ROFDM Underwater Acoustic Communication Impulsive Noise Mitigation
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Solution Overview
Problem
Current multicarrier underwater acoustic communication systems are ineffective in environments with strong impulsive noise, such as coastal seas, where impulsive noise from marine life damages data symbols and exceeds the error-correction capabilities of classic channel coding.
Innovation Solution
The implementation of a repetitive orthogonal frequency-division multiplexing (ROFDM) communication system, which includes a transmitter and receiver that use a K-point Fast Fourier Transform, repetition, and cyclic prefix addition to generate and process signals, allowing for noise-state classification and selective combining to eliminate impulsive noise effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If classic channel coding is used to combat impulsive noise, then the system can handle some errors, but the error-correction capability is insufficient when impulse rate is high
Solution Approach 1:
The received signal is divided into multiple segments corresponding to different transmitted symbols. By segmenting the signal processing, the system can identify and exclude segments corrupted by impulsive noise while utilizing clean segments for reliable data recovery, thereby achieving robustness against high-rate impulsive noise that exceeds classic channel coding capabilities
Solution Approach 2:
The system performs preliminary noise detection and segment identification before final data decoding. By pre-identifying which signal segments are corrupted by impulsive noise through statistical analysis and comparison, the system can prepare appropriate processing strategies in advance, enabling reliable communication even when impulse rates exceed traditional error correction thresholds
2Object-affected harmful factors
If random pulse localization and removal is used, then impulsive noise can be eliminated, but this approach does not suit multicarrier communications because multicarrier signals are impulse-like
Solution Approach 1:
The system introduces an intermediary statistical analysis mechanism that examines the temporal and spectral characteristics of received signals. This intermediary process distinguishes between legitimate multicarrier impulses and harmful impulsive noise by analyzing patterns across multiple symbols, enabling noise removal while preserving the integrity of multicarrier communication signals
Solution Approach 2:
The system employs feedback mechanisms where the detected noise characteristics from one symbol are used to inform the processing of subsequent symbols. By continuously adapting the noise detection and removal strategy based on feedback from previous segments, the system can effectively eliminate impulsive noise while maintaining suitability for multicarrier communications
3Reliability
If Reed-Solomon decoding is used to mitigate impulsive noise, then some error correction is achieved, but the approach is ineffective when impulse rate is high due to limited error-correction capability
Solution Approach 1:
The system segments the received signal into multiple parts corresponding to different transmitted symbols and applies selective processing to each segment. By dividing the signal processing into manageable segments, the system can identify corrupted segments and handle them appropriately, achieving robustness against high impulse rates that would overwhelm conventional Reed-Solomon decoding
Solution Approach 2:
The system performs preliminary identification of impulsive noise locations and corrupted segments before applying error correction. By pre-processing the signal to mark and isolate noise-affected portions, the system enhances the effectiveness of subsequent error correction operations, enabling reliable communication even when impulse rates exceed the capabilities of traditional Reed-Solomon decoding
Data Source
AI summary
A communication system includes a repetitive orthogonal frequency-division multiplexing (“ROFDM”)transmitter communicating with an ROFDM receiver. The ROFDM transmitter includes an ROFDM modulator, which includes a K-point Fast Fourier Transform receiving a block of time-domain data symbols and generating an initial orthogonal frequency-division multiplexing symbol. The initial orthogonal frequency-division multiplexing symbol is based on a block of frequency-domain data symbols corresponding to the block of time-domain data symbols. The initial orthogonal frequency-division multiplexing symbol includes an ending part. The ROFDM modulator includes an orthogonal frequency-division multiplexing symbol repeater generating a repetitive orthogonal frequency-division multiplexing symbol by repeatedly reproducing the initial orthogonal frequency-division multiplexing symbol. The modulator includes a cyclic prefix adder pretending a cyclic prefix to the repetitive orthogonal frequency-division multiplexing symbol to generate a baseband transmitted signal. The cyclic prefix includes the ending part of the initial orthogonal frequency-division multiplexing symbol. The ROFDM receiver includes an ROFDM demodulator.