving cells mapped to the TAG, wherein the TAG ID has a field length of 2 bits.

11. The at least one non-transitory machine readable storage medium of claim 8 , wherein a TAG ID is assigned to the one or more serving cells mapped to the TAG, wherein the TAG ID is included in a timing advance command medium access control (MAC) control element (CE).

12. The at least one non-transitory machine readable storage medium of claim 8 , further comprising instructions when executed by the one or more processors performs the following: maintaining a separate timing advance timer for each TAG for a selected period of time.

13. The at least one non-transitory machine readable storage medium of claim 8 , wherein the UE includes an antenna, a touch sensitive display screen, a speaker, a microphone, a graphics processor, an application processor, an internal memory or a non-volatile memory port.

14. At least one non-transitory machine readable storage medium having instructions embodied thereon for maintaining timing advance groups (TAGs) at an eNodeB, the instructions when executed by one or more processors performs the following:

forming, at the eNodeB, a timing advance group (TAG) for one or more serving cells;

mapping, at the eNodeB, each of the one or more serving cells to the TAG using signaling from the eNodeB; and

assigning, from the eNodeB, a timing advance group identifier (TAG ID) to the one or more serving cells mapped to the TAG.

15. The at least one non-transitory machine readable storage medium of claim 14 , further comprising instructions when executed by the one or more processors performs the following: forming the TAG for the one or more serving cells when a same timing advance applies to the one or more serving cells.

16. The at least one non-transitory machine readable storage medium of claim 14 , further comprising instructions when executed by the one or more processors performs the following: mapping each of the one or more serving cells to the TAG using radio resource control (RRC) signaling from the eNodeB.

17. The at least one non-transitory machine readable storage medium of claim 14 , further comprising instructions when executed by the one or more processors performs the following: assigning the TAG ID to the one or more serving cells mapped to the TAG to enable a user equipment (UE) to maintain a separate timing advance timer for each TAG for a selected period of time.

18. The at least one non-transitory machine readable storage medium of claim 14 , further comprising instructions when executed by the one or more processors performs the following: instructing a user equipment (UE) to select a serving cell from the TAG to use as a timing reference at the UE for the one or more serving cells in the TAG.

19. The at least one non-transitory machine readable storage medium of claim 14 , wherein the TAG ID has a field length of 2 bits.

20. The at least one non-transitory machine readable storage medium of claim 14 , wherein the TAG ID is included in a timing advance command medium access control (MAC) control element (CE).