Mechanisms for managing user equipment on sidelink communication
Some aspects of this disclosure relate to apparatuses and methods for implementing sidelink communications among multiple user equipments (UEs). A UE operates according to a periodical discontinuous reception (DRX) cycle that includes a sidelink on-duration period when the UE is in an active state. The UE is in a power saving state outside the sidelink on-duration period. The UE listens to a Physical Sidelink Control Channel (PSCCH) for sidelink communications during the active state. A UE determines the DRX cycle and the sidelink on-duration period of a receiver UE, and sends a message to the receiver UE during one or more slots of the sidelink on-duration period when the receiver UE is in the active state.
1. A user equipment (UE), comprising:
a transceiver configured to wirelessly communicate through a first interface for sidelink communication with one or more UEs including a first receiver UE and a second receiver UE; and
a processor communicatively coupled to the transceiver and configured to:
determine a first discontinuous reception (DRX) cycle of the first receiver UE that includes a first number of slots;
determine a sidelink on-duration period within the first DRX cycle of the first receiver UE, wherein the first receiver UE is in an active state to listen to a Physical Sidelink Control Channel (PSCCH) during the sidelink on-duration period, and wherein the sidelink on-duration period includes a second number of slots within the first DRX cycle that is less than the first number of slots within the first DRX cycle, and wherein the second number of slots is larger than one slot; and
send a message, using the transceiver, to the first receiver UE during one or more slots of the sidelink on-duration period,
wherein the processor is further configured to:
determine a second DRX cycle of the second receiver UE;
determine a second sidelink on-duration period within the second DRX cycle, wherein during the second sidelink on-duration period, the second receiver UE is in the active state to listen to the PSCCH;
determine one or more slots of the second DRX cycle when the first receiver UE and the second receiver UE are both in the active state; and
send an other message, using the transceiver, to the first receiver UE and the second receiver UE in a one-to-many communication during the one or more slots when the first receiver UE and the second receiver UE are both in the active state.
2. The UE of claim 1 , wherein the transceiver is further configured to wirelessly communicate with a base station through a second interface supporting uplink and downlink transmissions between the base station and the UE, wherein the first interface is a PC5 interface and the second interface is a Uu interface.
3. The UE of claim 1 , wherein the first DRX cycle of the first receiver UE further includes a power saving state having a third number of slots, and wherein the first receiver UE refrains from listening to the PSCCH during the power saving state.
4. The UE of claim 1 , wherein the second number of slots within the sidelink on-duration period are consecutive slots.
5. The UE of claim 1 , wherein the message to the first receiver UE is carried in a sidelink medium access control (MAC) Control Element (MAC CE), and includes a configuration to define one or more slots for the first receiver UE to respond to the UE.
6. The UE of claim 1 , wherein the message is sent to the first receiver UE by a broadcast transmission, a groupcast transmission, or a unicast transmission.
7. The UE of claim 1 , wherein the first receiver UE is an in-coverage UE, an out-of-coverage UE, or a partial-coverage UE.
8. The UE of claim 1 , wherein the first DRX cycle of the first receiver UE has a same time period as the second DRX cycle of the second receiver UE with respect to a timing reference, and the sidelink on-duration period has a same time period as the second sidelink on-duration period with respect to the timing reference.
9. The UE of claim 1 , wherein the first DRX cycle of the first receiver UE has a first offset with respect to a timing reference, and the second DRX cycle of the second receiver UE has a second offset with respect to the timing reference, and wherein the first offset has a length different from a length of the second offset.
10. The UE of claim 1 , wherein the first DRX cycle of the first receiver UE has a first length, the second DRX cycle of the second receiver UE has a second length, and the first length is ½ of the second length or ¼ of the second length.
11. The UE of claim 1 , wherein the sidelink on-duration period has a length different from a length of the second sidelink on-duration period.
12. A method for operating a user equipment (UE), comprising:
receiving a configuration for a first discontinuous reception (DRX) cycle having a sidelink on-duration period within the first DRX cycle, wherein the UE is in an active state during the sidelink on-duration period, and the UE is in a power saving state outside the sidelink on-duration period, wherein the first DRX cycle includes a first number of slots, the sidelink on-duration period includes a second number of slots within the first DRX cycle, and wherein the second number of slots is larger than one slot and less than the first number of slots;
listening to a Physical Sidelink Control Channel (PSCCH) during at least one slot within the sidelink on-duration period for a message from an other UE that wirelessly communicates through a PC5 interface for sidelink communication with the UE, wherein the UE refrains from listening to PSCCH when the UE is in the power saving state, wherein the at least one slot within the sidelink on-duration period for listening to the message is shared by a receiver UE in the active state within a second DRX cycle during which to listen to the PSCCH from the other UE; and
receiving the message from the other UE, wherein the message is sent to the UE and the receiver UE in a one-to-many communication during the at least one slot when the UE and the receiver UE are both in the active state.
13. The method of claim 12 , further comprising:
receiving the message from the other UE through the PC5 interface for the sidelink communication when the UE is in the active state.
14. The method of claim 13 , further comprising:
determining, based on the received message, a configuration that defines one or more slots for the UE to respond to the other UE; and
sending a response message to the other UE based on the determined configuration.
15. The method of claim 13 , wherein the receiving the message from the other UE includes receiving the message by a broadcast transmission, a groupcast transmission, or a unicast transmission.
16. The method of claim 13 , wherein the other UE is an in-coverage UE, an out-of-coverage UE, or a partial-coverage UE.
17. A method for operating a user equipment (UE), comprising:
receiving a configuration for a first discontinuous reception (DRX) cycle having a sidelink on-duration period within the first DRX cycle, wherein the UE is in an active state during the sidelink on-duration period, and the UE is in a power saving state outside the sidelink on-duration period, wherein the first DRX cycle includes a first number of slots, and the sidelink on-duration period includes a second number of slots within the first DRX cycle, and wherein the second number of slots is larger than one slot and less than the first number of slots;
setting an activity tracking timer to keep track of the first DRX cycle and the sidelink on-duration period based on an offset with respect to a time reference;
listening to a Physical Sidelink Control Channel (PSCCH) during at least one slot within the sidelink on-duration period for a message from an other UE that wirelessly communicates through a PC5 interface for sidelink communication with the UE, wherein the at least one slot within the sidelink on-duration period for listening to the message is shared by a receiver UE in the active state within a second DRX cycle during which to listen to the PSCCH from the other UE;
receiving the message in the PSCCH from the other UE through the PC5 interface for the sidelink communication when the UE is in the active state and the message is sent to the UE and the receiver UE in a one-to-many communication during the at least one slot when the UE and the receiver UE are both in the active state; and
restarting the activity tracking timer to keep track of the first DRX cycle and the sidelink on-duration period after receiving the message.
18. The method of claim 17 , wherein the configuration for the first DRX cycle, the sidelink on-duration period, and the offset with respect to the time reference is configured in a Radio Resource Control (RRC) message from a base station that wirelessly communicates to the UE through an interface supporting uplink and downlink transmissions between the base station and the UE.
19. The method of claim 17 , wherein the setting the activity tracking timer to keep track of the first DRX cycle and the sidelink on-duration period includes:
setting a first timer to be the activity tracking timer to keep track of the first DRX cycle; and
setting a second timer to keep track the sidelink on-duration period.