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DF Relay-Aided NOMA Framework for Low Outage
  • Anand Jee ,
  • KAMAL AGRAWAL ,
  • Shankar Prakriya
Anand Jee
Indian Institute of Technology Delhi, Indian Institute of Technology Delhi

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KAMAL AGRAWAL
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Shankar Prakriya
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Abstract

This paper investigates the performance of a framework for low-outage downlink non-orthogonal multiple access (NOMA) signalling using a coordinated direct and relay transmission (CDRT) scheme with direct links to both the near-user (NU) and the far-user (FU). Both amplify-and-forward (AF) and decode-and-forward (DF) relaying are considered. In this framework, NU and FU combine the signals from BS and R to attain good outage performance and harness a diversity of two without any need for feedback. For the NU, this serves as an incentive to participate in NOMA signalling. For both NU and FU, expressions for outage probability and throughput are derived in closed form. High-SNR approximations to the outage probability are also presented. We demonstrate that the choice of power allocation coefficient and target rate is crucial to maximize the NU performance while ensuring a desired FU performance. We demonstrate performance gain of the proposed scheme over selective decode-and-forward (SDF) CDRT-NOMA in terms of three metrics: outage probability, sum throughput and energy efficiency. Further, we demonstrate that by choosing the target rate intelligently, the proposed CDRT NOMA scheme ensures higher energy efficiency (EE) in comparison to its orthogonal multiple access counterpart. Monte Carlo simulations validate the derived expressions.
Mar 2022Published in IEEE Transactions on Communications volume 70 issue 3 on pages 1559-1579. 10.1109/TCOMM.2021.3126632