1、大连民族学院毕业设计外文资料翻译所 在 学 院：信息与通信工程学院专 业 (班级)： 电子 101 学 生 姓 名： 吴挺智 指 导 教 师： 于少华 徐道明 2014 年 2 月 9 日 1现代移动通信在日益增长的移动业务市场需求的推动下，3G 技术正在逐步走向应用。从目前 3G网络商用情况看，用户市场与运营商对 3G 的期望与网络实际应用之间存在一定的差距。在 3G 初期，众多的移动通信领域专家与学者们都预期 3G 将成为一个彻底实现普遍灵活、多样化、个性化的5A（Anyone，Anywhere，Anytime，Anydevice，Anything）方式的无缝隙宽带接入的解决方案，在网络统
2、一性、业务综合性、服务多样性方面，3G 将成为用户的理想选择。但是，随着规范制定、产品实现、网络商用、业务提供等多方面的发展，可以看出，现有的 WCDMA，cdma2000，TD-SCDMA 三类技术在应用方面都面临困境。认清这些问题，对于在移动通信产业发展中占据重要位置的移动运营商而言，具有重要的战略意义。从移动运营商角度来看，网络技术包括产品实现技术与网络运营技术。实现技术的综合性能影响网络运营技术，而网络运营技术又能够推动产品实现技术。这里结合对 3G 网络技术体系的理解，就应用方面面临的问题给予剖析。 对于 3G 产品实现技术而言，面临的最大问题就是如何实现产品性能多方面“软性”特征的
3、平衡与稳定。3G 系统中采用的 CDMA 无线接入技术的复杂程度远远超过 2G 系统的 GSM 技术。CDMA 技术以统计复用方式进行无线资源利用，用户区分采用码字方式，用户在时间、频谱方面呈共用特征，为了降低这种“共用”造成的“自干扰性”实现用户侧的高质量话音与数据业务，3G 网络需要在物理层、链路层、网络层引入多项关键无线技术，包括功率控制、软切换、多用户检测、智能天线、无线资源管理等，而对于每一项关键技术，不仅向下包含多类实现方式，而且横向与其它技术之间相关联。功率控制是克服 CDMA系统中的“远近效应”采用的一项关键技术，以实现用户之间的功率平衡，同时保证系统覆盖与容量之间的平衡。与
4、GSM 相比，3G 系统对功率控制的依赖程度很大，并且功率控制的精度与速度直接影响到网络性能。在功率控制的实现过程中，基站与手机的响应速度门限及可变性特征是限制功率控制速度的客观因素，用户的移动性与无线环境的复杂性是限制功率控制精度的客观因素。由于这两方面的客观因素存在，功率控制在 3G 的技术规范中不能给出明确限定值。因此，功率控制技术在实现及应用方面呈限制性与不确定性，这些特征一方面直接映射到 3G 网络性能中，另一方面通过与其2它技术（例如软切换）的相关性间接体现到 3G 网络性能中，这两方面将导致了网络性能的“软特性”。在当今高度信息化的社会，信息和通信已成为现代社会的“命脉”。信息的
5、交流主要依赖于计算机通信，而通信作为传输手段，与传感技术、计算机技术相互融合，已成为 21 世纪国际社会和世界经济发展的强大动力。为了适应时代的要求，新的一代移动通信技术应时而生，新的一代移动通信技术即人们称之第三代的核心特征是宽带寻址接入到固定网和众多不同通信系统间的无隙缝漫游，获取多媒体通信业务。随着时代的进步、科技的创新、人们的生活要求的提高，移动通信技术更新换代速度相当惊人，差不多每隔十年移动通信技术就发生一次变革性换代，从上个世纪 80年代的“大哥大”到现在的 3G 手机，其间发生了两次移动通信技术的变革，从 1G 的AMPS 过渡到 2G 的 GSM，从 GSM 到 IMT-200
6、0（即 3G 技术）。就我所知现代的移动通信技术有以下几方面的重要技术：1.宽带调制和多址技术无线高速数据传输不能一味仅靠频谱的扩展，应在频谱效率上至少高于目前一个数量级，可在物理层采用三项技术，即 OFDM、UWB 和空时调制编码。OFDM 与其他编码方式的结合，灵活把 OFDM 与 TDMA、FDMA、CDMA、SDMA 组合成多址技术。20 世纪 60 年代 OFDM 的多路数据传输已成功用于 Kineplex 和 Kathryn 高频军事通信系统。OFDM 已用于 1.6 Mbit/s 高比特率数字用户线（HDSL），6 Mbit/s 不对称数字用户线（ADSL），100 Mbit/s
7、 甚高速数字用户线（VDSL），数字音频广播和数字视频广播等。OFDM 应用于 5 GHz 上提供 54 Mbit/s 无线本地网 IEEE 802.11 a 和 IEEE 802.11g，高性能本地域网络 Hiper LAN/2 和 ETSI-BRAN，还作为城域网 IEEE 802.16和集成业务数字广播（ISDB-T）标准。与单载频调制制式相比，OFDM 调制制式要解决相对大的峰均功率比（PAPR，Peak to Average Power Ratio）和对频率位移和相位噪声敏感的问题。高速移动通信的另一要求是在宽噪声带宽下，所需解调信噪比应尽可能降低，从而增加覆盖面积。可采取抗衰落的快
8、速发射功率控制和导频辅助快速跟踪相干解调技术，如频域抗衰落的 Rake 接收和跟踪技术，从时域和频域抵抗时间和频率选择性衰落的 OFDMA 技术，链路自适应技术，联合编码技术。2.频谱利用率提升技术理论研究指出：在独立 Rayleigh 散射信道中，数据速率与天线数成线性关系，容3量可达 Shannon 的 90%。在发射和接收端以多天线开发信道空间可取得容量和频谱效率的增益。MIMO 技术主要包括空间复用和空间分集技术，在独立信道上并发或连发相同信息来提高传输可靠性。收发双方的空间分集是高容量无线通信系统采用技术之一。贝尔实验室分层次空时的对角 BLAST（D-BLAST）容量的增加为收发双
9、方最小天线数的函数。利用 MIMO 所构成的跨时域和空域的扩展信号还可以抵抗多径干扰。V-BLAST 系统在室内 2434 dB 时，频谱利用率为 2040 bit/s/Hz。而发射和接收端均采用 16 天线，在 30 dB 时，频谱利用率增至 6070 bit/s/Hz。智能天线自动跟踪所需信号和自适应空时处理算法，利用天线阵产生空间定向波束，通过数字信号处理技术使主波束对准用户信号到达方向，旁瓣或零陷对准干扰信号到达方向。自适应阵列天线（AAA，Adaptive Array Antennas）中干扰抵消均衡器（ICE，Interference Canceling Equalizer）可减少
10、干扰和降低发射功率。3.软件无线电技术软件无线电技术是在硬件平台上通过软件编辑以一个终端实施不同系统中多种通信业务。它用数字信号处理语言描述电信元件，以软件程序下载成数字信号处理硬件（DSPH，Digital Signal Pocessing Hardware）。以具有通用开放无线结构（OWA，Open Wireless Architecture），兼容多种模式在多种技术标准之间无缝切换。UWB 也称为脉冲无线电，调制采用脉冲宽度在纳秒级的快速上升和下降脉冲，脉冲覆盖的频谱从直流至吉赫兹，不需常规窄带调制所需的射频上变换，脉冲成型后可直接送至天线发射。4.软件无线电技术软件无线电技术是在硬件平
11、台上通过软件编辑以一个终端实施不同系统中多种通信业务。它用数字信号处理语言描述电信元件，以软件程序下载成数字信号处理硬件（DSPH，Digital Signal Pocessing Hardware）。以具有通用开放无线结构（OWA，Open Wireless Architecture），兼容多种模式在多种技术标准之间无缝切换。5.网络安全和 QoSQoS 分为无线和有线侧两部分，无线侧的 QoS 涉及无线资源管理和调度，接纳控制和移动性管理等，移动性管理主要包括终端移动性，个人移动性和业务移动性。有线4侧的 QoS 涉及基于 IP diffSer 的区分业务和 RSVP 的端到端资源预留机制
12、。把 IP diffSer 的 IP QoS 机制映射到无线侧。网络安全包括网络接入安全，核心网安全，应用安全，安全机制可见性与可配置性。在上述现代移动通信关键技术的基础上，产生了陆地蜂窝移动通信、卫星通信以及无线因特网通信技术，这些通信方式使通信面貌发生了巨大的变化，采用数字技术的现代无线通信已经渗入国民经济的各个领域和人们的日常生活，为此，我们需要关心它的发展趋势，希望它朝着越来越方便人们的生活的方向发展，现在就让我们来看看现代移动通信的未来发展趋势吧。现代移动通信技术发展的七个新趋势:一、移动管理已从终端管理向个人管理和智能管理发展二、网络已从同步的数字电路向异步的数字分组和异步传递方式
