It is the fourth generation of wireless communications technology. 4G can provide data throughput of 1 gbps for stationary users and 100 mbps for high mobility users, it can provide low latency and high reliability in the network with a benefit of clear HD voice calls as well. 4G is based on OFDM ( Orthogonal Frequency division multiple Access ) technology instead of WCDMA concept which was used by 3G systems. In OFDM technology, the digital signal is split into different narrow band frequencies which are modulated by data streams and then re-multiplexed to create the OFDM carrier. 4G technology can provide the broadband experience to users with good upload and download speed at their mobile devices. It can provide applications like mobile web access, IP telephony, HD video calls, video surveillance, video calling, interactive services, 3D television etc. The first release of 4G was LTE (Long term evolution) followed by LTE-Advanced and LTE-Advanced Pro. various releases was there to meet all IMT specific requirements like 4G core network should be all IP based packet, it should be able to share the network resources so that there will be more users per cell, it has scalable bandwidth concept rather than fixed bandwidth which was there in 2G and 3G technologies, scalable bandwidth as 5 - 20 MHz which could be expanded up to 40 MHz optionally with carrier aggregation. It has hard handover which means it should provide smooth handovers across heterogeneous networks.