URLLC with Coded Massive MIMO via Random Linear Codes and GRAND

A present challenge in wireless communications is the assurance of ultra-reliable and low-latency communication (URLLC). While the reliability aspect is well known to be improved by channel coding with long codewords, this usually implies using interleavers, which introduce undesirable delay. Using short codewords is a needed change, which will also do away with the need for interleaving and minimize the decoding delay. This work proposes a coding and decoding scheme that, in combination with the high spectral efficiency attained by spatial signal processing, can provide URLLC over a fading wireless channel. The paper advocates the use of random linear codes (RLCs) over a massive MIMO channel with standard zero-forcing detection and guessing random additive noise decoding (GRAND). The performance of several schemes is assessed over a MIMO flat fading channel. The proposed scheme greatly outperforms the equivalent scheme using standard polar encoding and decoding for signal-to-noise ratios (SNR) of interest. The decoding complexity of the proposed setup is assessed and compared with the equivalent counterpart using the polar code in the 5G NR (new radio) standard. While the complexity of the polar code is constant at all SNRs, using RLCs with GRAND achieves much faster decoding times for most of the SNR range, further reducing latency.