Underwater acoustic communication to an unmanned underwater vehicle with a compact vector sensor array

Although underwater acoustic (UWA) communication based on vector sensors has been intensively investigated in past years, most of these works focus on theoretical analysis and simulation, and only very limited research on the practical application of vector sensors to underwater platforms (i.e., UUVs) is available. Recently, a data transmission experiment between a surface vessel and a mobile UUV was conducted in Qiandao Lake, Zhejiang Province, China. During this experiment, a compact vector sensor array with four elements was installed on the UUV. This paper proposes a two-stage data processing scheme for the experimental data. The fractional Fourier transform (FrFT) is first used to estimate the delay-Doppler parameter of UWA channels. The delay estimation can help determine the number of equalizer taps, while the Doppler estimation can help determine the re sampling frequency in the passband. Then, a new receiver called the vector multichannel decision feedback equalizer (VM-DFE) is proposed to deal with the inter-symbol interference (ISI) introduced by UWA channels. The experimental results show that the proposed two-stage data processing scheme realizes satisfactory performance and achieves a 1.8 dB gain compared with a pressure sensor-based equalizer.