Energy efficient searching in delay-tolerant wireless sensor networks

In this paper, we consider the problem of information discovery in densely deployed and delay-tolerant Wireless Sensor Network (WSN), where the initiator of search is unaware of the location of target information. We propose Increasing Ray Search (IRS), an energy efficient query resolution or search technique. The basic principle of IRS is to route the search packet along a set of trajectories called rays that maximizes the likelihood of discovering the target information by consuming least amount of energy. The rays are organized such that, if the search packet travels along all these rays, then the entire terrain area will be covered by its transmissions while minimizing the overlap of these transmissions. In this way, only a subset of total sensor nodes transmit the search packet while others listen. We believe that query resolution based on the principles of area coverage provides a new dimension for conquering the scale of WSN. We compare IRS with existing query resolution techniques for unknown target location such as, Expanding Ring Search, Random Walk Search, and Gossip Search. We prove by analysis and simulation that IRS is highly scalable, the energy consumed for searching is independent of node density, and it is much lower than that of existing search techniques under high node density.