Nonbinary low density parity check coded faster-than-Nyquist signaling system for short packet communications

Newer generations of communication systems aim to improve transmission in terms of performance and complexity. Ultra-reliable low-latency communication (URLLC) supports newer generations with the requirement of low processing time and short packets. Short packet transmission provides a better latency, in return for decreased channel coding rate and a performance decay in a communication system. In this study, the loss of channel coding rate is compensated with faster-than-Nyquist (FTN) signaling, which uses nonorthogonal pulse shapes for a faster transmission beyond Nyquist criterion in return for introduction of intersymbol interference (ISI) at the received symbols. At the receiver, a low complexity FTN detector, namely, symbol-by-symbol with go-back-K sequence estimator (SSSgbKSE), is used to satisfy the URLLC requirement of latency. Short block length requirement is supported by nonbinary low density parity check (NB-LDPC) channel codes, which have been known to have better performance on short packets of data than binary counterparts. Simulation results revealed that NB-LDPC codes with SSSgbKSE yielded performance improvements than conventional systems, which are based on the combination of low density parity check (LDPC) codes with M-algorithm Bahl, Cocke, Jelinek and Raviv (M-BCJR) detection, for low signal-to-noise ratio (SNR) cases for 128-bit block length. Simulations for 256- and 512-bit block lengths revealed that higher lengths yielded better performances favoring the proposed scheme. However, simulations for transmissions with an acceleration factor of τ=0.7 favored conventional schemes. Furthermore, complexity evaluations for τ=0.8 revealed that proposed structure has 3 to 5 times less complexity than conventional structure.