This study considers a dual-hop cognitive inter-vehicular relay-assisted communication system where all communication links are non-line of sight ones and their fading is modelled by the double Rayleigh fading distribution. Road-side relays (or access points) implementing the decode-and-forward relaying protocol are employed and one of them is selected according to a predetermined policy to enable communication between vehicles. The performance of the considered cognitive cooperative system is investigated for Kth best partial and full relay selection (RS) as well as for two distinct fading scenarios. In the first scenario, all channels are double Rayleigh distributed. In the second scenario, only the secondary source to relay and relay to destination channels are considered to be subject to double Rayleigh fading whereas, channels between the secondary transmitters and the primary user are modelled by the Rayleigh distribution. Exact and approximate expressions for the outage probability performance for all considered RS policies and fading scenarios are presented. In addition to the analytical results, complementary computer simulated performance evaluation results have been obtained by means of Monte Carlo simulations. The perfect match between these two sets of results has verified the accuracy of the proposed mathematical analysis.

http://ieeexplore.ieee.org/document/7395050/