Soft Decision Value Circuit with Sign Reflection for DEQPSK

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Solution Overview

Problem

Existing soft decision value generation circuits for differentially encoded modulation schemes, such as DEQPSK, require significant hardware and computational resources due to the need for extensive error calculations and Euclidean distance calculations, leading to large circuit scales and high power consumption, especially when implemented in digital LSI or FPGA.

Innovation Solution

A soft decision value generation circuit that includes phase rotation, addition, minimum value selection, and sign reflection units to simplify the calculation of soft decision values, reducing the computational load and hardware requirements by restricting soft decision value candidates and using sign inversion and addition/subtraction processing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If the general principle of soft decision value calculation is applied to DEQPSK, then accurate soft decision values can be obtained, but the calculation amount becomes large and hardware scale increases

Engineering Contradiction:

Improvesoft decision value accuracyVSAvoidcircuit scale

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent segments the calculation process into two distinct parts: (1) calculation of absolute values of soft decision values using simplified arithmetic operations, and (2) determination of signs based on phase information. This segmentation allows each part to be optimized independently, reducing overall computational complexity while maintaining accuracy.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent changes the calculation parameter from complex Euclidean distance calculations to simplified arithmetic operations involving only additions and subtractions. By transforming the mathematical formulation, the patent eliminates the need for multiplication and square root operations, significantly reducing hardware complexity.

Inventive Principle:

Principle #35Parameter changes

2Measurement precision

If extensive error calculations and Euclidean distance calculations are performed, then accurate soft decision values are generated, but power consumption increases

Engineering Contradiction:

Improvesoft decision value accuracyVSAvoidpower consumption

Core Design Contradiction:

Measurement precisionVSUse of energy by moving object

Solution Approach 1:

The patent extracts and separates the sign determination from the magnitude calculation. By taking out the sign information from the complex Euclidean distance calculation and determining it separately through phase comparison, the patent eliminates energy-intensive operations while preserving the accuracy required for soft decision values.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent replaces expensive computational operations (multiplication, square root) with cheap operations (addition, subtraction, comparison). These simplified operations consume significantly less power and can be implemented using simpler, lower-power hardware circuits.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

3Measurement precision

If multiple modulation symbol candidates are evaluated for each transmitted bit, then accurate soft decision values are obtained, but the calculation amount increases significantly

Engineering Contradiction:

Improvesoft decision value accuracyVSAvoidcalculation efficiency

Core Design Contradiction:

Measurement precisionVSProductivity

Solution Approach 1:

The patent performs preliminary calculation of absolute values for all modulation symbol candidates using a unified simplified formula. By pre-calculating these absolute values before determining signs, the patent avoids redundant calculations and streamlines the overall process, improving calculation efficiency.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent develops a universal calculation formula for absolute values that applies to all modulation symbol candidates regardless of which transmitted bit is being evaluated. This multi-functional approach allows the same computational pathway to serve multiple evaluation purposes, reducing the overall calculation burden.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS8914715B2Soft decision value generation circuit to reduce calculation amounts and hardware scale

Publication Date: 2014.12.16 MITSUBISHI ELECTRIC CORP

AI summary

A soft decision value generation circuit capable of reducing amount of calculation and hardware scale for generating a soft decision value. The soft decision value generation circuit includes: a phase rotation unit rotating phases of received symbols after coherent detection; addition units calculating, by using the phase-rotated received symbols, absolute values of soft decision values for soft decision value candidates restricted in advance; minimum value selection units selecting minimum values out of the absolute values of the soft decision values; sign reflection units reflecting, based on the phases of the received symbols after the phase rotation, sign information to the minimum values; and soft decision value correction units multiplying outputs of the sign reflection units by a coefficient depending on a noise variance value and an amplitude value of a modulation symbol.