NEW YORK — Sprint Nextel Corp. said Monday that it has turned on its new wireless data network, providing a much-needed boost to the carrier, whose data speeds lag those of its largest competitors.

Sprint fired up the fourth-generation, or 4G, network in Atlanta, Dallas, Houston, Kansas City, San Antonio and some smaller surrounding cities on Sunday. It uses LTE, or Long-Term Evolution, technology already in use by Verizon Wireless and AT&T Inc.

Four smartphones and one mobile-hotspot device are capable of using the network.

PC Magazine got early access to the network a month ago, and found that it’s not quite as fast as Verizon’s and AT&T’s equivalents, but a big step up from Sprint’s older 3G, or third-generation, network and the 4G access it rents from Clearwire Corp.

Sprint, the third-largest U.S. cellphone carrier, doesn’t have as much available spectrum, or space on the airwaves, as the larger carriers do. That holds back its LTE speeds somewhat.

Verizon and AT&T also have much wider coverage on their LTE networks. Verizon covers 304 markets, or two-thirds of the U.S. population.

Sprint, which is based in Overland Park, Kan., is planning to expand LTE coverage this year and largely complete the network buildout next year. It’s planning to supplement its own LTE network with that of Clearwire, which has yet to fire up.

Sprint had said that Baltimore would also be among the first cities to get LTE, but it was missing from the initial lineup.