Comparative Study of SC-FDMA and OFDMA Using Turbo SIC Considering Soft-Symbol Estimate for MIMO SDM

This paper presents a comparative study of single-carrier (SC)-frequency division multiple access (FDMA) and OFDMA using turbo soft interference cancellation (SIC) from the viewpoint of throughput for multiple-input multiple-output (MIMO) spatial division multiplexing (SDM). In turbo SIC, interference from other transmission streams is generated based on the log-likelihood ratio (LLR) at the turbo decoder output and subtracted from the received signal iteratively associated with a linear minimum mean-square error (LMMSE) filter. Hence, we compare the throughput performance levels of methods for generating soft-symbol estimates of other streams based on the extrinsic LLR and the a posteriori LLR at the Max-Log-MAP decoder output. We show by computer simulation the difference in performance of turbo SIC based on the a posteriori LLR and extrinsic LLR from the viewpoints of the average block error rate and throughput. We also show that the OFDMA yields superior throughput performance compared to SC-FDMA with 16QAM and 64QAM schemes when using turbo SIC for 2-by-2 to 8-by-8 MIMO SDM.