IMS Call Setup Time Reduction via Wake-Up Message Bypass
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Solution Overview
Problem
The existing VoLTE call setup procedures in mobile networks involve sequential IMS and radio resource control procedures, leading to increased Call Setup Time (CST) due to cumulative processing times through multiple application servers, especially when the UE is in an idle state and no data is being transmitted.
Innovation Solution
A wake-up message, such as an SIP OPTIONS request, is created by a network element to bypass multiple application servers, initiating the transition of the terminating UE from an idle to a connected state in parallel with the SIP call initiation message, thereby reducing CST by starting the radio channel reestablishment and IMS procedures earlier.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the SIP call initiation message is transmitted sequentially through multiple application servers to establish the call, then the call setup follows the standard IMS procedure with proper resource reservation, but the Call Setup Time increases due to cumulative processing delays through each server
Solution Approach 1:
The patent applies preliminary action by sending a wake-up message before the main SIP INVITE message to trigger the UE to transition from idle to connected state in advance. This preliminary transition preparation allows the main call setup procedures to proceed faster once the INVITE arrives, effectively reducing the cumulative processing delay through multiple servers while maintaining reliable call establishment.
2Loss of energy
If the UE remains in idle state to conserve network resources, then network resource usage is optimized, but the transition to connected state takes additional time when a call is initiated
Solution Approach 1:
The wake-up message triggers preliminary actions in the UE to prepare for upcoming call setup by initiating the transition from idle to connected state before the main SIP INVITE arrives. This allows the UE to be ready faster when the actual call is needed, reducing the perceived call setup time while maintaining the energy-saving idle state during non-call periods.
3Device complexity
If the media plane bearer establishment is assumed to be quick and user plane resources always available, then the QoS Precondition feature can be omitted simplifying the setup, but this assumption may not hold in mobile networks with complex resource reservation procedures
Solution Approach 1:
The patent extracts the QoS Precondition complexity from the main call setup flow by handling resource reservation separately through the wake-up message mechanism. This allows the main SIP INVITE path to remain simple and fast, while resource availability is ensured through the preliminary wake-up and transition preparation, effectively separating the timing-critical signaling from the resource-management functions.
Data Source
AI summary
A method for decreasing a Call Setup Time Key Performance Indicator (CST KPI) of an Internet Protocol (IP) multimedia call in a mobile telecommunications network includes: initiating the IP multimedia call from an originating user equipment (UE) to a terminating UE; transmitting a session initiation protocol (SIP) call initiation message from the originating UE to a terminating Proxy-Call Session Control Function (P-CSCF) through an originating Serving-Call Session Control Function (S-CSCF); and creating a wake-up message via a network element upon receiving the SIP call initiation message. The wake-up message bypasses a plurality of network application servers (ASs) to start switching a transition of the terminating UE from an idle state to a connected state before the SIP call initiation message reaches the terminating P-CSCF.