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 base station (BS), the method comprising:
determining, at the base station, a mapping of each set of channel state information reference signal (CSI-RS) resources from a plurality of CSI-RS resources to a subframe set of a plurality of subframe sets;
determining, at the base station, a set of CSI-RS resources of the plurality of CSI-RS resources for feedback reporting;
transmitting, from the base station to a user equipment (UE), a request for a CSI feedback report in a subframe of one of the plurality of subframe sets, the subframe selected based on the mapping of the determined set of CSI-RS resources to the one of the plurality of subframe sets; and
receiving, at the base station from the UE, the CSI feedback report based on the set of CSI-RS resources.
2. The method of claim 1 , wherein the set of CSI-RS resources comprises a predetermined number of CSI-RS resources, wherein the predetermined number is signaled to a UE.
3. The method of claim 1 , wherein:
CSI-RS resources have a one-to-one association with subframe sets; and
the set of CSI-RS resources comprises CSI-RS resources whose subframe set contains the subframe in which the request is sent.
4. The method of claim 3 , further comprising transmitting signaling including a bitmap, the bitmap indicating the subframe sets.
5. The method of claim 1 , wherein the set of CSI-RS resources comprises multiple CSI-resources contained in a single subframe.
6. The method of claim 5 , wherein the feedback report is based on a CSI-RS resource subset, the CSI-RS resource subset having less than all CSI-RS resources contained in the single subframe.
7. The method of claim 6 , further comprising transmitting signaling indicating the CSI-RS resource subset.
8. A base station for wireless communications, comprising:
at least one processor configured to:
determine a mapping of each set of channel state information reference signal (CSI-RS) resources from a plurality of CSI-RS resources to a subframe set of a plurality of subframe sets; and
determine a set of CSI-RS resources of the plurality of CSI-RS resources for feedback reporting;
a transmitter configured to transmit, to a user equipment (UE), a request for a CSI feedback report in a subframe of one of the plurality of subframe sets, the subframe selected based on the mapping of the determined set of CSI-RS resources to the one of the plurality of subframe sets; and
a receiver configured to receive, from the UE, the CSI feedback report based on the set of CSI-RS resources.
9. The base station of claim 8 , wherein the set of CSI-RS resources comprises a predetermined number of CSI-RS resources, wherein the predetermined number is signaled to a UE.
10. The base station of claim 8 , wherein:
CSI-RS resources have a one-to-one association with subframe sets; and
the set of CSI-RS resources comprises CSI-RS resources whose subframe set contains the subframe in which the request is sent.
11. The base station of claim 10 , further comprising transmitting signaling including a bitmap, the bitmap indicating the subframe sets.
12. The base station of claim 8 , wherein the set of CSI-RS resources comprises multiple CSI-resources contained in a single subframe.
13. The base station of claim 12 , wherein the feedback report is based on a CSI-RS resource subset, the CSI-RS resource subset having less than all CSI-RS resources contained in the single subframe.
14. The base station of claim 13 , further comprising transmitting signaling indicating the CSI-RS resource subset.
15. A base station for wireless communications, comprising:
means for determining a mapping of each set of channel state information reference signal (CSI-RS) resources from a plurality of CSI-RS resources to a subframe set of a plurality of subframe sets;
means for determining a set of CSI-RS resources of the plurality of CSI-RS resources for feedback reporting;
means for transmitting a request for a CSI feedback report in a subframe of one of the plurality of subframe sets, the subframe selected based on the mapping of the determined set of CSI-RS resources to the one of the plurality of subframe sets; and
means for receiving the CSI feedback report based on the set of CSI-RS resources.
16. The base station of claim 15 , wherein the set of CSI-RS resources comprises a predetermined number of CSI-RS resources, wherein the predetermined number is signaled to a UE.
17. The base station of claim 15 , wherein:
CSI-RS resources have a one-to-one association with subframe sets; and
the set of CSI-RS resources comprises CSI-RS resources whose subframe set contains the subframe in which the request is sent.
18. The base station of claim 17 , further comprising means for transmitting signaling including a bitmap, the bitmap indicating the subframe sets.
19. The base station of claim 15 , wherein the set of CSI-RS resources comprises multiple CSI-resources contained in a single subframe.
20. The base station of claim 19 , wherein the feedback report is based on a CSI-RS resource subset, the CSI-RS resource subset having less than all CSI-RS resources contained in the single subframe.
21. The base station of claim 20 , further comprising means for transmitting signaling indicating the CSI-RS resource subset.
22. A non-transitory computer-readable medium having encoded thereon program code for wireless communications, the program code being executed by a processor and comprising:
program code to determine, at a base station, a mapping of each set of channel state information reference signal (CSI-RS) resources from a plurality of CSI-RS resources to a subframe set of a plurality of subframe sets;
program code to determine, at the base station, a set of CSI-RS resources of the plurality of CSI-RS resources for feedback reporting;
program code to transmit, from the base station to a user equipment (UE), a request for a CSI feedback report in a subframe of one of the plurality of subframe sets, the subframe selected based on the mapping of the determined set of CSI-RS resources to the one of the plurality of subframe sets; and
program code to receive, at the base station from the UE, the CSI feedback report based on the set of CSI-RS resources.