Analysis of an electronic fence element for a vehicle location system

At the present time there is much interest in vehicle location systems [1]-[3]. For certain applications [4]-[7] precise location of the vehicle is not needed and determination that the vehicle is within a zonal area of the city is sufficient. This paper considers a vehicle location system in which an array of transmitters forms an "electronic fence" along the zone boundaries. As it passes throagh the electronic fence a suitably equipped vehicle receives and stores the zonal location information. This information is sent by the vehicle to a central location via a separate radio channel after receiving an interrogation message. The analysis of the communication performance of the short-range communications link between the zonal transmitters and the vehicle is the concern of this paper. Design curves and formulas are presented that allow performance calculations to be made. The implications of this predicted communication performance to a vehicle locator system are then considered. Most of the results obtained are directly applicable to a general class of vehicle location systems, which utilize the proximity of a vehicle to some coded electronic signpost to determine the vehicle\´s location. The electronic fence is a special case of the proximity-type system.