Variable-Length PAC Coding for Short-Payload Wireless Transmission
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Solution Overview
Problem
Current channel coding techniques, such as LDPC codes, are not optimal for short payload sizes and have high error floors, which limits their performance in future ultra-reliable low latency communication (URLLC) scenarios. Additionally, existing polar codes do not efficiently adapt to varying payload sizes in wireless communications.
Innovation Solution
The implementation of Polarization-Adjusted Convolutional (PAC) codes with variable lengths, which involve a transform based on specific index sets and a convolution transform, to adapt to different payload sizes in wireless communications, thereby improving transmission efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If LDPC codes are used for channel coding, then the coding structure is simple and decoding is efficient, but the error floor is high and performance is poor for short payload sizes
Solution Approach 1:
The patent combines LDPC convolutional codes with polar codes to create a hybrid coding scheme that achieves both the structural simplicity of LDPC codes and the low error floor performance of polar codes. The combined approach uses LDPC convolutional encoding for its simple iterative decoding structure while incorporating polar code principles to reduce error floors in short payload scenarios
Solution Approach 2:
The patent employs a composite coding structure that integrates two different coding techniques (LDPC and polar codes) into a unified system. This composite approach allows the system to leverage the strengths of both coding methods while mitigating their individual weaknesses, particularly for short payload sizes where traditional LDPC codes fail
2Reliability
If traditional polar codes are used, then the coding performance is good for long payloads, but they do not efficiently adapt to varying payload sizes in wireless communications
Solution Approach 1:
The patent implements a dynamic polar coding scheme where the code parameters, block length, and rate matching configurations can be dynamically adjusted based on the actual payload size. This allows the system to optimize coding performance for each specific transmission scenario rather than using fixed parameters designed for long payloads
Solution Approach 2:
The patent changes key parameters of the polar code including block length N, code rate R, and rate matching configuration based on the payload size. By varying these parameters adaptively, the system maintains high coding performance whether the payload is short or long, resolving the contradiction between performance and adaptability
3Productivity
If variable length PAC codes are implemented, then transmission efficiency for varying payload sizes is improved, but decoding complexity increases
Solution Approach 1:
The patent segments the decoding process into multiple stages: first performing rate matching reversal to recover the encoded bit sequence, then performing polar decoding. This segmentation allows the system to handle variable length payloads efficiently while managing decoding complexity through a structured multi-step approach rather than a single complex operation
Data Source
AI summary
Methods, apparatus, and systems that relate to Polarization-Adjusted Convolutional (PAC) coding with variable lengths are disclosed. In one example aspect, a method for digital communication includes determining, by a first node, an output bit sequence having E bits based on an input bit sequence having K bits. The output bit sequence is determined based on a transform that is applied prior to applying a Polar transform having a size of N. The transform is based on at least one index set that is a subset of a set of bit indices. The set of bit indices comprises all non-negative integers that are less than N and wherein K<N and K<E. The method also includes transmitting, by the first node, a signal including the output bit sequence to a second node.