電子信息類專業(yè)英語（西電第二版）Unit163rdGenerationMobile

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1、Unit 16 3rd Generation Mobile Communications,Passage A TDSCDMA-a 3G Radio Access Technology Passage B Summary of the Main Parameters in WCDMA Passage C Planning Ahead: Technology Choices in a Complex World,1. What is TD-SCDMA? Jointly developed by Siemens and the China Academy of Telecommunica

2、tions Technology (CATT), TD-SCDMA (Time Division Synchronous Code Division Multiple Access) is one of the five IMT-2000 standards accepted by the ITU. In March 2001 the standard was also adopted by the Third Generation Partnering Project (3GPP), as part of UMTS Release 4. In this way it became a tru

3、ly global standard, which covers all radio deployment scenarios: from rural to dense urban areas, from pedestrian to high mobility.,Passage A TD-SCDMA-a 3G Radio Access Technology,Designed as an advanced TDMA/TDD system with an adaptive CDMA component operating in synchronous mode, TD-SCDMA masters

4、both symmetric circuit switched services (such as speech or video) as well as asymmetric packet switched services (such as mobile Internet access).1 The main benefits of TD-SCDMA are that it can be implemented less expensively than comparable 3G systems since it is much more spectrum efficient and i

5、s compatible with GSM network elements, allowing 3G services without installation of completely new infrastructure.2 The key benefits are: , Services optimally suited for asymmetric 3G applications (mobile Internet). Real-time applications like voice and multimedia require minimum delay during trans

6、mission and generate symmetric traffic. For non real-time applications like e-mail or Internet access, timing constraints are less strict and the generated traffic is asymmetric. For all those radio technologies which require separate bands for uplink and downlink (such as GSM, EDGE, W-CDMA or CDMA2

7、000) portions of the spectrum are occupied but not used when an asymmetric data load is applied. These idle resources cannot be utilized for any other service, leading to an inefficient use of the spectrum. On the contrary, TD-SCDMA,adapts the uplink/downlink ratio according to the data load within

8、a single unpaired frequency thus utilizing the spectrum more efficiently, and provides data rates ranging from 1.2 kbps to 2 Mbps.3 This is especially helpful in an environment with increasing data traffic (mobile data), which tends to be asymmetric, often requiring little uplink throughput, but sig

9、nificant bandwidth for downloading information (mobile Internet)., Outstanding Spectrum Efficiency increases capacity. As already stated, with asymmetric traffic applications, TD-SCDMA utilizes the available spectrum more efficiently than other 3G standards since it employs only one band for both up

10、link and downlink traffic (TDD unpaired band) instead of two separate bands for uplink and downlink (FDD paired bands).4 Moreover, highly effective technologies like smart antennas, joint detection and dynamic channel allocation-which are integral features of the TD-SCDMA radio standard-contribute t

11、o minimize intra-cell interference (typical of every CDMA technology) and inter-cell interference leading to an outstanding spectrum efficiency (3-5 times GSM). This is especially helpful in densely populated urban areas, which are capacity driven and require an efficient use of the available spectr

12、um., Smooth migration to 3G. TD-SCDMA allows an easy migration path: GSM/GPRS/TDSCDMA. 3G services are introduced adding TD-SCDMA radio subsystems to existing stable and established GSM infrastructures. The total migration costs from 2G to 3G decrease considerably, compared to other 3G standards. Th

13、e total investment risk is reduced and at the same time investment in already purchased GSM infrastructure is secured., Increased flexibility. TD-SCDMAs carrier bandwidth of 1.6 MHz provides high flexibility in spectrum usage and network design. Low power emission. Beam Steering Smart Antennas direc

14、t power to active mobile terminals only. The high directivity and sensibility of smart antenna together with the fact that terminals transmit power only during active timeslots contributes to keep the terminals power consumption low, which leads to more cost effective handsets. 5In addition, since t

15、he transmitted power is directed only to active users, the radio illuminated area is strongly reduced., Reduced Investment Costs. In conventional 2G and 3G CDMA based systems, due to intra-cell interference cell area is reduced when data rates or numbers of user grow (cell breathing effect). As a re

