Contributions on Hybrid Localization Techniques For Heterogeneous Wireless Networks. (Contribution à l'Étude des Techniques Hybrides de Localisation dans les Réseaux Sans-fil Hétérogènes)

Recent advancement in wireless networks and systems has seen the rise of localization techniques as a worthwhile and cost-effective basis for novel services. These location based services (LBSs) have been more and more beneficial and money-making for telecommunications operators and companies. Various LBSs can be offered to the user such as tracking, advertisement, security, and management. Wireless networks themselves may benefit from localization information to enhance the performances of the different network layers. Location based routing, synchronization, interference cancellation are some examples of fields where location information can be fruitful. Two main tasks a localization system must be able to do: measurement of locationdependent parameters (LDPs) (e.g. time of arrival -TOA-, time difference of arrival -TDOA-, and received signal strength indicator -RSSI-) and estimation of position using location estimation techniques. The main goal of this dissertation is the study of different location estimation techniques. Estimation and measurement of LDPs are also investigated using a provided measurements campaign in order to have a complete understanding of localization field. Two types of location estimation techniques are addressed. The first one is based on algebraic formulation of LDPs and the second is based on the representation of LDPs in the form of geometric constraints and it is called Robust Geometric Positioning Algorithm (RGPA). Studied algebraic techniques are least-squares (LS), Maximum likelihood (ML), and Semidefinite programming (SDP). All of these techniques are developed and compared for both non-hybrid and hybrid localization schemes. Nonhybrid localization schemes are schemes which involve one type of LDPs (i.e. RSSI, TOA, or TDOA) while hybrid schemes are schemes which fuse more than one type of LDPs (i.e. RSSI+TOA, RSSI+TDOA, TOA+TDOA, and RSSI+TOA+TDOA). In addition to the comparison between the different studied algorithms, the focus is put on the importance of fusing hybrid LDPs. The dissertation proves that positioning accuracy is not only factor of involved LDPs and their precision but also factor of the used location estimation technique. Indeed, the proposed RGPA technique outperforms all algebraic methods and the ML technique is the most accurate algebraic technique. Besides, the dissertation recommends to use all available RSSIs and added necessary time-based LDPs in order to reach the requested positioning accuracy with minimum resources. The Cramer Rao lower bound (CRLB) and the geometric dilution of precision (GDOP) are developed for all localization schemes in order to assess theoretical reachable positioning accuracies and to evaluate the effect of different radio parameters on these performances. While the GDOP is factor only of geometric configuration of the targeted device with respect to anchors, the CRLB present a weighted version of iii te l-0 06 24 43 6, v er si on 1 17 S ep 2 01 1