Method and apparatus for handling soft buffer size with dual connectivity in wireless communication system

1. A method for handling a soft buffer size by a user equipment (UE) in a wireless communication system, wherein the UE is connected to both a first system and a second system in dual connectivity, the method comprising:

determining a first UE capability for the first system and a second UE capability for the second system;

determining a total soft buffer size based on the first UE capability and the second UE capability; and

sharing the total soft buffer size between the first system and the second system based on at least one of a maximum transport block size (TBS) per transmission time interval (TTI) and a number of carriers used in the second system,

wherein the maximum TBS per TTI is defined per bandwidth part (BWP).

2. The method of claim 1 , wherein the sharing the total soft buffer size between the first system and the second system comprises:

determining a required soft buffer size for the second system based on at least one of the maximum TBS per TTI and the number of carriers used in the second system; and

assigning a soft buffer size which is remained after subtracting the required soft buffer size for the second system from the total soft buffer size to the first system.

3. The method of claim 2 , wherein the required soft buffer size for the second system is reported to a network.

4. The method of claim 1 , wherein the maximum TBS per TTI is a function of a minimum bandwidth of a BWP.

5. The method of claim 1 , wherein the first UE capability for the first system is defined based on a UE category in the first system or a peak data rate in the first system.

6. The method of claim 1 , wherein the second UE capability for the second system is defined based on a peak data rate in the second system.

7. The method of claim 1 , wherein the first system is a long-term evolution (LTE) system, and

wherein the second system is a new radio access technology (NR) system.

8. The method of claim 1 , wherein the UE is in communication with at least one of a mobile device, a network, and/or autonomous vehicles other than the UE.

9. A user equipment (UE) configured to operate in a wireless communication system, wherein the UE is configured to be connected to both a first system and a second system in dual connectivity, the UE comprising:

a memory;

a transceiver; and

a processor, operably coupled to the memory and the transceiver, that is configured to perform operations comprising:

determining a first UE capability for the first system and a second UE capability for the second system;

determining a total soft buffer size based on the first UE capability and the second UE capability; and

sharing the total soft buffer size between the first system and the second system based on at least one of a maximum transport block size (TBS) per transmission time interval (TTI) and a number of carriers used in the second system,

wherein the maximum TBS per TTI is defined per bandwidth part (BWP).

10. The UE of claim 9 , wherein the sharing the total soft buffer size between the first system and the second system comprises:

determining a required soft buffer size for the second system based on at least one of the maximum TBS per TTI and the number of carriers used in the second system; and

assigning a soft buffer size which is remained after subtracting the required soft buffer size for the second system from the total soft buffer size to the first system.

11. The UE of claim 10 , wherein the required soft buffer size for the second system is reported to a network.

12. The UE of claim 9 , wherein the maximum TBS per TTI is a function of a minimum bandwidth of a BWP.

13. The UE of claim 9 , wherein the first UE capability for the first system is defined based on a UE category in the first system or a peak data rate in the first system.

14. The UE of claim 9 , wherein the second UE capability for the second system is defined based on a peak data rate in the second system.