EasiMG: A method of maximizing lifetime for group request in web-based sensor network

The lightweight RESTful protocols, such as CoAP and SeaHttp, have been proposed for web-based sensor network (WBSN), which provides web service on resource-constrained devices. In general, because sensing data are spatially correlated in sensor network, it is efficient to request a group of devices located in nearby area. Thus group requesting is a typical way to provide web service for resource-constrained devices in WBSN. However, it is a critical problem that how to make an optimal assignment of nodes for a group of requests to maximize network lifetime. In this paper, we address this problem in the scenario where nodes have different initial energy, and they can process in-network group request with branch and combine methods supported by SeaHttp. We prove this problem is NP-complete and transform the problem into an edge-weighted semi-matching problem in bipartite graph using the fat tree construction algorithm. Finally we propose an approximation algorithm to solve the problem. Simulation results show that our approach prolong lifetime of the network by 29.11% on average, which is more competitive when it is applied in a high concurrency scenario compared with traditional methods.