System and method of improving sampling of WLAN packet information to improve estimates of Doppler frequency of a WLAN positioning device

• US 7,768,963 B2
• Filed: 07/06/2007
• Issued: 08/03/2010
• Est. Priority Date: 07/07/2006
• Status: Active Grant

• Current Assignee: Skyhook Wireless Incorporated (Liberty Broadband Corp.)
• Original Assignee: Skyhook Wireless Incorporated (Liberty Broadband Corp.)
• Inventors: Alizadeh-Shabdiz, Farshid
• Primary Examiner(s): Pérez-Gutiérrez; Rafael
• Assistant Examiner(s): Patel; Nimesh
• Application Number:
  US11/774,399
• Publication Number:
  US 20080008120A1
• Time in Patent Office: 1,124 Days
• Field of Search: 455/453, 455/436, 455/439, 455/442, 455/522, 370/331, 370/319, 370/516, 370/328, 342/461, 342/109
• US Class Current: 370/328
• CPC Class Codes: G01S 5/019 Energy consumption
• CPC Class Codes: G01S 5/0242 Determining the position of transmitters to be subsequently used in positioning G01S5/0289 takes precedence
• CPC Class Codes: H04B 7/26 at least one of which is mobile
• CPC Class Codes: H04W 4/02 Services making use of location 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 84/12 WLAN [Wireless Local Area Networks]

Abstract

Systems and methods of improving sampling of WLAN packet information to improve estimates of Doppler frequency of a WLAN positioning device. A device estimates the position of itself. The device includes a WLAN radio module for receiving WLAN signals transmitted by WLAN APs in range of said device, extraction logic for extracting information from said received WLAN signals to identify the WLAN APs, and logic to cooperate with a WLAN-based positioning system to estimate the position of the device based at least in part on the extracted information identifying the WLAN APs in the range of said device. The WLAN radio module includes logic for measuring multiple received signal strength indicator (RSSI) values for sufficiently long WLAN packets to increase the sampled rate of RSSI of WLAN packets from WLAN APs and to thereby improve an estimate of the Doppler frequency of said device.

Claims

1. A device for estimating the position of itself in response to gathering wireless signal information from WLAN access points (APs), said device comprising:

a WLAN radio module for receiving WLAN packets transmitted by WLAN APs in range of said device;

logic located in the WLAN radio module for

extracting information from said received WLAN packets to identify the WLAN APs,

dividing said received WLAN packets into a plurality of segments,

measuring a received signal strength indicator (RSSI) value for each segment,

estimating a Doppler frequency of said received WLAN packet using the RSSI values for each segment; and

cooperating with a WLAN-based positioning system to estimate the position of the device based at least in part on the extracted information identifying the WLAN APs in the range of said device and the Doppler Frequency of the received WLAN packet.

2. The system of claim 1, wherein said received WLAN packet is divided into two segments.

3. The system of claim 1, wherein said received WLAN packet is divided into a number of segments that satisfies the Nyquist sampling theorem.

4. The system of claim 1, wherein the RSSI values comprise a distribution of power values.

5. The system of claim 4, wherein the distribution of power values comprises a Rayleigh distribution.

6. The system of claim 4, wherein the distribution of power values comprises a Rician distribution.

7. The system of claim 1, wherein RSSI values for each WLAN AP are evaluated separately from other WLAN AP RSSI values.