Terminal Equipment Cell Reselection on Unlicensed Frequencies
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Solution Overview
Problem
In New Radio (NR) systems, especially in NR-U mechanisms, the inability to transmit Master Information Blocks (MIB) and System Information Blocks (SIB) due to busy channels leads to frequent cell reselection attempts, causing increased power consumption and prolonged camping on serving cells, as all cells on a busy frequency are barred for 300 seconds, preventing terminal equipment from acquiring essential system information.
Innovation Solution
Implementing a method where terminal equipment considers all cells on an unlicensed frequency as barred or of lowest priority within a predefined time when essential system information cannot be acquired, allowing it to save power and quickly find a suitable cell by limiting repeated attempts on busy frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If terminal equipment continuously attempts to acquire MIB and SIB1 on unlicensed frequency, then it may eventually obtain system information, but power consumption increases and camping time is prolonged
Solution Approach 1:
The terminal equipment performs preliminary channel monitoring and LBT/CCA checks before attempting to acquire MIB and SIB1. By detecting channel busy status in advance, the terminal avoids unnecessary acquisition attempts and reduces power consumption while maintaining reliable system information acquisition when the channel is actually available.
2Reliability
If terminal equipment continuously attempts to acquire MIB and SIB1 on unlicensed frequency, then it may eventually obtain system information, but the time to find a suitable cell is prolonged
Solution Approach 1:
The terminal equipment performs preliminary channel monitoring and LBT/CCA checks before attempting to acquire MIB and SIB1. By detecting channel busy status in advance, the terminal avoids unnecessary acquisition attempts and reduces time to find a suitable cell while maintaining reliable system information acquisition when the channel is actually available.
3Reliability
If all cells on the same frequency are barred when one cell cannot provide MIB/SIB1, then system information acquisition reliability is maintained, but the terminal cannot utilize other cells on the same frequency
Solution Approach 1:
Instead of barring all cells on the frequency as a single group, the terminal equipment evaluates each cell individually by performing LBT/CCA checks and attempting MIB/SIB1 acquisition on each cell separately. This segmentation allows the terminal to select suitable cells while avoiding cells with busy channels, maintaining system information acquisition reliability while improving cell reselection flexibility.
Data Source
AI summary
A method and apparatus for processing when acquisition of essential system information fails. The method is applicable to a terminal equipment side and includes: in a process of evaluation of cell reselection by a terminal equipment, or in a case where a terminal equipment applies system information acquisition procedure, when the terminal equipment is unable to acquire the essential system information on least one cell on an unlicensed frequency, considering by the terminal equipment that all cells on the frequency are barred within a predefined first time, or, considering by the terminal equipment that the frequency is the lowest priority within a predefined first time.