Improving Physical Layer Security of Two-Way Cooperative DF System using Modulation Diversity

Abstract

This paper investigates the physical layer security of a two-way cooperative relay system, where two sources communicate with each other directly as well as via an intermediate decode-and-forward (DF) relay. This paper proposes to incorporate modulation diversity into the two-way cooperative relay system to improve its secrecy performance. In this paper, the physical layer security of the two-way cooperative relay system with modulation diversity is explored in detail over Rayleigh fading channels using mathematical analysis and computer simulations. When the modulation diversity is integrated into two sources and the intermediate DF relay, both source and relay cooperatively transmit different symbols, thus increasing the spectral efficiency of the system by exchanging four symbols in three time slots compared to the conventional two-way cooperative relay system which exchanges two symbols in three time slots. Hence, the mutual information of the proposed system is higher than the conventional system that makes the analysis of the proposed system is entirely different than the conventional system. This paper presents the mathematical analysis for the secrecy outage probability, the probability of non-zero secrecy capacity, and the intercept probability of the proposed system. Moreover, it carries out comprehensive computer simulations to validate the mathematical framework. Finally, the results confirm the significant improvement of the two-way cooperative relay system's secrecy performance by incorporating the proposed scheme compared to the conventional system.