CBG Feedback Verification via CRC Scrambling in 5G NR
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In 5G NR networks, unreliable code block group (CBG) level feedback leads to incorrect decoding and retransmission of code block groups, resulting in failed decoding of CBGs due to errors in acknowledging feedback at the base station.
Innovation Solution
The method involves a user equipment (UE) transmitting code block group feedback and a cyclic redundancy check (CRC) in one slot, and receiving and comparing it with a CRC scrambled by the base station in a subsequent slot to determine correct decoding, allowing for accurate retransmission management and avoiding incorrect LLR combination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If CBG level feedback is used to improve retransmission efficiency, then retransmission management is improved, but feedback reliability deteriorates due to decoding errors at the base station
Solution Approach 1:
The patent implements a feedback verification mechanism where the base station sends back a verification signal containing a CRC scrambled by the received CBG feedback. The UE compares this with a locally generated CRC to determine if the base station correctly decoded the feedback. This feedback-loop feedback verifies the reliability of the initial CBG feedback, resolving the contradiction by maintaining retransmission efficiency while ensuring feedback accuracy.
Solution Approach 2:
The patent introduces a CRC verification mechanism as an intermediary to mediate between the UE and base station. This intermediary verification step checks whether the CBG feedback was correctly decoded without requiring additional dedicated feedback resources, thus maintaining retransmission efficiency while improving feedback reliability.
2Measurement precision
If CBG feedback verification is implemented to improve decoding accuracy, then decoding success rate is improved, but system complexity increases due to additional CRC generation and comparison
Solution Approach 1:
The patent makes the existing CRC mechanism multi-functional by using it both for its traditional error detection purpose and for verifying CBG feedback decoding accuracy. The same CRC generation and comparison functionality serves dual purposes, improving decoding accuracy without adding separate verification systems, thus limiting the increase in system complexity.
Solution Approach 2:
The UE performs self-verification by comparing the received CRC with a locally generated CRC. This self-service approach allows the UE to verify feedback decoding accuracy using its own resources and capabilities, reducing the need for additional network infrastructure or complex centralized verification systems.
3Reliability
If incorrect CBG feedback is transmitted due to decoding errors, then retransmission accuracy is improved, but wrong LLR combination occurs leading to failed decoding
Solution Approach 1:
The patent applies preliminary anti-action by preemptively verifying CBG feedback decoding accuracy before the base station uses it to generate retransmission signals. The UE checks if the feedback was correctly decoded and can prevent wrong LLR combination by identifying decoding errors early, thus maintaining retransmission accuracy and avoiding harmful wrong LLR combinations.
Solution Approach 2:
The patent performs preliminary verification of CBG feedback decoding status before retransmission occurs. By checking the CRC match in advance, the system prepares the correct state for retransmission, ensuring that LLR combination will be performed on accurate feedback data, thus preventing wrong LLR combination and ensuring retransmission accuracy.
Data Source
AI summary
Aspects of the present disclosure relate to techniques for retransmission of code block groups when code block group (CBG) level feedback is unreliable. A user equipment (UE), in a first slot, transmits a first CBG feedback corresponding to a first set of CBGs received from a base station. In a second slot after the first slot, the UE receives downlink control information (DCI) and a first cyclic redundancy check (CRC). The first CRC is generated based on the DCI and further scrambled by a first concatenation of CBG feedbacks as decoded by the base station. The UE generates a second CRC based on the DCI and further scrambled by a second concatenation of CBG feedbacks including the first CBG feedback. The UE determines that the base station correctly decoded the first CBG feedback based on a comparison of the first CRC and the second CRC.