UE Cell Selection Using Stored RAT Priorities After Service Loss
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Solution Overview
Problem
User equipment (UE) experiences prolonged out-of-service time due to inefficient cell selection procedures after losing service, particularly when scanning through a large number of frequencies across various radio access technologies (RATs) without prioritization.
Innovation Solution
Implementing an intermediate stored information cell selection (ISICS) procedure that prioritizes scanning frequencies based on previously used and preferred radio access technologies (RATs), with a configurable timer to pause and resume the initial cell search (ICS) when a suitable cell is not found within a specified time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the UE performs a search on all carrier frequencies corresponding to each RAT it supports, then the UE can find a suitable cell, but the out-of-service time is prolonged
Solution Approach 1:
The cell selection procedure is segmented into multiple phases: SICS (Stored Information Cell Selection) phase that searches only stored frequencies first, followed by ICS (Initial Cell Selection) phase that searches all frequencies if SICS fails. This segmentation allows the UE to quickly attempt recovery on known good frequencies before undertaking the more time-consuming comprehensive search.
Solution Approach 2:
The UE performs preliminary actions by maintaining and using a stored list of frequencies from previously camped cells before initiating a full search. The SICS procedure uses this pre-stored information to attempt cell selection without needing to scan all possible frequencies, thereby reducing the time to regain service while maintaining reliability.
2Adaptability or versatility
If the UE performs a comprehensive search on all frequencies, then all possible RATs are covered, but the service re-establishment time increases
Solution Approach 1:
The cell selection procedure dynamically adapts based on the UE's service status. When in-service, the UE maintains a stored frequency list optimized for its current RAT. When out-of-service, the UE first attempts SICS using stored information, and only if that fails does it proceed to the more comprehensive ICS procedure, creating a dynamic two-stage approach that balances speed and completeness.
Solution Approach 2:
The search strategy applies different quality levels of frequency lists to different situations: a focused, high-quality stored frequency list (SICS) is used first for quick recovery, and only if needed does the UE expand to a comprehensive frequency list (ICS) that covers all RATs. This local quality approach ensures the most efficient search path is taken first.
Data Source
AI summary
Techniques are provided for implementing a cell selection procedure to get a user equipment (UE) into service on prioritized RAT after an out-of-service detection. For example, some aspects of this disclosure relate to a method including determining, by a user equipment (UE), whether the UE has a loss of service, and in response to determining that the UE has the loss of service, initiating an initial cell selection (ICS) and starting a timer. The method further includes determining whether a suitable cell is identified during the ICS and determining whether the timer has expired. The method further includes, in response to determining that a suitable cell is not identified during the ICS and the timer has expired, pausing the ICS, and performing an intermediate stored information cell selection (ISICS) to identify a suitable cell.