Flexible Short TTI Control Region for Low Latency LTE
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Solution Overview
Problem
The existing 3GPP LTE system's transmission time interval (TTI) is not suitable for low latency requirements in next-generation wireless communication systems, as it takes longer than 1 ms, which is necessary for achieving faster data rates and lower latency.
Innovation Solution
A flexible short transmission time interval (sTTI) is introduced, allowing for a variable control region structure within the existing TTI, enabling multiple sTTIs with different lengths and frequency allocation, and optimizing the placement of UE-specific reference signals to minimize overhead and ensure compatibility with existing LTE systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If a traditional 1ms TTI structure is used in LTE system, then system compatibility and stability are maintained, but transmission latency cannot meet the low latency requirements of next-generation wireless communication systems
Solution Approach 1:
The patent divides the traditional 1ms TTI into multiple shorter sTTIs (short TTIs), where each sTTI can be independently scheduled and transmitted. This segmentation enables the system to achieve lower latency by transmitting data in smaller time units while maintaining compatibility with the existing LTE frame structure through proper mapping and signaling mechanisms.
Solution Approach 2:
The patent introduces flexible sTTI length configuration that can be dynamically adjusted based on channel conditions, traffic types, and latency requirements. The sTTI duration can be configured as 2, 3, or 4 symbols, allowing the system to adaptively optimize transmission performance while maintaining backward compatibility with LTE systems.
2Productivity
If multiple sTTIs with different lengths are introduced to reduce latency, then transmission speed and latency performance are improved, but control region management and resource allocation complexity increase
Solution Approach 1:
The patent applies different control region configurations to different sTTIs based on their specific requirements. Each sTTI can have its own control region size and structure optimized for its particular traffic type and latency requirement, rather than using a uniform control structure for all sTTIs. This local optimization reduces overall system complexity while improving transmission performance.
Solution Approach 2:
The patent introduces configurable parameters for sTTI length, control region size, and resource allocation that can be adjusted through higher-layer signaling. These parameter changes enable flexible control of multiple sTTIs with different characteristics, allowing the system to manage complexity through standardized parameter interfaces rather than hard-coded complex logic.
3Quantity of substance
If UE-specific reference signals are optimized for sTTI structure, then data channel capacity and beamforming performance are improved, but signal placement overhead and system complexity increase
Solution Approach 1:
The patent nests UE-specific reference signals within the sTTI structure in a hierarchical manner, where reference signals are placed at specific positions within each sTTI that are determined by the sTTI's start position and length. This nested arrangement allows efficient reuse of reference signal patterns across different sTTIs while adapting to varying sTTI configurations, reducing overhead and complexity.
Solution Approach 2:
The patent designs UE-specific reference signals to serve multiple functions simultaneously: channel estimation, beamforming reference, and demodulation reference for both downlink and uplink transmissions. This multi-functionality reduces the need for separate reference signal types and decreases overall overhead while improving data channel capacity and beamforming performance.
Data Source
AI summary
Provided are a method and a device for arranging a subframe structure of a short TTI according to the change in a control region in a wireless communication system. Specifically, a plurality of first downlink channels received during an sTTI and a second downlink channel received during a TTI are received. The number of symbols used for each of the plurality of first downlink channels is determined by a format indicator channel included in the first symbol of a subframe. Further, the plurality of first downlink channels are demodulated by using scheduling information included in each of the plurality of first downlink channels, and the second downlink channel is demodulated by using scheduling information included in a control region indicated by the format indicator channel.