"Hundreds of billions of dollars have been spent on creating robust cellular networks," Redman said. "There's nobody who can compete with that." However, while he doubts that companies like TowerStream can become major players, he acknowledges that new applications for wireless VOIP will emerge.

"It'll fill niches. It will help with in-building capabilities and for specific industry applications," Redman said. "But will it be disruptive to cellular? Companies like TowerStream might like to think so, but you look at a company like Cingular -- they're huge."

Sprint's Krueck falls somewhere in between Thompson's and Redman's points of view. Sprint has one advantage that no other U.S. cellular operator has -- a lot of licensed spectrum in the 2.5-GHz range, which it acquired when it merged with Nextel. The Federal Communications Commission has told Sprint it must use the spectrum or lose it.

Krueck confirmed what many industry analysts have been speculating about: Sprint plans to use that spectrum for wireless broadband and, potentially, for voice over IP. Nextel ran field trials of FLASH-OFDM before the merger, and Sprint currently is testing WiMax and UMTS TDD.

"We'll do trials this year on a couple of different wireless broadband technologies," Krueck said. "Sometime this year we'll actually select a technology, and sometime in 2007 we could start seeing something come into production."