TDD HARQ Feedback Coordination Across Short and Long TTIs
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Solution Overview
Problem
Existing wireless communication systems face delays and reduced performance due to improper timing between data reception and feedback transmission, particularly in time division duplexing (TDD) configurations, which can be exacerbated by the use of short transmission time intervals (TTIs).
Innovation Solution
Implementing efficient hybrid automatic repeat request (HARQ) timing and feedback coordination in TDD systems by scheduling short-duration TTIs within or overlapping longer TTIs, adjusting feedback timing based on UE capabilities and timing advance conditions, and utilizing special subframes for HARQ feedback transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If short TTIs are used for data reception, then transmission speed is improved, but feedback timing coordination becomes more complex and latency increases
Solution Approach 1:
The patent applies dynamics by making the TTI length configurable and adaptable rather than fixed. The system can dynamically switch between short TTIs for high-speed transmission and longer TTIs for feedback coordination, optimizing the balance between transmission speed and feedback timing complexity based on current operational requirements
Solution Approach 2:
The patent segments the TDD frame structure into multiple subframes with different TTI lengths. Short TTIs are used within subframes for high-speed data transmission, while the overall frame structure maintains longer periodicity for feedback coordination, effectively dividing the time domain to resolve the contradiction between speed and latency
2Productivity
If feedback timing is adjusted to reduce latency, then system performance is improved, but payload size balancing across uplink TTIs becomes more difficult
Solution Approach 1:
The patent applies preliminary action by pre-configuring the TDD frame structure with designated subframes for downlink transmission and uplink feedback. This predetermined structure allows the system to prepare feedback timing and payload distribution in advance, reducing the complexity of real-time payload balancing while maintaining low latency performance
3Adaptability or versatility
If multiple TTI lengths are supported, then transmission flexibility is improved, but frame structure complexity increases
Solution Approach 1:
The patent applies universality by designing a TDD frame structure that can accommodate multiple TTI lengths within a unified framework. The same basic frame structure supports both short and long TTIs, allowing the system to adapt to different transmission requirements without requiring completely separate frame formats, thus reducing the increase in complexity
Data Source
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AI summary
Methods, systems, and devices for wireless communication are described. Data may be received during transmission time intervals (TTIs) that have a short duration relative to other TTIs. The short-duration TTIs may occur within or overlap a longer duration TTI, such as a subframe. Feedback responsive to the data may be generated and assigned for transmission during an uplink TTI according to a feedback timing or delay, which may be selected to reduce latency or balance the payload size of uplink messages sent during the assigned uplink TTI. Data and feedback assignments in short-duration TTIs may be configured based on a time division duplexing (TDD) configuration for some TTIs (e.g., subframes). TTIs that are a Long Term Evolution (LTE) subframe, an LTE slot, and a duration of two LTE symbol periods may be supported. Portions of special TTIs may be used for transmissions according to shorter-duration TTIs.