Nested Lookup Table for QAM Symbol Detection Candidate Reduction

Solution Overview

Problem

Calculating log-likelihood ratios for maximum likelihood estimation in quadrature amplitude modulation (QAM) is computationally costly, especially for large constellations, necessitating an efficient method for reducing computational complexity.

Innovation Solution

A method and system for selecting initial candidate points using a nested lookup table, where initial modulation estimates are used to identify rows in the lookup table, and candidate points are read, allowing for the calculation of approximate log-likelihood ratios with reduced computational cost by selecting points based on binary word conditions and transformations for quadrant alignment.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If maximum likelihood estimation is performed for all constellation points in large QAM, then measurement precision is improved, but device complexity increases

Engineering Contradiction:

Improvelog-likelihood ratio calculation accuracyVSAvoidcomputational complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The constellation is divided into multiple regions, and the candidate points are segmented into initial candidate points and refined candidate points. This segmentation allows the system to process only relevant subsets of points at each stage, reducing the overall computational burden while maintaining accuracy.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The system performs preliminary action by pre-identifying and storing initial candidate points in lookup tables before the actual log-likelihood ratio calculation. These preliminary candidate points are selected based on region information, so that when detection is needed, the system already has a reduced set of candidates ready, avoiding the need to evaluate all constellation points.

Inventive Principle:

Principle #10Preliminary action

2Reliability

If all constellation points are evaluated for log-likelihood ratio, then reliability is improved, but productivity decreases

Engineering Contradiction:

Improvedetection accuracyVSAvoidprocessing speed

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The system performs preliminary action by pre-identifying and storing initial candidate points in lookup tables before the actual log-likelihood ratio calculation. These preliminary candidate points are selected based on region information, so that when detection is needed, the system already has a reduced set of candidates ready, avoiding the need to evaluate all constellation points.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system dynamically adjusts the candidate point selection process by using refined candidate points that are specifically chosen for each initial candidate point. This dynamic refinement ensures that the most relevant points are evaluated for log-likelihood ratio, maintaining reliability while improving processing speed by avoiding unnecessary evaluations.

Inventive Principle:

Principle #15Dynamics

3Device complexity

If initial candidate reduction is performed using nested lookup tables, then device complexity is reduced, but measurement precision may deteriorate

Engineering Contradiction:

Improvecomputational complexityVSAvoidlog-likelihood ratio accuracy

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The system dynamically adjusts the candidate point selection process by using refined candidate points that are specifically chosen for each initial candidate point. This dynamic refinement ensures that the most relevant points are evaluated for log-likelihood ratio, maintaining reliability while improving processing speed by avoiding unnecessary evaluations.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system replaces the mechanical process of evaluating all constellation points with a lookup table-based approach. Instead of computationally intensive real-time evaluation of all points, the system substitutes this with pre-computed lookup tables that store candidate point information, significantly reducing computational complexity while maintaining accuracy through the refinement process.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentUS11296816B2Nested lookup table for symbol detection with initial candidate reduction

Publication Date: 2022.04.05 SAMSUNG ELECTRONICS CO LTD

AI summary

A method of signal demodulation includes receiving, by a signal receiver, a first signal modulated by a symbol corresponding to a point in a constellation; generating, by the signal receiver and on the basis of the first signal, a modulation estimate; identifying, by the signal receiver and on the basis of the modulation estimate, a row or column of a candidate lookup table, the row or column corresponding to a region of the constellation; reading, by the signal receiver, from the row or column of the candidate lookup table one or more candidate points of the constellation, at least one among the one or more candidate points being more distant, from a center of the region, than a point, in the constellation, not among the one or more candidate points, and demodulating, by the signal receiver and on the basis of the one or more candidate points, the first signal.