Human Body Communication between Pocketed and On-body Devices

The Internet of Bodies (IoB) interconnects devices in, on, and around the human body, enabling applications such as health monitoring, augmented reality, etc. Over the past few decades, human body communication (HBC), leveraging the human body as a conductive medium for data transmission, has emerged as an energy-efficient alternative to radio-frequency (RF) communication traditionally used in IoB systems, with improved physical security, and has attracted significant scholarly attention. The variability of the human body channel has been widely studied through simulations and measurements with devices placed in direct contact with the human body. However, the communication between on-body devices and a mobile device in the pocket, such as a smartphone, also represents a critical aspect of HBC systems. This paper, for the first time, explores the channel profile of HBC between an on-body device and a pocketed device at different postures, and device positions and orientations. Simulations and measurements with miniaturized wearable devices in both electro quasi-static (EQS) and body resonance (BR) regions are conducted. The results indicate that the pocketed transmitter (Tx) leads to ~15 dB larger channel gain reduction in EQS region than BR region. Moreover, pocketed Tx facing upward or downward leads to about 20 dB and 8 dB more channel gain degradation in EQS and BR regions, respectively, when the Tx and Rx are placed on different sides. These findings illustrate the HBC channel profiles of interaction between pocketed devices and on-body nodes, providing insights for developing HBC systems with pocketed devices.