Exact Outage Performance of the SIMO Cognitive Cooperative Network in the Presence of Co-Channel Interference

The nature of cognitive radio is based on the co-existence of secondary users in the area of primary users. Co-channel interference (CCI), therefore, is a vulnerable phenomenon in such a system. Motivated by this, a more practical scenario has been considered for studying the performance of the single-input-multiple-output (SIMO) underlay cognitive co-operative network. In this investigation, the primary transceiver is considered as well as the impact of the CCI on the secondary network. For this practical scenario, the equivalent signal-tointerference-plus-noise ratio (SINR) of the secondary system is obtained by employing the selection combining (SC) technique at the receiver side. Then, the cumulative distribution function (CDF) of the equivalent SINR is derived. Using the derived CDF, exact outage probability for the secondary network is assessed. From the results, it can be deduced that using a multi-antenna scheme and applying the SC technique has the advantage of improving the system performance. Moreover, besides the impact of the interference power constraint, the presence of the primary transmitter and the CCI will severely reduce the system performance, especially when the CCI linearly increases with the secondary transmit powers. Finally, numerical results and Monte Carlo simulations have also been provided to support the correctness of the analytical derivations.