Cell Reselection Ranking Using PLMN Offset in Unlicensed Frequency
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Solution Overview
Problem
Current wireless communication systems face challenges in efficiently supporting standalone operation of 5G New Radio (NR) on unlicensed frequency bands, particularly in cell reselection processes, where existing methods do not adequately consider the Public Land Mobile Network (PLMN) offset, leading to suboptimal performance and potential interference.
Innovation Solution
A method and apparatus for wireless devices that measure the quality of serving and neighboring cells, receive PLMN offset information on unlicensed frequencies, and perform cell reselection based on the determined ranking, prioritizing cells belonging to registered or equivalent PLMNs to optimize network selection and minimize interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If cell reselection is performed without considering PLMN offset in unlicensed frequency, then cell reselection process is simple, but network performance and interference management deteriorate
Solution Approach 1:
The patent introduces a PLMN offset parameter specifically for unlicensed frequency bands that modifies the cell reselection ranking calculation. By changing the parameter set used in ranking (adding QoffsetPLMN for unlicensed frequencies), the system achieves better network performance without fundamentally changing the reselection mechanism's complexity
Solution Approach 2:
The patent applies different quality criteria for cell reselection based on the frequency type. For unlicensed frequencies, PLMN offset is considered in the ranking, while for licensed frequencies, traditional RSRP-based ranking is used. This local differentiation optimizes performance for unlicensed bands without affecting other frequency operations
2Reliability
If cell reselection prioritizes cells in registered PLMNs using PLMN offset, then interference is reduced and network performance improves, but cell reselection process complexity increases
Solution Approach 1:
The patent makes the cell reselection ranking dynamic by conditionally applying PLMN offset based on frequency type. The system dynamically adjusts the ranking formula: for unlicensed frequencies, it includes QoffsetPLMN to prioritize registered PLMN cells, while for licensed frequencies, it uses the traditional RSRP-based ranking without PLMN offset
Solution Approach 2:
The patent segments the cell reselection process by frequency type (licensed vs. unlicensed). For unlicensed frequencies, a separate ranking mechanism incorporating PLMN offset is applied, while licensed frequencies continue with the existing mechanism. This segmentation isolates the complexity to only where it is needed
3Measurement precision
If PLMN offset is applied for cell ranking in unlicensed frequency, then cell reselection accuracy improves, but measurement and calculation complexity increases
Solution Approach 1:
The patent performs preliminary action by obtaining the PLMN offset value from system information broadcasting before the actual cell reselection ranking is performed. This pre-fetching of the offset parameter simplifies the real-time ranking calculation, as the offset value is already available and does not need to be measured or calculated during the ranking process
Data Source
AI summary
A method and an apparatus for cell reselection by ranking cells using PLMN offset in unlicensed frequency in a wireless communication system is provided. The method, by a UE, may include measuring a quality of a serving cell and a neighboring cell, receiving a PLMN offset on unlicensed frequency from a network, determining ranking of the serving cell and the neighboring cell based on the PLMN offset and the measured quality, and performing a cell reselection based on the determined ranking.