LTE Advanced

LTE Advanced is a mobile communication standard and a major enhancement of the Long Term Evolution (LTE) standard. It was formally submitted as a candidate 4G system 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.^[1]

Background

The LTE format was first proposed by NTT DoCoMo of Japan and has been adopted as the international standard.^[2] LTE standardization has matured to a state where changes in the specification are limited to corrections and bug fixes. The first commercial services were launched in Sweden and Norway in December 2009^[3] followed by the United States and Japan in 2010. More LTE networks were deployed globally during 2010 as a natural evolution of several 2G and 3G systems, including Global system for mobile communications (GSM) and Universal Mobile Telecommunications System (UMTS) in the 3GPP family as well as CDMA2000 in the 3GPP2 family.

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)."^[4] 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.

The mobile communication industry and standards organizations have therefore started work on 4G access technologies, such as LTE Advanced. At a workshop in April 2008 in China, 3GPP agreed the plans for work on Long Term Evolution (LTE).^[5] A first set of specifications were approved in June 2008.^[6] 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.

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.^[7]

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:^[8]

• 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.

A summary of a study carried out in 3GPP can be found in TR36.912.^[9]

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, heterogenous networks (HetNet) are formed of a mixture of macro-, pico- and femto base stations serving corresponding-size areas. Frozen in December 2012, 3GPP Release 11^[10] 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 ^[11] 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.

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 LTE networks. These are not covered here. Instead a coverage of commercial deployments can be found in the section below.

Company	Country	Date	Note
NTT DoCoMo	Japan	000000002007-02-01-0000February 2007	[12] The operator announced the completion of a 4G trial where it achieved a maximum packet transmission rate of approximately 5 Gbit/s in the downlink using 12 transmit and 12 receive antennas and 100 MHz frequency bandwidth to a mobile station moving at 10 km/h.
Agilent Technologies	Spain	000000002011-02-01-0000February 2011	[13] The vendor demonstrated at Mobile World Congress the industry's first test solutions for LTE-Advanced with both signal generation and signal analysis solutions.
Ericsson	Sweden	000000002011-06-01-0000June 2011	[14] The vendor demonstrated LTE-Advanced in Kista.
touch	Lebanon	000000002013-04-01-0000April 2013	[15] The operator trialed LTE-Advanced with Chinese vendor Huawei and combined 800 MHz spectrum and 1.8 GHz spectrum. touch achieved 250 Mbit/s.
Vodafone	New Zealand	000000002013-05-01-0000May 2013	[16] The operator trialed LTE-Advanced with Nokia Networks and combined 1.8 GHz spectrum and 700 MHz spectrum. Vodafone achieved just below 300 Mbit/s.
A1	Austria	000000002013-06-01-0000June 2013	[17] The operator trialed LTE-Advanced with Ericsson and NSN using 4x4 MIMO. A1 achieved 580 Mbit/s.
Turkcell	Turkey	000000002013-08-01-0000August 2013	[18] The operator trialed LTE-Advanced in Istanbul with Chinese vendor Huawei. Turkcell achieved 900 Mbit/s.
Telstra	Australia	000000002013-08-01-0000August 2013	[19] The operator trialed LTE-Advanced with Swedish vendor Ericsson and combined 900 MHz spectrum and 1.8 GHz spectrum.
SMART	Philippines	000000002013-08-01-0000August 2013	[20] The operator trialed LTE-Advanced with Chinese vendor Huawei and combined 2.1 GHz spectrum and 1.80 GHz spectrum bands and achieved 200 Mbit/s.
SoftBank	Japan	000000002013-09-01-0000September 2013	[21] The operator trialed LTE-Advanced in Tokyo with Chinese vendor Huawei. Softbank used the 3.5 GHz spectrum band and achieved 770 Mbit/s.
beCloud/ MTS	Belarus	000000002013-10-01-0000October 2013	[22] The operator trialed LTE-Advanced with Chinese vendor Huawei.
SFR	France	000000002013-10-01-0000October 2013	[23] The operator trialed LTE-Advanced in Marseille and combined 800 MHz spectrum and 2.6 GHz spectrum. SFR achieved 174 Mbit/s.
EE	United Kingdom	000000002013-11-01-0000November 2013	[24] The operator trialed LTE-Advanced in London with Chinese vendor Huawei and combined 20 MHz of 1.8 GHz spectrum and 20 MHz of 2.6 GHz spectrum. EE achieved 300 Mbit/s which is equal to category 6 LTE.
O2	Germany	000000002013-11-01-0000November 2013	[25] The operator trialed LTE-Advanced in Munich with Chinese vendor Huawei and combined 10 MHz of 800 MHz spectrum and 20 MHz of 2.6 GHz spectrum. O2 achieved 225 Mbit/s.
SK Telecom	South Korea	000000002013-11-01-0000November 2013	[26] The operator trialed LTE-Advanced and combined 10 MHz of 850 MHz spectrum and 20 MHz of 1.8 GHz spectrum. SK Telecom achieved 225 Mbit/s.
Vodafone	Germany	000000002013-11-01-0000November 2013	[27] The operator trialed LTE-Advanced in Dresden with Swedish vendor Ericsson and combined 10 MHz of 800 MHz spectrum and 20 MHz of 2.6 GHz spectrum. Vodafone achieved 225 Mbit/s.
Telstra	Australia	000000002013-12-01-0000December 2013	[28] The operator trialed LTE-Advanced with Swedish vendor Ericsson and combined 20 MHz of 1.8 GHz spectrum and 20 MHz of 2.6 GHz spectrum. Telstra achieved 300 Mbit/s which is equal to category 6 LTE.
Optus	Australia	000000002013-12-01-0000December 2013	[29] The operator trialed TD-LTE-Advanced with Chinese vendor Huawei and combined two 20 MHz channels of 2.3 GHz spectrum. Optus achieved over 160 Mbit/s.

