Abstract-Repairing connectivity and achieving a certain level of fault tolerance are two important research challenges in wireless sensor networks that have, in many papers in the literature, been jointly studied. Most of the proposals that aim at restoring network connectivity deal with the network as a general graph of N nodes with the edge cost being the number of nodes needed to establish connectivity between the two ends of the edge. This assumption ignores the topological properties of the network, especially the overlap between sensors' communication ranges, and the node-failure pattern that caused the disconnection. In this paper, we try to exploit these properties to minimize the number of additional nodes needed to repair the connectivity.

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Abstract-Cognitive radio networks (CRN) have emerged as a promising, yet challenging, solution to enhance spectrum utilization, thanks to the technology of cognitive radios. In this work, we consider the multicast routing and channel allocation problem in cognitive radio mesh networks. Due to the potential heterogeneity in channel availability among mesh routers (MRs) and the frequency switching latency, end-to-end delay and throughput degradation could be subject to a significant increase. We propose an on-demand multicast routing and channel allocation algorithm that takes channel heterogeneity and switching latency into consideration. The algorithm aims at reducing the end-toend delay, and at the same time reducing the degradation of throughput using a dynamic programming approach.

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