(Long Term Evolution) The next-generation 3G technology for both GSM and CDMA cellular carriers. Expected in the 2010 time frame, LTE uses a different air interface and packet structure than current 3G systems, which are GSM's UMTS (WCDMA and HSPA) and CDMA's EV-DO. However, it is envisioned that GSM and CDMA2000 carriers will eventually migrate to LTE to provide an interoperable cellular system worldwide.
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.
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).
The IP Multimedia Subsystem (IMS), which provides an integrated framework for all telecommunications based on IP, is also integrated into LTE.
4G - LTE-Advanced/IMT-Advanced
Approved in 2008, LTE is defined by the 3G Partnership Project in the 3GPP Release 8 specification. With download speeds up to 173 Mbps, LTE is considerably faster than GSM's HSPA and CDMA's EV-DO, but is still considered a 3G technology.
The International Telecommunications Union (ITU) established the "IMT-Advanced" moniker for its 4th generation systems, superseding "IMT-2000," which defines 3G. As a result, 3GPP defined "LTE-Advanced" (LTE-A) as the name of a compliant implementation of IMT-Advanced, and an LTE-Advanced specification is expected in 3GPP Release 10 in the 2010 time frame.
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