Modem Control Layer for Seamless IMS Session Handover
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Solution Overview
Problem
Traditional mobile communication device architectures fail to handle handovers of multiple IMS sessions from packet-switched (PS) networks to circuit-switched (CS) networks effectively, as they are unaware of the number and type of sessions established by an external IMS host application, leading to dropped calls during handovers.
Innovation Solution
The introduction of a modem with a control layer that aligns IMS session data between the host IMS application and the modem, using AT commands to submit session data, allowing the modem's control layers to establish sufficient call control channels for successful handovers, employing SRVCC and vSRVCC procedures to maintain all IMS sessions across network transitions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the modem uses traditional architecture without control layer alignment, then the device structure remains simple, but the modem cannot identify multiple IMS sessions established by external host applications, leading to dropped calls during handovers
Solution Approach 1:
The control layer performs preliminary alignment of IMS session data between the host application and modem before handover is needed. This advance preparation ensures the modem has accurate session information ready when handover occurs, preventing call drops without requiring complex real-time detection mechanisms during the handover process itself.
Solution Approach 2:
The control layer acts as an intermediary between the host application and the physical layer, managing the alignment and transfer of IMS session data. This intermediary structure allows the modem to handle multiple sessions without requiring the host application to directly manage modem complexity, resolving the contradiction by introducing a controlled interface layer.
2Measurement precision
If the modem aligns IMS session data with the host application using control layer mechanisms, then handover accuracy improves, but the data alignment process and control layer mechanisms increase system complexity
Solution Approach 1:
The data alignment mechanism is segmented into distinct control layer functions: session data reception from the host application, session data storage and management, and session data transmission to the physical layer for handover. This segmentation allows each function to be optimized independently, improving measurement precision while managing complexity through modular design.
3Reliability
If the modem establishes separate call control channels for each IMS session, then handover reliability improves, but the number of control channels increases system complexity
Solution Approach 1:
The control layer implements a universal session management mechanism that can handle multiple IMS sessions through a standardized data alignment interface. Rather than creating entirely separate control systems for each session, the universal control layer manages all sessions using consistent procedures and data structures, improving handover reliability while minimizing the increase in system complexity through reuse of common functions.
Data Source
AI summary
A modem and a method for handing over Internet protocol (IP) multimedia subsystem (IMS) sessions from a packet-switched network to a circuit-switched network. One embodiment of the modem includes: (1) a physical layer through which IMS packets for a plurality of IMS sessions are transmittable and receivable, and (2) a control layer configured to gain access to respective IMS session data for the plurality of IMS sessions, the respective IMS session data originating from a host IMS application.