Low-Rate Turbo Code Structure for Low-SNR Error Correction

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Solution Overview

Problem

Existing communication systems face challenges in achieving low error rates in low signal-to-noise ratio (SNR) environments due to the limitations of traditional error control codes, particularly in designing codes that edge closer to the Shannon limit while minimizing complexity.

Innovation Solution

The development of turbo codes with low code rates using specific constituent encoding transfer functions, such as G(D)=[n0(D)d(D),n1(D)d(D),…⁢⁢n4⁡(D)d⁡(D)], where d(D)=1+D+D3 and n0(D)=1+D2+D3, to enhance error performance in low SNR environments.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional error control codes are used in low SNR environments, then system complexity is reduced, but error performance deteriorates and the Shannon limit cannot be approached

Engineering Contradiction:

Improveerror performanceVSAvoiddecoder complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The encoder is segmented into two independent constituent encoders connected by an interleaver, where each encoder processes the input sequence separately. This segmentation allows the system to achieve low error rates in low SNR environments while maintaining manageable decoder complexity through the independent processing structure.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

An interleaver is introduced as an intermediary component between the two constituent encoders. This intermediary permutes the input sequence before it reaches the second encoder, enabling the system to approach the Shannon limit by distributing error patterns while keeping the individual encoder designs relatively simple.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If low code rates are used to improve error performance in low SNR environments, then reliability increases, but transmission efficiency decreases

Engineering Contradiction:

Improveerror performanceVSAvoidtransmission efficiency

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The code rate is changed from traditional values to low code rates (e.g., 1/6, 1/7, 1/8) by adjusting the ratio of information bits to coded bits. This parameter change improves error performance in low SNR environments, while the parallel structure of the two constituent encoders helps maintain transmission efficiency through efficient use of the available bandwidth.

Inventive Principle:

Principle #35Parameter changes

3Productivity

If code rate is increased to improve transmission efficiency, then productivity increases, but error performance deteriorates in low SNR environments

Engineering Contradiction:

Improvetransmission efficiencyVSAvoiderror performance

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The system dynamically adapts to low SNR conditions by using low code rates with the parallel concatenated structure. The two constituent encoders work together to provide robust error correction that maintains transmission efficiency even at low code rates, allowing the system to optimize performance based on channel conditions.

Inventive Principle:

Principle #15Dynamics

Data Source

PatentUS8140946B2Method and apparatus for generating low rate turbo codes

Publication Date: 2012.03.20 HUGHES NETWORK SYST

AI summary

An approach is provided for encoding information bits to output a coded signal using turbo code encoding with a low code rate.