Shared Likelihood Generation Circuit Using 8QAM Phase Rotation
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Solution Overview
Problem
The circuit scale of likelihood generation circuits increases proportionally with the number of supported modulation schemes, particularly in adaptive modulation systems like 8QAM and QPSK, due to the need for separate implementations for each scheme.
Innovation Solution
A likelihood generation circuit that shares components by using a phase rotation adjustment part to rotate symbols on a constellation diagram, allowing a single circuit to handle both 8QAM and QPSK modulation schemes, with separate likelihood generation parts for determining whether symbols are on the inner or outer circle, reducing the overall circuit scale.
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 maintained, but the circuit scale increases proportionally with 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 phase rotation adjustment to transform 8QAM symbols into configurations that can be processed by the same likelihood generation logic used for QPSK, thereby eliminating the need for separate dedicated circuits for each modulation scheme while maintaining accuracy.
Solution Approach 2:
The patent changes the phase parameter of the received symbols through phase rotation adjustment. By rotating the phase of 8QAM symbols by specific angles (0, 90, 180, or 270 degrees) based on the quadrant information, the circuit transforms the symbol configuration to match the QPSK likelihood generation requirements, enabling the same circuit to process different modulation schemes with different parameters.
2Speed
If likelihood generation circuits are implemented in parallel to secure real-time operation, then the real-time property is improved, but the number of multipliers increases leading to larger circuit scale
Solution Approach 1:
The unified likelihood generation circuit processes both 8QAM and QPSK signals through the same parallel processing structure. Instead of having separate parallel circuits for each modulation scheme, the circuit uses phase rotation adjustment followed by a single set of parallel likelihood generation units, reducing the total number of multipliers while maintaining real-time processing capability.
Data Source
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.