Body Area Network (BAN) technology is related to many applications inside, on and around the human body. The basic configuration of a BAN is a set of sensors, which are wearable or are placed inside the human body, transmitting signals to a terminal situated in a doctor’s office, in order to assess or monitor some aspect of a patient’s physical condition. Additionally, in many BAN applications the information about the sensor location is very important, since without knowing a sensor’s location, the transmitted data may be of limited value. As an example, Wireless Video Capsule Endoscopy (VCE) can benefit greatly from the addition of location information. The capsule transmits an RF signal from inside the human body to another sensor on the body surface or external. From the image data provided by the capsule, taken together with the location information, the doctor can locate the infection or lesion and initiate appropriate medical care. In this way, the treatment can be more effective and accurate. In this thesis we investigate the characteristics of Ultra-Wide Band (UWB) RF propagation for BAN devices placed around and inside the human body. We have made measurements around the human body and around a water-filled phantom using an E8363B Vector Network Analyzer (VNA), specifically measuring the S21 signal, which gives the transfer function. Based on these measurement results, we discuss the channel propagation for cases where the transmitter and the receiver are on the surface of the body and analyze the UWB propagation characteristics for RF localization. Because it is impractical or even impossible to make measurements inside the human body, we chose to apply the measurements using a simulation model of homogenous tissue, which serves as an approximation of the signal propagation environment inside the body. First, by comparing the multipath situation in free space and within a model of homogenous tissue, we are able to analyze the multipath effects inside human body. Then, because of the different characteristics of RF propagation in different bandwidths, we have made measurements at UWB (3GHz to 10GHz), and narrowband (402MHz) frequencies.

"Localization inside the human body using Radio Frequency (RF) transmission is gaining importance in a number of applications such as Wireless Capsule Endoscopy. The accuracy of RF localization depends on the technology adopted for this purpose. The two most common RF localization technologies use Received Signal Strength (RSS) and Time-Of-Arrival (TOA). This research first provides bounds for accuracy of localization of a Endoscopy capsule inside the human body as it moves through the gastro-Intestinal track with and without randomness in transmit power using RSS based localization with a triangulation algorithm. It is observed that in spite of presence of a large number of anchor nodes; the localization error is still in range of few cm, which is quite high; hence we resort to TOA based localization. Due to lack of a widely accepted model for TOA based localization inside human body we use a computational technique for simulation inside and around the human body, named Finite Difference Time Domain (FDTD). We first show that our proprietary FDTD simulation software shows acceptable results when compared with real empirical measurements using a vector network analyzer. We then show that, the FDTD method, which has been used extensively in all kinds of electromagnetic modeling due to its versatility and simplicity, suffers seriously because of its demanding requirement on memory storage and computation time, which is due to its inherently recursive nature and the need for absorbing boundary conditions. In this research we suggest a novel computationally efficient technique for simulation using FDTD by considering FDTD as a Linear Time Invariant (LTI) system. Then we use the software to simulate the TOA of the narrowband and wideband signals propagated inside the human body for RF localization to compare the accuracies of the two using this method. "

Among the low-power wireless technologies that have emerged in recent years, ultra-wideband (UWB) has successfully established itself as the reference for accurate ranging and localization, both outdoors and indoors. Due to its unprecedented performance, paired with relatively low energy consumption, UWB is going to play a central role in the next wave of location-based applications. As the trend of integration in smartphones continues, UWB is also expected to reach ordinary users, revolutionizing our lives the same way GPS and similar technologies have done. But the impact of UWB may not be limited to ranging and localization. Because of its considerable data rate, and its robustness to obstacles and interference, UWB communication may hold untapped potential for sensing and control applications. Nevertheless, several research questions still need to be answered to assess whether UWB can be adopted widely in the communication and localization landscapes. On one hand, the rapid evolution of UWB radios and the release of ever more efficient chips is a clear indication of the growing market for this technology. However, for it to become pervasive, full-fledged communication and localization systems must be developed and evaluated, tackling the shortcomings affecting current prototypes. UWB systems are typically single-hop networks designed for small areas, making them impractical for large-scale coverage. This limitation is found in communication and localization systems alike. Specifically for communication systems, energy-efficient multi-hop protocols are hitherto unexplored. As for localization systems, they rely on mains-powered anchors to circumvent the issue of energy consumption, in addition to only supporting small areas. Very few options are available for light, easy to deploy infrastructures using battery-powered anchors. Nonetheless, large-scale systems are required in common settings like industrial facilities and agricultural fields, but also office spaces and museums. The general goal of enabling UWB in spaces like these entails a number of issues. Large multi-hop infrastructures exacerbate the known limitations of small, single-hop, networks; notably, reliability and latency requirements clash with the need to reduce energy consumption. Finally, when device mobility is a factor, continuity of operations across the covered area is a challenge in itself. In this thesis, we design energy-efficient UWB systems for large-scale areas, supporting device mobility across multi-hop infrastructures. As our opening contribution, we study the unique interference rejection properties of the radio to inform our design. This analysis yields a number of findings on the impact of interference in communication and distance estimation, that are directly usable by developers to improve UWB solutions. These findings also suggest that concurrent transmissions in the same frequency channel are a practical option in UWB. While the overlapping of frames is typically avoided to prevent collisions, concurrent transmissions have counter-intuitively been used to provide highly reliable communication primitives for a variety of traffic patterns in narrowband radios. In our first effort to use concurrent transmissions in a full system, we introduce the UWB version of Glossy, a renowned protocol for efficient network-wide synchronization and data dissemination. Inspired by the success of concurrency-based protocols in narrowband, we then apply the same principles to define a novel data collection protocol, Weaver. Instead of relying on independent Glossy floods like state-of-the-art systems, we weave multiple data flows together to make our collection engine faster, more reliable and more energy-efficient. With Glossy and Weaver supporting the communication aspect in large-scale networks, we then propose techniques for large-scale localization systems. We introduce TALLA, a TDoA solution for continuous position estimation based on wireless synchronization. We evaluate TALLA in an UWB testbed and in simulations, for which we replicate accurately the behavior of the clocks in our real-world platforms. We then offer a glimpse of what TALLA can be employed for, deploying an infrastructure in a science museum to track visitors. The collected movement traces allow us to analyze fine-grained stop-move mobility patterns and infer the sequence of visited exhibits, which is only possible because of the high spatio-temporal granularity offered by TALLA. Finally, with SONAR, we tackle the issue of large-scale ranging and localization when the infrastructure cannot be mains-powered. By blending synchronization and scheduling operations into neighbor discovery and ranging, we drastically reduce energy consumption and ensure years-long system lifetime. Overall, this thesis enhances UWB applicability in scenarios that were previously precluded to the technology, by providing the missing communication and localization support for large areas and battery-powered devices. Throughout the thesis, we follow an experiment-driven approach to validate our protocol models and simulations. Based on the evidence collected during this research endeavor, we develop full systems that operate in a large testbed at our premises, showing that our solutions are immediately applicable in real settings.