Multi-mode UE RAT Reselection via Network Assistance Data
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Solution Overview
Problem
Current wireless technologies lack efficient mechanisms for reselection from older radio access technologies (RATs) like 2G or 3G to newer technologies such as 5G New Radio (NR), leading to time-consuming and costly reselection processes, especially when switching back to NR RAT.
Innovation Solution
A multi-mode user equipment (UE) is equipped with mechanisms to store information about previously used RATs, allowing it to quickly switch back by determining the availability of cells in the original RAT without blind searching, using timers and access point-assisted data to efficiently reselect the original RAT.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a multi-mode UE uses blind searching to reselect to the original RAT, then the UE can find available cells, but the reselection process becomes time-consuming and power-consuming
Solution Approach 1:
The network provides assistance data in advance that contains information about suitable cells and frequencies for the original RAT. This preliminary information allows the UE to skip blind searching and directly evaluate whether those pre-identified cells are available, dramatically reducing reselection time and power consumption while maintaining reliable cell availability determination
2Reliability
If a multi-mode UE performs comprehensive cell search to ensure reliable reselection, then the UE can find available cells, but the power consumption increases
Solution Approach 1:
The network performs comprehensive cell information gathering and provides assistance data containing pre-evaluated cell suitability information. This shifts the computational and energy burden from the UE to the network, allowing the UE to perform lightweight checks on pre-identified cells rather than conducting exhaustive searches, thereby reducing UE power consumption while maintaining reselection accuracy
3Loss of time
If a multi-mode UE stores detailed information about the original RAT, then the reselection process becomes faster, but the device complexity increases
Solution Approach 1:
The network acts as an intermediary that stores and manages comprehensive cell information in assistance data. The UE only needs to store and process lightweight references to this assistance data rather than maintaining detailed cell information locally. This mediator approach enables fast reselection by allowing the UE to quickly retrieve and evaluate pre-processed network-provided information without burdening the UE with complex storage and processing requirements
Data Source
AI summary
Some aspects of this disclosure relate to apparatuses and methods for the reselection of a Radio Access Technology (RAT) for a multi-mode user equipment (UE). A UE can determine that the UE camps on a first RAT for service by a first public land mobile network (PLMN) and that the UE camps on a second RAT for service by a second PLMN, and store information about the first RAT for the first PLMN. The UE can further determine whether there is a trigger event to enable the UE to switch from the second RAT to the first RAT. In response to a determination that there is the trigger event, the UE can determine whether a cell in the first RAT for the first PLMN is available for the UE to camp on to select the available cell in the first RAT to register the UE with the first PLMN.