answer:“Over the last year or so, we have seen the introduction of two so-called 4G technologies: LTE (Long Term Evolutions) and WiMAX. In the U.S., Sprint is using the WiMAX standard for its networks and Verizon is using LTE. With CLEAR, Clearwire is also offering a WiMAX-based broadband network that targets consumers who want fast Internet speeds on their laptops and at home, though the reach of the company’s network is still limited to a select number of cities in the U.S. One of the major differences – besides the faster speeds – between these networks and 3G is that voice – which until now travelled over a separate line – now runs over the same network as the data, and telephony on the phone basically becomes a VoIP application similar to Skype. With speeds of over 100 Mbps, wireless networks can easily rival the speeds of wired connections While no actual 4G spec has been finalized yet, the current expectation is that the standard will call for a minimum speed of 1 to 1.5 Gbps. According to a recent report (PDF) by Rysavy Research for 3G Americas, the first networks that will actually fulfill these official requirements for 4G will probably use the LTE-Advanced specifications. The final specs for LTE-Advanced won’t be completed until March 2011, though, and the first networks with support for this standard won’t go online until 2012. The other real 4G spec that is currently being discussed is the IEEE 802.16m standard, backed by the WiMAX Forum.” Source