MSC Server Ring-Back Tone Triggering for CS Fallback Latency
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Solution Overview
Problem
In the context of CS domain fallback, mobile terminated calls result in prolonged waiting times for the calling party to be informed about the network's connection with the called user, leading to a poor user experience, especially when the called user is in idle mode on the E-UTRAN side.
Innovation Solution
A Mobile Switching Centre (MSC) server is configured to send a Paging Request and initiate a ring-back tone towards the calling party as soon as a successful paging procedure is confirmed, using the SGs service request message to trigger state transitions and indicate call progression, regardless of the called user's mode (Connected or Idle).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the network waits for the ALERTING message from the called UE before initiating the ring-back tone, then the call establishment protocol is followed correctly, but the calling user experiences a very long waiting time
Solution Approach 1:
The network performs preliminary action by initiating the ring-back tone before receiving the ALERTING message from the called UE. The MSC server sends the ring-back tone to the calling UE as soon as it determines the called UE is being alerted, based on paging response or service request messages, rather than waiting for the actual ALERTING message. This preliminary action reduces the waiting time for the calling user while maintaining protocol compliance.
2Reliability
If the called UE sends an ALERTING message after falling back to UTRAN/GERAN, then the call establishment protocol is maintained, but the calling user hears the ring-back tone after the called user has already been alerted
Solution Approach 1:
The network uses feedback from paging response messages or service request messages sent by the called UE to UTRAN/GERAN to determine when the called user is being alerted. Based on this feedback, the MSC server proactively initiates the ring-back tone to the calling user, ensuring the tone is played at the appropriate moment rather than waiting for the ALERTING message, thus improving user experience while maintaining protocol compliance.
3Productivity
If the called UE sends CALL CONFIRMED and CONNECT messages without an ALERTING message, then the call establishment is faster, but the calling user does not hear a ring-back tone before hearing the called user
Solution Approach 1:
The network performs preliminary action by proactively sending the ring-back tone to the calling user before the called UE sends CALL CONFIRMED and CONNECT messages. The MSC server initiates the ring-back tone based on feedback from paging responses or service requests, ensuring the calling user hears the tone first, which improves user experience while maintaining fast call establishment speed.
Data Source
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AI summary
Disclosed are devices and methods for provisioning of voice and other CS-domain services. A first server (22) comprises a call reception block (221) configured to receive an incoming voice call, from a first user equipment; a transmitting block (222) configured to send, in response to the reception of the incoming voice call, a paging request to a second server; a service request reception block (223) configured to receive, from the second server, an SGs service request message, and; a trigger block (224) configured to use the SGs service request message as a trigger to send an indication of user alerting to the first user equipment when the SGs service request message indicates that a second user equipment was in Connected mode.