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1、IT专业英语UNIT19 3G NetworkUNIT 19 3G Network UNIT 19 3G Network UNIT 19 3G Network 19-1 Technical Part 19-1-1 Definition 3G or 3rd generation mobile telecommunications is a generation of standards for mobile phones and mobile telecommunication services fulfilling the International Mobile Telecommunicat

2、ions-2000(IMT-2000)specifications by the International Telecommunication Union.Application services include wide-area wireless voice telephone,mobile Internet access,video calls and mobile TV,all in a mobile environment.UNIT 19 3G Network 19-1-2 Introductions Several telecommunications companies mar

3、ket have extended to wireless mobile Internet services as 3G,indicating that the advertised service is provided over a 3G wireless network.Services advertised as 3G are required to meet IMT-2000 technical standards,including standards for reliability and speed(data transfer rates).UNIT 19 3G Network

4、 UNIT 19 3G Network UNIT 19 3G Network The TD-SCDMA(Time Division Duplex Synchronous Code Division Multiple Access)radio interface was commercialized in 2009 and is only offered in China.The system bandwidth is 1.6MHz,chip rate is 1.28Mbps.TD-SCDMA is an important feature of 3GPP R4 standards and ad

5、mitted to the UTRA TDD standard by 3GPP in 1999.UNIT 19 3G Network The original and most widespread radio interface is called W-CDMA(Wideband Code Division Multiple Access).The system bandwidth is 5MHz,chip rate is 3.84Mbps.The Figure 19-1 shows the network architecture of WCDMA.UNIT 19 3G Network F

6、igure 19-1 The network architecture of WCDMA telecommunications industryUNIT 19 3G Network The CDMA2000 system,first offered in 2002,standardized by 3GPP2,used especially in North America and South Korea,sharing infrastructure with the IS-95 2G standard.The cell phones are typically CDMA2000 and IS-

7、95 hybrids.The latest release EVDO Rev B offers peak rates of 14.7 Mbit/s downstream.The Figure 19-2 shows the deployment of CDMA2000 1X EVDO.UNIT 19 3G Network Figure 19-2 Network deployment of CDMA 2000 1X EVDOUNIT 19 3G Network The above systems and radio interfaces are based on spread spectrum r

8、adio transmission technology.While the GSM EDGE standard(“2.9G”),DECT(Digital Enhanced Cordless Telecommunication)cordless phones and Mobile WiMAX standards formally also fulfill the IMT-2000 requirements and are approved as 3G standards by ITU,these are typically not branded 3G,and are based on com

9、pletely different technologiesUNIT 19 3G Network 2.Introductions of TD-SCDMATD-SCDMA standard,developed by the China independently,has become one of the three mainstream 3G,and has an important position in China or even in international,TD-SCDMA uses TDD,smart antenna,joint detection,dynamic channel

10、 allocation,uplink synchronization,baton handover and other key technologies.All of these have TF-SCDMA system performance been greatly improved,the following will describe each of the key technology of TD-SCDMA.UNIT 19 3G Network Introductions to TDD3G system is divided into time division duplex(TD

11、D)and frequency division duplex(FDD)modes.FDD is used in WCDMA and CDMA2000,datas receiving and transmission occur in two symmetric,separated frequency channel.TDD is used in TD-SCDMA,which means the receiving and transmission occur in the same frequency.UNIT 19 3G Network Through periodic conversio

12、n direction,alternation uplink and downlink transmission in the same carrier,with a guaranteed time to separate the receiving and transmission channel.TD-SCDMA system is divided into the Core Network,Radio Access Network and User Equipment from the functions.The design combine with FDMA,TDMA,CDMA an

13、d SDMA as a whole,has high spectrum efficiency and low emission power.UNIT 19 3G Network The uplink and downlink can be asymmetric is also its advantage.TD-SCDMA maintain backward compatibility with GSM,which is the second generation mobile communication system cur widely used in China and the world

14、,allowing smooth transition from GSM to 3G systems.UNIT 19 3G Network Advantage of TDD:1)No symmetric band.It can use the asymmetric band flexibly which FDD cant use.It can adjust the number of up and down time slots to support asymmetric data sevices.2)Uplink and downlink has the same frequency,so

