通用移动通信系统的回顾外文翻译

1、.通用移动通信系统的回顾外文翻译 附件1:外文资料翻译译文通用移动通信系统的回顾1.1 UMTS网络架构 欧洲/日本的3G标准,被称为UMTS。 UMTS是一个在IMT-2000保护伞下的ITU-T批准的许多标准之一。随着美国的CDMA2000标准的发展,它是目前占主导地位的标准,特别是运营商将cdmaOne部署为他们的2G技术。在写这本书时,日本是在3G网络部署方面最先进的。三名现任运营商已经实施了三个不同的技术:J - PHONE使用UMTS,KDDI拥有CDMA2000网络,最大的运营商NTT DoCoMo正在使用品牌的FOMA(自由多媒体接入)系统。 FOMA是基于原来的UMTS协议,

2、而且更加的协调和标准化。 UMTS标准被定义为一个通过通用分组无线系统(GPRS)和全球演进的增强数据技术(EDGE)从第二代GSM标准到UNTS的迁移,如图。这是一个广泛应用的基本原理,因为自2003年4月起,全球有超过847万GSM用户,占全球的移动用户数字的68%。重点是在保持尽可能多的GSM网络与新系统的操作。 我们现在在第三代(3G)的发展道路上,其中网络将支持所有类型的流量:语音,视频和数据,我们应该看到一个最终的爆炸在移动设备上的可用服务。此驱动技术是IP协议。现在,许多移动运营商在简称为2.5G的位置,伴随GPRS的部署,即将IP骨干网引入到移动核心网。在下图中,图2显示了一个

3、在GPRS网络中的关键部件的概述,以及它是如何适应现有的GSM基础设施。 SGSN和GGSN之间的接口被称为Gn接口和使用GPRS隧道协议(GTP的,稍后讨论)。引进这种基础设施的首要原因是提供连接到外部分组网络如,Internet或企业Intranet。这使IP协议作为SGSN和GGSN之间的运输工具应用到网络。这使得数据服务,如移动设备上的电子邮件或浏览网页,用户被起诉基于数据流量,而不是时间连接基础上的数据量。3G网络和服务交付的主要标准是通用移动通信系统,或UMTS。首次部署的UMTS是发行'99架构,在下面的图3所示。 在这个网络中,主要的变化是在无线接入网络(RAN的)CD

4、MA空中接口技术的引进,和在传输部分异步传输模式作为一种传输方式。这些变化已经引入,主要是为了支持在同一网络上的语音,视频和数据服务的运输。核心网络保持相对不变,主要是软件升级。然而,随着目前无线网络控制器使用IP与3G的GPRS业务支持节点进行通信,IP协议进一步应用到网络。 未来的进化步骤是第4版架构,如图4。在这里,GSM的核心被以语音IP技术为基础的IP网络基础设施取代。 海安的发展分为两个独立部分:媒体网关(MGW)和MSC服务器(MSS)的。这基本上是打破外连接的作用和连接控制。一个MSS可以处理多个MGW,使网络更具有扩展性。 因为现在有一些在3G网络的IP云,合并这些到一个IP

5、或IP/ ATM骨干网是很有意义的(它很可能会提供两种选择运营商)。这使IP权利拓展到整个网络,一直到BTS基站收发信台。这被称为全IP网络,或推出五架构,如图五所示。在HLR/ VLR/VLR/EIR被推广和称为HLR的子系统(HSS)。 现在传统的电信交换的最后残余被删除,留下完全基于IP协议的网络运营,并推广了许多服务类型的运输。实时服务通过引入一个新的网络域名得到支持,即IP多媒体子系统(IMS)。 目前3GPP作用于第6版,意在包含冷冻版本没有涵盖所有方面。有些人称UMTS 第6版为4G和它包括热点无线电接入技术,如无线局域网互联互通的问题。1.2 UMTS的FDD和TDD 像任何C

