Window-Based HARQ-ACK Feedback for SPS Uplink Gaps
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Solution Overview
Problem
In 5G wireless communications, Hybrid Automatic Repeat Request (HARQ)-ACK feedback for Downlink Semi-Persistent Scheduling (SPS) operations is often dropped due to mismatches between SPS periodicity and semi-static Time Division Duplexing (TDD) configurations, leading to issues with ultra-reliable and low latency communications.
Innovation Solution
Implementing enhanced HARQ-ACK feedback mechanisms, including window-based HARQ-ACK feedback and DCI formats with a HARQ-ACK Window Indicator Information Element, to ensure timely transmission of HARQ-ACK feedback in available uplink slots, even when corresponding valid slots are not available.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If window-based HARQ-ACK feedback is implemented to ensure timely transmission in available uplink slots, then reliability of HARQ-ACK feedback is improved, but device complexity increases
Solution Approach 1:
The patent implements dynamic HARQ-ACK feedback transmission by allowing the feedback window to adaptively adjust its size and position based on available uplink slots. The window length parameter (K1) is dynamically determined rather than fixed, enabling the system to flexibly accommodate varying uplink availability while maintaining reliable feedback transmission for semi-persistent scheduling operations
Solution Approach 2:
The patent segments the HARQ-ACK feedback transmission into configurable window periods, allowing selective transmission within specific time windows. This segmentation enables the system to divide feedback opportunities into manageable intervals defined by the window length parameter, improving reliability without requiring complete retransmission mechanisms
2Reliability
If HARQ-ACK window length is extended to capture more feedback opportunities, then feedback reliability improves, but latency increases
Solution Approach 1:
The patent introduces configurable parameters including window length and offset values that can be adjusted to optimize the balance between reliability and latency. By changing these parameters dynamically based on traffic requirements and uplink availability, the system can extend the window when reliability is critical or reduce it when low latency is prioritized, without fixed constraints
3Adaptability or versatility
If DCI format with Window Indicator IE is added to trigger Type-4 HARQ-ACK codebook, then adaptability of feedback mechanism improves, but message complexity increases
Solution Approach 1:
The patent implements a feedback triggering mechanism where the Downlink Control Information (DCI) format includes a Window Indicator Information Element that explicitly triggers Type-4 HARQ-ACK codebook transmission. This feedback-based approach allows the network to adaptively request specific feedback types based on current system state, improving versatility while concentrating complexity in controlled signaling events rather than continuous operation
Solution Approach 2:
The Window Indicator IE acts as an intermediary element in the DCI format that mediates between network scheduling decisions and HARQ-ACK feedback requirements. This intermediary structure allows the system to convey complex feedback instructions through a standardized, parseable format without requiring complete redesign of the DCI structure, managing complexity through modular information elements
Data Source
AI summary
Some embodiments include an apparatus, method, and computer program product for enhanced Hybrid Automatic Repeat Request (HARQ)-ACK in a fifth generation (5G) wireless communications system. A user equipment (UE) can receive, during a HARQ-ACK window, a semi-persistent scheduling (SPS) Physical Downlink Shared Channel (PDSCH) transmission or a Physical Downlink Control Channel (PDCCH) transmission corresponding to a SPS PDSCH release. The UE can generate a Hybrid Automatic Repeat Request (HARQ)-ACK information bit corresponding to the reception. The UE can be configured with an offset value, k, and a length, l, of the HARQ-ACK window associated with an uplink transmission slot n, of a Physical Uplink Control Channel (PUCCH) transmission, and determine a starting slot of the HARQ-ACK window as n-k. When a corresponding valid uplink transmission slot is not available, the UE can transmit the HARQ-ACK information bit in the uplink transmission slot n of the PUCCH transmission.