4G is the fourth generation of broadband cellular network technology, succeeding 3G. In the field of mobile communications, a “generation” generally refers to a change in the fundamental nature of the service, non-backward-compatible transmission technology, higher peak bit rates, new frequency bands, wider channel frequency bandwidth in Hertz, and higher capacity for many simultaneous data transfers (higher system spectral efficiency in bit/second/Hertz/site).
A 4G system must provide capabilities defined by the International Telecommunication Union (ITU) in international Mobile Telecommunications- Advanced (ITU- Advanced). Potential and current applications include amended mobile web access, IP telephony, gaming services, high-definition mobile TV, video conferencing, and 3D television. The first-release Long Term Evolution (LTE) standard was commercially deployed in Oslo, Norway, and Stockholm, Sweden in 2009, and has since been deployed throughout most parts of the world. In 2011/2012, the “real” 4G, which refers to all-Internet Protocol (IP) packet-switched networks giving mobile ultra-broadband (gigabit speed) access was launched.
The 4G system was originally envisioned by the DARPA, the US Defense Advanced Research Projects Agency. DARPA selected the distributed architecture and end-to-end Internet Protocol (IP) and believed at an early stage in peer-to-peer networking in which every mobile device would be both a transceiver and a router for other devices in the network, eliminating the spoke-and-hub weakness of 2G and 3G cellular systems. Unlike in 2.5G and 3G, in 4G systems, the circuit-switched infrastructure is abandoned and only a packet-switched network is provided. Also, in 4G traditional voice calls are replaced by IP telephony. 4G systems have Orthogonal frequency-division multiple access (OFDMA) multi-carrier transmission and other frequency-domain equalization (FDE) schemes, making it possible to transfer very high bit rates despite extensive multi-path radio propagation (echoes). The peak bit rate is further improved by smart antenna arrays for multiple-input multiple-output (MIMO) communications.
Despite the above striking benefits of 4G, there are also disadvantages that it comes with. 4G introduces a potential inconvenience for those who travel internationally or wish to switch carriers. In order to make and receive 4G voice calls, the subscriber handset must not only have a matching frequency band (and in some cases require unlocking), it must also have the matching enablement settings for the local carrier and/or country. While a phone purchased from a given carrier can be expected to work with that carrier, making 4G voice calls on another carrier’s network (including international roaming) may be impossible without a software update specific to the local carrier and the phone model in question, which may or may not be available.