6、DMA系统,UMTS需要一个宽的频带,在这个频带上有效地传播信号。该系统的特点是芯片的速度,芯片是一个符号的CDMA代码的宽度。 UMTS使用的芯片速率为3.84Mchips/秒,这转换到所需的频谱载波宽度为5MHz。由于这比现有的cdmaOne系统所需的1.25MHz带宽要宽,UNTS空中接口被称为“宽带”CDMA. 实际上在UMTS下有两个无线电技术:UMTS软盘驱动器和时分双工。FDD代表频分双工,如GSM,通过把它们放置在不同的频率信道分离为交通上行和下行。因此,一个运营商必须有一对频率分配,使他们能够运行网络,即术语成对频谱。TDD或时分双工只需要一个频率通道,上行和下行流量是在不同

7、的时间分开发送。 ITU-T的频谱使用,如在图6所示。对于FDD是1920 - 1980MHz的为上行流量,2110-2170MHz为下行的。运营商需要的最小分配是两个成对5MHz的信道,一个用于上行,一个用于下行的,两者相分离190MHz。然而,为了给客户提供全面的覆盖和服务,建议给予每个运营商三个信道。考虑到频谱分配,有12对可用的渠道,现在许多国家都完成了这个频谱的许可过程,每个许可证配置两个到四个信道。这趋向给运营商造成一个昂贵的花费,因为一些国家的监管部门,特别是在欧洲,已经将这些许可证拍卖给出价最高的人。这就造成了频谱费用在一些国家高达数十亿美元。 时分双工(TDD)系统,只需要一

8、个5MHz的带宽在其中操作,通常被称为非成对频谱。UMTS FDD和TDD之间的差异只有在较低层明显,特别是在无线接口。在更高的层次,两个系统的运作大部分是相同的。正如它的名字表明,TDD系统通过把它们放置在不同的时间空挡分为上行流量和下行流量。正如我们以后可以看到的, UMTS使用一个分为15个相等的时隙的10ms帧结构。 时分双工可以分配这些为上行或下行,在一个确定的帧结构中这两者间可以有一个或多个断点。以这种方式,这是非常适合数据包通信的,因为这对于不对称的通信流的动态标注可以有极大的灵活性。 TDD系统真的不应该被视为一个独立的网络,而是作为一个FDD系统的补充,提供更高的数据传输率的

9、热点覆盖。由于站点之间的干扰,它相当不合适用作大规模部署,因为一个基站可以尝试从UE检测微弱信号,这被来自邻近基站的相同频率的相对较强的信号阻止了。 时分双工对于小面积的室内覆盖是理想的。 由于FDD是目前正在发展的主要的接入技术,这里介绍的解释将完全专注于这个系统。1.3 UMTS承载模型 移动设备连接到UMTS网络的程序可以分成两领域:接入层(AS)和非接入层(NAS)。接入层涉及所有提供普遍服务的非接入层和子系统阶层。在UMTS接入层包括无线接入的所有元素网络,包括潜在的ATM传输网络,各种机制提供可靠的信息交换等。所有的非接入层功能都在移动设备和核心网络之间,例如,移动性管理。图7显示

10、了结构模型。AS通过使用服务接入点(SAPS)与NAS交互。 UMTS无线接入网(UTRAN)提供NAS和AS功能的分离,并允许AS功能在UTRAN中被完全控制和实施。两大UTRAN的接口是UU,这是移动设备之间的接口,或者用户设备(UE)和UTRAN之间,Iu,这是UTRAN和核心网之间的接口。这些接口都可以分为控制平面和用户平面,每个都有适当的协议功能。承载服务是两点间的连接,这是由一组特定的特点定义的。在UMTS的情况下,使用无线接入承载提供承载服务。 无线接入承载(RAB)被定义为用户设备和核心网络之间的服务,即接入层(ieUTRAN)为非接入层提供用户数据传输。一个RAB可以由一些支

