Accuracy improvement algorithms for prediction of user location using receive signal strength indication in infrastructure WLANs

An analysis of the performance of several algorithms for improving the estimation of user location in a standard infrastructure wireless local area network (WLAN) is presented. The basic method involves comparing real-time received signal strength indication values with those stored in a precreated radio map to estimate the user´s location. However, this basic tracking technique can have an rms error of almost 5 m, which is particularly high for indoor tracking. The performance of three different refinement algorithms was simulated across a range of testbed environments. One of the algorithms, constrained movement, offered almost a 40 % improvement in rms error (2.8 m for a measurement uncertainty of 2.5 dB) and performed consistently well across all of the environments considered.