A self-adaptive body channel communication scheme for backward path loss reduction

Body channel communication (BCC) is one of the best candidates for communications in wireless body sensor networks as it uses the human body as transmission media to minimize transmission loss resulting better energy efficiency. The main issue of BCC is the loss in its backward path, which is formed by the capacitive coupling between two floated GND electrodes (GEs) of transmitter (TX) and receiver (RX). To mitigate the backward path loss, an off-chip inductor could be used to resonate with the backward capacitance to reduce the impedance of the backward path. However, this method is not suitable for wearable applications as the off-chip inductor only works for fixed communication distance. In this paper, we present a novel self-adaptive capacitive compensation (SACC) scheme to reduce the capacitive loss of the backward path. The proposed system automatically estimates the distance between GEs of TX and RX with the help of received signal strength indicator (RSSI). The backward capacitance is then calculated based on the estimated distance. And then the capacitance is compensated by a digitally controlled active inductor to reduce the backward path loss. Simulation shows that the proposed scheme achieves more than 15 dB channel enhancement at the IEEE 802.15.6 standard frequency.