Evaluation of TOA-based localization schemes using range estimation at network layer in WLAN environment

A lot of wireless localization schemes using time of arrival (TOA) have been proposed in the literature with comprehensive performance comparisons in terms of accuracy, complexity and robustness. The major issue in TOA-based localization schemes is that the presence of error due to non-line-of-site (NLOS) propagation in the range measurements introduces a lot of errors in location estimation. Thus we have focused on those TOA-based localization schemes that can mitigate the effect of NLOS errors to provide reasonable location accuracy. Another major issue in TOA-based localization is the computational complexity incurred by solving the non-linear equations associated with the location estimation. Thus, among the various TOA-based localization schemes that work in NLOS environment, we have chosen two-step least square (LS) method for estimation of location of a mobile user in WLAN environment. To the best of our knowledge, no such real evaluation of two-step LS method does exist in literature. In this paper, we have proposed a novel technique for estimation of round trip time (RTT) between the Base Station (BS) and the Mobile Station (MS) of Internet Control Message Protocol (ICMP) packet in order to avoid the requirement for exact synchronization between the MS and the BS. Our proposed technique also shows a statistical post-processing step to reduce the errors incorporated into TOA measurements. Moreover, in this paper we have compared the performance of two-step LS method in theoretical environment with that in WLAN environment.