4G

        It is a successor to the3G and2G families of standards. In 2009, the ITU-R organization specified the IMT-Advanced (International Mobile Telecommunications Advanced)requirements for 4G standards, setting peak speed requirements for 4G service 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 laptop computer wireless modems, smartphones, 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 Long term evolution (LTE) have been on the market since 2006 and 2009 respectively, and though often branded as 4G in marketing materials, the current versions of these technologies provide downstream peak bitrates of 144Mbit/s and 100 Mbit/s respectively. The ITU announced in December 2010 that WiMax, LTE, and HSPA+ are 4G technologies.[6]IMT-Advanced compliant versions of the above two standards are under development and called “LTE Advanced” and “Wireless MAN-Advanced” respectively. ITU has decided that “LTE Advanced” and “Wireless MAN-Advanced” should be accorded the official designation of IMT-Advanced. On December6, 2010, ITU announced that current versions of LTE, WiMax and other evolved 3Gtechnologies that do not fulfill "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."[7]As seen below, in all suggestions for 4G, the CDMA spread spectrum radio technology used in 3G systems andIS-95 is abandoned and replaced by OFDMA and other frequency-domain equalization schemes. This is combined with MIMO (Multiple In Multiple Out), e.g., multiple antennas, dynamic channel allocation and channel-dependent scheduling