Gaussian and Fading Multiple Access Using Linear Physical-Layer Network Coding

• Published in: IEEE transactions on wireless communications Vol. 22; no. 5; pp. 3099 - 3113
• Main Authors: Chen, Qiuzhuo, Yu, Fangtao, Yang, Tao, Liu, Rongke
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.05.2023; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: coded modulation; Codes; Coding; compute-forward; Decoding; Domains; Fading; Fading channels; Information transfer; Iterative decoding; Iterative methods; Matrices (mathematics); Messages; Modulation; multiple access; Network coding; NOMA; Nonorthogonal multiple access; Optimization; physical-layer network coding; Pulse amplitude modulation; Receivers; successive interference cancellation
• ISSN: 1536-1276; 1558-2248
• DOI: 10.1109/TWC.2022.3216002

This paper concerns with efficient communication over Gaussian and fading multiple-access channels (MACs). Existing orthogonal multiple-access (OMA) and power-domain nonorthogonal-OMA (NOMA) cannot achieve all rate-tuples in the MAC capacity region. Meanwhile, code-domain NOMA schemes usually require big-loop receiver-iterations for multi-user decoding, which is subject to high implementation cost and latency. This paper studies a linear physical-layer network coding multiple access (LPNC-MA) scheme that is capable of achieving any rate-tuples in the MAC capacity region without receiver iterations. For deterministic Gaussian MACs with <inline-formula> <tex-math notation="LaTeX">M </tex-math></inline-formula> users, we propose to utilize <inline-formula> <tex-math notation="LaTeX">q </tex-math></inline-formula>-ary irregular repeat accumulate (IRA) codes over finite integer fields/rings and <inline-formula> <tex-math notation="LaTeX">q </tex-math></inline-formula>-ary pulse amplitude modulation (<inline-formula> <tex-math notation="LaTeX">q </tex-math></inline-formula>-PAM) as the underlying coded-modulation. The receiver sequentially computes <inline-formula> <tex-math notation="LaTeX">M </tex-math></inline-formula> network coded (NC) messages of the <inline-formula> <tex-math notation="LaTeX">M </tex-math></inline-formula> users. All users' messages are then recovered by solving the computed <inline-formula> <tex-math notation="LaTeX">M </tex-math></inline-formula> NC messages via the inverse of the NC coefficient matrix. A joint nested code construction and extrinsic information transfer (EXIT) chart based code optimization method is developed, yielding near-capacity performance (within 0.7 and 1.1 dB the capacity limits for two and three users respectively). For fading MAC, we study the symmetric rate of LPNC-MA, and propose a pragmatic method for identifying the mutual information (MI) maximizing network coding coefficient matrix. Numerical results demonstrate that the frame error rate (FER) of the optimized LPNC-MA is within a fraction of dB the outage probability of fading MAC capacity. LPNC-MA remarkably outperforms NOMA-SIC and IDMA while avoiding the big-loop receiver iteration.