<p>Progress in miniaturized computing and connectivity has led to a plethora of smart connected electronic devices around humans, leading us towards the era of seamless human-electronics co-operation. In this connected society, radiative communication using electromagnetic fields is the backbone of inter-device connectivity. This unfortunately leads to high power usage as well as physical signals being available for malicious interceptors to snoop. To address the need of security and energy efficiency of inter-device communication for devices on and around the human body, Human Body Communication (HBC) has been proposed. The fundamental philosophy of HBC is to use the human body as a medium - thus being helped and not hurt by the body - for communication between devices. Confinement of a signal within the body implies higher security as well as efficiency. This dissertation is an analysis of these properties of different HBC modalities, through electromagnetic modelling, simulation, and experienced. Electro-quasistatic (EQS) HBC has been explored in significant detail, including a complete theoretical formulation of return path capacitance, as well as a study of inter-body coupling for interference and security management in EQS-HBC. Magnetic modes of HBC have also been analyzed, and compared with its electric counterparts. Finally, a novel HBC technique, GSW-HBC, has been proposed. GSW-HBC or a Goubau line inspired surface wave based HBC, is shown to be a viable, secure and energy efficient alternative to RF wireless communication, leading the search for Gbps communication around the body.</p><p>In reference to IEEE copyrighted material which is used with permission in this thesis, the IEEE does not endorse any of Purdue University's products or services. Internal or personal use of this material is permitted. If interested in reprinting/republishing IEEE copyrighted material for advertising or promotional purposes or for creating new collective works for resale or redistribution, please go to <a href="http://www.ieee.org/publications_standards/publications/rights/rights_link.html" rel="noreferrer" target="_blank">http://www.ieee.org/publications_standards/publications/rights/rights_link.html</a> to learn how to obtain a License from RightsLink.</p>

Gait analysis is the systematic study of human walking. Clinical gait analysis is the process by which quantitative information is collected for the assessment and decision-making of any gait disorder. Although observational gait analysis is the therapist's primary clinical tool for describing the quality of a patient's walking pattern, it can be very unreliable. Modern gait analysis is facilitated through the use of specialized equipment. Currently, accurate gait analysis requires dedicated laboratories with complex settings and highly skilled operators. Wearable locomotion tracking systems are available, but they are not sufficiently accurate for clinical gait analysis. At the same time, wireless healthcare is evolving. Particularly, ultra wideband (UWB) is a promising technology that has the potential for accurate ranging and positioning in dense multi-path environments. Moreover, impulse-radio UWB (IR-UWB) is suitable for low-power and low-cost implementation, which makes it an attractive candidate for wearable, low-cost, and battery-powered health monitoring systems. The goal of this research is to propose and investigate a full-body wireless wearable human locomotion tracking system using UWB radios. Ultimately, the proposed system should be capable of distinguishing between normal and abnormal gait, making it suitable for accurate clinical gait analysis. / Ph. D.