15、the propagation characteristics can be considered the same under certain conditions.Its beneficial using smart antennas and other new technologies.3)Equipment costs are generally lower than the FDD system.UNIT 19 3G Network 3.Advantages and disadvantages of TD-SCDMA Advantages 1)High spectrum effici

16、ency,TD-SCDMA uses TDD mode,applicate FDMA,CDMA,TDMA multiple access technologies synthetically,to facilitate set uplingk and downlink switch point in the transmission for different kinds of services,thus increasing spectrum efficiency.UNIT 19 3G Network 2)Support a variety of communication interfac

17、es:TD-SCDMA meet a variety of interference requirement s include lub,A,Gb,Iu,IuR.Base station subsystem can be both as a expansion of 2G,2.5G GSM and a base station subsystem of 3G.UNIT 19 3G Network 3)Spectrum flexibility:TD-SCDMA has a flexible frequency spectrum.Only a band of 1.6M can provide th

18、e service of 3G with 2M speed,which is very ideal for the transmission of asymmetric operations.4)System performance stable:TD-SCDMA is more suitable for the emerging smart antenna technology and joint detection technology.All of these technologies can reduce interference and increase the stability

19、of system.UNIT 19 3G Network 5)Compatibility with legacy systems:It adapt to a variety of UEs(User Equipment)of the environment,can implement a smooth transition from existing communications system to the next generation mobile communication system.UNIT 19 3G Network Disadvantage1)TD-SCDMA is fallin

20、g behind WCDMA and CDMA2000 in commercial progress,technological development and industrial scale.TD-SCDMA has a narrow bandwidth and can not take full advantage of multipath,which reduce the system efficiency.2)Ability in high-speed mobile environment is falling behind WCDMA and CDMA2000.3)TD-SCDMA

21、 system requires district keep synchronously,which need precise timing.So there is a high requirement on the timing system.UNIT 19 3G Network 19-1-3 Application Case or Example 1.Case 1:Application in stream media serviceWCDMA equipment supporting stream media business,which supports the standard RT

22、P/RTCP protocol,provides the high performance adaptive bandwidth and the industrys widely used MPEG-2/4 technologies,also applied to audio,video codec,and provide a wealth of operational interface,access to various types of media.UNIT 19 3G Network It can support unicast,multicast service and variet

23、y charging policy with stream media technology,providing a complete digital rights management.Figure 19-3 shows logical network diagram of stream media as below.UNIT 19 3G Network Figure 19-3 Logical network diagram of stream mediaUNIT 19 3G Network HTTP Accelerator:Web browsing is the most widely u

24、sed data service.Users expect to be able to quickly load web pages at any time or place.In traditional mobile telecommunication systems,however,multiple services coexist and equally compete for limited bandwidth resources.Bandwidth is not allocated preferentially to web page access,making it difficu

25、lt for users to enjoy high-quality,low-delay web browsing.During high-traffic hours,web access is frequently impacted by other services and users experience high levels of delay.UNIT 19 3G Network This feature relies on packet analysis to recognize web page accesses and then preferentially allocates

26、 higher bandwidth to these services,thus reducing access time and improving the user experience.This feature is only applicable for HSDPA users.UNIT 19 3G Network P2P Slow down:With the current rapid growth of high bandwidth mobile telecommunication systems,more and more users are using P2P to downl

27、oad content such as music and videos.Due to its high volume and long duration,P2P traffic consumes a large amount of system resources.This significantly increases operator costs and adversely affects the user experience of other time sensitive services.Therefore,to solve this problem,this feature is

28、 introduced.UNIT 19 3G Network The below Figure 19-4 shows the HTTP Accelerator and P2P Download Rate Restriction.This feature restricts P2P traffic during busy periods,reducing operator cost and improving the user experience of other time sensitive services.High-speed P2P downloads are not restrict

29、ed during idle periods,which allows P2P users to achieve good performance and helps users take advantage of network resources.UNIT 19 3G Network Figure 19-4 HTTP Accelerator and P2P Download Rate RestrictionUNIT 19 3G Network 19-2 Reading Material 19-2-1 Reading Comprehension Introduction to 3GThe I

