4g and Wifi

4G stands for the fourth generation of cellular wireless standards. It is a successor to 3G and 2G families of standards. Speed requirements for 4G service set the peak download speed at 100 Mbit/s for high mobility communication (such as from trains and cars) and 1 Gbit/s for low mobility communication (such as pedestrians and stationary users).[1]
A 4G system is expected to provide a comprehensive and secure all-IP based mobile broadband solution to smartphones, laptop computerwireless modems and other mobile devices. Facilities such as ultra-broadband Internet access, IP telephony, gaming services, and streamed multimedia may be provided to users.
Pre-4G technologies such as mobile WiMAX and first-release 3G Long term evolution (LTE) have been on the market since 2006[2] and 2009[3][4][5] respectively, and are often branded as 4G. The current versions of these technologies did not fulfill the original ITU-R requirements of data rates approximately up to 1 Gbit/s for 4G systems. Marketing materials use 4G as a description for Mobile-WiMAX and LTE in their current forms.
IMT-Advanced compliant versions of the above two standards are under development and called “LTE-Advanced” and “WirelessMAN-Advanced” respectively. ITU has decided that “LTE-Advanced” and “WirelessMAN-Advanced” should be accorded the official designation of IMT-Advanced. On December 6th, 2010, ITU announced that current versions of LTE, WiMax and other evolved 3G technologies that do not fulfull 'IMT-Advanced' requirements could be considered '4G', provided they represent forerunners to IMT-Advanced and "a substantial level of improvement in performance and capabilities with respect to the initial third generation systems now deployed." [6]
In all suggestions for 4G, the CDMA spread spectrum radio technology used in 3G systems and IS-95 is abandoned and replaced byOFDMA and other frequency-domain equalization schemes.[citation needed] This is combined with MIMO (Multiple In Multiple Out),...