The promise of fixed-mobile convergence (FMC) is real. Analysts suggest dual-mode telephony could save businesses up to 30% on their annual telecom bills. Too bad the U.S. carriers aren't on board with the idea yet.Dual-mode phones use both licensed spectrum from wireless network operators, such as AT&T, and unlicensed spectrum, such as the nifty Wi-Fi hot spot you have in your home or office, to make calls. The phones can sense when they are entering one of the networks and switch from one to the other seamlessly and automatically. What this boils down to is, you should be able to save your precious cell phone minutes and use "free" minutes over a Wi-Fi network instead.

With the increasing penetration of cell phones in the enterprise, it's no surprise that telecom bills are an increasing pain in the neck for businesses.

T-Mobile is the only one of the major carriers to openly trial dual-mode handsets in the U.S., but has sadly limited the trial to select areas in Washington State. Customers pay an extra fee for the privilege of using the Wi-Fi systems along with T-Mobile's regular cellular network. AT&T and Verizon Wireless would not comment on their plans. Handset manufacturers Nokia and Motorola have both invested in their own versions of the technology, and I've even seen several demonstrations.

A recent report, though, goes further to scare the major operators away from FMC. Remember that 30% FMC will save enterprises on their telecom bills? Where do you think it comes from? Yep, you're right, directly from the bottom line of wireless operators to the tune of $3.3 billion by 2011.

So, who wants to take bets on how soon we'll see FMC in the U.S.?