Handling Samples Correlation in the Horus System
Handling Samples Correlation in the Horus System
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Date
2003-08-01
Authors
Youssef, Moustafa
Agrawala, Ashok
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Abstract
We present an autoregressive model for modeling samples autocorrelation
from the same access point in WLAN location determination systems. Our
work is in the context of the Horus system, which is a probabilistic WLAN
location determination system. We show that the autocorrelation between
consecutive samples from the same access point can be as high as 0.9.
Using our model, we describe a technique to use multiple signal strength
samples from each access point, taking the high autocorrelation into
account, to achieve better accuracy. Implementation of the technique in
the Horus system shows that the average system accuracy is increased by
more than 50%. Our results show that assuming independence of samples from
the same access point can lead to degraded performance as the number of
samples used in the estimation algorithm is increased, due to the wrong
independence assumption. We also discuss how to incorporate the new
technique with other algorithms for enhancing the performance of WLAN
location determination systems.
(UMIACS-TR-2003-75)