HARQ Feedback Timing Adjustment for Semi-Persistent Scheduling
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Solution Overview
Problem
In 5G wireless communication systems, the use of inapplicable HARQ feedback timing indications (e.g., NN-K1 values) can lead to out-of-order (OOO) HARQ processes and inefficient data transmission, particularly in unlicensed spectrum where frame structuring is floating due to LBT procedures, causing issues with semi-persistent scheduling (SPS) and dynamic scheduling combinations.
Innovation Solution
A method where user equipment (UE) receives a first downlink control signal activating SPS with applicable HARQ feedback timing, and upon determining an inapplicable timing for subsequent data transmissions, adjusts the HARQ feedback timing based on a subsequent downlink control signal with a numerical K1 value, ensuring timely and ordered HARQ feedback.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If inapplicable HARQ feedback timing indications (NN-K1 values) are used for downlink data transmissions, then flexibility in unlicensed spectrum operations is improved, but out-of-order HARQ processes occur causing transmission inefficiency
Solution Approach 1:
The network entity transmits a first downlink control signal activating SPS with applicable HARQ feedback timing before transmitting downlink data with inapplicable timing indications. This preliminary action establishes a default timing reference that the UE can use to determine HARQ feedback timing even when subsequent control signals contain NN-K1 values, preventing OOO HARQ processes while maintaining flexibility for unlicensed spectrum operations
Solution Approach 2:
The patent introduces an intermediary mechanism where the first downlink control signal acting as SPS activation serves as a mediator between the network's flexible scheduling needs and the UE's HARQ feedback timing determination. This intermediary provides a stable reference point (applicable HARQ feedback timing) that resolves the conflict between using inapplicable timing indications for flexibility and maintaining ordered HARQ processes for efficiency
2Productivity
If semi-persistent scheduling is combined with dynamic scheduling in unlicensed spectrum, then resource utilization is improved, but frame structuring becomes unstable due to LBT procedures
Solution Approach 1:
The patent applies dynamics by allowing the HARQ feedback timing indication to transition between states. The first downlink control signal provides a stable initial configuration, while subsequent dynamic scheduling can use inapplicable timing indications (NN-K1) that allow flexibility. The UE determines the actual timing based on the stable reference from the first control signal, enabling the system to be both dynamic in scheduling and stable in HARQ feedback timing, thus maintaining resource utilization while coping with LBT-induced frame structure variations
3Ease of operation
If applicable HARQ feedback timing is provided in SPS activation, then HARQ feedback timing determination is simplified, but subsequent inapplicable timing indications create confusion for the UE
Solution Approach 1:
The first downlink control signal providing applicable HARQ feedback timing serves as a preliminary action that establishes a clear reference before any inapplicable timing indications are introduced. This preliminary timing information is stored by the UE and used as the basis for determining HARQ feedback timing when subsequent control signals contain NN-K1 values, preventing confusion while maintaining ease of operation
Solution Approach 2:
The patent implements a feedback mechanism where the UE uses the initially provided applicable HARQ feedback timing as a reference to interpret subsequent inapplicable timing indications. This feedback loop ensures that even when timing information appears missing or inapplicable in later control signals, the UE can still determine the correct feedback timing by referencing the initial configuration, thus preventing information loss and maintaining clarity
Data Source
AI summary
A method may include receiving, by a user equipment from a network entity, a first downlink (DL) control signal activating semi-persistent scheduling (SPS) of a first set of downlink data transmissions, the downlink control signal indicating an applicable hybrid automatic repeat request (HARQ) feedback timing for the first set of downlink data transmissions and receiving one or more of the first set of downlink data transmissions. The user equipment may determine that an applicable HARQ feedback timing for a second set of downlink data transmission previously received with an inapplicable HARQ feedback timing has not been provided. In response to the determination, the user equipment may determine a HARQ feedback timing for the one or more of the first set of downlink data transmissions based a second DL control signal indicating an applicable HARQ feedback timing received after reception of the one or more of the first set of downlink data transmissions.