Mobile-Element Data Gathering Scheme

In sensor network applications, data gathering mechanisms, which are based on multi-hop forwarding can be expensive in terms of energy. This limitation reduces the lifetime of the network and challenges the use of sensor networks for applications that demand a predefined operational lifetime. To avoid this problem, the benefits of using mobile gateway to prolong sensor life-time have been explored in the literature. However, practical considerations such as the gateway speed and route planning, sensor buffer size and data frequency generation constraints impose limits on the mobile elements. In this work, we consider the natural hybrid solution that combines the two approaches of mobile gateways and multi-hop forwarding to address more constraints for sensor applications. We provide algorithmic solutions that attempt to balance the benefits of both approaches. Based on a given predetermined time deadline, a gateway tour will be established to involve a subset of the sensors. These selected sensors will work as gathering points and will aggregate the other sensors´ data. The gathering points/nodes are selected with the aim of reducing the energy expenditures due to multi-hop forwarding. Using approximation-preserving reductions, we discuss the hardness of this problem. We also present a heuristic-based solution and validate its performance through an extensive set of experiments.