13、(ATM)发展;三、软件的开发已从算法驱动到面向过程和面向目标的趋势发展;四、信息处理已从话音发展到数据和图像;五、无线频谱的处理已从窄带模拟向窄带 CDMA 发展;六、计算机已从集中式处理发展到分布式服务器和智能化处理;七、半导体器件已从每芯片 16 兆门/150MHz 速率的 VLSI 发展到 0.5 千兆门/350MHz 速率的 VLSI 和 2 千兆门 /550MHz 速率的 VLSI。在这种趋势的引导下，移动通信业务迅猛发展，它满足了人们在任何时间、任何地点与任何个人进行通信的愿望。移动通信是实现未来理想的个人通信服务的必由之路。在信息支撑技术、市场竞争和需求的共同作用下，移动通信技
14、术的发展更是突飞猛进，呈现出以下几大趋势：1)网络业务数据化、分组化；2)网络技术宽带化；3)网络技术智能化；4)更高的频段；5)更有效利用频率；6)各种网络趋于融合。了解、掌握这些趋势对移动通信运营商和设备制造商均具有重要的现实意义。5Modern mobile communication technology Mobile services in the growing market demand driven, 3G technology is gradually applied. Commercial 3G network from the current situation, the
15、 user market and the expectations of3G operators and network exists between the practical application of the gap. In the early 3G, many mobile communication experts and scholars are expected to 3G will be a completely universal and flexible, diversified, individualized 5A (Anyone, Anywhere, Anytime,
16、 Anydevice, Anything) method of seamless broadband access solutions, the unity in the network, business integration, service diversity, 3G will be the ideal choice for users. However, with the specification development, product realization, network business, service provision and other aspects of de
17、velopment, we can see, the existing WCDMA, cdma2000, TD-SCDMA technology in the application of three are facing difficulties. Clear understanding of these issues in the mobile communications industry for the development of an important position to occupy the mobile operators, has important strategic
18、 significance.From the perspective of mobile operators, network technologies, including products, technology implementation technology and network operations. Products to achieve the overall performance of technical network operations technologies, and network operators, technology and implementatio
19、n techniques to promote the product. This system, combined with the understanding of 3G network technology to the problems facing the application of given analysis.Implementation technology for 3G products, the biggest problem is how to achieve various performance “soft“ characteristics of balance a
20、nd stability. 3G CDMA system, wireless access technology used in the complexity of the system farmore than 2G GSM technology. CDMA wireless technology in the way of statistical multiplexing of resources, the user distinguish the use of code words, the user at the time, the frequency spectrum was sha
21、red characteristics, in order to reduce this “common“ cause “self-interference“ to achieve high-quality voice user side and data services, 3G networks need in the physical layer, link layer, network layer into a number of key wireless technologies, including power control, soft switching, multi-user
22、 detection, smart antennas, radio resource management, and for each of the key technologies not only down to include many types of implementations, and between the horizontal and o6ther technologies associated. Below the power control technology, for example, analysis of product realization technolo
23、gy problems.CDMA power control system to overcome the “distance effect“ a key technology used toachieve a balance of power between users, while ensuring that the system balance between coverage and capacity. Compared with GSM, 3G systems dependent on large power control andpower control accuracy and
24、 speed directly affects the network performance. The realization of the power control process, the base station and mobile speed of response and variability characteristics of the threshold is to limit the power control the speed of objective factors, the users mobile and wireless environment is to
25、limit the complexity of the power control accuracy of the objective factors. Since both the objective factors exist, the power control in 3G specifications can not give a clear limit. Therefore, the power control technology and applications in the realization was restrictive and uncertainties,which