16、sult, when traffic increases, an operator has to introduce a higher number of base stations in order to guarantee an adequate coverage. On the contrary, in TD-SCDMA systems the traffic load can be increased without reducing coverage: the cell-breathing effect is not an issue anymore. This leads to a

17、 considerable reduction of infrastructure costs., Costs of Leased Lines reduced. Thanks to joint detection, smart antennas and an accurate terminal synchronization TD-SCDMA does not need to rely on soft handover. On the contrary, TD-SCDMA uses conventional handover (similarly to GSM) which leads to

18、a sensible reduction of the cost of leased lines compared with other 3G standards. Simple Network planning. Network Planning is sensibly simplified since TD-SCDMA is not affected by cell breathing and soft handovers. TD-SCDMA enjoys considerable backing in China. Field Trials started in October 2001

19、 in Beijing and the first commercial networks will be deployed in China in 2003.,2. TD-SCDMA is an Universal Standard for 3G The international 3G standards are accepted by the ITU (International Telecommunication Union) under the name of International Mobile Telecommunication-2000 (IMT-2000). A comp

20、rehensive set of terrestrial radio interface specifications for IMT-2000 was approved in November 1999. These included (Figure 16.1): IMT-DS (Direct Spread)-W-CDMA; MT-MC (Multi Carrier)-CDMA2000;, IMT-SC (Single Carrier)-UWC; IMT-FT (Frequency Time)-DECT; IMT-TD (Time Division)-CDMA TDD, it includ

21、ed TD-CDMA (Time Division-Code Division Multiple Access) and TD-SCDMA (Time Division- Synchronous Code Division Multiple Access). Being acknowledged as one mode of the interface IMT-TD, TD-SCDMA air interface became in this way an international standard in 1999.,Figure 16.1 IMT-2000 Radio Interface

22、Standard,In Europe, the 3G standard has been initially developed by ETSI (European Telecommunication Standard Institute) under the designation of UMTS (Universal Mobile Telecommunications System). The radio access interface of the UMTS (UTRA) comprises two standards for operation in the FDD and TDD

23、modes. Both interfaces have been accepted by ITU and are designated IMT-DS and IMTTD respectively. The UMTS standard is being currently defined by Third Generation Partnership Project (3GPP): a joint venture of industry organizations and of several Standards Developing Organizations (SDOs) from Euro

24、pe (ETSI), US (T1), Japan (ARIB), Korea (TTA), and China (CWTS).,3GPP is introducing UMTS in phases and annual releases. The first release (Rel99), issued in December 1999, and defined the following two standards: UTRA FDD and UTRA TDD. These two standards were complementary: UTRA-FDD to be employed

25、 in Micro and Macro Cells, UTRA TDD to cover micro, pico cells and indoor. In order to offer seamless services everywhere and every time, the two modes of the UTRA standard should be deployed together in a common network.,In the second release of the UTRA standard (called Release 4, March 2001), 3GP

26、P agreed upon the worldwide harmonization and extension of the TDD performance spectrum. Additional features of TD-SCDMA radio technology were also included in the specification for this UMTS Standard (Figure 16.2).,Figure 16.2 TD-SCDMA Air Interface is Part of UMTS Release 4,According to Release 4,

27、 TD-SCDMA radio interface is integrated in 3GPP as the 1.28 Mcps option of the UTRA TDD, also called TDDLCR (TDD Low Chip Rate). The current status of the UMTS terrestrial radio access standard includes the following modes: UTRA FDD (W-CDMA); UTRA TDDHCR (3.84 Mcps, 5 MHz bandwidth, TD-CDMA air inte

28、rface); UTRA TDDLCR (1.28 Mcps, 1.6 MHz bandwidth, TD-SCDMA air interface).,UTRA-FDD targets public areas where high mobility in micro and macro cells together with symmetric services is required. Based on the classic DS-CDMA principle this technology uses paired frequency bands with a radio carrier

29、 bandwidth of 5 MHz. UTRA TDDHCR is best suited for low mobility micro/pico public areas outdoor and indoor. UTRA TDDLCR (TD-SCDMA), on the contrary, covers all application scenarios. This technology is designed to address all sizes of deployment environments-from rural to densely populated urban ar

