LTE Advanced

LTE Advanced, also named or recognized as LTE+, LTE-A or 4G+, is a 4G mobile cellular communication standard developed by 3GPP as a major enhancement of the Long Term Evolution (LTE) standard.

Three technologies from the LTE-Advanced tool-kit – carrier aggregation, 4x4 MIMO and 256QAM modulation in the downlink – if used together and with sufficient aggregated bandwidth, can deliver maximum peak downlink speeds approaching, or even exceeding, 1 Gbit/s. This is significantly more than the peak 300 Mbit/s rate offered by the preceding LTE standard. Later developments have resulted in LTE Advanced Pro (or 4.9G) which increases bandwidth even further.

LTE Advanced signal indicator in Android

LTE Advanced signal indicator on a Xiaomi smartphone

LTE Advanced signal indicator (4G+) on a Samsung Galaxy smartphones in Europe

The first ever LTE Advanced network was deployed in 2013 by SK Telecom in South Korea. In August 2019, the Global mobile Suppliers Association (GSA) reported that there were 304 commercially launched LTE-Advanced networks in 134 countries. Overall, 335 operators are investing in LTE-Advanced (in the form of tests, trials, deployments or commercial service provision) in 141 countries.

Name

LTE Advanced is also named (indicated as) LTE+, LTE-A, or (on Samsung Galaxy and Xiaomi smartphones) as 4G+. Such networks have also often been described as ‘Gigabit LTE networks’ mirroring a term that is also used in the fixed broadband industry.

History

The mobile communication industry and standards organizations have therefore started work on 4G access technologies, such as LTE Advanced.^[when?] At a workshop in April 2008 in China, 3GPP agreed the plans for work on Long Term Evolution (LTE). A first set of specifications were approved in June 2008. Besides the peak data rate 1 Gb/s as defined by the ITU-R, it also targets faster switching between power states and improved performance at the cell edge. Detailed proposals are being studied within the working groups.^[when?] The LTE+ format was first proposed by NTT DoCoMo of Japan and has been adopted as the international standard. It was formally submitted as a candidate 4G to ITU-T in late 2009 as meeting the requirements of the IMT-Advanced standard, and was standardized by the 3rd Generation Partnership Project (3GPP) in March 2011 as 3GPP Release 10.

The work by 3GPP to define a 4G candidate radio interface technology started in Release 9 with the study phase for LTE-Advanced. Being described as a 3.9G (beyond 3G but pre-4G), the first release of LTE did not meet the requirements for 4G (also called IMT Advanced as defined by the International Telecommunication Union) such as peak data rates up to 1 Gb/s. The ITU has invited the submission of candidate Radio Interface Technologies (RITs) following their requirements in a circular letter, 3GPP Technical Report (TR) 36.913, "Requirements for Further Advancements for E-UTRA (LTE-Advanced)." These are based on ITU's requirements for 4G and on operators’ own requirements for advanced LTE. Major technical considerations include the following:

Continual improvement to the LTE radio technology and architecture
Scenarios and performance requirements for working with legacy radio technologies
Backward compatibility of LTE-Advanced with LTE. An LTE terminal should be able to work in an LTE-Advanced network and vice versa. Any exceptions will be considered by 3GPP.
Consideration of recent World Radiocommunication Conference (WRC-07) decisions regarding frequency bands to ensure that LTE-Advanced accommodates the geographically available spectrum for channels above 20 MHz. Also, specifications must recognize those parts of the world in which wideband channels are not available.

Likewise, 'WiMAX 2', 802.16m, has been approved by ITU as the IMT Advanced family. WiMAX 2 is designed to be backward compatible with WiMAX 1 devices. Most vendors now support conversion of 'pre-4G', pre-advanced versions and some support software upgrades of base station equipment from 3G.

Proposals

The target of 3GPP LTE Advanced is to reach and surpass the ITU requirements. LTE Advanced should be compatible with first release LTE equipment, and should share frequency bands with first release LTE. In the feasibility study for LTE Advanced, 3GPP determined that LTE Advanced would meet the ITU-R requirements for 4G. The results of the study are published in 3GPP Technical Report (TR) 36.912.

One of the important LTE Advanced benefits is the ability to take advantage of advanced topology networks; optimized heterogeneous networks with a mix of macrocells with low power nodes such as picocells, femtocells and new relay nodes. The next significant performance leap in wireless networks will come from making the most of topology, and brings the network closer to the user by adding many of these low power nodes – LTE Advanced further improves the capacity and coverage, and ensures user fairness. LTE Advanced also introduces multicarrier to be able to use ultra wide bandwidth, up to 100 MHz of spectrum supporting very high data rates.

