Pruned Polar Encoding Graphs for Flexible Low-Latency Decoding
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Solution Overview
Problem
The decoding complexity of polar codes increases with block-length, limiting their adoption for high-throughput applications like 5G NR eMBB data rates, and existing methods for flexible code rate and size are impractical due to high memory requirements and complexity.
Innovation Solution
A method involving the generation of a pruned factor graph and corresponding parity-check matrix for polar encoding and decoding, which reduces connections and complexity, allowing for flexible code rates and sizes without the need for separate pruning processes for each instance, and enables efficient decoding through LDPC-like BP decoding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If polar codes are used for high-throughput applications with increased block-length, then data rate and throughput are improved, but decoding complexity increases
Solution Approach 1:
The factor graph is segmented into multiple levels (e.g., 5 levels for N=32) with variable nodes and check nodes organized hierarchically. This segmentation allows the decoding process to be divided into manageable stages, reducing the overall decoding complexity while maintaining support for high block-lengths and data rates
Solution Approach 2:
The patent implements dynamic pruning of the factor graph where check nodes are selectively removed based on their connection patterns. The pruning process dynamically adapts the graph structure to eliminate unnecessary computations, thereby reducing decoding complexity while preserving the essential error correction functionality for high-throughput applications
2Adaptability or versatility
If flexible code rates and sizes are implemented, then adaptability is improved, but memory requirements and complexity increase
Solution Approach 1:
The pruned factor graph structure serves as a universal framework that can accommodate multiple code rates and block sizes through systematic pruning. By removing check nodes based on connection patterns rather than creating separate graphs for each code configuration, the system achieves multi-functionality with reduced memory requirements
Solution Approach 2:
The patent changes the structural parameters of the factor graph through pruning operations, where check nodes are removed based on their degree (number of connections). This parameter change approach allows flexible code rates and sizes to be achieved by modifying the graph structure rather than storing multiple complete graphs, thereby reducing memory requirements while maintaining adaptability
3Reliability
If complete factor graphs are used for accurate decoding, then decoding accuracy is improved, but decoding latency increases
Solution Approach 1:
Check nodes that contribute minimally to decoding accuracy are extracted and removed from the factor graph through systematic pruning. By identifying and removing check nodes with specific connection patterns (e.g., check nodes connected to already-pruned variable nodes), the patent reduces the number of computations required during decoding, thereby reducing latency while preserving sufficient decoding accuracy for practical applications
Data Source
AI summary
A method performed by a WTRU may comprise generating a polar factor graph and pruning the polar factor graph to generate a pruned factor graph. The pruned factor graph may include input variable nodes, check nodes and output variable nodes. The method may further comprise the initializing input variable nodes. For each of a plurality of encoding levels of the pruned factor graph, values from the input variable nodes may be transferred to the check nodes. Operations, for example, XOR) additions, may be performed on the values of the check nodes. Check nodes having a single connection to another node not used in a previous transfer may be identified. Values from the identified check nodes may be transferred to the input variable nodes. Binary values from the input variable nodes may be transferred to the output variable nodes for transmission to a receiver.