Method of variable rate single user and multi user mimo feedback for mobile communications system

Abstract

A spatial channel state information (CSI) feedback technique is incorporated into multiple-input multiple-output mobile communications technologies. User equipment (UE) channel conditions are measured and, based on the measurements, codebook subsets are selected to which indices are assigned and fed back to a base station.

1 . A method to generate feedback in a multiple-input multiple-output (MIMO) system which comprises:
 performing at least one measurement of a channel condition;   selecting a subset of a codebook based on the at least one measurement, the subset comprising a plurality of codewords and a plurality of indices;   selecting one of the plurality of codewords based on a certain criterion and assigning one of the plurality of indices to the one of the plurality of codewords; and   transmitting a feedback signal comprising the one of the plurality of indices.   
     
     
         2 . The method of  claim 1 , wherein the codebook is predetermined. 
     
     
         3 . The method of  claim 1 , further comprising dividing a cell into a plurality of feedback rate regions, wherein each of the plurality of feedback rate regions uses a subset of a codebook having a different characterization based on average radio channel conditions. 
     
     
         4 . The method of  claim 1 , further comprising dividing a cell area into a plurality of feedback rate regions according to long term radio channel conditions. 
     
     
         5 . The method of  claim 4 , wherein the long term radio channel conditions are determined by mobile radio channel measurement reporting. 
     
     
         6 . The method of  claim 1 , further comprising determining an indication of a feedback rate region, wherein the determining is by predefined radio channel thresholds known at the mobile station and by transmission of certain messages from a base station. 
     
     
         7 . The method of  claim 1 , further comprising partitioning a plurality of codewords into multiple sub-codebooks, each sub-codebook corresponding to one of a plurality of feedback regions. 
     
     
         8 . The method of  claim 7 , wherein each sub-codebook has a different feedback granularity. 
     
     
         9 . The method of  claim 1 , wherein the one of the plurality of indices is assigned so a distance between a quantized composite spatial CSI and a floating-point composite spatial CSI is minimized. 
     
     
         10 . A method to generate feedback in a multiple-input multiple-output (MIMO) system which comprises:
 measuring, at a UE, a radio channel condition, resulting in a channel condition measurement;   reporting the channel condition measurement to a base station; and   deciding, by one of the UE and the base station, a feedback rate region classification for the UE based on the channel condition measurement.   
     
     
         11 . The method of  claim 10 , wherein the deciding is by the base station; and further comprising conveying the feedback rate region classification for the UE to the UE through a downlink signaling form. 
     
     
         12 . The method of  claim 11 , further comprising:
 measuring, by the UE, an instantaneous radio channel; and   choosing codewords from a subset of a codebook corresponding to the feedback rate region classification.   
     
     
         13 . The method of  claim 12 , further comprising choosing codewords from a subset of a codebook corresponding to the feedback rate region classification based on one of (i) a minimal distance of a codeword and a channel vector, and (ii) a maximal capacity criterion. 
     
     
         14 . The method of  claim 12 , further comprising feeding back the codewords from the UE to the base station. 
     
     
         15 . The method of  claim 14 , further comprising calculating precoding matrices by the base station. 
     
     
         16 . The method of  claim 10 , wherein the deciding is by the UE and is further based on a predefined threshold. 
     
     
         17 . The method of  claim 16 , wherein the predefined threshold is known to both the base station and the UE. 
     
     
         18 . The method of  claim 16 , further comprising choosing codewords from a subset of a codebook corresponding to the feedback rate region classification based on one of (i) a minimal distance of a codeword and a channel vector, and (ii) a maximal capacity criterion. 
     
     
         19 . The method of  claim 18 , further comprising feeding back the codewords from the UE to the base station. 
     
     
         20 . The method of  claim 19 , further comprising calculating precoding matrices by the base station. 
     
     
         21 . A system to generate feedback in a multiple-input multiple-output (MIMO) system which comprises:
 means for performing at least one measurement of a channel condition;   means for selecting a subset of a codebook based on the at least one measurement, the subset comprising a plurality of codewords and a plurality of indices;   means for selecting one of the plurality of codewords based on a certain criterion and assigning one of the plurality of indices to the one of the plurality of codewords; and   means for transmitting a feedback signal comprising the one of the plurality of indices.   
     
     
         22 . The system of  claim 21 , wherein the codebook is predetermined. 
     
     
         23 . The system of  claim 21 , further comprising means for dividing a cell into a plurality of feedback rate regions, wherein each of the plurality of feedback rate regions uses a subset of a codebook having a different characterization based on average radio channel conditions. 
     
     
         24 . The system of  claim 21 , further comprising means for dividing a cell area into a plurality of feedback rate regions according to long term radio channel conditions. 
     
     
         25 . The system of  claim 24 , wherein the long term radio channel conditions are determined by mobile radio channel measurement reporting. 
     
     
         26 . The system of  claim 21 , further comprising means for determining an indication of a feedback rate region, wherein the determining is by predefined radio channel thresholds known at the mobile station and by transmission of certain messages from a base station. 
     
     
         27 . The system of  claim 21 , further comprising means for partitioning a plurality of codewords into multiple sub-codebooks, each sub-codebook corresponding to one of a plurality of feedback regions. 
     
     
         28 . The system of  claim 27 , wherein each sub-codebook has a different feedback granularity. 
     
     
         29 . The system of  claim 21 , wherein the one of the plurality of indices is assigned so a distance between a quantized composite spatial CSI and a floating-point composite spatial CSI is minimized. 
     
     
         30 . An apparatus to generate feedback in a multiple-input multiple-output (MIMO) system comprising
 a UE configured to (i) measure a radio channel condition, resulting in a channel condition measurement, and (ii) report the channel condition measurement to a base station; and   one of the UE and the base station, configured to decide a feedback rate region classification for the UE based on the channel condition measurement.   
     
     
         31 . The apparatus of  claim 30 , wherein the base station is further configured to convey the feedback rate region classification for the UE to the UE through a downlink signaling form. 
     
     
         32 . The apparatus of  claim 31 , wherein the UE is further configured to (i) measure an instantaneous radio channel, and (ii) choose codewords from a subset of a codebook corresponding to the feedback rate region classification. 
     
     
         33 . The apparatus of  claim 32 , wherein the UE is further configured to choose codewords, from a subset of a codebook corresponding to the feedback rate region classification, based on one of (i) a minimal distance of a codeword and a channel vector, and (ii) a maximal capacity criterion. 
     
     
         34 . The apparatus of  claim 32 , wherein the UE is further configured to feed back the codewords to the base station. 
     
     
         35 . The apparatus of  claim 34 , wherein the base station is further configured to calculate precoding matrices. 
     
     
         36 . The apparatus of  claim 30 , wherein the UE is further configured to decide the feedback rate region classification for the UE further based on a predefined threshold. 
     
     
         37 . The apparatus of  claim 36 , wherein the predefined threshold is known to both the base station and the UE. 
     
     
         38 . The apparatus of  claim 36 , wherein the UE is further configured to choose codewords, from a subset of a codebook corresponding to the feedback rate region classification, based on one of (i) a minimal distance of a codeword and a channel vector, and (ii) a maximal capacity criterion. 
     
     
         39 . The apparatus of  claim 38 , wherein the UE is further configured to feed back the codewords to the base station. 
     
     
         40 . The apparatus of  claim 39 , where in the base station is further configured to calculate precoding matrices.