Centralized and Distributed Algorithms for Stable Communication Topologies in Cognitive Radio Ad hoc Networks

Abstract

A Cognitive radio Ad hoc network (CRAHN) is an ad hoc network of primary user (PU) nodes and secondary user (SU) nodes, wherein the SU nodes tend to access the licensed channels of the PU nodes when not in use. As the availability of the PU channels fluctuates with time, communication topologies spanning the SU nodes have to be dynamically and frequently reconfigured. Our objective is to determine stable communication topologies (like paths, trees, etc.) for the SU network that last for a longer time. In this pursuit, our contributions in this chapter are two fold: First, given the complete knowledge of the availability of the PU channels, we propose a generic benchmarking algorithm that determines a sequence of stable communication topologies spanning all of the SU nodes such that the number of transitions from one instance of the topology to another is the global minimum. Second, we propose a distributed local spectrum knowledge-based stable path routing protocol called the Maximum Common Primary User channel-based Routing (MCPUR) protocol that prefers to choose an SU-SU source-destination (s-d) path with the largest value for the sum of the number of common PU channels available for use across each of its constituent SU-SU edges; our hypothesis is that the SU-SU edges with a larger number of common available PU channels are likely to exist for a longer time.