The Coding-Spreading Trade-off in LDPC-Coded Interleave-Division Multiple-Access (IDMA) System

In this paper capacity-achieving low-density parity-check (LDPC) codes is applied to IDMA System, called as, LDPC-Coded IDMA system, in which the associated coding- spreading tradeoff problem is mainly investigated. We quest the required minimum SNR for reliable data and voice transmission based on the bit error rate (BER) level of 10" and 10"3 over AWGN channel under different code rates to explore the coding-spreading tradeoff. Simulation results show that the optimal LDPC code rates in LDPC-coded IDMA system are middle rates between 0.4 and 0.5 for relevant communication services over AWGN channel. Finally comparing with traditional convolutional-coded IDMA system at 0.5 code rate, the performance advantage of the proposed system is greatly obvious.