Co-Orthogonal Multi-Stream Spreading for Wireless Coding Efficiency
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Solution Overview
Problem
Conventional CDMA encoding techniques face limitations in achieving higher coding rates necessary for next-generation wireless networks, and existing low density spreading (LDS) and sparse code multiple access (SCMA) methods have room for improvement in terms of coding efficiency and complexity reduction.
Innovation Solution
The method involves mapping input symbols to K symbols using a symbol-to-resource-element mapping, where K symbols are transmitted over T OFDM tones, employing co-orthogonal mappings and sparse signatures to optimize resource utilization and reduce decoding complexity, while maintaining high coding rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional CDMA encoding is used, then relatively high coding rates are achieved, but the coding rate is insufficient for next-generation wireless networks
Solution Approach 1:
The patent transitions from conventional two-step CDMA encoding to a unified multi-dimensional mapping approach where input bits are directly mapped to multidimensional codewords. This dimensional expansion enables higher coding rates by efficiently utilizing multiple dimensions (time, frequency, space) simultaneously, achieving coding rates necessary for next-generation networks while maintaining reliability through the structured multi-dimensional codebook design.
2Device complexity
If low density spreading (LDS) is used, then decoding complexity is reduced, but coding efficiency has room for improvement
Solution Approach 1:
The patent changes the fundamental parameters of spreading by transitioning from simple repetition of QAM symbols in LDS to direct bit-to-multidimensional-codeword mapping. This parameter change in the mapping process enables higher coding efficiency while the structured codebook design and sparse nature of the mapping maintain reduced decoding complexity, resolving the trade-off between efficiency and complexity.
3Reliability
If sparse code multiple access (SCMA) is used, then performance is improved compared to LDS, but coding efficiency can be further optimized
Solution Approach 1:
The patent creates a universal mapping framework that can accommodate multiple access scenarios and modulation schemes. The unified bit-to-multidimensional-codeword mapping approach serves multiple functions: it improves coding efficiency through optimized codebook design, maintains SCMA's performance benefits, and provides a flexible foundation that can be adapted to different network conditions and requirements, thereby optimizing coding efficiency while preserving performance.
4Ease of manufacture
If simple repetition of QAM symbols in LDS is used, then implementation is simple, but coding rate is limited
Solution Approach 1:
The patent segments the encoding process into distinct mapping stages where input bits are systematically mapped to multidimensional codewords with specific structures. This segmentation allows the system to achieve higher coding rates through the structured approach while maintaining implementation simplicity by breaking down the complex mapping into manageable, standardized steps that can be efficiently implemented.
Data Source
Figure 1A~1B
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AI summary
Systems and methods are provided for spreading symbols over multiple time-frequency resources that rely on simple base constellations that can be sent over a frequency tone or time slot. A set of input bits (or an input symbol) are mapped to K symbols, and a symbol-to-resource-element mapping is applied that maps the K symbols to resource units. The mapping to the K symbols may be a linear mapping that maps an input symbol to K target tones through a 2K ×2 real matrix, where input symbol is a complex point in a base constellation, and is considered as a 2-dimensional real vector. Up to K co-orthogonal 2K × 2 real matrices (whose columns are orthogonal to each other) can be associated with the subset of K target tones. Each of the K co-orthogonal matrices can be used for mapping of an independent symbol from a separate steam of symbols which can be associated to a single UE or separate UEs.