IMS Call Retry Logic for Multiple Radio Access Technologies
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Solution Overview
Problem
As PS-domain coverage increases and CS-domain RANs are decommissioned, existing telecommunications networks face challenges in determining the optimal retry method for connecting calls, often resulting in failed CS-domain retries due to outdated assumptions about UE coverage, leading to reduced success rates in call setups.
Innovation Solution
The system determines whether to perform a PS-domain or CS-domain retry based on the registered RAT type of the UE, age values of location information associated with CS-domain registration, and other factors, allowing the network to dynamically choose the most likely successful retry option.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the network performs CS-domain retry based on outdated assumptions, then the retry mechanism maintains simplicity, but the call setup success rate deteriorates due to decommissioned CS-domain RANs
Solution Approach 1:
The patent changes the parameter of retry domain selection from static (always CS-domain) to dynamic (PS-domain or CS-domain based on current conditions). The network determines the RAT type of the RAN the UE is connected to and selects the retry domain accordingly, transforming the retry mechanism from a fixed approach to an adaptive one that responds to changing network infrastructure conditions.
Solution Approach 2:
The retry logic transitions from a static configuration to a dynamic decision-making process. The network continuously monitors UE connection status and RAN availability, then adapts the retry domain selection in real-time. This dynamic approach allows the system to respond to decommissioned CS-domain RANs and redirected UEs to PS-domain RANs, maintaining high call setup success rates despite infrastructure changes.
2Reliability
If the network always attempts CS-domain retry, then the retry process remains simple and consistent, but it fails when CS-domain RANs are decommissioned and UEs are redirected to PS-domain
Solution Approach 1:
The patent implements a feedback mechanism where the network monitors UE connection status, RAN availability, and call setup outcomes. Based on this feedback, the system adjusts the retry domain selection. When the network detects that a UE is connected to a PS-domain RAN or that CS-domain RANs are unavailable, it adjusts the retry strategy accordingly, creating a closed-loop control system that continuously optimizes retry success rates.
Solution Approach 2:
The network performs preliminary assessment of UE connection status and RAN availability before initiating the retry process. By determining the RAT type of the currently connected RAN in advance, the network can proactively select the appropriate retry domain, preventing failed retry attempts and improving overall call setup success rates.
Data Source
AI summary
An Internet Protocol Multimedia Subsystem (IMS) application server can initially attempt to route a terminating call invite to a user equipment (UE) via a packet-switched (PS) domain radio access network (RAN). However, if that initial attempt fails, the application server can follow either a PS retry option to reattempt routing the terminating call invite via a PS-domain RAN, or a circuit-switched (CS) retry option to instead reattempt routing the terminating call invite via a CS-domain RAN. In some examples, if Home Subscriber Server (HSS) data indicates that the UE is connected to a Long-Term Evolution (LTE) RAN and that CS-domain location information for the UE is older than a threshold, the application server can enable the PS retry option. However, if the UE is connected to an LTE RAN but the CS-domain location information is more recent than the threshold, the application server can instead enable the CS retry option.