Buffer-Aided Relaying With Direct Link Transmission and Spectrum Sharing

Cognitive relay networks are designed to increase access to under-utilized spectrum. The direct link communication can be exploited to decrease the outage probability with a buffer-aided relaying network. To this end, a novel transmission policy is proposed to combine the benefits of direct communication and buffer-aided relaying. In addition, a modification to the hybrid interweave-underlay spectrum access policy is presented to restrict the amount of interference caused due to a miss-detection event. Assuming independent and not necessarily identical fading channels, the analytical outage probability and the end-to-end average packet delay for the secondary system are derived. Monte-Carlo simulations show that adopting the proposed policy, compared to the conventional link selection techniques, results in a significantly larger outage gain, a lower average packet delay, a higher empty buffer probability, and a lower full buffer probability. Also, the theoretical and Monte-Carlo results coincide in the provided simulation examples which verifies correctness of the theoretical analysis.