LDPC Bit Permutation for 16QAM Quasi-Error-Free Reception
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Solution Overview
Problem
The existing methods for transmitting and receiving digital audio and video signals in second-generation digital terrestrial television broadcasting, which utilize LDPC codes with QAM modulations, do not adequately achieve the required signal-to-noise ratio for quasi-error-free conditions, particularly with 16QAM, 64QAM, and 256QAM modulations.
Innovation Solution
The proposed solution involves improving the association between the bits outputted by the LDPC encoder and the constellation coordinates of QAM modulations by employing specific permutation schemes in the interleaver and demux blocks, similar to the DVB-S2 standard, to optimize the LDPC encoding with a 3/5 code rate for 16QAM, 64QAM, and 256QAM modulations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If standard LDPC encoding with QAM modulation is used, then system complexity is kept simple, but signal-to-noise ratio performance is insufficient for quasi-error-free conditions
Solution Approach 1:
The patent applies preliminary action by performing bit permutation and association optimization between LDPC encoder output bits and QAM constellation coordinates before modulation. Specific permutation schemes are pre-defined to optimally map coded bits to constellation points, thereby improving signal-to-noise ratio performance before the actual transmission occurs.
Solution Approach 2:
The patent changes parameters by introducing specific permutation patterns and association rules that optimize the mapping between coded bits and constellation coordinates. Different permutation schemes are defined for different code rates and modulation orders, adjusting the bit-to-symbol mapping parameters to achieve better error performance.
2Reliability
If bit permutation schemes are introduced to optimize LDPC encoding, then signal-to-noise ratio improves, but system complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the bit stream into groups that correspond to specific constellation coordinates. The interleaver block segments the LDPC coded bits and rearranges them according to predefined permutation patterns, while the demux block separates them for modulation. This structured segmentation enables optimized bit-to-constellation mapping without requiring complex adaptive processing.
Solution Approach 2:
The patent uses copying by implementing fixed permutation patterns and association rules that are pre-defined and replicated for different code rates and modulation orders. Instead of dynamically calculating optimal mappings, the system copies proven permutation schemes from standardized patterns, reducing computational complexity while maintaining performance benefits.
3Reliability
If standard interleaving is used, then implementation is simple, but association between encoded bits and constellation coordinates is suboptimal
Solution Approach 1:
The patent applies preliminary action by pre-defining optimal association rules between encoded bits and constellation coordinates before transmission. The interleaver is configured with specific permutation patterns that are determined in advance based on code rate and modulation type, eliminating the need for real-time optimization while achieving near-optimal bit-to-constellation mapping.
Solution Approach 2:
The patent changes parameters by adjusting the interleaving depth, permutation patterns, and association rules according to specific code rates and modulation orders. Different parameter sets are defined for different operating conditions, allowing the system to optimize bit association without requiring complex adaptive algorithms during transmission.
Data Source
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Figure 3C
AI summary
The present invention relates to methods for digital signal processing and to transmission/reception systems utilizing said methods; the present invention is based on the use of LDPC codes, in particular the LDPC code with a 3/5 code rate, in combination with a QAM modulation, in particular the 16QAM or 64QAM or 256QAM modulation; in transmission, a bit permutation (Demux) is carried out prior to the QAM constellation mapping function; in reception, the bit permutation is carried out after the QAM constellation demapping function.