System and method of passive and active scanning of WLAN-enabled access points to estimate position of a WLAN positioning device

• US 8,185,129 B2
• Filed: 07/06/2007
• Issued: 05/22/2012
• 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): Faragalla, Michael
• Application Number:
  US11/774,400
• Publication Number:
  US 20080008121A1
• Time in Patent Office: 1,782 Days
• Field of Search: 370/338, 370/328, 370/389, 4554561-4566, 455/448
• US Class Current: 455/456.1
• 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 passive and active scanning of WLAN-enabled access points to estimate position of a WLAN positioning device. A device estimates the position of itself. The device includes a WLAN radio module for receiving WLAN signals, 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. The WLAN radio module includes a phase for active scanning of WLAN APs in range of said device and a phase of passive scanning of WLAN APs in range of said device, and the passive scanning phase scans only a pre-determined and selected subset of WLAN channels. Under certain embodiments, the WLAN radio module includes a passive scanning phase that simultaneously scans multiple WLAN channels.

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 signals transmitted by WLAN APs in range of said device, wherein the WLAN APs are capable of transmitting on a set of WLAN channels;

logic to cause the WLAN radio module to perform a scanning sequence in which the WLAN radio module receives WLAN signals transmitted by WLAN APs in range of said device, wherein the scanning sequence includes an active scanning phase and a passive scanning phase, each of the active and passive scanning phases ending after detecting a sufficient numbers of APs to locate the 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;

wherein said WLAN radio module is configured to receive signals transmitted by WLAN APs on only a subset of said set of WLAN channels upon a start of the scanning sequence, wherein the subset consists only of WLAN channels that are most commonly used in at least one selected geographic region.

2. The device of claim 1 wherein said WLAN radio module scans multiple WLAN channels in parallel during the scanning sequence.

3. The device of claim 1 wherein the active scanning phase performed by the device minimizes power consumption and occurs when the device is not associated with any AP.

4. The device of claim 1 wherein a frequency of the scanning sequence performed by the device is reduced to minimize power consumption, when the device is associated with an AP.

5. The device of claim 1 wherein the scanning sequence performed by the device is stopped after a selected number of scans to minimize power consumption, when the device is associated with an AP.

6. The device of claim 1 wherein the scanning sequence is performed when the device is activated for other applications.