Adaptive CRC Length Selection for 3GPP NR UCI Reliability
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Solution Overview
Problem
The existing cyclic redundancy check (CRC) length used in LTE networks is insufficient for the larger uplink control information (UCI) sizes in 3GPP New Radio (NR) networks, which can range from 1 bit to 500 bits, necessitating an adaptive solution for effective error detection and correction.
Innovation Solution
An adaptive length CRC method is implemented, where the CRC polynomial length is determined based on the amount of data to transmit, with different lengths used for data less than or equal to a threshold number of bits and greater than that threshold, and a portion of the length is allocated for error correction and another portion for error detection, utilizing Polar codes or LDPC codes as needed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the existing CRC length of 8 bits is used for LTE UCI, then the error detection capability is sufficient for LTE UCI sizes, but the CRC length is insufficient for NR UCI sizes ranging from 1 bit to 500 bits
Solution Approach 1:
The patent implements dynamic CRC length selection by determining the CRC polynomial length based on the amount of data to transmit. The system adapts between different CRC lengths (e.g., 8 bits for small data, 16 bits for medium data, 24 bits for large data) according to the actual UCI size, making the error detection capability dynamically matched to the data volume rather than using a fixed length.
Solution Approach 2:
The patent changes the parameter of CRC polynomial length based on transmission requirements. By selecting different polynomial lengths (8, 16, or 24 bits) according to the data size category, the system optimizes the balance between error detection capability and overhead, ensuring sufficient reliability for each specific transmission scenario.
2Reliability
If a longer CRC polynomial length is used to cover larger UCI sizes, then the error detection capability improves, but the CRC overhead increases
Solution Approach 1:
The patent optimizes the parameter of CRC polynomial length by selecting from discrete values (8, 16, or 24 bits) based on data size categories. This prevents unnecessary use of longer CRC lengths for small data transmissions, thereby reducing overhead while maintaining sufficient error detection capability for each specific data volume.
Solution Approach 2:
The system dynamically adjusts CRC length to match the actual transmission needs. By determining the appropriate CRC polynomial length based on the amount of data to transmit, the system ensures that CRC overhead is minimized while still providing adequate error detection capability for the specific UCI size being transmitted.
3Device complexity
If a fixed CRC length is used for all data sizes, then the system complexity is reduced, but the error detection capability becomes insufficient for varying UCI sizes
Solution Approach 1:
The patent introduces dynamic CRC length selection with determination logic that assesses data size and selects appropriate polynomial length. While this adds some complexity, it uses structured decision-making (comparing data size against thresholds) to achieve adaptability, balancing the increased complexity against the significant improvement in error detection capability for varying UCI sizes.
Data Source
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AI summary
The present application relates to the adaptation of the CRC length in the context of 3GPP NR. In a first step, the maximum uplink control information (UCI) size is determined. Then, this maximum UCI size is scaled with a scaling factor F that is greater than zero but smaller than or equal to 1. The CRC length L is obtained as the minimum integer 2**(L-1)-L-1 that is greater than or equal to F*(maximum UCI size) and relates to a CRC code having a generator polynomial of the form g(x) = (x+1)*b(x), wherein b(x) is primitive polynomial of length L-1. The determined CRC code is of length N=2**(L-1)-1 with information length N-L.