LEEF: Latency and energy efficient federation of disjoint wireless sensor segments

In hostile environments where explosives and natural calamities probably occur, wireless sensor networks (WSNs) are susceptible to multiple collocated failures and could be partitioned into disjoint segments. Federating the segments would be essential for restoring connectivity and enabling data sharing in the network. The federation may be achieved by populating relay nodes and providing perpetual inter-segment paths. In this paper, we tackle the federation problem while considering constrained relay availability, i.e., a limited number (k) of mobile relays to provide intermittent inter-segment connectivity that makes the problem more challenging. We propose LEEF, a novel algorithm for achieving energy-efficient federation with low inter-segment data delivery latency. LEEF strives to group the segments into k clusters in a star topology where a cluster at the center of the area serves as a hub between each pair of segment-clusters. Each cluster is served by a distinct mobile relay. In addition, LEEF opts to equalize the energy consumed by the k mobile relays due to travel and wireless communication. We analyze the properties of LEEF mathematically and validate its performance through extensive simulation experiments.