[Paper Review] Transmission of Video Image in Underwater Acoustic Communication

Han Zhang, Jun Yang|arXiv (Cornell University)|Feb 26, 2019

Underwater Vehicles and Communication Systems38 references6 citations

TL;DR

This paper presents a real-time underwater acoustic communication system that transmits video images using multiplexed orbital angular momentum (OAM) acoustic beams with topology charges from +1 to +8, modulated via on-off keying. The system achieves a spectral efficiency of 8 (bit/s)/Hz, demonstrating the potential of OAM multiplexing to significantly enhance underwater communication capacity despite bandwidth limitations.

ABSTRACT

Acoustic communication is currently considered as the best way to transmit information over long distances under water, since acoustic waves have lower attenuation in water than the other information transmission media. However, current information transmission rates of the underwater acoustic communication is usually limited by low-frequency bandwidth due to the large attenuation which characterized in high-frequency sound waves in water. Spiral acoustic beams with helical wavefront dislocations carrying orbital angular momentum have been applied to acoustic levitation and capture. Recently, harnessing the orthogonality and the infinite dimension of Hilbert space in underwater acoustic communication has been considered promising. Here, we construct a real-time underwater acoustic communication system to transmit video image. The system multiplexes eight orbital angular momentum topology charges ranging from +1 to +8 and encoded with on-off keying modulation format, achieving a spectral efficiency of 8 (bit/s)/Hz. This demonstration suggests that multiplexed information-carrying orbital angular momentum acoustic beams presents tremendous potential for increasing the capacity of underwater communication systems.

Motivation & Objective

• To address the limited data rate in underwater acoustic communication due to narrow bandwidth and high-frequency attenuation.
• To explore the use of orbital angular momentum (OAM) in acoustic waves for increasing spectral efficiency.
• To design and implement a real-time system capable of transmitting video images using OAM multiplexing.
• To validate the feasibility of using orthogonal OAM states in underwater environments for high-capacity communication.
• To demonstrate practical video transmission using OAM beams with on-off keying modulation in a controlled underwater setting.

Proposed method

• The system employs eight distinct OAM modes with topology charges ranging from +1 to +8 to multiplex data streams.
• Each OAM mode is modulated using on-off keying (OOK) to encode digital information.
• The acoustic wavefronts are shaped to carry orbital angular momentum, creating helical wavefront dislocations.
• The system leverages the orthogonality of OAM states in Hilbert space to separate multiplexed signals at the receiver.
• A real-time signal processing chain is implemented to generate, transmit, and decode the OAM-modulated signals.
• The communication link is established in a controlled underwater environment to test video transmission performance.

Experimental results

Research questions

• RQ1 Can OAM multiplexing in underwater acoustic communication significantly increase spectral efficiency?
• RQ2 Is real-time video transmission feasible using OAM-modulated acoustic beams in underwater environments?
• RQ3 How does the orthogonality of OAM states perform under real-world underwater channel conditions?
• RQ4 What is the achievable data rate and spectral efficiency when using multiple OAM modes with OOK modulation?
• RQ5 Can the system maintain reliable video transmission despite acoustic channel impairments such as multipath and noise?

Key findings

• The system successfully transmitted video images in real time using underwater acoustic channels.
• A spectral efficiency of 8 (bit/s)/Hz was achieved by multiplexing eight OAM modes with topology charges from +1 to +8.
• The use of OAM beams enabled spatial multiplexing of data streams through orthogonal modes in Hilbert space.
• The on-off keying modulation format was effectively implemented and decoded for each OAM mode.
• The results confirm the feasibility of using OAM multiplexing to overcome bandwidth limitations in underwater acoustic communication.
• The demonstration shows a substantial increase in data capacity compared to conventional narrowband underwater acoustic systems.