إل‌تي‌إي المتطور LTE Advanced، هومعيار اتصال محمول أولي، قُدم رسميا كمرشح نظام الجيل الرابع لITU-T في أواخر 2009، ووافق عليه الاتحاد الدولي للاتصالات، IMT-Advanced and expected to be finalized by 3GPP in early 2011. It is standardized by the 3rd Generation Partnership Project (3GPP) as a major enhancement of the 3GPP Long Term Evolution (LTE) standard.

خلفية

The LTE format was first proposed by NTT DoCoMo of Japan and has been adopted as the international standards.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 Scandinavia in December 2009 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 IMT Advanced 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 Releaseتسعة 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)." 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:

• Continual improvement to the LTE radio technology and architecture
• Scenarios and performance requirements for interworking with legacy radio access 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.
• Account taken of recent World Radiocommunication Conference (WRC-07) decisions regarding new IMT spectrum as well as existing frequency bands to ensure that LTE-Advanced geographically accommodates available spectrum for channel allocations above 20 MHz. Also, requirements must recognize those parts of the world in which wideband channels are not available.

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). A first set of 3GPP requirements on LTE Advanced has been approved in June 2008. 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.

مقترحات

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.

One of the important LTE Advanced benefits is the ability to take advantage of advanced topology networks; optimized heterogeneous networks with a mix of macros 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:

• Support for relay node base stations
• Coordinated multipoint (CoMP) transmission and reception
• UE Dual TX antenna solutions for SU-MIMO and diversity 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 Organized Networks methodologies
• Multiple carrier spectrum access.

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.

اطار زمني

Standardization is expected to be included in 3GPP Releaseعشرة timeframe. The importance and timeframe of LTE Advanced will of course largely depend on the success of LTE itself. LTE Advanced will be fully built on the existing LTE specification Releaseعشرة and not be defined as a new specification series. If possible LTE Advanced will be a software upgrade for LTE networks. Approval is expected by Spring, 2011. Trials have taken place based on pre-release equipment. Major vendors support software upgrades to final versions and ongoing improvements.

ثورات تكنولوجية

• In February 2007 NTT DoCoMo announced the completion of a 4G trial where they achieved a maximum packet transmission rate of approximately 5 Gbit/s in the downlink using 100 MHz frequency bandwidth to a mobile station moving at 10 km/h.
• In 2009, Rohde & Schwarz launched the CMW500 Wideband Communication Tester [2] the equipment that used by most of the major mobile manufacturer in testing GSM, WCDMA, HSPA, HSPA+, VAMOS, Wimax and LTE^[]
• In February 2011 at Mobile World Congress, Agilent Technologies demonstrated the industry's first test solutions for LTE-Advanced with both signal generation and signal analyzer solutions.

المصادر

• Qualcomm: http://qualcomm.com/technology
• 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, page 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, page 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.

الهوامش

وصلات خارجية

• LTE Advanced page on Qualcomm site
• 3GPP Official 3GPP Standardisation Page on LTE Advanced
• LTE Protocol Overview
• LTE Advanced overview
• Future use of LTE A femtocells
• LTE Encyclopedia
• LTE courses at Oxford University by Dr Harri Holma and Dr Antti Toskala
• Alcatel-Lucent chair on Flexible Radio, working on the concept of LTE small cells
• LTE Portal – 3GPP LTE / LTE Advanced Technology, dedicated portal created for information sharing, collaboration, and networking
• LTE Vertrag Portal

مراجع (White papers, technical papers, application notes)

• ITU-R Confers IMT-Advanced (4G) Status to 3GPP LTE – LTE Advanced is officially 4G!]
• The LTE / LTE Advanced Guide – a semi-annual publication on LTE / LTE Advanced, May and November 2010 publications are now available