Tag location,client location, and coverage hole location in a wireless network

• US 20060075131A1
• Filed: 11/22/2005
• Published: 04/06/2006
• Est. Priority Date: 07/28/2003
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Douglas, Bretton Lee, Olson, Timothy S., Kaiser, Daryl A., Halasz, David E., Rebo, Richard D., Bilstad, Arnold M., Yang, Sheausong, Deng, John Z., Leary, Jonathan S.
• Granted Patent: US 7,293,088 B2
• Time in Patent Office: Days
• US Class Current: 709/230
• CPC Class Codes: H04W 48/08 Access restriction or access information delivery, e.g. discovery data delivery signalling during connection H04W76/00
• CPC Class Codes: H04W 48/16 Discovering, processing access restriction or access information
• 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 80/00 Wireless network protocols or protocol adaptations to wireless operation

Abstract

Determining the location of a radio tag or client station of a wireless network, and the location of coverage holes by receiving from a plurality of wireless stations of the wireless network path loss information of the path loss of one or more location frames received at the respective wireless stations. The location frames transmitted by the radio tag or client station having a pre-defined frame structure. The radio tags and client stations use a common infrastructure for transmitting a location frame configured for radiolocation by path loss measurement. The common infrastructure includes a pre-defined protocol common for both radio tags and client stations for transmitting information for reception by the plurality of stations of the wireless network for radiolocation. The pre-defined protocol includes using the location frame having the pre-defined frame structure.

Claims

1. A method of determining location of a radio tag or client station of a wireless network, the method comprising:

receiving from a plurality of wireless stations of the wireless network path loss information of the path loss of one or more location frames received at the respective wireless stations, the location frames transmitted by the radio tag or client station and having a pre-defined frame structure; and

determining the location of the wireless station or radio tag from the path loss information,

wherein the radio tag or client station uses for transmitting a location frame, a common infrastructure configured for radiolocation by path loss measurement, the common infrastructure including a pre-defined protocol common for both radio tags and client stations for transmitting information for reception by the plurality of stations of the wireless network for radiolocation, the pre-defined protocol including using the location frame having the pre-defined frame structure.

2. A method as recited in claim 1, wherein the common infrastructure includes a defining a protocol for radio tags to transmit information with relatively low power consumption compared to transmitting normal payload carrying frames.

3. A method as recited in claim 1, wherein the pre-defined protocol includes a pre-assigned multicast address to be used by transmitting radio tags and client stations to transmit location frames.

4. A method as recited in claim 3, wherein a location frame conforming to the pre-defined frame structure includes an identifier that provides for a receiving station to recognize the frame as a frame that includes location information, and wherein the identifier includes the multicast address.

5. A method as recited in claim 1, wherein the location frames having a pre-defined frame structure are configured to be receivable by one or more substantially standard wireless stations of a substantially standard wireless local area network (“

WLAN”

).

6. A method as recited in claim 5 wherein the WLAN substantially conforms to the IEEE 802.11 standard or variants thereof.

7. A method as recited in claim 6, wherein the predefined protocol includes one or more extensions to the IEEE 802.11 specifications that provide for client stations and radio tags the pre-defined frame structure for location frames, including an indication of the transmit power used to transmit the location frame.

8. A method as recited in claim 5, wherein the plurality of wireless stations are access points of the WLAN, the access points having the ability to measure the received signal power of received signal to a pre-defined level of accuracy, and wherein the location frame transmitted by the radio tag or clients includes an indication of transmit power, such that the path loss from the transmitting radio tag or client to any receiving access point is available at the access point.

9. A method as recited in claim 5, wherein the radio tag or client station transmitting the one or more location frames includes a transmitter with transmit power calibrated to relative high accuracy.

10. A method as recited in claim 1, wherein the radio tag or client does not need to associate or to be associated with an AP in order to transmit a location frame conforming to the pre-defined frame structure.

11. A method as recited in claim 1, wherein a location frame conforming to the pre-defined frame structure includes an identifier that provides for a receiving station to recognize the frame as a frame that includes location information.

12. A method as recited in claim 11, wherein the identifier includes a multicast address.

13. A method as recited in claim 1, wherein the radio tag or client is settable to periodically transmit frames conforming to the pre-defined frame format on a single channel, or periodically transmit on a number of channels in succession to a pre-assigned multicast address, the setting including setting one or more of a set of parameters for the transmitting by the radio tag or client, the set of parameters consisting of the single transmission channel or channels for transmitting, a transmit power or powers, one or more intervals between transmissions, and a length or lengths of time of transmissions.

14. A method as recited in claim 13, wherein the setting of the radio tag or client uses software, such that legacy clients that are software upgradable can be upgraded to be able to conform to the infrastructure.

15. A method as recited in claim 13, wherein the setting of the radio tag or client uses a wired mechanism for setting the one or more parameters.

16. A method as recited in claim 13, wherein the setting of the radio tag or client uses a mechanism for wirelessly setting the one or more parameters.