11、流组成,这是数据流在有不同的QoS特性的RAB流向核心网络,如不同的可靠性。一个常见的?例子是不同类别的位有不同的位错误率,可以实现不同的RAB子流。RAB子流在RAB建立和释放的同时建立和释放,并通过相同的传输承载一起传输。 无线电链路被定义为一个单一的用户设备(UE)和一个单一的UTRAN接入点之间的逻辑关联,如一个RNC。它实际上是由一个或多个无线承载组成和不应和无线接入承载混淆。 在UTRAN内部来看,总体架构模型在下面的图8所示。现在显示的是节点B基站(BTS)和无线网络控制器(RNC)组件,以及它们各自的内部接口。UTRAN分为被称为无线网络子系统(RNS)的块,其中每个RNS由一

12、个控制RNC和控制下的所有基站组成。UMTS的独特之处是RNS之间的接口,Iur接口,在交接过程起了关键作用。基站和RNC之间的接口是Iub接口。 所有“I”接口:Iu,Iur和Iub,currently3将ATM用作传输层。在ATM的背景下,BTS被看作是ATM网络的主机访问,在这个网络中RNC是一个ATM交换机。因此,Iub是一个UNI接口,而Iu和Iur接口被认为是NNI,如图9所示。 这种区别是因为基站到RNC的链接是一个点至点连接,在这个连接中一个基站或RNC只和与它直接连接的RNC或基站通信,并且不会要求和其他网络元素的元素。 对于每个用户连接到核心网络,这里只有一个RNC,保持U

13、E和核心网域之间的联系,在图10中突出显示。RNC是指服务RNC或SRNC。SRNC加上在其控制下的基站被称为SRNS。这是一个只以UE为参考的逻辑定义。在一个RNS中,控制基站的RNC被称为控制RNC或CRNC。这是以基站为参考,其控制下的部分和所有常见的和共享的渠道内。 因为UE移动,它可能执行软或硬切换到另一个蜂窝。在软切换的情况下,SRNC将启动新的连接到新的基站。新的基站应该是在另一个RNC控制下,SRNC中也会提醒这个新的RNC启动沿Iur接口连接。UE现在有两个连接,一个直接连接SRNC,第二个通过新的RNC连接Iur接口。在这种情况下,这个新的RNC在逻辑上被称为漂移RNC或D

14、RNC,见图10。它不涉及任何呼叫处理,只是将它中继到SRNC以连接核心网络,总之,SRNC和DRNC通常与UE相关联,CRNC与BTS相关联。由于这些是逻辑功能,一个单一的RNC是能够处理所有这些功能是很正常的做法。 一个UE连接到基站,它的SRNC并不是这个基站的控制RNC,这种情况可能会出现。在这种情况下,这个网络可以调用SRNC的搬移程序来移动核心网络的连接。在第3节将介绍此过程。附件2:外文原文Review of UMTS 1.1 UMTS Network Architecture The European/Japanese 3G standard is referred to as

15、 UMTS. UMTS is one of a number of standards ratified by the ITU-T under the umbrella of IMT-2000. It is currently the dominant standard, with the US CDMA2000 standard gaining ground, particularly with operators that have deployed cdmaOne as their 2G technology. At time of writing,Japan is the most a

16、dvanced in terms of 3G network deployment. The three incumbent operators there have implemented three different technologies: J-Phone is using UMTS,KDDI has a CDMA2000 network, and the largest operator NTT DoCoMo is using a system branded as FOMA Freedom of Multimedia Access. FOMA is based on the or

17、iginal UMTS proposal, prior to its harmonization and standardization. The UMTS standard is specified as a migration from the second generation GSM standard to UMTS via the General Packet Radio System GPRS and Enhanced Data for Global Evolution EDGE, as shown in Figure. This is a sound rationale sinc

18、e as of April 2003, there were over 847 Million GSM subscribers worldwide1, accounting for68% of the global cellular subscriber figures. The emphasis is on keeping as much ofthe GSM network as possible to operate with the new system. We are now well on the road towards Third Generation 3G, where the

19、 network will support all traffic types: voice, video and data, and we should see an eventual explosion in the services available on the mobile device. The driving technology for this is the IP protocol. Many cellular operators are now at a position referred to as 2.5G, with the deployment of GPRS,

