Analysis of the impact of primary user switching strategies in cognitive radio networks

In this paper, a multi-channel cognitive radio network is considered in which both primary users (PUs) and secondary users (SUs) can sense and make use of idle channels, i.e. both kinds of users are cognitive. We study a situation where a PU, while transmitting, can sense idle channels with a better transmission rate than the one currently occupied and can switch to such a better channel. This switching behaviour affects the PU activity profile on the channels and hence also the SU throughput, since SU packet transmissions are confined to the gaps left by the PUs. Different PU switching strategies are studied by developing a continuous-time Markov chain (CTMC) for each strategy. Performance measures include the mean sojourn time of PUs as well as the saturation throughput and interruption probability of SU packets. Some specific considered scenarios quantitatively demonstrate the influence of the PU switching speed. An increased PU switching rate considerably reduces PU sojourn time, at the cost of reducing the SU throughput.