CBG ACK/NACK Feedback for Punctured 5G NR Retransmissions
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Solution Overview
Problem
Current wireless communication systems, particularly in 5G NR, face challenges in efficiently managing punctured codeblock groups (CBGs) during dynamic resource sharing between Ultra-Reliable and Low-Latency Communications (URLLC) and Enhanced Mobile Broadband (eMBB) transmissions, leading to errors in ACK/NACK feedback and inefficient retransmissions.
Innovation Solution
Implementing a method that uses single bit ACK/NACK feedback for CBG-based transmissions, allowing retransmissions of only affected CBGs and providing a CBG list in retransmission grants to manage punctured resources effectively, thereby reducing overhead and improving decoding accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multi-bit ACK/NACK feedback is used for CBG-based transmissions, then retransmission accuracy is improved, but feedback overhead and system complexity increase
Solution Approach 1:
The patent extracts the CBG-level acknowledgment information from a multi-bit feedback structure and represents it using a single bit by leveraging the puncturing indication. Instead of transmitting separate ACK/NACK bits for each CBG, the system only needs to indicate whether the punctured CBGs were successfully decoded, reducing feedback overhead while maintaining retransmission accuracy.
Solution Approach 2:
The single bit feedback mechanism serves multiple functions: it acknowledges receipt of the transport block, indicates decoding status of punctured CBGs, and triggers appropriate retransmission actions. This multi-functional approach eliminates the need for complex multi-bit feedback structures while achieving the same communication goals.
2Reliability
If retransmission of all CBGs is performed upon receiving NACK, then reliability is improved, but air link resource efficiency deteriorates
Solution Approach 1:
The patent segments the transport block into multiple CBGs and enables independent retransmission of only the failed punctured CBGs rather than retransmitting the entire transport block. This segmentation allows selective retransmission, improving air link resource efficiency while maintaining reliability by ensuring all necessary data is eventually delivered.
Solution Approach 2:
The system applies different retransmission strategies based on the local condition of each CBG. Only the punctured CBGs that failed decoding are retransmitted, while successfully decoded CBGs are not retransmitted. This localized approach optimizes resource usage by transmitting only the necessary data segments.
3Loss of time
If punctured resources are used for URLLC transmissions, then latency is reduced, but eMBB transmission reliability deteriorates
Solution Approach 1:
The patent implements a feedback mechanism where the UE reports back to the gNB whether the punctured CBGs were successfully decoded. This feedback enables the gNB to make informed decisions about retransmissions, ensuring that eMBB data is reliably delivered even when URLLC traffic punctures allocated resources. The feedback loop maintains reliability while allowing latency-critical URLLC transmissions to proceed.
Solution Approach 2:
The system performs preliminary actions by indicating to the UE which CBGs are affected by puncturing before the UE attempts decoding. This allows the UE to prepare appropriate feedback responses and enables the gNB to proactively manage retransmissions, reducing the need for additional round-trip delays and maintaining both latency and reliability performance.
Data Source
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AI summary
Various features related to a single bit ACK/NACK feedback for CBG based transmissions in a communication system are described. In an aspect, a base station may transmit, to a UE, a set of CBGs of a TB including a first subset of CBGs and a second subset of CBGs, the first subset of CBGs being transmitted on at least partially punctured resources. The base station may receive an ACK/NACK from the UE based on the transmitted set of CBGs, and retransmit to the UE one of the full set of CBGs or the first subset of CBGs based the received ACK/NACK. In an aspect, a UE may decode the set of CBGs received from the base station, transmit ACK/NACK feedback based on a result of the decoding, and receive, based on the transmitted ACK/NACK feedback, a retransmission of either the full set of CBGs, or the first subset of CBGs.