Wireless vehicle monitoring system

• US 6,484,096 B2
• Filed: 03/16/2001
• Issued: 11/19/2002
• Est. Priority Date: 06/06/2000
• Status: Expired due to Fees

• Current Assignee: Satellite Service Company
• Original Assignee: Satellite Service Company
• Inventors: Tsoi, Leo S. C., Wong, Carlos C. H.
• Primary Examiner(s): Cuchlinski, Jr., William A.
• Assistant Examiner(s): To, Tuan C
• Application Number:
  US09/811,273
• Publication Number:
  US 20020038182A1
• Time in Patent Office: 613 Days
• Field of Search: 701/213, 701/214, 701/216, 455/427, 455/429, 455/12.1, 455/456, 342/450, 342/362, 342/378, 342/357.09, 342/457, 375/347, 375/200
• 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:

a GPS receiver connected to a GPS antenna by an antenna cable;

an interface to said 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 for selecting between said first and second sets of position information;

a communication interface for communicating with said control center;

a control unit for controlling said signal processing unit and said communication interface, said control unit retrieving from said signal processing unit said selected set of position information and causing said selected set of position information to be transmitted to said control center over said communication interface;

wherein said said antenna cable comprises a first conductor for providing a DC voltage from a power supply comprised by said GPS receiver 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 said second end being connected to a continuity sensing circuit comprised by said GPS receiver.

2. A mobile unit as in claim 1, wherein said control unit further comprises 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 third conductor exhibits less than 2.5 ohms of impedance as seen from said second end.

7. A mobile unit as in claim 1, wherein said continuity sensing circuit provides an alarm signal when said continuity sensing circuit detects an open circuit in said ground loop.

8. A mobile unit as in claim 7, wherein said control unit, upon detecting said alarm signal, provides said alarm signal to said control center.

9. A method for communicating position data from a mobile unit carried by a vehicle to a control center of a vehicle monitoring system, said mobile unit comprising:

a GPS receiver connected to a GPS antenna, said GPS receiver providing a first set of position information;

a dead reckoning device providing a second set of position information;

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

a control and transmitting unit for retrieving said selected set of position information from said signal processing unit and transmitting said selected set of position information to said control center in a data packet transmitted over said communication interface in response to a request received from said control center,

said method comprising the following steps, performed by said mobile unit;

receiving a request from said control center 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;

accumulating said acquired positions;

monitoring the quantity of unreported accumulated positions; and

reporting said unreported accumulated positions in a data packet whenever said quantity of unreported accumulated positions reaches a predetermined data size.

10. The method of claim 9, wherein said data packet comprises a SMS data packet in a GSM/PSC communication system.

11. The method of claim 9, wherein said data packet positions are reported in text mode.

12. 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.

13. An antenna cable as in claim 12, wherein said third conductor constitute less than 2.5 ohms of impedance as seen from said second end.