Deployment

An LTE Advanced Base Station installed in Iraq for Broadband Wireless Internet Service Provision

A complete coverage of commercial LTE-Advanced deployments (Cat.4 with CA and Cat.6 onwards) including launch dates can be found in List of LTE networks.

Devices

At the time of its launch in 2007, LTE Advanced was not supported by any smartphone, but only by a small number of routers. The first capable smartphones wouldn't arrive until late 2013. While no smartphone is currently capable of 1 Gbit/s+, there are smartphones that can reach 300 Mbit/s to 600 Mbit/s under ideal conditions.

See also

• LTE
• E-UTRA
• LTE User Equipment Category
• Simulation of LTE Networks

Bibliography

• Qualcomm
• Harri Holma, Antti Toskala, LTE for UMTS - OFDMA and SC-FDMA Based Radio Access, John Wiley & Sons 2009, ISBN 978-0-470-99401-6 Chapter 2.6: LTE Advanced for IMT-advanced, pp 19–21.
• Moray Rumney (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
• Preben E. Mogensen, Tommi Koivisto, Klaus I. Pedersen 1, et al.; Nokia Siemens Networks;LTE Advanced: The Path towards Gigabit/s in Wireless Mobile Communications, Wireless VITAE'09.

References

External links

• LTE Advanced page on Qualcomm site
• 3GPP Official 3GPP Standardisation Page on LTE Advanced
• Future use of LTE A femtocells
• LTE-3GPP online decoders - 3GPP LTE / LTE Advanced online L3 messages decoders (24.008, 44.018, 44.060, etc.)

Resources (white papers, technical papers, application notes)

• LTE-Advanced Technology Introduction - this white paper summarizes improvements on LTE known as LTE-Advanced Rel.10
• Introducing LTE-Advanced - Application Note
• Introduction to LTE-Advanced Rel.11 - Summarization of improvements specified in LTE-Advanced Release 11.

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