Integrated Acoustic Frequency Comb Signal for Underwater Inverted Ultrashort Baseline Autonomous Positioning Systems

Inverted ultra-short baselines(iUSBL) systems provide low-cost and passive covert spatial sensing for autonomous underwater vehicles (AUV) networking, which is a prerequisite and advanced technology to support the Internet of Underwater Things (IoUT). In the iUSBL system, multiple AUVs can realize low-power autonomous positioning through passive reception of space-time information broadcast by a surface mothership beacon. However, existing iUSBL systems usually use different and independent communication and positioning signals due to the independent development of both technologies, which leads to wasted resources and inefficiencies. This paper presents a novel integrated acoustic frequency comb (IAFC) signal for communication and positioning integration of the iUSBL system. The IAFC signal with communication and positioning performances is designed by employing the spectral sparsity and orthogonal feature of the AFC. In particular, an AFC for positioning is created by employing the stable phase-locked characteristic. And an AFC for communication is generated via cyclic shift modulation. Compared to other integrated signals, IAFC achieves a comprehensive trade-off of positioning accuracy, spectral efficiency, robustness, and hardware compatibility by a fully-shared waveform design, avoids the corruption of positioning correlation by the randomness of communication coding. The experimental results proposed IAFC can implement positioning and communication simultaneously and enhance the spectral efficiency of the iUSBL system.