Secrecy Enhancement of Dual-Hop Cooperative Relay System Using Signal Space Diversity

In this paper, signal space diversity (SSD) is proposed to integrate into a dual-hop cooperative relay system to enhance its secrecy performance. A complete investigation on secrecy performance of the cooperative system with a decode- and-forward (DF) relay using SSD over Rayleigh fading channels is carried out in this paper. Due to SSD, both source and intermediate relay cooperate to transmit two different symbols to the destination, thus its mutual information and secrecy capacity is higher than the conventional dual-hop cooperative relay system. Therefore, secrecy analysis of SSD-based cooperative relay system is completely different than conventional dual-hop cooperative relay system. Moreover, secrecy outage probability of the SSD-based cooperative system is compared with the conventional dual-hop cooperative system and it is confirmed that SSD-based cooperative system outperforms the conventional cooperative system. In this paper, the closed-form expressions for the secrecy outage probability, and intercept probability of the SSD-based cooperative system are derived and validated through Monte Carlo simulations. Furthermore, the impact of imperfect channel estimation on the secrecy performance of the SSD-based cooperative relay system is investigated.