Impact of User Pairing on 5G Nonorthogonal Multiple-Access Downlink Transmissions

Zhiguo Ding, Pingzhi Fan, H. Vincent Poor

Research output: Contribution to journalArticlepeer-review

1254 Scopus citations


Nonorthogonal multiple access (NOMA) represents a paradigm shift from conventional orthogonal multiple-access (MA) concepts and has been recognized as one of the key enabling technologies for fifth-generation mobile networks. In this paper, the impact of user pairing on the performance of two NOMA systems, i.e., NOMA with fixed power allocation (F-NOMA) and cognitive-radio-inspired NOMA (CR-NOMA), is characterized. For F-NOMA, both analytical and numerical results are provided to demonstrate that F-NOMA can offer a larger sum rate than orthogonal MA, and the performance gain of F-NOMA over conventional MA can be further enlarged by selecting users whose channel conditions are more distinctive. For CR-NOMA, the quality of service (QoS) for users with poorer channel conditions can be guaranteed since the transmit power allocated to other users is constrained following the concept of cognitive radio networks. Because of this constraint, CR-NOMA exhibits a different behavior compared with F-NOMA. For example, for the user with the best channel condition, CR-NOMA prefers to pair it with the user with the second best channel condition, whereas the user with the worst channel condition is preferred by F-NOMA.

Original languageEnglish (US)
Article number7273963
Pages (from-to)6010-6023
Number of pages14
JournalIEEE Transactions on Vehicular Technology
Issue number8
StatePublished - Aug 2016

All Science Journal Classification (ASJC) codes

  • Aerospace Engineering
  • Electrical and Electronic Engineering
  • Computer Networks and Communications
  • Automotive Engineering


  • Cognitive radio
  • nonorthogonal multiple access (NOMA)
  • power allocation
  • user pairing and outage probability


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