DUAL BANDWIDTH TIME DIFFERENCE OF ARRIVAL (TDOA) SYSTEM

• US 20080186231A1
• Filed: 02/04/2008
• Published: 08/07/2008
• Est. Priority Date: 02/05/2007
• Status: Active Grant

• Current Assignee: Aeroscout Limited (Stanley Black & Decker, Inc.)
• Original Assignee: Aeroscout Limited (Stanley Black & Decker, Inc.)
• Inventors: Aljadeff, Daniel, Shamir, Adi, Lavi, Amir, Amsalem, Reuven
• Granted Patent: US 8,208,939 B2
• Time in Patent Office: Days
• US Class Current: 342/387
• CPC Class Codes: G01S 5/0258 by combining or switching between measurements derived from different systems
• 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

Abstract

A wireless location system has at least one wireless tag to be located by the wireless location system, wherein the at least one wireless tag transmits two wireless signals having a known time relationship and having different bandwidths. A plurality of receivers is provided wherein a first receiver receives and processes a first of the two wireless signals and estimates a time to arrive (TOA) of the first wireless signal, and a second receiver receives and processes a second of the two wireless signals and estimates a TOA of the second wireless signal at the second transceiver. The plurality of receivers is time synchronized based on a common timing signal. A location server is coupled to each of the plurality of receivers. The location server receives the TOA of the first wireless signal from the first receiver and the TOA of the second wireless signal from the second receiver. The location server calculating a TDOA of the two wireless signals and estimates a position of the at least one wireless tag based on the TDOA

Claims

1. A wireless location system comprising:

at least one wireless transmitter unit to be located by said wireless location system, wherein the at least one wireless transmitter unit transmits two wireless signals having a known time relationship and having different bandwidths;

a plurality of receivers, wherein a first receiver receives and processes a first of the two wireless signals and estimates a time to arrive (TOA) of the first wireless signal, and a second receiver receives and processes a second of the two wireless signals and estimates a TOA of the second wireless signal at the second receiver, wherein the plurality of receivers is time synchronized based on a common timing signal; and

a location server coupled to each of the plurality of receivers, the location server receiving the TOA of the first wireless signal from the first receiver and the TOA of the second wireless signal from the second receiver, the location server calculating a TDOA of the two wireless signals and estimating a position of the at least one wireless transmitter unit based on the TDOA.

2. A location system in accordance with claim 1, wherein the two wireless signals having different bandwidth comprises:

an UWB signal; and

a narrower band signal;

wherein the UWB signal and the narrow band signal are both transmitted with a known time relationship between the UWB signal and the narrow band signal.

3. A location system in accordance with claim 2 wherein at least one of the plurality of receivers comprises:

means for receiving and processing each of said two wireless signals transmitted;

means for estimating the time to arrive (TOA) of each of said two wireless signals trasmitted at said receiver, wherein said TOA of each of said two wireless signals is referenced to synchronized time counters;

said second receiver selecting an earliest TOA of said received signals;

wherein said location server coupled to each of the plurality of receivers, the location server receiving the TOA of the first wireless signal from the first receiver and the selected TOA of the second wireless signal from the second receiver, the location server calculating a TDOA of the two wireless signals and estimating a position of the at least one wireless transmitter unit based on the TDOA.

4. A wireless transmitter unit according to claim 3, wherein the UWB signal carries no data and the narrower band signal carries transmitter data.

5. A location system in accordance with claim 1, wherein the location server estimates a position of the at least one wireless tag based on multiple TDOA calculations.

6. A location system in accordance with claim 2, wherein the TDOA comprising at least one TDOA value calculated from the difference of one TOA estimated on the transmitted UWB signal and a second TOA estimated on the transmitted narrower band signal.

7. A location system according to claim 5, wherein the common timing signal to time synchronize the plurality of receivers is a wireless signal.

8. A location system according to claim 1, wherein at least one receiver is a transceiver and transmits the common timing signal.

9. A location system according to claim 1, wherein at least one wireless tag at a known position transmits the common timing signal used to time synchronize the plurality of receivers.

10. A location system according to claim 1, wherein the location server assigns a quality factor to each reported TOA by the plurality of receivers, wherein the estimated position of the wireless tag is based on the assigned quality factors.

11. A wireless location system in accordance with claim 1 wherein said at least one wireless transmitter is a wireless tag comprising:

a first signal transmitter having a first signal antenna;

a second signal transmitter having a second signal antenna; and

a controller coupled to the first signal transmitter and the second signal transmitter.

12. A wireless location system in accordance with claim 11 wherein the wireless tag further comprises:

a second signal receiver;

a switching unit coupled to the second signal transmitter, and the second signal receiver;

wherein the controller is coupled to the first signal transmitter, the second signal transmitter, and the second signal receiver.

13. A wireless location system in accordance with claim 12 wherein the second signal antenna is coupled to the switching unit.

14. A wireless location system in accordance with claim 1 wherein at least one of the plurality of receivers comprises:

a first receiver signal receiver;

a second receiver signal receiver;

a first TOA circuit coupled to the first signal receiver to calculate the TOA of the first signal; and

a controller coupled to the first TOA circuit, the second signal receiver and means for processing the second signal, the controller calculating the TOA of the second signal;

wherein the TOA of the first and second signals are referenced to synchronized time counters.

