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In this paper, dynamic spectrum leasing strategies (with and without anticipated resource leasing) for coordinated cognitive radio networks are proposed to mitigate the effects of unpredictable resource availability. 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. Additionally, to finely control the provided quality of service, fractional channel reservation to prioritize ongoing secondary calls over new ones is considered. A teletraffic mathematical analysis for the performance evaluation of the proposed strategies is developed. The tradeoff between the spectrum leasing cost and the system Erlang capacity is also investigated. For a given maximum allowed number of simultaneously rented channels, maximum Erlang capacity is obtained by optimizing the number of reserved channels for different traffic scenarios. Numerical results reveal that system performance strongly depends on the value of the mean secondary service time relative to the mean primary service time. Finally, the cost per capacity a function of both the utilization factor of the primary resources and the maximum allowed number of simultaneously rented channels is evaluated.Keywords-overlay cognitive radio networks, dynamic spectrum leasing, Erlang capacity, call admission control, new call blocking and call forced termination probabilities.

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