Advanced Technologies in LTE/LTE-Advanced 3GPP Release 11 LTE/LTE-Advanced IMT-Advanced Further Development of LTE/LTE-Advanced – LTE Release 10/11 Standardization Trends – Advanced Technologies in LTE/LTE-Advanced †0 LTE was standardized at 3GPP, an international standards Radio Access Network Development Department Takehiro Nakamura organization, as 3GPP Release 8 in 2008 with an eye to Sadayuki Abeta†0 achieving dramatic improvements over the third-generation Hideaki Takahashi†0 mobile communications system. This was followed by the Satoshi Nagata†0 Journal standardization of LTE-Advanced as Release 10 to achieve even higher speeds and capacities in mobile communica- tions. At present, 3GPP is in the process of completing Release 11 specifications and beginning the formulation of Release 12. This article describes an overview on the pro- gression of LTE and LTE-Advanced standardization and summarizes the main function extensions in the above releases. Technical 3GPP Release 10 specifications (here- releases up to LTE Rel. 11. 1. Introduction inafter referred to as “Rel. 10”) making The 3rd Generation Partnership further enhancements to LTE. Never- 2. Progression of Project (3GPP), which had previously theless, market demands for enhanced 3GPP Specifications formulated the specifications for performance continued to grow and Since the formulation of W-CDMA WCDMA and High-Speed Packet diversify, and in 2012, 3GPP formulat- specifications as Release 99*3, many *1 DOCOMO Access (HSPA) as a third-generation ed Release 11 specifications (here- functions have been added at 3GPP in mobile communications system, formu- inafter referred to as “Rel. 11”) with the the form of new release specifications lated a radio system called Long Term aim of extending the functions and rais- in response to growing demands from Evolution (LTE) in 2008 as 3GPP ing the performance of LTE-Advanced. the market. The progression of these NTT Release 8 specifications (hereinafter In this article, we describe an overview specifications is shown in Figure 1. referred to as “Rel. 8”) in response to on how LTE specifications have pro- High-Speed Downlink Packet Access growing market demands. It then went gressed over the years and summarize (HSDPA)*4 and High-Speed Uplink on to formulate LTE-Advanced*2 as the main function extensions in the Packet Access (HSUPA)*5, which are ©2013 NTT DOCOMO, INC. *1 HSPA: A specification for increasing packet- Copies of articles may be reproduced only for per- data rates in W-CDMA and a general term sonal, noncommercial use, provided that the name encompassing HSDPA (see *4), which increases NTT DOCOMO Technical Journal, the name(s) of the speed from the base station to the mobile the author(s), the title and date of the article appear terminal, and HSUPA (see *5), which increas- in the copies. es the speed from the terminal to the base sta- tion. 4 NTT DOCOMO Technical Journal Vol. 15 No. 2 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 GSM/GPRS/EDGE enhancements Release 99 W-CDMA Release 4 1.28Mcps TDD Release 5 HSDPA Release 6 HSUPA, MBMS Release 7 HSPA+ (MIMO, HOM etc.) ITU-R M.1457 Release 8 LTE IMT-2000 Recommendation Minor LTE Release 9 enhancements Journal Formally approved by ITU-R Release 10 LTE-Advanced in January 2012 ITU-R M.2012 IMT-Advanced Recommendation Release 11 Figure 1 Progression of 3GPP specifications already in widespread use around the growing demands from the market for eration mobile communications system Technical world, are included in Release 5 and enhanced specifications as well as to then being standardized at ITU-R, Release 6, respectively. These 3GPP achieve a competitive mobile commu- 3GPP set out in 2008 to formulate spec- specifications related to W-CDMA and nications system. At present, the com- ifications for LTE-Advanced with the HSDPA/HSUPA are contained in the mercial deployment of LTE is progress- aim of making further performance International Mobile Telecommunica- ing well in Japan and elsewhere improvements and function extensions tions-2000 (IMT-2000)*6 Recommenda- throughout the world and its high level to LTE. Those specifications were stan- tion of the International Telecommuni- of performance is being recognized. dardized as Rel. 10 in 2011. LTE- cation Union-Radiocommunication sec- Following Rel. 8, technologies for Advanced was proposed as a candidate *7 DOCOMO tor (ITU-R) . achieving a number of function exten- technology for ITU-R IMT-Advanced, The LTE system was formulated at sions mainly in LTE upper layers were and deliberations at ITU-R concluded 3GPP at the end of 2007 as Rel. 8 spec- developed and incorporated in Release that LTE-Advanced did indeed satisfy ifications to provide a mobile commu- 9 specifications in 2009. the requirements of IMT-Advanced. In NTT nications system that could perform at a Next, as market demands continued January 2012, LTE-Advanced was for- dramatically higher level than to intensify and as the