30、eas and indoor applications, from stationary to high mobility. Figure 16.3 offers a complete Solution-Macro, micro and pico coverage, pedestrian and high mobility.,Figure 16.3 A Complete Solution,TDDLCR uses the UTRA core network and the TD-SCDMA air interface. It is also possible, however, to intro

31、duce a TD-SCDMA Radio Access Channel while using the GSM core network, including the signaling and protocols (Figure 16.4). This TD-SCDMA deployment, called TSM (TD-SCDMA System for Mobile Communication), offers a smooth and seamless way of introducing 3G mobile networks and services while keeping a

32、 GSM infrastructure. Both TD-SCDMA deployments-TSM and TDDLCR-offer the same performances in terms of data rate, spectrum efficiency, coverage, mobility and reliability and basically can be introduced by all operators having TDD unpaired bands awarded.6,Figure 16.4 TD-SCDMA Protocols,Notes 1 Designe

33、d as an advanced TDMA/TDD system with an adaptive CDMA component operating in synchronous mode, TD-SCDMA masters both symmetric circuits switched services (such as speech or video) as well as asymmetric packet switched services (such as mobile Internet access). 作為一種以同步模式運行的結(jié)合CDMA自適應(yīng)技術(shù)的高級TDMA/TDD系統(tǒng),

34、TD-SCDMA 具有對稱電路交換服務(wù)業(yè)務(wù)(如語音和視頻)和非對稱分組交換服務(wù)業(yè)務(wù)(如手機上網(wǎng))。 Designed as是一個狀語從句修飾主語TD-SCDMA。,2 The main benefits of TD-SCDMA are that it can be implemented less expensively than comparable 3G systems since it is much more spectrum efficient and is compatible with GSM network elements, allowing 3G services with

35、out installation of completely new infrastructure. TD-SCDMA的主要優(yōu)勢在于它的運營費用比其他3G系統(tǒng)低, 因為它的頻譜利用率較高而且與GSM網(wǎng)絡(luò)組件兼容, 使得3G業(yè)務(wù)在GSM系統(tǒng)中能夠?qū)崿F(xiàn)而不需要安裝新的基礎(chǔ)設(shè)施。 That 引導(dǎo)一個表語從句作賓語, since引導(dǎo)原因狀語從句, allowing引導(dǎo)結(jié)果狀語從句。,3 On the contrary, TD-SCDMA adapts the uplink/downlink ratio according to the data load within a single unpaire

36、d frequency thus utilizing the spectrum more efficiently, and provides data rates ranging from 1.2 kbps to 2Mbps. 相反, TD-SCDMA根據(jù)數(shù)據(jù)負(fù)荷在單一而非成對的載頻內(nèi)調(diào)整上下行的(時隙)比率， 因此能夠更有效地利用頻譜, 并提供從1.2 kbps到2 Mbps的數(shù)據(jù)傳輸速率。,4 As already stated, with asymmetric traffic applications, TD-SCDMA utilizes the available spectrum m

37、ore efficiently than other 3G standards since it employs only one band for both uplink and downlink traffic (TDD unpaired band) instead of two separate bands for uplink and downlink (FDD paired bands). 如前所述, 在非對稱通信量應(yīng)用中, TD-SCDMA利用可用頻譜的效率比其他3G標(biāo)準(zhǔn)高, 因為它在只利用一個頻帶(TDD單一頻帶)而不是兩個獨立的頻帶(FDD成對頻帶)進(jìn)行上行及下行通信。,5 T

38、he high directivity and sensibility of smart antenna together with the fact that terminals transmit power only during active timeslots contributes to keep the terminals power consumption low, which leads to more cost effective handsets. 智能天線的高方向性和靈敏度連同終端只有在激活的時間內(nèi)才發(fā)射功率這一事實有助于保持終端的低功耗, 這帶來更多具有成本效益的手持設(shè)

39、備。 That引導(dǎo)一個同位語從句修飾fact, 謂語為contributes to, which引導(dǎo)一個非限制性定語從句, 引出前面的結(jié)果。,6 Both TD-SCDMA deployments-TSM and TDDLCR-offer the same performances in terms of data rate, spectrum efficiency, coverage, mobility and reliability and basically can be introduced by all operators having TDD unpaired bands awar

