Using delayed feedback for antenna selection in MIMO systems

Antenna selection in multiple-input-multipleoutput (MIMO) systems preserves diversity gain while significantly reducing hardware complexity. However, imperfect channel state information (CSI) affects performance. In this paper, we first analyze the performance of a MIMO system employing antenna selection at the transmitter and maximal ratio combining (MRC) at the receiver in the presence of feedback delay and channel estimation errors. Then, we determine whether channel prediction can compensate for the effect of feedback delay. Outage probability is analyzed as a function of ¿, the correlation coefficient between the CSI used at the receiver for decoding (CSIR) and the CSI used at the transmitter for selection (CSIT). Analytical results show that the effect of feedback delay is more significant than the effect of estimation error. In order to overcome the effect of delay, ¿ should increase with SNR. For a given SNR, the length of the linear minimum mean square error (LMMSE) prediction filter required is calculated and shown to increase with SNR. Finally, we determine the asymptotic diversity order as a function of the feedback quality. Results show that if 1 - ¿ ¿ SNR^-1, the diversity order with imperfect CSI is same as that with perfect CSI.