LDPC Constellation Mapping With Unequal Bit Protection
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Solution Overview
Problem
Low-density parity-check (LDPC) coding does not provide optimal performance when used with higher order modulation constellation mapping, such as 16-QAM, 64-QAM, and 256-QAM, due to inherent inequity in bit reliability within the modulation constellation, leading to performance degradation in error protection.
Innovation Solution
The implementation of parallel LDPC coding and symbol mapping processes that demultiplex data streams into substreams, encoding them using different coding rates, and mapping bits from these substreams to specific regions of a symbol constellation map to address the reliability inequity, thereby improving overall coding performance and efficiency for higher order modulation formats.
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 protection deteriorate due to bit reliability inequity within the modulation constellation
Solution Approach 1:
The patent divides the data stream into multiple substreams and applies different LDPC coding rates to different portions of the modulation constellation. Specifically, it segments the constellation into regions with different bit reliabilities and assigns appropriate coding rates to each region, thereby resolving the contradiction between maintaining high transmission rates and ensuring adequate error protection for all bits.
Solution Approach 2:
The patent applies different coding rates to different regions of the modulation constellation based on the local reliability characteristics of bits in each region. Bits in more reliable constellation regions receive lower coding rates (less protection), while bits in less reliable regions receive higher coding rates (more protection), optimizing the overall system performance by matching protection levels to local needs.
2Productivity
If higher order modulation constellation mapping is used, then bandwidth efficiency is improved, but error protection performance deteriorates due to inherent inequity in bit reliability
Solution Approach 1:
The patent makes different parts of the modulation constellation have different error protection characteristics by assigning different LDPC coding rates to different constellation regions. This allows the system to maintain high bandwidth efficiency through higher order modulation while providing differentiated error protection that compensates for the inherent bit reliability inequity in each region.
Solution Approach 2:
The patent changes the coding rate parameter dynamically based on the modulation constellation region. By adjusting the LDPC coding rate parameter according to the specific constellation mapping and bit reliability characteristics, the system optimizes error protection performance while maintaining the bandwidth efficiency benefits of higher order modulation.
Data Source
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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 (210) that produces a first and second substream, a first encoder (220) that encodes the first substream using a low density parity check coding process at a first encoding rate, a second encoder (222) that encodes the second substream at a second rate, and a symbol mapper (240) 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.