4G refers to the fourth generation of cellular wireless standards. It is a successor to 3G and 2G families of standards. A 4G system is expected to provide a comprehensive and secure all-IP based solution where facilities such as ultra-broadband (giga-bit speed such as 100+ MiB/s) 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 available on the market since 2006[1] and 2009[2][3][4]respectively, and are often branded as 4G. Current versions of these technologies do not fulfill the ITU-R requirements of data rates approximately up to 1 Gbit/s for 4G systems.
In all suggestions for 4G, the CDMA spread spectrum radio technology used in 3G systems and IS-95 is abandoned and replaced by frequency-domain equalization schemes, for example multi-carrier transmission such as OFDMA. This is combined with MIMO (Multiple In Multiple Out), e.g., multiple antennas,dynamic channel allocation and channel-dependent scheduling.
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