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To many non technical people FMC is still quite a new term. It stands for Fixed Mobile Convergency. I bet you are still confused after hearing this because I just give you three technical terms instead of one. There is another term MVC which is somewhat equavalent to FMC. MVC stands for Mobile Voice Continuity. Now this should make more sense. Basically it means to keep your active talking call (under Wi-Fi, cellular network, or in transition) without dropping it when you switch between networks.

I’m not talking about switching between AT&T and Sprint cellular networks but a switching between a Wi-Fi network to a cellular network. I will give you an example here. Say you order the Vonage VoIP service as your home telephone and you own a 3G Nokia E71 which is running AT&T service. Wouldn’t it be great if all your families and friends can reach you by just one number independent of of where you are? So you give them your Vonage number and you setup some FMC system at your house. When you are out of your home Wi-Fi network, FMC server automatically forwards any call that is made to your Vonage number to your cellular carrier AT&T. And you answer the call on the cellular side of your E71. And later on when you reach home where cellular coverage isn’t that great and any incoming call dial to your Vonage will ring your E71 at Wi-Fi side. In this way you never need to provide two numbers to your families and friends.

Sounds pretty cool isn’t it? However, so far the FMC system is not targeting to regular home office but enterprise. The major reasons are the following:

1. You need to be able to control/ config your VoIP system. Even though Vonage example sounds pretty reasonable, the configuration of that VoIP system is actually hidden from you. When you subscribe the service, Vonage provisions the telephony adapter for you already. You will not have the information of VoIP backend servers and account information for registration because they don’t want you to touch those. Therefore you cannot configure your E71 or any other Wi-Fi capable handset to share with your home Vonage service.

2. You need to be able to control/ config your Wi-Fi system on your Wi-Fi handset. In the above case it is the Nokia E71. Your E71 will need to inform FMC server when you step in and out of your home Wi-Fi network. This information is crucial because FMC server needs to know when to switch to the cellular network and when to switch back to the Wi-Fi network. Typically this is done by inserting a small software client in your phone. Nokia E71 does provide this capability for you to install a custom made FMC client on the phone. But I’m not sure about other Wi-Fi aware phones.

In an enterprise environment, the above information is generally controlled by the IT department. They are in charge of your office VoIP system which includes both your desktop phone and Wi-Fi capable phone. IT can configure your Wi-Fi 3G phone to take calls dialed to your desktop phone. And when you walk out of the office, your 3G phone notifies FMC server that you are out of Wi-Fi network and is switching to cellular network. When someone calls you, FMC server then forwards the call to your cellular number.

Well, too bad it is not easy to deploy this technology in your home. Isn’t it? Even though it’s a pity that you cannot have this fancy thing running in your house, it doesn’t hurt to learn some insights about it. I will introduce some basic idea of how FMC works in the following paragraphs.

1. Registration. All VoIP phones (your office desktop phone, Vonage TA…) need to register their numbers with the service provider before incoming calls can be routed. In Vonage case, Vonage has a registrar server which handles the registration. In an enterprise office, the office PBX will handle the registration from your desktop phone or 3G phone. When FMC system is deployed, FMC server is acting as a middle man between your phone and the registrar/ PBX. Your phone registers to FMC server and FMC server passes the registration to the registrar/ PBX. This way FMC server knows when your phone is under a Wi-Fi network. And registrar/ PBX knows that incoming calls to you should now go through your FMC server instead of directly ring your phone.

2. Call Setup. Now that phone registration is actually going through FMC system, both inoming and outgoing call will be routed through FMC system. In the incoming call case, PBX sends the call setup request to FMC then to your phone. FMC is acting as a proxy forwarding the Wi-Fi call to your phone if your phone is under a Wi-Fi network. If your phone is under a cellular network because of you are out of the office, FMC forwards the call setup request to your cellular side of your phone.

3. Handover. Assuming you already have a Wi-Fi call connected via FMC and you need to walk out of the office. When the Wi-Fi signal strength falls under certain threshold, FMC client on your phone notifies FMC server to dial an outbound call to your cellukar side of phone through PBX. Once that call-leg is established, FMC server uses this new call-leg to swap out the call-leg between FMC server and your Wi-Fi side of phone. This should be a seamless transition. Without your awareness, you are now using your cellular carrier to talk to the other party. The handover from cell side to Wi-Fi side is similar.

4. Single Number Reach/ Presentation. Once this FMC is setup, your families and friends no longer need to keep two numbers to contact you. The only number for you to contact the rest of world will be your Vonage or office number. When someone dials this number, FMC server forwards the call to either your Wi-Fi side or cellular side of the phone depends on where you are. This is called single number reach. When you are making outbound call, by default your phone will find its way back to FMC server and makes the outbound call via your Vonage or office number. People who receive your call will only see this number displayed as caller-ID. This is called single number presentation.

Many vendors have already rolled out FMC system and sell it to many enterprises. Maybe in the short future we shall see home office based FMC system on the market.