Electric Field Short-range Over-the-air Communication for Wearable and IoT Applications with Off-the-shelf Microcontrollers

Wearable and home IoT applications require low-power connectivity to maximize battery life. Sensing a modulated electric field, referred to as capacitively coupled communication, is a promising alternative to communication via electromagnetic waves. However, achieving a reliable over-the-air communication through electric field remains a research challenge. We describe an efficient electric field based over-the-air communication system using frequency shift keying (FSK) which achieves arm’s length communication range with throughput suitable for real-time sensor streaming or even audio streaming. This is achieved through a highly sensitive electric potential receiver allowing communication when weakly coupled, such as between two devices far from any other object or human body. The digital FSK receiver uses an undersampling technique to reduce the complexity of the implementation. Another contribution of this work is the use of low-power ARM microcontroller to perform the modulation/demodulation, with a few additional off-the-shelf digital and analog components. We present a detailed performance analysis of the system when varying the transmit voltage and communication distance in five different scenarios/environments. The performance is analyzed and compared in terms of bit error rate (BER) and throughput. The system is capable of providing reliable communication link up to 1.2m with a user throughput of 75 kbps in the best case scenario, when placed over tarmac road. It is also shown that the system achieves a user throughput of at least 80 kbps for a distance of 70cm in the worst case scenario, when both the devices are hanged in air through strings.