LTE Advanced is a preliminary mobile communication standard, formally submitted as a candidate 4G system to ITU-T in late 2009, was approved into ITU, International Telecommunications Union, IMT-Advanced and expected to be finalized by 3GPP in early 2011.[1] It is standardized by the 3rd Generation Partnership Project (3GPP) as a major enhancement of the 3GPP Long Term Evolution (LTE) standard.
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The LTE format was first proposed by NTT DoCoMo of Japan and has been adopted as the international standards.[2] LTE standardization has come to a mature state by now 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 first release LTE networks are expected to be 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) (3GPP as well as 3GPP2).
Being described as a 3.9G (beyond 3G but pre-4G) technology the first release LTE does 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 Gbit/s. The ITU has invited the submission of candidate Radio Interface Technologies (RITs) following their requirements as mentioned in a circular letter. The work by 3GPP to define a 4G candidate radio interface technology started in Release 9 with the study phase for LTE-Advanced. The requirements for LTE-Advanced are defined in 3GPP Technical Report (TR) 36.913, "Requirements for Further Advancements for E-UTRA (LTE-Advanced)."[4] These requirements are based on the ITU requirements for 4G and on 3GPP operators’ own requirements for advancing LTE. Major technical considerations include the following:
Likewise, 802.16m, 'WiMAX 2', has been approved by ITU into the IMT Advanced family. WiMAX 2 is designed to be backward compatible with WiMAX 1/1.5 devices. Most vendors now support ease of conversion of earlier 'pre-4G', pre-advanced versions and some support software defined upgrades of core base station equipment from 3G.
The mobile communication industry and standardization organizations have therefore started to work on 4G access technologies such as LTE Advanced. At a workshop in April 2008 in China, 3GPP agreed the plans for future work on Long Term Evolution (LTE).[5] A first set of 3GPP requirements on LTE Advanced has been approved in June 2008.[6] Besides the peak data rate 1 Gbit/s that fully supports the 4G requirements 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.
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 Advance technologies. The proposals could roughly be categorized into:[8]
Within the range of system development, LTE-Advanced and WiMAX 2, can use up to 8x8 MIMO and 128 QAM. Example performance: 100MHz aggregated bandwidth, LTE-Advanced provides almost 3.3Gbit 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]
Standardization work was done in 3GPP Release 10, which was frozen in April 2011.[10] Trials have taken place based on pre-release equipment. Major vendors support software upgrades to final versions and ongoing improvements.
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