BatComm: enabling inaudible acoustic communication with high-throughput for mobile devices

Acoustic communication is an increasingly popular alternative to existing short-range wireless communication technologies for mobile devices, such as NFC and QR codes. Unlike the current standards, there are no requirements for extra hardware, lighting conditions, or Internet connection. However, the audibility and limited throughput of existing studies hinder their deployment on a wide range of applications. In this paper, we aim to redesign acoustic communication mechanism to push the boundary of potential throughput while keeping the inaudibility. Specifically, we propose BatComm, a high-throughput and inaudible acoustic communication system for mobile devices capable of throughput rates 12X higher than contemporary state-of-the-art acoustic communication for mobile devices. We theoretically model the non-linearity of microphone and use orthogonal frequency division multiplexing (OFDM) to transmit data bits over multiple orthogonal channels with an ultrasound frequency carrier. We also design a series of techniques to mitigate interference caused by sources such as the signal's unbalanced frequency response, ambient noise, and unrelated residual signals created through OFDM, amplitude modulation (AM), and related processes. Extensive evaluations under multiple realistic settings demonstrate that our inaudible acoustic communication system can achieve over 47kbps within a 10cm communication range. We also show the possibility of increasing the communication range to room scale (i.e., around 2m) while maintaining high-throughput and inaudibility. Our findings offer a new direction for future inaudible acoustic communication techniques to pursue in emerging mobile and IoT applications.