Using Conference-Servers for SIP-based Vertical Handoff Technique for Cellular Networks
Lead Inventors: Henning G. Schulzrinne, Ph.D. Problem or Unmet Need:VoIP technology has been popular with landline phones to allow users to make phone calls to telephones or other computers via the internet. Cellular phones are the next emerging market for VoIP technology as it is becoming a standard to equip cell phones with WiFi capabilities. This is especially appealing to consumers as VoIP offers major cost benefits over traditional network such as cellular and PSTN, and much more flexibility. A challenge however, still exists in combining the cellular network and the wireless network without user intervention. Developed technology fills this void by implementing a new method to seamlessly transfer a call between different networks as needed. Using this technology, a transfer can take place automatically as needed during a call or data transfer session without the user perceiving any interruption.Fixed-Mobile Convergence (FMC) describes the seamless linking of a fixed network (e.g., a WiFi hot-spot connected to the internet) and a mobile network (e.g., a cellular network connected to switching centers). A handset that takes advantage of FMC and finds itself in range of multiple accessible networks can use the network of choice based on cost or signal strength. This transfer is desired to happen automatically during a call or data transfer session without the user perceiving the change.This technology achieves the hand off as follows: User A (with a regular phone) is in a phone call with User B (who has a phone and service plan equipped with this technology). User B enters an area with an accessible WiFi network, which is free to use with strong signal strength. User B's handset notifies the switching server and an extra call is added to handset B. When it is established that the connection over WiFi has been successfully added, the call to User B over the cellular network is dropped from the conference call, thus completing the handoff.
This technology requires no change to the existing network architecture or protocols, and can achieve seamless mobility. Only the users who want to achieve seamless transfer have to modify their handsets and no change is required for the party who called or was called. Software can be developed by developers and installed at the switching center to customize handoff solution.
The technology allows WiFi-enabled mobile handsets to seamlessly switch between communicating over a cellular network and the internet depending on the cost and signal strength. The technology makes possible transceivers in office buildings where the cellular network signal is weak, but the WiFi is strong: the technology solves communication problem using software rather than expensive hardware.
Fixed-Mobile Convergence (FMC) describes the seamless linking of a fixed network (e.g., a WiFi hot-spot connected to the internet) and a mobile network (e.g., a cellular network connected to switching centers). A handset that takes advantage of FMC a...
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