What is 4G ?
Although the term 4G has been tossed around a lot in relation to WiMAX, the reality is that the International Telecommunications Union has not yet to define what 4G actually means. According to most telecommunication professionals, the main technologies that are associated with this position include WiMAX, Long Term Evolution (LTE) and Ultra Mobile Broadband (UMB).
To better understand the nature of the players involved in so-called 4G technologies, Wikipedia provides some helpful definitions for LTE and UMB (for a definition of WiMAX, see above)
Ultra Mobile Broadband : An ultra fast technology that supports more than an order of magnitude increase in broadband data throughput rates to economically deliver IP-based voice, multimedia, broadband, information technology, entertainment, and consumer electronic services within most kinds of devices. A platform that supports several wireless services within a full mobility environment and thus differentiates itself from Wi-Fi, WiMAX, UWB, etc. Ultra high-speeds that are in the order of 100s of megabits per second; next-generation capabilities, beyond 3G.
Long Term Evolution : 3GPP LTE (Long Term Evolution) is the name given to a project within the Third Generation Partnership Project to improve the UMTS mobile phone standard to cope with future requirements. Goals include improving efficiency, lowering costs, improving services, making use of new spectrum opportunities, and better integration with other open standards. The LTE project is not a standard, but it will result in the new evolved release 8 of the UMTS standard, including mostly or wholly extensions and modifications of the UMTS system.