Implicitly linking aperiodic channel state information (A-CSI) reports to CSI-reference signal (CSI-RS) resources
Certain aspects of the present disclosure provide techniques for implicitly linking aperiodic channel state information (A-CSI) reports to CSI-reference signal (CSI-RS) resources. In an aspect, the UE may be instructed to report on specific CSI-RS resource(s) via explicit signaling in the UE grant. Other aspects disclose techniques for implicit CSI-RS resource selection by the UE that require fewer signaling resources. Instead of explicitly signaling CSI-RS resources to the UE, the UE may implicitly select CSI-RS resource for CSI feedback reporting based on information known to the UE, e.g. a subframe on which a reporting request is received. This may reduce the impact of the additional signaling in the UE grant.
1. A method for wireless communications by a user equipment (UE), the method comprising:
receiving, at the UE, a request for a channel state information (CSI) feedback report in a specific subframe from one subframe set of a plurality of subframe sets configured for the UE;
determining, at the UE, a subset of CSI reference signal (CSI-RS) resources from a plurality of CSI-RS resources specified for the UE for feedback reporting based at least in part on the subframe set in which the request was received, each subframe set of the plurality of subframe sets being associated with a subset of CSI-RS resources of the plurality of CSI-RS resources, a first subframe set of the plurality of subframe sets associated with a first subset of CSI-RS resources of the plurality of CSI-RS resources and a second subframe set of the plurality of subframe sets associated with a second subset of CSI-RS resources of the plurality of CSI-RS resources, and the first subset of CSI-RS resources being different from the second subset of CSI-RS resources;
generating, at the UE, the feedback report based on the subset of CSI-RS resources; and
transmitting, at the UE, the feedback report.
2. The method of claim 1 , wherein the subset of CSI-RS resources comprise CSI-RS resources of a first subframe, the first subframe being determined based on a mapping with the specific subframe.
3. The method of claim 2 , wherein the subset of CSI-RS resources comprise CSI-RS resources of a second subframe preceding the first subframe if the first subframe contains no CSI-RS resources.
4. The method of claim 3 , wherein the first subframe is the specific subframe.
5. The method of claim 1 , wherein the subset of CSI-RS resources comprise a predetermined number of CSI-RS resources signaled to the UE.
6. The method of claim 1 , wherein:
the subsets of CSI-RS resources have one-to-one associations with subframe sets.
7. The method of claim 6 , further comprising receiving signaling including a bitmap that indicates the subframe sets.
8. The method of claim 1 , wherein a plurality of subsets of CSI-RS resources are transmitted in a single subframe.
9. The method of claim 8 , wherein a number of resources in each subset of CSI-RS resources is less than all CSI-RS resources in the single subframe.
10. The method of claim 9 , further comprising receiving signaling indicating the subset of CSI-RS resources.
11. A user equipment (UE) for wireless communications, comprising:
a receiver configured to:
receive a request for a channel state information (CSI) feedback report in a specific subframe from one subframe set of a plurality of subframe sets configured for the UE;
at least one processor configured to:
determine a subset of CSI reference signal (CSI-RS) resources from a plurality of CSI-RS resources for feedback reporting based at least in part on the subframe set in which the request was received, each subframe set of the plurality of subframe sets being associated with a subset of CSI-RS resources of the plurality of CSI-RS resources, a first subframe set of the plurality of subframe sets associated with a first subset of CSI-RS resources of the plurality of CSI-RS resources and a second subframe set of the plurality of subframe sets associated with a second subset of CSI-RS resources of the plurality of CSI-RS resources, and the first subset of CSI-RS resources being different from the second subset of CSI-RS resources; and
generate the feedback report based on the subset of CSI-RS resources; and
a transmitter configured to:
transmit the feedback report.
12. The UE of claim 11 , wherein the subset of CSI-RS resources comprise CSI-RS resources of a first subframe, the first subframe being determined based on a mapping with the specific subframe.
13. The UE of claim 12 , wherein the subset of CSI-RS resources comprise CSI-RS resources of a second subframe preceding the first subframe if the first subframe contains no CSI-RS resources.
14. The UE of claim 13 , wherein the first subframe is the specific subframe.
15. The UE of claim 11 , wherein the subset of CSI-RS resources comprise a predetermined number of CSI-RS resources signaled to the UE.
16. The UE of claim 11 , wherein:
the subsets of CSI-RS resources have one-to-one associations with subframe sets.
17. The UE of claim 16 , wherein the receiver is further configured to receive signaling including a bitmap that indicates the subframe sets.
18. The UE of claim 11 , wherein a plurality of subsets of CSI-RS resources are transmitted in a single subframe.
19. The UE of claim 18 , wherein a number of resources in each subset of CSI-RS resources is less than all CSI-RS resources in the single subframe.
20. The UE of claim 19 , wherein the receiver is further configured to receive signaling indicating the subset of CSI-RS resources.
21. An apparatus for wireless communications, comprising:
means for receiving, at a user equipment (UE), a request for a channel state information (CSI) feedback report in a specific subframe from one subframe set of a plurality of subframe sets configured for the UE;
means for determining, at the UE, a subset of CSI reference signal (CSI-RS) resources from a plurality of CSI-RS resources for feedback reporting based at least in part on the subframe set in which the request was received, each subframe set of the plurality of subframe sets being associated with a subset of CSI-RS resources of the plurality of CSI-RS resources, a first subframe set of the plurality of subframe sets associated with a first subset of CSI-RS resources of the plurality of CSI-RS resources and a second subframe set of the plurality of subframe sets associated with a second subset of CSI-RS resources of the plurality of CSI-RS resources, and the first subset of CSI-RS resources being different from the second subset of CSI-RS resources;
means for generating, at the UE, the feedback report based on the subset of CSI-RS resources; and
means for transmitting, at the UE, the feedback report.
22. The apparatus of claim 21 , wherein the subset of CSI-RS resources comprise CSI-RS resources of a first subframe, the first subframe being determined based on a mapping with the specific subframe.
23. The apparatus of claim 22 , wherein the subset of CSI-RS resources comprise CSI-RS resources of a second subframe preceding the first subframe if the first subframe contains no CSI-RS resources.
24. The apparatus of claim 23 , wherein the first subframe is the specific subframe.
25. A non-transitory computer-readable medium having program code recorded thereon for wireless communication, the program code including:
program code to receive, at a user equipment (UE), a request for a channel state information (CSI) feedback report in a specific subframe from one subframe set of a plurality of subframe sets configured for the UE;
program code to determine, at the UE, a subset of CSI reference signal (CSI-RS) resources from a plurality of CSI-RS resources for feedback reporting based at least in part on the subframe set in which the request was received, each subframe set of the plurality of subframe sets being associated with a subset of CSI-RS resources of the plurality of CSI-RS resources, a first subframe set of the plurality of subframe sets associated with a first subset of CSI-RS resources of the plurality of CSI-RS resources and a second subframe set of the plurality of subframe sets associated with a second subset of CSI-RS resources of the plurality of CSI-RS resources, and the first subset of CSI-RS ports resources being different from the second subset of CSI-RS resources;
program code to generate, at the UE, the feedback report based on the subset of CSI-RS resources; and
program code to transmit, at the UE, the feedback report.