Towerstream Corp. has launched a high-speed wireless service for professional firms and small businesses in Center City, one of several companies investing in the wireless sector in Philadelphia.

AT&T Inc. recently expanded its wireless phone network into Philadelphia's subway system for daily riders, and Sprint Nextel, Clearwire, and Comcast Corp. began selling next-generation wireless Internet service in the region.

T-Mobile USA Inc. said yesterday it added wireless service in the Market East station and the City Hall station on the Broad Street line, two of the busiest stations on the subway system. T-Mobile also is upgrading its 3G network in the region with higher speeds in a test project, the first in the nation, Mark McDiarmid, a T-Mobile director of engineering, said last week.

"I don't have any concerns through 2010 and into 2011 of T-Mobile being on the top of the pile for performance," he said.

Philadelphia is Towerstream's 10th expansion market in the nation.

Jeff Thompson, president and chief executive officer of the Rhode Island company, said last week it was investing $3 million to $5 million into wireless cell sites in the Philadelphia region in the next two years.

Towerstream also applied for an additional $8 million in federal stimulus funds for Philadelphia, Thompson said. He expects to hear whether Towerstream has won the grant in the next two weeks or early next year.

Towerstream's typical customer is a small business that employs about 35 workers. Its prices are 30 percent to 50 percent below the phone companies', Thompson said.

Towerstream uses lightly regulated radio spectrum for the WiMAX service, which connects to a main cell site through an 8-inch dish.