By lighting up WiMax services in Austin and San Antonio, Texas Monday, Sprint Nextel continues to lead in 4G services, but its rivals are rapidly planning to catch up.

The carrier is reselling service from Clearwire, of which it is the majority owner, and Sprint is offering mobile and fixed Internet options. With WiMax, Sprint is delivering up to 6 Mbps to users on the go, and it also offering a hybrid service that utilizes its EV-DO 3G network in areas where WiMax is not available.

"Sprint continues to lead the charge in rolling out wireless 4G in cities across America and the momentum continues to build," said Todd Rowley, VP of Sprint 4G, in a statement. "Our aggressive expansion of Sprint 4G will include many new devices and capabilities that create increased performance and productivity while enhancing personal lifestyles on the go."

Sprint already has 4G services in multiple markets across the country, and it is aiming to blanket more than 120 million people in WiMax by the end of the year, including Boston, New York, San Francisco, and Houston. Sprint's competitors are not standing still though, as AT&T, T-Mobile, and Verizon Wireless are all taking steps to better capitalize on the growing demand for mobile data services.

AT&T is in the middle of upgrading its 3G network to provide up to 7.2 Mbps downstream speed, and it also plans to begin deploying 4G networks some time in 2011. Verizon Wireless has laid out aggressive 4G plans based on Long-Term Evolution technology, and it plans to have 25 to 30 markets covered by the end of 2010.

T-Mobile has lagged behind the competitors with high-speed mobile data for years, but it appears to be trying to make up for lost time by outlining an ambitious 3G upgrade strategy. The fourth-largest carrier said it will cover 200 million people by the end of the year, and its entire 3G network will provide 7.2 Mbps downlink speed. The company will also begin upgrading its network to HSPA+ in the middle of 2010, and this has the potential to provide 21 Mbps downstream.

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