Shortened TTI for Wireless Communication Delay Reduction
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Solution Overview
Problem
Current radio communication systems, such as LTE Rel. 8 to 12, face challenges in providing adequate communication services at high frequencies and small data amounts, particularly in IoT and MTC applications, due to the fixed 1ms transmission time interval (TTI), which results in increased processing delays and limited capacity.
Innovation Solution
Implementing a shortened TTI, configured with OFDM or SC-FDMA symbols, which can be shorter than 1ms, to reduce processing delays and increase capacity, while maintaining compatibility with existing systems by adjusting the number of symbols and subcarrier intervals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If a transmission time interval (TTI) of 1ms is used, then compatibility with existing LTE systems is maintained, but processing delays increase and communication service quality deteriorates in future radio communication systems
Solution Approach 1:
The patent applies dynamics by making the TTI length variable rather than fixed. The base station dynamically adjusts the TTI length based on communication requirements, allowing switching between 1ms (for compatibility) and shorter durations (for reduced delay). This enables the system to adapt TTI characteristics to different service scenarios, resolving the contradiction between maintaining compatibility and reducing processing delays.
2Productivity
If a shortened TTI is implemented, then communication service quality and capacity are improved, but system complexity increases due to multiple TTI configurations
Solution Approach 1:
The patent segments the communication system into different TTI configuration modes. By dividing the system into distinct TTI length options (1ms and shorter), each segment can be independently optimized for specific service requirements. This segmentation allows the system to handle different communication scenarios with appropriate TTI lengths without requiring complete system redesign, thus improving capacity while managing complexity through modular configuration.
Solution Approach 2:
The patent changes the TTI length parameter to optimize system performance. By adjusting this key time parameter, the system can improve communication capacity and reduce delays for future radio communication systems. The base station controls and notifies user terminals of TTI length changes, enabling parameter optimization without fundamentally altering system architecture, thereby balancing performance improvement with complexity management.
3Speed
If carrier aggregation is used to achieve broadbandization, then data rates are increased, but the fixed 1ms TTI limits the ability to provide low delay services
Solution Approach 1:
The patent applies dynamics by enabling flexible TTI length adjustment within the carrier aggregation framework. While carrier aggregation maintains high data rates through multiple component carriers, the dynamic TTI configuration allows the system to use shorter TTIs when low delay is required. This dynamic adaptation resolves the contradiction by allowing the system to optimize both speed (through carrier aggregation) and delay (through adjustable TTI length) based on service requirements.
Data Source
Figure 1
Figure 2A~2B
Figure 3A~3C
AI summary
According to the present invention, communication is carried out using a transmission time interval (TTI) that is suitable for a future radio communication system. A user terminal of the present invention includes a receiving section configured to receive a downlink signal; a transmitting section configured to transmit an uplink signal; and a control section configured to control a transmission time interval (TTI) used in reception of the downlink signal and/or used in transmission of the uplink signal. The control section sets a second transmission time interval (TTI) that is shorter than a 1ms first transmission time interval (TTI).