Calculation of quality of wlan access point characterization for use in a wlan positioning system
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.
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
=
(
R
max
-
R
min
)
[
log
(
CF
n
)
-
log
(
CF
min
)
]
[
log
(
CF
max
)
-
log
(
CF
min
)
]
+
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:
CFn
=
KN
1
+
∑
i
=
1
N
2
V
i
T
i
wherein:
K is a correction factor;
N 1 is a subset of the RSS samples taken while the Wi-Fi enabled scanning device is stationary;
N 2 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
=
(
R
max
-
R
min
)
[
log
(
CF
n
)
-
log
(
CF
min
)
]
[
log
(
CF
max
)
-
log
(
CF
min
)
]
+
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.