SIP Session Handover via Session Border Controller
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Solution Overview
Problem
Current technologies do not fully support seamless handovers of voice or multimedia sessions between different access technologies and operator networks, particularly failing to recognize session border elements and hide network topologies, leading to potential interruptions during user movement.
Innovation Solution
A method involving a terminal detecting a second access network, registering with a call server, sending a SIP invite message with a changed Session Description Protocol payload, and establishing a second connection through a node of the second access network, allowing for seamless handover across different access and operator networks using standard SIP signaling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If current IMS-based handover scenarios are used, then basic connectivity is maintained, but session border elements and network topologies are not properly hidden, leading to potential interruptions and incompatibility with future network infrastructure
Solution Approach 1:
A session border controller (SBC) is introduced as an intermediary element between the terminal and the communication partner. The SBC terminates SIP messages from the terminal, modifies the Session Description Protocol payload by changing the terminal's address to the SBC's own address, and forwards the modified message to the communication partner. This intermediary approach ensures proper topology hiding, session continuity during handovers, and compatibility with future network infrastructure without requiring new standardization efforts.
2Productivity
If direct SIP messaging between terminal and communication partner is used, then communication efficiency is improved, but network topology visibility increases, exposing terminal movement and access network changes
Solution Approach 1:
The session border controller acts as a mediator that receives SIP messages from the terminal, terminates them, and re-originates new SIP messages to the communication partner. By modifying the Session Description Protocol payload to contain the SBC's address instead of the terminal's address, the SBC prevents the communication partner from directly seeing the terminal's real address and network path changes. This maintains communication efficiency while protecting network topology information.
3Adaptability or versatility
If handover between different access networks is implemented, then user mobility is improved, but session interruption risk increases due to lack of support for session border elements
Solution Approach 1:
The session border controller is pre-positioned in the network path before handover occurs. When the terminal moves to a different access network, the SBC already has the capability to terminate and re-originate SIP messages with modified addresses. This preliminary setup ensures that session continuity is maintained during handover without requiring new standardization efforts, as the SBC handles the address translation and message forwarding transparently.
Data Source
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AI summary
The invention concerns a method, a terminal (40), a node (10) of a first access network (1), a node (20) of a second access network (2), a call server function (30), and a communication network (123) for performing a handover for a terminal (40) having a session-oriented first connection (100) with a communication partner (50) via the first access network (1). The terminal (40) detects the availability of the second access network (2), and registers via the second access network (2) at a call server function (30). The terminal (40) sends an invite message directed to the communication partner (50) via the second access network (2). The node (20) of the second access network (2) terminates the invite message, changes a Session Description Protocol payload of the invite message to an address of said node (20) of the second access network (2), and sends an invite message with the changed Session Description Protocol payload from said node (20) of the second access network (2) to the call server function (30). The invite message with the changed Session Description Protocol payload received by the call server function (30) is routed to a node (10) of the first access network (1), and a second connection (200, 2010) between the node (10) of the first access network (1) and the terminal (40) via the node (20) of the second access network (2) is opened.