Characterisation of Wearable Electric-Field Communication Link for BAN Multimedia Applications

Wearable mobile devices demand seamless connectivity with low power consumption for improved quality of user experience. Capacitively coupled communication that is based on sensing a low frequency modulated electric field (several MHz), is a promising alternative to conventional electromagnetic wave radio links. However, achieving reliable over-the-air as well as air-to-body communication through electric field remains a research challenge as the presence of the human body influences the performance of an e-field communication channel. Therefore, in this work, we first benchmark a system for air-to-air communication and then characterise the effect of orientation and distance between the transmitter and receiver nodes when the receiver node is worn on the body. The presented work is an adaptation of a system previously developed for a standalone air-to-air communication scenario [16]. As an application, we integrate the receiver node into commercial overhead headphones to create a wireless audio system, recovering and demodulating a binary frequency shift keying (BFSK) digital audio signal. The signal is transmitted through the varying electric field resulting from a 4.45 MHz alternating voltage applied to the transmitter electrode. We present the bit error rate (BER) performance of the channel for various on-body electrode configurations and transmitter-receiver orientations. The system is capable of transmitting 8-bit mono audio at a sample rate of 16 kHz (128 kbps) with a BER of less than 10 ^−6.7 at 50 cm, and less than 10 ⁻⁴ at 75 cm,