Prices and terms for the WiMax service that Sprint Nextel launched on Monday stand up against other wired and wireless broadband options, but a key measure -- coverage -- remains a question mark.

The Xohm service is to be the first national broadband service in the U.S. using WiMax high-speed wireless technology. The service, which launched commercially in Baltimore on Monday, carries a US$35-per-month regular price for home broadband and $45 per month for mobile use. (Introductory rates of $25 and $30, respectively, will last for six months.)

That's for a service with download speeds between 2M bps (bits per second) and 4M bps, comparable with many DSL (Digital Subscriber Line) and cable modem services in the U.S. A major advantage of WiMax is that customers can buy a mobile client device and use it on the road wherever the network is available. The service is priced for customers depending on their devices, so those who only buy and register a large, tabletop modem can get the less-expensive home plan. (They can travel with that modem and set it up elsewhere in Xohm's service area if they choose.)

If Sprint's speed claims are accurate, WiMax is something new in the Internet-access market: Internet access that can take the place of DSL or cable and also travel with you. Clearwire is rolling out its own WiMax network, starting in Portland, Oregon, that will be combined with Sprint's after the companies finish forming a joint venture later this year. Verizon Wireless and AT&T Mobility expect to start deploying another 4G (fourth-generation) technology, LTE (Long-Term Evolution), within the next couple of years and are speeding up their 3G networks in the meantime.

But although Xohm waves the mobility flag high, it will probably rely on stationary home users for its early success, analysts said. The problem is that roving users will find it available in so few places. Baltimore is the only commercial market for Xohm now, and just two more cities -- Chicago and Washington, D.C. -- are scheduled to come online this year. Even the coverage in the Baltimore area, which Sprint lays out in an interactive map on the Xohm Web site, is patchy today and doesn't look like it will cover most of the area until late next year. However, most of downtown does seem to be covered now.

The lack of coverage makes it hard to fairly compare Xohm with cellular data offerings, analysts said. That's the multibillion-dollar challenge for Sprint and its partners.