Methods for opportunistic multi-user beamforming in collaborative MIMO-SDMA

摘要

A system and method for opportunistically designing collaborative beamforming vectors is disclosed for a wireless multiple input, multiple output (MIMO) space division multiple access (SDMA) communication system by sequentially designing beamforming vectors for ranked channels in order to exploit the instantaneous channel conditions to improve per user average SNR performance. Each subscriber station independently transmits information to a base station that allows the base station to determine beamforming vectors for each subscriber station by ranking the subscriber stations by channel strength. Using sequential nullspace methods, the ranked channel matrices are then used to select the channel matrix Hi for the best subscriber station, to design the wi, vi for the best subscriber station as the left and right singular vectors of the MIMO channel matrix Hi, to transform the remaining channels and to continue the process until beamforming vectors are designed for all channels.

主权项

1. A method for designing beamforming vectors for a collaborative space division multiple access system, comprising:
for each one of a plurality of subscriber stations, determining, by a processor, an array of channel conditions; wherein each one of the plurality of determined arrays comprises a representation of a plurality of channel gains corresponding to one or more transmit antennas and one or more receive antennas; ranking the plurality of determined arrays according to at least a first criterion; and designing a beamforming vector comprising a weighting vector and a combining vector for each subscriber station based at least in part on the ranking and on a nullspace of one or more previously designed weighting vectors and combining vectors of corresponding beamforming vectors; wherein, for each one of the plurality of determined arrays, the representation of the plurality of channel gains comprises a channel matrix H, wherein the first criterion is based at least in part on a maximal eigenvalue of the channel matrix H; wherein each beamforming vector for each subscriber station is determined sequentially according to rank.