Shared Likelihood Generation Circuit for 8QAM and QPSK
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Solution Overview
Problem
The existing likelihood generation circuits for soft decision error correction decoding face an increase in circuit scale when supporting multiple modulation schemes, such as 8QAM and QPSK, due to the need for separate implementations for each scheme, leading to inefficient use of resources.
Innovation Solution
A likelihood generation circuit is designed to share components across different modulation schemes by incorporating a phase rotation part, a likelihood generation part, and a modulation scheme selection part, allowing for reduced circuit scale by utilizing smaller-scale circuits for phase rotation, addition, and minimum value selection, and enabling the sharing of circuits between 8QAM and QPSK.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If separate likelihood generation circuits are implemented for each modulation scheme (8QAM and QPSK), then the likelihood generation accuracy for each scheme is improved, but the circuit scale increases proportionally to the number of supported modulation schemes
Solution Approach 1:
The patent implements a universal likelihood generation circuit that can handle multiple modulation schemes (8QAM and QPSK) through a single unified structure. The circuit uses modulation scheme selection signals to dynamically configure its operation mode, allowing the same hardware to perform likelihood generation for different modulation types without requiring separate dedicated circuits for each scheme.
Solution Approach 2:
The circuit employs dynamic configuration based on modulation scheme selection signals. The likelihood generation circuit can switch between different operational modes (8QAM mode or QPSK mode) depending on the input signal type, enabling adaptive operation that optimizes performance for the current modulation scheme while maintaining a compact fixed hardware structure.
2Productivity
If likelihood generation circuits are implemented in parallel to secure real-time operation, then the real-time processing capability is improved, but the number of multipliers increases leading to larger circuit scale
Solution Approach 1:
The patent segments the likelihood generation process into distinct functional stages that can be executed sequentially within a unified circuit. By dividing the calculation into manageable segments (such as separating the 8QAM-specific calculations from QPSK calculations based on modulation type), the circuit achieves real-time processing without requiring full parallel implementation for all operations simultaneously.
Solution Approach 2:
The circuit changes its operational parameters based on the modulation scheme selection. When processing 8QAM signals, the circuit configures itself for 8QAM-specific calculations; when processing QPSK signals, it reconfigures for QPSK calculations. This parameter-based adaptation allows the single circuit to handle different modulation types efficiently without requiring parallel hardware for each configuration.
Data Source
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AI summary
A phase of a symbol on an inner or outer circle of a received 8QAM symbol set, which is bitmapped by being assigned one bit depending on whether the symbol is on the inner or outer circle of a constellation mapping diagram and two bits for each of the quadrants, is rotated to generate, by QPSK likelihood generation, along with a likelihood of a received QPSK modulation symbol, a likelihood for the two bits assigned to the quadrant of the 8QAM modulated symbol set whose phase is rotated. Further, the phase-rotated 8QAM modulated symbol set is phase-rotated to the first quadrant of the diagram to move the symbol set to the QPSK symbol mapping positions, thereby generating, by QPSK likelihood generation, the likelihood for the one bit assigned to represent whether the symbol is on the outer circle or the inner circle of the 8QAM modulated symbol set.