Adaptive TTI Configuration for Flexible HARQ Feedback
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Solution Overview
Problem
Modern wireless networks face challenges in accommodating diverse traffic types with different latency requirements due to fixed transmission time intervals (TTIs), which lead to inflexible latency and throughput performance, particularly in LTE and WiMAX TDD systems where HARQ feedback delays are variable and influenced by downlink and uplink configurations.
Innovation Solution
The implementation of adaptive TTIs allows for flexible HARQ feedback delays by configuring different TTI lengths within the same system, enabling dynamic signaling overhead adjustments based on traffic characteristics, and incorporating TTI splitting to reduce control channel overhead and accommodate varying latency requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If fixed length TTIs are used, then system simplicity is maintained, but flexibility for diverse traffic characteristics with different latency requirements deteriorates
Solution Approach 1:
The patent segments the TTI structure by introducing multiple TTI lengths (short TTI and long TTI) within the same system. Different TTIs can be configured with different lengths (e.g., 0.5ms, 1ms, 2ms, 4ms, 8ms, 16ms) to accommodate different traffic types. This segmentation allows the system to handle both low-latency traffic (using short TTI) and high-throughput traffic (using long TTI) simultaneously, resolving the contradiction between system simplicity and traffic adaptability.
Solution Approach 2:
The patent implements dynamic TTI configuration where the TTI length can be adjusted based on traffic characteristics. The system can dynamically switch between different TTI lengths and configurations to match real-time network conditions and service requirements. This dynamic approach enables the system to adapt to diverse traffic patterns while maintaining operational simplicity through standardized configuration mechanisms.
2Adaptability or versatility
If variable HARQ feedback delay is used in LTE TDD, then flexibility for different DL:UL traffic ratios is improved, but latency predictability deteriorates
Solution Approach 1:
The patent changes the TTI length parameter to control HARQ feedback delay. By configuring different TTI lengths, the system can adjust the HARQ feedback timing to meet specific latency requirements. For example, shorter TTIs result in shorter feedback delays, while longer TTIs provide more flexible DL:UL ratios. This parameter-based control allows simultaneous optimization of both flexibility and latency predictability.
3Productivity
If longer TTIs are used, then throughput efficiency is improved, but latency requirement for diverse traffic deteriorates
Solution Approach 1:
The patent segments traffic handling into different TTI length categories. Long TTIs (e.g., 4ms, 8ms, 16ms) are used for throughput-intensive traffic to maximize spectral efficiency and reduce overhead. Short TTIs (e.g., 0.5ms, 1ms) are used for latency-sensitive traffic to minimize delay. This segmentation enables the system to optimize throughput efficiency for appropriate traffic types without compromising latency requirements.
Data Source
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AI summary
In one embodiment, a method for adaptive transmission time intervals (TTIs) includes transmitting, by a communications controller to a user equipment (UE), a segment of a first TDD TTI configuration of a first TDD interval and a second TDD TTI configuration of the first TDD interval, where the first TDD TTI configuration has a first pattern, where the second TDD TTI configuration has a second pattern, where the first pattern is different than the second pattern, where the first TDD TTI configuration has a first uplink TTI segment and a first downlink TTI segment,. The method also includes transmitting a first plurality of data on a first TTI in the first downlink TTI segment of the first TDD TTI configurations of the first TDD interval and receiving a second plurality of data on the first uplink segment of the first TDD TTI configuration of the first TDD interval.