Low cost data gathering using mobile hybrid sensor networks

In this work we study energy efficient hybrid sensor network design using mobile sinks, motivated by the practical GreenObs system application. In our model, the movement of mobile sinks is constrained to be on some predefined road-segments. Two different network structures are investigated: the one-hop structure in which each static sensor can be reached by the mobile sink at some stage of the movement, and the multi-hop structure where some sensors need the relay by other sensors to reach the sink. The challenge is to find a movement schedule of mobile sink that will minimize the energy cost while meet other constraints. In this work, we first show that the problem is NP-hard and then design an efficient movement scheme and theoretically prove that the total cost is within a constant factor of the optimum. We further present a scheduling solution using integer program for multi-hop structure, which is near optimal and can be computed in polynomial time. Finally, we conduct extensive study of our method in a real wireless sensor network deployment composed of hundreds of static sensors. Our experiments validate the theoretical findings of our method.