20、which introduces an IP backbone into the mobile core network.The diagram below, Figure 2, shows an overview of the key components in a GPRS network, and how it fits into the existing GSM infrastructure. The interface between the SGSN and GGSN is known as the Gn interface and uses the GPRS tunneling

21、protocol GTP, discussed later. The primary reason for the introduction of this infrastructure is to offer connections to external packet networks, such as the Internet or a corporate Intranet. This brings the IP protocol into the network as a transport between the SGSN and GGSN. This allows data ser

22、vices such as email or web browsing on the mobile device,with users being charged based on volume of data rather than time connected. The dominant standard for delivery of 3G networks and services is the Universal Mobile Telecommunications System, or UMTS. The first deployment of UMTS is the Release

23、 99 architecture, shown below in Figure 3. In this network, the major change is in the radio access network RAN with the introduction of CDMA technology for the air interface, and ATM as a transport in the transmission part. These changes have been introduced principally to support the transport of

24、voice, video and data services on the same network. The core network remains relatively unchanged, with primarily software upgrades. However, the IP protocol pushes further into the network with the RNC now communicating with the 3G SGSN using IP. The next evolution step is the Release 4 architectur

25、e, Figure 4. Here, the GSM core is replaced with an IP network infrastructure based around Voice over IP technology. The MSC evolves into two separate components: a Media Gateway MGW and an MSC Server MSS. This essentially breaks apart the roles of connection and connection control. An MSS can handl

26、e multiple MGWs, making the network more scaleable. Since there are now a number of IP clouds in the 3G network, it makes sense to merge these together into one IP or IP/ATM backbone it is likely both options will be available to operators. This extends IP right across the whole network, all the way

27、 to the BTS.This is referred to as the All-IP network, or the Release 5 architecture, as shown in Figure 5. The HLR/VLR/EIR are generalised and referred to as the HLR SubsystemHSS. Now the last remnants of traditional telecommunications switching are removed, leaving a network operating completely o

28、n the IP protocol, and generalised for the transport of many service types. Real-time services are supported through the introduction of a new network domain, the IP Multimedia Subsystem IMS. Currently the 3GPP are working on Release 6, which purports to cover all aspects not addressed in frozen rel

29、eases. Some call UMTS Release 6 4G and it includes such issues as interworking of hot spot radio access technologies such as wireless LAN.1.2 UMTS FDD and TDD Like any CDMA system, UMTS needs a wide frequency band in which to operate to effectively spread signals. The defining characteristic of the

30、system is the chip rate, where a chip is the width of one symbol of the CDMA code. UMTS uses a chip rate of 3.84Mchips/s and this converts to a required spectrum carrier of 5MHz wide. Since this is wider than the 1.25MHz needed for the existing cdmaOne system, the UMTS air interface is termed wideba

31、nd CDMA. There are actually two radio technologies under the UMTS umbrella: UMTS FDD and TDD. FDD stands for Frequency Division Duplex, and like GSM, separates traffic in the uplink and downlink by placing them at different frequency channels. Therefore an operator must have a pair of frequencies al

32、located to allow them to run a network, hence the term paired spectrum. TDD or Time Division Duplex requires only one frequency channel, and uplink and downlink traffic are separated by sending them at different times. The ITU-T spectrum usage, as shown in Figure 6, for FDD is 1920- 980MHz for uplin

33、k traffic, and 2110-2170MHz for downlink. The minimum allocation an operator needs is two paired 5MHz channels, one for uplink and one for downlink, at a separation of 190MHz. However, to provide comprehensive coverage and services, it is recommended that an operator be given three channels. Conside

34、ring the spectrum allocation, there are 12 paired channels available, and many countries have now completed the licencing process for this spectrum, allocating between two and four channels per licence. This has tended to work out a costly process for operators, since the regulatory authorities in s

