Those cities will be followed by Chicago, Philadelphia and Dallas in 2009, with Seattle, Charlotte and Honolulu switching over from Clearwire's existing fixed broadband network to true mobile WiMax. Their WiMax network in Baltimore, currently sold under the Xohm brand, will be expanded and will switch over to the Clear brand in 2009 as well.

In 2010, Clearwire expects to roll out New York, Boston, Washington DC, Houston, and the San Francisco Bay area. They're aiming to cover more than 80 markets, including 75% of the top 50 markets, by the end of 2010, Wolf said.

All the upcoming markets will get both voice-over-IP and data service, Wolf said. Existing Clearwire subscribers will need new modems for the new system, but that path will be smoothed because most of Clearwire's modems are leased, not owned, he said.

Clearwire owns a massive amount of spectrum nationwide, but their path to mobile WiMax domination has been rocky. After their merger with Sprint's Xohm unit last year, they now own two incompatible WiMax networks in Baltimore and Portland, along with 46 cities with non-WiMax fixed broadband and a lot of partially built networks.

While Wolf admitted that the Xohm merger slowed down Clearwire's rollout, he said they still have major advantages over their competition because of the large amount of spectrum they own. Verizon Wireless has said they'll be the first US carrier to launch the WiMax competitor technology LTE in early 2010.

"Our competitive advantage is not measured in months, but by the strength of our assets," Wolf said.

The new network will be compatible with many devices, Wolf said. There are more than 26 WiMax-compatible laptops, and by the end of March the company will launch a "personal hotspot" device which will let people turn a WiMax modem into a Wi-Fi hotspot. Clearwire also plans to launch their first 3G/4G modem this summer, which will roam on Clearwire's WiMax network and Sprint's 3G EVDO network.

Right now Sprint offers such a modem, the U300, but it only works on WiMax in Baltimore because of incompatibilities with Clearwire's other systems. Baltimore equipment including the U300 will start working in other Clear cities "in the coming weeks," Clearwire spokeswoman Susan Johnston said.

Even in an economic downturn, Clearwire can make money thanks to the desire fr wireless connectivity, Wolf said.

"Wireless communications continue to be an incredible opportunity for growth in our country ... and this phenomenon has created a tremendous business opportunity for companies that are positioned to capitalize on it," he said.