Modeling and Analysis of Physical Layer Security of OTFS Systems Under Transmit Antenna Selection and Passive Eavesdropping

Secrecy outage probability (SOP) of orthogonal time frequency space (OTFS) systems is analyzed under transmit antenna selection (AS), passive eavesdropping and practical pulse shaping. New expressions for signal-to-noise ratio (SNR) at the legitimate receiver, SNR at the eavesdropper and SOP are developed. The analysis exploits the block diagonal nature of the time-domain channel, block circulant nature of the delay Doppler channel, statistical modeling based on gamma distribution, order statistics and Gauss-Laguerre quadrature. We also present asymptotic analysis to analyze the secrecy diversity order and secrecy array gain. Results are presented to elucidate the impact of number of antennas, speed, target secrecy rate and number of radio frequency chains on SOP. Benchmarking against no AS and full complexity system is presented to illustrate the performance complexity trade-off.