LTE (telecommunication)

LTE (telecommunication)
Name	Long-Term Evolution
Caption	A simplified diagram of an LTE network architecture.
Developed by	3GPP
Introduced	2009
Industry	Telecommunications
Predecessor	3GPP UMTS / HSPA
Successor	5G NR

LTE (telecommunication). Long-Term Evolution, commonly known as LTE, is a standard for wireless broadband communication developed by the 3GPP (3rd Generation Partnership Project). It represents a major advancement from previous 3G technologies like UMTS and HSPA, offering significantly higher data rates, reduced latency, and a simplified, all-IP network architecture. Often marketed as "4G LTE," it laid the foundational framework for the subsequent development of true 4G standards and the eventual transition to 5G NR.

Overview

LTE was conceived as a project within the 3GPP to ensure the long-term competitiveness of the 3GPP family of standards against other evolving technologies like WiMAX. The first version, 3GPP Release 8, was frozen in December 2008, with the first commercial services launched by TeliaSonera in Stockholm and Oslo in 2009. Unlike its 3G predecessors, LTE utilizes new radio access technologies, primarily OFDMA for the downlink and SC-FDMA for the uplink, and operates with an entirely packet-switched core network known as the System Architecture Evolution (SAE). This design supports high-speed mobile internet access, enabling services like mobile IPTV, VoLTE, and robust machine-to-machine communication.

Technical specifications

The radio interface of LTE employs Orthogonal Frequency-Division Multiple Access (OFDMA) in the downlink and Single-carrier FDMA (SC-FDMA) in the uplink, which improves spectral efficiency and power amplifier performance in user devices. It supports flexible bandwidths from 1.4 MHz to 20 MHz and utilizes advanced antenna techniques like MIMO (Multiple Input, Multiple Output), including configurations like 2x2 and 4x4 MIMO. Key performance targets defined by the 3GPP included peak data rates of 300 Mbps downlink and 75 Mbps uplink under ideal conditions, with a user-plane latency of less than 10 milliseconds. Modulation schemes range from QPSK to 64-QAM and, in later releases, 256-QAM.

Architecture

The LTE system architecture is divided into two main parts: the Evolved UMTS Terrestrial Radio Access Network (E-UTRAN) and the Evolved Packet Core (EPC). The E-UTRAN consists solely of eNodeB base stations, which handle radio communications and connect directly to the EPC, eliminating the network controller role found in UMTS. The EPC, defined as part of the System Architecture Evolution, includes key nodes like the Mobility Management Entity (MME), the Serving Gateway (S-GW), and the Packet Data Network Gateway (P-GW). This flat, all-IP architecture simplifies the network, reduces latency, and supports seamless mobility and integration with other access networks, including GSM, W-CDMA, and CDMA2000.

Evolution and LTE-Advanced

To meet the full International Telecommunication Union (ITU) requirements for 4G, known as IMT-Advanced, the 3GPP developed LTE-Advanced, standardized beginning with 3GPP Release 10. Key enhancements introduced include Carrier Aggregation, which allows the combination of multiple component carriers for wider bandwidths, advanced MIMO techniques like 8x8 downlink, and support for Heterogeneous Networks (HetNets) with small cells like picocells and femtocells. Further evolutions in releases like 3GPP Release 13 introduced features such as LTE-Unlicensed (LTE-U) and enhanced Machine Type Communication (eMTC) for the Internet of Things. These advancements ensured LTE's relevance as a precursor to 5G NR.

Deployment and spectrum

LTE has been deployed globally by mobile operators such as Verizon Wireless, AT&T Mobility, Vodafone, and China Mobile across a wide range of frequency bands. Due to varying national regulations and legacy allocations, LTE operates in both paired Frequency-division duplexing (FDD) and unpaired Time-division duplexing (TDD) spectrum modes, known as LTE-TDD. It utilizes bands from below 1 GHz (e.g., 700 MHz, 800 MHz) for wide-area coverage to higher frequencies like 2.6 GHz and even 3.5 GHz for capacity. The fragmentation of spectrum necessitated multi-band devices, and refarming of legacy bands used for GSM and CDMA became a common strategy for operators.

Services and performance

LTE enabled a transformative shift in mobile services, providing the necessary performance for high-definition mobile video streaming, real-time online gaming, and cloud-based applications. A critical service introduced was Voice over LTE (VoLTE), which carries voice calls as data packets over the IP network, providing higher quality and faster call setup compared to circuit-switched fallback. For public safety, FirstNet in the United States built a dedicated LTE network. Typical real-world user experiences offered download speeds ranging from 5 to 50 Mbps, with latency around 30-50 ms, vastly improving upon HSPA and enabling the modern app ecosystem dominated by platforms like Netflix and YouTube.

Category:3GPP standards Category:Mobile telecommunications Category:4G