Performance of decode and forward MIMO relaying for wireless uplink

In this paper, performance of relay assisted wireless link is evaluated in the presence of rayleigh fading where mobile handset is equipped with single transmit antenna, relay is equipped with multiple transmit and receive antennas, and destination has multiple receive antennas. Data are modulated using QPSK or 16 QAM or 64 QAM modulator at handset and send to relay which combined and decode the incoming signal using Maximum Likelihood decoding and further encode the symbols using STBC, and the encoded data are split into n streams which are simultaneously transmitted using n transmit antennas of relay. It is observed that relay with 2 transmit antennas and 2,3,4,5 and 6 receive antennas provides 13 dB, 11 dB, 9 dB, 6 dB and 5 dB gains respectively compared to direct link at 10^-5. And there are around 1.5 dB to 6 dB gains for increasing number of receiving antennas of relay from 2 to 3 or 3 to 4 but there are very little gains for increasing number of receiving antennas of relay from 4 to 5 or 5 to 6.