Techniques for cross-carrier scheduling from a secondary cell to a primary cell
Methods, systems, and devices for wireless communications are described. A user equipment (UE) may be configured to monitor search spaces on a primary cell and an secondary cell in a carrier aggregation configuration. The UE may monitor the search spaces for control information according to a shared search space monitoring configuration. Based on the shared search space monitoring configuration, the UE may identify that the secondary cell is a scheduling cell and the primary cell is a scheduled cell (e.g., cross-carrier scheduling). The UE may monitor control channel candidates of search spaces on the primary cell and on the secondary cell for downlink control information messages scheduling data transmissions with the primary cell. In some examples, the cross-carrier scheduled communications may be configured according to a scheduling configuration, which may include one or more scheduling constraints.
1. A method for wireless communications at a user equipment (UE), comprising:
identifying that the UE is in communication with a primary cell and one or more secondary cells in a carrier aggregation configuration, wherein the primary cell is a cross-carrier scheduled cell and a first secondary cell is a cross-carrier scheduling cell;
monitoring respective UE-specific search spaces of the one or more secondary cells for control information in accordance with a shared search space monitoring configuration;
determining a limit corresponding to the shared search space monitoring configuration, wherein the limit is associated with a maximum number of blind decodes to be attempted by the UE, a maximum number of non-overlapping control channel elements, or both, across control channel candidates of the UE-specific search space of the first secondary cell;
receiving an indication of the limit from the first secondary cell, wherein determining the limit is based at least in part on receiving the indication;
receiving one or more downlink control information messages as a result of monitoring the UE-specific search space of the first secondary cell, wherein the one or more downlink control information messages schedule one or more data transmissions and include a cross-carrier scheduling indication that the one or more data transmissions are scheduled with the primary cell; and
communicating with the primary cell via the data transmission in accordance with at least one of the one or more downlink control information messages.
2. The method of claim 1 , further comprising:
identifying a respective carrier indicator field in each of the one or more downlink control information messages, wherein the cross-carrier scheduling indication is a value included in one of the respective carrier indicator fields.
3. The method of claim 1 , further comprising:
receiving an indication of the shared search space monitoring configuration consistent with the limit, wherein the monitoring is further in accordance with the limit.
4. The method of claim 1 , further comprising:
receiving an indication of the shared search space monitoring configuration, wherein the shared search space monitoring configuration includes a number of blind decodes that exceeds the maximum number of blind decodes associated with the limit, a number of non-overlapping control channel elements that exceeds the maximum number of non-overlapping control channel elements associated with the limit, or both;
identifying a second UE-specific search space of the first secondary cell included in the shared search space monitoring configuration; and
refraining from monitoring the second UE-specific search space of the first secondary cell in accordance with the limit.
5. The method of claim 1 , further comprising:
receiving a second downlink control information message as a result of the monitoring, wherein the second downlink control information message includes a second scheduling indication that a second data transmission is scheduled with the first secondary cell; and
communicating with the first secondary cell via the second data transmission in accordance with the second downlink control information message.
6. The method of claim 1 , further comprising:
receiving a third downlink control information message as a result of the monitoring, wherein the third downlink control information message includes a third scheduling indication that a third data transmission is scheduled with the primary cell; and
communicating with the primary cell via the third data transmission in accordance with the third downlink control information message.
7. The method of claim 1 , wherein:
the shared search space monitoring configuration includes control channel candidates associated with the one or more downlink control information messages that include the cross-carrier scheduling indication; and
the control channel candidates associated with the one or more downlink control information messages are not included in UE-specific search spaces unassociated with the cross-carrier scheduling indication.
8. The method of claim 1 , wherein:
the shared search space monitoring configuration includes control channel candidates associated with the one or more downlink control information messages that include the cross-carrier scheduling indication; and
one or more of the control channel candidates associated with the one or more downlink control information messages are included in a second UE-specific search space not associated with the cross-carrier scheduling indication.
9. The method of claim 1 , further comprising:
reporting an indication of a capability of the UE to support shared search space control channel candidates in UE-specific search spaces not associated with the cross-carrier scheduling indication, wherein the shared search space monitoring configuration is based at least in part on the capability.
10. The method of claim 1 , wherein communicating with the primary cell via the data transmission comprises:
receiving a downlink data transmission from the primary cell, transmitting an uplink data transmission to the primary cell, or both.
11. An apparatus for wireless communications at a user equipment (UE), comprising:
one or more processors, one or more memories coupled with the one or more processors; and
instructions stored in the one or more memories and executable by the one or more processors to cause the apparatus to:
identify that the UE is in communication with a primary cell and one or more secondary cells in a carrier aggregation configuration, wherein the primary cell is a cross-carrier scheduled cell and a first secondary cell is a cross-carrier scheduling cell;
monitor respective UE-specific search spaces of the one or more secondary cells for control information in accordance with a shared search space monitoring configuration;
determine a limit corresponding to the shared search space monitoring configuration, wherein the limit is associated with a maximum number of blind decodes to be attempted by the UE, a maximum number of non-overlapping control channel elements, or both, across control channel candidates of the UE-specific search space of the first secondary cell;
receive an indication of the limit from the first secondary cell, wherein determining the limit is based at least in part on receiving the indication;
receive one or more downlink control information messages as a result of monitoring the UE-specific search space of the first secondary cell, wherein the one or more downlink control information messages schedule one or more data transmissions and include a cross-carrier scheduling indication that the one or more data transmissions are scheduled with the primary cell; and
communicate with the primary cell via the data transmission in accordance with at least one of the one or more downlink control information messages.
