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In recent years, underwater wireless sensor networks (UWSNs) have been widely applied to aquatic and military applications. Network survivability is an essential attribute to be considered in UWSN circumstance and various stratifications like node survivability, connectivity and rapid fault node detection and recovery. However, efficient and accurate fault tolerance mechanisms are required to prolong the network survivability in UWSN. In this research work, the energy-efficient fault detection and recovery management (EFRM) approach is proposed for the UWSN with relatively better network survivability. The hidden Poisson Markov model has been incorporated in EFRM to achieve efficient fault detection throughout the whole network. Thereafter, the recovered node can be selected by using the analytical network process model which facilitates to recover the larger number of nodes in the damaged region. The simulation results manifest that when the fault probability is 40%, the detection accuracy of the proposed EFRM is over 99%, and the false positive rate is below 2%. The detection accuracy is improved by up to 12% when compared with the existing state-of-the-art schemes.

Wavelength division multiplexing (WDM) networks have become a viable solution to meet the increasing bandwidth demand. These networks carry messages in the optical domain at data rates of several Gb/s. Such high data rates make it necessary for using efficient restoration protocols in an event of a failure. This paper addresses the problem of dynamic path-based restoration in WDM optical networks. Our objective is to develop a protocol that ensures rapid recovery while keeping the restoration ratio high. We propose two distributed dynamic restoration protocols called disjoint path-wavelength grouping protocol and disjoint weighted path-wavelength grouping protocol. Both these protocols group all the candidate backup paths of the failed paths into path-disjoint groups before assigning wavelengths to them. This allows the failed paths to search different sets of wavelengths on various candidate backup paths in parallel without any reservation conflicts. Also, it does not require any reservation retries, thus resulting in rapid restoration. The grouping method attempts to restore increased number of failed paths by allowing increased number of wavelengths to be searched on a path. The performance of the proposed protocol is verified through extensive simulation experiments.