SCMA Codebook Structure With Fewer Projections for Low-Complexity Decoding

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Solution Overview

Problem

Current sparse code multiple access (SCMA) systems face high decoding complexity due to a large number of distinct projections per complex dimension, which hinders efficient data transmission and reception in communication systems.

Innovation Solution

The method involves generating and utilizing codebooks with a smaller number of distinct projections per complex dimension, reducing decoding complexity through multi-dimensional modulation maps and message passing algorithms, while maintaining or improving link performance and spectral efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If a large number of distinct projections per complex dimension are used in SCMA codebooks, then spectral efficiency and data rates are improved, but decoding complexity increases significantly

Engineering Contradiction:

Improvedata rateVSAvoiddecoding complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The codebook is segmented into multiple groups where each group contains codebooks with a limited number of distinct projections per complex dimension. This segmentation allows the system to manage decoding complexity by processing smaller projection sets while maintaining overall spectral efficiency through the use of multiple codebook groups.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention changes the parameter of distinct projections per complex dimension from a large number to a small number (e.g., 1 or 2 distinct projections). This parameter change directly reduces decoding complexity while the system compensates by utilizing multiple codebook groups to maintain spectral efficiency and data rates.

Inventive Principle:

Principle #35Parameter changes

2Device complexity

If codebooks with small number of distinct projections per complex dimension are used, then decoding complexity is reduced, but spectral efficiency may be compromised

Engineering Contradiction:

Improvedecoding complexityVSAvoidspectral efficiency

Core Design Contradiction:

Device complexityVSProductivity

Solution Approach 1:

Multiple codebook groups are merged or combined to compensate for the reduced spectral efficiency of individual codebooks with small projections. Each codebook group contains codebooks with limited distinct projections, but the collective use of multiple groups restores overall spectral efficiency while maintaining low decoding complexity for each group.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The codebook structure is designed to be universal across multiple groups, where each group serves the function of providing low-complexity decoding while the collection of groups provides the multi-functionality needed to maintain spectral efficiency. Different codebook groups can be selected based on channel conditions and traffic requirements.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS10700803B2System and method for generating codebooks with small projections per complex dimension and utilization thereof

Publication Date: 2020.06.30 HUAWEI TECH CO LTD

AI summary

A method for data transmission by a device in a communication system includes modulating a first data stream using a codebook to produce a second data stream, wherein the codebook is in correspondence with a multi-dimensional modulation map that includes a number of distinct projections per complex dimension that is smaller than a number of modulation points of the multi-dimensional modulation map, and transmitting the second data stream over allocated resources in the communication system.