Energy Efficiency Maximization for Hybrid TDMA-NOMA System With Opportunistic Time Assignment

Xinchen Wei, Haitham Al-Obiedollah, Kanapathippillai Cumanan, Zhiguo Ding, Octavia A. Dobre

Research output: Contribution to journalArticlepeer-review

20 Scopus citations

Abstract

In this paper, we consider an energy efficient resource allocation technique for a hybrid time division multiple access (TDMA) - non-orthogonal multiple access (NOMA) system. In such a hybrid system, the available time for transmission is divided into several sub-time slots, and a sub-time slot is allocated to serve a group of users (i.e., cluster). Furthermore, signals for the users in each cluster are transmitted based on the NOMA approach. With NOMA, multiple users can be served simultaneously through utilizing power domain multiplexing at transmitter and successive interference cancellation (SIC) at receiver. In this paper, to maximize the energy efficiency (EE), we jointly allocate both the available time slots and the available transmit power in the hybrid TDMA-NOMA system. In particular, we formulate an EE maximization (EE-Max) problem aiming to maximize the overall EE of the system with a per-user minimum rate and transmit power constraints. However, this joint optimization problem is non-convex in nature, and thus, cannot be solved directly. Therefore, we develop an iterative algorithm by approximating the original problem into a convex one with sequential convex approximation (SCA) and a novel second-order cone (SOC) approach. Simulation results demonstrate that the performance of the proposed hybrid TDMA-NOMA system with joint resource allocation outperforms the system with equal time allocation in terms of the overall EE. Simulation results further confirm that the proposed iterative approaches with SCA and SOC techniques converge within a few number of iterations while yielding the solution to the original non-convex problem.

Original languageBritish English
Pages (from-to)8561-8573
Number of pages13
JournalIEEE Transactions on Vehicular Technology
Volume71
Issue number8
DOIs
StatePublished - 1 Aug 2022

Keywords

  • Convex optimization
  • energy efficiency
  • hybrid TDMA-NOMA
  • non-orthogonal multiple access (NOMA)
  • time division multiple access (TDMA)

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