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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 Telecommunications 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 truly 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 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 is 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 transmission 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 CDMA2000) 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 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 significant 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 uplink 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 to 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 spectrum., 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. The 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 direct 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 the 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 result, 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 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 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 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 comprehensive 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 included 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 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 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 Europe (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 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), 3GPP 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, 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 interface); 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 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 areas 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 introduce 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 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 Designed 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). 作为一种以同步模式运行的结合CDMA自适应技术的高级TDMA/TDD系统, TD-SCDMA 具有对称电路交换服务业务(如语音和视频)和非对称分组交换服务业务(如手机上网)。 Designed as是一个状语从句修饰主语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 without installation of completely new infrastructure. TD-SCDMA的主要优势在于它的运营费用比其他3G系统低, 因为它的频谱利用率较高而且与GSM网络组件兼容, 使得3G业务在GSM系统中能够实现而不需要安装新的基础设施。 That 引导一个表语从句作宾语, since引导原因状语从句, allowing引导结果状语从句。,3 On the contrary, TD-SCDMA adapts the uplink/downlink ratio according to the data load within a single unpaired frequency thus utilizing the spectrum more efficiently, and provides data rates ranging from 1.2 kbps to 2Mbps. 相反, TD-SCDMA根据数据负荷在单一而非成对的载频内调整上下行的(时隙)比率， 因此能够更有效地利用频谱, 并提供从1.2 kbps到2 Mbps的数据传输速率。,4 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 uplink and downlink traffic (TDD unpaired band) instead of two separate bands for uplink and downlink (FDD paired bands). 如前所述, 在非对称通信量应用中, TD-SCDMA利用可用频谱的效率比其他3G标准高, 因为它在只利用一个频带(TDD单一频带)而不是两个独立的频带(FDD成对频带)进行上行及下行通信。,5 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. 智能天线的高方向性和灵敏度连同终端只有在激活的时间内才发射功率这一事实有助于保持终端的低功耗, 这带来更多具有成本效益的手持设备。 That引导一个同位语从句修饰fact, 谓语为contributes to, which引导一个非限制性定语从句, 引出前面的结果。,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 awarded. TD-SCDMA的两种部署TSM和TDDCLR的数据速率、 频谱利用率、 覆盖率、 移动性和可靠性等性能是一样的, 并基本上为所有取得非成对TDD频段牌照的运营商所采用。 having作为定语修饰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 Division 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) (12) 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 section 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 are 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 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. 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 hierarchical 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 Bandwidth 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 network 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 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 unpaired 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 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 coverage 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 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 and 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-random bits (called chips) derived from CDMA spreading codes. WCDMA是一个宽带直扩码分多址(DS-CDMA)系统, 即通过用户数据与由CDMA扩频码得来的伪随机比特(称为码片)相乘, 从而把用户信息比特扩展到宽的带宽之上。 ,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 increase of coverage and capacity on the uplink. 虽然IS-95在下行链路中使用了相干检测, 但是在公众CDMA系统中上行链路使用相干检测是一种新技术, 这将全面增加上行链路的覆盖和容量。 while引导一从句省略主句主语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 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进的CDMA接收机理念, 例如多用户检测和自适应智能天线, 运营商可以将这些先进技术作为提高系统容量和/或覆盖的选择方案。 that引导一个同位语从句解释way, such as是插入语。,4 In most second 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. 在大多数第二代系统中, 并没有提出这些先进的接收机理念。 因此, 它们或者根本不可能应用, 或者就只能在一些苛刻的条件约束下才能应用, 而且在性能方面的提高很有限。,Exercises 1. Please translate the following phrases into Chinese. (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) What 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 explosive 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 inexorable 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 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 (as 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 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
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