26、features the one hand, map directly to the 3G network performance, the other hand, with other technologies (such as soft handover) is reflected indirectly related to the 3G network performance in both the network performance will lead to “soft features.“In now highly the informationization society,
27、the information and the correspondence have become the modern society “the life”. The information exchange mainly relies on the computer correspondence, but corresponds takes the transmission method, with the sensing technology, the computer technology fuses mutually, has become in the 21st century
28、the international society and the world economic development powerful engine. In order to of adapt the time request, the new generation of mobile communication technology seasonable and lives, the new generation of mobile communication technology is the people said that third generations core charac
29、teristic is the wide band addressing turns on non-gap roaming between the rigid network and numerous different communications systems, gains the multimedia communication services. Along with the time progress, the technical innovation, peoples life requests enhancement, the mobile communication tech
30、nology renewal speed is quite astonishing, almost every other ten year mobile communication technology has a transformation update, from the 1980s “the mobile phone” to presents 3G handset, during has had two mobile communication technology transformation, transits from 1G AMPS to 2G GSM, from GSM 7
31、to IMT-2000 (i.e. 3G technology). Knows modern on me the mobile communication technology to have the following several aspect important technology: 1. wideband modulation and multiple access technique The wireless high speed data transmission cannot only depend on the frequency spectrum constantly t
32、he expansion, should be higher than the present number magnitude at least in the frequency spectrum efficiency, may use three technologies in the physical level, namely OFDM, UWB and free time modulation code. OFDM with other encoding methods union, nimbly OFDM and TDMA, FDMA, CDMA, SDMA combines th
33、e multiple access technique. In the 1960s the OFDM multi-channel data transmission has succeeded uses in Kineplex and the Kathryn high frequency military channels. OFDM has used in 1.6 Mbit/s high bit rate digital subscriber line (HDSL), 6 Mbit/s asymmetrical digital subscriber line (ADSL), 100 Mbit
34、/s really high speed figure subscribers line (VDSL), digital audio frequency broadcast and digital video broadcast and so on. OFDM applies on 5 GHz provides 54 Mbit/s wireless local network IEEE 802.11 a and IEEE 802.11g, high performance this region network Hiper LAN/2 and ETSI-BRAN, but also takes
35、 metropolitan area network IEEE 802.16 and the integrated service digit broadcast (ISDB-T) the standard. Compares with the single load frequency modulation system service pattern, the OFDM modulation service pattern needs to solve the relatively big peak even power ratio (PAPR, Peak to Average Power
36、 Ratio) and to the frequency shifting and the phase noise sensitive question. High speed mobile communications another request is under the wide noise bandwidth, must demodulate the signal-to-noise ratio to reduce as far as possible, thus increases the cover area. May adopt the anti-fading the full
37、start power control and the pilot frequency auxiliary fast track demodulation technology, like the frequency range anti-fadings Rake receive and the track technology, the OFDMA technology which declines from the time domain and the frequency range resistance time and the frequency selectivity, the l
