Security-Reliability Trade-off Analysis for D-SSMR-CT Systems with Two Combining Schemes in Wireless Communication

This study investigates a direct single-source multi-relay cooperative transmission (D-SSMR-CT) system with an eavesdropper to address the security and reliability challenges in communication system. To begin with, the reliability and security of the system using maximum ratio combining (MRC) and selective combining (SC) methods are analyzed. The system reliability is quantified through outage probability (OP), while security is evaluated via intercept probability (IP). Closed-form expressions for OP and IP under MRC and SC are derived, respectively. Subsequently, the main-to-eavesdropper ratio (MER) is employed to analyze the security-reliability trade-off (SRT) for achieving diversity gain. Numerical results demonstrate that the proposed MRC-based cooperative scheme with direct link outperforms both the SC-based scheme with direct link and traditional non-direct-link transmission in terms of SRT. Furthermore, the SRT of the proposed scheme improves significantly as the number of relays increases, indicating that cooperative transmission between the source node and relay nodes effectively enhances the security and reliability of wireless communication systems.