RAT Switching Fallback Using Rejection Causes to Preserve 4G Service
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Solution Overview
Problem
In wireless communications systems, UEs may incorrectly fallback to lower service generations (2G or 3G) when a 4G request is rejected due to unexpected causes, despite the network supporting 4G, leading to loss of additional services offered by 4G.
Innovation Solution
UEs are configured to identify preconfigured rejection causes and fallback to 4G without 5G support instead of 2G or 3G when a 4G request with 5G parameters is rejected, maximizing service availability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a UE fallback mechanism is implemented when a 4G request is rejected, then connectivity is maintained, but the UE may incorrectly fallback to lower service generations (2G or 3G) despite the network supporting 4G, leading to loss of additional services offered by 4G
Solution Approach 1:
The patent implements a feedback mechanism where the UE monitors rejection causes from the network and uses this information to intelligently determine the appropriate fallback behavior. When a 4G request is rejected, the UE checks the rejection cause and only falls back to lower generations if explicitly indicated by the network, otherwise it maintains 4G connectivity. This feedback-driven approach resolves the contradiction by making the fallback decision based on actual network conditions rather than defaulting to lower generations.
Solution Approach 2:
The patent makes the fallback mechanism dynamic by allowing the UE to adapt its behavior based on network responses and rejection causes. Instead of a static fallback to 2G/3G, the system dynamically adjusts the fallback target based on whether the network explicitly indicates unsupported radio access technology. This dynamic adaptation preserves service availability while maintaining reliability through condition-based decision making.
2Adaptability or versatility
If the UE attempts to use 5G parameters in a 4G request, then higher service generation capabilities are utilized, but the request may be rejected by the network for unexpected causes, causing the UE to incorrectly fallback to lower generations
Solution Approach 1:
The patent applies preliminary action by having the UE check network support for higher service generations before attempting to use them in 4G requests. The UE monitors network indications and rejection causes in advance, and only includes 5G parameters when the network has explicitly indicated support. This preliminary verification prevents premature rejection and maintains connection stability while still enabling higher service generation capabilities when appropriate.
3Reliability
If the UE falls back to lower service generations (2G or 3G) when a 4G request is rejected, then connectivity is maintained, but additional services offered by 4G are lost
Solution Approach 1:
The patent uses feedback from network rejection causes to determine whether fallback is actually necessary. When a 4G request is rejected, the UE checks the rejection cause code and only falls back to lower generations if the code explicitly indicates unsupported radio access technology. For other rejection causes, the UE maintains 4G connectivity, thereby preserving both connectivity reliability and service quality simultaneously through intelligent, condition-based decision making.
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.