ANALYSIS AND DEMONSTRATION OF HUMAN-COMPUTER INTERACTIONS USING ELECTRO-QUASISTATIC HUMAN BODY COMMUNICATION

Due to several innovations Moore's law scaling in the past several decades, consumer electronics continue to reduce in size and miniaturize. Radio frequency(RF) and electromagnetic(EM) wave techniques continue to strain power budgets of wearables due to it's high loss near conductors. Recently emerging alternatives such as EQS-HBC promises to reduce the power consumption by 10-100x as well as improved physical security over RF EM techniques.

Lab sized or commercial-off-the-shelf form factor measurement equipment do not accurately capture the channel as the loss of a near-field operated EQS0-HBC wearables such as a watch. In the near-field and for capacitive HBC the channel characteristics is a strong function of it's form factor. Hence, a need to study the channel variation "in-device" is a necessary part of a successful miniaturized wearable implementation.

Furthermore, wearables are always on the move and may be used on the body other than just the wrist. Additional studies relating to the posture, environment and location on body are necessary to fully characterize the channel. Chapter 2 covers the channel loss of a miniaturized EQS-HBC wearable and demonstrates the first wearable-wearable link.

Outside of the lab environment interferences are ever present. While radio waves are heavily moderated by the FCC in the United States and other standards org, interference in the low frequency (<30MHz) often have comparatively relaxed limits and can be considered a FCC Part 15b unintentional radiator. The interferences at these frequency can couple to the body and create significant degradation in channel capacity. In order to implement a reliable EQS-HBC wearable, interference spectrum of the body must be studied in a variety of environments. Chapter 3 provides an in-depth characterization of the interference spectrum on the body as seen from the form-factor of a wearable device.

As EQS-HBC becomes prolific and more robust, advanced devices can intelligently adapt to their surroundings to improve channel performance. Chapter 4 presents a study of EQS-HBC receivers and their interactions with humans in combination with surrounding metal structures. As EQS-HBC receivers and transmitters can see a signal increase owing to nearby ambient conductors, a study can be performed to understand these interactions. This understanding can expand operating environments and avoid pitfalls introduced by environmental conductors.

Chapter 5 covers the study of multiple human body communication. As it is necessary in order to realize multiple body area network devices.

Finally, EQS and more generally non-far field techniques can be applied not only to the human body but to alternative conductive mediums as well. The work here demonstrates for the first time an EQS and resonant cavity channels (intentionally not operating in the far-field)- demonstrating that wireless communication can be achieved in a car using only the chassis. These techniques provide a security benefit over wireless comms while maintaining a packaging/space benefit over physical twisted pairs (which is the common technique today). Chapter 6 highlights and demonstrates these fundamentally different physical layer techniques for achieving wireless communication in a densely conductive medium.