Secrecy Outage Probability of Conventional and Modified TAS/Alamouti-STBC Schemes With Power Allocation in the Presence of Feedback Errors

Modified transmit antenna selection (M-TAS)/Alamouti space-time block coding (STBC) schemes have been shown to achieve superior error performance together with a reduced feedback load in the presence of feedback errors (FEs) when compared to the conventional TAS/Alamouti-STBC schemes. By shifting the focus of the investigation, this paper answers the query on whether the modified schemes with power allocation (PA) provide enhancements in the secrecy outage probability (SOP) performance of multi-antenna schemes in wiretap channels. The exact expressions of the SOP and non-zero secrecy probabilities for both the conventional and modified schemes in Rayleigh fading channels have been derived and validated via Monte Carlo simulations. With the help of high signal-to-noise ratio approaches and approximations, the asymptotic secrecy diversity order analysis has been carried out. Besides, by providing a simulation-based examination on the inclusion of a different TAS criterion before STBC transmission, the additional advantages on the secrecy performance have been exhibited. The extensive investigation and comparisons have shown that M-TAS/PA/Alamouti-STBC schemes provide considerable enhancements in the secrecy rates of wireless communications systems in the presence of FEs.