Downlink control channel monitoring switching for unlicensed spectrum
Certain aspects of the present disclosure provide improved techniques for monitoring a downlink control channel. For example, a method includes switching, at a first time period, to monitoring a downlink control channel according to a second group of search space sets in an unlicensed spectrum. The method further includes switching, after the first time period, to monitoring the downlink control channel according to a first group of search space sets in the unlicensed spectrum based on at least one of: i) expiration of a timer started based on the switching to monitoring the downlink control channel according to the second group of search space sets; or (ii) end of a channel occupancy time (COT), of a serving cell, during which the UE monitors the downlink control channel according to the second group of search space sets.
1. A method of wireless communication by a user equipment (UE), the method comprising:
receiving signaling indicating a value of a timer for switching to monitoring according to a default group of search space sets;
switching, at a first time period, to monitoring a downlink control channel according to a non-default group of search space sets in an unlicensed spectrum; and
switching, after the first time period, to monitoring the downlink control channel according to the default group of search space sets in the unlicensed spectrum in response to expiration of the timer started based on the switching to monitoring the downlink control channel according to the non-default group of search space sets, wherein the default group of search space sets is configured for monitoring outside of a channel occupancy time (COT) of a serving cell.
2. The method of claim 1 , further comprising receiving an explicit indication identifying the non-default group of search space sets, wherein switching, at the first time period, to monitoring the downlink control channel according to the non-default group of search space sets is based on the UE receiving the explicit indication.
3. The method of claim 2 , wherein the explicit indication comprises one or more bits in a downlink control information (DCI) identifying the non-default group of search space sets.
4. The method of claim 1 , further comprising receiving a transmission from the serving cell, wherein switching, at the first time period, to monitoring the downlink control channel according to the non-default group of search space sets is based on the UE receiving the transmission from the serving cell.
5. The method of claim 1 , further comprising switching to monitoring the downlink control channel according to the default group of search space sets in response to an end of a COT.
6. The method of claim 1 , further comprising, prior to the first time period:
receiving an explicit indication identifying the default group of search space sets; and
switching to monitoring the downlink control channel according to the default group of search space sets based on receiving the explicit indication.
7. The method of claim 6 , wherein the explicit indication comprises one or more bits in a downlink control information (DCI) identifying the default group of search space sets.
8. The method of claim 1 , further comprising receiving signaling indicating one or more of:
a configuration of the default group of search space sets;
a configuration of the non-default group of search space sets;
enabling or disabling of switching between groups of search space sets;
a minimum number of symbols after which the UE is allowed to switch between groups of search space sets after determining to switch; or
a switching boundary indicating when the UE is to switch between groups after determining to switch.
9. The method of claim 8 , wherein the switching boundary comprises a slot boundary.
10. The method of claim 1 , further comprising switching, after the first time period, to monitoring the downlink control channel according to the non-default group of search space sets in the unlicensed spectrum based on expiration of a second timer started based on the switching to monitoring the downlink control channel according to the default group of search space sets.
11. The method of claim 1 , further comprising switching to monitoring the downlink control channel according to the default group of search space prior to expiration of the timer in response to the UE receiving an explicit indication identifying the default group of search space sets, the explicit indication taking priority over the timer.
12. The method claim 1 , further comprising receiving downlink control information (DCI), wherein the switching to monitoring the downlink control channel according to the default group of search space sets is in response to the expiration of the timer when the DCI does not carry a COT duration field, and wherein the switching to monitoring the downlink control channel according to the default group of search space sets is in response to the end of the COT when the DCI carries the COT duration field.
13. A method for wireless communication by a base station (BS), the method comprising:
transmitting, to a user equipment (UE), a first value for a first timer for switching to monitoring a downlink control channel according to a default group of search space sets in an unlicensed spectrum in response to expiration of the first timer started based on switching to monitoring the downlink control channel according to a non-default group of search space sets in the unlicensed spectrum, wherein the default group of search space sets is configured for monitoring outside of a channel occupancy time (COT) of a serving cell;
performing a listen-before-talk procedure to determine availability of the unlicensed spectrum; and
transmitting downlink control information to the UE in the downlink control channel based on the determined availability of the unlicensed spectrum.
14. The method of claim 13 , further comprising transmitting, to the UE, an explicit indication identifying the non-default group of search space sets for the UE to switch to monitoring the downlink control channel according to the non-default group of search space sets.
15. The method of claim 14 , wherein the explicit indication comprises one or more bits in a downlink control information (DCI) identifying the non-default group of search space sets.
16. The method of claim 13 , further comprising transmitting, to the UE, an explicit indication identifying the default group of search space sets for the UE to switch to monitoring the downlink control channel according to the default group of search space sets.
17. The method of claim 16 , wherein the explicit indication comprises one or more bits in a downlink control information (DCI) identifying the default group of search space sets.
