Non-Uniform 16-Symbol Modulation for Low-Rate LDPC Codewords

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Solution Overview

Problem

Bit-Interleaved Coded Modulation (BICM) systems, used in digital broadcast channels, face a significant gap in performance compared to the Shannon limit due to the use of uniform signal constellations, which can be improved by employing non-uniform signal constellations optimized for specific code rates.

Innovation Solution

A modulator and modulation method utilizing a non-uniform 16-symbol signal constellation, specifically designed for an LDPC coder with a code rate of 3/15, which maps codewords to 16 symbols with non-uniform distances and symmetric amplitudes, optimizing performance for next-generation broadcast systems like ATSC 3.0.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If a uniform signal constellation is used in BICM systems, then the system structure remains simple and implementation is straightforward, but the performance gap compared to the Shannon limit increases significantly

Engineering Contradiction:

Improveimplementation simplicityVSAvoidperformance gap to Shannon limit

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent applies asymmetry by transitioning from a uniform signal constellation to a non-uniform 16-symbol constellation. The non-uniform constellation has varying symbol distances and asymmetric amplitude distributions that are specifically optimized for LDPC codes with code rate 3/15, thereby reducing the performance gap to the Shannon limit while maintaining implementation feasibility through systematic design

Inventive Principle:

Principle #4Asymmetry

2Reliability

If a non-uniform signal constellation optimized for specific code rates is employed, then the bit error rate and frame error rate performance is significantly enhanced, but the system complexity and design difficulty increase

Engineering Contradiction:

Improveerror rate performanceVSAvoidconstellation design complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent applies local quality by designing a non-uniform signal constellation where different symbol regions have different properties optimized for specific functions. The 16-symbol constellation has varying amplitudes and phases in different locations, with specific symbols having different distances from the origin, creating locally optimized regions that collectively improve overall error rate performance for LDPC code rate 3/15

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent applies parameter changes by modifying the signal constellation parameters (amplitudes, phases, and symbol distances) from uniform to non-uniform values. The specific amplitude values and phase angles are optimized to match the characteristics of LDPC codes with code rate 3/15, thereby improving reliability while managing complexity through parameter optimization rather than structural complexity

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS10819371B2Modulator and modulation method using non-uniform 16-symbol signal constellation for low-density parity check codeword having 3/15 code rate

Publication Date: 2020.10.27 ELECTRONICS & TELECOMM RES INST

AI summary

A modulator and a modulation method using a non-uniform 16-symbol signal constellation are disclosed. The modulator includes a memory and a processor. The memory receives a codeword corresponding to a low-density parity check (LDPC) code having a code rate of 3/15. The processor maps the codeword to 16 symbols of the non-uniform 16-symbol signal constellation on a 4-bit basis.