BodySense: An Expandable and Wearable-Sized Wireless Evaluation Platform for Human Body Communication

TL;DR

This paper addresses the challenge of realistically evaluating capacitive Human Body Communication (HBC) for wearable devices, where environmental factors and return-path coupling can bias measurements. It introduces BodySense, a wearable-sized, expandable evaluation platform built around a BLE-enabled SiP and an M.2 interface to host application-specific Rx/Tx front-ends, enabling true wearable-to-wearable testing in the 4–64 MHz range. Through a comparative study against classical grid-connected DAQ, the authors demonstrate an average channel-gain overestimation of $18.15\,\mathrm{dB}$ when using conventional setups, underscoring the importance of wireless, body-centered testing. The results show that capacitive HBC can achieve energy efficiencies comparable to BLE at practical data rates, highlighting its potential for battery-free, body-worn sensing networks and motivating further development of realistic evaluation platforms.

Abstract

Wearable, wirelessly connected sensors have become a common part of daily life and have the potential to play a pivotal role in shaping the future of personalized healthcare. A key challenge in this evolution is designing long-lasting and unobtrusive devices. These design requirements inherently demand smaller batteries, inevitably increasing the need for energy-sensitive wireless communication interfaces. Capacitive Human Body Communication (HBC) is a promising, power-efficient alternative to traditional RF-based communication, enabling point-to-multipoint data and energy exchange. However, as this concept relies on capacitive coupling to the surrounding area, it is naturally influenced by uncontrollable environmental factors, making testing with classical setups particularly challenging. This work presents a customizable, wearable-sized, wireless evaluation platform for capacitive HBC, designed to enable realistic evaluation of wearable-to-wearable applications. Comparative measurements of channel gains were conducted using classical grid-connected and wireless Data Acquisition (DAQ) across various transmission distances within the frequency range of 4 MHz to 64 MHz and revealed an average overestimation of 18.15 dB over all investigated distances in the classical setup.

Figures (6)

• Figure 1: Comparison between HBC DAQ setups: (left) Classical DAQ setup using grid-powered measurement tools, (right) Miniaturized and fully-wireless DAQ setup.
• Figure 2: Equivalent circuit for classical DAQ (red) and wireless DAQ (blue).
• Figure 3: System overview: (a) High-level block diagram of the main platform BodySense, (b) Tx carrier circuit, (c) Rx carrier circuit, (d) BodySense platform, equipped with M.2 carrier.
• Figure 4: Overview of the experimental setup for (a) wireless and (b) classical data readout. Transmitter and receiver placement are identical for both scenarios.
• Figure 5: Channel gains measured over different frequencies for the classical and the wireless receiver scenario.