Coverage based expanding ring search for dense wireless sensor networks

Expanding Ring Search (ERS) is a prominent technique usedfor information discovery in multi-hop networks where the initiator ofsearch is unaware of any of the γ locations of the target information. ERSreduces the overhead of search by successively searching larger numberof hops starting from the location of search initiator. Even though ERSreduces overhead of search compared to flooding, it still incurs huge costwhich makes it unsuitable especially to energy constrained networks likeWireless Sensor Networks (WSNs). Moreover, the cost of search usingERS increases with node density, which limits its scalability in denselydeployed WSNs. In this paper, we apply the principles of area coverageto ERS and propose a new protocol called Coverage Based ExpandingRing Search (CERS(k), where k is the amount of parallelism in search)for energy efficient and scalable search in WSNs. CERS(k) is configurablein terms of energy-latency trade-off which enables it applicable tovaried application scenarios. The basic principle of CERS(k) is to routethe search packet along a set of ring based trajectories that minimizesthe number of messages transmitted to find the target information. Webelieve that query resolution based on the principles of area coverageprovides a new dimension for conquering the scale of WSN. We compareCERS(k) with the existing query resolution techniques for unknown targetlocation such as, ERS, Random walk search, and Gossip search.