Multicarrier Coding With Constellation Shaping for High-SNR Links
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Solution Overview
Problem
Current communication systems, particularly those using copper wires, face challenges in achieving high efficiency in high SNR regions due to error correction coding schemes being optimized for low channel quality, and the application of FEC schemes like LDPC is problematic due to varying channel quality along the frequency spectrum.
Innovation Solution
The implementation of a communication system that uses probabilistic constellation shaping combined with LDPC coding and Reed-Solomon codes, allowing for adaptable bit allocations based on channel quality and efficient noise processing, which includes a shell mapper and QAM modulator to optimize performance across different SNR regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional FEC schemes like LDPC are used, then error correction capability is improved, but performance degrades in high SNR regions due to optimization for low channel quality
Solution Approach 1:
The patent implements dynamic bit allocation across multiple carriers where the number of bits per carrier is adjusted based on channel quality measurements. This allows the system to optimize transmission efficiency for each carrier's specific SNR conditions while maintaining robust error correction where needed, resolving the contradiction between reliability and productivity across different channel conditions.
Solution Approach 2:
The patent applies different modulation and coding schemes to different carriers based on their individual channel qualities. High SNR carriers use higher-order modulation with fewer redundancy bits, while low SNR carriers use lower-order modulation with more redundancy, allowing each part of the system to operate at its optimal quality level rather than using a uniform approach.
2Device complexity
If uniform bit allocation is used across all carriers, then system complexity is reduced, but transmission efficiency decreases due to varying channel quality along the frequency spectrum
Solution Approach 1:
The patent divides the frequency spectrum into multiple carriers and applies independent bit allocation to each carrier based on its channel quality. This segmentation allows the system to optimize transmission efficiency for each frequency component separately, achieving high overall productivity without requiring complex centralized optimization, as each carrier can be independently configured.
3Productivity
If higher order modulation is used to increase throughput, then data rate is improved, but error rate increases in low SNR regions
Solution Approach 1:
The patent changes the modulation parameter (order of QAM) dynamically for each carrier based on measured channel quality. Carriers with high SNR use higher-order modulation (e.g., 64-QAM, 256-QAM) to achieve high data rates, while carriers with low SNR use lower-order modulation (e.g., QPSK, 16-QAM) to maintain low error rates, thus resolving the contradiction between throughput and reliability.
Data Source
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AI summary
A multi-carrier transmitter apparatus is disclosed. The apparatus includes an outer encoder, a shell mapper and an inner encoder. The outer encoder is configured to receive a signal, perform error correction using an outer code on the received signal and generate an outer encoder signal. The shell mapper is configured to perform constellation shaping on a subset of bits from the outer encoder signal and generate one or more constellation shaping bits. The inner encoder is configured to perform inner error correction/encoding using an inner code on a second subset of bits from the outer encoder signal and generate an inner correction signal.