Maximizing the lifetime of delay-sensitive sensor networks via joint routing and sleep scheduling

Network lifetime is critical to any battery operated wireless sensor networks (WSNs). Especially for delay-sensitive WSNs, it is challenging to prolong the network lifetime, while meeting the delay requirements of different applications. In this paper, we investigate how to optimize the network lifetime of delay-sensitive WSNs with respect to energy efficient routing and sleep scheduling. Instead of treating routing and sleep scheduling as two separate approaches, we have a joint consideration of them, and mathematically formulate the lifetime maximization problem under multiple constraints (i.e., routing, end-to-end delay bounds, sleep scheduling, energy consumption of transmission, receiving and listening, etc.). Since the formulated problem is a mixed integer non-linear programming (MINLP) problem and NP-hard to solve, we relax it into a linear programming (LP) problem and solve the relaxed problem for the upper bound. We also develop a heuristic algorithm for the feasible solution, which yields a lower bound of WSNs´ lifetime. Through extensive simulations, we show that the solution found by the proposed algorithm is close to the optimal one and the proposed scheme is effective in prolonging the lifetime of delay-sensitive WSNs.