One Shot HARQ-ACK Codebook Generation via NDI Comparison
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Solution Overview
Problem
In 3GPP 5G New Radio (NR) systems, there is a misunderstanding between User Equipment (UE) and Base Station (BS) regarding HARQ-ACK feedback, leading to missed data transmissions due to incorrect interpretation of HARQ-ACK codebooks, especially when UE reports ACK for a given HARQ process but misses new DL assignments, causing the BS to assume the ACK corresponds to new data and not retransmitting it.
Innovation Solution
The proposed solution involves generating HARQ-ACK feedback based on New Data Indicator (NDI) bits and HARQ-ACK information bits, with a dedicated DCI triggering one-shot HARQ-ACK feedback for all configured DL HARQ processes, using bit-level operations like addition or subtraction to ensure accurate feedback transmission and reception, and reusing DCI fields to minimize overhead and prevent lost retransmission opportunities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If UE transmits one-shot HARQ-ACK feedback for all configured DL HARQ processes, then HARQ-ACK feedback coverage is improved, but misunderstanding between BS and UE occurs leading to missed data transmissions
Solution Approach 1:
The patent introduces an intermediary mechanism using NDI bit comparison as a mediator to resolve the misunderstanding between BS and UE. The UE compares the NDI bit in the received DCI with the stored NDI bit for each HARQ process before generating HARQ-ACK feedback. This intermediary comparison step prevents the BS from misinterpreting ACK feedback as corresponding to new data, thereby eliminating the information loss while maintaining comprehensive feedback coverage.
2Loss of energy
If BS assumes ACK corresponds to new data and does not retransmit, then retransmission overhead is reduced, but new data is lost due to UE missing the new DL assignment
Solution Approach 1:
The patent applies preliminary action by having the UE perform NDI bit comparison before generating HARQ-ACK feedback. The UE stores the NDI bit from the latest DCI and compares it with the NDI bit in the current DCI. If the NDI bit has toggled, the UE knows new data is being scheduled and generates appropriate feedback. This preliminary NDI comparison prevents the BS from making incorrect assumptions, ensuring new data is not lost while avoiding unnecessary retransmissions.
3Quantity of substance
If DCI fields are reused for NDI bits, then signaling overhead is minimized, but DCI field functionality may be compromised
Solution Approach 1:
The patent applies universality by making DCI fields serve multiple functions. The same DCI fields are used both for their original scheduling purposes and for conveying NDI bit information for HARQ-ACK feedback generation. The NDI bits are extracted from existing DCI fields rather than requiring separate dedicated fields, achieving multi-functionality that reduces signaling overhead while maintaining the reliability of DCI field functionality through careful bit interpretation and comparison logic.
Data Source
AI summary
The subject disclosure relates to a method and apparatus for determining a one shot HARQ-ACK codebook. In one embodiment, the subject disclosure provides a method performed by a User Equipment (UE), including receiving, from a base station (BS), a signaling configuring a plurality of Downlink (DL) Hybrid Automatic Repeat reQuest (HARQ) processes, and Downlink Control Information (DCI) requesting HARQ-ACK feedback for each of the plurality of DL HARQ processes; for each of the plurality of DL HARQ processes, generating the HARQ-ACK feedback based on an associated New Data Indicator (NDI) bit and HARQ-ACK information bit; and transmitting, to the BS, a HARQ-ACK codebook comprising the HARQ-ACK feedback for each of the plurality of DL HARQ processes.