17. A method as recited in claim 5, wherein a plurality of the receiving stations are access points of the wireless network, wherein each receiving access point is at a known location and is able to listen for beacons and probe responses from other access points, wherein a plurality of receiving access points sending and receiving beacons or probe responses between each other provide for access point-to-access point calibration, such calibration usable in the location determining.

18. A method as recited in claim 5, wherein the set of receiving stations at known locations are access points, and wherein the location determining further includes:

providing a propagation model for the selected region to provide a mapping of distance and path loss between pairs of selected access points, the propagation model including a mapping of distance and path loss between pairs of APs;

providing an array of grid points in the selected region;

using the propagation model to provide an expected path loss from each selected AP to each grid point; and

using the expected path loss from each selected AP to each grid point and the provided path loss measurement information to determine a likely location in the selected region of a radio tag or client station that transmitted location frames.

19. A method as recited in claim 18 further comprising, calibrating access point-to-access point path losses for the selected APs using AP-to-AP measurements;

and correcting the expected path loss from each selected AP to each grid point to provide a corrected coverage model.

20. A method as recited in claim 18, wherein the location determining further includes:

determining whether or not the provided path loss measurement information exceeds the capability of the method or system to measure so that measurements that are determined not to be of sufficient accuracy are discardable.

21. A method as recited in claim 1, wherein the location frames having a pre-defined frame structure are configured to be receivable by one or more substantially standard wireless stations of a substantially standard wireless local area network (“

WLAN”

), and wherein the plurality of receiving stations are access points of the wireless network, and wherein the common infrastructure is also for determining gaps in the coverage area of the access points of the wireless network without requiring a map.

22. A method as recited in claim 21,

wherein the pre-defined protocol provides a mechanism to set a radio tag or client to periodically transmit frames conforming to the pre-defined frame format on a single channel, or periodically transmit on a number of channels in succession to a pre-assigned multicast address, the protocol providing a set of parameters for the transmitting by the radio tag or client, including setting at least one parameter of the set consisting of the single transmission channel or channels for transmitting, a transmit power or powers, one or more intervals between transmissions, and a length or lengths of time of transmissions, and

the method further comprising:

determining the gaps in the coverage area including, at an entity of the wireless network;

setting up client stations and/or radio tags to transmit location frames at their respective maximum power;

receiving reports sent by one or more access points that receive the transmitted location frames, the reports including information about received location messages and further about from which clients and/or radio tags the communication was unreliable; and

determining the location of the client stations and/or radio tags that transmitted location frames and from which frames were received at one or more access points.

23. A method as recited in claim 22, wherein the setting up of client stations and/or radio tags to transmit location frames includes setting up the client stations and/or radio tags to transmit at their respective minimum data rate, and on the frequency channel expected to have the best propagations.

24. A method as recited in claim 22, further comprising:

ascertaining whether or not a particular client is in a coverage gap; and

in the case that it is ascertained that the particular client is in a coverage gap, ascertaining which access point is serving the client station, and instructing the ascertained access point to instruct the particular client station to transmit location-finding frames more frequently to provide for more frequent location determination for the particular client station.

25. A method as recited in claim 22,

ascertaining whether or not a particular client is at a coverage gap;

in the case that it is ascertained that the particular client is in a coverage gap, ascertaining which access point is serving the client station, and instructing the ascertained access point to instruct the particular client station to transmit location frames at the highest power and lowest data rate to provide for more accuracy in determining location.

26. A method as recited in claim 5, further comprising, when the location server determines that a particular client station is at or near a pre-defined location, ascertaining which access point is serving the client station, and instructing the ascertained access point to instruct the particular client station to transmit location-finding frames more frequently to provide for more frequent location determination for the particular client station.

27. A method as recited in claim 5, further comprising, when the location determining entity first determines the location of a particular client station, ascertaining which access point is serving the client station, and instructing the ascertained access point to instruct the particular client station to transmit location frames more frequently to provide for more frequent location determination for the particular client station.

28. A method as recited in claim 5, further comprising:

ascertaining whether or not a particular client is roaming relatively frequently,

in the case that it is ascertained that the particular client is roaming relatively frequently, ascertaining which access point is serving the client station, and instructing the ascertained access point to instruct the particular client station to transmit location-frames more frequently to provide for more frequent location determination for the particular client station.

29. A method comprising:

providing a common infrastructure for radio tags and client stations of a wireless network to be located using radiolocation by path loss measurement, wherein the common infrastructure includes a pre-defined protocol for radio tags and client stations to transmit information for reception by a plurality of stations of the wireless network, the pre-defined protocol including using frames that are location frames having a pre-defined frame structure.

30. A method as recited in claim 29, wherein the common infrastructure includes a defining a protocol for radio tags to transmit information with relatively low power consumption compared to transmitting normal payload carrying frames.

31. A method as recited in claim 29, wherein the location frames having a pre-defined frame structure are configured to be receivable by one or more substantially standard wireless stations of a substantially standard wireless local area network (“

WLAN”

).