40、ded. TD-SCDMA的兩種部署TSM和TDDCLR的數(shù)據(jù)速率、 頻譜利用率、 覆蓋率、 移動性和可靠性等性能是一樣的, 并基本上為所有取得非成對TDD頻段牌照的運營商所采用。 having作為定語修飾operators。,Exercises 1. Please translate the following phrases into Chinese. (1) circuit switch (2) packet switch (3) CATT (China Academy of Telecommunications Technology) (4) TD-SCDMA (Time Divisi

41、on Synchronous Code Division Multiple Access) (5) ITU (International Telecommunication Union) (6) 3GPP (the Third Generation Partnership Project),(7) Beam Steering Smart Antenna (8) Cell Breathing Effect (9) Base Station (10) Soft Handover (11) ETSI (European Telecommunication Standard Institute) (1

42、2) UMTS (Universal Mobile Telecommunication System),2. Answer the questions. (1) What is TD-SCDMA? (2) What are the main benefits? (3) What is the data rates TD-SCDMA can provide? ,,Passage B Summary of the Main Parameters in WCDMA We present the main system design parameters of WCDMA in this sectio

43、n and give brief explanations for most of them. Table 16.1 summarizes the main parameters related to the WCDMA air interface. Here we highlight some of the items that characterize WCDMA., WCDMA is a wideband Direct-Sequence Code Division Multiple Access (DS-CDMA) system, i.e. user information bits a

44、re spread over a wide bandwidth by multiplying the user data with quasi-random bits (called chips) derived from CDMA spreading codes.1 In order to support very high bit rates (up to 2 Mbps), the use of a variable spreading factor and multicode connections is supported. An example of this arrangement

45、 is shown in Figure 16.5.,Figure 16.5 Allocation of bandwidth in WCDMA in the Time-frequency-code space, The chip rate of 16.84 Mcps leads to a carrier bandwidth of approximately 5 MHz. DSCDMA systems with a bandwidth of about 1 MHz, such as IS-95, are commonly referred to as narrowband CDMA systems

46、. The inherently wide carrier bandwidth of WCDMA supports high user data rates and also has certain performance benefits, such as increased multipath diversity. Subject to his operating license, the network operator can deploy multiple 5 MHz carriers to increase capacity, possibly in the form of hie

47、rarchical cell layers. Figure 16.1 also shows this feature. The actual carrier spacing can be selected on a 200 kHz grid between approximately 4.4 and 5 MHz, depending on interference between the carriers., WCDMA supports highly variable user data rates, in other words the concept of obtaining Bandw

48、idth on Demand (BoD) is well supported. The user data rate is kept constant during each 10 ms frame. However, the data capacity among the users can change from frame to frame. Figure 16.1 also shows an example of this feature. This fast radio capacity allocation will typically be controlled by the n

49、etwork to achieve optimum throughput for packet data services., WCDMA supports two basic modes of operation: Frequency Division Duplex (FDD) and Time Division Duplex (TDD). In the FDD mode, separate 5 MHz carrier frequencies are used for the uplink and downlink respectively, whereas in TDD only one

50、5 MHz is timeshared between the uplink and downlink. Uplink is the connection from the mobile to the base station, and downlink is that from the base station to the mobile. The TDD mode is based heavily on FDD mode concepts and was added in order to leverage the basic WCDMA system also for the unpai

51、red spectrum allocations of the ITU for the IMT-2000 systems. , WCDMA supports the operation of asynchronous base stations, so that, unlike in the synchronous IS-95 system, there is no need for a global time reference such as a GPS. Deployment of indoor and micro base stations is easier when no GPS

52、signal needs to be received. WCDMA employs coherent detection on uplink and downlink based on the use of pilot symbols or common pilot. While already used on the downlink in IS-95, the use of coherent detection on the uplink is new for public CDMA systems and will result in an overall increase of co

53、verage and capacity on the uplink.2, The WCDMA air interface has been crafted in such a way that advanced CDMA receiver concepts, such as multiuser detection and smart adaptive antennas, can be deployed by the network operator as a system option to increase capacity and/or coverage.3 In most second

54、generation systems no provision has been made for such receiver concepts and as a result they are either not applicable or can be applied only under severe constraints with limited increases in performance.4 WCDMA is designed to be deployed in conjunction with GSM. Therefore, handovers between GSM a

