A Multichannel Acoustic Chirp-Spread Modulation Approach Towards Diver-to-Diver Communication

In this work, we propose a single and multiband chirp signals for communication in the air and underwater channel. A Raspberry Pi based transceiver system and MAT-LAB are used for the demodulation of the chirp signals. The experiments, for both air and water, are conducted in static conditions, that is the transmitter and receiver are fixed. To increase the efficiency of signal processing, down-conversion or bandpass sampling is implemented on the receiver side. We use transmission bands between 60 kHz and 70kHz to reduce the impact of divers' communication on the maritime ecosystem and its natural communication bands. The structure of the demodulation is discussed in detail with focus on the frame detection and decision algorithm. In several different settings, we demonstrate the performance of this approach and transmit data of up to 12 Byte with data rates of 100 and 200 bit/s over 0.25 m in air and 4.5 m in water inside a highly echoic environment.