Method of handling HARQ resource in TDD system and related communication device

1. A method of determining hybrid automatic repeat request (HARQ) resource of an uplink (UL) subframe for an advanced communication device, the method comprising:

determining a first new association set of the UL subframe according to an association set of the UL subframe of a first UL/downlink (DL) configuration of a legacy communication device;

replacing a subset of the first new association set by a subset of an association set of the UL subframe of a second UL/DL configuration of the advanced communication device, when the legacy communication device is not able to perform a reception in at least one subframe corresponding to the subset of the first new association set;

configuring a mapping between at least one sequence index of the UL subframe of the first UL/DL configuration and the first new association set according to the first UL/DL configuration; and

determining the HARQ resource of the UL subframe according to the mapping and the first new association set;

wherein the first UL/DL configuration is a System Information Block Type 1 (SIB 1) configuration.

2. The method of claim 1 , wherein the legacy communication device is not able to perform the reception in the at least one subframe, if the at least one subframe is at least one DL subframe according to the first UL/DL configuration and is at least one UL subframe according to the second UL/DL configuration.

3. The method of claim 1 , wherein the legacy communication device is not able to perform the reception in the at least one subframe, if a network notifies the advanced communication device that the network does not schedule the at least one subframe to the legacy communication device for performing the reception.

4. The method of claim 1 , wherein each association set index of the subset of the UL subframe of the second UL/DL configuration and each association set index of the rest of the first new association set are different.

5. The method of claim 1 , further comprising:

determining a second new association set according to the association set of the UL subframe of the second UL/DL configuration; and

determining the HARQ resource of the UL subframe according to the mapping, the first new association set and the second new association set.

6. The method of claim 5 , wherein the second new association set does not overlap with the subset of the UL subframe of the second UL/DL configuration.

7. The method of claim 5 , wherein the second new association set partly overlaps with the first new association set.

8. The method of claim 5 , wherein the second new association set does not overlap with the first new association set.

9. The method of claim 5 , wherein a resource region corresponding to the first new association set does not overlap with a resource region corresponding to the second new association set.

10. The method of claim 1 , wherein when the advanced UE replaces the first new association set completely by the subset of the association set of the UL subframe of the second UL/DL configuration, the advanced UE stops configuring the mapping and determines the HARQ resource of the UL subframe according to the first new association set without using the mapping.

11. The method of claim 1 , wherein an interleaving for the first new association set is performed according to the first UL/DL configuration.

12. The method of claim 1 , wherein the step of determining the first new association set of the UL subframe according to the association set of the UL subframe of the first UL/DL configuration comprises:

determining the first new association set as the association set of the UL subframe of the first UL/DL configuration.

13. The method of claim 1 , wherein the step of configuring the mapping between the at least one sequence index of the UL subframe of the first UL/DL configuration and the first new association set according to the first UL/DL configuration comprises:

configuring the mapping as a mapping between the at least one sequence index of the UL subframe of the first UL/DL configuration and the association set of the UL subframe of the first UL/DL configuration.

14. The method of claim 1 , wherein the legacy communication device and the advanced communication device are the same communication device, the first UL/DL configuration corresponds to a first component carrier, and the second UL/DL configuration corresponds to a second component carrier.