Experiments on Acoustic Communication with Quadrature Amplitude Modulation in Multipath Environment

Abstract

An experiment on high-speed underwater acoustic data communication was carried out at real sea as a time-variant multipath channel. Demodulation was processed by a multichannel decision feedback equalizer (DFE) demodulator with adaptive filtering. The modulation method used was 16-quadrature amplitude modulation (16-QAM), transmitting rate was 32 k bit per second (bps), carrier frequency was 20 kHz, and bandwidth was 8 kHz (16–24 kHz). Good demodulation results were obtained at a sea trial despite the presence of high-level multipaths. At real sea, we proved that high-speed (32 kbps) acoustic communication can be realized even in a multipath fading channel with 16-QAM. Therefore, it is expected that the flexibility of the design of underwater equipment will be improved, because the influence of a circumferential structure can be neglected.

Experiment of Underwater Acoustic Communication with an Orthogonal Signal Division Multiplexing Scheme in a Harbor

“…to cope with ISI using adaptive equalizers such as DFE [1][2][3] . Moreover, it was found that the combination of DFE and array processing can increase communication quality [4][5][6][7][8][9][10][11][12] . Although the receiver complexity significantly increases as the effect of ISI increases, the single-carrier technique achieves good communication quality even in UWA channels, and an array-processing technique can be utilized to increase communication quality with practical complexity.…”

Measurement of Absorption Loss at 80 kHz Band for Wideband Underwater Acoustic Communication

“…1,2) In recent years, the need for high-speed underwater acoustic communication to construct sensor networks on the sea floor or to communicate with underwater vehicles has become higher. In the Japan Agency for Marine-Earth Science and Technology (JAMSTEC), two types of research on underwater acoustic communication are in progress, one is the short range but very high speed, [3][4][5][6][7][8] and the other is low speed but very long range. For the first type of research, the development of a wideband transducer and the experiments in a water tank and at sea have been advanced.…”

Twisted Acoustics: Metasurface‐Enabled Multiplexing and Demultiplexing

“…Unlike optical communication with the high frequency and light speed, data transfer based on sound is subject to deficiencies of low frequency and velocity, limiting the advancement of acoustic communication . Although remarkable progress has been made by introducing wavelength‐division multiplexing (WDM), time‐division multiplexing (TDM), and multilevel amplitude/phase modulation, data rate of acoustic communication is approaching its current limit, due to the fact that sound, as a scalar wave, bears no polarization or spin, as opposed to its optical counterparts. It is stringent to exploit plausible multiplexing mechanisms to encode information in a scalar field with multiple states orthogonal and compatible to existing degrees of freedom (DOF).…”