1、UNIT21 4G Network 21-1 Technical Part21-2 Reading Material 21-1 Technical Part 21-1-1 Definition 4G is the fourth generation of cell phone mobile communications standards.It is a successor of the third generation(3G)standards.A 4G system provides mobile ultra-broadband Internet access,for example to
2、 laptops with USB wireless modems,to smartphones,and to other mobile devices.Conceivable applications include amended mobile web access,IP telephony,gaming services,high-definition mobile TV,video conferencing and 3D television.Two 4G candidate systems are commercially deployed:The Mobile WiMAX stan
3、dard(at first in South Korea in 2006),and the first-release Long term evolution(LTE)standard(in Scandinavia since 2009).It has however been debated if these first-release versions should be considered as 4G or not.See technical definition.In the U.S.Sprint Nextel has deployed Mobile WiMAX networks s
4、ince 2008,and MetroPCS was the first operator to offer LTE service in 2010.USB wireless modems have been available since the start,while WiMAX smartphones have been available since 2010 and LTE smartphones since 2011.Equipment made for different continents are not always compatible,because of differ
5、ent frequency bands.Mobile WiMAX and LTE smartphones are currently(April 2012)not available for the European market.21-1-2 Introductions 1.Origin of LTEIn March 2008,the International Telecommunications Union-Radio communications sector(ITU-R)specified a set of requirements for 4G standards,named th
6、e International Mobile Telecommunications Advanced(IMT-Advanced)specification,setting peak speed requirements for 4G service at 100 megabits per second(Mbit/s)for high mobility communication(such as from trains and cars)and 1 gigabit per second(Gbit/s)for low mobility communication(such as pedestria
7、ns and stationary users).Since the above mentioned first-release versions of Mobile WiMAX and LTE support much less than 1 Gbit/s peak bit rate,they are not fully IMT-Advanced compliant,but are often branded 4G by service providers.On December 6,2010,ITU-R recognized that these two technologies,as w
8、ell as other beyond-3G technologies that do not fulfill the IMT-Advanced requirements,could nevertheless be considered“4G”,provided they represent forerunners to IMT-Advanced compliant versions and“a substantial level of improvement in performance and capabilities with respect to the initial third g
9、eneration systems now deployed”.Mobile WiMAX Release 2(also known as WirelessMAN-Advanced or IEEE 802.16m)and LTE Advanced(LTE-A)are IMT-Advanced compliant backwards compatible versions of the above two systems,standardized during the spring 2011,and promising peak bit rates in the order of 1 Gbit/s
10、.Services are expected in 2013.As opposed to earlier generations,a 4G system does not support traditional circuit-switched telephony service,but all-internet protocol(IP)based communication such as IP telephony.As seen below,the spread spectrum radio technology used in 3G systems,is abandoned in all
11、 4G candidate systems and replaced by OFDMA multi-carrier transmission and other frequency-domain equalization(FDE)schemes,making it possible to transfer very high bit rates despite extensive multi-path radio propagation(echoes).The peak bit rate is further improved by smart antenna arrays for multi
12、ple-input multiple-output(MIMO)communications.2LTE AdvancedLTE Advanced(Long-term-evolution Advanced)is a candidate for IMT-Advanced standard,formally submitted by the 3GPP organization to ITU-T in the fall 2009,and expected to be released in 2012.The target of 3GPP LTE Advanced is to reach and surp
13、ass the ITU requirements.LTE Advanced is essentially an enhancement to LTE.It is not a new technology but rather an improvement on the existing LTE network.This upgrade path makes it more cost effective for vendors to offer LTE and then upgrade to LTE Advanced which is similar to the upgrade from WC
14、DMA to HSPA.LTE and LTE Advanced will also make use of additional spectrum and multiplexing to allow it to achieve higher data speeds.Coordinated Multi-point Transmission will also allow more system capacity to help handle the enhanced data speeds.Release 10 of LTE is expected to achieve the LTE Adv
15、anced speeds.Release 8 currently supports up to 300 Mbit/s download speeds which is still short of the IMT-Advanced standards.3.Development of Long Term Evolution(LTE)The pre-4G technology 3GPP Long Term Evolution(LTE)is often branded“4G-LTE”,but the first LTE release does not fully comply with the
16、IMT-Advanced requirements.LTE has a theoretical net bit rate capacity of up to 100 Mbit/s in the downlink and 50 Mbit/s in the uplink if a 20 MHz channel is used and more if multiple-input multiple-output(MIMO),i.e.antenna arrays,are used.The below Figure 21-1 shows the 4G wireless devices.Figure 21
17、-1 4G wireless devicesThe physical radio interface was at an early stage named High Speed OFDM Packet Access(HSOPA),now named Evolved UMTS Terrestrial Radio Access(E-UTRA).The first LTE USB dongles do not support any other radio interface.The worlds first publicly available LTE service was opened in
18、 the two Scandinavian capitals Stockholm(Ericsson and Nokia Siemens Networks systems)and Oslo(a Huawei system)on 14 December 2009,and branded 4G.The user terminals were manufactured by Samsung.Currently,the three publicly available LTE services in the United States are provided by MetroPCS,Verizon W
