Interference suppression for wireless local area network and location system

• US 20020086640A1
• Filed: 12/28/2001
• Published: 07/04/2002
• Est. Priority Date: 12/29/2000
• Status: Active Grant

• Current Assignee: Zebra Technologies Corporation
• Original Assignee: Wherenet Corporation (Zebra Technologies Corporation)
• Inventors: Belcher, Donald K., Boyd, Robert W., Wohl, Michael A.
• Granted Patent: US 6,892,054 B2
• Time in Patent Office: Days
• US Class Current: 455/67.16
• CPC Class Codes: G01S 5/0218 Multipath in signal reception
• CPC Class Codes: H04B 7/086 using weights depending on external parameters, e.g. direction of arrival [DOA], predetermined weights or beamforming
• CPC Class Codes: H04W 64/00 Locating users or terminals or network equipment for network management purposes, e.g. mobility management
• CPC Class Codes: H04W 84/12 WLAN [Wireless Local Area Networks]
• CPC Class Codes: H04W 88/08 Access point devices

Abstract

A wireless local area network and location system for locating objects within a monitored environment are disclosed. A plurality of access point stations receive and transmit communication signals within a wireless local area network. A processor is operatively connected to each of the access point stations and operative for processing communication signals received from the mobile station and, in one embodiment, determining which communication signals are first-to-arrive signals and conducting differentiation of the first-to-arrive signals to locate a mobile station. Delayed versions of at least one interference signal are weighted and the amplitude and phase controlled with weighted functions W₁, W₂. . . W_n. The resultant weighted replicas are summed to determine an approximation of disbursed interference for cancelling interference. The location system can include a tag transmitter and spaced monitoring receivers and processor.

Claims

1. A wireless local area network system comprising:

a plurality of access point stations that receive and transmit communication signals within a wireless local area network;

a mobile station in communication with a plurality of access point stations;

a processor operatively connected to each of the access point stations and operative for processing communication signals received from the mobile station and determining which communication signals are first-to-arrive signals and conducting differentiation of the first-to-arrive signals to locate a mobile station and weighting delayed versions of at least one interference signal by controlling amplitude and phase with weighted functions W₁, W₂. . . W_n and summing any resultant weighted replicas to determine an approximation of the dispersed interference for cancelling interference.

2. A wireless local area network system according to claim 1, and further comprising an interference detector and controller circuit that provide a control loop for minimizing interference.

3. A wireless local area network system according to claim 1, and further comprising a system antenna and an interference receiving antenna directed for receiving an interference signal.

4. A wireless local area network system according to claim 3, and further comprising two system antennas spaced in diversity.

5. A wireless local area network system according to claim 1, and further comprising a processor positioned at each access point station for determining first-to-arrive signals and a location processor that receives any determined first-to-arrive signals from each access point station and conducts differentiation of said first-to-arrive signals.

6. A wireless local area network according to claim 1, wherein said mobile station comprises a mobile access point station that receives and transmits communication signals within the wireless local area network.

7. A wireless local area network according to claim 1, wherein said mobile station comprises a mobile device in communication with an access point station.

8. A wireless local area network according to claim 7, wherein said mobile device comprises a tag transmitter associated with an object.

9. A wireless local area network according to claim 1, wherein a processor is operative for determining first-to-arrive signals based on a common timing signal.

10. A wireless local area network system comprising:

a plurality of access point stations that receive and transmit communication signals within the wireless local area network, said access point stations further comprising a system antenna and an interference receiving antenna directed for receiving an interference signal;

a mobile station in communication with a plurality of access point stations;

a processor operatively connected to each access point station for processing communication signals received from the mobile station and determining which communication signals are first-to-arrive signals and conducting differentiation of first-to-arrive signals to locate a mobile station;

a tapped delay line, summer, controller, and interference detector circuit operatively connected to said system and interference receiving antenna for weighting delayed versions of at least one interference signal by controlling amplitude and phase with weighting functions W₁, W₂. . . W_n and summing any resultant weighted replicas to determine an approximation of the dispersed interference for cancelling interference.

11. A wireless local area network system according to claim 10, and further comprising two system antennas spaced in diversity.

12. A wireless local area network system according to claim 10, and further comprising a processor positioned at each access point station for determining first-to-arrive signals and a processor that receives any determined first-to-arrive signals from each access point station and conducting differentiation of said first-to-arrive signals.

13. A wireless local area network according to claim 10, wherein said mobile station comprises a mobile access point station that receives and transmits communication signals within the wireless local area network.

14. A wireless local area network according to claim 10, wherein said mobile station comprises a mobile device in communication with an access point station.

