Understanding the Information Propagation Speed in Multihop Cognitive Radio Networks

Information propagation speed (IPS) in a multihop cognitive radio network (CRN) is an important factor that affects the network´s delay performance and needs to be considered in network planning and routing protocol design. The impact of primary user (PU) activities on IPS makes the problem of analyzing IPS in multihop CRNs very challenging and, hence, unsolved in existing literature. In this paper, we fill this technical void. We establish models of IPS in multihop CRNs and compute how to maximize IPS in two cases. The first case, named the maximum network IPS, maximizes IPS across a network topology over an infinite plane. The second case, named the maximum flow IPS, maximizes the IPS between a given pair of source and destination nodes separated by a fixed distance. We reveal that both maximum IPSs are determined by the PU activity level and the placement of secondary user (SU) relay nodes. We design optimal relay placement strategies in CRNs to maximize these two IPSs under different PU activity levels. The correctness of our analytical results is validated by simulations and numerical experiments.