35、ome countries, notably in Europe, have auctioned these licences to the highest bidder. This has resulted in spectrum fees as high as tens of billions of dollars in some countries. The Time Division Duplex TDD system, which needs only one 5MHz band in which to operate, often referred to as unpaired s

36、pectrum. The differences between UMTS FDD and TDD are only evident at the lower layers, particularly on the radio interface. At higher layers, the bulk of the operation of the two systems is the same. As the name suggests, the TDD system separates uplink and downlink traffic by placing them in diffe

37、rent time slots. As will be seen later, UMTS uses a 10ms frame structure which is divided into 15 equal timeslots. TDD can allocate these to be either uplink or downlink,with one or more breakpoints between the two in a frame defined. In this way, it is well suited to packet traffic, since this allo

38、ws great flexibility in dynamically dimensioning for asymmetry in traffic flow. The TDD system should not really be considered as an independent network, but rather as a supplement for an FDD system to provide hotspot coverage at higher data rates. It is rather unsuitable for large scale deployment

39、due to interference between sites, since a BTS may be trying to detect a weak signal from a UE, which is blocked out by a relatively strong signal at the same frequency from a nearby BTS. TDD is ideal for indoor coverage over small areas. Since FDD is the main access technology being developed curre

40、ntly, the explanations presented here will focus purely on this system.1.3 UMTS Bearer Model The procedures of a mobile device connecting to a UMTS network can be split into two areas: the access stratum AS and the non-access stratum NAS. The access stratum involves all the layers and subsystems tha

41、t offer general services to the non-access stratum. In UMTS, the access stratum consists of all of the elements in the radio access network, including the underlying ATM transport network, and the various mechanisms such as those to provide reliable information exchange. All of the non-access stratu

42、m functions are those between the mobile device and the core network, for example, mobility management. Figure 7 shows the architecture model. The AS interacts with the NAS through the use of service access points SAPs. UMTS radio access network UTRAN provides this separation of NAS and AS functions

43、, and allows for AS functions to be fully controlled and implemented within the UTRAN. The two major UTRAN interfaces are the Uu, which is the interface between the mobile device, or User Equipment UE and the UTRAN, and the Iu, which is the interface between the UTRAN and the core network. Both of t

44、hese interfaces can be divided into control and user planes each with appropriate protocol functions. A Bearer Service is a link between two points, which is defined by a certain set of characteristics. In the case of UMTS, the bearer service is delivered using radio access bearers. A Radio access b

45、earer RAB is defined as the service that the access stratum /.AN provides to the non-access stratum for transfer of user data between the User Equipment and Core Network. A RAB can consist of a number of subflows, which are data streams to the core network within the RAB that have different QoS char

46、acteristics,such as different reliabilities. A common example of this is different classes of bits with different bit error rates can be realised as different RAB subflows. RAB subflows are established and released at the time the RAB is established and released, and are delivered together over the

47、same transport bearer. A Radio Link is defined as a logical association between a single User Equipment UE and a single UTRAN access point, such as an RNC. It is physically comprised of one or more radio bearers and should not be confused with radio access bearer. Looking within the UTRAN, the gener

48、al architecture model is as shown in Figure 8 below. Now shown are the Node B or Base Station BTS and Radio Network Controller RNC components, and their respective internal interfaces. The UTRAN is subdivided into blocks referred to as Radio Network Subsystems RNS, where each RNS consists of one con

49、trolling RNC CRNC and all the BTSs under its control. Unique to UMTS is the interface between RNSs, the Iur interface, which plays a key role in handover procedures. The interface between the BTS and RNC is the Iub interface. All the I interfaces: Iu, Iur and Iub, currently3 use ATM as a transport l

50、ayer. In the context of ATM, the BTS is seen as a host accessing an ATM network, within which the RNC is an ATM switch. Therefore, the Iub is a UNI interface, whereas the Iu and Iur interfaces are considered to be NNI, as illustrated in Figure 9. This distinction is because the BTS to RNC link is a point-to-point connection in that a BTS or RNC will only communicate with the RNC or BTS directly connected to it, and will not require communication beyond