Underwater Optical Communication Using Fountain Codes
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Solution Overview
Problem
Current underwater communication methods, such as tethered systems and acoustic communication, face limitations in bandwidth, latency, and mobility, particularly when transmitting high-quality video and enabling teleoperation in subsea exploration, due to constraints like tether length, low speed of sound, and high absorption of electromagnetic waves.
Innovation Solution
The implementation of a high-bandwidth, low-latency underwater optical communication system using Fountain codes and a two-layer digital encoding scheme, along with adaptive control of transmission properties, to enable efficient data transmission and positioning of underwater vehicles and sensors, employing Light Emitting Diodes (LEDs) for optical data packet transmission and Manchester encoding for error-resistant communication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If acoustic communication is used for wireless underwater transmission, then mobility is improved, but bandwidth is reduced and latency increases
Solution Approach 1:
The patent replaces acoustic wave-based communication with optical wave-based communication using LEDs and photodetectors. This substitution enables high-bandwidth wireless transmission while maintaining mobility, as optical waves provide significantly higher bandwidth compared to acoustic waves in underwater environments.
Solution Approach 2:
The patent changes the fundamental parameter of wave type from acoustic to optical. By using optical waves instead of acoustic waves, the system achieves both high bandwidth and low latency while maintaining wireless mobility, resolving the contradiction between bandwidth and mobility.
2Productivity
If optical communication is used for high bandwidth transmission, then bandwidth is improved, but reliability is reduced due to absorption
Solution Approach 1:
The patent segments video data into multiple data blocks and applies fountain codes to generate redundant encoded blocks. This segmentation and redundancy approach ensures that even if some optical transmission packets are lost due to absorption or interference, the original video data can be reliably reconstructed from the received packets, thereby maintaining high transmission reliability while utilizing optical communication's high bandwidth capability.
3Productivity
If tethered communication is used for high bandwidth data transmission, then bandwidth is improved, but mobility is reduced
Solution Approach 1:
The patent replaces the mechanical tether system with an optical wireless communication system using LEDs and photodetectors. This substitution eliminates the physical tether constraint, enabling fully mobile underwater vehicles to achieve high-bandwidth communication without any physical connection, thus resolving the contradiction between bandwidth and mobility.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution achieves 98% success in high-quality video transmission up to 25 yards and 100 ms latency, enabling effective teleoperation and data collection from underwater sensors, while optimizing transmission reliability and latency through bidirectional communication and adaptive control.
Implementation Method 1
employing Light Emitting Diodes (LEDs) for optical data packet transmission
Implementation Method 2
a photodetector to convert the received signal to an electrical signal
Data Source
AI summary
A method of optical underwater communications comprises applying a Fountain code to a plurality of data blocks. A sequence of optical data packets is transmitted through an underwater communications channel. Each optical data packet comprises one of the plurality of data blocks preceded by a preamble. The sequence of optical data packets transmitted through the underwater communication channel is received to generate a sequence of received data packets. The sequence of received data packets is sampled with the sampling clock to recover the plurality of data blocks.