RSS-based indoor positioning accuracy improvement using antenna array in WLAN environments

The interest in utilizing Wi-Fi signals for indoor location estimation purposes has been increased recently due to wide deployment of WLANs. Received signal strength (RSS) based approach has become an attractive candidate for positioning owing to its simplicity and low-complexity, which can be easily implemented in modern wireless devices such as laptops and PDAs. However, the challenging nature of indoor wireless propagation environments provoke time varying location estimations from RSS based positioning algorithms. In this paper, we have shown that this variability of the location estimations can be reduced by introducing an antenna array at the receiving station. In our proposed approach, the variation of the received signal power with respect to time is averaged using a uniform linear antenna array (ULA) at the mobile station. We further explore the impact of number of array elements on the accuracy of the position estimations by using representative set of multi-lateration algorithms. In the first phase of analysis, we consider uncorrelated Rayleigh fading channels on each antenna element whilst in the second phase, we take into account the fading correlation between antenna elements using the spatial correlation function for two-dimensional (2D) diffuse field. The proposed positioning technique can be integrated into IEEE 802.11 compatible receivers with single-input multiple-output (SIMO) capability, thus be able to use for robust indoor localization purposes.