Think of mobile broadband as a train station. On Track 1 is third-generation, or 3G, cellular data service, which operators have been deploying for the past couple of years. 3G service now covers most large and medium-size cities in the U.S., Europe and large swaths of the rest of the world, particularly in Asia.

Ephremides noted that the third-generation designation comes after 1G, which was analog voice service, and 2G, which was digital voice service. Early cellular data systems such as 1xRTT (1x Radio Transmission Technology) and EDGE (Enhanced Data Rates for GSM Evolution) often are called 2.5G.

Confusing matters is the fact that carriers with different technologies have deployed different flavors of 3G. For instance, carriers that have CDMA (Code Division Multiple Access) cellular networks, such as Verizon Wireless and Sprint in the U.S., have deployed the first generation of EV-DO (Evolution-Data Optimized) 3G service. UMTS (Universal Mobile Telecommunications System) and, more recently, HSDPA (High-Speed Downlink Packet Access), have been deployed by Cingular and other carriers worldwide that have GSM (Global System for Mobile Communications) networks. All these current forms of 3G provide typical download speeds of about 500 Kbit/sec. and typical upload speeds of less than 200 Kbit/sec.

In the short term -- say in the next year to 18 months -- many cellular operators will roll out enhanced versions of 3G that will increase speed, coverage and capacity, according to David Debrecht, Nokia Corp.'s director of technology for broadband wireless access. For instance, EV-DO Revision A and HSUPA (High-Speed Uplink Packet Access ) will increase typical download speeds to more than 1 Mbit/sec.

"Rev A is coming sooner than some people think," Peter Cannistra, a director in Sprint's Broadband Strategy Group, said in an interview. "We'll see typical speeds of 1 Mbit/sec., but upload speeds will be the biggest improvement over [first-generation] EV-DO -- it'll be two or three times as fast."