Effect of joint modulation and coding scheme selection on turbo SIC for OFDM-MIMO multiplexing

This paper presents the effect of joint modulation and coding scheme (MCS) selection on a turbo soft interference canceller (SIC) for OFDM-MIMO multiplexing using adaptive modulation and coding (AMC). We use a turbo SIC to detect signals by performing iterative interference cancellation using soft-symbol estimates based on the a posteriori log-likelihood ratio (LLR) at the Max-Log-MAP decoder output and linear minimum mean-square error (LMMSE)-based signal detection. Joint MCS section selects the best MCS combinations of all transmission streams so that the total throughput is maximized considering the residual interference from other streams for the turbo SIC. Computer simulations show that the joint MCS selection mitigates the decrease in throughput due to the large difference in the peak data rate between consecutive MCSs compared to independent MCS selection. Hence, we show that by using joint MCS selection, the total throughput with the number of MCSs of N_MCS = 8 becomes almost identical to that for N_MCS = 12 for 4-by-4 MIMO multiplexing using the turbo SIC.