Currently, advertised 4G is really just late-stage 3G. The two formats designated by the International Telecommunication Union (ITU) as “true 4G technologies” are:
LTE Advanced (Long Term Evolution Advanced)
WiMAX Release 2
There aren’t any large-scale deployments of either of these. However, their predecessors — LTE and WiMAX — are currently available.
As the wireless companies advertise it, 4G consists of three different technologies:
HSPA+ — This is more like an upgrade to regular 3G. HSPA+ offers faster speeds, but that take advantage of the same infrastructure. The first HSPA+ deployments began in 2008, and are now widely available throughout the world. T-Mobile’s “4G” network in the U.S. is HSPA+. Likewise, the first stage in AT&T’s 4G roll-out includes HSPA+.
LTE — LTE, or Long Term Evolution, doesn’t fully comply with 4G requirements. But it is what most people consider 4G. This is the system being adopted by Verizon, Metro PCS and AT&T in the U.S. Most European carriers have also committed to LTE. It is upgradable to LTE Advanced — so once that kicks in, it will be easy to upgrade an LTE phone into full-on 4G. Verizon started deploying its LTE network in December 2010. AT&T started rolling out 4G LTE in the second half of 2011. AT&T has a HSPA+ deployment, which it will use as a backup to LTE. Both AT&T and Verizon expect to have the bulk of their LTE deployments in place by the end of 2013