Uplink Signal Synchronization in Unlicensed Band LTE Terminals
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In the context of LTE mobile communication systems using unlicensed bands, existing technologies face challenges in efficiently managing uplink data transmission across subframe boundaries and coordinating transmission start times among user terminals to avoid interference and ensure resource allocation, particularly due to the variability in Clear Channel Assessment (CCA) results and Extended CCA processing.
Innovation Solution
The proposed solution involves user terminals transmitting a specific signal at the beginning of uplink data transmission, if started from the middle of a subframe, and coordinating with each other to synchronize transmission start times, while base stations consecutively allocate frequency resources and manage allocation periods to minimize interference and ensure efficient resource use.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If uplink data transmission is started from the middle of a subframe based on CCA monitoring results, then transmission efficiency is improved by avoiding idle waiting, but the base station cannot accurately identify the transmission start time
Solution Approach 1:
A specific signal is introduced as an intermediary between the actual data transmission and the base station's detection system. This signal is transmitted at the beginning of uplink data when started from the middle of a subframe, serving as a detectable marker that enables the base station to accurately identify transmission start times without requiring the data itself to be detectable at those precise moments.
2Productivity
If user terminals transmit simultaneously based on independent CCA monitoring, then resource utilization is improved, but interference between terminals occurs
Solution Approach 1:
User terminals provide feedback to each other through specific signals indicating their transmission start times and frequency resource usage. This feedback mechanism allows terminals to coordinate their transmissions, enabling simultaneous resource utilization while preventing interference by allowing other terminals to adjust their transmission parameters based on the received information.
3Adaptability or versatility
If frequency resources are reallocated frequently to adapt to variable transmission timings, then transmission flexibility is improved, but signaling overhead increases
Solution Approach 1:
Frequency resources are allocated in advance for multiple possible transmission timings rather than reallocating for each specific timing. This preliminary allocation covers a range of potential start times, allowing the system to adapt to variable transmission timings without generating frequent reassignment signals, thus reducing signaling overhead while maintaining flexibility.
Data Source
AI summary
A user terminal according to an embodiment transmits uplink data to a base station using an unlicensed band. The user terminal includes a controller configured to, if uplink data transmission is started from a middle of a subframe according to a monitoring result of the unlicensed band, perform processing of transmitting a specific signal being different from the uplink data, at a beginning of the uplink data.