Multi-rank precoding matrix indicator (pmi) feedback in a multiple-input multiple-output (mimo) system

Abstract

In at least some embodiments, a system includes a multiple-input multiple-output (MIMO) base station and a plurality of MIMO user equipment (UE) devices in communication with the MIMO base station. The MIMO base station is configured to switch between a single-user (SU)-MIMO mode and a multiple-user (MU)-MIMO mode during communications with the plurality of MIMO UE devices based on multi-rank precoding matrix indicator (PMI) feedback received from at least one of the MIMO UE devices.

What is claimed is: 
     
         1 . A system comprising:
 a multiple-input multiple-output (MIMO) base station for use with a plurality of MIMO user equipment (UE) devices in communication with the MIMO base station;   wherein the MIMO base station includes single-user/multiple-user switching logic configured to switch between a single-user (SU)-MIMO mode and a multiple-user (MU)-MIMO mode during communications with the plurality of MIMO UE devices based on multi-rank precoding matrix indicator (PMI) feedback received from at least one of the MIMO UE devices;   wherein the multi-rank PMI feedback comprises:   a first PMI corresponding to a recommended precoding matrix for SU-MIMO communications between the MIMO base station and the plurality of MIMO UE devices, and a rank indicator (RI) corresponding to the rank value of the first PMI, and   a second PMI corresponding to a precoding matrix of a pre-defined restricted rank value applicable for MU-MIMO communications between the base station and the plurality of MIMO UE devices.   
     
     
         2 . The system of  claim 1  wherein the MIMO base station sends configuration information to at least one MIMO UE device that indicate that the MIMO UE device should report said first and second PMIs periodically, wherein the reporting periodicity of said second PMI is equal to the reporting periodicity of said first PMI. 
     
     
         3 . The system of  claim 1  wherein the MIMO base station sends configuration information to at least one MIMO UE device that indicate that the MIMO UE device should report said first and second PMIs periodically, wherein the reporting periodicity of said second PMI is not equal to the reporting periodicity of said first PMI. 
     
     
         4 . The system of  claim 1  wherein the said pre-defined restricted rank value is configured by a higher layer control signal. 
     
     
         5 . The system of  claim 1  wherein the MIMO base station encodes the reporting configuration for said first PMI and said second PMI in a UE-specific higher-layer control signal transmitted from the MIMO base station to the MIMO UE devices. 
     
     
         6 . The system of  claim 1  wherein the MIMO base station is configured to switch between the SU-MIMO mode and the MU-MIMO mode based on a schedule derived from said multi-rank PMI feedback received from different MIMO UE devices. 
     
     
         7 . The system of  claim 1  wherein the MIMO base station transmits a control signal to the UE devices to configure at least one MIMO UE device to switch from one type of multi-rank PMI feedback reporting to another type of multi-rank PMI feedback reporting. 
     
     
         8 . The system of  claim 5  wherein the higher layer control signal comprises a Radio Resource Control (RRC) configuration signal.