Three different flavors of wireless, 802.16m WiMax, LTE, and UMB, are the top three contenders for the fourth generation of wireless technology. Each has pluses and minuses, as well as corporate backing, says In-Stat.Which one will prevail in the end remains to be determined. The International Telecommunications Union is still working on the definition of what 4G will actually entail and won't have those specs in place for another year or two. In the meantime, the technologies continue to evolve.

Long Term Evolution, or LTE, is where GSM-based wireless systems such as HSPA are headed. But even what constitutes LTE hasn't been defined yet (it should be sometime next month). Ericsson has a big stake in LTE and is standing firmly behind it.

Ultra Mobile Broadband merges a handful of air interface standards, including CDMA, TDM, and OFDM, into a single technology. Backed by Qualcomm, it also takes advantage of MIMO antenna arrays to boost data speeds.

WiMax of the 802.16m variety is mobile WiMax on steroids. It also will use MIMO antennas to reach wireless data speeds of 1 Gbps, according to the IEEE. With Intel's large investment in WiMax technology, it isn't surprising to know where its support will fall.

Each of these holds promise. In-Stat believes there are a number of factors that will affect how 4G is eventually rolled out. One is that the ITC will likely require any 4G technology to be OFDMA-based and be capable of 100 Mbps in WWAN applications. Because of the slow acceptance of HSPA and EV-DO 3G handsets, however, 4G implementations will not begin until about 2010.

Says In-Stat, "Realistically, initial implementations of LTE, UMB and 802.16m WiMax may fall short of throughput and other expectations, with later enhancements, or even some type of technology combination, actually bringing real 4G to the table."