Maximizing the lifetime of two-tiered sensor networks

Recent technological advances in the field of microelectro-mechanical systems (MEMS) have made the development of multi-functional sensor nodes technically and economically feasible. The lifetime of sensor networks is still limited as individual sensor nodes are usually powered by battery. In the past few years, the use of relay nodes in sensor networks has been proposed in literature for balanced data gathering, reduction of transmission range, connectivity and fault tolerance. In hierarchical sensor networks, higher-powered relay nodes can also be used as cluster heads. These relay nodes may form a network among themselves and route data towards the base station. In such a sensor network, the lifetime of the network is directly related to the lifetime of these relay nodes. In this paper, we have proposed an ILP solution for scheduling the data gathering of relay nodes such that the lifetime of the relay node network is maximized. We have compared our formulation with the direct transmit energy model and shown that it can lead to significant improvements. We have also proposed a re-scheduling approach which can further extend the maximized lifetime of the network.