Wireless vehicle monitoring system

• US 20020038182A1
• Filed: 03/16/2001
• Published: 03/28/2002
• Est. Priority Date: 06/06/2000
• Status: Active Grant

• Current Assignee: Satellite Service Company
• Original Assignee: Satellite Service Company
• Inventors: Wong, Carlos C.H., Tsoi, Leo S. C.
• Granted Patent: US 6,484,096 B2
• Time in Patent Office: Days
• US Class Current: 701/213
• CPC Class Codes: B60R 2325/205 Mobile phones
• CPC Class Codes: B60R 25/1025 preventing jamming or interference of said signal
• CPC Class Codes: B60R 25/33 of global position, e.g. by providing GPS coordinates
• CPC Class Codes: B60W 2556/50 of positioning data, e.g. GPS [Global Positioning System] data
• CPC Class Codes: G01C 21/28 with correlation of data from several navigational instruments
• CPC Class Codes: G08G 1/205 Indicating the location of the monitored vehicles as destination, e.g. accidents, stolen, rental

Abstract

A vehicle monitoring system provides real time monitoring of vehicles by receiving position and operational conditions from mobile units over a wireless communication link, such as a cellular telephony connection. In one embodiment, the mobile unit is equipped with both a Global Positioning System (GPS) receiver and a dead reckoning device, which provides position information when the GPS receiver is unable to receive GPS positions from a GPS satellite (e.g., when the vehicle is in a city area surrounded by tall buildings). A novel position request protocol allows multiple position reports to be included in a single data packet, thereby reducing the air time cost of transmitting data over a cellular telephony link. A novel antenna cable detects and reports tempering of a GPS antenna.

Claims

1. A mobile unit which communicates with a control center of a vehicle monitoring system, comprising:

an interface to a GPS receiver for receiving from said GPS receiver a first set of position information;

an interface to a dead reckoning device for receiving from said dead reckoning device a second set of position information;

a signal processing unit selecting between said first and second sets of position information;

a communication interface for communicating with said control center;

a control unit that controls said signal processing unit and said communication interface, said control unit retrieving from said signal processing unit said selected set of position information and providing said selected set of position information to said control center over said communication interface.

2. A mobile unit as in claim 1, wherein said control unit further comprising a storage device for accumulating said selected position information.

3. A mobile unit as in claim 1, wherein said signal processing unit selects said first set of position information when said GPS receiver has access to a GPS satellite.

4. A mobile unit as in claim 1, wherein said dead reckoning device receives signals from a digital compass.

5. A mobile unit as in claim 1, wherein said control unit comprises a microprocessor.

6. A mobile unit as in claim 1, wherein said GPS receiver comprises an antenna cable for connecting an antenna, said antenna cable comprising:

a first conductor for providing a DC voltage to a first terminal of said antenna;

a second conductor for providing a ground reference to a second terminal of said antenna; and

a third conductor having a first end and a second end, said first end being coupled to said second conductor to form a ground loop and, at said second end being available for connection to a continuity sensing cirucit.

7. A mobile unit as in claim 6, wherein said third conductor constitute less than 2.5 ohms of impedance as seen from said second end.

8. A mobile unit as in claim 6, wherein said continuity sensing circuit providing an alarm signal when said continuity sensing circuit detects an open circuit in said ground loop.

9. A mobile unit as in claim 8, wherein said control, upon detecting said alarm signal, provides said alarm signal to said control center.

10. In a vehicle monitoring system, a method for reporting position data from a mobile unit in a data packet, comprising:

receiving a request to send a specified number of positions over a specified time interval;

acquiring said number of positions from a positioning device in said mobile unit over said specified interval; and

accumulating said acquired positions and reporting said positions in said data packet whenever reporting unreported acquired positions requires a predetermined data size.

11. A method as in claim 10, wherein said data packet having a specified length and wherein the difference between said predetermined data size and said specified length is insufficient to report a position.

12. A method as in claim 10, wherein said data packet comprises a SMS data packet in a GSM/PSC communication system.

13. A method as in claim 10, wherein said data packet positions are reported in text mode.

14. A method as in claim 10, wherein said specified number of positions is one, whereupon said acquired position is reported immediately.

16. An antenna cable as in claim 15, wherein said third conductor constitute less than 2.5 ohms of impedance as seen from said second end.

15. An antenna cable for connecting an antenna, comprising:

a first conductor for providing a DC voltage to a first terminal of said antenna;

a second conductor for providing a ground reference to a second terminal of said antenna; and

a third conductor having a first end and a second end, said first end being coupled to said second conductor to form a ground loop and, at said second end being available for connection to a continuity sensing circuit.