18. The method of claim 13 , further comprising transmitting, to the UE, signaling indicating one or more of:
configuration of the default group of search space sets;
configuration of the non-default group of search space sets;
enabling or disabling of switching between groups of search space sets;
a minimum number of symbols after which the UE is allowed to switch between groups of search space sets after determining to switch; or
a switching boundary indicating when the UE is to switch between groups after determining to switch.
19. The method of claim 18 , wherein the switching boundary comprises a slot boundary.
20. The method of claim 13 , further comprising transmitting, to the UE, a second value for a second timer for switching to monitoring the downlink control channel according to the non-default group of search space sets in response to expiration of the second timer started based on switching to monitoring the downlink control channel according to the default group of search space sets.
21. An apparatus for wireless communication by a user equipment (UE), the apparatus comprising:
a memory comprising computer executable code stored thereon; and
at least one processor coupled to the memory, the at least one processor configured to execute the computer executable code and cause the apparatus to:
receive signaling indicating a value of a timer for switching to monitoring according to a default group of search space sets;
switch, at a first time period, to monitoring a downlink control channel according to a non-default group of search space sets in an unlicensed spectrum; and
switch, after the first time period, to monitoring the downlink control channel according to the default group of search space sets in the unlicensed spectrum in response to expiration of the timer started based on the switching to monitoring the downlink control channel according to the non-default group of search space sets, wherein the default group of search space sets is configured for monitoring outside of a channel occupancy time (COT) of a serving cell.
22. The apparatus of claim 21 , wherein the at least one processor is further configured to cause the apparatus to receive an explicit indication identifying the non-default group of search space sets, wherein switching, at the first time period, to monitoring the downlink control channel according to the non-default group of search space sets is based on the UE receiving the explicit indication.
23. The apparatus of claim 21 , wherein the at least one processor is further configured to cause the apparatus to receive a transmission from the serving cell, wherein switching, at the first time period, to monitoring the downlink control channel according to the non-default group of search space sets is based on the UE receiving the transmission from the serving cell.
24. The apparatus of claim 21 , wherein the at least one processor is further configured to cause the apparatus to, prior to the first time period:
receive an explicit indication identifying the default group of search space sets; and
switch to monitoring the downlink control channel according to the default group of search space sets based on receiving the explicit indication.
25. The apparatus of claim 21 , wherein the at least one processor is further configured to cause the apparatus to receive signaling indicating one or more of:
configuration of the default group of search space sets;
configuration of the non-default group of search space sets;
enabling or disabling of switching between groups of search space sets;
a minimum number of symbols after which the UE is allowed to switch between groups of search space sets after determining to switch; or
a switching boundary indicating when the UE is to switch between groups of search space sets after determining to switch.
26. The apparatus claim 21 , wherein the at least one processor is further configured to cause the apparatus to receive downlink control information (DCI), wherein the switching to monitoring the downlink control channel according to the default group of search space sets is in response to the expiration of the timer when the DCI does not carry a COT duration field, and wherein the switching to monitoring the downlink control channel according to the default group of search space sets is in response to the end of the COT when the DCI carries the COT duration field.
27. An apparatus for wireless communication by a base station (BS), the apparatus comprising:
a memory comprising computer executable code stored thereon; and
at least one processor coupled to the memory, the at least one processor configured to execute the computer executable code and cause the apparatus to:
transmit, to a user equipment (UE), a value for a timer for switching to monitoring a downlink control channel according to a default group of search space sets in an unlicensed spectrum in response to expiration of the timer after switching to monitoring the downlink control channel according to a non-default group of search space sets in the unlicensed spectrum, wherein the default group of search space sets is configured for monitoring outside of a channel occupancy time (COT) of a serving cell;
perform a listen-before-talk procedure to determine availability of the unlicensed spectrum; and
transmit downlink control information to the UE in the downlink control channel based on the determined availability of the unlicensed spectrum.
28. The apparatus of claim 27 , wherein the at least one processor is further configured to cause the apparatus to transmit, to the UE, an explicit indication identifying the non-default group of search space sets for the UE to switch to monitoring the downlink control channel according to the non-default group of search space sets.
29. The apparatus of claim 27 , wherein the at least one processor is further configured to cause the apparatus to transmit, to the UE, an explicit indication identifying the default group of search space sets for the UE to switch to monitoring the downlink control channel according to the default group of search space sets.
30. The apparatus of claim 27 , wherein the at least one processor is further configured to cause the apparatus to transmit, to the UE, signaling indicating one or more of:
configuration of the default group of search space sets;
configuration of the non-default group of search space sets;
enabling or disabling of switching between groups of search space sets;
a minimum number of symbols after which the UE is allowed to switch between groups of search space sets after determining to switch; or
a switching boundary indicating when the UE is to switch between groups of search space sets after determining to switch.