SYNCHRONIZATION SYSTEM AND METHOD FOR ACHIEVING LOW POWER BATTERY OPERATION OF A VEHICLE LOCATING UNIT IN A STOLEN VEHICLE RECOVERY SYSTEM WHICH RECEIVES PERIODIC TRANSMISSIONS

• US 20140105341A1
• Filed: 11/18/2013
• Published: 04/17/2014
• Est. Priority Date: 10/23/2009
• Status: Active Grant

• Current Assignee: Calamp Wireless Networks Inc. (CalAmp Corporation)
• Original Assignee: LoJack Corporation (Solera Holdings Incorporated)
• Inventors: Meacci, Fabio, Goodwin, Michael, Justice, James A., Rhodes, Jesse L.
• Granted Patent: US 9,112,674 B2
• Time in Patent Office: Days
• US Class Current: 375/362
• CPC Class Codes: H04L 7/0079 Receiver details
• CPC Class Codes: H04L 7/0083 taking measures against momentary loss of synchronisation, e.g. inhibiting the synchronisation, using idle words or using redundant clocks
• CPC Class Codes: H04L 7/04 Speed or phase control by synchronisation signals H04L7/0075 takes precedence
• CPC Class Codes: H04W 52/0216 using a pre-established activity schedule, e.g. traffic indication frame
• CPC Class Codes: H04W 52/0251 using monitoring of local events, e.g. events related to user activity
• CPC Class Codes: H04W 52/028 switching on or off only a part of the equipment circuit blocks
• CPC Class Codes: H04W 56/005 compensating for timing error by adjustment in the receiver
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

Synchronization for achieving low power battery operation of a vehicle locating unit in a stolen vehicle recovery system whose radio receiver receives periodic transmissions, includes receiving periodic transmissions; turning on a radio receiver for a limited time to detect an expected message; if an expected message is not found, turning off the receiver and turning it on again after a time asynchronous with the transmission period; and after finding an expected message, waiting for the period of the transmissions less the length of an expected message and then looking for a synchronization symbol in the expected message and synchronizing subsequent actuation of the receiver using that synchronization symbol.

Claims

1-14. -14. (canceled)

15. A system for maintaining synchronization with a periodic transmission from one of a plurality of transmission sources while achieving low power battery operation of a vehicle locating unit in a stolen vehicle recovery system, the periodic transmission occurring during a transmission cycle period and including an expected message that has a transmission duration, the system comprising:

a selectively-actuatable radio receiver for receiving during periods of actuation the periodic transmissions from the one of a plurality of transmission sources; and

a microprocessor configured to look for a synchronization symbol in the expected message and to synchronize subsequent actuation of the radio receiver using the synchronization symbol;

to reacquire a warm start synchronization if synchronization is lost; and

to acquire a cold start synchronization if the warm start synchronization fails to reacquire synchronization.

16. The system of claim 15, wherein the plurality of transmission sources includes a number of phased transmission sources.

17. The system of claim 16, wherein, during the transmission cycle period, each phased transmission source of the number of phased transmission sources transmits a burst that has a burst duration and that includes a plurality of message indexes.

18. The system of claim 15, wherein reacquiring warm start synchronization includes further adapting the microprocessor to:

re-check for synchronization a predetermined number of times; and

, if synchronization is not detected, to look for a synchronization symbol after waiting for a length of time.

19. The system of claim 18, wherein if synchronization is not detected after rechecking for the predetermined number of times, the microprocessor is adapted to acquire the cold start synchronization.

20. The system of claim 18, wherein warm start synchronization fails to reacquire synchronization if, after the predetermined number of times, loss of synchronization remains.

21. The system of claim 18, wherein the length of time is equal to a difference between the cycle period of the transmissions less a transmission duration of the expected message.

22. The system of claim 15, wherein acquiring cold start synchronization includes further adapting the microprocessor to:

turn on the radio receiver for a limited time to look for the expected message; and

if the expected message is detected, to wait for a length of time before turning on the radio receiver to synchronize;

otherwise, if the expected message is not detected, to repeatedly turn off the radio receiver for a time asynchronous with the transmission cycle period and to turn it on again until the expected message is detected.

23. The system of claim 22, wherein the length of time is equal to the difference between the transmission cycle period less the transmission duration of the expected message.

24. The system of claim 22, wherein the microprocessor is configured to turn on the radio receiver for a limited time to look for an expected message from each transmission source of the plurality of transmission sources.

25. The system of claim 24, wherein the microprocessor is configured to synchronize to the transmission source of the plurality of transmission sources that has the strongest signal.

26. A method for maintaining synchronization with a periodic transmission from one of a plurality of transmission sources while achieving low power battery operation of a vehicle locating unit in a stolen vehicle recovery system, the periodic transmission occurring during a transmission cycle period and including an expected message that has a transmission duration, the method comprising:

using a selectively-actuatable radio receiver of the vehicle locating unit, receiving during periods of actuation the periodic transmissions from the one of a plurality of transmission sources;

using a microprocessor of the vehicle locating unit, looking for a synchronization symbol in the expected message and synchronizing subsequent actuation of the radio receiver using the synchronization symbol;

reacquiring a warm start synchronization if synchronization is lost; and

acquiring a cold start synchronization if the warm start synchronization fails to reacquire synchronization.

27. The method of claim 26, wherein reacquiring warm start synchronization includes re-checking for synchronization a predetermined number of times;

and, if synchronization is not detected, looking for a synchronization symbol after waiting for a length of time.

28. The method of claim 27, wherein acquiring the cold start synchronization begins if synchronization is not detected after rechecking for the predetermined number of times.

29. The method of claim 27, wherein warm start synchronization fails to reacquire synchronization if, after the predetermined number of times, loss of synchronization remains.

30. The method of claim 27, wherein the length of time is equal to a difference between the cycle period of the transmissions less a transmission duration of the expected message.

31. The method of claim 26, wherein acquiring cold start synchronization includes:

turning on the radio receiver for a limited time to look for the expected message; and

if the expected message is detected, waiting for a length of time before turning on the radio receiver to synchronize;

otherwise, if the expected message is not detected, repeatedly turning off the radio receiver for a time asynchronous with the transmission cycle period and turning it on again until the expected message is detected.

32. The method of claim 31, wherein the length of time is equal to the difference between the transmission cycle period less the transmission duration of the expected message.

33. The method of claim 31, wherein turning on the radio receiver comprises turning on the radio receiver for a limited time to look for an expected message from each transmission source of the plurality of transmission sources.

34. The method of claim 31 further comprising synchronizing to the transmission source of the plurality of transmission sources that has the strongest signal.