Long Term Evolution (LTE) is a mobile network technology that is being deployed by mobile operators on both the GSM and the CDMA technology paths. Depending on the spectrum available, live LTE networks can deliver very fast data speeds of up to 100Mbps in the downlink and 50Mbps in the uplink.
Designed to be backwards-compatible with GSM and HSPA, LTE incorporates Multiple In Multiple Out (MIMO) technology, the Orthogonal Frequency Division Multiple Access (OFDMA) air interface in the downlink and Single Carrier FDMA in the uplink. This combination provides high levels of spectral efficiency and network performance, coupled with high network capacity and low latency. LTE will support spectrum channel bandwidths from 1.4 MHz to 20 MHz and can operate in both paired spectrum (in FDD mode) and unpaired spectrum (in TDD mode).
Although both LTE and WiMAX use the OFDMA air interface, LTE’s compatibility with existing GSM and HSPA networks enables mobile operators to continue to provide a seamless service across LTE and existing deployed networks.
LTE networks have now been launched by mobile operators Europe, Asia and North America. In the U.S., the largest CDMA operator, Verizon Wireless, for example, launched commercial LTE services at the end of 2010.
LTE-Advanced is designed to enable a further step change in data rates. Incorporating higher order MIMO (4×4 and beyond) and allowing multiple carriers to be bonded together into a single stream, LTE-Advanced’s target is to achieve peak data rates of 1Gbps.
Other innovations being incorporated into LTE-Advanced include the use of non-contiguous frequency ranges (to alleviate congestion in the increasingly-crowded core spectrum bands), base stations that will be able to connect themselves to an operator’s network and the seamless integration of femtocells using so-called self-organising network techniques.
Standards body 3GPP intends LTE-Advanced to be its technology candidate for the ITU-R IMT-Advanced process, which is intended to identify ‘4G’ technologies.