On the Performance of Cognitive Underlay Alamouti Space-Time Coding Schemes

In this paper, we study the performance of underlay Alamouti schemes over Rayleigh fading channels. In particular, the closed form expressions of outage probability and Shannon capacity are derived. We develop a new derivation approach, which allows to obtain the exact form of Shannon capacity, where two interference links to the primary receiver are taken into account. Monte Carlo simulations are performed to verify the correctness of the analysis results. The numerical results show that the system achieves full diversity and outperform underlay direct transmissions.