UE PLMN Search Order Optimization via Frequency Group Prioritization
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Solution Overview
Problem
Current mobile communication systems, particularly 3GPP-compliant systems, face inefficiencies in cell/PLMN selection processes during power-up and loss-of-service scenarios, as they search all frequency bands of a RAT before switching to another, potentially wasting time searching invalid bands.
Innovation Solution
A method where a UE searches for cells in the most recently used frequency group of a first RAT and, if unsuccessful, switches to a second RAT to search in its most recently used frequency group, optimizing the search order to avoid unnecessary searches in invalid bands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the UE searches all frequency bands of a RAT before switching to another RAT, then the search is exhaustive and reliable, but the search time increases significantly
Solution Approach 1:
The UE performs preliminary actions by storing the most recently used frequency group information from previous successful PLMN selections. When a new search is needed, the UE prioritizes searching these previously successful frequency groups first, rather than starting from scratch or searching all bands systematically. This preliminary preparation of frequency group information resolves the contradiction by enabling faster searches while maintaining reliability through targeted rather than exhaustive searching.
2Reliability
If the UE searches all frequency bands to ensure complete coverage, then no valid cell is missed, but power consumption increases
Solution Approach 1:
The UE applies local quality by concentrating search efforts on specific frequency groups that have demonstrated success in previous selections, rather than uniformly searching all frequency bands. The search resource allocation is made non-uniform, with higher priority given to the most recently used frequency groups. This resolves the contradiction by achieving reliable cell selection through focused local searching rather than exhaustive global searching, thereby reducing power consumption.
3Ease of operation
If the UE searches frequency bands in a systematic linear order, then the search process is simple and deterministic, but the search efficiency decreases when valid cells are in non-sequential bands
Solution Approach 1:
The UE implements dynamic search ordering by adapting the search sequence based on historical selection data. Instead of a fixed linear order, the search priority dynamically adjusts to place most recently used frequency groups at the front of the search queue. This dynamic reordering resolves the contradiction by maintaining operational simplicity through automated adaptation while significantly improving service acquisition speed when valid cells are located in frequency groups that were recently successful.
Data Source
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AI summary
By employing an intelligent search order, a user equipment in a mobile communication system can shorten the time needed to find a cell/public land mobile network. After a first cell has been found, the equipment can determine which frequencies it will be worthwhile to search when another search is needed for a second cell. The equipment can thus avoid wasting time searching for cells in frequencies of a radio access technology that may not be valid when cells can be found in a most recently used group of frequencies of another radio access technology.