Non-Uniform 16-Symbol Constellation for 3/15 LDPC BICM
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Solution Overview
Problem
Bit-Interleaved Coded Modulation (BICM) systems, used in digital broadcast channels, exhibit a significant difference from the Shannon limit in terms of capacity, necessitating the use of a more efficient signal constellation for effective error correction coded data transmission.
Innovation Solution
A modulator utilizing a non-uniform 16-symbol signal constellation, optimized for an LDPC coder with a code rate of 3/15, is employed for error correction coded data transmission in next-generation broadcast systems, such as ATSC 3.0, where the 16 symbols are distributed with non-uniform distances and symmetry across quadrants, enhancing transmission efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a uniform signal constellation is used in BICM systems, then the system structure remains simple and easy to implement, but the transmission capacity falls significantly short of the Shannon limit
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 features variable symbol distances and asymmetric distribution patterns that are specifically optimized for LDPC code rate 3/15, thereby improving transmission capacity while maintaining manageable complexity through targeted optimization
2Reliability
If a non-uniform signal constellation is designed to optimize BICM performance, then transmission reliability improves, but the complexity of modulation and demodulation increases
Solution Approach 1:
The patent applies local quality by designing a non-uniform signal constellation where different symbol regions have different distance characteristics optimized for specific LDPC code rate 3/15 performance requirements. This localized optimization improves bit error rate performance while the structured approach keeps modulation complexity manageable
Solution Approach 2:
The patent applies parameter changes by modifying the signal constellation parameters (symbol distances, positions, and distributions) from uniform to non-uniform values. These parameter adjustments are specifically tailored to optimize performance for LDPC code rate 3/15, improving reliability while the changes remain within implementable ranges
3Productivity
If traditional uniform 16-QAM modulation is used, then implementation is straightforward and compatible with existing systems, but transmission efficiency and error correction performance are suboptimal
Solution Approach 1:
The patent applies asymmetry by replacing the symmetric uniform 16-QAM constellation with a non-uniform 16-symbol constellation that has asymmetric symbol distributions and varying distances. This asymmetric design optimizes transmission efficiency for LDPC code rate 3/15 while the structured approach maintains reasonable implementation complexity
Data Source
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.