Call Forwarding for Mobile Devices Switching Between WLAN and WWAN
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Solution Overview
Problem
Mobile communication devices operating in both wireless local area networks (WLANs) and wireless wide area networks (WWANs) face challenges in seamless reachability due to unique identification numbers associated with each network, leading to service disruptions when switching between them.
Innovation Solution
Implementing call forwarding techniques where the mobile device transmits messages to switch voice calls from one network identification number to another, ensuring continuous reachability by forwarding calls from a WLAN identification number to a WWAN number and vice versa, using RF transceiver circuitry and antennas for both networks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the mobile device uses unique identification numbers for WLAN and WWAN networks, then the device can be reached through both networks separately, but the device becomes out-of-service on one network when operating on the other network
Solution Approach 1:
The patent introduces call forwarding as an intermediary mechanism that bridges the WLAN and WWAN networks. When the mobile device switches from WLAN to WWAN, call forwarding messages are transmitted to redirect calls from the WLAN identification number to the WWAN identification number, ensuring continuous reachability across network boundaries without requiring the device to be simultaneously active on both networks
Solution Approach 2:
The patent implements preliminary action by proactively transmitting call forwarding activation messages before the device fully switches networks. The mobile device sends a call forwarding activation message to the first network (WLAN) before disconnecting, ensuring that incoming calls are automatically redirected to the second network (WWAN) where the device will be active, thus preventing service interruption
2Productivity
If the mobile device switches operations between WLAN and WWAN, then the device can optimize communication based on location and factors, but call reachability is disrupted during switching
Solution Approach 1:
The patent reduces service interruption time by performing preliminary actions during network switching. The mobile device transmits call forwarding activation messages to the current network before fully disconnecting, and sends call forwarding deactivation messages to the new network after connecting. This overlapping transition ensures call reachability is maintained throughout the switching process, minimizing productive time loss
Solution Approach 2:
The patent ensures continuity of the useful action (call reachability) during network switching by maintaining active call forwarding status throughout the transition. The device keeps call forwarding enabled on both networks during the switching period, ensuring that incoming calls are continuously routed to the device regardless of which network is currently active, thus eliminating gaps in service
Data Source
AI summary
A mobile device operates in a WLAN for VoIP communications, which includes registering with registrar server functionality of a SIP proxy server with a SIP identity which is further communicated to a location server. In response to an incoming voice call from a caller via a telephone network, the mobile device receives an INVITE request which is issued from a gateway and forwarded from the SIP proxy server. The mobile device sends a response to the SIP proxy server which is communicated to the caller via the gateway. When switching from the WLAN to the cellular network, the mobile device sends via the WLAN to the location server a message for forwarding voice calls directed to the SIP identity to the telephone number. The mobile device also sends via the cellular network a message for canceling the forwarding of voice calls directed to telephone number to the SIP identity.