QAM Differential Decoding with MSB Rotation for Phase Noise Tolerance
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Solution Overview
Problem
Existing multilevel differential decoding devices for QAM modulation communication systems face challenges in maintaining phase noise tolerance and circuit operating speed, especially during high-speed transmission, as increasing multilevel degree decreases phase noise tolerance and requires complex circuit configurations to combine differential encoding/decoding with error correction.
Innovation Solution
A multilevel differential decoding device that includes a synchronous detection part for differential encoding on the first two most significant bits, MSB coordinate rotating parts for quadrant information extraction, MSB and LSB symbol likelihood generating parts for independent likelihood generation, and a soft decision error correction decoding part to process the received signal, allowing for coordinate rotation and error correction without increasing circuit complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multilevel modulation degree is increased to improve frequency utilization efficiency and transmission capacity, then transmission capacity is improved, but phase noise tolerance decreases
Solution Approach 1:
The patent segments the N-bit transmission symbol into two independent processing paths: the first two most significant bits (MSB) are processed through differential decoding with coordinate rotation, while the remaining (N-2) less significant bits (LSB) are processed through independent likelihood generating. This segmentation allows the system to maintain phase noise tolerance through differential decoding on MSB while preserving transmission capacity through multilevel modulation on LSB.
2Reliability
If differential encoding is applied to maintain phase noise tolerance, then phase noise tolerance is improved, but circuit complexity increases
Solution Approach 1:
The patent applies differential decoding with coordinate rotation only to the first two most significant bits that are associated with quadrant identification, while the remaining (N-2) less significant bits are processed through independent likelihood generating without coordinate rotation. This localized application of differential decoding maintains phase noise tolerance where it is most needed (quadrant identification) while reducing overall circuit complexity compared to applying differential decoding to all bits.
3Device complexity
If likelihood generating processing is performed separately for MSB and LSB to reduce circuit complexity, then circuit complexity is reduced, but processing accuracy may deteriorate
Solution Approach 1:
The patent changes the processing parameters differently for MSB and LSB: MSB processing uses differential decoding with coordinate rotation based on quadrant information, while LSB processing uses independent likelihood generating without coordinate rotation. This parameter differentiation allows the system to optimize processing accuracy for each bit group according to its characteristics, maintaining overall processing accuracy while reducing circuit complexity through specialized processing paths.
Data Source
AI summary
Differential decoding processing applied to multilevel modulation is accomplished with the circuit scale kept small by including; an MSB coordinate rotating part for performing coordinate rotation based on information of the first two most significant bits of a signal received via a synchronous detection part; an MSB symbol likelihood generating part for generating likelihood with respect to the first two most significant bits after differential decoding, with the use of two sets of bit strings at different points in time for which coordinate rotation has been performed; an LSB symbol likelihood generating part for generating likelihood with respect to less significant bits; and a soft decision error correction decoding part for generating a decoded signal with the use of the likelihood of the first two most significant bits and the likelihood of the less significant bits.