32. A method as recited in claim 31 wherein the WLAN substantially conforms to the IEEE 802.11 standard or variants thereof.

33. A method as recited in claim 32, wherein the predefined protocol includes one or more extensions to the IEEE 802.11 specifications that provide for client stations and radio tags the pre-defined frame structure for location frames, including an indication of the transmit power used to transmit the location frame.

34. A method in a client station of a wireless station or a radio tag, the client station or radio tag including a transmitter of frames that conform to a wireless network standard, the method comprising:

transmitting location frames having a pre-defined frame structure and including information for reception by a plurality of stations of the wireless network, the location frames substantially conforming to frames of the wireless network standard,

wherein the predefined frame structure is designed for conveying information needed to locate radio tags and clients using path loss measurements,

such that the radio tags or client station can be located using radiolocation by path loss measurement between the radio tag or client station and the receiving stations.

35. A method as recited in claim 34, wherein the location frames are structured such that the transmitting by the radio tag or client station can be with relatively low power consumption compared to transmitting normal payload carrying frames.

36. A method as recited in claim 34, wherein the pre-defined protocol includes a pre-assigned multicast address to be used by transmitting radio tags and client stations to transmit location frames.

37. A method as recited in claim 36, wherein a location frame conforming to the pre-defined frame structure includes an identifier that provides for a receiving station to recognize the frame as a frame that includes location information, and wherein the identifier includes the multicast address.

38. A method as recited in claim 34, wherein the location frames having a pre-defined frame structure are configured to be receivable by one or more substantially standard wireless stations of a substantially standard wireless local area network (“

WLAN”

).

39. A method as recited in claim 38 wherein the WLAN substantially conforms to the IEEE 802.11 standard or variants thereof.

40. A method as recited in claim 39, wherein the predefined frame structure forms one or more extensions to the IEEE 802.11 specifications.

41. A method as recited in claim 38, wherein the locating includes receiving at one or more access points of the WLAN at least one location frame transmitted by the radio tag or client, the access points having the ability to measure the received signal power of received signal to a pre-defined level of accuracy, and wherein the location frame transmitted by the radio tag or clients includes an indication of transmit power, such that the path loss from the transmitting radio tag or client to any receiving access point is available at the access point.

42. A method as recited in claim 38, wherein the transmitter has transmit power calibrated to relative high accuracy.

43. A method as recited in claim 34, wherein the radio tag or client does not need to associate or to be associated with an AP in order to transmit a location frame conforming to the pre-defined frame structure.

44. A method as recited in claim 34, wherein a location frame conforming to the pre-defined frame structure includes an identifier that provides for a receiving station to recognize the frame as a frame that includes location information.

45. A method as recited in claim 44, wherein the identifier includes a multicast address.

46. A method as recited in claim 34, further comprising:

receiving setting instructions to set the radio tag or client to periodically transmit location frames, or periodically transmit on a number of channels in succession to a pre-assigned multicast address, the protocol providing a set of parameters for the transmitting by the radio tag or client, including setting at least one parameter of the set consisting of the single transmission channel or channels for transmitting, a transmit power or powers, one or more intervals between transmissions, and a length or lengths of time of transmissions.

47. A method as recited in claim 46, wherein the mechanism to set one or more parameters includes a mechanism wirelessly setting the one or more parameters.

48. A method as recited in claim 34, further comprising:

after the transmitting and as a result of not receiving any acknowledgment of the location-finding frame being received by a receiving station, re-transmitting the location frame at the highest power and lowest data rate to provide for more accuracy.

49. A method as recited in claim 34, further comprising:

after the transmitting and as a result of not receiving any acknowledgment of the location-finding frame being received by a receiving station, re-transmitting the location frame one or more times each at a progressively higher transmit power level until either the highest power is reached or an acknowledgment is received.

50. An apparatus for inclusion in a client station of a wireless station or in a radio tag, the apparatus comprising:

a transmitter configured to transmit frames that conform to a wireless network standard, and further configured to transmit location frames having a pre-defined frame structure and including information for reception by a plurality of stations of the wireless network, the location frames substantially conforming to frames of the wireless network standard,

wherein the predefined frame structure is designed for conveying information needed to locate radio tags and clients using path loss measurements,

such that the radio tag or client station can be located using radiolocation by path loss measurement between the radio tag or client station and the receiving stations.

51. An apparatus for inclusion in a client station of a wireless station or in a radio tag, the apparatus comprising:

means for transmitting frames that conform to a wireless network standard, and for transmitting location frames having a pre-defined frame structure and including information for reception by a plurality of stations of the wireless network, the location frames substantially conforming to frames of the wireless network standard,

wherein the predefined frame structure is designed for conveying information needed to locate radio tags and clients using path loss measurements,

such that the radio tags or client station can be located using radiolocation by path loss measurement between the radio tag or client station and the receiving stations.