Downlink signaling for partially precoded CSI-RS and CSI feedback
User equipment (UE) is configured to receive two types of channel state information (CSI) reference signals (CSI-RS), the first containing more antenna ports and measured less often than the second. A first CSI report is based on first type CSI-RS and a second CSI report on the second type CSI-RS. The second type CSI-RS is at least partially precoded in response to the first CSI report, is precoded for the specific UE, and is transmitted more often than the first type CSI-RS, while the first type CSI-RS is not precoded. The first CSI report contains a first precoding matrix indicator (PMI) parameter and the second CSI report contains only a second PMI parameter of a two-PMI codebook, where the first PMI parameter is a long-term and wideband PMI. The first PMI is derived from measuring the first type CSI-RS in a plurality of subframes and resource blocks.
1. A base station, comprising:
a transmitter configured to transmit a signal configuring a user equipment with receiving two channel state information (CSI) reference signal (CSI-RS) resources, wherein a first of the two CSI-RS resources contains more ports and is measured less often than a second of the two CSI-RS resources;
a receiver configured to receive two types of CSI reports from the user equipment, a first of the two types of CSI reports associated with the first CSI-RS resource and a second of the two types of CSI reports associated with the second CSI-RS resource; and
a controller configured to apply a precoder across ports associated with the second CSI-RS resource in response to the first type CSI report,
wherein the transmitter is configured to transmit the first CSI-RS resource in a first set of subframes and the second CSI-RS resource in a second set of subframes.
2. The base station according to claim 1 , wherein the first CSI-RS resource is not precoded.
3. The base station according to claim 1 , wherein the second CSI-RS resource is precoded specifically for the user equipment.
4. The base station according to claim 1 , wherein the first type CSI report contains a first precoding matrix indicator (PMI) parameter of a two-PMI codebook, and the second type CSI report contains a PMI parameter of a one-PMI codebook.
5. The base station according to claim 4 , wherein the first PMI parameter is calculated from a plurality of subframes and resource blocks carrying the first CSI-RS resource.
6. The base station according to claim 4 , wherein the first PMI parameter is a long-term and wideband PMI.
7. A user equipment, comprising:
a processor configured to
measure channel state information reference signals (CSI-RS) of at least a first CSI-RS resource and a second CSI-RS resource, wherein the first CSI-RS resource corresponds to more ports than the second CSI-RS resource and wherein the first CSI-RS resource is measured less often than the second CSI-RS resource, and
calculate two types of CSI reports, wherein a first of the two types of CSI reports is generated in response to the first CSI-RS resource and a second of the two types of CSI reports is generated in response to the second CSI-RS resource, wherein a precoder to be applied across ports associated with the second CSI-RS resource is determined in response to the first type CSI report; and
a transmitter configured to report the two types of CSI reports.
8. The user equipment according to claim 7 , wherein the first CSI-RS resource is not precoded.
9. The user equipment according to claim 7 , wherein the second CSI-RS resource is precoded specifically for the user equipment.
10. The user equipment according to claim 7 , wherein the first type CSI report contains at least a first precoding matric indicator (PMI) parameter of a two-PMI codebook and the second type CSI report contains a PMI parameter of a one-PMI codebook.
11. The user equipment in claim 10 , wherein the first PMI parameter is calculated from a plurality of subframes and resource blocks carrying the first CSI-RS resource.
12. The user equipment in claim 10 , wherein the first PMI parameter is a long-term and wideband PMI.
13. A method of operating a base station, comprising:
transmitting a signal configuring a user equipment with receiving two channel state information (CSI) reference signal (CSI-RS) resources, wherein a first of the two CSI-RS resources contains more ports and is measured less often than a second of the two CSI-RS resources;
receiving two types of CSI reports from the user equipment, a first of the two types of CSI reports associated with the first CSI-RS resource and a second of the two types of CSI reports associated with the second CSI-RS resource;
applying a precoder across ports associated with the second CSI-RS resource in response to the first type CSI report;
transmitting the first CSI-RS resource in a first set of subframes and the second CSI-RS resource in a second set of subframes.
14. The method according to claim 13 , wherein the first CSI-RS resource is not precoded and the second CSI-RS resource is precoded specifically for the user equipment.
15. The method according to claim 13 , wherein the first type CSI report contains a first precoding matrix indicator (PMI) parameter of a two-PMI codebook, and the second type CSI report contains a PMI parameter of a one-PMI codebook.
16. The method according to claim 15 , wherein the first PMI parameter is a long-term and wideband PMI calculated from a plurality of subframes and resource blocks carrying the first CSI-RS resource.
17. A method of operating a user equipment, comprising:
measuring channel state information reference signals (CSI-RS) of at least a first CSI-RS resource and a second CSI-RS resource, wherein the first CSI-RS resource corresponds to more ports than the second CSI-RS resource and wherein the first CSI-RS resource is measured less often than the second CSI-RS resource;
calculating two types of CSI reports, wherein a first of the two types of CSI reports is generated in response to the first CSI-RS resource and a second of the two types of CSI reports is generated in response to the second CSI-RS resource, wherein a precoder to be applied across ports associated with the second CSI-RS resource is determined in response to the first CSI report; and
reporting the two types of CSI reports.
18. The method according to claim 17 , wherein the first CSI-RS resource is not precoded and the second CSI-RS resource is precoded specifically for the user equipment.
19. The method according to claim 17 , wherein the first type CSI report contains a first precoding matrix indicator (PMI) parameter of a two-PMI codebook, and the second type CSI report contains a PMI parameter of a one-PMI codebook.
20. The method according to claim 19 , wherein the first PMI parameter is is a long-term and wideband PMI calculated from a plurality of subframes and resource blocks carrying the first CSI-RS resource.