Delayed EPS Fallback for SIP Message Delivery in 5G RAN
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Solution Overview
Problem
The existing radio access network (RAN) fallback mechanisms, particularly EPS fallback, can introduce race conditions and delays in call setup due to ill-timed fallbacks, negatively impacting user experience by causing SIP message loss or undeliverability during voice or video calls in 5G networks.
Innovation Solution
Implementing a delayed EPS fallback process where the 5G RAN waits for a predetermined timer to expire or until the UE and IMS are in a safe phase before instructing the UE to fallback to the LTE RAN, ensuring that SIP messages are less likely to be lost or delayed during call setup.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If immediate EPS fallback is implemented when 5G RAN cannot handle a communication session, then fallback capability is provided, but SIP messages may be lost or delayed causing call setup delays
Solution Approach 1:
The system performs preliminary actions by delaying the EPS fallback until a safe phase is detected. The 5G RAN monitors SIP message timing and waits for appropriate intervals (e.g., 200ms, 500ms, 1s) before triggering fallback, ensuring critical SIP messages have been transmitted or received before the radio domain switch occurs.
Solution Approach 2:
The system uses feedback mechanisms by monitoring SIP message timing and radio resource status to determine when fallback should occur. The 5G RAN receives feedback about SIP message transmission status and adjusts the fallback timing accordingly, creating a closed-loop control system that optimizes the balance between reliability and timing.
2Productivity
If 5G RAN handles all communication sessions, then 5G network utilization is maximized, but compatibility issues arise for voice/video calls that 5G cannot handle
Solution Approach 1:
The system implements multi-functionality by enabling the 5G RAN to handle both 5G-capable communication sessions directly and to trigger fallback for sessions requiring circuit-switched domain support. The 5G RAN acts as a universal access point that can serve both modern 5G services and legacy voice/video call requirements through intelligent routing and fallback mechanisms.
3Reliability
If EPS fallback is delayed until safe phase, then SIP message delivery is improved, but fallback latency increases
Solution Approach 1:
The system applies dynamics by making the fallback timing flexible rather than fixed. The delay duration is dynamically adjusted based on the detected safe phase, using predetermined intervals (200ms, 500ms, 1s) that adapt to the actual SIP message timing and radio conditions, optimizing the balance between reliability and latency for each specific scenario.
Data Source
AI summary
A fifth generation (5G) radio access network (RAN) can determine that a user equipment (UE) should fall back to engaging in a communication session over an LTE-based Evolved Packet System (EPS) instead of a 5G system. However, to avoid interrupting setup operations that may be occurring separately for that communication session in an IP Multimedia Subsystem (IMS) apart from the 5G system, the EPS fallback can be delayed such that setup in the IMS can proceed at least to a point at which IMS signaling messages are less likely to be undeliverable due to the EPS fallback.