SIP Call Handover Across Wi-Fi and Cellular Without Re-Registration Delay
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Solution Overview
Problem
Existing methods for handover of calls between communication networks, such as from Wi-Fi to Cellular/LTE, often result in speech path loss due to the time required for IP address re-registration and lack of support for protocols like STUN, TURN, and ICE, leading to connectivity disruptions.
Innovation Solution
A method involving SIP and CSTA over SIP control signaling, using endpoint IDs that incorporate network connectivity mode, allowing seamless handover by maintaining simultaneous registrations and utilizing OS detection of connectivity changes to facilitate rapid transfer between networks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the SIP client re-registers with a new IP address after connectivity change, then the device can establish connection with the new network, but the speech path is lost during the re-registration period
Solution Approach 1:
The system performs preliminary registration with multiple network interfaces before connectivity changes occur. When a connectivity change happens, the SIP client already has alternative contact information registered, allowing immediate call transfer without speech path loss. The PBX is pre-configured with multiple contact URIs for the same user, enabling seamless failover.
2Reliability
If multiple protocols (STUN, TURN, ICE) are implemented for network traversal, then connectivity can be maintained across NAT boundaries, but the device complexity and implementation overhead increase
Solution Approach 1:
The patent extracts the complex network traversal protocols (STUN, TURN, ICE) from the client device and replaces them with a simpler SIP-based solution. The PBX server handles the complexity of network address translation by maintaining multiple contact URIs and routing calls appropriately, while the client only needs to implement basic SIP registration and connectivity status reporting.
3Adaptability or versatility
If the SIP client supports simultaneous registrations on multiple networks, then seamless handover is enabled, but the registration management and call transfer complexity increases
Solution Approach 1:
The PBX server acts as an intermediary that manages the complexity of multi-network registrations. The SIP client registers with the PBX over each available network interface, and the PBX stores multiple contact URIs associated with the same user. When handover is needed, the PBX mediates the call transfer by routing the call to the appropriate contact URI based on current connectivity status, shielding the client from complex registration management.
Data Source
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AI summary
A method for handing over a call from a first communication network (6) to a second communication network (7) is provided, wherein the method comprises the steps of registering, by a first mobile client (3), in particular, an IP-PBX VoIP client, running on a mobile device (2), the mobile device (2) with an IP-based PBX (4) for the first communication network (6), following a naming convention, by sending a registration message from the first mobile client (3) to the IP-based PBX (4), the registration message comprising an endpoint ID (epid), establishing an active conversation over the first communication network (6), detecting, on the mobile device (2), a connectivity change with respect to the first communication network (6), wherein the further steps of retrieving, by the first mobile client (3), the status of the call impacted by the connectivity change, and subsequently transferring the call to the second communication network (6) are carried out using SIP NOTIFY messages. Further, a communication system (1) for carrying out the method is provided.