4G

4G, or the fourth generation of cellular mobile communications, refers to a family of standards designed to provide high-speed mobile broadband and all-IP networks. Officially, 4G was defined by the International Telecommunication Union as IMT-Advanced, setting higher performance benchmarks than previous generations. The aim is to deliver sustained data rates, lower latency, and improved support for multimedia and mobility across wide areas.

The most widely deployed 4G technologies are LTE (Long-Term Evolution) and its enhanced form, LTE-Advanced, as well as the mobile version of IEEE 802.16e, known as Mobile WiMAX. LTE uses OFDMA for the downlink and SC-FDMA for the uplink, enabling higher spectral efficiency and peak data rates. LTE-Advanced adds features such as carrier aggregation, higher-order MIMO, higher-order modulation, and improved coding schemes to increase throughput and network capacity. Voice services typically transition to IP-based VoLTE. 4G networks are designed as all-IP networks, emphasizing data transmission over voice circuits and supporting seamless roaming, quality of service, and better support for applications like video streaming and cloud services.

Performance targets defined for IMT-Advanced include peak data rates up to about 1 Gbit/s for low-mobility scenarios and up to around 100 Mbit/s for high-mobility scenarios, with real-world speeds varying by network, spectrum, and user load. In practice, urban 4G networks commonly deliver tens of megabits per second, with higher speeds achievable in favorable conditions and with LTE-Advanced deployments. 4G significantly improved mobile broadband capabilities and laid the groundwork for continued evolution toward 5G.