SCMA Codebook Constellation Radial Distance Optimization
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Solution Overview
Problem
The design of Sparse Code Multiple Access (SCMA) codebooks for uplink communications faces challenges in robust performance due to amplitude and phase misalignment among different user equipment (UE) layers, which affects the efficiency and accuracy of multiple access in wireless communication systems.
Innovation Solution
The proposed solution involves creating an SCMA codebook with a constellation of points in the complex plane, where the first grouping of constellation points is located at a first radial distance from the origin and the second grouping at a second radial distance, with Gray coding between non-zero entries, ensuring improved performance under amplitude and phase misalignment. This design optimizes the shape of the constellation to enhance the robustness of the SCMA codebook by reducing the normalized distance of points from a chosen reference point.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional SCMA codebooks are used with uniform constellation points, then the system is simpler to implement, but performance degrades under amplitude and phase misalignment in uplink communications
Solution Approach 1:
The patent applies local quality by assigning different radial distances to different groups of constellation points within the codebook. Specifically, the codebook is divided into multiple groups where each group has constellation points at a specific radial distance from the origin. This local differentiation in radial positioning enhances robustness against amplitude and phase misalignment while maintaining a structured, manageable codebook design.
Solution Approach 2:
The patent changes the parameter of radial distance for different constellation point groups. By varying the radial distance parameter across different groups of constellation points, the codebook achieves improved performance under amplitude and phase misalignment. This parameter variation allows the system to better handle uplink communications where different users may have varying channel conditions.
2Productivity
If multi-dimensional codebooks are used to improve spectral efficiency, then overloading capacity increases, but detection complexity increases
Solution Approach 1:
The patent applies segmentation by organizing the multi-dimensional codebook into multiple groups of constellation points, where each group is associated with specific non-zero entries. This segmentation allows the detector to process different groups separately, reducing overall detection complexity while maintaining the spectral efficiency benefits of multi-dimensional codebooks and overloading capacity.
Solution Approach 2:
The patent utilizes another dimension by extending the codebook structure to multiple dimensions with different radial distances. This dimensional extension enables the system to achieve higher spectral efficiency and overloading capacity while the structured grouping across dimensions provides a framework for managing detection complexity through organized processing.
3Reliability
If constellation points are grouped at different radial distances, then robustness against misalignment improves, but the codebook structure becomes more complex
Solution Approach 1:
The patent applies local quality by assigning different radial distances to different groups of constellation points within the codebook. Specifically, the codebook is divided into multiple groups where each group has constellation points at a specific radial distance from the origin. This local differentiation in radial positioning enhances robustness against amplitude and phase misalignment while maintaining a structured, manageable codebook design.
Solution Approach 2:
The patent applies asymmetry by using non-uniform radial distances for different constellation point groups. Instead of placing all constellation points at the same distance from the origin, the codebook uses asymmetric radial positioning where different groups have different radial distances. This asymmetric structure improves performance under misalignment conditions while maintaining a systematic organization that manages structural complexity.
Data Source
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AI summary
Disclosed are methods and apparatus used in wireless communications. The methods and apparatus establish a codebook for use in sparse code multiple access (SCMA) encoded communications, in particular. The SCMA codebook is configured to set the codebook for at least one layer (i.e., a user) to include a constellation of points having a first grouping of constellation points located at first radial distance from an origin in a complex plane and a second grouping of constellation points located at a second radial distance from the origin. This codebook arrangement provides increased gains at receivers by optimizing the constellation shape to improve the distance between constellation points (i.e., SCMA codebook performance), and in particular more robust performance when encountering amplitude and phase misalignment in uplink (UL) multiple access.