Secrecy outage analysis of MU-MIMO transmit antenna selection systems with arbitrary number of eavesdropping users

The secrecy outage performance of multiuser multiple-input-multiple-output (MU-MIMO) transmit antenna selection systems is analysed, where some of the users overhear transmissions as long as they are not scheduled currently. A general closed-form expression of secrecy outage probability is derived by ordering the qualities of paths and calculating the joint probability density functions. Numerical results are provided to illustrate the different impacts of multiuser diversity and antenna diversity on the secrecy performance.