Comparison of RCPT HARQ throughput using OFDM, MC-CDMA and DS-CDMA with frequency-domain equalization

OFDM, MC-CDMA and DS-CDMA are being researched vigorously as the prospective signaling technique for the next generation mobile communications systems, which will be characterized by the broadband packet technology. With packet transmission, hybrid ARQ (HARQ) will be inevitable for error control. HARQ with rate compatible punctured turbo (RCPT) codes is one of the promising techniques. Data rate equivalent to OFDM can be attained with MC-CDMA and DS-CDMA by assigning all the available orthogonal codes to the same user, resulting in what is commonly referred to as multicode MC-CDMA and multicode DS-CDMA. In this paper, we introduce RCPT HARQ to DS-CDMA with minimum mean square error frequency-domain equalization (MMSE-FDE) and compare its throughput performance with OFDM, multicode MC-CDMA and multicode DS-CDMA with rake combining. It is found that the throughput of DS-CDMA with MMSE-FDE is the same as or better than that of MC-CDMA. However, with higher level modulation, coded OFDM is better than either MC-CDMA or DS-CDMA.