3GPP Long Term Evolution (LTE), is the latest standard in the mobile network technology tree that produced the GSM/EDGE and UMTS/HSxPA network technologies. It is a project of the 3rd Generation Partnership Project (3GPP), operating under a name trademarked by one of the associations within the partnership, the European Telecommunications Standards Institute.
The current generation of mobile telecommunication networks are collectively known as 3G (for "third generation"). Although LTE is often marketed as 4G, first-release LTE is a 3.9G technology since it does not fully comply with the IMT Advanced 4G requirements. The pre-4G standard is a step toward LTE Advanced, a 4th generation standard (4G) of radio technologies designed to increase the capacity and speed of mobile telephone networks. LTE Advanced is backwards compatible with LTE and uses the same frequency bands, while LTE is not backwards compatible with 3G systems.
MetroPCS, Verizon Wireless and AT&T Mobility in the United States and several worldwide carriers announced plans, beginning in 2009, to convert their networks to LTE. The world's first publicly available LTE-service was opened by TeliaSonera in the two Scandinavian capitals Stockholm and Oslo on the 14th of December 2009. LTE is a set of enhancements to the Universal Mobile Telecommunications System (UMTS) which was introduced in 3rd Generation Partnership Project (3GPP) Release 8. Much of 3GPP Release 8 focuses on adopting 4G mobile communication's technology, including an all-IP flat networking architecture. On August 18, 2009, the European Commission announced it will invest a total of €18 million into researching the deployment of LTE and the certified 4G system LTE Advanced.
While it is commonly seen as a mobile telephone or common carrier development, LTE is also endorsed by public safety agencies in the US as the preferred technology for the new 700 MHz public-safety radio band. Agencies in some areas have filed for waivers hoping to use the 700 MHz spectrum with other technologies in advance of the adoption of a nationwide standard.
The LTE specification provides downlink peak rates of at least 100 Mbit/s, an uplink of at least 50 Mbit/s and RAN round-trip times of less than 10 ms. LTE supports scalable carrier bandwidths, from 1.4 MHz to 20 MHz and supports both frequency division duplexing (FDD) and time division duplexing (TDD).
Part of the LTE standard is the System Architecture Evolution, a flat IP-based network architecture designed to replace the GPRS Core Network and ensure support for, and mobility between, some legacy or non-3GPP systems, for example GPRS and WiMax respectively.
The main advantages with LTE are high throughput, low latency, plug and play, FDD and TDD in the same platform, an improved end-user experience and a simple architecture resulting in low operating costs. LTE will also support seamless passing to cell towers with older network technology such as GSM, cdmaOne, UMTS, and CDMA2000. The next step for LTE evolution is LTE Advanced and is currently being standardized in 3GPP Release 10.
Much of the standard addresses upgrading 3G UMTS to 4G mobile communications technology, which is essentially a mobile broadband system with enhanced multimedia services built on top.
The standard includes:
* Peak download rates of 326.4 Mbit/s for 4x4 antennae, and 172.8 Mbit/s for 2x2 antennae (utilizing 20 MHz of spectrum).
* Peak upload rates of 86.4 Mbit/s for every 20 MHz of spectrum using a single antenna.
* Five different terminal classes have been defined from a voice centric class up to a high end terminal that supports the peak data rates. All terminals will be able to process 20 MHz bandwidth.
* At least 200 active users in every 5 MHz cell. (Specifically, 200 active data clients)
* Sub-5 ms latency for small IP packets
* Increased spectrum flexibility, with supported spectrum slices as small as 1.4 MHz and as large as 20 MHz (W-CDMA requires 5 MHz slices, leading to some problems with roll-outs of the technology in countries where 5 MHz is a commonly allocated amount of spectrum, and is frequently already in use with legacy standards such as 2G GSM and cdmaOne.) Limiting sizes to 5 MHz also limited the amount of bandwidth per handset
* In the 900 MHz frequency band to be used in rural areas, supporting an optimal cell size of 5 km, 30 km sizes with reasonable performance, and up to 100 km cell sizes supported with acceptable performance. In city and urban areas, higher frequency bands (such as 2.6 GHz in EU) are used to support high speed mobile broadband. In this case, cell sizes may be 1 km or even less.
* Good support for mobility. High performance mobile data is possible at speeds of up to 350 km/h, or even up to 500 km/h, depending on the frequency band used.
* Co-existence with legacy standards (users can transparently start a call or transfer of data in an area using an LTE standard, and, should coverage be unavailable, continue the operation without any action on their part using GSM/GPRS or W-CDMA-based UMTS or even 3GPP2 networks such as cdmaOne or CDMA2000)
* Support for MBSFN (Multicast Broadcast Single Frequency Network). This feature can deliver services such as Mobile TV using the LTE infrastructure, and is a competitor for DVB-H-based TV broadcast.
A large amount of the work is aimed at simplifying the architecture of the system, as it transits from the existing UMTS circuit + packet switching combined network, to an all-IP flat architecture system.
LTE standard can be used with different frequency bands. There are planned 700 MHz deployment in North America (Verizon); 900, 1800, 2600 MHz in Europe; 1800 and 2600 MHz in Asia; 1800 MHz in Australia. With some of the 1800 MHz deployment already functioning (e.g. in Poland).
Situation is similar to the GSM standard that is deployed worldwide on many GSM frequency bands, from which most popular are: 850, 900, 1800, 1900 MHz. That is why phones from one country often do not work in the other countries. For example one needs at least quad-band handset (850/900/1800/1900) to be sure his phone will work in both North America and Europe. Same problem consumer have with 3G technologies - the UMTS standard is deployed worldwide on 14 different UMTS frequency bands. For this reason even 3G-supporting phones will most likely provide fast internet access in no more than one region, even when it is quad-band phone and voice services will work, internet access will be slow.
Headsets and mobile modems stated to support 4G LTE will most likely support only a subset of LTE bands, so will not work with the other.