METHOD AND USER EQUIPMENT OF SIDELINK DISCONTINUOUS RECEPTION

1 . A method of sidelink discontinuous reception (SL-DRX), adapted to a first user equipment (UE), wherein the method comprising:

rejecting a SL-DRX configuration of a sidelink service by transmitting one of a first signaling and a second signaling with a sidelink destination identity to a serving cell of the first UE according to a cast type of the sidelink service, wherein the sidelink destination identity is associated with the sidelink service and the SL-DRX configuration is configured by the serving cell; and

in response to rejecting the SL-DRX configuration, disabling a SL-DRX mechanism for the sidelink service and the sidelink destination identity.

2 . The method of claim 1 , wherein the step of transmitting the one of the first signaling and the second signaling comprising:

transmitting the first signaling to the serving cell in response to the cast type being a sidelink unicast service.

3 . The method of claim 2 , further comprising:

transmitting a sidelink control signaling to a second UE via a PC5 radio resource control (RRC) connection between the first UE and the second UE;

receiving an SL-DRX reject message from the second UE after transmitting the sidelink control signaling; and

transmitting the first signaling to the serving cell after receiving the SL-DRX reject message.

4 . The method of claim 3 , wherein the SL-DRX reject message comprises a RRCReconfigurationCompletesidelink message, wherein the sidelink control signaling comprises a RRCReconfigurationsidelink message.

5 . The method of claim 4 , wherein the first signaling comprises a SL-DRX reject indication indicating a sidelink failure event for the PC5 RRC connection between the first UE and the second UE.

6 . The method of claim 1 , wherein the step of transmitting the one of the first signaling and the second signaling comprising:

transmitting the second signaling to the serving cell in response to the cast type being a sidelink groupcast service.

7 . The method of claim 6 , wherein the second signaling comprises a SL-DRX indication indicating the SL-DRX mechanism is not applied for the sidelink destination identity.

8 . The method of claim 1 , further comprising:

receiving the SL-DRX configuration via one of broadcasting system information and a UE- specific dedicated control signaling in response to the cast type being a sidelink groupcast service; and

applying the SL-DRX configuration to a plurality of sidelink groupcast services implemented by the first UE.

9 . The method of claim 1 , further comprising:

receiving the SL-DRX configuration via a UE-specific dedicated control signaling in response to the cast type being a sidelink unicast type.

10 . A first 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:

reject a SL-DRX configuration of a sidelink service by transmitting one of a first signaling and a second signaling with a sidelink destination identity to a serving cell of the first UE according to a cast type of the sidelink service, wherein the sidelink destination identity is associated with the sidelink service and the SL-DRX configuration is configured by the serving cell; and

determining a SL-DRX mechanism is not applied for the sidelink service and the sidelink destination identity.

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

transmit the first signaling to the serving cell in response to the cast type being a sidelink unicast service.

12 . The first UE of claim 11 , wherein the at least one processor is further configured to execute the computer-executable instructions to:

transmit a sidelink control signaling to a second UE via a PC5 radio resource control (RRC) connection between the first UE and the second UE;

receiving an SL-DRX reject message from the second UE after transmitting the sidelink control signaling; and

transmitting the first signaling to the serving cell after receiving the SL-DRX reject message.

13 . The first UE of claim 12 , wherein the SL-DRX reject message comprises a RRCReconfigurationCompletesidelink message, wherein the sidelink control signaling comprises a RRCReconfigurationsidelink message.

14 . The first UE of claim 13 , wherein the first signaling comprises a SL-DRX reject indication indicating a sidelink failure event for the PC5 RRC connection between the first UE and the second UE.

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

transmit the second signaling to the serving cell in response to the cast type being a sidelink groupcast service.

16 . The first UE of claim 15 , wherein the second signaling comprises a SL-DRX indication indicating the SL-DRX mechanism is not applied for the sidelink destination identity.

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

receive the SL-DRX configuration via one of broadcasting system information and a UE-specific dedicated control signaling in response to the cast type being a sidelink groupcast service; and

apply the SL-DRX configuration to a plurality of sidelink groupcast services implemented by the first UE.

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

receive the SL-DRX configuration via a UE-specific dedicated control signaling in response to the cast type being a sidelink unicast type.

19 . A method of sidelink discontinuous reception (SL-DRX), adapted to a base station, wherein the method comprising:

receiving a rejection of a sidelink service via one of a first signaling and a second signaling from a user equipment (UE), wherein the one of the first signaling and the second signaling is determined according to a cast type of the sidelink service; and

in response to receiving the rejection, disabling a SL-DRX mechanism for the sidelink service.