Clearwire has begun selling laptop PC cards to its broadband access customers in Seattle, allowing them to take their once-fixed Internet connections out into the wider world. The portable, or nomadic, service uses Clearwire’s current proprietary network developed by former Clearwire subsidiary NextNet, but true mobility may be just around the corner as Clearwire prepares to launch its first WiMAX networks this year in conjunction with Sprint.

The nomadic service in Seattle hasn’t been officially launched and is only in the trial stages, but a Clearwire spokeswoman confirmed that the service is generally available to its customers in Seattle. The service requires a Motorola laptop card for $80 and a monthly service plan of $60 for unlimited data access.

The application, however, is considered portable, not mobile, since the network hasn’t been optimized for handoff between base stations.

Clearwire, however, is using rapid re-selection technology in the network that simulates mobility. The base stations don’t hand-off directly to one another, but as soon as a subscriber PC card leaves the cell coverage of one base station, the new cell-site rapidly recognizes the signal loss and quickly establishes a new connection. The re-selection is often fast enough that customers’ data sessions appear uninterrupted as they travel through the network, the Clearwire spokeswoman said.

True mobility, however, will come when Clearwire deploys Mobile WiMAX, a standards-based technology being rolled out by both Clearwire and partner Sprint. Clearwire’s current NextNet technology was designed primarily for fixed access through a fixed antenna and separate CPE, which is the configuration Clearwire sells to the majority of its broadband access customers in the U.S. and overseas.

Motorola bought NextNet and invested in Clearwire last year in exchange for its exclusive infrastructure relationship with the company. Earlier this year, Motorola ran a WiMAX trial for Clearwire in Portland, Ore., using its standards-based WiMAX platform and is in the process of developing a hybrid base station that will support both WiMAX and NextNet subscriber equipment.

Sprint and Clearwire are combining their resources to roll out a nationwide WiMAX footprint, though each carrier will be responsible for running the networks in their own territories. The new service will be called Xohm, and the two companies expect to launch their first commercial networks by the end of the year.