METHODS AND APPARATUS FOR IMPROVED LOCATIONING IN A WIRELESS NETWORK

• US 20090005063A1
• Filed: 06/28/2007
• Published: 01/01/2009
• Est. Priority Date: 06/28/2007
• Status: Active Grant

• Current Assignee: Extreme Networks, Inc.
• Original Assignee: Symbol Technologies, Inc. (Zebra Technologies Corporation)
• Inventors: VANGATI, Mahender, LE, Vinh-Phuong, MALIK, Ajay
• Granted Patent: US 7,826,862 B2
• Time in Patent Office: Days
• US Class Current: 455/456.100
• CPC Class Codes: G01S 5/02527 Detecting or resolving anomalies in the radio frequency fingerprints of the radio-map
• CPC Class Codes: H04W 64/00 Locating users or terminals or network equipment for network management purposes, e.g. mobility management

Abstract

Methods and systems are provided for determining the location of a first wireless device (e.g., a mobile unit) within a wireless network comprising a second wireless device (e.g., an access point). The method includes determining a signal strength contour associated with RF communication between the access point and the mobile unit, and adding a correction factor to the signal strength contour to produce a corrected signal strength contour, wherein the correction factor includes the sums of the differences between the transmit power and the antenna gain associated with the mobile unit and the access point. In an alternate scheme involving stored fingerprint data, a correction factor is introduced based on the differences between antenna gains and transmit power associated with the mobile unit under consideration and the mobile unit used for generating the fingerprint data. The systems and methods disclosed herein are applicable, for example, to networks operating in accordance with 802.11, RFID, WiMax, WAN, Bluetooth, Zigbee, UWB, and the like.

Claims

1. A method for locating a first wireless device having a first type within a wireless network comprising a second wireless device having a second type, wherein each of the first and second wireless devices have respective antenna gains and transmit powers, comprising the steps of:

determining a signal strength contour associated with RF communication between the first wireless device and the second wireless device;

adding a correction factor to the first signal strength contour to produce a corrected signal strength contour, wherein the correction factor includes the sums of the differences between the transmit power and the antenna gain associated with at least one of the first and second wireless devices.

2. The method of claim 1, wherein the first type of wireless device is a mobile unit, and the second type of wireless device is an access port.

3. The method of claim 1, wherein the first type of wireless device is an access port, and the second type of wireless device is a mobile unit.

4. The method of claim 1, wherein the first and second types of wireless devices are configured to operate within a wireless environment selected from the group consisting of 802.11, RFID, WiMax, WAN, Bluetooth, Zigbee, and UWB.

5. The method of claim 1, wherein computing the set of signal strength values includes computing signal strength based on a receiver signal strength indicator (RSSI).

6. The method of claim 5, wherein the step of determining the signal strength contour includes:

determining a first RSSI contour for the first wireless device as the sum of the transmit power of the second wireless device, the antenna gain of the second wireless device, and a path loss;

determining a second RSSI contour for the second wireless device as the sum of the transmit power of the first wireless device, the antenna gain of the first wireless device, and the path loss.

7. The method of claim 6, wherein the step of adding a correction factor includes adding, to the first RSSI contour, the sum of the difference between the transmit powers of the first and second wireless devices and the difference between the antenna gains of the first and second wireless devices.

8. The method of claim 5, wherein the step of determining the signal strength contour includes:

generating a predetermined set of fingerprint data comprising RSSI values determined by a test mobile device interacting with the first wireless device, wherein the test mobile device has an associated antenna gain and transmit power.

9. The method of claim 8, wherein the step of adding a correction factor includes adding, to the fingerprint data, the sum of the difference between the transmit powers of the test mobile device and second wireless device and the difference between the antenna gains of the test mobile device and the second wireless device.

10. A wireless network system comprising:

a first wireless device having a first type;

a second wireless device having a second type, wherein the signal strength contour of the first wireless device is not coextensive with the signal strength contour of the second wireless device; and

a locationing module configured to identify location of the second wireless device with respect to the first wireless device, the locationing module configured to determine a signal strength contour associated with RF communication between the first wireless device and the second wireless device, and add a correction factor to the first signal strength contour to produce a corrected signal strength contour, wherein the correction factor includes the sums of the differences between the transmit power and the antenna gain associated with at least one of the first and second wireless devices.

11. The system of claim 10, wherein the first type of wireless device is a mobile unit, and the second type of wireless device is an access port.

12. The system of claim 10, wherein the first type of wireless device is an access port, and the second type of wireless device is a mobile unit.

13. The system of claim 10, wherein the first and second types of wireless devices are configured to operate within a wireless environment selected from the group consisting of 802.11, RFID, WiMax, WAN, Bluetooth, Zigbee, and UWB.

14. The system of claim 10, wherein the locationing module computes the set of signal strength values based on a receiver signal strength indicator (RSSI).

15. The system of claim 14, wherein the locationing module computes the signal strength contour by determining a first RSSI contour for the first wireless device as the sum of the transmit power of the second wireless device, the antenna gain of the second wireless device, and a path loss;

and determining a second RSSI contour for the second wireless device as the sum of the transmit power of the first wireless device, the antenna gain of the first wireless device, and the path loss.

16. The system of claim 15, wherein the correction factor is the sum of the difference between the transmit powers of the first and second wireless devices and the difference between the antenna gains of the first and second wireless devices.

17. The method of claim 14, wherein the locationing module computes the signal strength contour by generating a predetermined set of fingerprint data comprising RSSI values determined by a test mobile device interacting with the first wireless device, wherein the test mobile device has an associated antenna gain and transmit power.

18. The method of claim 17, wherein the correction factor is the sum of the difference between the transmit powers of the test mobile device and second wireless device and the difference between the antenna gains of the test mobile device and the second wireless device.

19. A locationing module for determining the location of a mobile unit with respect to an access point associated therewith, the locationing module configured to determine a signal strength contour associated with RF communication between the access point and the mobile unit, and add a correction factor to the signal strength contour to produce a corrected signal strength contour, wherein the correction factor includes the sums of the differences between the transmit power and the antenna gain associated with the mobile unit and the access point.

20. The module of claim 19, wherein the mobile unit and access point are configured to operate within a 802.11 environment.