15. A wireless local area network according to claim 14, wherein said mobile device comprises a tag transmitter associated with an object.

16. A wireless local area network according to claim 10, wherein a processor is operative for determining first-to-arrive signals based on a common timing signal.

18. A location system according to claim 17, wherein a processor is operative for determining which signals are first-to-arrive signals based on a common timing signal.

19. A location system according to claim 17, and further comprising an interference detector and controller circuit that provide a control loop for minimizing interference.

20. A location system according to claim 17, and further comprising a system antenna and an interference receiving antenna directed for receiving an interference signal.

21. A location system according to claim 20, and further comprising two system antennas spaced in diversity.

22. A location system according to claim 17, and further comprising a processor positioned at each monitoring receiver for determining first-to-arrive signals and a location processor that receives any determined first-to-arrive signals from each monitoring receiver and conducting differentiation of said first-to-arrive signals.

24. A location system according to claim 23, wherein a processor is operative for determining which signals are first-to-arrive signals based on a common timing signal.

25. A location system according to claim 23, and further comprising two system antennas spaced in diversity.

26. A location system according to claim 23, and further comprising a processor positioned at each monitoring receiver for determining first-to-arrive signals and a location processor that receives any determined first-to-arrive signals from each access point station and conducting differentiation of said first-to-arrive signals.

28. A wireless local area network system according to claim 27, and further comprising an interference detector and controller circuit that provide a control loop for minimizing the total amount of interference.

29. A wireless local area network system according to claim 27, and further comprising a system antenna and an interference receiving antenna directed for receiving an interference signal.

30. A wireless local area network system according to claim 29, and further comprising two system antennas spaced in diversity.

31. A wireless local area network according to claim 27, wherein said mobile station comprises a mobile access point station that receives and transmits communication signals within the wireless local area network.

32. A wireless local area network according to claim 27, wherein said mobile station comprises a mobile device in communication with an access point station.

33. A wireless local area network according to claim 27, wherein said mobile device comprises a tag transmitter associated with an object.

35. A wireless local area network system according to claim 34, and further comprising two system antennas spaced in diversity.

17. A location system for locating objects within a monitored environment comprising:

a tag transmitter associated with each object within the monitored environment and operative to transmit a signal encoded with information representative of the identification of the object;

a plurality of spaced monitoring receivers for receiving signals from tag transmitters; and

a processor operative with each of said monitoring receivers for receiving and processing signals received from tag transmitters for determining which signals are first-to-arrive signals and conducting differentiation of the first-to-arrive signals to locate an object and associated tag and weighting delayed versions of at least one interference signal by controlling amplitude and phase with weighting functions W₁, W₂. . . W_n and summing any resultant weighted replicas to determine an approximation of the dispersed interference for cancelling interference.

23. A location system for locating objects within a monitored environment comprising:

a tag transmitter associated with each object within the monitored environment and operative to transmit a signal encoded with information representative of the identification of the object;

a plurality of spaced monitoring receivers for receiving signals from tag transmitters and each including a system antenna and interference receiving antenna;

a processor operative with each of said spaced monitoring receivers for receiving and processing signals received from tag transmitters for determining which signals are first-to-arrive signals and conducting differentiation of the first-to-arrive signals to locate an object and associated tag; and

a tapped delay line, summer, controller and interference detector circuit operatively connected to said system antenna and interference receiving antenna for weighting delayed versions of at least one interference signal by controlling amplitude and phase with weighting functions W₁, W₂. . . W_n and summing any resultant weighted replicas to determine an approximation of the dispersed interference for cancelling interference.

27. A wireless local area network system comprising:

a plurality of access point stations that receive and transmit communication signals within a wireless local area network;

a processor operatively connected to each of the access point stations and operative for processing communication signals received from a mobile station in communication therewith and weighting delayed versions of at least one interference signal by controlling amplitude and phase with weighted functions W₁, W₂. . . W_n and summing any resultant weighted replicas to determine an approximation of the dispersed interference for cancelling interference.

34. A wireless local area network system comprising:

a plurality of access point stations that receive and transmit communication signals within the wireless local area network from a mobile station in communication therewith;

said access point stations further comprising a system antenna and an interference receiving antenna directed for receiving an interference signal;

a tapped delay line, summer, controller and interference detector circuit operatively connected to said system and interference receiving antenna for weighting delayed versions of at least one interference signal by controlling amplitude and phase with weighting functions W₁, W₂. . . W_n and summing any resultant weighted replicas to determine an approximation of the dispersed interference for cancelling interference.