Spatially coupled LDPC coding in cooperative wireless networks

Dushantha Nalin K. Jayakody, Vitaly Skachek, Bin Chen
2016 EURASIP Journal on Advances in Signal Processing  
This paper proposes a novel technique of spatially coupled low-density parity-check (SC-LDPC) code-based soft forwarding relaying scheme for a two-way relay system. We introduce an array-based optimized SC-LDPC codes in relay channels. A more precise model is proposed to characterize the residual noise on the soft symbols, using a pre-calculated look-up table at the destination. This requires less signaling overhead compared to previous soft noise modeling techniques. We also introduce a
more » ... e correction factor to provide a rectification to the equivalent total noise variance at the destination. Finally, we propose an appropriate log likelihood ratio (LLR) former at the destination which is tailored to the proposed soft parity generation technique. Simulation results demonstrate that the proposed relay protocol yields an improved bit error rate (BER) performance compared to competing schemes proposed in the literature. Full list of author information is available at the end of the article forwarding technique based on symbol-wise mutual information (SMI) was investigated in [4] using physical layer network coding (PLNC) in the two-way relay channel. Recently, a soft decode-compress-forward scheme was proposed in [5] ; that work featured a new model, referred to as the soft scalar model, in order to facilitate the log likelihood ratio (LLR) computation at the destination. In [6], the authors suggested a "soft fading" model for the overall channel, experienced by a BPSK symbol, when transmitted from the source to relay to the destination. That idea was extended to soft two-step re-encoding together with per-scaling at the relay in [7] . In order to decode the SIR signals, the destination uses an independent Gaussian approximation, which models the residual noise in the estimated symbols as in [3, 5] . Error-correcting code is a pivotal ingredient of the DF cooperative relay system. The right choice of the code can greatly improve the performance. Low-density paritycheck (LDPC) codes, which became extremely popular in point-to-point communications due to their excellent performance, are a natural candidate for use in such systems. It was observed in [12] that the so-called "convolutional LDPC codes" outperform classical LDPC block codes. Recently, it has been shown that regular spatially coupled low-density parity-check (SC-LDPC) achieve capacity of
doi:10.1186/s13634-016-0311-9 fatcat:ip3w775rhnb2tevn4xmj4kaeai