Multicarrier Coding With Shell Mapping Across Varying SNR
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Solution Overview
Problem
Existing communication technologies face challenges in achieving high data rates and reliability, particularly in copper wire-based systems, due to varying channel quality and inefficiencies in error correction schemes optimized for low or high signal-to-noise ratios.
Innovation Solution
A coding and modulation scheme utilizing probabilistic constellation shaping, combined with LDPC encoding and Reed-Solomon coding, adapts bit allocations to channel quality, partitioning constellations into shells to optimize performance across varying SNR regions, and employs a shell mapper to enhance efficiency and reduce error propagation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional error correction schemes optimized for low or high SNR regions are used, then performance is improved in those specific regions, but performance deteriorates in other SNR regions
Solution Approach 1:
The patent applies dynamics by making the error correction scheme adaptive rather than static. The LDPC code rate and constellation size are dynamically adjusted based on the measured SNR of each carrier, allowing the system to optimize performance across varying channel conditions. This is achieved through iterative decoding where the decoder provides feedback about channel quality, enabling the encoder to adapt the coding parameters for subsequent transmissions.
Solution Approach 2:
The patent changes key parameters (LDPC code rate and QAM constellation size) based on channel conditions. Different LDPC code rates (e.g., 1/2, 2/3, 3/4) are selected depending on the SNR region, and constellation sizes are adjusted accordingly. This parameter adaptation allows the system to achieve optimal performance across low, medium, and high SNR regions rather than being optimized for a single region.
2Productivity
If higher data rates are pursued through increased modulation complexity, then throughput is improved, but reliability and error correction capability deteriorate
Solution Approach 1:
The patent segments the data stream and applies different coding rates to different segments based on channel conditions. By dividing the transmission into multiple carriers with different modulation schemes and coding rates, the system can achieve high overall data rates while maintaining reliability through lower-order modulations and stronger error correction on more challenging carriers.
Solution Approach 2:
The patent uses a composite approach combining multiple error correction codes (LDPC and Reed-Solomon) with multiple modulation schemes (QAM constellations of different sizes). This composite coding and modulation strategy allows the system to achieve high data rates while maintaining robust error correction capability through the synergistic combination of different techniques.
3Ease of manufacture
If uniform error correction is applied across all carriers, then implementation is simplified, but performance is suboptimal for carriers with varying channel quality
Solution Approach 1:
The patent applies local quality by using different error correction parameters for different carriers based on their individual channel quality. Each carrier can have its own LDPC code rate and constellation size optimized for its specific SNR conditions. This per-carrier optimization improves overall system performance while the modular structure keeps implementation complexity manageable.
Data Source
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.