Physical Layer Security of QSTBC With Power Scaling in MIMO Wiretap Channels

Quasi-orthogonal space time block codes with power scaling (QSTBC-PS) that linearly combines two Alamouti codes with unequal power scaling has been known to achieve full diversity in multi-input multi-output (MIMO) systems. In this correspondence, we evaluate the physical layer security performance of QSTBC-PS in MIMO wiretap channels under Rayleigh fading. We derive the tight closed-form approximate formula of secrecy outage probability for QSTBC-PS by using moment matching approximation technique. Further, we derive the high signal-to-noise ratio (SNR) approximation and the probability of strictly positive secrecy capacity in explicit form. The numerical examples validate that our analytical results match well to the Monte-Carlo simulation results for general number of receive antennas at the desired receiver and eavesdropper.