Abstract

A Cognitive radio ad hoc network (CRAHN) is an ad hoc network of primary user (PU) nodes and secondaryuser (SU) nodes, wherein the SU nodes use the licensed channels of the PU nodes when not in use. As theavailability of the PU channels fluctuates with time, communication topologies spanning the SU nodes have tobe dynamically and frequently reconfigured. Given the complete knowledge of the availability of the PUchannels, we propose a generic benchmarking algorithm that determines a sequence of stable communicationtopologies spanning all of the SU nodes such that the number of transitions from one instance of the topology toanother is the global minimum. At any time instant t when we need a stable communication topology spanningthe entire network, we look for the largest value of k such that the intersection of the static SU graphs from timeinstants t to t+k, defined as the mobile graph Gt...t+k(SU) = Gt(SU) ? Gt+1(SU) ? .... ? Gt+k(SU), is connected andthat the mobile graph Gt...t+k+1(SU) is not connected. We repeat the above procedure for the entire network sessionto determine a sequence of longest-living instances of the mobile graphs and the corresponding instances of thecommunication topology of interest (say a shortest path tree rooted at a source SU node) such that the number oftopology transitions is the minimum. We prove the theoretical correctness of the algorithm and evaluate itseffectiveness by implementing it to determine a sequence of shortest path trees of the maximum lifetime.

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