Companies are extremely uncomfortable talking about "4G" technologies per se, since the ITU has not defined 4G yet. Most companies believe that the characteristics of IMT-Advanced, as defined by the ITU, will represent a definition of 4G. Two expected requirements within IMT-Advanced are that technologies be OFDMA-based, and that they support 100Mbps for mobile applications. Long Term Evolution (LTE), Ultra Mobile Broadband (UMB), and 802.16m WiMAX all fulfill these requirements, and are the primary 4G technology contenders.

Each of the 4G technologies has a head cheerleader, with Intel supporting WiMAX, Ericsson touting LTE, and Qualcomm preferring UMB.

LTE, UMB and 802.16m WiMAX are expected to be initially implemented in 2010; however, looking at the slow uptake rate of EV-DO and HSPA, it may be 2012 and beyond. In-Stat actually forecasts that GSM/GPRS and GSM/EDGE handsets will still make up the majority of cellular handsets in 2011, with EV-DO and HSPA handsets expected to overtake 2G technologies in 2012. This, perhaps, points to a slow build-out of 4G networks, in which operators will maintain their 3G networks for a long time, running these as complementary to their 4G networks.

Initial implementations of LTE, UMB and 802.16m technologies may fall short of throughput and other expectations, with later enhancements to one or more of these technologies, or even some type of technology blend, actually bringing real 4G to the table.