On information‐theoretic limits of code‐domain NOMA for 5G. Issue 15 (13th August 2018)

• Record Type: Journal Article
• Authors: Le, Mai T. P.; Ferrante, Guido Carlo; Caso, Giuseppe; De Nardis, Luca; Di Benedetto, Maria‐Gabriella
• Is Part Of: IET communications. Volume 12:Issue 15(2018)
• Page Start: 1864
• Page End: 1871
• Publication Date: 2018-08-13
• Subjects: 5G mobile communication -- multi‐access systems -- information theory -- matrix algebra; information‐theoretic limits -- code‐domain NOMA schemes -- 5G -- code‐domain nonorthogonal multiple access -- NOMA spreading matrix -- load feature -- sparsity feature -- regularity feature -- extreme low‐dense code‐domain NOMA -- number‐of‐resource elements -- regular low‐dense spreading matrix -- system achievable rates -- regular low‐dense NOMA; Telecommunication systems -- Periodicals; Speech processing systems -- Periodicals; 621.38205
• DOI: 10.1049/iet-com.2018.5241
• Languages: English
• ISSNs: 1751-8628

Abstract

Abstract : Motivated by recent theoretical challenges for 5G, this study aims to position relevant results in the literature on code‐domain non‐orthogonal multiple access (NOMA) from an information‐theoretic perspective, given that most of the recent intuition of NOMA relies on another domain, that is, the power domain. Theoretical derivations for several code‐domain NOMA schemes are reported and interpreted, adopting a unified framework that focuses on the analysis of the NOMA spreading matrix, in terms of load, sparsity, and regularity features. The comparative analysis shows that it is beneficial to adopt extreme low‐dense code‐domain NOMA in the large system limit, where the number of resource elements and number of users grow unboundedly while their ratio, called load, is kept constant. Particularly, when optimum receivers are used, the adoption of a regular low‐dense spreading matrix is beneficial to the system achievable rates, which are higher than those obtained with either irregular low‐dense or dense formats, for any value of load. For linear receivers, which are more favourable in practice due to lower complexity, the regular low‐dense NOMA still has better performance in the underloaded regime (load < 1 ), while the irregular counterpart outperforms all the other schemes in the overloaded scenario (load > 1 ).