Measurement and Evaluation of Electric Signal Transmission through Human Body by Channel Modeling, System Design, and Implementation

Human body communications (HBCs), employing the human body as a signal transmission medium, can provide efficient and intuitive methods to form a network in the body. This article presents a comprehensive study for a highly reliable HBC system, including body channel modeling, transceiver design, and performance evaluation through implementation, in consideration of practical sensor network environments for wearable and implantable devices applicable to healthcare and biosignal acquisition. Body channel characteristics based on capacitive couplings, such as root mean square delay spread and mean path gain (MPG), were explored by measuring the body impulse responses under 12 experimental conditions, determined by the variation in body postures and device locations between the wrist and positions assumed under the scalp through a customized experimental setup with micropig-derived biomembranes (MBMs) used for wrapping the devices to emulate an implantable environment. The proposed transceiver design for digital transmission, including a preamble structure and signal modulation method supporting a maximum data rate of 1 Mb/s, was verified through the performance evaluations conducted for examining the frame detection probability and bit error rate (BER) in the body channel model at multiple operating frequencies of 32, 42, and 64 MHz. The proposed system reliability was demonstrated by the achievement of a BER of below ${4.7\,\times \, }{10}^{-8}$ through battery-powered implemented devices with dimensions of ${30\times 30 }\,\,{\text {mm}}^{2}$ , comprising a digital signal processing module (DSPM) for signal generation and detection processes, and an analog front-end module (AFEM) for recovering the received signal from signal deterioration by severe path loss and time-dispersive effect in the body channel.