Secrecy outage probability and diversity order of Alamouti STBC over time-selective fading channels

This paper studies physical layer security for Alamouti space-time block code (STBC) with joint maximum likelihood (JML) or zero forcing (ZF) detection techniques particularly over multi-input single-output (MISO) wiretap time-selective Rayleigh fading channels. Specifically, we derive the secrecy outage probabilities (SOPs) and their concise but effective approximations for various combinations of JML and ZF at the legitimate receiver and eavesdropper. We also investigate the secrecy diversity gain by applying the high signal-to-noise ratio (SNR) approximation of SOP and prove that the corresponding asymptotic diversity order of two, two, one, and one can be achieved for JML-JML, JML-ZF, ZF-JML, and ZF-ZF, respectively. Our asymptotic analytical results corroborate that the secrecy diversity order is dominantly affected by the detection strategy of the legitimate receiver rather than that of the eavesdropper. & COPY; 2023 The Author(s). Published by Elsevier B.V. on behalf of The Korean Institute of Communications and Information Sciences. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).