Peter S. Hall - Antennas and Propagation for Body-Centric Wireless Communications. Second Edition

CHAPTER 1

CHAPTER 2

CHAPTER 3

CHAPTER 4

CHAPTER 5

CHAPTER 6

CHAPTER 7

CHAPTER 8

CHAPTER 9

CHAPTER 10

The potential value to society of body-centric wireless communications is being increasingly recognized. They are important for supporting a population with increasing life expectancy, and they give improved survival to those with chronic illness. They also have use in promoting safe independent living, limiting complications, and expediting safe discharge after surgery. Additionally, they also have a use for general well-being, sports, and public safety applications, such as firefighters. All of these require ubiquitous and pervasive monitoring of biological indices. Such devices need to be miniaturized, low cost, and easy to use. Yet they also are technologically sophisticated and include context aware and autonomic sensing, while being suitable for continuous long-term use even in harsh environments.

A body-centric wireless network contains a number of important technologies, ranging from novel biosensor design, biocompatible materials, and power harvesting, to low-power communications, integrated circuits, and systems. Among these, it is wireless communication that frees the network from the tyranny of wired connection and helps to make it more discrete and user-oriented. Miniaturization is an important element in allowing the integration of wireless data-paths into sensor nodes. Sensors are required to be small, and the communication transceiver circuits and antennas need to be miniaturized in order to facilitate sensor node realization or to be integrated into smart fabrics for improved comfort and user compliance. For both wearable and implantable devices, accurate modeling of induced electromagnetic fields and propagation in or around the body is a prerequisite to the design of power-efficient communication pathways, given the stringent power constraint of these devices.

This book is focused on low-power wireless communication and antenna design for body sensor networks. It provides researchers, designers, and developers with an up-to-date theoretical foundation and practical considerations, as well as exemplar implementations of the technologies for real-life applications. It is an important reference for those already working in the field and, I am sure, will also convince those who are considering entering this fascinating and rewarding topic of research and development.

I congratulate the editors and contributors on bringing this timely second edition together, and I am sure it will be as successful as the first one.

Guang-Zhong Yang, PhD, FREng

London, May 2012

The first edition of this book, published in 2006, came at a time when the topic of antennas and propagation for body-centric wireless communications was being viewed as novel, full of significant challenges, and responding to serious societal needs, particularly to those of monitoring those who are at risk and the elderly through wireless body sensor networks. In parallel with developments in antennas and propagation, the wider areas of networks, sensors, and applications saw explosive growth. New conference series were being established in these areas, and within the antennas and propagation community, the topic began to be covered by keynote addresses and special sessions. Since then, the topic has developed in several ways. There is more understanding of the basic action of channels on and into the body, and in how to design antennas for working close to or inside of the body. Now, in many antennas and propagation conferences, body-centric sessions are well-established, and around the world both research groups and industrialists are entering the field.

The response to the first edition from our colleagues was gratifying, as we always felt that body-centric communications was an area that would both unify various existing strands and offer new challenges for understanding, design, simulation, and measurement techniques. For example, while the simulation of channel variations for moving bodies can, in principle, be solved with very large computer resources, researchers are being taxed to devise new simulation methodologies, or even more of a challenge, new analytical solutions, for electromagnetic fields in the vicinity of arbitrarily shaped in homogenous and moving objects.

Since 2006, researchers have taken up some of these challenges, and there is much new material to discuss in this second edition. While the structure of this edition is the same, many of the chapters have been thoroughly updated or have been expanded to include new data and topics; the introduction fully itemizes the new material. However, this is a work in progress. As new applications appear, companies design new systems that are effective, efficient, and user-centered. Underpinning this continuing exploitation is a deeper knowledge of the behavior of electromagnetic fields, around and into the body, and of how to convert this into improved design, simulation tools and measurement processes. We hope that readers will learn much from this new edition and will be stirred to contribute to this activity.

In this new edition, the team of contributors has grown! We thank all of them for their hard work in meeting the short deadlines and thus making our task of bringing it together easier. In particular, we would like to thank our editor, Manika Power of Artech House, for her encouragement and patience.

Peter Hall and Yang Hao

May 2012