On the Secrecy Rate of Downlink NOMA in Underlay Spectrum Sharing with Imperfect CSI

Abstract

<div>In this paper, we present the ergodic sum secrecy rate (ESSR) analysis of an underlay spectrum sharing non-orthogonal multiple access (NOMA) system. We consider the scenario where the power transmitted by the secondary transmitter (ST) is constrained by the peak tolerable interference at multiple primary receivers (PRs) as well as the maximum transmit power of the ST. The effect of channel estimation error is also taken into account in our analysis. We derive exact and asymptotic closed-form expressions for the ESSR of the downlink NOMA system, and show that the performance can be classified into two distinct regimes, i.e., it is dictated either by the interference constraint or by the power constraint. Our results confirm the superiority of the NOMA-based system over its orthogonal multiple access (OMA) based counterpart. More interestingly, our results show that NOMA helps in maintaining the secrecy rate of the strong user while significantly enhancing the secrecy performance of the weak user as compared to OMA. The correctness of the proposed investigation is corroborated through Monte Carlo simulation.</div>

Achievable Rate Maximization for Underlay Spectrum Sharing MIMO System With Intelligent Reflecting Surface

“…Following the arguments in the related works of[6],[7],[9],[11],[12], we assume that the secondary network is deployed outside the coverage of the primary transmitter, and that the distance between the primary transmitter and secondary receiver is large enough for the primary-to-secondary interference to be negligible. However, it is noteworthy that the proposed PDDGP algorithm is also applicable when the secondary network is deployed completely or partially inside the coverage of the primary transmitter.…”