Aerial acoustic data communication

Bilgiç, Kemal Önder
Spectrum has been a scarce commodity in RF communication. Acoustic data communication is an alternative to RF communication where data is transmitted through sound waves. In this thesis, several different aspects of acoustic data communication are investigated. A physical test setup is built where the data communication spectrum extends up to 40 kHz. Impulse response of the acoustic channel is considered in a laboratory environment. Acoustic spectrum beyond the hearing limit between 25 kHz to 35 kHz is found as a suitable band for the developed setup. Distance and multipath components are important factors, determining the communication accuracy. The physical layer for the communication system is built by taking RF Pager system as a reference. This system is also modified to improve the performance. Di erent modulation techniques are used in order to evaluate their performances for acoustic channels. BFSK, BPSK, QPSK, GMSK, OFDM, DSSS and FHSS techniques are implemented for comparison. Total and effective bit rate are considered for the overall performance evaluation of differentt modulation techniques. Several experiments are done in laboratory environment where there are several multipath components. As the distance between the transmitter and receiver is increased, path loss and multipath increases. It is shown that certain modulation techniques are more robust to multipath and are better candidates for acoustic communication. While acoustic environment is inefficient in terms of power, it is still a good candidate for communication in short distances.