1、UNIT19 3G Network 19-1 Technical Part19-2 Reading Material 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 Telecommunications-2000(IMT-2000)sp
2、ecifications 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.19-1-2 Introductions Several telecommunications companies market have extended to wireless mobile Int
3、ernet 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).To meet the IMT-2000 standards,a system is required to pro
4、vide peak data rates of at least 200 kbit/s(about 0.2 Mbit/s).However,many services advertised as 3G provide higher speed than the minimum technical requirements for a 3G service.Recent 3G releases,often denoted 3.5G and 3.75G,also provide mobile broadband access of several Mbit/s to smartphones and
5、 mobile modems in laptop computers.1.Concept of UMTS The UMTS(Universal Mobile Telecommunications System)first offered in 2001,standardized by 3GPP,used primarily in Europe,Japan,China(however with a different radio interface)and other regions predominated by GSM 2G system infrastructure.The cell ph
6、ones are typically UMTS and GSM hybrids.Several radio interfaces are offered,sharing the same infrastructure:The latest UMTS release,HSPA+,can provide peak data rates up to 56 Mbit/s in the downlink in theory(28 Mbit/s in existing services)and 22 Mbit/s in the uplink.The following standards are typi
7、cally branded 3G: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 admitted to the UTRA TDD
8、 standard by 3GPP in 1999.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.Figure 19-1 The network architecture of WCDMA telecommunicati
9、ons industry 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-95 hybrids.The latest release EVDO Rev B offers peak rates of 14.7 Mbit/s down
10、stream.The Figure 19-2 shows the deployment of CDMA2000 1X EVDO.Figure 19-2 Network deployment of CDMA 2000 1X EVDO The above systems and radio interfaces are based on spread spectrum radio transmission technology.While the GSM EDGE standard(“2.9G”),DECT(Digital Enhanced Cordless Telecommunication)c
11、ordless 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 completely different technologies2.Introductions of TD-SCDMATD-SCDMA standard,developed by the China independently,has
12、 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 allocation,uplink synchronization,baton handover and other key technologies.All of these have TF-SCDMA system performance been greatl
13、y improved,the following will describe each of the key technology of TD-SCDMA.Introductions to TDD3G system is divided into time division duplex(TDD)and frequency division duplex(FDD)modes.FDD is used in WCDMA and CDMA2000,datas receiving and transmission occur in two symmetric,separated frequency c
14、hannel.TDD is used in TD-SCDMA,which means the receiving and transmission occur in the same frequency.Through periodic conversion 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 di
15、vided into the Core Network,Radio Access Network and User Equipment from the functions.The design combine with FDMA,TDMA,CDMA and SDMA as a whole,has high spectrum efficiency and low emission power.The uplink and downlink can be asymmetric is also its advantage.TD-SCDMA maintain backward compatibili
16、ty with GSM,which is the second generation mobile communication system cur widely used in China and the world,allowing smooth transition from GSM to 3G systems.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
17、 slots to support asymmetric data sevices.2)Uplink and downlink has the same frequency,so 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.3.Adv
18、antages and disadvantages of TD-SCDMA Advantages 1)High spectrum efficiency,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 effi
19、ciency.2)Support a variety of communication interfaces: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.3)Spectrum flexibility:TD-SCDMA has a flexible frequency spectrum.O
20、nly a band of 1.6M can provide the 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 interfe
21、rence and increase the stability of system.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.Disadvantage1)TD-SCDMA is falling beh
22、ind 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 syst
23、em requires district keep synchronously,which need precise timing.So there is a high requirement on the timing system.19-1-3 Application Case or Example 1.Case 1:Application in stream media serviceWCDMA equipment supporting stream media business,which supports the standard RTP/RTCP protocol,provides
24、 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.It can support unicast,multicast service and variety charging policy with stream media technol
25、ogy,providing a complete digital rights management.Figure 19-3 shows logical network diagram of stream media as below.Figure 19-3 Logical network diagram of stream media HTTP Accelerator:Web browsing is the most widely used data service.Users expect to be able to quickly load web pages at any time o
26、r 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 difficult for users to enjoy high-quality,low-delay web browsing.During high-traffic ho
27、urs,web access is frequently impacted by other services and users experience high levels of delay.This feature relies on packet analysis to recognize web page accesses and then preferentially allocates higher bandwidth to these services,thus reducing access time and improving the user experience.Thi
28、s feature is only applicable for HSDPA users.P2P Slow down:With the current rapid growth of high bandwidth mobile telecommunication systems,more and more users are using P2P to download content such as music and videos.Due to its high volume and long duration,P2P traffic consumes a large amount of s
29、ystem 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 introduced.The below Figure 19-4 shows the HTTP Accelerator and P2P Download Rate Restriction.This feature restricts
30、P2P traffic during busy periods,reducing operator cost and improving the user experience of other time sensitive services.High-speed P2P downloads are not restricted during idle periods,which allows P2P users to achieve good performance and helps users take advantage of network resources.Figure 19-4
31、 HTTP Accelerator and P2P Download Rate Restriction 19-2 Reading Material 19-2-1 Reading Comprehension Introduction to 3GThe International Telecommunications Union(ITU)defined the third generation(3G)of mobile telephony standards IMT-2000 to facilitate growth,increase bandwidth,and support more devi
32、ces applications.For example,GSM(the current most popular cellular phone standard)could deliver not only voice,but also circuit-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
33、greater speeds.International Mobile Telecommunications-2000(IMT-2000),better as 3G or 3rd Generation,is a family 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-ar
34、ea wireless voice telephone,video calls,and wireless data,all in a mobile environment.Compared to 2G and 2.5G 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+).Thus,3G networks enable netwo
35、rk operators to offer users a wider range of more advanced services while achieving greater 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 ba
36、sed 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.However,falling short of the speed requirements for 4G(which is 1 Gbit/s for stationary and 100 Mbit/s f
37、or mobile operation),these standards are classified as 3.9G or Pre-4G.3GPP plans to meet th 4G goals with LTE Advanced,whereas Qualcomm has halted development of UMB in favour of the LTE family.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
38、 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 通用移动通信技术CDMA2000 一种3G移动通信标准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.
39、使停下来19-2-2 Exercises I.Multiple Choices.1.According to the passage,3G refers to _.A.3 gamesB.3 gradesC.3 generationsD.3nd generations2.About 3G,which of the following is NOT TRUE?A.3G is better known as International Mobile Telecommunications-2000(IMT-2000).B.3G allows simultaneous use of speech and
40、 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.3.How many services are mentioned in a mobile environment?A.Two.B.Three.C.Four.D.Five.4.Which of the following terms is no
41、t mentioned in the passage?A.2G.B.3G.C.3G.D.4G.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 advanced than 3G.II.Read&Translate.1.The International Telecommunic
42、ations Union(ITU)defined the third generation (3G)of mobile telephony standards IMT-2000 to facilitate growth,increase bandwidth,and support more devices applications2.Thus,3G networks enable network 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.
