Numerical Modeling and Experiment Validation of Propagation Channel for 5G Indoor Localization
Résumé rédigé par
Directeur de thèse:
Unité de recherche ? 0 Laboratoire inconnu!
The wide range of applications of the Internet of Things (IoT) makes the accurate indoor localization becoming an important focus of research. Among the principle techniques of location sensing, Time-Of-Arrival (TOA) and Time-Difference-Of-Arrival (TDOA) provide higher accuracy in small cell networks. In addition, Ultra Wide Band (UWB) systems are attractive as a means of measuring accurate TOA  and TDOA  since the accuracy and robustness of localization is proportional to the bandwidth. Impulse Radio (IR) UWB system is a very promising alternative to classic solutions (such as OFDM for instance) as it leads to ultra-low power consumption thanks to low duty cycles. An IR-UWB localization system at 60 GHz has been recently achieved , which answers the needs of both precise positioning and high data rate wireless communication in the context of 5G. The key problem of TOA-based positioning techniques is the solution of a set of nonlinear inconsistent equations in which the coordinates of the target terminals are the variables. In Line-of-Sight (LOS) environment, the methods to solve the equations, such as maximum likelihood and least square techniques work pretty well . However, due to the obstruction by indoor objects, LOS propagation path is not always the strongest path and Non-Line-of-Sight (NLOS) components are abundant, which leads to dramatically large TOA estimation errors, hence to poor position accuracy. The simplest way for NLOS mitigation is achieved by identifying and discarding the NLOS fixed terminals, then estimating mobile terminals by using one of the LOS techniques. The benefit of a priori channel knowledge for NLOS mitigation has been proved . Consequently, the key feature for accurate TOA-based localization is to obtain robust channel model. However, compared with outdoor environments, appropriate indoor channel models are trickier to obtain. The heights of the surrounding objects are analogous to the heights of the bases and terminals. So the multiple components and edges scattering are richer and the channel is seriously influenced by the specific indoor environment. This is even more so for millimeter wave frequencies: the delay spread is directly proportional to the number of path; the diffraction is significant; the transmission loss through walls is very high. With the above limitations, the conventionally experimental methods can only obtain unphysical models which rely on the particular scenes under consideration . So the exploration of the physical mechanism of indoor propagation is essential. One approach is electromagnetic numerical simulation which includes full-wave methods such as Finite Difference Time Domain (FDTD) and high frequency asymptotic methods such as Geometrical Optics (GO). Full-wave methods can achieve high accuracy but at the expense of large computational cost. In channel modeling, the scene is usually a room or a building’s floor which is a very large computational problem, especially at millimeter-wave frequency. Full-wave methods are more suitable for fine-details small simulation like antennas for instance rather than propagation. On the other hand, the low requirement of computational resources and high calculating speed makes high frequency asymptotic methods like GO widely applied in channel modeling . Considering the diffraction with Uniform Theory of Diffraction (UTD), the poor GO accuracy can be improved to some extent. To obtain realistic propagation channel behavior, a remarkable approach lies in the combination of GO and FDTD method . Hybrid code combining GO and full-wave techniques such as FDTD allows the simultaneous simulation of electrical large reflectors (such as walls, people, and large objects like table, chairs…) and electrical small antennas along with the surrounding scatters in their near-field range. Consequently, body-worn wireless systems can also be fully taken into consideration. The advantage of GO’s high speed execution will enable to study the stochastic influence of moving humans on the channel by considering a UTD-based scattering model of human body compatible with GO [9, 10]. Under the above consideration, this PhD thesis will study the indoor propagation of electromagnetic wave with a specific focus at 60 GHz using a hybrid GO-FDTD method which will be experimentally assessed with measurements, to satisfy the demand for indoor localization. This PhD thesis is a part of an international project between IMECAS and UPMC, which is partly supported by National Natural Science Foundation of China (NSFC) (Grant 61501454). The principal supervisor of this PhD thesis, Prof. Aziz Benlarbi-Delai, is a famous scholar in the domain of UWB, millimeter-wave indoor localization and Body Area Networks. The co-supervisor, Prof. Zhuoxiang Ren, is a famous scholar in the domain of numerically electromagnetic and multiphasic simulation. The co-supervisor, Associate Prof. Julien Sarrazin, is a famous scholar focusing on antennas, Body Area Networks, propagation, MIMO systems, and communication and localization at 60 GHz. The cooperators’ abundant experience will ensure the successful completion of the NSFC research project and this PhD thesis. Reference:  Davide Dardari, Andrea Conti, Ulric Ferner, Andrea Giorgetti and Moe Z. Win, "RangingWith Ultrawide Bandwidth Signals in Multipath Environments", Proceedings of The IEEE, vol. 97 , no. 2, Feb 2009, p404-426.  Ahmadreza Jafari, Theodoros Mavridis, Luca Petrillo, Julien Sarrazin, Michael Peter, Wilhem Keusgen, Philippe De Doncker, Aziz Benlarbi-Delai, “UWB Interferometry TDOA Estimation for 60 GHz OFDM Communication Systems”, IEEE Antennas and Wireless Propagation Letters, 2015  Michael Bocquet, Christophe Loyez and Nathalie Rolland, "An overview of 60 GHz location systems operating in multipath environments", International Journal of Microwave and Wireless Technologies, vol. 3, no. 2, Special Issue 02, Apr 2011, p223-230.  Ismail Guvenc and Chia-Chin Chong, "A Survey on TOA Based Wireless Localization and NLOS Mitigation Techniques", IEEE Communications Surveys and Tutorials, vol. 11, no. 3, 2009, p107-124.  Yuan Shen and Moe Z. Win, "Fundamental Limits of Wideband Localization - Part I: A General Framework", IEEE Transactions on Information Theory, vol. 56, no. 10, Oct 2010, p4956-4980.  Homayoun Hashemi, “The Indoor Radio Propagation Channel”, Proceedings of The IEEE, vol. 81, no. 7, Jul 1993, p943-968.  Magdy F. Iskander and Zhengqing Yun, “Propagation Prediction Models for Wireless Communication Systems”, IEEE Transactions on Microwave Theory and Techniques, vol. 50, no. 3, Mar 2002, p662-673.  Ying Wang, Safieddin Safavi-Naeini and Sujeet K. Chaudhuri, “A Hybrid Technique Based on Combining Ray Tracing and FDTD Methods for Site-Specific Modeling of Indoor Radio Wave Propagation”, IEEE Transactions on Antennas and Propagation, vol. 48, no. 5, May 2000, p743-754.  Theodoros Mavridis, Luca Petrillo, Julien Sarrazin, David Lautru, Aziz Benlarbi-Delai, Philippe De Doncker, “Theoretical and Experimental Investigation of a 60 GHz Off-Body Propagation Model”, IEEE Transactions on Antennas and Propagation, vol. 62, no. 1, 2014, p393-402  Theodoros Mavridis, Luca Petrillo, Julien Sarrazin, David Lautru, Aziz Benlarbi-Delai, Philippe De Doncker, “Creeping wave model of Diffraction of an Obliquely Incident Plane Wave by a Circular Cylinder at 60 GHz”, IEEE Transactions on Antennas and Propagation, vol. 62, no. 3, 2014, p1372-1377