Methods and devices for packet data convergence protocol (PDCP) data transmission in wireless communication systems

1. A method performed by a User Equipment (UE), the UE having a Packet Data Convergence Protocol (PDCP) entity associated with two Radio Link Control (RLC) entities, the PDCP entity being configured with a duplication function, and the duplication function being not activated, and the method comprising:

determining, by the PDCP entity, whether the two RLC entities belong to a same cell group;

submitting, by the PDCP entity, a PDCP Data Protocol Data Unit (PDU) to a primary RLC entity of the two RLC entities, when the two RLC entities belong to a same cell group; and

submitting, by the PDCP entity, the PDCP Data PDU to one of the two RLC entities in response to a comparison result, when the two RLC entities belong to different cell groups,

wherein the PDCP entity compares a total amount of PDCP data available in the PDCP entity and RLC data available in the two RLC entities for initial transmission with an uplink data split threshold to obtain the comparison result.

2. The method according to claim 1 , further comprising:

submitting, by the PDCP entity, the PDCP Data PDU to the primary RLC entity when the total amount of PDCP data available in the PDCP entity and RLC data available in the two RLC entities for initial transmission is less than the uplink data split threshold; and

submitting, by the PDCP entity, the PDCP Data PDU to the primary RLC entity or a secondary RLC entity of the two RLC entities when the total amount of PDCP data available in the PDCP entity and RLC data available in the two RLC entities for initial transmission is equal to or larger than the uplink data split threshold.

3. The method according to claim 1 , wherein the uplink data split threshold is indicated by a base station.

4. The method according to claim 1 , wherein the primary RLC entity is associated with a first Medium Access Control (MAC) entity and a secondary RLC entity of the two RLC entities is associated with a second MAC entity, and the method further comprises:

indicating, by the PDCP entity, a first PDCP data volume and a second PDCP data volume to the first MAC entity and the second MAC entity, respectively, when the two RLC entities belong to the same cell group, wherein the second PDCP data volume is indicated as zero by the PDCP entity.

5. The method according to claim 1 , further comprising:

indicating, by the PDCP entity, a first PDCP data volume to at least one MAC entity associated with at least one of the two RLC entities in response to the comparison result, when the two RLC entities belong to different cell groups.

6. The method according to claim 5 , further comprising:

indicating, by the PDCP entity, the first PDCP data volume to a first MAC entity associated with the primary RLC entity and a second MAC entity associated with a secondary RLC entity of the two RLC entities, when the total amount of PDCP data available in the PDCP entity and RLC data available in the two RLC entities for initial transmission is equal to or larger than the uplink data split threshold; and

indicating, by the PDCP entity, the first PDCP data volume and a second PDCP data volume to the first MAC entity and the second MAC entity, respectively, when the total amount of PDCP data available in the PDCP entity and RLC data available in the two RLC entities for initial transmission is less than the uplink data split threshold, wherein the second PDCP data volume is indicated as zero by the PDCP entity.

7. The method according to claim 5 , wherein the uplink data split threshold is indicated by a base station.

8. The method according to claim 1 , wherein the primary RLC entity is indicated by a base station.

9. A User Equipment (UE) comprising:

one or more non-transitory computer-readable media having computer-executable instructions embodied thereon; and

at least one processor coupled to the one or more non-transitory computer-readable media, and configured to execute the computer-executable instructions to:

configure a Packet Data Convergence Protocol (PDCP) entity associated with two Radio Link Control (RLC) entities, wherein the PDCP entity is configured with a duplication function and the duplication function is not activated;

determine whether the two RLC entities belong to a same cell group;

submit a PDCP Protocol Data Unit (PDU) to a primary RLC entity of the two RLC entities, when the two RLC entities belong to a same cell group; and

submit the PDCP Data PDU to one of the two RLC entities in response to a comparison result, when the two RLC entities belong to different cell groups,

wherein the PDCP entity compares a total amount of PDCP data available in the PDCP entity and RLC data available in the two RLC entities for initial transmission with an uplink data split threshold to obtain the comparison result.

10. The UE according to claim 9 , wherein the at least one processor is further configured to execute the computer-executable instructions to:

submit the PDCP Data PDU to the primary RLC entity when the total amount of PDCP data available in the PDCP entity and RLC data available in the two RLC entities for initial transmission is less than the uplink data split threshold; and

submit the PDCP Data PDU to the primary RLC entity or a secondary RLC entity of the two RLC entities when the total amount of PDCP data available in the PDCP entity and RLC data available in the two RLC entities for initial transmission is equal to or larger than the uplink data split threshold.

11. The UE according to claim 9 , wherein the uplink data split threshold is indicated by a base station.

12. The UE according to claim 9 , wherein the primary RLC entity is associated with a first Medium Access Control (MAC) entity and a secondary RLC entity of the two RLC entities is associated with a second MAC entity;

the at least one processor is further configured to execute the computer-executable instructions to:

indicate a first PDCP data volume and a second PDCP data volume to the first MAC entity and the second MAC entity, respectively, when the two RLC entities belong to the same cell group;

wherein the second PDCP data volume is indicated as zero by the PDCP entity.

13. The UE according to claim 9 , wherein the at least one processor is further configured to execute the computer-executable instructions to:

indicate a first PDCP data volume to at least one MAC entity associated with at least one of the two RLC entities in response to the comparison result, when the two RLC entities belong to different cell groups.

14. The UE according to claim 13 , wherein the at least one processor is further configured to execute the computer-executable instructions to:

indicate the first PDCP data volume to a first MAC entity associated with the primary RLC entity and a second MAC entity associated with a secondary RLC entity of the two RLC entities, when the total amount of PDCP data available in the PDCP entity and RLC data available in the two RLC entities for initial transmission is equal to or larger than the uplink data split threshold; and

indicate the first PDCP data volume and a second PDCP data volume to the first MAC entity and the second MAC entity, respectively, when the total amount of PDCP data available in the PDCP entity and RLC data available in the two RLC entities for initial transmission is less than the uplink data split threshold, wherein the second PDCP data volume is indicated as zero by the PDCP entity.

15. The UE according to claim 13 , wherein the uplink data split threshold is indicated by a base station.

16. The UE according to claim 9 , wherein the primary RLC entity is indicated by a base station.