RAT Interworking Policy Control for Reliable 5G/LTE Transitions
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Solution Overview
Problem
Current mobile core network architectures face issues with inconsistent network behaviors and interworking problems due to user equipment disabling N1/S1 operating modes, leading to failed Tracking Area Updates (TAUs) and inefficient management of Radio Access Technology (RAT) type changes.
Innovation Solution
A protocol-based approach where user equipment requests a RAT type change to the mobile core network, which determines subscription and authorization through a subscription management element, and sends an updated Access and Mobility Management policy to the UE, including a Frequency Selection Priority index, allowing seamless transitions between 5G/NR and 4G/LTE without disabling N1/S1 modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If user equipment disables N1/S1 operating modes to manage RAT type changes, then device control over network selection is improved, but network behavior consistency deteriorates and interworking problems occur
Solution Approach 1:
The patent introduces a mobility management entity (MME) as an intermediary that mediates between the UE's RAT selection requests and the core network. The MME receives TAU requests from UEs, determines appropriate RAT types based on network policies and subscription data, and manages the N1/S1 operating modes centrally, thereby maintaining network behavior consistency while still allowing UE-initiated RAT changes.
Solution Approach 2:
The system implements feedback mechanisms where the network provides policy information to UEs through TAU acceptance messages and other signaling. The network monitors UE behavior and adjusts RAT selection policies dynamically, creating a closed-loop control system that maintains consistency while adapting to changing conditions.
2Speed
If user equipment autonomously selects RAT types, then responsiveness to network conditions is improved, but Tracking Area Updates fail and interworking problems arise
Solution Approach 1:
The network performs preliminary actions by pre-configuring UEs with policy information, RAT selection criteria, and operating mode requirements before TAU attempts. The MME prepares acceptance criteria and network responses in advance, ensuring that UE autonomous selection occurs within pre-approved parameters that guarantee TAU success.
Solution Approach 2:
The MME acts as an intermediary that validates UE RAT selection decisions before accepting TAU requests. It checks whether the selected RAT type aligns with network policies and subscription data, and can reject or redirect TAU attempts to ensure proper interworking between different RAT types.
3Adaptability or versatility
If N1/S1 operating modes are disabled for RAT transitions, then device flexibility is improved, but network management complexity increases
Solution Approach 1:
The patent extracts the complexity of N1/S1 operating mode management from individual UEs and centralizes it in the mobility management entity. The MME maintains and manages the operating modes for all UEs, removing the burden of mode switching logic from devices while preserving RAT transition flexibility through network-controlled policies.
4Extent of automation
If mobility management is distributed to user equipment, then device autonomy is improved, but network behavior consistency deteriorates
Solution Approach 1:
The system implements feedback loops where UEs report their RAT selection decisions and network conditions to the MME, which responds with policy updates and acceptance/rejection decisions. This feedback mechanism ensures that distributed device autonomy operates within network-defined boundaries, maintaining behavior consistency across the network.
Data Source
AI summary
Provided herein are techniques to facilitate Radio Access Technology (RAT) interworking for user equipment in a mobile networking environment. In one example, a method may include obtaining, from a user equipment (UE) that is connected to first wireless wide area (WWA) RAT type, a request to connect to a second WWA RAT type in which the request includes a location indicator identifying a location of the UE and a parameter identifying the second WWA RAT type; querying a subscription management element to determine whether the UE is subscribed to connect to the second WWA RAT type at the location; and based, at least in part upon determining that the UE is subscribed to connect to the second WWA RAT type at the location, sending a policy to the UE including an indicator of the second WWA RAT type to cause the UE to connect to the second WWA RAT type.