Chirp signal-based aerial acoustic communication for smart devices

Smart devices such as smartphones and tablet/wearable PCs are equipped with voice user interface, i.e., speaker and microphone. Accordingly, various aerial acoustic communication techniques have been introduced to utilize the voice user interface as a communication interface. In this paper, we propose an aerial acoustic communication system using inaudible audio signal for low-rate communication in indoor environments. By adopting chirp signal, which is widely used for radar applications due to its capability of resolving multi-path propagation, the proposed acoustic modem supports long-range communication independent of device characteristics over severely frequency-selective acoustic channel. We also design a backend server architecture to compensate for the low data rate of chirp signal-based acoustic modem. Via extensive experiments, we evaluate various characteristics of the proposed modem including multi-path resolution and multiple chirp signal detection. We also verify that the proposed chirp signal can deliver data at 16 bps in typical indoor environments, where its maximum transmission range is drastically extended up to 25 m compared to the few meters of the previous research.