User Terminal Cross-Carrier Scheduling with Mixed TTI Lengths
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Solution Overview
Problem
Future radio communication systems face challenges in scheduling and controlling user data transmission using TTIs of varying time durations, particularly in supporting both long and short TTIs within the same carrier, which is essential for reducing latency and accommodating diverse services like eMBB, mMTC, and URLLC.
Innovation Solution
A user terminal is designed to receive and process downlink control information for both long and short TTIs, allowing for cross-carrier scheduling across multiple cells, enabling proper allocation and transmission of data even when different TTIs are used, by assuming the presence or absence of a carrier indicator in the control information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If multiple TTIs of different time durations are supported in the same carrier, then latency is reduced and diverse services are accommodated, but scheduling and control complexity increases
Solution Approach 1:
The patent segments the TTI structure into long TTI and short TTI types, each with distinct scheduling mechanisms. Long TTIs use traditional scheduling while short TTIs use simplified scheduling, allowing the system to handle different service requirements without overwhelming complexity. This segmentation enables latency reduction for time-sensitive services while maintaining manageable scheduling complexity through differentiated handling.
Solution Approach 2:
The patent implements dynamic TTI selection where the system can adaptively choose between long and short TTIs based on service requirements and channel conditions. This dynamic approach allows the scheduler to optimize latency for URLLC services using short TTIs while using long TTIs for eMBB services, thereby reducing overall latency without requiring complex scheduling for all services simultaneously.
2Productivity
If cross-carrier scheduling is implemented with multiple TTI durations, then resource allocation efficiency is improved, but control information processing complexity increases
Solution Approach 1:
The patent applies local quality by assigning different control information processing rules to different TTI types. Short TTIs use simplified control information with reduced processing requirements, while long TTIs use comprehensive control information. This localized approach to control information design improves resource allocation efficiency across carriers while managing processing complexity through differentiation.
Solution Approach 2:
The patent changes the parameters of control information based on TTI duration. Short TTIs use control information with fewer fields and simplified structures, while long TTIs use control information with complete scheduling details. This parameter adaptation allows efficient cross-carrier scheduling while reducing the processing burden for short TTI scenarios.
3Speed
If short TTIs are used for latency reduction, then response time is improved, but processing overhead increases
Solution Approach 1:
The patent applies partial action by implementing simplified scheduling and control information for short TTIs rather than full scheduling procedures. This partial approach provides sufficient control for latency-critical operations while reducing processing overhead compared to complete scheduling mechanisms. The simplification covers only the essential functions needed for short TTI operation.
Solution Approach 2:
The patent extracts and removes non-essential scheduling components from short TTI processing, keeping only the critical elements needed for rapid response. By taking out unnecessary control information fields and simplifying procedures, the system achieves fast response times while minimizing processing overhead and energy consumption.
Data Source
AI summary
A user terminal communicates by using a plurality of cells, including at least a given cell to use a first TTI and a second TTI having a shorter TTI length than the first TTI, and this user terminal has a receiving section that receives, in the given cell, first downlink control information that is transmitted by using the first TTI and/or second downlink control information that is transmitted by using the second TTI, and a control section that controls receipt of a downlink shared channel that is transmitted in another cell and/or transmission of an uplink shared channel, based on the first downlink control information and/or the second downlink control information.