إل‌تي‌إي المتطور

إل‌تي‌إي المتطور LTE Advanced، هو معيار 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.[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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خلفية

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 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 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)."[3] 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).[4] A first set of 3GPP requirements on LTE Advanced has been approved in June 2008.[5] 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:[6]

  • 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.[7]

اطار زمني

Standardization is expected to be included in 3GPP Release 10 timeframe.[8] 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 Release 10 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

المصادر

الهوامش

  1. ^ Stefan Parkvall, Erik Dahlman, Anders Furuskär et al; Ericsson, Robert Syputa, Maravedis; http://www.itu.int/ITU-R/information/promotion/e-flash/2/article4.html "International Telecommunications Union, IMT-Advanced global platform standar; LTE Advanced - Evolving LTE towards IMT-Advanced; Vehicular Technology Conference, 2008. VTC 2008-Fall. IEEE 68th 21-24 Sept. 2008 Page(s):1 - 5.
  2. ^ Faster cell phone services planned
  3. ^ "Requirements for further advancements for Evolved Universal Terrestrial Radio Access (E-UTRA) (LTE-Advanced)"
  4. ^ Beyond 3G: “LTE Advanced” Workshop, Shenzhen, China
  5. ^ 3GPP specification: Requirements for further advancements for E-UTRA (LTE Advanced)
  6. ^ Nomor Research: White Paper on LTE Advanced
  7. ^ 3GPP Technical Report: Feasibility study for Further Advancements for E-UTRA (LTE Advanced)
  8. ^ Nomor Research Newsletter: The way of LTE towards 4G
  9. ^ NTT DoCoMo Achieves World's First 5 Gbit/s Packet Transmission in 4G Field Experiment
  10. ^ Agilent Technologies Introduces Industry's First LTE-Advanced Signal Generation, Analysis Solutions[1]

وصلات خارجية

مراجع (White papers, technical papers, application notes)

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