NR LDPC Base Graph Selection to Limit Code Block Segmentation
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Solution Overview
Problem
The existing proposal for selecting base graph #2 (BG2) for code rates just below 1/3 in new radio (NR) wireless communication systems results in poorer performance compared to base graph #1 (BG1) due to increased code block segmentation and shorter block lengths, especially for transport block sizes greater than 3840.
Innovation Solution
Instead of always selecting BG2 for code rates less than 1/3, the method determines a threshold (R_threshold) between 1/5 and 1/3, and selects BG2 only if the code rate is below this threshold, otherwise choosing BG1, to optimize performance by avoiding unnecessary code block segmentation and leveraging the coding gain of BG2 for significant performance gains.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If base graph #2 (BG2) is selected for code rates just below 1/3, then the coding gain of BG2 can be utilized, but code block segmentation is increased and block lengths are shortened resulting in poorer performance
Solution Approach 1:
The patent changes the parameter threshold for base graph selection from a fixed code rate of 1/3 to a configurable threshold R_threshold (where 1/5 < R_threshold < 1/3). This allows optimization of the trade-off between coding gain and segmentation overhead by adjusting the threshold based on specific communication conditions, thereby improving overall system performance without excessive segmentation.
2Adaptability or versatility
If base graph #2 (BG2) is selected for all code rates below 1/3, then lower code rate support is achieved, but transport block size is limited to 3840 requiring segmentation for larger blocks
Solution Approach 1:
The patent introduces dynamic base graph selection where the choice between BG1 and BG2 depends on the relationship between code rate R and threshold R_threshold, as well as transport block size TBS. When R ≤ R_threshold and TBS ≤ 3840, BG2 is selected for its coding gain; otherwise BG1 is selected to avoid segmentation. This dynamic approach adapts to different transmission conditions optimally.
3Productivity
If base graph #1 (BG1) is used for code rates above 1/3, then larger transport blocks can be transmitted without segmentation, but coding gain is reduced for lower code rates
Solution Approach 1:
The patent applies different base graphs to different operating conditions: BG2 is used locally when code rate R ≤ R_threshold and TBS ≤ 3840 to maximize coding gain, while BG1 is used for other conditions to ensure efficient transmission without segmentation. This localized optimization based on specific parameter ranges resolves the contradiction between coding gain and transmission efficiency.
Data Source
AI summary
According to some embodiments, a method for use in a wireless transmitter of encoding a transport block comprises, upon determining a code rate for transmitting a transport block is less than or equal to R_threshold (R_threshold is between 1/5 and 1/3), selecting new radio (NR) low-density parity-check (LDPC) base graph 2 for encoding the transport block. The method further comprises encoding the transport block using the selected base graph and transmitting the encoded transport block to a wireless receiver.