On information-theoretic limits of codedomain NOMA for 5G
Motivated by recent theoretical challenges for 5G, this study aims to position relevant results in the literature on codedomain 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.