Providing ultra-reliable and low-latency transmission is a current issue in wireless communications (URLLC). While it is commonly known that channel coding with large codewords improves reliability, this usually necessitates using interleavers, which incur undesired latency. Using short codewords is a necessary adjustment that will eliminate the requirement for interleaving and reduce decoding latency. This paper suggests a coding and decoding system that, combined with the high spectral efficiency of spatial multiplexing, can provide URLLC over a fading wireless channel. Random linear codes (RLCs) are used over a block-fading massive multiple input-multiple-output (mMIMO) channel followed by zero-forcing (ZF) detection and guessing random additive noise decoding (GRAND). A variation of GRAND, called symbol-level GRAND, originally proposed for single-antenna systems, is generalized to spatial multiplexing. Symbol-level GRAND is much more computationally effective than bit-level GRAND as it takes advantage of the structure of the constellation of the modulation. The paper analyses the performance of symbol-level GRAND depending on the orthogonality defect (OD) of the underlying lattice. Symbol-level GRAND takes advantage of the a priori probability of each error pattern given a received symbol, and specifies the order in which error patterns are tested. The paper further proposes to make use of further side-information that comes from the mMIMO channel-state information (CSI) and its impacts on the reliability of each antenna. This induces an antenna sorting order that further reduces the decoding complexity by over 80 percent when comparing with bit-level GRAND.

翻译：提供超可靠低延迟传输是当前无线通信（URLLC）领域的关键问题。尽管大码字信道编码能提升可靠性，但这通常需要引入交织器，从而产生不可接受的延迟。采用短码字是必要的调整方案，既能消除交织需求，又能降低解码延迟。本文提出一种编码与解码系统，结合空间复用的高频谱效率，可在衰落无线信道上实现URLLC。在块衰落大规模多输入多输出（mMIMO）信道中，采用随机线性码（RLC）后接迫零（ZF）检测与猜测随机加性噪声解码（GRAND）。我们将其一种变体——最初为单天线系统提出的符号级GRAND——推广至空间复用场景。符号级GRAND利用调制星座图结构，其计算效率远优于比特级GRAND。本文分析了符号级GRAND在不同晶格正交性缺陷（OD）下的性能表现。符号级GRAND利用给定接收符号时各错误模式的先验概率，指定错误模式的测试顺序。进一步地，本文提出利用mMIMO信道状态信息（CSI）及其对每根天线可靠性的影响作为额外辅助信息，由此推导出天线排序准则。与比特级GRAND相比，该排序可将解码复杂度降低80%以上。