In the research phase many proposals have been studied as candidates for LTE Advanced (LTE-A) technologies. The proposals could roughly be categorized into:

Support for relay node base stations
Coordinated multipoint (CoMP) transmission and reception
UE Dual TX antenna solutions for SU-MIMO and diversity MIMO, commonly referred to as 2x2 MIMO
Scalable system bandwidth exceeding 20 MHz, up to 100 MHz
Carrier aggregation of contiguous and non-contiguous spectrum allocations
Local area optimization of air interface
Nomadic / Local Area network and mobility solutions
Flexible spectrum usage
Cognitive radio
Automatic and autonomous network configuration and operation
Support of autonomous network and device test, measurement tied to network management and optimization
Enhanced precoding and forward error correction
Interference management and suppression
Asymmetric bandwidth assignment for FDD
Hybrid OFDMA and SC-FDMA in uplink
UL/DL inter eNB coordinated MIMO
SONs, Self Organizing Networks methodologies

Within the range of system development, LTE-Advanced and WiMAX 2 can use up to 8x8 MIMO and 128-QAM in downlink direction. Example performance: 100 MHz aggregated bandwidth, LTE-Advanced provides almost 3.3 Gbit peak download rates per sector of the base station under ideal conditions. Advanced network architectures combined with distributed and collaborative smart antenna technologies provide several years road map of commercial enhancements.

The 3GPP standards Release 12 added support for 256-QAM.

A summary of a study carried out in 3GPP can be found in TR36.912.

Timeframe and introduction of additional features

Original standardization work for LTE-Advanced was done as part of 3GPP Release 10, which was frozen in April 2011. Trials were based on pre-release equipment. Major vendors support software upgrades to later versions and ongoing improvements.

In order to improve the quality of service for users in hotspots and on cell edges, heterogeneous networks (HetNets) are formed of a mixture of macro-, pico- and femto base stations serving corresponding-size areas. Frozen in December 2012, 3GPP Release 11 concentrates on better support of HetNet. Coordinated Multi-Point operation (CoMP) is a key feature of Release 11 in order to support such network structures. Whereas users located at a cell edge in homogenous networks suffer from decreasing signal strength compounded by neighbor cell interference, CoMP is designed to enable use of a neighboring cell to also transmit the same signal as the serving cell, enhancing quality of service on the perimeter of a serving cell. In-device Co-existence (IDC) is another topic addressed in Release 11. IDC features are designed to ameliorate disturbances within the user equipment caused between LTE/LTE-A and the various other radio subsystems such as WiFi, Bluetooth, and the GPS receiver. Further enhancements for MIMO such as 4x4 configuration for the uplink were standardized.

The higher number of cells in HetNet results in user equipment changing the serving cell more frequently when in motion. The ongoing work on LTE-Advanced in Release 12, amongst other areas, concentrates on addressing issues that come about when users move through HetNet, such as frequent hand-overs between cells. It also included use of 256-QAM.

First technology demonstrations and field trials

This list covers technology demonstrations and field trials up to the year 2014, paving the way for a wider commercial deployment of the VoLTE technology worldwide. From 2014 onwards various further operators trialled and demonstrated the technology for future deployment on their respective networks. These are not covered here. Instead a coverage of commercial deployments can be found in the section below.

LTE Advanced Pro

LTE Advanced Pro (LTE-A Pro, also known as 4.5G, 4.5G Pro, 4.9G, Pre-5G, 5G Project) is a name for 3GPP release 13 and 14. It is an evolution of LTE Advanced (LTE-A) cellular standard supporting data rates in excess of 3 Gbit/s using 32-carrier aggregation. It also introduces the concept of License Assisted Access, which allows sharing of licensed and unlicensed spectrum.

Additionally, it incorporates several new technologies associated with 5G, such as 256-QAM, Massive MIMO, LTE-Unlicensed and LTE IoT, that facilitated early migration of existing networks to enhancements promised with the full 5G standard.

Telstra in Australia deployed the very first LTE Advanced Pro network in January 2017.

Bibliography

Qualcomm

LTE for UMTS - OFDMA and SC-FDMA Based Radio Access,

ISBN 978-0-470-99401-6 Chapter 2.6: LTE Advanced for IMT-advanced, pp. 19–21.

e,:-(editor), LTE and the Evolution to 4G Wireless: Design and Measurement Challenges, Agilent Technologies Publication 2009,ISBN 978-0-470-68261-6, Chapter 8.7: Proving LTE Advanced, p. 425.
, et al.; Nokia Siemens Networks; LTE Advanced: The Path towards Gigabit/s in Wireless Mobile Communications^{[permanent dead link]}, Wireless VITAE'09.
Mobile Terminal Receiver Design: LTE and LTE-Advanced ,ISBN 9781119107309.

References

External links

LTE Advanced page on Qualcomm site
3GPP Official 3GPP Standardisation Page on LTE Advanced
Future use of LTE A femtocells Archived 2012-08-19 at the Wayback Machine
LTE-3GPP online decoders – 3GPP LTE / LTE Advanced online L3 messages decoders (24.008, 44.018, 44.060, etc.) supporting Release 14

Resources (white papers, technical papers, application notes)

LTE-Advanced Technology Introduction – white paper summarizing improvements on LTE known as LTE-Advanced Release 10
Introducing LTE-Advanced – Application Note
Introduction to LTE-Advanced Rel.11 Archived 2018-04-17 at the Wayback Machine – summarization of improvements specified in LTE-Advanced Release 11