Raptor-Like LDPC Base Graph Switching Across Code-Rate Ranges
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Solution Overview
Problem
Raptor-like LDPC base graphs in 5G communications systems face challenges in ensuring encoding and decoding performance across a wide range of code lengths and code rates, failing to effectively support both high and low code-rate encoding and decoding.
Innovation Solution
A data transmission method that allows a base station to select and indicate a target Raptor-like LDPC base graph to a terminal device from a set of available graphs, based on specific requirements such as code rate, code length, terminal device type, throughput rate, latency, and service type, using modulation and coding scheme (MCS) indexes and lifting factors to optimize LDPC encoding and decoding performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If one Raptor-like LDPC base graph is used to support a wide range of code lengths and code rates, then the versatility of the encoding scheme is improved, but the encoding and decoding performance for specific code blocks cannot be ensured
Solution Approach 1:
The patent divides a single base graph into multiple sub-graphs, each optimized for specific code length and code rate ranges. The base graph is segmented such that different sub-graphs handle different service scenarios (e.g., some sub-graphs optimized for short code blocks, others for long code blocks; some for high code rates, others for low code rates), thereby maintaining both versatility and performance.
Solution Approach 2:
Different sub-graphs are designed with different local qualities tailored to specific requirements. Each sub-graph has optimized column weights, connection patterns, and structural characteristics suited for particular code lengths and code rates, ensuring that the local structure matches the local performance requirements of different service types.
2Device complexity
If a single base graph is used for both high-code-rate and low-code-rate encoding, then the system complexity is reduced, but the performance of both high-code-rate and low-code-rate encoding cannot be ensured
Solution Approach 1:
The base graph is segmented into multiple sub-graphs with different structures optimized for different code rates. The patent specifies that different sub-graphs have different column weight distributions and connection patterns, allowing each to excel at specific code rate ranges while collectively covering the full range from 1/5 to 8/9.
Solution Approach 2:
The system dynamically selects which sub-graph to use based on the actual code rate and code length requirements. The base station determines the appropriate sub-graph according to service requirements and indicates it to the terminal device, enabling adaptive performance optimization without requiring the system to maintain multiple complete base graphs.
3Reliability
If multiple base graphs are used to optimize performance for different code lengths and code rates, then the encoding and decoding performance is improved, but the signaling overhead increases
Solution Approach 1:
The patent merges the base graph selection information with existing MCS (Modulation and Coding Scheme) indexing mechanisms. The base graph index is combined with MCS indexes in a unified table structure, allowing the base graph selection to be indicated alongside modulation and coding parameters without requiring separate dedicated signaling fields.
Solution Approach 2:
The MCS indexing mechanism is given multi-functionality by incorporating base graph selection information into it. The same MCS index that previously only indicated modulation order and code rate now also indicates the base graph to be used, making the signaling structure universal and eliminating the need for additional dedicated base graph indication signaling.
Data Source
AI summary
This application provides a data transmission method, a base station, and a terminal device. The method includes: determining, by a base station, a target base graph in N Raptor-like LDPC base graphs; and sending, by the base station, indication information to a terminal device, where the indication information is used to indicate the terminal device to use the target base graph to perform LDPC encoding and decoding. Based on the foregoing technical solution, the base station may determine a target base graph in a plurality of Raptor-like LDPC base graphs that may be used to perform LDPC encoding and decoding, and indicate the target base graph to the terminal device. Further, for one code rate or one code length, the base station may select different base graphs as required.