Secrecy Performance of Diversity Scheme Using Generalized Selection Combining in Dual-Hop AF-Relay Systems

This paper presents the secrecy performance analysis of a hybrid combining scheme using antenna and relay selection for dual-hop amplify-forward (AF)-relay systems. In the source and relay link, the hybrid scheme uses feedback information to select a transmit antenna of the source node and a generalized selection combining (GSC)-based relay node. Additionally, in the relay and user link, the hybrid scheme selects a transmit antenna of the relay node and a selection combining (SC)-based user node. This study presents new exact cumulative distribution function (CDF) expression of the received signal to noise ratio (SNR) for GSC. Using the CDF for GSC, this research derives the new exact and approximate CDF expressions of the hybrid combining scheme for the received SNR. Using the exact CDF, this paper newly derives the lower bound and exact expressions of the proposed scheme for the secrecy performance. To offer new insights, this paper quantifies the secrecy diversity order, secrecy SNR gain for the secrecy outage probability, and assesses the high SNR power offset and the high SNR slope for the secrecy rate. Numerical results show that the number of combining paths affects both the secrecy SNR gain and the high SNR power offset. Thus, we confirm that the secrecy performance of the hybrid combining scheme can be adjusted by modifying the number of combining paths without hardware reconfiguration.