HARQ Feedback Timing Adaptation for 5G NR-U Scheduling
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Solution Overview
Problem
In wireless communication systems, particularly in 5G NR-U, the existing HARQ feedback mechanism faces inefficiencies due to limitations in representing timing values, leading to unnecessary retransmissions and potential loss of access to the medium, especially with higher subcarrier spacing values.
Innovation Solution
The proposed solution involves configuring HARQ feedback in user equipment (UE) to identify and transmit feedback information in specific uplink slots based on a PDSCH-to-HARQ_feedback timing indicator, allowing for flexible timing representation by grouping slots and adjusting the bitwidth of the timing indicator field, thereby supporting a wider range of timing values within a channel occupancy time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the existing HARQ feedback mechanism is used with higher subcarrier spacing values, then the system can support higher data rates, but the limitation in representing timing values causes unnecessary retransmissions and loss of access to the medium
Solution Approach 1:
The patent makes the HARQ feedback timing mechanism dynamic by introducing slot grouping where the timing indicator field can represent different timing values based on the group configuration. Instead of a fixed timing representation, the system dynamically adapts the timing values based on the configured groups, allowing flexible adjustment to support higher subcarrier spacing while maintaining accurate timing representation.
Solution Approach 2:
The patent changes the parameters of the timing indicator field by adjusting its bitwidth and the number of groups. By modifying these parameters, the system can represent a wider range of timing values needed for higher subcarrier spacing operations, thereby resolving the contradiction between supporting high data rates and maintaining feedback accuracy.
2Device complexity
If the timing indicator field uses fixed bitwidth, then the system structure remains simple, but it cannot represent all necessary timing values for higher subcarrier spacing
Solution Approach 1:
The patent segments the timing representation into multiple groups, where each group can be configured with specific timing values. This segmentation allows the system to maintain a relatively simple fixed bitwidth structure while achieving enhanced adaptability through the group-based configuration approach.
Solution Approach 2:
The timing indicator field is designed to serve multiple functions by working with different group configurations. The same field structure can represent different timing values depending on the configured groups, providing universality and versatility without increasing the fundamental bitwidth complexity.
3Productivity
If HARQ feedback timing is not accurately represented, then the system can maintain simple scheduling, but unnecessary retransmissions occur and medium access is lost
Solution Approach 1:
The patent implements an enhanced feedback mechanism where the HARQ timing indicator provides accurate timing information through group-based configuration. This improved feedback ensures that retransmissions are scheduled at the correct time, preventing unnecessary medium access loss and reducing retransmission delays while maintaining efficient scheduling.
Data Source
AI summary
A user equipment (UE) receives physical downlink shared channel (PDSCH) in a downlink slot as scheduled using a downlink control indicator (DCI). The UE identifies that the downlink slot is part of a group of downlink slots based on the DCI and/or another DCI corresponding to the group. The UE identifies one or more uplink slots at which to transmit hybrid automatic repeat request (HARQ) feedback corresponding to the slots in the group, and transmits the HARQ feedback at one of these uplink slots. If HARQ feedback is not received, a semi-static codebook may prevent HARQ payload size misalignment.