Lattice-Code Multiple Access: Architecture and Efficient Algorithms
Tao Yang, Fangtao Yu, Rongke Liu, Shanxiang Lyu, John Thompson · IEEE Transactions on Vehicular Technology · 2025
This paper proposes a lattice-code multiple-access (LCMA) scheme for$K$-user uplink systems. Each user encodes messages via$2^{m}$-ary lattice codes mapped to$2^{m}$-PAM. The receiver employs integer coefficients to computeinteger linear combinations(ILCs) of messages, then reconstructs original data through novel low-complexitysoft detectionand single-user decoders. Key contributions include: 1) A soft detector calculating a posteriori probabilities of ILCs over lattices, enabling efficient belief-propagation decoding; 2) Abounded independent vectors problem(BIVP) framework to optimize ILC coefficients, solved by arate-constrained sphere decoderoutperforming traditional lattice reduction methods; 3) Optimized signature sequences designed via a targetswitching steepest descent algorithm. Simulations demonstrate LCMA's superiority over IDMA and SCMA in supporting higher user loads and achieving lower error rates, while avoiding successive interference cancellation or iterative detection.