Handling FDD and TDD timing offset in FDD and TDD CA in LTE

1. A method for wireless communications, comprising:

communicating using carrier aggregation (CA) involving at least two component carriers (CCs), wherein the at least two CCs include at least one time division duplex CC (TDD CC) using a time division duplex (TDD) system configuration and at least one frequency division duplex CC (FDD CC) using a frequency division duplex (FDD) system configuration; and

determining a timing advance (TA) offset value for a user equipment (UE) to use for uplink transmissions on the at least two CCs based, at least in part, on whether the TDD CC or the FDD CC carries a physical uplink control channel (PUCCH).

2. The method of claim 1 , wherein the TA offset value comprises a same TA offset value for all CCs used to communicate in a primary cell (Pcell) or secondary cell (Scell) carrying PUCCH.

3. The method of claim 1 , wherein:

at least one CC of the at least two CCs used to communicate in a primary cell (Pcell) carries PUCCH; and

determining the TA offset value comprises determining the TA offset value based on a system type of the at least one CC used to communicate in the Pcell.

4. The method of claim 3 , wherein:

the TA offset value is determined to be a zero value if the system type of the at least one CC used to communicate in the Pcell is FDD; or

the TA offset value is determined to be a positive value to accommodate a switching gap for switching between uplink and downlink subframes if the system type of the at least one CC used to communicate in the Pcell is TDD.

5. The method of claim 1 , wherein at least one CC of the at least two CCs used to communicate in a primary cell (Pcell) and at least one CC of the at least two CCs used to communicate in a secondary cell (Scell) carries PUCCH.

6. The method of claim 5 , wherein the determining comprises determining the TA offset value based on a system type of the at least one CC used to communicate in the Pcell.

7. The method of claim 5 , wherein:

at least one CC used to communicate in the Pcell carries PUCCH;

at least one CC used to communicate in the Scell also carries PUCCH;

a first TA offset value is used for CCs used to communicate in the Pcell; and

a second TA offset value is used for CCs used to communicate in the Scell.

8. The method of claim 1 , wherein the at least one FDD CC and the at least one TDD CC are of a same timing advance group.

9. The method of claim 1 , wherein a different TA offset value is used when the TDD CC carries the PUCCH as compared to when the FDD CC carries the PUCCH.

10. An apparatus for wireless communications, comprising:

at least one processor configured to:

communicate using carrier aggregation (CA) involving at least two component carriers (CCs), wherein the at least two CCs include at least one time division duplex component carrier (TDD CC) using a time division duplex (TDD) system configuration and at least one frequency division duplex CC (FDD CC) using a frequency division duplex (FDD) system configuration, and

determine a timing advance (TA) offset value for a user equipment (UE) to use for uplink transmissions on the at least two CCs based, at least in part, on whether the TDD CC or the FDD CC carries a physical uplink control channel (PUCCH); and

a memory coupled with the at least one processor.

11. The apparatus of claim 10 , wherein the TA offset value comprises a same TA offset value for all CCs used to communicate in a primary cell (Pcell) or secondary cell (Scell) carrying PUCCH.

12. The apparatus of claim 10 , wherein:

at least one CC of the at least two CCs used to communicate in a primary cell (Pcell) carries PUCCH; and

the at least one processor configured to determine the TA offset value determines the TA offset value based on a system type of the at least one CC used to communicate in Pcell.

13. The apparatus of claim 12 , wherein:

the TA offset value is determined to be a zero value if the system type of the at least one CC used to communicate in the Pcell is FDD; or

the TA offset value is determined to be a positive value to accommodate a switching gap for switching between uplink and downlink subframes if the system type of the at least one CC used to communicate in the Pcell is TDD.

14. The apparatus of claim 10 , wherein at least one CC of the at least two CCs used to communicate in a primary cell (Pcell) and at least one CC of the at least two CCs used to communicate in a secondary cell (Scell) carries PUCCH.

15. The apparatus of claim 14 , wherein the at least one processor is configured to determine the TA offset value based on a system type of the at least one CC used to communicate in the Pcell.

16. The apparatus of claim 14 , wherein:

at least one CC used to communicate in the Pcell carries PUCCH;

at least one CC used to communicate in the Scell also carries PUCCH;

a first TA offset value is used for CCs used to communicate in the Pcell; and

a second TA offset value is used for CCs used to communicate in the Scell.

17. The apparatus of claim 10 , wherein the at least one FDD CC and the at least one TDD CC are of a same timing advance group.

18. An apparatus for wireless communications, comprising:

means for communicating using carrier aggregation (CA) involving at least two component carriers (CCs), wherein the at least two CCs include at least one time division duplex CC (TDD CC) using a time division duplex (TDD) system configuration and at least one frequency division duplex CC (FDD CC) using a frequency division duplex (FDD) system configuration; and

means for determining a timing advance (TA) offset value for a user equipment (UE) to use for uplink transmissions on the at least two CCs based, at least in part, on whether the TDD CC or the FDD CC carries a physical uplink control channel (PUCCH).

19. The apparatus of claim 18 , wherein the TA offset value comprises a same TA offset value for all CCs used to communicate in a primary cell (Pcell) or secondary cell (Scell) carrying PUCCH.

20. The apparatus of claim 18 , wherein:

at least one CC of the at least two CCs used to communicate in a primary cell (Pcell) carries PUCCH; and

the means for determining are configured to determine the TA offset value based on a system type of the at least one CC used to communicate in the Pcell.

21. The apparatus of claim 20 , wherein:

the TA offset value is determined to be a zero value if the system type of the at least one CC used to communicate in the Pcell is FDD; or

the TA offset value is determined to be a positive value to accommodate a switching gap for switching between uplink and downlink subframes if the system type of the at least one CC used to communicate in the Pcell is TDD.

22. The apparatus of claim 18 , wherein at least one CC of the at least two CCs used to communicate in a primary cell (Pcell) and at least one CC of the at least two CCs used to communicate in a secondary cell (Scell) carries PUCCH.

23. The apparatus of claim 22 , wherein the means for determining comprises means for determining the TA offset value based on a system type of the at least one CC used to communicate in the Pcell.

24. The apparatus of claim 22 , wherein:

at least one CC used to communicate in the Pcell carries PUCCH;

at least one CC used to communicate in the Scell also carries PUCCH;

a first TA offset value is used for CCs used to communicate in the Pcell; and

a second TA offset value is used for CCs used to communicate in the Scell.

25. The apparatus of claim 18 , wherein the at least one FDD CC and the at least one TDD CC are of a same timing advance group.

26. A non-transitory computer-readable medium having instructions stored thereon that, when executed by a computer, cause the computer to:

communicate using carrier aggregation (CA) involving at least two component carriers (CCs), wherein the at least two CCs include at least one time division duplex CC (TDD CC) using a time division duplex (TDD) system configuration and at least one frequency division duplex (FDD CC) using a frequency division duplex (FDD) system configuration; and

determine a timing advance (TA) offset value for a user equipment (UE) to use for uplink transmissions on the at least two CCs based, at least in part, on whether the TDD CC or the FDD CC carries a physical uplink control channel (PUCCH).