LDPC Base Graph Selection and TB Segmentation for Variable Code Rates
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Solution Overview
Problem
Existing LDPC coding methods face challenges in efficiently handling varying code rates and block sizes, leading to inefficiencies in data transmission and reception, particularly in wireless communication systems.
Innovation Solution
The method involves attaching transport block (TB) level CRC bits, selecting an LDPC base graph based on code rate and TB size, segmenting the TB into code blocks, padding zeros to the last block, attaching CB level CRC bits, and encoding each segment using the selected LDPC base graph, thereby optimizing data transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If LDPC coding is applied to handle varying code rates and block sizes, then error correction capability is improved, but system complexity increases due to multiple base graphs and segmentation requirements
Solution Approach 1:
The patent applies parameter changes by dynamically selecting different LDPC base graphs (BG1, BG2, BG3) based on code rate and transport block size parameters. Each base graph is optimized for specific parameter ranges, allowing the system to adapt to varying code rates (1/3 to 8/9) and block sizes without using a single complex universal graph, thus improving error correction while managing complexity through parameter-based selection
Solution Approach 2:
The patent implements segmentation by dividing large transport blocks into multiple code blocks when the TB size exceeds the maximum code block size. This segmentation allows LDPC coding to handle varying block sizes efficiently by processing smaller manageable segments, each encoded with appropriate base graphs, thereby improving reliability for large data transmissions while maintaining system complexity through structured division
2Reliability
If transport block level CRC bits are attached to all TBs, then error detection capability is improved, but overhead increases for small TB sizes
Solution Approach 1:
The patent applies local quality by differentiating CRC attachment based on transport block size. TBs with size greater than a threshold (e.g., 6000 bits) receive TB-level CRC bits for error detection, while smaller TBs do not. This localized approach ensures robust error detection for large blocks where overhead is negligible, while avoiding unnecessary overhead for small blocks, thus balancing reliability improvement with overhead control
3Adaptability or versatility
If multiple base graphs are used to support different code rates, then adaptability to varying code rates is improved, but selection and configuration complexity increases
Solution Approach 1:
The patent uses parameter changes to select from multiple LDPC base graphs based on code rate and transport block size. Three base graphs (BG1, BG2, BG3) are defined with different properties optimized for specific code rate ranges. The transmitter and receiver both use the same parameters (code rate, TB size) to select the appropriate base graph, providing adaptability across code rates from 1/3 to 8/9 while keeping selection logic simple and symmetric
Solution Approach 2:
The patent applies inversion by having both transmitter and receiver independently select the same base graph using identical parameters (code rate and TB size) without explicit signaling. Instead of the transmitter selecting and signaling the base graph choice to the receiver, both ends use the same selection criteria to arrive at the same configuration, inverting the traditional approach and reducing signaling overhead while maintaining adaptability
Data Source
AI summary
An apparatus and method are described. The apparatus includes a transceiver and processor, which attach transport block (TB) level CRC bits to a TB, select an LDPC base graph (BG) based on a code rate (CR) and TB size of the TB including TB level CRC bits, determine a number of code blocks (CBs) to use for segmenting the TB including TB level CRC bits depending on the selected LDPC BG, determine a single CB size for each of the CBs based on the number of CBs, segment the TB including TB level CRC bits into the CBs based on the number of CBs and CB size, pad zeros to a last CB of the CBs in the segmented TB, attach CB level CRC bits to each CB in the segmented TB, encode each CB in the segmented TB using the selected LDPC base graph, and transmit the encoded CBs.