Date of Award
Doctor of Philosophy
The sensor nodes in Wireless Sensor Networks (WSNs) and Mobile Sensor Networks (MSNs) can be prone to failures due to limited resources and/or the harsh environments where they are deployed. The network may be subject to partitioning if such failures are experienced by the cut-vertex nodes in the system. In case of partitioning, connectivity of the nodes in disjoint partitions with the sink node is disrupted. This not only affects the data delivery but also the possible cooperation and coordination of the nodes in handling certain events. To restore the connectivity of a partition with the rest of the network, network topology should be adjusted through either exploiting existing mobile nodes in the network or introducing additional relay nodes (RNs) to the network. However, both solutions pose certain challenges. In the former case, the mobility of the nodes requires significant energy consumption and thus the movement distance should be minimized. In addition, if the scope of the damage is too wide, determining the nodes to be relocated and their final locations is another challenge. In the latter case, determining the number of RNs and a self-configuring scheme for their movement destinations need to be tackled. In case of unavailability of sufficient RNs to provide connectivity with stable links to the whole network, another solution can be providing intermittent connectivity to the partitions by employing RNs as Mobile Data Collectors (MDCs). A mixed solution where some of the RNs are employed as MDCs and some as stationary RNs raises the challenge of determining the number of stationary RNs and identifying their locations, assigning MDCs to serve partitions uniformly in such a way that the tour lengths of MDCs are minimized and the load among the MDCs are balanced. In this dissertation, we address the connectivity restoration problem in partitioned WNSs and MSNs due to large scale damages. We present centralized and distributed approaches while considering four cases: 1. Minimizing the movement cost of the nodes while utilizing existing nodes in the network in case of the availability of the mobile nodes/actors. 2. Minimizing the number of relay nodes to be used and their movement cost in case of the lack of mobile nodes/actors in the network. 3. Maximizing the number of nodes served with a stable link while not exceeding the maximum tour length defined on MDCs when a mixed solution is required where some or all of the RNs are employed as MDCs. 4. Considering QoS constraints and rendezvous waiting time when multiple MDCs are in use. The effectiveness of all proposed approaches are validated through extensive simulation experiments.
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