Lifetime maximization using observation time scheduling in multi-hop sensor networks

Prolonging lifetime is a key challenge in wireless sensor networks comprising unattended, limited resource sensor nodes. As sensors are usually densely deployed, redundant data is produced by multiple observations on the same event, which decreases the network lifetime. With each observing sensor acting as a source of data, we schedule the time when these sources are allowed to send data to prolong the network lifetime with the guarantee that the total data provided satisfies the application requirement at any time. Considering k-coverage of each target as the application requirement, we propose the observation time scheduling for network lifetime maximization (OSLM) problem and solve it for two observation scenarios: a) a sensor node can distinguish the targets in its sensing range and selects a subset of targets to observe and b) a sensor node has to simultaneously observe all the targets in its sensing range as it cannot distinguish targets. We develop an optimal solution using a linear programming (LP) problem formulation for OSLM problem for the first observation scenario and solve it using CPLEX package. We prove that OSLM problem for the second observation scenario is NP-complete. A heuristic algorithm for the second scenario is then proposed. The performance is evaluated by the numerical results obtained from CPLEX and extensive simulation results