SRVCC Indication via eNodeB-MME Signaling for EPS Handovers
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Solution Overview
Problem
Current mobile communication networks, particularly in Evolved Packet System (EPS) networks, face challenges in accurately indicating Voice-over-IMS and SRVCC support, leading to voice call disruptions during handovers due to unsupported Radio Access Networks (RAN) nodes, as the Mobility Management Entity (MME) lacks information about target RNC capabilities.
Innovation Solution
The eNodeB provides SRVCC and Voice-over-IMS support information to the MME through dedicated messages, such as the UE Capability Info Indication or Initial Context Response, ensuring accurate network support indications for the UE, even during handovers, by signaling RAN-level support information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the MME relies on general UE capability indication for SRVCC support, then the indication process is simple, but voice call continuity cannot be guaranteed during handovers to RAN nodes that do not support SRVCC
Solution Approach 1:
The source eNodeB performs preliminary action by determining the SRVCC support capability of the target RNC before the handover is executed. This capability information is then included in the Handover Request message sent to the target RNC, and the MME is informed of the target RNC's SRVCC capability. This preliminary determination prevents voice call disruption by ensuring the target node can handle SRVCC before the handover occurs.
Solution Approach 2:
The system implements feedback by having the source eNodeB send target RNC capability information back to the MME through the Handover Request message or separate indication. The MME uses this feedback information to make informed decisions about SRVCC support during handover, ensuring that voice service continuity is maintained by only allowing handovers to SRVCC-capable nodes.
2Reliability
If the MME makes SRVCC decisions without target RNC capability information, then the decision process is fast, but voice service reliability deteriorates due to unsupported handovers
Solution Approach 1:
The capability information exchange is merged into the existing handover signaling流程. The source eNodeB includes target RNC SRVCC capability information in the Handover Request message that is already being sent as part of the normal handover procedure. This merging approach adds minimal complexity while ensuring voice service reliability, as the capability information is transmitted through an already-established signaling path.
3Reliability
If SRVCC capability indication is only provided at UE and MME level, then the signaling overhead is reduced, but handover failures occur when target RAN nodes do not support SRVCC
Solution Approach 1:
The solution applies local quality by determining SRVCC capability at the specific target RNC level rather than making a general network-wide assumption. The source eNodeB evaluates the SRVCC capability of each potential target RNC individually based on local configuration information, and only includes SRVCC-capable target nodes in handover candidates. This localized assessment ensures handover success while adding minimal signaling overhead.
Data Source
AI summary
Embodiments of the present invention include a method for enhanced indication of network support of SRVCC and/or Voice-over-IMS for an User Equipment UE in an Evolved Packet System EPS network, said method comprising at least one step based on taking into account support of SRVCC and/or Voice-over-IMS by Radio Access Network RAN nodes and/or by Radio Access Technologies RATs available for SRVCC for said UE in said EPS network.