2019/11/26 by Hossein Asgharimoghaddam, Asgharimoghaddam, Hossein, Jarkko Kaleva +3
Engineering · #Advanced Wireless Communication Techniques #Advanced Wireless Communication Technologies #FOS: Electrical engineering #Signal Processing (eess.SP) #eess.SP #electronic engineering #graph theory and CDMA systems #information engineering
paper · pdf · doi:10.48550/arxiv.1911.11540
29 Pages, New references are added. Section III and IV are revised for better presentation, the final results unchanged. Additional numerical results are included
openalex publication_date 2019/11/26 · arxiv created 2020/06/23 · arxiv updated 2020/06/24 · openalex created_date 2022/07/26 · openalex updated_date 2026/07/28
Low-density spreading non-orthogonal multiple-access (LDS-NOMA) is considered where K single-antenna user-equipments (UEs) communicate with a base-station (BS) over F fading sub-carriers. Each UE k spreads its data symbols over dk<F sub-carriers. We aim to identify the LDS-code allocations that maximize the ergodic mutual information (EMI). The BS assigns resources solely based on pathlosses. Conducting analysis in the regime where F, K, and dk,∀ k converge to +∞ at the same rate, we present EMI as a deterministic equivalent plus a residual term. The deterministic equivalent is a function of pathlosses and spreading codes, and the small residual term scales as O((1)/(min(dk2))). We formulate an optimization problem to get the set of all spreading codes, irrespective of sparsity constraints, which maximize the deterministic EMI. This yields a simple resource allocation rule that facilitates the construction of desired LDS-codes via an efficient partitioning algorithm. The acquired LDS-codes additionally harness the small incremental gain inherent in the residual term, and thus, attain near-optimal values of EMI in the finite regime. While regular LDS-NOMA is found to be asymptotically optimal in symmetric models, an irregular spreading arises in generic asymmetric cases. The spectral efficiency enhancement relative to regular and random spreading is validated numerically.