A Grid-Based Location Update Protocol in mobile wireless sensor networks

The introduction of mobile sinks to wireless sensor networks (WSNs) leads to several advantages such as hot-spot removal, energy balancing and longer network lifetime. However, as each sink moves freely and unpredictably in the sensing area, its location information needs to be broadcasted periodically to ensure network connectivity. This process results in unexpected communication overhead in each sensor node. In this paper, a Grid-Based Location Update Protocol (GBLUP) is proposed. In GBLUP, the sensing area is divided into virtual grids, and a sensor node is selected as the anchor in each grid. Sensor nodes inside the Current Grid (CG) report their sensing data directly to the mobile sink. While sensor nodes in other grids only send their Data Submitting Requests (DSRs) to the anchor, the anchor decides whether the source´s data packets will be forwarded to the sink or not. In this way, when the sink moves inside the CG, location update will be confined in the local grid. When the sink needs to move out of the CG, its location information will only be updated in the anchors. Besides, both the optimal size of the grid and the max sojourn time in a grid are considered jointly to further improve the GBLUP performance. Simulation results demonstrate that GBLUP outperforms the traditional protocols in reducing the energy consumption of location update and prolonging the network lifetime_.