Beamforming techniques for nonorthogonal multiple access in 5G cellular networks

Faezeh Alavi, Kanapathippillai Cumanan, Zhiguo Ding, Alister G. Burr

Research output: Contribution to journalArticlepeer-review

60 Scopus citations


In this paper, we develop various beamforming techniques for downlink transmission for multiple-input single-output nonorthogonal multiple access (NOMA) systems. First, a beamforming approach with perfect channel state information is investigated to provide the required quality of service for all users. Taylor series approximation and semidefinite relaxation (SDR) techniques are employed to reformulate the original nonconvex power minimization problem to a tractable one. Furthermore, a fairness-based beamforming approach is proposed through a max-min formulation to maintain fairness between users. Next, we consider a robust scheme by incorporating channel uncertainties, where the transmit power is minimized while satisfying the outage probability requirement at each user. Through exploiting the SDR approach, the original nonconvex problem is reformulated in a linear matrix inequality form to obtain the optimal solution. Numerical results demonstrate that the robust scheme can achieve better performance compared to the nonrobust scheme in terms of the rate satisfaction ratio. Furthermore, simulation results confirm that NOMA consumes a little over half transmit power needed by orthogonal multiple access for the same data rate requirements. Hence, NOMA has the potential to significantly improve the system performance in terms of transmit power consumption in future 5G networks and beyond.

Original languageBritish English
Article number8411153
Pages (from-to)9474-9487
Number of pages14
JournalIEEE Transactions on Vehicular Technology
Issue number10
StatePublished - Oct 2018


  • max-min fairness
  • Non-orthogonal multiple access (NOMA)
  • outage probability
  • robust beamforming


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