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Cognitive radio ad hoc networks (CRAHNs) solve the problem of spectrum utilization when the licensed or primary user (PU) activity changes over time. This affects not only the spectrum availability, but also the network topology, making the analysis of scaling laws very challenging. Currently, the effect of PU activity on the network scaling laws has not been theoretically analyzed, to the best of our knowledge. In this paper, throughput capacity and delay scaling laws are introduced for CRAHNs by capturing the impact of PU activity in dense, and sparse PU deployment conditions. In the former case, it is observed that the scalability for the CRAHN is very low, with the capacity strongly related to the `off' transmission times of the PU. Moreover, this is possible only under specific conditions of buffering, and queuing assumptions for the CRAHN. In the second case with sparse PUs, both the average throughput capacity and network delay of CRAHN are significantly improved. Interestingly, in both cases, the distribution of the PU locations does not impact the scalability in CRAHNs.
Date of Conference: 6-10 Dec. 2010