A low complexity iterative multiuser detector for LDPC-coded TDRSS return link MA service

In coded multiuser tracking and data relay satellite system (TDRSS) return link, multiple access interference and inter-symbol interference are major impediment to reliable communication. While the optimal soft-input soft-output multiuser detection scheme results in a prohibitive computational complexity. In this paper, a simplified hard-input soft-output (HISO) scheme for low-density parity-check (LDPC) coded multiuser TDRS system is proposed. The hard decisions of multiuser detection are used as the initial values of the decoding method. After each iteration, the hard output of log-likelihood ratio (LLR) belief propagation (BP) decoding algorithm is fed back as the input of decoding for the next iteration. Furthermore, interleaving is not a necessary part in the proposed method. The computational complexity is much lower than the optimal algorithm. However, simulation results show that the performance of the proposed scheme approaches that of the single-user system for moderate to high signal-to-noise ratios (SNRs).