Performance Study of the Dual-hop Underlay Cognitive Network in the Presence of Co-Channel Interference

Cognitive radio allows secondary users to use the same existing frequency spectrum band as primary users. This co-existence has several impacts on the whole network. This has motivated us to study the performance of a more practical dual-hop underlay cognitive network, by considering the interference power constraint, the primary transceiver and the co-channel interference (CCI). We start by determining the equivalent signal-to-interference-plus-noise ratio (SINR) of the secondary network, then, we derive the cumulative distribution function (CDF) of the equivalent SINR. Using the derived CDF, system outage probability has been assessed. Furthermore, an approximate expression for the system average error probability has been derived. From the results it can be observed that 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 power. Finally, numerical results and Monte Carlo simulations are also provided to sustain the correctness of the analytical derivations.