Granted Patent B2

US 8,618,957 · App. 12/589,498 · Granted Dec 31, 2013

Abstract

Claims (29)

1. A vehicle locating unit with improved power management, the vehicle locating unit comprising:

a receiver for receiving an intermittent transmission from a communications source and having an assigned message frame, each transmission including at least one message frame having a data field and at least one auxiliary field; and

a power management system responsive to said receiver and configured to perform the following sequential steps:

(i) enter a wake mode corresponding to an expected start of the intermittent transmission,

(ii) enter a sleep mode until a start of a next intermittent transmission if the expected start of the intermittent transmission is not detected; otherwise, after detecting the expected start of the intermittent transmission, re-enter sleep mode and index to the receiver's assigned message frame in the intermittent transmission,

(iii) re-enter the wake mode after indexing,

(iv) match a pattern of bits of the at least one auxiliary field of the indexed message frame with a plurality of stored patterns of bits, each pattern of bits corresponding to a command to the vehicle locating unit, and

(v) return to the sleep mode if a mismatch is detected.

2. The vehicle locating unit of claim 1 in which there are a plurality of message frames in each transmission.

3. The vehicle locating unit of claim 1 in which there are one or more auxiliary fields in each message frame.

4. The vehicle locating unit of claim 1 in which said power management system includes a processor for controlling said wake and sleep modes.

5. The vehicle locating unit of claim 1 in which said power management system includes a memory for storing said plurality of patterns of bits expected for an auxiliary field.

6. An improved method of power management for a vehicle locating unit having a receiver, the method comprising:

assigning a message frame to the receiver;

receiving an intermittent transmission from a communication source, each transmission including at least one message frame having a data field and at least one auxiliary field;

entering a wake mode corresponding to an expected start of the intermittent transmission;

entering a sleep mode until a start of a next intermittent transmission if the expected start of the intermittent transmission is not detected; otherwise, after detecting the expected start of the intermittent transmission, re-entering sleep mode and indexing to the receiver's assigned message frame in the intermittent transmission;

reentering the wake mode after indexing to the assigned message frame in the intermittent transmission;

matching a pattern of bits of the at least one auxiliary field of the indexed frame with a plurality of stored patterns of bits, each pattern corresponding to a command to the vehicle locating unit; and

returning to the sleep mode if a mismatch is detected.

7. The improved method of power management of claim 6 in which there are a plurality of message frames in each transmission.

8. The improved method of power management of claim 6 in which there are one or more auxiliary fields in each message frame.

9. The vehicle locating unit of claim 1 further comprising:

a transmitter for transmitting reply codes;

wherein the periodic, intermittent transmission includes at least one of an activate command, a de-activate command, and a speed-up command, the receiver further adapted to wake up at a start of the periodic intermittent transmission; and

the power management system responsive to said receiver is configured to switch said transmitter from a de-activated state to a slow mode state upon receipt of an activate command, to switch said transmitter from said slow mode state to a second, slower, slow mode state after a predetermined period; and

upon receipt of a speed-up command to switch said transmitter from either of the slow mode state or second slow mode state to a fast mode state and to switch said transmitter from the fast mode state to said slow mode state after a predetermined period.

10. The vehicle locating unit of claim 9 in which said power management system is further configured to switch said transmitter from said second slow mode state to a third, slower, slow mode state after a preselected period, and to switch said transmitter from said third slow mode state to said fast mode state upon receipt of a speed-up command.

11. The vehicle locating unit of claim 10 in which said power management system is further configured to de-activate said transmitter from any of said mode states to a de-activated state upon receipt of a de-activate command.

Assignments (19)