Doctorate thesis defense of Nesrine Zaghdoud

Doctorate thesis defense on September 23^th 2023 at 09H00 AM ,in Amphitheater Ibn Khaldoun, SUP'COM 2.

Entitled :Study and performance analysis of secure cooperative NOMA communication

Presented by : Nesrine Zaghdoud 

Committee

Abstract

The innovative concept of Non-Orthogonal Multiple Access (NOMA) has recently been considered as a promising technique for the next generation of wireless communication since it ensures significant gains in spectral efficiency, user fairness, and connectivity compared with OMA (Orthogonal Multiple Access) techniques. The main idea of NOMA is to serve multiple users using the same resources with different power levels. In addition, SIC (Successive Interference Cancellation) technique is used to decode their information. NOMA can be utilized in a variety of domains, including cooperative communications using different cooperative protocols such as Amplify-and-Forward (AF) and Decode-and-Forward (DF), which leads to further improvement of the system. However, the performance of NOMA communications can be seriously compromised due to the broadcast nature of the wireless medium, which increases the possibility of eavesdropping attacks. Although, the inherent randomness and impairments of the wireless medium (noisy channels, fading channels, ...) can also be exploited to ensure secure communications using the Physical Layer Security (PLS) approach. For some limited scenarios, PLS was used to secure Cooperative NOMA (C-NOMA) transmissions. However, there are still many challenging scenarios to explore in order to thoroughly investigate the security of the Cooperative NOMA (C-NOMA) system.

In this regard, the main objective of this thesis is to provide an effective study and performance analysis of the security of the C-NOMA system using the PLS approach. First, we analyse how can fading affects the secrecy of HD/FD AF/DF C-NOMA systems. Thus, we use the general fading distribution κ-μ, which includes multiple distributions as special cases like Rayleigh, Rice, and Nakagami-m. Second, we study the impact of NOMA users' ranking on the secrecy performance of the HD AF/DF C-NOMA system, in which we investigate instantaneous and average channel gain for users' ranking. Then, we propose to study the effect of multi-antenna receivers on the secrecy of the HD AF/DF C-NOMA system for two wiretapping scenarios: external and internal eavesdroppers. Next, the effect of multiple relays and eavesdroppers on the secrecy of FD AF C-NOMA was studied for both non-colluding and colluding scenarios. Finally, we extend this work to study the impact of Partial, Best, and Optimal relay selection schemes on the secrecy of the HD/FD AF C-NOMA system in the presence of non-colluding and colluding eavesdroppers.

Keywords

Non-Orthogonal Multiple Access, Cooperative communications, Amplify-and-Forward, Decode-and-Forward, Physical Layer Security, Secrecy Outage Probability, Strictly Positive Secrecy Capacity.