Dynamic spectrum leasing strategies for coordinated cognitive radio networks with delay-tolerant traffic

In this paper, dynamic spectrum leasing strategies (with and without anticipated resource leasing) for coordinated cognitive radio networks with delay-tolerant (best effort) traffic are proposed and analyzed to mitigate the effects of unpredictable resource availability. To exploit the tolerance to delay a buffer for preempted secondary calls is considered. From the mathematical point of view, our contribution is to develop a teletraffic model for the performance evaluation of the proposed strategies. The tradeoff between the spectrum leasing cost and system Erlang capacity is also investigated. For a given maximum allowed number of simultaneously rented channels and Quality of Service (QoS) requirement in terms of new call blocking probability, maximum Erlang capacity is obtained for different traffic scenarios. Numerical results reveal that system performance strongly depends on the value of the mean secondary channel holding time relative to the mean primary channel holding time. Finally, the cost per capacity and mean transmission delay as a function of both the utilization factor of the primary resources and the maximum allowed number of simultaneously rented channels is evaluated. It is shown that anticipated resource leasing is an effective mechanism to increase the possibility to have available resources when needed for the secondary network.