NTN Cell Reselection Frequency Priority Adjustment
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Solution Overview
Problem
In Non-Terrestrial Networks (NTN), the service stop time of a quasi-earth fixed cell poses challenges for user equipment (UE) to perform timely cell reselection due to the decrease in cell quality when the beam steers to the next serving area, and the UE's reluctance to reselect to neighbor cells of equal or lower frequency priority when the serving cell quality is good.
Innovation Solution
A method where a wireless device receives a cell reselection configuration from the network, which includes a frequency list, first and second priority values for each frequency, and location conditions. The device applies the first priority values initially and determines if the location condition for a specific frequency is met, then applies the second priority value if the condition is satisfied, to prioritize neighbor cell frequencies for cell reselection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the UE performs neighbor cell measurements until the service stop time, then the measurement coverage is improved, but the cell reselection timing is delayed because the UE does not reselect to neighbor cells of equal or lower frequency priority when serving cell quality is good
Solution Approach 1:
The patent dynamically adjusts frequency priority values based on location conditions. The network configures multiple frequency priority values for different location conditions, and the UE applies different priorities depending on whether the location condition is met. This dynamic adjustment enables the UE to prioritize neighbor cell reselection when approaching the service stop time or specific locations, resolving the contradiction between thorough measurement and timely reselection.
Solution Approach 2:
The patent changes the frequency priority parameter based on location conditions. Instead of using a static priority value, the system configures first and second priority values that differ based on whether the UE satisfies the location condition. This parameter change mechanism allows the UE to switch from conservative reselection behavior to aggressive reselection behavior when needed, ensuring timely cell reselection before service stop time.
2Reliability
If the UE reselects to neighbor cell earlier, then the service continuity is improved, but the serving cell quality may be degraded prematurely
Solution Approach 1:
The patent applies different frequency priority values for different location conditions. When the location condition is not met (UE is still in optimal serving cell area), the UE uses the first priority value to maintain normal serving cell connectivity. When the location condition is met (UE is approaching service stop time or boundary), the UE switches to the second priority value to prioritize neighbor cell reselection. This localized quality adjustment ensures service continuity without premature degradation of serving cell quality.
Solution Approach 2:
The network configures location conditions in advance that predict when the UE will need to reselect. The UE evaluates these pre-configured conditions and proactively adjusts frequency priorities before the actual service stop time occurs. This preliminary action allows the UE to prepare for reselection in advance, ensuring seamless service continuity while maintaining optimal serving cell quality until the appropriate moment for handover.
Data Source
AI summary
A method and apparatus for frequency priority for cell reselection in a wireless communication system is provided. A wireless device may receive, from a network, a cell reselection configuration associated with a Non-Terrestrial Networks (NTN) cell. The wireless device may apply the first priority values for the multiple frequencies. The wireless device may determine that the location condition for a specific cell in a specific frequency, among the multiple frequencies, is met. The wireless device may apply a second priority value for the specific frequency.