Communications: directive radio wave systems and devices (e.g. – Directive – Including a satellite
Reexamination Certificate
1999-10-25
2001-05-22
Tarcza, Thomas H. (Department: 3662)
Communications: directive radio wave systems and devices (e.g.,
Directive
Including a satellite
C342S357490, C342S357490
Reexamination Certificate
active
06236357
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to automatic vehicle location systems. More particularly, the present invention relates to a reduction in the resource requirements for automatic vehicle location systems where the position of a large number of vehicles is frequently transmitted to a Dispatch Center.
2. Background
Automatic Vehicle Location (AVL) systems are used to keep track of a fleet of field vehicles for more efficient assignment of tasks in the field, monitoring productivity, and other reasons. Such systems typically have a Dispatch Center which receives a constant stream of position update messages that alert the Dispatch Center to any changes in the position of the vehicles. For example, each vehicle in the fleet sends a position update message to the Dispatch Center every 10 seconds.
Each field vehicle contains a mobile unit at least having an AVL box, a Mobile Data Terminal (MDT) usually in the form of a laptop or notebook computer, and a transceiver for broadcasting position update messages and for receiving information and instructions from the Dispatch Center.
The Dispatch Center of such a system includes a dispatch system, which stores logic and information (such as electronic maps) needed to receive and process position update messages from the fleet of field vehicles, and a transceiver for transmitting and receiving messages to and from the fleet of field vehicles.
A common use for an automatic vehicle location system is the tracking of public safety vehicles such as police cars, fire engines, paramedic vehicles and the like. In large municipalities with a great number of field vehicles to be monitored, the combination of a fixed bandwidth allocated for such services and the requirement that frequent position update messages be sent can cause “bottlenecks” and overwhelm the system, causing overall poor system performance.
There is a dire need to provide an AVL system with a lower bandwidth requirement for optimum system performance.
SUMMARY OF THE INVENTION
In view of the aforementioned shortcomings of the prior art, the present invention provides an automatic vehicle location method for monitoring by a Dispatch Center, the position of at least one vehicle. The method includes the steps of, via the Dispatch Center, tracking the changes in the position of a vehicle with respect to an electronic map, the map having predefined decision points, via a mobile unit in a vehicle, receiving position signals from the transmitter of a position system, and storing in the mobile unit, an identical map. The method also includes the steps of, via an automatic vehicle location (AVL) box in the mobile unit, monitoring vehicle movement change indicia, and upon reaching a decision point, transmitting position and movement update messages to the Dispatch Center only when one or more vehicle change indicia cross a predetermined threshold. Additionally, the method includes the step of, in both the Dispatch Center and the vehicle, extrapolating the position and movement of the vehicle between decision points by following a projected path on the map according to the same algorithm.
The present invention also provides an automatic vehicle location system adapted to monitor the position of at least one vehicle. The system includes a Dispatch Center adapted to track the changes in the position of a vehicle with respect to an electronic map, the map having predefined decision points, and a mobile unit in the vehicle adapted to receive position signals from the transmitter of a position system. The mobile unit is also adapted to store a map identical to the one stored by the Dispatch Center.
The system also includes an AVL box subsumed by the mobile unit and adapted to monitor vehicle movement change indicia, and extrapolators in the Dispatch Center and the mobile unit. The mobile unit is adapted to, upon reaching a decision point, transmit position and movement update messages to the Dispatch Center only when one or more vehicle change indicia cross a predetermined threshold. Both extrapolators are adapted to extrapolate the position and movement of the vehicle between decision points by following a projected path on the map according to the same algorithm.
REFERENCES:
patent: 5751245 (1998-05-01), Janky et al.
Lucent Technologies - Inc.
Mull Fred H
Tarcza Thomas H.
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