5G FDD Subframe Structure for Low Latency HARQ Feedback
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Solution Overview
Problem
Current 5G FDD systems face challenges in reducing latency for ultra-reliable and mission-critical applications due to limitations in subframe structure design, which affects the efficiency of data transmission and feedback mechanisms.
Innovation Solution
The proposed solution involves optimizing the subframe structure in 5G FDD systems by allocating specific configurations for downlink and uplink subframes, allowing for self-contained transmissions where HARQ ACK/NACK feedback is provided within the same subframe, and dynamically adjusting the number of symbols allocated for control and data signals to minimize latency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If traditional subframe structure is used in 5G FDD systems, then system compatibility and standard adherence are maintained, but transmission latency increases and feedback efficiency decreases
Solution Approach 1:
The subframe is segmented into distinct regions including downlink control region, downlink data region, uplink data region, and uplink control region, allowing independent optimization of each segment for low latency transmission while maintaining overall structure compatibility with existing 5G FDD systems
Solution Approach 2:
The subframe structure employs dynamic configuration where the number of symbols allocated to control and data regions can be adjusted based on traffic conditions and latency requirements, enabling flexible adaptation for ultra-reliable low latency communications while preserving standard compliance
2Reliability
If HARQ feedback is provided in subsequent subframes, then processing accuracy is maintained, but feedback time increases and latency accumulates
Solution Approach 1:
The downlink and uplink subframes are merged into a self-contained structure where downlink data transmission and uplink HARQ feedback are contained within the same subframe, eliminating inter-subframe delays while maintaining processing accuracy through adequate guard periods and processing time allocation
Solution Approach 2:
The uplink control region is prepared in advance within the same subframe to receive HARQ feedback, and sufficient processing time is pre-allocated between downlink data reception and uplink feedback transmission, ensuring both accuracy and low latency are achieved simultaneously
3Productivity
If flexible subframe configuration is implemented, then latency is reduced and transmission efficiency improves, but system complexity and configuration overhead increase
Solution Approach 1:
The flexible subframe structure is designed to serve multiple functions including downlink transmission, uplink transmission, control signaling, and HARQ feedback within a unified framework, allowing a single configuration mechanism to handle diverse transmission scenarios without requiring separate complex configuration systems
Solution Approach 2:
The system enables dynamic adjustment of subframe parameters such as the number of downlink symbols, uplink symbols, and control region sizes through standardized signaling mechanisms, allowing transmission efficiency to be optimized by changing parameters rather than restructuring the entire system
Data Source
AI summary
Devices for and methods of providing low latency 5G FDD communications are generally described. A HARQ ACK/NACK for an xPDSCH is transmitted in the xPUCCH of the same or next subframe as the xPDSCH and xPDCCH. An xPUSCH is generated in the same subframe in response to an xPDCCH and HARQ ACK/NACK response is carried by another xPDCCH or xPHICH in the same or next sub frame. The xPDCCH and the xPUCCH are at opposite ends of the same subframe, DL and UL subframe are delayed relative to each other, or at least one of the DL and UL subframe has an additional blank portion, portion with data associated with another UE or portion that contains a reference signal, broadcast signal or control information.