Research on computationally efficient ranging scheme for network-based wireless geolocation systems

Abstract

Recently, the interest in location based service lead a lot of researches on finding mobiles’ location. The conventional geolocation system like the global positioning system (GPS) requires an expensive GPS receiver within a mobile station (MS), and the line-of-sight path between the MS and the satellites, which makes it not be suitable for indoor geolocation. Thus, there is a need for new location finding technique. A new location finding system can be developed using new signaling system and infrastructure of the location sensors, or by utilizing an existing wireless network infrastructure. In this thesis, we focus on the latter one to locate the mobile station. Various positioning algorithms and ranging schemes for wireless location systems are reviewed in this thesis. Then the time of arrival (TOA) estimation technique for IEEE 802.15.4a system is proposed. In indoor environments, it is difficult to receive the GPS signal, and large multipaths make it hard to estimate angle of arrival (AOA). Hence, the distance measurements are generally used for finding users’ location in indoor area. The proposed system utilizes the chirp spread spectrum (CSS) in the physical layer (PHY) standard of IEEE 802.15.4a. Moreover, the matrix pencil algorithm, one of the super-resolution techniques is used for precise and low complexity TOA estimation. The estimated TOA can be converted into the distance measurement. The performance of the proposed system and the conventional MUSIC (MUltiple SIgnal Classfication) algorithm is compared by computer simulations. Also, the computational complexities are provided through the required number of real operations. The parameter which influences the performance is determined by empirical way. The determined parameter is applied for various channel models in IEEE 802.15.4a. The numerical results indicate that the proposed scheme outperforms the MUSIC algorithm even though it has comparatively low computational complexity. In addition,...