LDPC-Coded HARQ Throughput Performance of MC-CDMA Using ICI Cancellation

Abstract

Broadband packet data services are demanded in the next generation mobile communications systems. Multi-carrier CDMA (MC-CDMA) is considered to be a promising wireless technique. Hybrid ARQ (HARQ) is a powerful error control technique. It is known that the HARQ throughput performance of MC-CDMA degrades due to the residual inter-code interference (ICI) after frequency-domain equalization (FDE). The use of frequency-domain soft interference cancellation FDSIQ technique can reduce the residual ICI and improve the throughput performance. An important technical problem is the generation of accurate residual ICI replica for FDSIC. In this paper, we consider low-density parity-check coded (LDPC- coded) MC-CDMA HARQ and generate the residual ICI replica from a-posteriori log-likelihood ratio (LLR) obtained by the LDPC decoder. We evaluate, by computer simulation, the throughput performance in a frequency-selective Rayleigh fading channel. We show that if the residual ICI is removed MC- CDMA can provide better throughput performance than orthogonal frequency division multiplexing (OFDM).