Mobile Device Offline Inter-RAT Return Using Cached Cell Data
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Solution Overview
Problem
In wireless communication systems, particularly in LTE, UE devices face challenges during inter-RAT procedures such as handover, cell redirection, or cell reselection, as they often require significant signaling and network upgrades to move between radio access technologies, leading to increased costs and delays in returning to the original LTE system.
Innovation Solution
A method where the UE collects cell information when camping on a second RAT and performs an offline inter-RAT procedure to move back to the first RAT using cached data, reducing the need for network-provided information and signaling, thereby enabling quicker transitions without network upgrades.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the UE performs PLMN search to return to the first RAT, then the UE can search for a PLMN and cell, but the UE has to stop all on-going procedures and takes a lot of time to return
Solution Approach 1:
The UE stores cell information of the first RAT in memory before falling back to the second RAT. This preliminary storage of cell information enables the UE to quickly return to the first RAT without performing a complete PLMN search, thus reducing the time loss while maintaining the reliability of returning to the original system.
2Ease of operation
If the legacy system provides LTE cell information through system information broadcasting, then the UE can perform measurement and reselect to LTE cell, but the legacy system cells have to be upgraded which increases cost
Solution Approach 1:
The UE autonomously stores cell information of the first RAT when it camps on the second RAT. This self-service approach eliminates the need for the legacy system to provide LTE cell information through system information broadcasting, thereby avoiding network upgrades and reducing costs while maintaining the UE's ability to easily return to LTE.
3Ease of operation
If the network provides redirection information to indicate UE to return to first RAT, then the UE can return to first RAT, but the network has to be upgraded which increases cost
Solution Approach 1:
The UE autonomously stores cell information of the first RAT in memory, enabling it to independently return to the first RAT without requiring the network to provide redirection information. This self-service mechanism eliminates the need for network upgrades while maintaining ease of operation for the UE.
4Adaptability or versatility
If the UE performs inter-RAT procedure to move to another RAT, then the UE can handover or redirect to new RAT, but the signaling number increases
Solution Approach 1:
The UE pre-stores cell information of the first RAT before falling back to the second RAT. This preliminary action reduces the need for extensive signaling during the inter-RAT procedure, as the UE already has the necessary cell information cached and can quickly return to the first RAT with minimal network communication.
Data Source
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AI summary
A method for radio access technology, hereafter called RAT, change for a mobile device is disclosed. The method comprises whenever camping on a RAT, collecting cell information for at least one cell, falling back to a first RAT, and performing an offline procedure for moving to the camped RAT from the first RAT according to the collected cell information.