Transmit Selection Diversity for

Multiuser Spatial Multiplexing Systems


Runhua Chen, Jeffrey G. Andrews, and Robert W. Heath Jr.


in Proc. IEEE Global Telecommunications Conference, Dallas, Texas, Nov. 29th - Dec. 3rd, 2004.


Multiuser spatial multiplexing uses precoding to support multiple users in multi-antenna wireless channels. In this paper, two transmit diversity techniques are proposed that use extra transmit antennas to obtain addition diversity. In one solution, an eigenmode selection technique is proposed to achieve higher diversity gain by optimally matching the data streams to eigenmodes with superior channel conditions. In the other solution, a multiuser antenna selection algorithm is proposed that achieves good performance with fewer RF chains and lower system cost. Selection criteria for single-user spatial multiplexing are extended to the multiuser scenario in the context of unitary downlink precoding, and a novel selection algorithm that is near optimal in terms of symbol error rate (SER) is proposed. Simulation results show dramatic SNR reductions of 6-10 dB at an uncoded SER of $10^{-3}$ with only one extra antenna.

This paper is available as a .IEEE Xplore .