12. The apparatus of claim 11 , wherein the instructions are further executable by the one or more processors to cause the apparatus to:
identify a respective carrier indicator field in each of the one or more downlink control information messages, wherein the cross-carrier scheduling indication is a value included in one of the respective carrier indicator fields.
13. The apparatus of claim 11 , wherein the instructions are further executable by the one or more processors to cause the apparatus to:
receive a second downlink control information message as a result of the monitoring, wherein the second downlink control information message includes a second scheduling indication that a second data transmission is scheduled with the first secondary cell; and
communicate with the first secondary cell via the second data transmission in accordance with the second downlink control information message.
14. The apparatus of claim 11 , wherein the instructions are further executable by the one or more processors to cause the apparatus to:
receive a third downlink control information message as a result of the monitoring, wherein the third downlink control information message includes a third scheduling indication that a third data transmission is scheduled with the primary cell; and
communicate with the primary cell via the third data transmission in accordance with the third downlink control information message.
15. The apparatus of claim 11 , wherein:
the shared search space monitoring configuration includes control channel candidates associated with the one or more downlink control information messages that include the cross-carrier scheduling indication; and
the control channel candidates associated with the one or more downlink control information messages are not included in UE-specific search spaces unassociated with the cross-carrier scheduling indication.
16. The apparatus of claim 11 , wherein:
the shared search space monitoring configuration includes control channel candidates associated with the one or more downlink control information messages that include the cross-carrier scheduling indication, and
one or more of the control channel candidates associated with the one or more downlink control information messages are included in a second UE-specific search space not associated with the cross-carrier scheduling indication.
17. The apparatus of claim 11 , wherein the instructions are further executable by the one or more processors to cause the apparatus to:
report an indication of a capability of the UE to support shared search space control channel candidates in UE-specific search spaces not associated with the cross-carrier scheduling indication, wherein the shared search space monitoring configuration is based at least in part on the capability.
18. The apparatus of claim 11 , wherein the instructions to communicate with the primary cell via the data transmission are executable by the one or more processors to cause the apparatus to:
receive a downlink data transmission from the primary cell, transmit an uplink data transmission to the primary cell, or both.
19. An apparatus for wireless communications at a user equipment (UE), comprising:
means for identifying that the UE is in communication with a primary cell and one or more secondary cells in a carrier aggregation configuration, wherein the primary cell is a cross-carrier scheduled cell and a first secondary cell is a cross-carrier scheduling cell;
means for monitoring respective UE-specific search spaces of the one or more secondary cells for control information in accordance with a shared search space monitoring configuration;
means for determining a limit corresponding to the shared search space monitoring configuration, wherein the limit is associated with a maximum number of blind decodes to be attempted by the UE, a maximum number of non-overlapping control channel elements, or both, across control channel candidates of the UE-specific search space of the first secondary cell;
means for receiving an indication of the limit from the first secondary cell, wherein determining the limit is based at least in part on receiving the indication;
means for receiving one or more downlink control information messages as a result of monitoring the UE-specific search space of the first secondary cell, wherein the one or more downlink control information messages schedule one or more data transmissions and include a cross-carrier scheduling indication that the one or more data transmissions are scheduled with the primary cell; and
means for communicating with the primary cell via the data transmission in accordance with at least one of the one or more downlink control information messages.
20. A non-transitory computer-readable medium storing code for wireless communications at a user equipment (UE), the code comprising instructions executable by one or more processors to:
identify that the UE is in communication with a primary cell and one or more secondary cells in a carrier aggregation configuration, wherein the primary cell is a cross-carrier scheduled cell and a first secondary cell is a cross-carrier scheduling cell;
monitor respective UE-specific search spaces of the one or more secondary cells for control information in accordance with a shared search space monitoring configuration;
determine a limit corresponding to the shared search space monitoring configuration, wherein the limit is associated with a maximum number of blind decodes to be attempted by the UE, a maximum number of non-overlapping control channel elements, or both, across control channel candidates of the UE-specific search space of the first secondary cell;
receive an indication of the limit from the first secondary cell, wherein determining the limit is based at least in part on receiving the indication;
receive one or more downlink control information messages as a result of monitoring the UE-specific search space of the first secondary cell, wherein the one or more downlink control information messages schedule one or more data transmissions and include a cross-carrier scheduling indication that the one or more data transmissions are scheduled with the primary cell; and
communicate with the primary cell via the data transmission in accordance with at least one of the one or more downlink control information messages.