Performance Analysis of Opportunistic Cooperation Schemes in Cognitive Radio Networks

Abstract

In this paper, we propose an opportunistic cooperation scheme in a two-user buffer-aided cognitive radio network. In each time slot, the secondary user (SU) will either transmit its own packets, or help the primary user to forward packets, based on a priority factor $\alpha$ . According to previous cooperation schemes, some time slots will be wasted if the selected buffer is empty. However, under the proposed scheme, these time slots will be handed over to the nonempty buffer's transmission, which increases the average service rates of buffers at the SU. Considering the bursty nature of sources, we characterize the evolution of buffer states by using the Markov chain. By calculating the probability of time slot handing over, the increased service rates can be theoretically analyzed, so as to the improvements on the stable throughput region and the average end-to-end transmission delay. Moreover, we further discuss the throughput and delay tradeoffs between the two users, which indicates that we can control the traffic load by adjusting the priority factor. Simulations validate our analysis, and reveal that the proposed cooperation scheme with time slot handing over offers a far larger throughput while maintaining a shorter transmission delay compared with previous schemes.