Uplink Grant Optimization in Shortened TTI Wireless Systems
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Solution Overview
Problem
Current wireless communication systems face challenges in reducing packet data latency, particularly in LTE networks, which affects system performance and user experience, especially with the increasing demand for high-data-rate services.
Innovation Solution
The proposed solution involves optimizing uplink transmission scheduling by shortening the Transmission Time Interval (TTI) and reducing processing times, allowing for finer granularity in transport block sizes and reducing unnecessary padding, while also introducing a two-stage DCI design to limit control overhead and support both short and regular TTI lengths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the Transmission Time Interval (TTI) is shortened to reduce latency, then the packet data latency is reduced, but the processing time requirements become more stringent and system complexity increases
Solution Approach 1:
The patent segments the TTI into shorter intervals (e.g., mini-slots with 2, 4, or 7 symbols instead of full 1ms slots), allowing granular control over transmission timing. This segmentation enables reduced latency for time-sensitive data while maintaining standard processing times for non-urgent traffic, thus resolving the contradiction between latency reduction and processing complexity.
Solution Approach 2:
The patent introduces dynamic TTI length adjustment where the TTI can vary between standard slot lengths and shortened mini-slot lengths based on traffic requirements. This dynamic adaptation allows the system to use shorter TTIs only when latency reduction is critical, while maintaining standard TTIs for other traffic, thereby managing processing complexity selectively.
2Productivity
If the TTI is shortened to support high-data-rate services, then the system performance is improved, but the control signaling overhead increases
Solution Approach 1:
The patent merges multiple control signaling functions into unified DCI formats that can schedule both standard slots and mini-slots. By combining scheduling, resource allocation, and TTI length indication into single control messages, the patent reduces the total number of separate control signals needed, thereby reducing overhead while supporting short TTI operations.
Solution Approach 2:
The patent uses parameter changes in existing DCI formats (such as adding a TTI length indicator field or modifying resource allocation fields) to support short TTIs without introducing entirely new control signaling structures. This approach allows the system to adapt to varying TTI lengths while minimizing the increase in control overhead.
3Loss of substance
If the transport block size is optimized with finer granularity, then the padding is reduced, but the scheduling complexity increases
Solution Approach 1:
The patent applies local quality by allowing different transport block sizes and granularities at different locations in the transmission hierarchy. Specifically, it enables fine-grained TB sizing for short mini-slot transmissions where padding would be significant, while maintaining coarser granularity for standard slot transmissions. This localized optimization reduces overall padding without requiring complex scheduling across all transmission types.
Data Source
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AI summary
A method and apparatus are disclosed for performing uplink transmission in a wireless communication system. Preferably, the method includes the UE monitors a plurality of occasions for a DL control channel within a DL data region within one subframe, wherein a first control channel in a first occasion corresponds to a first UL data channel with a first duration, and wherein a second control channel in a second occasion corresponds to a second UL data channel with a second duration.