Flexible Sparse Code Multiple Access Codebook Design
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Solution Overview
Problem
Current multiple access techniques, such as CDMA and SCMA, face challenges in achieving high throughput while maintaining efficient multi-dimensional modulation and reducing computational complexity, especially in next-generation wireless networks with diverse application scenarios and multi-user multiplexing requirements.
Innovation Solution
The method involves applying forward error correction (FEC) encoding to input bits, mapping them to binary streams, and using layer-specific modulators to generate independent complex-valued symbol streams, which are transmitted using sparse resource elements defined by unique signatures, allowing for flexible spectral efficiency and reduced decoding complexity through tone-by-tone demodulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional CDMA encoding is used, then relatively high throughput is achieved, but computational complexity increases and flexibility for next-generation scenarios is limited
Solution Approach 1:
The patent segments the codebook into layer-specific codebooks, where each codebook is associated with a specific data layer and uses a dedicated spreading sequence. This segmentation allows each layer to be decoded independently with reduced complexity, while maintaining high throughput through efficient resource utilization across multiple layers.
Solution Approach 2:
The patent introduces dynamic codebook selection and layer-specific spreading sequences that can be adapted to different communication scenarios. The system dynamically assigns spreading sequences and codebooks based on channel conditions and data requirements, providing flexibility for next-generation wireless scenarios while managing computational resources efficiently.
2Productivity
If SCMA with multidimensional codebooks is used, then spectral efficiency is improved, but decoding complexity increases and receiver performance degrades
Solution Approach 1:
The patent divides the multidimensional codebook into separate layer-specific codebooks, each with its own spreading sequence. This segmentation transforms the complex joint decoding problem into multiple independent decoding problems, one for each layer, significantly reducing receiver complexity while preserving spectral efficiency through efficient use of time-frequency resources.
Solution Approach 2:
The patent extracts the spreading sequence from the codebook structure, making it a separate, layer-specific component. This extraction allows the spreading sequence to be optimized independently for each layer, simplifying the receiver's task of separating and decoding each layer without requiring complex joint optimization across all dimensions.
3Device complexity
If low density spreading is used, then decoding complexity is reduced, but throughput is limited compared to conventional CDMA
Solution Approach 1:
The patent merges multiple low-density spreading layers into a single multi-layer system, where each layer uses its own spreading sequence and codebook. This merging allows the system to achieve the throughput benefits of conventional CDMA by utilizing multiple layers simultaneously, while maintaining the decoding simplicity of low-density spreading through independent layer processing.
Data Source
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AI summary
Forward error correction encoding is applied to a first stream of input bits associated with a first data layer to generate a first stream of coded bits. The first steam of coded bits is mapped to K1 binary streams. A first layer-specific set of stream-specific modulators are applied to the K1 binary streams to generate K1 independent complex-valued symbol streams. The symbol streams are transmitted using T1 resource elements out of N1 resource elements. The T1 resource elements are defined by a first layer-specific signature of length N1, where 1≤ T1<N1. The same process may also be carried out for a second stream of input bits associated with a second data layer using a second layer-specific set of stream-specific modulators and a second layer-specific signature, which may differ from the first layer-specific signature in terms of sparsity pattern and/or sparsity level.