N° d’ordre : 2016telb0396 Sous le sceau de l'Université Bretagne Loire Télécom Bretagne En accréditation conjointe avec l’Ecole Doctorale Sicma Study of on-body antennas and channel properties for short-range communications in the context of Wireless Body Area Sensor Networks (WBASN) Thèse de Doctorat Mention : Sciences et Technologies de l'Information et de la Communication (STIC) Présentée par Rizwan Masood Département : Micro-ondes Laboratoire : Lab-STICC Pôle : Micro-ondes et matériaux (MOM) Directeur de thèse : Christian Person Soutenance le 29 mars 2016 Jury : Christophe Delavaud Ingénieur R&D - HDR, CEA-Leti, Grenoble (Rapporteur) Rodolphe Vauzelle Professeur XLIM-SIC, Université de Poitiers (Rapporteur) Christian Person Professeur, Télécom Bretagne, Brest (Directeur de thèse) Ronan Sauleau Professeur, IETR - Université de Rennes 1(Co-encadrant de thèse) Olivier Sentieys Professeur, ENSSAT, Lannion (Examinateur) Patrice Pajusco Directeur d’études, Télécom Bretagne, Brest (Examinateur) Yann Toutain Directeur R&D, Satimo – Microwave Vision Group, Brest (Invitée) To my mother and father "There are only two ways to live your life. One is as though nothing is a miracle. The other is as though everything is a miracle." Albert Einstein Look up at the stars and not down at your feet. Try to make sense of what you see, and wonder about what makes the universe exist. Be curious. Stephen Hawking Acknowledgements This dissertation is the outcome of my PhD thesis which was initiated in Brest, France during January, 2013. Firstly, I would like to express my sincere thanks and gratitude to Prof. Christian Person for giving me the wonderful opportunity to work under his patronage on a very rich and enchanting research area. His supreme research spirit and aptitude really polished my intuitive and critical approach towards science. Apart from his valuable guidance and support, he has been very kind, welcoming and friendly to me as a human being. It was also a wonderful experience for me to work in Lab- STICC laboratory surrounded by gifted minds and smart scientists. I would also like to express my sincere thanks to Prof. Ronan Sauleau, the supervisor of my thesis for his valuable guidance and directions throughout the course of thesis. More particularly, his guidelines for a number of technical reports accomplished during this thesis have been remarkable. His superb technical writing immersed with precision and flair also polished my writing skills. I would also like to express my special thanks to Cominlabs and Brittany region of France to sponsor the BoWI project and hence, this thesis. I would like to acknowledge Pascal Coant, Raymond Jezequel, and Jean-Marc Autret from the Microwaves department for their technical support during various measurements realized in this thesis. I am also very grateful to Prof. Patrice Pajusco for his insightful suggestions and valuable guidelines. A special mention goes to all my great friends and brilliant colleagues especially Abdelrahman Ijjeh, Axelle Pillain, Georges Mikhail, Gloria Makhoul, John Eric Ortiz Guzman, Lyes Rahmouni, and Maksims Abalenkovs to name only a few for the wonderful time and cherishing moments that we spent together. Above all, I would like to express my profound thanks and gratefulness to my parents, brothers, sisters and all other family members for their special love, affection and cares for me regardless of the physical distances. Abstract This thesis finds its place in the framework of BoWI project. BoWI stands for Body- World Interaction and is a novel and innovative inspiration of Wireless Body Area Networks (WBANs). The major scientific contributions of this thesis are focused around two main topics for WBAN applications: (i) Radio channel characterization and (ii) antenna design with stable performance in proximity to human body while offering tunable features e.g., radiation pattern and polarization. For the first project, smart sensors were used incorporating ultra-miniaturized chip antennas under pattern diversity configuration which were developed by one of the project partners. These sensors were used to investigate the off-body radio channel considering various parameters such as delay spread and channel capacity using real-time multipath channel measurements. Significant improvement in channel capacity has been reported exploiting the 2×2 MIMO configurations compared to SISO systems especially at high SNRs. Small-scale channel fading has also been investigated for both off- and on- body channels using real-time measurement data. A robust fitting algorithm has been developed for this purpose, based on Maximum Likelihood Estimation and Kolmogorov- Smirnov test as goodness of fit. Optimum first-order fading models have been reported for both off- and on-body channels using the proposed fitting algorithm on real-time measurement data. For numerical channel studies, a robust channel simulator was also developed using an electrically small chip antenna on realistic 3D body morphologies with tunable gestures. The simulator includes various enhancements such as local mesh refinement and reduction techniques, hence offering the power to simulate arbitrary WBASN scenarios under limited simulation resources. The scope of the channel simulator has also been demonstrated for sample body postures showing its interest for posture classification in interactive gesture recognition concept as used in BoWI project. For the second sub-project, various simulation studies were first undertaken to consider the critical impact of human body on antenna performance. Antenna topologies with stable on-body performance and appropriate radiation patterns were designed for both on-and off-body applications e.g., Inverted-F antenna and short-circuited ring path antenna. Based on the characteristic mode theory of patch antennas, a compact dual-mode dual-pattern polarization diversity antenna has been designed. The antenna offers appropriate radiation characteristics for both on- and off-body applications at single frequency, meanwhile offering a negligible cross-coupling between the two modes and a stable on-body performance. It provides two different forms of diversities (radiation and polarization) in a single package, hence circumventing the use of antenna arrays since space and form factor are crucial for wearable applications. The antenna is also a suitable candidate for diversity and MIMO applications while providing reasonable diversity gain (close to 10 dB). Finally, the performance of radiation pattern and polarization diversities simultaneously has been demonstrated for body-centric applications. Significant improvements in link budget have been reported which are corroborated by both full- wave simulations and real-time measurements. Table of Contents Chapter 1. Context and state-of-the-art.....................................................................1 1.1. General Introduction, Wireless Body Area Sensor Networks......................................2 1.2. Introduction to BoWI project........................................................................................6 1.3. Radio and propagation for WBASNs...........................................................................7 1.3.1. On-body channel models...............................................................................9 1.3.2. Off-body channel models.............................................................................14 1.4. Electromagnetic characterization and modeling of human body................................17 1.4.1. Electromagnetic characteristics of body tissues..........................................17 1.4.2. Phantoms for modeling human body...........................................................18 1.4.2.1. Physical Phantoms........................................................................18 I. Liquid phantoms........................................................................19 II. Semisolid phantoms.................................................................19 III. Solid (dry) phantoms...............................................................20 1.4.2.2. Numerical Phantoms.....................................................................21 I. Theoretical phantoms................................................................21 II. Voxel phantoms........................................................................22 1.5. Antennas for WBASN applications...........................................................................24 1.5.1. Antennas for ISM band and UWB...............................................................24 1.5.2. Antennas with material enhancements ........................................................27 1.5.3. Wearable/Textile Antennas..........................................................................28 1.5.4. Adaptive or pattern-reconfigurable antennas...............................................30 1.6. Conclusions.................................................................................................................34 1.7. Thesis Structure..........................................................................................................34 References..........................................................................................................................36 Chapter 2. Radio channel characterization for WBASNs using ultra- miniaturized chip antennas.........................................................................................44 2.1.Introduction..................................................................................................................45