Tracking system using an existing wireless network

A system for tracking an object being provided with a tracking wireless transceiver and a positioning system in communication with the tracking wireless transceiver is disclosed. The system includes a receiver for receiving an indication that the object needs to be tracked; a pager for paging the tracking wireless transceiver; and a trigger for activating the positioning system, so that the positioning system obtains preliminary positioning information from the positioning system and relays the preliminary positioning information to the tracking wireless transceiver. The tracking wireless transceiver sends the preliminary positioning information to a central location. The system also includes a beacon for emitting a signal, which is activated when the tracking wireless transceiver has been paged. The system further includes a radio location finder for tracking the object based on the preliminary positioning information and a direction of travel of signals emitted by the beacon and received at a search vehicle.

DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION As mentioned previously, the present invention concerns a tracking system and method which is an improvement over the prior art, and more particularly, over U.S. Pat. No. 5,895,436. In present tacking systems, a tracking wireless transceiver 30 is placed on board the vehicle or object. Power means are provided by a battery, such as car battery in FIG. 1 , and battery backup means 32 are also preferably provided. Transceiver 30 is provided with a power supply 33 , a processor 34 , RF circuitry 35 and an optional input/output circuit 36 , which may be connected to sensors 37 , ignition 38 (in the case of a vehicle), and have an audio output 39 . In the context of the present invention, transceiver 30 is further provided with a positioning system 340 , in this case preferably a GPS module, which is adapted to receive positioning information from a constellation of satellites. Other independent positioning systems can also be used for the purposes of the present invention. When an object or vehicle 40 needs to be tracked, means are provided for receiving an indication that the object needs to be tracked, such as an owner reporting to a security service provider 44 theft of a vehicle. The tracking wireless transceiver 30 on board vehicle 40 is paged, preferably through a data communication channel of a cellular network, although other means are contemplated by the present invention. When transceiver 30 is paged, processor 34 activates the positioning system 340 , so that the positioning system obtains positioning information from a plurality of satellites and relays this positioning information to the tracking wireless transceiver 30 . Through the same channel, or another channel, the tracking wireless transceiver 30 sends the positioning information to a central location 44 . The transceiver also activates a beacon 350 . The beacon is preferably an RF emitter, which emits, sporadically, regularly or continuously, a signal. The central location 44 sends the initial tracking information to a tracking vehicle 48 , which is provided with radio location finder means for tracking the object based on the preliminary positioning information and a direction of travel of RF signals emitted by the wireless transceiver and received at a search vehicle. Consequently, when the object needs to be tracked, the search vehicle obtains preliminary location information from the positioning system, i.e. the GPS system. Afterwards, the search vehicle relies on the beacon emitted by the tracking wireless transceiver to obtain more precise location information and eventually located the object that needs to be tracked. As mentioned previously, in a preferred embodiment of the invention, the positioning system is a GPS system. Such systems are commercially available. The GPS system can be wired to the tracking wireless transceiver, which has the disadvantage of somewhat compromising the stealthness of the location equipment on board the vehicle, although there are more recent GPS systems which can be partially hidden from view. Alternatively, the GPS can be in wireless communication with the tracking wireless transceiver on board the vehicle. For the purposes of the present invention, since in any event a tracking vehicle will be used to track the object using a beacon activated by the transceiver 30 , the accuracy of the positioning system does not need to be high, and can be, for example, within 500 meters. Furthermore, since only the positioning information is sent to the central location, the use of a cellular network is minimised, and does not require the cellular operator to divulge proprietary information. It should be understood that in the context of the present invention, an object that need to be tracked includes vehicles, machinery, ships, or anything or anybody else which can be equipped with a transceiver 30 .