30、nternational Telecommunications Union(ITU)defined the third generation(3G)of mobile telephony standards IMT-2000 to facilitate growth,increase bandwidth,and support more devices applications.For example,GSM(the current most popular cellular phone standard)could deliver not only voice,but also circui

31、t-switched data at download speeds up to14.4 kbps.But to support mobile multimedia applications,3G had to deliver packet-switched data with better spectral efficiency,at far greater speeds.UNIT 19 3G Network International Mobile Telecommunications-2000(IMT-2000),better as 3G or 3rd Generation,is a f

32、amily of standards for wireless communications defined by the International Telecommunications Union,which includes GSM EDGE,UMTS,and CDMA2000 as well as DECT and WiMAX.Services include wide-area wireless voice telephone,video calls,and wireless data,all in a mobile environment.Compared to 2G and 2.

33、5G services,3G allows simultaneous use of speech and data services and higher data rates(up to 14.4 Mbit/s on the downlink and 5.8 Mbit/s on the uplink with HSPA+).UNIT 19 3G Network Thus,3G networks enable network operators to offer users a wider range of more advanced services while achieving grea

34、ter network capacity through improved spectral efficiency.Both 3GPP and 3GPP2 are currently working on further extensions to 3G standards,named Long Term Evolution and Ultra Mobile Broadband,respectively.Being based on an all-IP network infrastructure and using advanced wireless technologies such as

35、 MIMO,UNIT 19 3G Network these specifications already display features characteristic for IMT-Advanced(4G),the successor of 3G.However,falling short of the speed requirements for 4G(which is 1 Gbit/s for stationary and 100 Mbit/s for mobile operation),these standards are classified as 3.9G or Pre-4G

36、.3GPP plans to meet th 4G goals with LTE Advanced,whereas Qualcomm has halted development of UMB in favour of the LTE family.UNIT 19 3G Network Words&ExpressionsInternational Telecommunications Union 国际电信联盟facility vt.使便利，减轻的困难GSM 全球移动通信系统，俗称全球通 EDGE 是一种基于GAM/GPRS网络的数据增强型移动通信技术，通常被称为“2.75代技术”UMTS 通用

37、移动通信技术CDMA2000 一种3G移动通信标准UNIT 19 3G Network DECT 先进数字式无线通信系统WiMAX 微波存取全球互通，是一项新型的宽带无线接入技术simultaneous adj.同时发生的，同时存在的 uplink 向上传输HSPA+是HSPA(3GPPR6)的向下演进版本，是上下行能力增强的技术UNIT 19 3G Network UMB 是CDMA2000系列标准的演进升级版本LTE 3GPP长期演进(LTE)项目，被看做准4G 标准infrastructure n.基础设施，基础结构MIMO 多输入多输出技术halt vt&vi.使停下来UNIT 19

38、3G Network 19-2-2 Exercises I.Multiple Choices.1.According to the passage,3G refers to _.A.3 gamesB.3 gradesC.3 generationsD.3nd generationsUNIT 19 3G Network 2.About 3G,which of the following is NOT TRUE?A.3G is better known as International Mobile Telecommunications-2000(IMT-2000).B.3G allows simu

39、ltaneous use of speech and data services and higher data rates.C.3G is a family of standards for wireless communications defined by the International Telecommunication Union.D.3G will have its successors.UNIT 19 3G Network 3.How many services are mentioned in a mobile environment?A.Two.B.Three.C.Fou

40、r.D.Five.4.Which of the following terms is not mentioned in the passage?A.2G.B.3G.C.3G.D.4G.UNIT 19 3G Network 5.What can be inferred from the passage about 4G?A.It is more popular than 3G.B.It will completely replace 3G in the near future.C.It is the most advantaged generation.D.It will be more adv

41、anced than 3G.UNIT 19 3G Network II.Read&Translate.1.The International Telecommunications Union(ITU)defined the third generation (3G)of mobile telephony standards IMT-2000 to facilitate growth,increase bandwidth,and support more devices applicationsUNIT 19 3G Network 2.Thus,3G networks enable networ

42、k operators to offer users a wider range of more advanced services while achieving greater network capacity through improved spectral efficiency.3.Being based on an all-IP network infrastructure and using advanced wireless technologies such as MIMO,these specifications already display features characteristic for IMT-Advanced(4G),the successor of 3G.