Hybrid Half-Duplex/Full-Duplex Cooperative Non-Orthogonal Multiple Access with Transmit Power Adaptation

Gang Liu, Xianhao Chen, Zhiguo Ding, Zheng Ma, F. Richard Yu

Research output: Contribution to journalArticlepeer-review

107 Scopus citations

Abstract

Power allocation is an important issue in order to optimize the performance of non-orthogonal multiple access (NOMA) systems. However, the power allocation problem for cooperative NOMA systems has not been well investigated. In this paper, we investigate the power allocation problems for half-duplex cooperative NOMA (HD-CNOMA) and full-duplex cooperative NOMA (FD-CNOMA) systems, respectively. From the fairness standpoint, the optimization problem for each system is formulated to maximize the minimum achievable user rate in a NOMA user pair. Even though both of the formulated problems are neither concave nor quasi-concave, the optimal closed-form solutions of both cases are still obtained with the proposed two-step method. First, we transform the initial problem into a quasi-concave problem by treating the relay transmit power, namely P R, as a constant, and then solve the obtained quasi-concave problem. Second, we convert the original problem into a univariate problem of PR based on the results of the first step, and eventually obtain the optimal power allocation. In addition, a hybrid half/full-duplex cooperative NOMA scheme, which dynamically switches between the HD-CNOMA and FD-CNOMA mode, is proposed. After that, a relay selection scheme is also investigated to extend the hybrid scheme into general networks with multiple users. Numerical results demonstrate that the proposed hybrid relaying scheme can achieve a significant performance improvement with respect to the conventional NOMA, HD-CNOMA, and FD-CNOMA scheme.

Original languageBritish English
Article number8094966
Pages (from-to)506-519
Number of pages14
JournalIEEE Transactions on Wireless Communications
Volume17
Issue number1
DOIs
StatePublished - Jan 2018

Keywords

  • 5G
  • cooperative NOMA
  • full-duplex relaying
  • half-duplex relaying
  • power allocation

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