need arose to sat- mally approved as one radio interface HSDPA/HSUPA. The motivation isfy the requirements of IMT- of the IMT-Advanced system. behind this development was to satisfy Advanced*8, which is a true fourth-gen- The formulation of Rel. 11 specifi- *2 LTE-Advanced: Name of IMT-Advanced in as Release 5. dardized by 3GPP. It optimizes the coding rate, 3GPP. IMT-Advanced is the successor to the *4 HSDPA: A high-speed downlink packet trans- spread factor, and transmission power accord- IMT-2000 third-generation mobile communi- mission technology based on W-CDMA and ing to reception conditions at the base station. cations system. standardized by 3GPP. It optimizes the modu- *6 IMT-2000: The 3G mobile communications *3 Release 99: Indicates a version of 3GPP lation method and coding rate according to systems for increasing the speed of communi- specifications. Release 99 was formulated as reception conditions at the mobile terminal. cation. These are summarized in ITU-R recom- the initial 3GPP specification in 1999. The *5 HSUPA: A high-speed uplink packet transmis- mendations, and there are currently six varia- HSDPA (see *4) function was added in 2005 sion technology based on W-CDMA and stan- tions, including W-CDMA. NTT DOCOMO Technical Journal Vol. 15 No. 2 5 Advanced Technologies in LTE/LTE-Advanced cations as function extensions of LTE- CDMA/HSDPA/HSUPA was 5 MHz, support was initiated for a maximum of Advanced was energetically pursued at but LTE supported a maximum band- four MIMO layers in the uplink. 3GPP in 2012. Most of the specifica- width of 20 MHz beginning with its ini- tions were completed in 2012 and the tial specifications in Rel. 8. Then, in 3.3 Inter-cell Coordination freezing of those specifications was LTE Rel. 10, carrier aggregation was Technology announced in March 2013. adopted with the aim of maintaining As an effective measure for improv- backward compatibility while widening ing cell-edge performance, inter-cell 3. LTE Function Extensions bandwidth even further. This technique coordination technology has been in Various Releases makes it possible to bundle multiple actively studied for every release. First, At 3GPP, new functions have been frequency carriers of LTE Rel. 8 and to in Rel. 8, Inter-Cell Interference Coor- added in various releases and exten- support a maximum bandwidth of 100 dination (ICIC) technology was adopt- sions have been added to existing func- MHz. ed as an inter-base-station interface on tions by applying enhanced technolo- top of Fractional Frequency Reuse gies. The correspondence between main 3.2 Multi-antenna Technology (FFR)*10, which applies frequency reuse Journal function extensions and recent releases In its initial Rel. 8 specifications, between cells only at the cell edge. is shown in Figure 2. The following LTE adopted Multiple Input Multiple Then, in Rel. 10, a Heterogeneous Net- describes the progression of extensions Output (MIMO)*9 multi-antenna tech- work (HetNet) was adopted as a config- made for key LTE functions. nology in the downlink to increase uration that could efficiently improve transmission speed and capacity. In Rel. system capacity by overlaying large 3.1 Bandwidth Widening 8, the maximum number of layers cells (macrocell*11) and small cells (pic- Technology (number of spatially multiplexed trans- ocell*12/femtocell*13) having different Technical Widening the frequency bandwidth mission signals) was four, but in Rel. transmission power levels. This release is an effective means of improving user 10, the maximum number of layers in also initiated support of Transmission throughput. The bandwidth under W- the downlink was extended to eight and Power Control (TPC)*14 for large cells Release 8 Release 9 Release 10 Release 11 Carrier Variable bandwidth aggregation Bandwidth widening Max: 20 MHz technology Max: 100 MHz Max. 4 layers in MIMO Max. 8 layers in MIMO downlink Multi-antenna downlink Max. 4 layers in MIMO uplink DOCOMO technology FeICIC Inter-cell coordination ICIC HetNet/eICIC CoMP technology eDDA, EPDCCH Smartphone/machine MTC:CN overload MTC:RAN communications technology avoidance overload avoidance NTT MMSE-IRC Interference rejection technology for UE receiver Figure 2 Correspondence between main function extensions and releases *7 ITU-R: A department of ITU, an organization data rates of about 100 Mbit/s for high mobili- ent frequency band to cell-edge UE. that specializes in the field of telecommunica- ty and 1 Gbit/s for low mobility. *11 Macrocell: Cellular communication area with tions. It manages and coordinates international *9 MIMO: A signal transmission technology that a radius of several hundred meters to several matters related to radio communication, such improves communications quality and spectral tens of kilometers mainly covering outdoors. as radio regulations and spectrum use in vari- efficiency by using multiple transmitter and Usually, antennas are put up on towers or on ous countries.