What this new competition means in terms of pricing and service remains to be seen, of course. Some believe that voice over IP using wireless broadband can hurt the mobile carriers, while others don't think such applications will have much impact. At the very least, more competitors providing more types of service can only be good for users, the experts agree.

4G: The tracks start to converge

Ultimately, as Debrecht suggested, the cellular carriers will adopt 4G. The problem is that nobody is quite sure what 4G means, since there are no standards. That isn't deterring Sprint, which, in announcing its nationwide mobile WiMax network, called that service 4G. For that network, it will use spectrum in the 2.5-GHz range that it amassed in large measure through its merger with Nextel.

"We call 4G the technology we choose for the 2.5-GHZ spectrum," said Sprint's Cannistra. "That has certain characteristics that are distinct from our 3G network." Among those characteristics are what Cannistra called "a global ecosystem that will allow for an inexpensive chip set that will be part of laptops. It's a very Wi-Fi-like model."

By that he's referring to how Wi-Fi developed into a worldwide success. A wide variety of vendors, ranging from consumer gadget manufacturers to enterprise networking company Cisco Systems Inc., sell products that support that wireless local-area networking standard. Intel, in particular, was very aggressive -- and successful -- in marketing Wi-Fi as a brand and says it will apply the same effort to mobile WiMax.