User Terminal Feedback Timing Control for Shortened TTI
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Solution Overview
Problem
In future radio communication systems like LTE Rel. 13 and 5G, using a transmission time interval (TTI) of 1 ms may not provide sufficient communication services, especially for high-frequency communications and small data amounts in IoT, MTC, and M2M applications, and shortening TTI poses challenges in controlling retransmission methods.
Innovation Solution
A user terminal and radio base station configuration that controls the feedback timing of delivery acknowledgement signals based on applied TTI, allowing for shortened TTIs shorter than 1 ms, enabling flexible HARQ-ACK feedback and retransmission control by adjusting HARQ RTT and TTI settings for improved throughput.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a shortened TTI is applied to DL and UL transmission, then communication speed and processing efficiency are improved, but retransmission control becomes more complex and difficult to manage
Solution Approach 1:
The patent implements dynamic TTI configuration where the system can switch between normal TTI (1ms) and shortened TTI based on service requirements. The eNB configures different TTI lengths for different user terminals or different component carriers, allowing flexible adaptation to varying communication needs while maintaining manageable retransmission control through configured parameters
Solution Approach 2:
The patent changes the TTI parameter from the fixed 1ms value to variable shortened values (e.g., 0.5ms, 0.25ms) to improve communication speed. By making this parameter changeable and configurable, the system achieves faster communication while the complexity is managed through standardized configuration mechanisms defined in the patent
2Loss of time
If a shortened TTI is applied, then latency is reduced and throughput is improved, but feedback timing control becomes more difficult
Solution Approach 1:
The patent applies preliminary action by having the eNB configure TTI length and feedback timing parameters in advance through RRC signaling or other control channels. This pre-configuration allows the user terminal to know the feedback timing requirements before actual data transmission, simplifying the feedback control process despite using shortened TTIs
Solution Approach 2:
The patent establishes periodic feedback timing patterns where HARQ-ACK feedback is transmitted at regular intervals relative to the shortened TTI. This periodic structure provides predictability and simplifies timing control, allowing the system to achieve low latency through shortened TTIs while maintaining manageable feedback control through established periodic patterns
3Productivity
If shortened TTI is used to accommodate more user terminals per unit time, then system capacity is improved, but synchronization and coordination between terminals become more challenging
Solution Approach 1:
The patent segments the system into multiple independent TTI configurations that can be assigned to different user terminals or component carriers. Each terminal or carrier can operate with its own configured TTI length, allowing the system to accommodate more terminals by dividing resources into manageable segments rather than requiring unified synchronization across all terminals
Solution Approach 2:
The patent creates a universal configuration mechanism that can handle both normal TTI (1ms) and shortened TTI scenarios through the same control framework. The eNB can configure different TTI lengths universally across multiple terminals and carriers using standardized signaling procedures, simplifying synchronization management while maintaining high system capacity
Data Source
Figure 1
Figure 2A~2B
Figure 3A~3C
AI summary
According to the present invention, appropriate communication can be carried out even if a shortened TTI is applied. A user terminal includes a receiving section configured to receive a DL signal, a transmitting section configured to feedback a delivery acknowledgement signal for the DL signal, and a control section configured to control the feedback of the delivery acknowledgement signal. In the case where a second transmission time interval (TTI), which is shorter than a first transmission time interval (TTI) of 1ms, is applied to DL transmission and/or UL transmission, the control section controls a feedback timing of the delivery acknowledgement signal based on the TTI that is applied to the received DL signal.