TDD HARQ Feedback Timing Optimization for Ultralow Delay
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Solution Overview
Problem
Current HARQ systems in TDD wireless communication systems face significant delays, exceeding the required ultralow delay thresholds of 1 ms in industrial and automated driving applications due to complex feedback mechanisms and subframe structures.
Innovation Solution
The proposed solution involves sending feedback messages in a Kth subframe after the initial data transmission subframe, reducing HARQ feedback complexity and shortening ACK/NACK feedback times by optimizing the subframe structure to include both uplink and downlink symbols, thereby reducing overall HARQ delay.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional HARQ feedback mechanism is used in TDD system, then feedback reliability is ensured, but transmission delay increases beyond 1ms requirement
Solution Approach 1:
The patent segments the feedback timing by introducing multiple feedback timing options (first feedback timing and second feedback timing) based on different uplink-downlink configuration types. This allows the system to divide the feedback process into different time paths, enabling shorter delay for certain configurations while maintaining reliability through structured feedback mechanisms.
Solution Approach 2:
The patent dynamically adjusts feedback timing based on the uplink-downlink configuration type. The terminal device determines whether to use first or second feedback timing according to the specific configuration, making the feedback mechanism adaptive rather than fixed. This dynamic adjustment enables the system to optimize delay performance for different TDD configurations while ensuring feedback reliability.
2Loss of time
If HARQ round-trip time is reduced to meet 1ms delay requirement, then transmission delay is improved, but processing time for data receiving becomes insufficient
Solution Approach 1:
The patent applies preliminary action by having the terminal device determine the feedback timing in advance based on the uplink-downlink configuration type before actual feedback transmission. The network device also prepares accordingly by knowing which timing to expect. This advance determination optimizes the timing relationship and ensures sufficient processing time is allocated before feedback is actually sent, preventing processing bottlenecks.
Solution Approach 2:
The patent changes the feedback timing parameter based on the uplink-downlink configuration type. By having different feedback timing values for different configuration types, the system can adjust the processing time duration to match the specific TDD configuration, ensuring adequate processing time while minimizing overall HARQ round-trip time.
3Speed
If feedback timing is optimized for speed, then transmission delay is reduced, but feedback mechanism complexity increases
Solution Approach 1:
The patent applies local quality by having different feedback timing characteristics for different uplink-downlink configuration types. Each configuration type has its own optimized feedback timing (first or second timing), allowing local optimization for each configuration scenario rather than using a single complex unified mechanism. This reduces overall system complexity while maintaining fast feedback speed for each specific case.
Data Source
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AI summary
Embodiments of the present invention provide an information feedback method. User equipment UE detects downlink transmission data in a received subframe. The UE sends a response message for the downlink transmission data to the access network device, where the response message is sent by the UE on an uplink symbol in a Kth subframe after the received subframe, K is the same for any subframe arrangement in a TDD system, and K is a positive integer. The embodiments of the present invention are applied to the TDD system. An ACK or NACK feedback time is reduced, thereby greatly reducing a HARQ delay and meeting a transmission requirement for an ultralow delay.