Calculation of quality of wlan access point characterization for use in a wlan positioning system

• US 7,551,579 B2
• Filed: 05/08/2006
• Issued: 06/23/2009
• Est. Priority Date: 05/08/2006
• Status: Active Grant

• Current Assignee: Skyhook Wireless Incorporated (Liberty Broadband Corp.)
• Original Assignee: Skyhook Wireless Incorporated (Liberty Broadband Corp.)
• Inventors: Brachet, Nicolas, Pahlavan, Kaveh, Alizadeh-Shabdiz, Farshid
• Primary Examiner(s): Harper; Vincent P
• Assistant Examiner(s): Casca; Fred A
• Application Number:
  US11/430,224
• Publication Number:
  US 20070258409A1
• Time in Patent Office: 1,142 Days
• Field of Search: 370/338, 370/329, 370/331, 370/328, 370/310
• US Class Current: 370/328
• CPC Class Codes: H04B 17/318 Received signal strength
• CPC Class Codes: H04W 16/18 Network planning tools
• CPC Class Codes: H04W 24/10 Scheduling measurement reports ; Arrangements for measurement reports
• CPC Class Codes: H04W 36/22 for handling the traffic
• CPC Class Codes: H04W 48/16 Discovering, processing access restriction or access information
• CPC Class Codes: H04W 48/20 Selecting an access point
• 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 64/006 with additional information processing, e.g. for direction or speed determination
• CPC Class Codes: H04W 84/12 WLAN [Wireless Local Area Networks]
• CPC Class Codes: H04W 88/06 adapted for operation in multiple networks or having at least two operational modes, e.g. multi-mode terminals
• CPC Class Codes: H04W 88/08 Access point devices

Abstract

Methods and systems for classifying WLAN access points according to the quality of estimation of characteristics of the WLAN access points are provided. The classifications may be used to scale a reference database and quantify an expected error of estimation of the characteristics of the access points. WLAN access points may be classified based on their impact on a user'"'"'s position, speed of travel, and direction of travel estimation accuracy in a WLAN positioning system. A method for determining a quality of estimation of characteristics of a Wi-Fi access point comprises a Wi-Fi enabled scanning device measuring a number of received signal strength (RSS) samples of the Wi-Fi signal transmitted by the Wi-Fi access point. A total distance traveled by the Wi-Fi enabled scanning device while measuring the number of RSS samples is estimated and used to estimate the quality of estimation of characteristics of the Wi-Fi access point.

Claims

1. In a positioning system having a plurality of Wi-Fi access points in a target area, a method for determining a quality of estimation of characteristics of a Wi-Fi access point, the method comprising:

a Wi-Fi enabled scanning device receiving and measuring a number of received signal strength (RSS) samples of a Wi-Fi signal transmitted by the Wi-Fi access point;

estimating a total distance traveled by the Wi-Fi enabled scanning device while measuring the number of RSS samples;

using the estimated total distance traveled to calculate the quality of estimation of characteristics of the Wi-Fi access point;

associating a corresponding speed of travel of the Wi-Fi enabled scanning device with each RSS sample;

associating a corresponding period of time of scanning with each RSS sample;

determining a confidence factor, CF_n, using the sum of each of the speeds of travel of the Wi-Fi enabled scanning device weighted by the corresponding period of time of scanning for each RSS sample; and

determining the quality of estimation, R, according to the equation;

$R=\left(R_{\max }-R_{\min }\right)<br><br>\frac{\left[\log <br><br>\left({\mathrm{CF}}_n\right)-\log <br><br>\left({\mathrm{CF}}_{\min }\right)\right]}{\left[\log <br><br>\left({\mathrm{CF}}_{\max }\right)-\log <br><br>\left({\mathrm{CF}}_{\min }\right)\right]}+R_{\min }$

wherein;

R_max is a maximum quality of estimation;

R_min is a minimum quality of estimation;

CF_max is a maximum confidence factor; and

CF_min is a minimum confidence factor.

2. The method of claim 1, wherein:

CF_max is about 68; and

CF_min is about 36.

3. In a positioning system having a plurality of Wi-Fi access points in a target area, a method for determining a quality of estimation of characteristics of a Wi-Fi access point, the method comprising:

a Wi-Fi enabled scanning device receiving and measuring a number of received signal strength (RSS) samples of a Wi-Fi signal transmitted by the Wi-Fi access point;

estimating a total distance traveled by the Wi-Fi enabled scanning device while measuring the number of RSS samples;

using the estimated total distance traveled to calculate the quality of estimation of characteristics of the Wi-Fi access point;

associating a corresponding speed of travel of the Wi-Fi enabled scanning device with each RSS sample;

associating a corresponding period of time of scanning with each RSS sample;

determining a confidence factor, CF_n, according to the equation;

$\mathrm{CFn}={\mathrm{KN}}_1+\underset{i=1}{\overset{N_2}{\sum <br><br>}}<br><br>V_i<br><br>T_i$

wherein;

K is a correction factor;

N₁ is a subset of the RSS samples taken while the Wi-Fi enabled scanning device is stationary;

N₂ is a subset of the RSS samples taken while the Wi-Fi enabled scanning device is moving;

V_i is one of the speeds of travel of the Wi-Fi enabled scanning device corresponding to RSS sample i; and

T_i is one of the periods of time of scanning corresponding to RSS sample i; and

determining the quality of estimation, R, according to the equation;

$R=\left(R_{\max }-R_{\min }\right)<br><br>\frac{\left[\log <br><br>\left({\mathrm{CF}}_n\right)-\log <br><br>\left({\mathrm{CF}}_{\min }\right)\right]}{\left[\log <br><br>\left({\mathrm{CF}}_{\max }\right)-\log <br><br>\left({\mathrm{CF}}_{\min }\right)\right]}+R_{\min }$

wherein;

R_max is a maximum quality of estimation;

R_min is a minimum quality of estimation;

CF_max is a maximum confidence factor; and

CF_min is a minimum confidence factor.

4. The method of claim 3, wherein:

CF_max is about 68;

CF_min is about 36;

K is about 2; and

T_i is about 1 second.