UE RAT Switching for 5G-to-4G Service Preservation
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Solution Overview
Problem
In wireless communications systems, UEs may incorrectly fallback to lower service level radio access technologies (RATs like 2G or 3G when a 4G request is rejected due to unexpected causes, even if the network supports 4G, leading to loss of additional services offered by 4G.
Innovation Solution
The UE is configured to identify preconfigured rejection causes and fallback to 4G without 5G support instead of lower RATs, maximizing service availability by maintaining or establishing a 4G connection based on network support indicators.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the UE falls back to lower service level RATs (2G or 3G) when a 4G request is rejected, then the connection is maintained, but additional services offered by 4G are lost
Solution Approach 1:
The patent implements dynamic RAT selection based on rejection cause analysis. The UE monitors rejection causes from the network and dynamically adjusts its RAT preference: when rejection cause indicates 5G parameter issues, the UE maintains 4G connectivity; when rejection cause indicates 4G incompatibility, the UE falls back to 2G/3G. This dynamic adaptation resolves the contradiction by optimizing both connection reliability and service availability based on real-time network conditions.
Solution Approach 2:
The patent changes the parameter of RAT selection criteria by introducing rejection cause analysis. Instead of uniformly falling back to lower RATs upon any rejection, the system evaluates the specific rejection cause (e.g., 5G parameter rejection vs. 4G incompatibility) and adjusts the selection parameters accordingly. This allows the UE to maintain 4G connectivity when possible while still ensuring connection reliability through appropriate fallback when necessary.
2Adaptability or versatility
If the UE continues to use 5G parameters after rejection, then service level is maintained, but network compatibility issues persist
Solution Approach 1:
The patent implements a feedback mechanism where the UE analyzes rejection causes from the network and uses this information to adjust its RAT selection strategy. When the network rejects 5G parameters, the UE receives feedback indicating incompatibility and subsequently modifies its behavior to use 4G parameters instead. This feedback loop ensures network compatibility while maintaining the highest possible service level, resolving the contradiction between service level and compatibility.
3Reliability
If the UE falls back to 2G or 3G RATs, then connection is maintained, but additional services offered by 4G are lost
Solution Approach 1:
The patent implements dynamic RAT selection that adapts to network conditions through rejection cause analysis. The system dynamically determines the appropriate fallback target: when 5G parameters are rejected, the UE maintains 4G connectivity to preserve service capabilities; when 4G itself is incompatible, the UE falls back to 2G/3G to ensure connection establishment. This dynamic approach resolves the contradiction by optimizing both connection reliability and service capability based on real-time network feedback.
Data Source
AI summary
Methods, systems, and devices for wireless communications are described. Generally, the described techniques provide for efficiently falling back from one RAT to another RAT while maximizing the services available to a UE. When a request from a UE for communicating with a base station using one RAT is rejected by a network node for unexpected causes, the UE may use the techniques described herein to fallback to an appropriate RAT. For instance, after receiving a response indicating that a request including fifth generation (5G) parameters is rejected, the UE may drop the 5G parameters and fall back to fourth generation (4G), rather than falling back to second generation (2G) or third generation (3G). The unexpected causes may be preconfigured and may be determined based on a number of factors, including a subscription of the UE, a public land mobile network (PLMN) associated with the network node, etc.