The next-generation 4G technology for both GSM and CDMA cellular carriers is referred to as LTE or Long Term Evolution. Approved in 2008 with download speeds up to 173 Mbps, LTE was defined by the 3G Partnership Project in the 3GPP Release 8 specification.
LTE uses a different air interface and packet structure than previous 3G systems, which are GSM’s UMTS (WCDMA and HSPA) and CDMA’s EV-DO. However, it is envisioned that all GSM and CDMA2000 carriers will eventually migrate to LTE to provide an interoperable cellular system worldwide.
LTE, Officially 4G, is considerably faster than GSM’s HSPA and CDMA’s EV-DO but was considered a 3G technology by the ITU until late 2010. Along with WiMAX 2, the ITU previously designated LTE-A (LTE-Advanced) as the true 4G evolution. In late 2010, the ITU widened its definition to include regular LTE, WiMAX and HSPA+ as bona fide 4G technologies since they are considerably faster than existing 3G networks. See IMT-Advanced.
E-UTRA/OFDMA, IP and IMS
LTE uses the Evolved UMTS Terrestrial Radio Access (E-UTRA) air interface, which is based on OFDMA and is a departure from the TDMA used in GSM and the CDMA used in GSM/UMTS and CDMA2000 (see GSM and CDMA). In addition, rather than proprietary packet structures, LTE is based entirely on IP packets, and voice travels over IP (VoIP). The IP part of LTE is called “Evolved Packet System” (EPS), which was previously called “System Architecture Evolution” (SAE).