CSI feedback overhead reduction for FD-MIMO
Mechanisms for reduction of channel state information (CSI) feedback overhead are disclosed for full dimensional multiple input, multiple output (FD-MIMO) systems with large dimension antenna ports. In one aspect, rank-dependent CSI antenna port measurements are used in order to limit the number of antenna ports for high rank CSI reporting. Another aspect allows a user equipment (UE) to select subband feedback for aperiodic CSI porting on an uplink shared channel when the UE is to report subband quality and precoding indicators. Another aspect provides for on-demand CSI feedback that dynamically configures CSI feedback parameters. To reduce the signaling overhead, the multiple parameter sets may be pre-configured with different values for dynamic reporting parameters.
1. A method of wireless communication, comprising:
receiving, at a user equipment (UE), an indication to report channel quality and precoding feedback for a plurality of channel state information reference signal (CSI-RS) ports in a full dimensional multiple input, multiple output (FD-MIMO) downlink transmission;
transmitting, by the UE, a first lower-order rank channel quality and precoding feedback for each of the plurality of CSI-RS ports, wherein the first channel quality and precoding feedback includes a low rank indicator;
selecting, by the UE, a second subset of CSI-RS ports of the plurality of CSI-RS ports for a second higher-order rank channel quality and precoding feedback, wherein the selecting the second subset of CSI-RS ports, which represent a fewer number of ports than a total number of the plurality of CSI-RS ports, is based on a rank indicator associated with the second higher-order rank channel quality and precoding feedback; and
transmitting, by the UE, the second higher-order rank channel quality and precoding feedback for each of the second subset of CSI-RS ports.
2. The method of claim 1 , wherein the selecting includes:
receiving, at the UE, a bitmap indicator signal from a serving base station, wherein the bitmap indicator signal identifies the CSI-RS ports in the plurality of CSI-RS ports for the second higher-order rank channel quality and precoding feedback; and
selecting the second subset of CSI-RS ports using the bitmap indictor.
3. The method of claim 1 , wherein the selecting includes:
receiving, at the UE, weighting information from a serving base station; and
mapping, by the UE, the plurality of CSI-RS ports into the second subset of CSI-RS ports using the weighting information.
4. The method of claim 1 , further including:
determining, by the UE, weighting information based on the first lower-order rank channel quality and precoding feedback; and
mapping, by the UE, the plurality of CSI-RS ports into the second subset of CSI-RS ports using the weighting information.
5. An apparatus configured for wireless communication, comprising:
means for receiving, at a user equipment (UE), an indication to report channel quality and precoding feedback for a plurality of channel state information reference signal (CSI-RS) ports in a full dimensional multiple input, multiple output (FD-MIMO) downlink transmission;
means for transmitting, by the UE, a first lower-order rank channel quality and precoding feedback for each of the plurality of CSI-RS ports, wherein the first lower-order rank channel quality and precoding feedback includes a low rank indicator; and
means for selecting, by the UE, a second subset of CSI-RS ports of the plurality of CSI-RS ports for a higher-order rank second channel quality and precoding feedback, wherein the selecting the second set of CSI-RS ports, which represent a fewer number of ports than a total number of the plurality of CSI-RS ports, is based on a rank indicator associated with the second higher-order rank channel quality and precoding feedback;
means for transmitting, by the UE, a second higher-order rank channel quality and precoding feedback for each of a second subset of CSI-RS ports.
6. The apparatus of claim 5 , wherein the means for selecting includes:
means for receiving, at the UE, a bitmap indicator signal from a serving base station, wherein the bitmap indicator signal identifies the CSI-RS ports in the plurality of CSI-RS ports for the second higher-order rank channel quality and precoding feedback; and
means for selecting the second subset of CSI-RS ports using the bitmap indictor.
7. The apparatus of claim 5 , wherein the means for selecting includes:
means for receiving, at the UE, weighting information from a serving base station; and
means for mapping, by the UE, the plurality of CSI-RS ports into the second subset of CSI-RS ports using the weighting information.
8. The apparatus of claim 5 , further including:
means for determining, by the UE, weighting information based on the first lower-order rank channel quality and precoding feedback; and
means for mapping, by the UE, the plurality of CSI-RS ports into the second subset of CSI-RS ports using the weighting information.