METHOD AND APPARATUS FOR LOCATIONING AN OBJECT IN A COMMUNICATION NETWORK

• US 20100118858A1
• Filed: 11/13/2008
• Published: 05/13/2010
• Est. Priority Date: 11/13/2008
• Status: Active Grant

• Current Assignee: Symbol Technologies, LLC (Zebra Technologies Corporation)
• Original Assignee: Symbol Technologies, Inc. (Zebra Technologies Corporation)
• Inventors: PISHARODY, Mohan
• Granted Patent: US 8,121,110 B2
• Time in Patent Office: Days
• US Class Current: 370/349
• CPC Class Codes: G01S 5/021 Calibration, monitoring or correction G01S5/0252 takes precedence
• CPC Class Codes: G01S 5/02216 Timing or synchronisation of the receivers
• CPC Class Codes: G01S 5/06 Position of source determined by co-ordinating a plurality of position lines defined by path-difference measurements G01S5/12 takes precedence
• CPC Class Codes: H04W 56/0075 based on arrival time vs. expected arrival time

Abstract

A method and apparatus for locationing an object in a communication network. The method includes transmitting by a wireless transceiver fixed to the object of unknown location a plurality of radio frequency (RF) packets to a plurality of locationing receivers (LRs) in the communication network. The method further includes determining by each locationing receiver the local time of arrival of the RF packet and places a time stamp on the received RF packet based on a corresponding local clock, wherein the local clocks of the locationing receivers are synchronized based on a plurality of RF beacon packets transmitted by at least one reference transmitter at a known location.

Claims

1. A method for locationing an object in a communication network, the method comprising:

transmitting by a wireless transceiver fixed to the object of unknown location, a radio frequency (RF) packet, to a plurality of locationing receivers in the communication network;

determining by each of the plurality of locationing receivers, the local time of arrival of the RF packet; and

placing, by each of the plurality of locationing receivers, a time stamp on the received RF packet based on a local clock of each of the plurality of locationing receivers, wherein the local clocks of the plurality of locationing receivers are synchronized based on a plurality of RF beacon packets transmitted by at least one reference transmitter at a known location.

2. The method of claim 1 further comprising:

communicating periodically by each of the plurality of locationing receivers to an infrastructure device a list of time stamped RF packets received by the locationing receivers.

3. The method of claim 1, wherein each time stamped RF packet and each time stamped RF beacon packet further includes a packet identifier number for using by the infrastructure device to uniquely correlate each RF packet and beacon packet as received by each of the plurality of locationing receivers.

4. The method of claim 1, wherein the plurality of RF beacon packets are transmitted during specific time intervals, to the plurality of locationing receivers.

5. The method of claim 4, wherein the time interval is shorter than a minimal time interval necessary for correcting the drift time of the local clocks in the locationing receivers.

6. The method of claim 4 further comprising:

communicating periodically by each of the plurality of locationing receivers to an infrastructure device a list of time stamped RF beacon packets received by the locationing receivers.

7. The method of claim 1, wherein the plurality of locationing receivers are at known locations.

8. A method for locationing an object with an infrastructure device having communication links with a plurality of locationing receivers, the method comprising:

receiving from the plurality of locationing receivers a list of time stamped RF packets, wherein a time stamped RF packet received from a given locationing receiver includes the time of arrival of an RF packet at the given locationing receiver, from a wireless transceiver fixed on the object of unknown location; and

correlating the timing information of each RF packet across all locationing receivers; and

determining the spatial location of the object based on a differential time-of-arrival triangulation method.

9. The method of claim 8, wherein the correlating the timing information of each RF packet across all locationing receivers further includes:

synchronizing the local clocks of the plurality of locationing receivers based on a cross calibration with at least one reference transmitter at a known location.

10. The method of claim 9, wherein the synchronizing of the local clocks of the plurality of locationing receivers further comprising:

correlating the local arrival times of each RF beacon packet at each of the locationing receivers based on the known spatial locations of the at least one reference transmitter and locationing receivers; and

interpolating the correlation among the plurality of local clocks between the arrival of successive RF beacon packets.

11. The method of claim 10, wherein the interpolating the correlation among the plurality of local clocks comprises:

linearly interpolating the correlation among the plurality of local clocks between the arrival of successive RF beacon packets.

12. The method of claim 10, wherein each R-F beacon packet further includes a packet identifier number.

13. A device operable for locationing an object in a communication network, the device comprising:

an antenna;

a receiver, coupled to the antenna, configured to

receive from a wireless transceiver fixed to the object, periodically, a plurality of RF packets;

receive from a reference transmitter fixed to a reference object, periodically, a plurality of beacon signals; and

calibrate timing information present in the plurality of beacon signals.

14. The device of claim 13, wherein the receiver is further configured to receive a plurality of RF packets from a plurality of locationing receivers.

15. The device of claim 13, wherein the receiver is further configured to receive a plurality of beacon signals from a plurality of locationing receivers.

16. The device of claim 13 further comprising:

a local clock to provide timing information.

17. The device of claim 16, wherein the receiver is further configured to place a time stamp on the plurality of RF packets based on the local clock.