Research On Range-free Localization Algorithms For Wireless Sensor Networks

Wireless sensor network (WSN), as an emerging technology, has received increasing attention in the last few years. And it has a good application prospect in both civil and military fields.Wireless sensor network consist of a large number of individual sensor nodes that are able to interact with their environment by sensing or controlling physical parameters; these nodes have to collaborate to fulfill their tasks as; and they use wireless communication to enable this collaboration.In many circumstances, it is useful or even necessary for a node in a wireless sensor network to be aware of its location in the physical world. For example, tracking or event-detection functions are not particularly useful if the WSN cannot provide any information where an event has happened. Facing to so many nodes that usually are placed randomly, Manually configuring location information into each node during deployment is not an option. So there must be a mechanism to work out nodes'location in real time.The character of WSN, such as limited resource, bad dependability, short communication distance and so on, brings some challenges to node-localization. Consequently, node-localization in WSN has became a research hotspot recently. The node-localization can be divided into two kinds:range-based and range-free. Range-free localization is considered to more adapt to WSN because of its simpleness and low cost.In this paper, based on the characteristics of DV-Hop in WSN, an improved scheme for this typical range-free localization algorithm in wireless sensor network is proposed. The main principle of the improved scheme is to introduce ratio of hop as ratio of distance in the third phase of localization, then estimates locations of unknown nodes in the geometrical method. To do so, it can pass over a phase of DV-Hop in which nodes broadcast AHL to each other and save much power. In addition, to introduce RSSI makes ratio of hop more accurate in one-hop range.As same as DV-Hop, the improved algorithm retain numerous advantages, including simpleness, low requirements to hardware, distributed processing, high rate of node-localization etc. Moreover, plenty of power is saved and precision of node-localization is improved very much. Simulation result demonstrates that the improved algorithm is more reliable and robust than the traditional DV-Hop localization algorithms.