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

• US 7,558,852 B2
• Filed: 08/21/2007
• Issued: 07/07/2009
• 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: Rebo, Richard D., Bilstad, Arnold M., Deng, John Z., Leary, Jonathan S., Douglas, Bretton Lee, Olson, Timothy S., Kaiser, Daryl A., Halasz, David E., Yang, Sheausong
• Primary Examiner(s): NGUYEN, PHUOC H
• Application Number:
  US11/842,549
• Publication Number:
  US 20070281714A1
• Time in Patent Office: 686 Days
• Field of Search: 709223-236, 455/404.2, 455/456.1
• US Class Current: 709/224
• 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 operating a processing system, comprising:

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

determining the location of at least one of the wireless client stations or radio tags from the received path loss information using a path-loss based location determining method,

wherein the radio tag or client station uses a common infrastructure for transmitting a location frame, the common intrastrcuture configured for radiolocation by path loss measurement and 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,

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

one or both;

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,

and/or

wherein a location frame conforming to the pre-defined frame structure is configured to be receivable by one or more substantially standard wireless stations of a substantially standard IEEE 802.11 wireless local area network, and 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.

2. A method as recited in claim 1, wherein the common infrastructure includes a defined 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 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.

5. A method as recited in claim 4, wherein the substantially standard wireless local area network is an IEEE 802.11 wireless local area network, and 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.

6. A method as recited in claim 4, wherein the substantially standard wireless stations are access points of the wireless local area network.

7. A method as recited in claim 4, 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.

8. A method as recited in claim 4, wherein the set of receiving stations are access points at known locations, 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 access points;

providing an array of grid points in the selected region;

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

using the expected path loss from each selected access point 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.

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

10. A method as recited in claim 1, wherein the radio tag or client is settable to transmit frames from time to time, the 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.

11. A method as recited in claim 10, 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.

12. 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, 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.

13. A method as recited in claim 12,

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

wherein the method further comprises:

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.

14. A method as recited in claim 13, 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.

15. A method as recited in claim 13, 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.

16. A method as recited in claim 13,

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.

17. A method comprising:

receiving information at a plurality of stations of a wireless network using a pre-defined protocol, the information in location frames having a pre-defined frame structure and transmitted by one or more transmitters, each transmitter in a radio tag or client station of the wireless network;

using path loss information from the location frames to determine the location of the one or more transmitting transmitters,

wherein the pre-defined protocol is part of a common infrastructure for radio tags and client stations of the wireless network to be located using radiolocation by path loss measurement,

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,

and/or

wherein a location frame conforming to the pre-defined frame structure is configured to be receivable by one or more substantially standard wireless stations of a substantially standard IEEE 802.11 wireless local area network, and 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.

18. A method as recited in claim 17, wherein the common infrastructure includes a pre-defined protocol for radio tags to transmit information with relatively low power consumption compared to transmitting normal payload carrying frames.

19. A method as recited in claim 17, 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.

20. A method as recited in claim 17, wherein the pre-defined frame structure for location frames includes an indication of the transmit power used to transmit the location frame.

21. A method comprising:

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, 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,

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 IEEE 802.11 wireless local area network, and

the pre-defined frame structure for location frames is defined by one or more extensions to the IEEE 802.11 specifications that provide pre-defined frame structure for client stations and radio tags,

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.

22. A method as recited in claim 21, 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.

23. 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 includes an identifier that provides for a receiving station to recognize the frame as a frame that includes location information and includes an indication of the transmit power, such that the location frame conveys information usable 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, and

one or both;

wherein the transmitting of location frames is according to a pre-defined protocol common for both radio tags and client stations, the pre-defined protocol includes a pre-assigned multicast address to be used by transmitting radio tags and client stations to transmit location frame,

and/or

wherein a location frame conforming to the pre-defined frame structure is configured to be receivable by one or more substantially standard wireless stations of a substantially standard IEEE 802.11 wireless local area network, and the pre-defined frame structure for location frames is defined by one or more extensions to the IEEE 802.11 specifications that provide pre-defined frame structure for client stations and radio tags.