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Re-establishing network connectivity in post-disaster scenarios through mobile cognitive radio networks

Network interoperability and self-organization constitute important communication requirements in disaster recovery scenarios. Here, the original communication infrastructure might be partially or completely damaged, and the whole network might be partitioned into segments (called islands in the following) that might operate on different frequencies/wireless technologies. In this paper, we investigate techniques to maximally re-establish the connectivity among heterogeneous islands through the utilization of specialized repairing units called Stem Nodes (SNs). A SN combines spectrum reconfigurability (offered by the Software Defined Radio technology) with self-positioning and dynamic routing functionalities, and thus it is able to replace damaged components of the original infrastructure. Moreover, sets of SNs can self-organize into multi-hop mesh structures connecting heterogeneous islands. We study the problem of determining the optimal deployment of SNs so that the number of connected devices of the original network is maximized. Given the NP-hardness of the problem, we propose approximated solutions with reduced computational complexity. We then compare the centralized solution with a distributed algorithm (based on virtual springs approach) that enables SNs to explore the environment in both space/frequency domains, and to self-organize into virtual mesh structures. Simulation results confirm the effectiveness of the distributed algorithm to maximally re-establish the network connectivity even on large-scale scenarios.