Method for communicating in a mimo context

Abstract

A primary station includes an array of transmit antennas to communicate with at least one secondary station on a downlink channel; at least one processor coupled to a memory, the at least one processor being configured to: generate a pre-coding to be applied during a corresponding transmission to the at least one secondary station for each transmit antenna in the array; apply a reversible transform to the pre-coding, the pre-coding being independent of data to be transmitted to the secondary station during said corresponding transmission to the secondary station so as to generate a set of pre-coding coefficients representative of the pre-coding in a transform domain; generate a set of parameters comprising at least one parameter indicative of the set of pre-coding coefficients; signal the set of parameters to the secondary station; and transmit data to the secondary station in accordance with the pre-coding.

1 . A primary station comprising:
 an array of transmit antennas to communicate with at least one secondary station on a downlink channel;   at least one processor coupled to a memory, the at least one processor being configured to:   generate a pre-coding to be applied during a corresponding transmission to the at least one secondary station for each transmit antenna in the array;   apply a reversible transform to the pre-coding, the pre-coding being independent of data to be transmitted to the secondary station during said corresponding transmission to the secondary station so as to generate a set of pre-coding coefficients representative of the pre-coding in a transform domain;   generate a set of parameters comprising at least one parameter indicative of the set of pre-coding coefficients;   signal the set of parameters to the secondary station; and   transmit data to the secondary station in accordance with the pre-coding.   
     
     
         2 . The primary station of  claim 1 , wherein the at least one processor is further configured to receive channel state information from a secondary station. 
     
     
         3 . The primary station of  claim 2 , wherein the at least one processor is configured to generate the pre-coding based at least partially on the channel state information. 
     
     
         4 . The primary station of  claim 1 , wherein the at least one processor is configured to generate the pre-coding so as to maximize a data rate. 
     
     
         5 . The primary station of  claim 1 , wherein the at least one processor is further configured to select the secondary station from a plurality of secondary stations. 
     
     
         6 . The primary station of  claim 5 , wherein the at least one processor is configured to select the secondary station from the plurality of secondary stations based at least partially on an indication of a channel quality of each secondary station. 
     
     
         7 . The primary station of  claim 5 , wherein the at least one processor is configured to select the secondary station from the plurality of secondary stations based at least partially on an indication of a priority of data to be transmitted to each secondary station. 
     
     
         8 . The primary station of  claim 5 , wherein to select the secondary station the at least one processor is configured to:
 select a first secondary station; and   select further secondary stations having channel properties that are not highly correlated with those of the first secondary station.   
     
     
         9 . The primary station of  claim 1 , wherein the at least one processor is configurede to select the secondary station such that a total data throughput is maximized. 
     
     
         10 . The primary station of  claim 1 , wherein the reversible transform is linear and orthogonal. 
     
     
         11 . The primary station of  claim 10 , wherein to apply the reversible transform to the pre-coding the at least one processor is configured to apply an Inverse Discrete Fourier transform to the set of precoding coefficients. 
     
     
         12 . The primary station of  claim 10 , wherein the set of parameters is based on a co-efficient from the set of precoding coefficients in an angular domain having a maximum magnitude. 
     
     
         13 . A secondary station comprising:
 an array of reception antennas for communicating with a base station on a downlink channel;   at least one processor coupled to a memory, the at least one processor being configured to:   determine channel state information;   transmit the channel state information to the base station;   receive a set of parameters from the base station comprising at least one parameter, said at least one parameter being representative of a set of pre-coding coefficients in an angular domain obtained by applying a reversible transform to a pre-coding, wherein said pre-coding is independent of data to be received by the secondary station, the pre-coding coefficients being based at least partially on the channel state information;   derive a phase reference depending on said set of parameters; and   receive data from the base station according to the phase reference.   
     
     
         14 . The secondary station of  claim 13 , wherein the channel state information comprises an estimate of a preferred direction of a transmission beam from the base station. 
     
     
         15 . The secondary station of  claim 13 , wherein the at least one processor is further configured to measure a downlink transfer function for each sub-carrier and each transmit antenna of the base station. 
     
     
         16 . A base station comprising:
 a memory;   an array of transmit antennas to communicate with user equipment over a downlink channel;   at least one processor configured to:
 generate pre-coding coefficients for each transmit antenna in the array of transmit antennas, the pre-coding coefficients being based at least partially on channel state information associated with the user equipment; 
 translate the pre-coding coefficients into a set of pre-coding coefficients indicative of pre-coding in an angular domain; 
 generate indices associated with the set of pre-coding coefficients indicative of pre-coding in the angular domain; 
 transmit at least the indices to the user equipment; and 
 transmit data to the user equipment in accordance with the set of pre-coding coefficients associated with the indices. 
   
     
     
         17 . The base station of  claim 16 , wherein the channel state information comprises measurements associated with a transfer function of a downlink channel from each transmit antenna in the array of transmit antennas. 
     
     
         18 . The base station of  claim 16 , wherein the at least one processor is further configured to select at least one user equipment for communication over the downlink channel. 
     
     
         19 . The base station of  claim 18 , wherein the at least one processor is further configured to select the at least one user equipment based at least partially on channel quality. 
     
     
         20 . The base station of  claim 19 , wherein the at least one processor is further configured to select the at least one user equipment based at least partially on a priority of data to be transmitted to the at least one user equipment. 
     
     
         21 . The base station of  claim 16 , wherein the at least one processor is configured to employ zero forcing beam forming to generate the pre-coding coefficients for each transmit antenna. 
     
     
         22 . The base station of  claim 16 , wherein the at least one processor is further configured to utilize a reversible transform to translate the pre-coding coefficients into coefficients in the angular domain. 
     
     
         23 . The base station of  claim 22 , wherein the reversible transform is liner and orthogonal. 
     
     
         24 . The base station of  claim 16 , wherein the at least one processor is further configured to utilize Inverse Discrete Fourier Transform to translate the pre-coding coefficients into coefficients in the angular domain. 
     
     
         25 . A mobile station comprising:
 a memory;   a plurality of antennas to communicate with a base station over a downlink channel;   at least one processor configured to:
 transmit channel state information to the base station; 
 receive indices from the base station, the indices being associated with a set of pre-coding coefficients in an angular domain obtained by applying a reversible transform to initial pre-coding coefficients, the initial pre-coding coefficients being independent of the set of pre-coding coefficients; 
 derive a phase reference based at least partially on the indices; and 
 receive data from the base station in accordance with the phase reference. 
   
     
     
         26 . The mobile station of  claim 25 , wherein the channel state information comprises an estimate of a preferred direction of a transmission beam from the base station. 
     
     
         27 . The mobile station of  claim 25 , wherein the at least one processor is further configured to measure a downlink transfer function for each sub-carrier and each transmit antenna of the base station.