19、ireless,and AT&T.As of April 2012,US Cellular also offers 4G LTE.Sprint Nextel has also stated its considering switching from WiMAX to LTE in the near future.4.Mobile WiMAX(IEEE 802.16e)The Mobile WiMAX(IEEE 802.16e-2005)mobile wireless broadband access(MWBA)standard(also known as WiBro in South Kor
20、ea)is sometimes branded 4G,and offers peak data rates of 128 Mbit/s downlink and 56 Mbit/s uplink over 20 MHz wide channels.In June 2006,the worlds first commercial mobile WiMAX service was opened by KT in Seoul,South Korea.Sprint Nextel has begun using Mobile WiMAX,as of September 29,2008 branded a
21、s a“4G”network even though the current version does not fulfil the IMT Advanced requirements on 4G systems.21-1-3 Application Case or Example Application:The coexistence of LTE and GSM/UMTSLTE is not standalone,but co-exist/interworks with GSM/UMTS.The current radio access networks are separated.In
22、the future,GSM/UMTS/LTE will tend to be converged into one network.However,this process will last at least 10 years.During this stage,5-band 3-mode will co-exist on one site and interwork with each other to provide end users consistence experience for a long time.Therefore,LTE is not standalone,but
23、co-exists&interworks with GSM/UMTS networks.The key requirements for this network modernization procedure are as below:Multi-Technology co-exists at least 10 years;up to 5 frequencies per site One single platform to support GSM/UMTS/LTE and FDD/TDD simultaneously The platform:common HW&upgradeable S
24、W for convergence&evolution One utility set:Co-RRM,Co-TRM,Co-OAM,Co-RNP/RNO,Co-Site/Antenna/Feeder The combination of radio wireless equipment frequency The below slide(Figure 21-2)shows the transformation and evolution from the current GSM/3G network to LTE/4G network.Figure 21-2 Evolution of 2G/3G
25、 to 4G 21-2 Reading Material 21-2-1 Reading Comprehension The Path to 4G Will Take Many TurnsA race is going on right now and its a heated one.Its a race to the next generation of untethered communications4G mobile broadband wireless.The prize for reaching the finish line first or even finishing at
26、all could be huge.Yet that finish line keeps moving,as the fourth generation(4G)isnt yet fully defined.In fact,spectrum wont be allocated until 2007.Standards probably wont be complete until the year after that.Right now,thought,many teams across the globe are investing a lot of time,effort,money,an
27、d talent to make sure that they are in the race.Any road race has three basic fundamentals:a track,a car,and a crew.The worldwide effort to develop 4G system and devices could be considered a race.Just as the track itself sets the boundary conditions for the race,standards set the boundaries for tel
28、ecommunications.The first topic of this article is standards development for 4G,which ranges from the International Telecommunications Union(ITU)to national and regional standards development organizations(SDOs).The people who are tolling away day in and day out to make sure their team wins the race
29、-the“pit crew”of 4G research are the engineers working in industry partnerships,high-tech corporations,and university research labs.The second section of this article will focus on their efforts.Lastly,every team needs a vehicle to propel them to the final goalthe finish line.In the race to 4G,the r
30、ace cars are the underlying technologies that enable communications to be more seamless,useful,and powerful.Words&Expressionsuntethered communications 无线通信 broadband n.宽带spectrum n.波谱；范围，系列 allocate vt.分配，分派invest vt&vi.投资，花费 fundamental n.基本原则，基本法则crew n.一队(或一组)工作人员 boundary n.分界线；界限，范围telecommunic
31、ation 电信International Telecommunications Union 国际电信联盟 toil away 长时间辛苦的工作 corporation n.公司vehicle n.交通工具，车辆；传播媒介，手段 propel vt.推进，推动seamless adj.准确无误的，完全符合逻辑21-2-2 Exercises I.Multiple Choices.1.According to the passage,the spectrum will be allocated by the year of _.A.2006 B.2007 C.2008 D.20092.Accor
32、ding to the 2nd Paragraph,it is essential for a real road race to have_.A.a track,a car and a bounfaryB.a track,a car and a standardC.a track,a crew and a bounfaryD.a track,a crew and a crew3.It can be learned from the passage that,the“ITU(Para.3)”refer to _.A.International Technology UnionB.Interna
33、tional Telecommunications UnitC.International Telephones UnionD.International Telecommunications Union4.What does the“pit crew”mean according to the passage?A.The engineers.B.The seaman.C.The racres.D.The corporations.5.It can be learned from the passage that the last section of this article will ma
34、inly _.A.discuss some new races related to 4GB.examine the types of the application of 4GC.discuss some major technologies involved in the raceD.examine different between 4G races and real racesII.Read&Translate.1.Right now,thought,many teams across the globe are investing a lot of time,effort,money
35、,and talent to make sure that they are in the race.2.The people who are tolling away day in and day out to make sure their team wins the race-the“pit crew”of 4G research-are the engineers working in industry partnerships,high-tech corporations,and university research labs.3.In the race to 4G,the race cars are the underlying technologies that enable communications to be more seamless,useful,and powerful.
