Study on Enhanced Fault Tolerance in WSAN with Minimal Topology Changes

In wireless sensor-actor networks, sensors probe their surroundings and forward their data to actor nodes. Actors collaboratively respond to achieve predefined application mission. Since actors have to coordinate their operation, it is necessary to maintain a strongly connected network topology at all times. Moreover, the length of the inter-actor communication paths may be constrained to meet latency requirements. However, a failure of an actor may cause the network to partition into disjoint blocks and would, thus, violate such a connectivity goal. One of the effective recovery methodologies is to autonomously reposition a subset of the actor nodes to restore connectivity. Contemporary recovery schemes either impose high node relocation overhead or extend some of the inter-actor data paths. This project overcomes these shortcomings and presents a Least-Disruptive Topology Repair (LDTR) algorithm. LDTR relies on the local view of a node about the network to devise a recovery plan that relocates the least number of nodes and ensures that no path between any pair of nodes is extended. The experiments have also compared LDTR with a centralized version and to contemporary solutions in the literature. The results have demonstrated that LDTR is almost insensitive to the variation in the communication range. LDTR also works very well in dense networks and yields close to optimal performance even when nodes are partially aware of the network topology. LDTR can recover from a single node failure at a time. Generally, simultaneous node failures are very improbable unless a part of the deployment area becomes subject to a major hazardous event, e.g., hit by a bomb. Considering such a problem with collocated node failure is more complex and challenging in nature. The performance of LDTR is analyzed mathematically and validated via extensive simulation experiments.