38、ink auto-adapted technology, the union coding technique. 2. frequency spectrum use factor lift technique The fundamental research pointed out: In the independent Rayleigh scattering channel, the data rate and the antenna several tenth linear relationships, the capacity may reach 8Shannon 90%. Is lau
39、nching and the receiving end may obtain the capacity and the frequency spectrum efficiency gain by the multi-antenna development channel space. The MIMO technology mainly includes the spatial multiplying and the space diversity technology, concurrent or the salvo same information enhances the transm
40、ission reliability on the independent channel. Receives and dispatches the bilateral space diversity is the high-capacity wireless communication system uses one of technical. Bell Lab free times opposite angle BLAST (D-BLAST) capacity increase to receive and dispatch the bilateral smallest antenna n
41、umber in administrative levels the function. The cross time domain which and the air zone expansion signal constitutes using MIMO may also resist the multi-diameter disturbance. V-BLAST system when indoor 2434 dB, the frequency spectrum use factor is 2040 bit/s/Hz. But launches and the receiving end
42、 uses 16 antennas, when 30 dB, the frequency spectrum use factor increases to 6070 bit/s/Hz. The smart antenna automatic tracking needs the signal and the auto-adapted free time processing algorithm, produces the dimensional orientation wave beam using the antenna array, causes the main wave beam al
43、ignment subscriber signal direction of arrival through the digital signal processing technology, the side lobe or zero falls the alignment unwanted signal direction of arrival. The auto-adapted array antennas (AAA, Adaptive Array Antennas) disturbs the counter-balance balancer (ICE, Interference Can
44、celing Equalizer) to be possible to reduce disturbs and cuts the emissive power. 3. software radio technology The software radio technology is in the hardware platform through the software edition by a terminal implementation different system in many kinds of communication services. It uses the digi
45、tal signal processing language description telecommunication part, downloads the digital signal processing hardware by the software routine (DSPH, Digital Signal Pocessing Hardware). By has the general opening wireless structure (OWA, Open Wireless Architecture), compatible many kinds of patterns be
46、tween many kinds of technical standards seamless cut. UWB is also called the pulse to be radio, the modulation uses the pulse width in the nanosecond level fast rise and the drop pulse, the pulse cover frequency spectrum from the 9cocurrent to the lucky hertz, does not need in the radio frequency wh
47、ich the convention narrow band frequency modulation needs to transform, after pulse formation, may deliver directly to the antenna launch. 4. software radio technology The software radio technology is in the hardware platform through the software edition by a terminal implementation different system
48、 in many kinds of communication services. It uses the digital signal processing language description telecommunication part, downloads the digital signal processing hardware by the software routine (DSPH, Digital Signal Pocessing Hardware). By has the general opening wireless structure (OWA, Open Wi
49、reless Architecture), compatible many kinds of patterns between many kinds of technical standards seamless cut. 5. network security and QoS QoS divides into wireless and the wired side two parts, wireless sides QoS involves the radio resource management and the dispatch, the admission control and the mobility management and so on, the mobility management mainly includes the terminal mobility, individual mobility and service mobility. Wired sides QoS involves based on the IP diffSer discrimination service and the RSVP end-to-end resources reservation mechanism. Mech
