LDPC Substream Mapping for Higher-Order Modulation Reliability
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Solution Overview
Problem
Low-density parity-check (LDPC) coding does not provide optimal coding performance when used with higher order modulation constellation mapping, such as 16-QAM, 64-QAM, and 256-QAM, due to the relationship between symbol reliability and error protection in digital television signal transmission systems like DVB-T and DVB-H.
Innovation Solution
A system that demultiplexes data into multiple substreams, encodes each using LDPC coding at different rates, and maps bits from these encoded substreams to specific regions of a symbol constellation map to address the reliability inequity in higher order modulation formats, employing parallel non-binary LDPC coding and symbol mapping tailored to the LDPC coding process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If LDPC coding is used with higher order modulation constellation mapping (16-QAM, 64-QAM, 256-QAM), then data transmission rate and bandwidth efficiency are improved, but coding performance and error correction capability deteriorate due to symbol reliability inequity
Solution Approach 1:
The patent segments the modulation constellation into multiple regions (e.g., inner region and outer region) with different error protection levels. Bits mapped to symbols in different regions receive different amounts of error correction protection, allowing the system to match error protection levels with symbol reliability. This segmentation resolves the contradiction by enabling higher order modulation while maintaining coding performance through differentiated protection strategies.
Solution Approach 2:
The patent applies local quality by providing different error protection levels to different bits within the same modulation symbol, depending on their position in the constellation map. Bits in more reliable symbol positions receive less protection, while bits in less reliable positions receive enhanced protection. This localized differentiation of error protection quality allows the system to achieve both high transmission rates and maintained reliability.
2Productivity
If higher order modulation formats (16-QAM, 64-QAM, 256-QAM) are used, then bandwidth efficiency is improved, but error protection and bit reliability become inequitable across the symbol constellation
Solution Approach 1:
The patent segments the symbol constellation map into multiple regions with different reliability characteristics. By mapping different bits to different regions and applying region-specific error correction, the system maintains bit reliability precision even as bandwidth efficiency increases through higher order modulation formats.
Solution Approach 2:
The patent changes the error protection parameter (coding rate) based on the symbol region and bit position. Different coding rates are applied to different bits depending on their reliability in the modulation constellation, thereby maintaining manufacturing precision (bit reliability) while enabling higher bandwidth efficiency through parameter adaptation.
3Device complexity
If uniform error protection is applied to all bits in higher order modulation, then implementation simplicity is maintained, but overall coding performance deteriorates due to mismatched protection levels
Solution Approach 1:
The patent segments the error protection structure into multiple levels corresponding to different symbol regions. This segmentation improves overall coding performance by matching protection levels to symbol reliability, while maintaining relatively simple implementation through systematic region-based classification and standardized encoding procedures for each region.
Data Source
AI summary
Modern coding and modulation techniques have greatly improved the transmission of signals. A method is described including receiving a stream of data bits, demultiplexing the stream into a first and second substream, encoding the first and second substream using a low density parity check coding process, and mapping the first substream to a first region of a symbol constellation map and the second substream to a second region. Also, an apparatus is described including a demultiplexer that produces a first and second bitstream, a first encoder that encodes the first substream using a low density parity check coding process at a first encoding rate, a second encoder that encodes the second substream at a second rate, and a symbol mapper that maps bits from the first substream to a first region of a symbol constellation map and maps bits from the second substream to a second region.