3GPP Long Term Evolution 3G/4G

3GPP Long Term Evolution (LTE) is a standard for wireless communication of high-speed data. It is based upon GSM/EDGE and Universal Mobile Telecommunications System/High Speed Packet Access (UMTS/HSPA) network technologies^. The standard is maintained as a project of the3rd Generation Partnership Project (3GPP), operating under a name trademarked by one of the associations within the partnership, the European Telecommunications Standards Institute (ETSI).

The goal of LTE is to increase the capacity and speed of wireless data networks utilizing cutting-edge hardware and Digital Signal Processing (DSP) techniques that have recently been developed. Its wireless interface is incompatible with 2G and 3G networks, and so it must be operated on separate wireless spectrum.

Features of LTE include an all-IP flat network architecture, end-to-end QoS including provisions for low-latency communications, peak download rates nearing 300 Mbps and upload rates of 75 Mbps, capacity exceeding 200 active users per cell, the ability to manage fast-moving mobiles, and support for multi-cast and broadcast streams.

Sprint Nextel (through LightSquared), MetroPCS, Verizon Wireless, and AT&T Wireless in the United States along with several worldwide carriers are building out LTE networks. The world's first publicly available LTE-service was opened by TeliaSonera in the Scandinavian capitals Stockholmand Oslo on 14 December 2009.

 

LTE is the brand name for emerging and developed technologies that comprise the existing 3G and 4G networks. The LTE specification provides downlink peak rates of at least 100 Mbit/s, uplink peak rates 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 Evolved Packet Core (EPC), 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 also supports seamless passing to cell towers with older network technology such as GSM, cdmaOne, UMTS, and CDMA2000. The evolution of LTE is LTE Advanced, which was 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 299.6 Mbit/s for 4x4 antennas, and 150.8 Mbit/s for 2x2 antennas (using 20 MHz of spectrum).
• Peak upload rates of 75.4 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.