Enhanced Dynamic HARQ Codebook for 5G NR
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Solution Overview
Problem
Current Hybrid Automatic Repeat Request (HARQ) feedback mechanisms in 3GPP New Radio (NR) face challenges such as inefficient band utilization due to failed HARQ feedback transmissions and difficulty in distinguishing between failed Listen Before Talk (LBT) transmissions and missed UCI transmissions.
Innovation Solution
The proposed solution involves enhanced dynamic codebook HARQ feedback, where PDSCH grouping is indicated and used in combination with the fallback DCI format, allowing for retransmission of HARQ feedback and improved handling of multiple PDSCH groups.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If HARQ feedback transmission is subject to LBT procedure, then channel access is controlled, but transmission failure risk increases and band utilization becomes inefficient
Solution Approach 1:
The patent segments HARQ feedback transmissions into multiple opportunities across different slots. Instead of a single one-to-one mapping between PDSCH and feedback, the system allows multiple feedback transmission opportunities, enabling the UE to retry feedback transmission if LBT fails in the first attempt, thus improving reliability without continuously occupying the channel
2Ease of operation
If one-to-one mapping between PDSCH and feedback is used, then feedback timing is simple, but gNB cannot distinguish between failed LBT transmissions and missed UCI transmissions
Solution Approach 1:
The patent introduces a NFI (New Feedback Indicator) bit in the DCI that is set in advance to indicate whether the HARQ feedback is a retransmission or new feedback. This preliminary indication allows the gNB to distinguish between different types of feedback transmissions and understand when a transmission failure occurred, enabling better error detection without complicating the timing mechanism
3Adaptability or versatility
If DAI is wrapped around after reaching highest value, then DAI cycling is achieved, but PDSCH transmission status cannot be accurately tracked
Solution Approach 1:
The patent enhances the DAI mechanism by introducing a counter indication field that provides feedback about the cumulative number of PDSCH transmissions. This additional feedback dimension allows the UE to track the actual transmission status accurately even when the DAI wraps around, preventing loss of information about missed or repeated transmissions
4Device complexity
If fallback DCI format is used without explicit group indication, then DCI simplicity is maintained, but PDSCH grouping cannot be implemented
Solution Approach 1:
The patent makes the DCI format dynamic by allowing the group indication field to be present or absent depending on the DCI type. For enhanced DCI formats, the group indication field is included to enable PDSCH grouping, while fallback DCI formats maintain simplicity without this field. This dynamic adaptation allows the system to support both grouped and ungrouped PDSCH configurations without increasing complexity of all DCI formats uniformly
Data Source
AI summary
Systems and methods are disclosed herein for supporting enhanced dynamic codebook Hybrid Automatic Repeat Request (HARQ) feedback. In one embodiment, a method performed by a wireless communication device comprises receiving, from a base station, downlink control information (DCI) in accordance with a fallback DCI format. The DCI comprises downlink scheduling information that indicates downlink resources allocated for a downlink data channel transmission to the wireless communication device. The fallback DCI format does not include an explicit indication of an identifier of a downlink data channel group of the downlink data channel transmission. The method further comprises attempting to receive and decode the transmission and determining a downlink data channel group for the transmission based on the DCI. The method further comprises generating a dynamic codebook HARQ feedback for the downlink data channel group comprising HARQ feedback for the transmission and transmitting the dynamic codebook HARQ feedback to the base station.