Fundamental limits of low-density spreading NOMA with fading

Mai T.P. Le, Guido Carlo Ferrante, Tony Q.S. Quek, Maria Gabriella Di Benedetto

Research output: Contribution to journalArticlepeer-review

20 Citations (Scopus)


Spectral efficiency of low-density spreading non-orthogonal multiple access channels in the presence of fading is derived for linear detection with independent decoding and optimum decoding. The large system limit, where both the number of users and number of signal dimensions grow with fixed ratio, called load, is considered. In the case of optimum decoding, it is found that low-density spreading underperforms dense spreading for all loads. Conversely, linear detection is characterized by different behaviors in the underloaded versus overloaded regimes. In particular, it is shown that spectral efficiency changes smoothly as load increases. However, in the overloaded regime, the spectral efficiency of low-density spreading is higher than that of dense spreading.

Original languageEnglish
Pages (from-to)4648-4659
Number of pages12
JournalIEEE Transactions on Wireless Communications
Issue number7
Publication statusPublished - 2018 Jul

All Science Journal Classification (ASJC) codes

  • Computer Science Applications
  • Electrical and Electronic Engineering
  • Applied Mathematics


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