55、nd WCDMA are supported in order to be able to leverage the GSM coverage for the introduction of WCDMA.,Notes 1 WCDMA is a wideband Direct-Sequence Code Division Multiple Access (DS-CDMA) system, i.e. user information bits are spread over a wide bandwidth by multiplying the user data with quasi-rando

56、m bits (called chips) derived from CDMA spreading codes. WCDMA是一個寬帶直擴(kuò)碼分多址(DS-CDMA)系統(tǒng), 即通過用戶數(shù)據(jù)與由CDMA擴(kuò)頻碼得來的偽隨機比特(稱為碼片)相乘, 從而把用戶信息比特擴(kuò)展到寬的帶寬之上。 ,2 While already used on the downlink in IS-95, the use of coherent detection on the uplink is new for public CDMA systems and will result in an overall increas

57、e of coverage and capacity on the uplink. 雖然IS-95在下行鏈路中使用了相干檢測, 但是在公眾CDMA系統(tǒng)中上行鏈路使用相干檢測是一種新技術(shù), 這將全面增加上行鏈路的覆蓋和容量。 while引導(dǎo)一從句省略主句主語the use of coherent detection on the uplink。,3 The WCDMA air interface has been crafted in such a way that advanced CDMA receiver concepts, such as multiuser detection and

58、 smart adaptive antennas, can be deployed by the network operator as a system option to increase capacity and/or coverage. WCDMA空中接口中包括一些先進(jìn)的CDMA接收機理念, 例如多用戶檢測和自適應(yīng)智能天線, 運營商可以將這些先進(jìn)技術(shù)作為提高系統(tǒng)容量和/或覆蓋的選擇方案。 that引導(dǎo)一個同位語從句解釋way, such as是插入語。,4 In most second generation systems no provision has been made for

59、 such receiver concepts and as a result they are either not applicable or can be applied only under severe constraints with limited increases in performance. 在大多數(shù)第二代系統(tǒng)中, 并沒有提出這些先進(jìn)的接收機理念。 因此, 它們或者根本不可能應(yīng)用, 或者就只能在一些苛刻的條件約束下才能應(yīng)用, 而且在性能方面的提高很有限。,Exercises 1. Please translate the following phrases into Ch

60、inese. (1) FDD (frequency division duplex) (2) TDD (time division duplex) (3) multiuser detection (4) quasi-random bit (5) coherent detection (6) pilot symbols (7) multipath diversity (8) carrier spacing (9) bandwidth of demand (BoD) ,2. Answer the questions. (1) What is uplink and downlink? (2) Wha

61、t is the difference of the carrier frequencies of uplink and downlink between TDD and FDD? (3) What is the soft handover and the hard handover? What is the difference between them?,,Passage C Planning Ahead: Technology Choices in a Complex World Dimensioning for the future The past decade has seen e

62、xplosive growth in mobile communications within every single continent across the globe. Spearheaded by GSM systems, the mobile communications sector in many countries is now experiencing subscriber penetration levels approaching or even exceeding 100%. Voice traffic continues its apparently inexora

63、ble migration from fixed to mobile networks. Multimedia services are starting to take hold as 3G/UMTS networks are rolled out-attracting subscribers at a faster rate than the first GSM networks-and appealing terminal devices become widely available.,In just a decade, mobile communications has had a

64、massive impact on economies and societies. That impact is continuing as the previously voice-centric mobile networks embrace data and video services and as convergence irreversibly changes the structure of the telecommunications industry. The amalgamation of mobile communications and the Internet (a

65、s shown in Figure 16.6) is set to strengthen as broadband access networks are deployed and legacy PSTNs are replaced by all-IP environments.,Figure 16.6 Evolution to Higher Bit Rates Drives Convergence Between Fixed/mobile Systems and the Internet,These new dimensions make planning for the future an

66、 urgent but daunting task. The underlying problem is unpredictability-the future can no longer be approached as an extrapolation of the past. No-one can be certain what mix of products and services the next generation of users will be demanding from the information and communications industries a decade from now.,Voice services will undoubtedly be part of that demand. When digital cellular systems were originally designed, voice was the primary target service. System design focused on technology