Use of radio propagation maps in a single moving beacon assisted localization in MANETs

A mobile ad-hoc network (MANET) of small robots (sensor nodes) adjusting their positions to establish network connectivity would be able to provide a communication infrastructure in an urban battlefield environment. A sensor node would be capable of moving to a particular position to establish network connectivity, provided it knows its current position, positions of other sensor nodes and the radio propagation characteristics of the sensor area. Typically, the nodes in the MANET determine their positions using a localization algorithm. Most localization algorithms use either the free space or the “two ray” radio propagation models, which are only accurate in communication environments where there are no hills or buildings. In an urban environment, direct transmission through buildings is limited and most communications rely on reflections and refractions around buildings. The presence of the buildings, therefore, greatly influences radio propagation. Consequently, free space or two-ray propagation models are inaccurate in outdoor urban areas. This paper, presents a single moving beacon assisted localization algorithm that incorporates an urban radio propagation map to localize sensor nodes in a MANET. First, the paper describes using a convex hull to represent irregular radio propagation shapes in terms of regular geometric shapes. Next, an algorithm to determine intersection (localized area) of multiple convex hulls is discussed. Simulation results, comparing the performance of localization using an urban radio propagation map against the free space model are presented. The simulation results show the effect of the radio propagation map on localization accuracy and demonstrate the free space model inaccuracy.