Secure opportunistic scheduling with transmit antenna selection

We investigate the physical layer security for opportunistic scheduling scheme using transmit antenna selection (TAS) with maximal ratio combining (MRC) at receiver and eavesdropper under a quasi-static Rayleigh fading channel. We assume a scenario composed of a single transmitter, multiple users and a single eavesdropper each equipped with multiple antennas. The transmitter selects best transmit antenna and best user to enhance the secure communication. A theoretical analysis is performed to derive new closed form expressions for probability of positive secrecy and outage probability at a normalized secrecy rate. Furthermore, asymptotic analysis on the outage probability reveals the outage diversity gain and array gain. It is confirmed that number of antennas at eavesdropper impacts on secrecy array gain while the outage diversity gain is determined by the product of number of users and antennas at the transmitter and the user. From numerical results, TAS is verified as a suitable option for secure opportunistic scheduling.