Supporting ultra-reliable and low-latency communication (URLLC) is a challenge in current wireless systems. Channel codes that generate large codewords improve reliability but necessitate the use of interleavers, which introduce undesirable latency. Only short codewords can eliminate the requirement for interleaving and reduce decoding latency. This paper suggests a coding and decoding method which, when combined with the high spectral efficiency of spatial multiplexing, can provide URLLC over a fading channel. Random linear coding and high-order modulation are used to transmit information over a massive multiple-input multiple-output (mMIMO) channel, followed by zero-forcing detection and guessing random additive noise decoding (GRAND) at a receiver. A variant of GRAND, called symbol-level GRAND, originally proposed for single-antenna systems that employ high-order modulation schemes, is generalized to spatial multiplexing. The paper studies the impact of the orthogonality defect of the underlying mMIMO lattice on symbol-level GRAND, and proposes to leverage side-information that comes from the mMIMO channel-state information and relates to the reliability of each receive antenna. This induces an antenna sorting step, which further reduces decoding complexity by over 80\% when compared to bit-level GRAND.

翻译：支持超可靠低延迟通信（URLLC）是当前无线系统面临的一项挑战。生成较大码字的信道编码可提升可靠性，但需要引入交织器，从而导致不可接受的延迟。只有短码字才能避免交织需求并降低译码延迟。本文提出了一种编码与译码方法，该方法结合空间复用的高频谱效率，可在衰落信道上实现URLLC。采用随机线性编码与高阶调制，通过大规模多输入多输出（mMIMO）信道传输信息，并在接收端进行迫零检测与猜测随机加性噪声译码（GRAND）。本文还将一种最初为采用高阶调制方案的单天线系统设计的GRAND变体——符号级GRAND——推广至空间复用场景。论文研究了底层mMIMO格的正交缺陷对符号级GRAND的影响，并提出利用源自mMIMO信道状态信息、与各接收天线可靠性相关的边信息。这一方法引入了天线排序步骤，与比特级GRAND相比，可进一步将译码复杂度降低80%以上。