LDPC-Coded SCMA Access Scheme With Segmented Encoding
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Solution Overview
Problem
The deployment of Low Density Parity Check (LDPC) codes is hindered by complexity in encoding, high storage requirements, and complexity in communication between processing nodes, as well as the need for efficient error control in satellite communication systems with limited bandwidth and power constraints.
Innovation Solution
The implementation of a Scrambled Division Multiple Access (SDMA) and Spread Scrambled Division Multiple Access (SSDMA) scheme using LDPC encoding, which simplifies encoding and decoding processes, reduces storage needs, and enhances communication efficiency by employing low code rates and spectral spreading.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If LDPC encoding is implemented using generator matrix, then encoding capability is provided, but storage requirements increase due to large non-sparse matrix
Solution Approach 1:
The patent segments the LDPC code into multiple sub-blocks, where each sub-block is encoded independently using a smaller generator matrix. This segmentation reduces the storage requirements from a single large non-sparse matrix to multiple smaller matrices, while maintaining the overall encoding capability through the structured arrangement of sub-blocks.
Solution Approach 2:
The patent applies local quality by making different parts of the code (sub-blocks) have different encoding characteristics. Each sub-block can use optimized local generator matrices tailored to specific requirements, reducing overall storage needs while maintaining global encoding performance.
2Reliability
If LDPC codes are used to approach Shannon limit, then error control performance improves, but decoder design complexity increases
Solution Approach 1:
The decoder is segmented into multiple processing units that handle different sub-blocks independently. This segmentation reduces the complexity of each individual decoder unit while maintaining the overall error control performance that approaches the Shannon limit, as each unit processes a manageable portion of the code.
Solution Approach 2:
The patent employs dynamic decoding strategies where the decoding process adapts to the specific characteristics of received sub-blocks. This dynamic approach optimizes the trade-off between error control performance and decoder complexity by adjusting processing intensity based on actual channel conditions.
3Reliability
If LDPC codes are deployed in satellite communication, then transmission reliability improves, but computational load in decoding process increases
Solution Approach 1:
The patent segments the decoding computational load across multiple independent sub-block processors. Each processor handles a portion of the decoding task with reduced computational requirements, while the overall system maintains high transmission reliability through the combined processing of all sub-blocks.
Solution Approach 2:
The patent applies partial action by processing sub-blocks independently and selectively, allowing the system to achieve sufficient decoding performance without the excessive computational load of processing the entire code block simultaneously. This partial processing approach reduces energy consumption while maintaining acceptable reliability.
4Adaptability or versatility
If CDMA technique is used for satellite communication, then multiple users can share bandwidth, but bandwidth expansion factor increases
Solution Approach 1:
The patent segments the CDMA system into multiple access sub-blocks, where each user's data is divided into sub-blocks that are encoded and spread independently. This segmentation reduces the overall bandwidth expansion factor required for multiple user access while maintaining the capability for multiple users to share the bandwidth simultaneously.
Data Source
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Figure 1B
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AI summary
A multiple access scheme is described. One or more encoders are configured to encode a plurality of bit streams using Low Density Parity Check (LDPC) coding. The bit streams correspond to a respective plurality of terminals. The plurality of bit streams are converted to provide a multiple access scheme for the terminals.