15. A wireless location system in accordance with claim 1 wherein at least one of the plurality of receivers are transceivers comprising:

a first signal transceiver receiver;

a second signal transceiver transmitter;

a second signal transceiver receiver;

a first TOA circuit coupled to the first signal transceiver receiver to calculate the TOA of the first signal;

a controller coupled to the first TOA circuit, the second signal transceiver transmitter, and the second signal transceiver receiver and means for processing the second signal, the controller calculating the TOA of the second signal; and

a switching unit coupled to the second signal transceiver transmitter, and the second signal transceiver receiver;

a first signal transceiver antenna coupled to the first signal transceiver receiver; and

a second signal transceiver antenna coupled to the switching unit;

wherein the TOA of the first and second signals is referenced to synchronized time counters.

36. A wireless location system in accordance with claim 3, wherein the wherein said TOA of each of said two wireless signals is referenced to a single time counter.

16. A method for estimating a time of arrival (TOA) of a wireless transmission at a wireless receiver, comprising:

transmitting an UWB signal and a narrower band signal from a single wireless device, the UWB signal and a narrower band signal having a known time relationship;

receiving the UWB signal and the narrower band signal at a receiver unit, the receiver unit processing the UWB signal and a narrower band signal and estimating the time of arrival (TOA) of the UWB signal and the TOA of the narrower band signal at said receiver unit, said TOAs of said received signals being referenced to synchronized time counters; and

selecting an earliest TOA between the TOA of the UWB signal and the TOA of the narrower band signal.

17. A method according to claim 16, further comprising estimating a quality of the estimated TOA values.

18. A method according to claim 16, wherein the earliest TOA is reported to a location server coupled to the receiver unit.

19. A method according to claim 18, wherein the TOA of a non-selected signal is also reported by the receiver unit.

20. A method according to claim 17, further comprising correcting the TOA of the narrow band signal by using the TOA of the UWB signal.

21. A method for calculating a time difference of arrival (TDOA) of a wireless transmission at a plurality of wireless receivers, comprising:

transmitting two wireless signals having different bandwidths and a known time relationship by a single wireless device;

receiving and processing a first of the two wireless signals and estimating a time of arrival (TOA) of a first of the two wireless signals by a first receiver;

receiving and processing a second of the two wireless signals and estimating the TOA of a second of the two wireless signals by a second receiver;

transmitting the TOA of the first wireless signal by the first receiver and the TOA of the second wireless signal by the second receiver to a common location server; and

calculating the TDOA of the two wireless signals from a difference of the TOA of the first signal and the second TOA of the second signal;

wherein said first and second receivers are time synchronized by a common timing signal.

22. A method for calculating a time difference of arrival (TDOA) of a wireless transmission at a plurality of wireless receivers in accordance with claim 21 wherein transmitting two wireless signals having different bandwidths comprises:

transmitting an UWB signal; and

transmitting a narrower band signal;

wherein the UWB signal and the narrow band signal are both transmitted with a known time relationship between the UWB signal and the narrow band signal.

23. A receiver unit for receiving and processing two different wireless signals comprising:

means for receiving the two different wireless signals; and

means for estimating a time to arrive (TOA) of each of the two different wireless signals at said receiver, said TOA of each of the two different wireless signals being referenced to synchronized time counters;

wherein the wireless signals comprising an UWB signal and a narrower band signal, both being transmitted with a known time relationship.

24. A receiver unit according to claim 23, wherein said means for receiving further comprises an antenna diversity receiver having two antennas.

25. A receiver unit according to claim 24, wherein said means for estimating further comprises estimating the TOA of said narrower band signal at the receiver unit from the two antennas.

26. A receiver unit according to claim 23, wherein the receiver unit is a transceiver unit further comprising a wireless transmitter.

27. A receiver unit according to claim 23, wherein said receiver is integrated into a WLAN access point unit.

28. A receiver unit according to claim 23, wherein said narrower band signal is an IEEE 802.11a/b/g/n signal.

29. A receiver unit according to claim 23, wherein said means for receiving activates signal detection during time windows synchronized to the received narrower band signal.

30. A wireless transmitter unit comprising:

means for transmitting two wireless signals having different bandwidths;

wherein said two wireless signals comprise an UWB signal and a narrower band signal, wherein the two wireless signals are transmitted with a known time relationship.

31. A wireless transmitter unit according to claim 30, wherein the wireless transmitter is a wireless tag.

32. A wireless transmitter unit according to claim 30, wherein the narrower band signal is an IEEE 802.11a/b/g/n signal.

33. A wireless transmitter unit according to claim 30, wherein the UWB signal carries no data and the narrower band signal carries transmitter data.

34. A wireless transmitter unit according to claim 30, further comprising a CCA mechanism to prevent transmission collision of the narrower band signal.

35. A wireless transmitter unit according to claim 30, wherein UWB pulses are transmitted at the edge of the narrower band signal symbol clock.