LTE, also known as 3GPP LTE or 3G LTE (Long Term Evolution), represents the next-generation radio interface developed by 3GPP. It serves as the evolutionary successor to the 3GPP air interface UMTS (evolved UTRA) and its associated radio access network (evolved UTRAN). LTE offers significantly enhanced peak data rates while reducing latency. This technology is designed as a fully packet-optimized radio-access system, improving spectral efficiency, increasing system capacity, and reducing the cost per gigabyte. LTE is capable of delivering a broader range of services, offering users a superior experience. The initial deployment of LTE occurred in 2009.

Key technical objectives for LTE include:

1. Substantial increase in peak data rates, with an instantaneous data rate of 100 Mbit/s on the downlink and 50 Mbit/s on the uplink within a 20 MHz channel.
2. Improved user throughput, targeting a threefold increase on the downlink and a twofold increase on the uplink.
3. Enhanced data rates at the cell edge, aiming for a twofold improvement to provide higher data rates across wide-area coverage without the need for additional cell sites.
4. Improved spectrum efficiency.
5. Scalable bandwidth, supporting channel widths of 1.25, 1.6 (TDD only), 2.5, 5, 10, 15, or 20 MHz based on the user’s data rate requirements.
6. Optimization for both low and high mobile speeds.
7. Compatibility with earlier releases and other systems, including mobility support for RLAN and non-3GPP air interfaces.

LTE employs Orthogonal Frequency Division Multiplexing (OFDM) on the downlink to handle multipath effects and enable flexible bandwidth allocation. OFDM employs numerous individual sub-carriers with a 15 kHz spacing. OFDM parameters can be adjusted to support cell sizes exceeding 120 km in radius.

On the uplink, LTE utilizes a single carrier combined with Frequency Division Multiple Access (FDMA) (SC-FDMA). FDMA is chosen for power-efficient user terminal transmission, and the bandwidth can be adjusted to accommodate the user’s data rate requirements. User separation is achieved primarily by assigning distinct time intervals on an allocated frequency. Frequency separation is also employed in cases where terminals have limited transmission power or insufficient data to transmit.

3G LTE can make use of existing 2G and 3G spectrum allocations, as well as new spectrum resources.