通信工程外文文獻(共12頁)

1、精選優(yōu)質(zhì)文檔-傾情為你奉上外文資料與中文翻譯外文資料：Review of UMTS1.1 UMTS Network ArchitectureThe European/Japanese 3G standard is referred to as 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 grou

2、nd, particularly with operators that have deployed cdmaOne as their 2G technology. At time of writing,Japan is the most advanced 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, an

3、d the largest operator NTT DoCoMo is using a system branded as FOMA (Freedom of Multimedia Access). FOMA is based on the original 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 Genera

4、l Packet Radio System (GPRS) and Enhanced Data for Global Evolution (EDGE), as shown in Figure. This is a sound rationale since 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 of

5、the GSM network as possible to operate with the new system.We are now well on the road towards Third Generation (3G), where the 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 technolog

6、y for this is the IP protocol. Many cellular operators are now at a position referred to as 2.5G, with the deployment of GPRS, 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

7、 existing GSM infrastructure.The interface between the SGSN and GGSN is known as the Gn interface and uses the GPRS tunneling 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

8、 corporate Intranet.This brings the IP protocol into the network as a transport between the SGSN and GGSN. This allows data services 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

9、 networks and services is the Universal Mobile Telecommunications System, or UMTS. The first deployment of UMTS is the Release 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 interfac

10、e, and ATM as a transport in the transmission part. These changes have been introduced principally to support the transport of 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

11、into the network with the RNC now communicating with the 3G SGSN using IP.The next evolution step is the Release 4 architecture, 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 Gate

12、way (MGW) and an MSC Server (MSS). This essentially breaks apart the roles of connection and connection control. An MSS can handle 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/AT

13、M backbone (it is likely both options will be available to operators.) This extends IP right across the whole network, all the way 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 Sub

14、system(HSS).Now the last remnants of traditional telecommunications switching are removed, leaving a network operating completely on 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 Mul

15、timedia Subsystem (IMS).Currently the 3GPP are working on Release 6, which purports to cover all aspects not addressed in frozen releases. 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 TDDLike any C

16、DMA system, UMTS needs a wide frequency band in which to operate to effectively spread signals. The defining characteristic of the 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

17、 of 5MHz wide. Since this is wider than the 1.25MHz needed for the existing cdmaOne system, the UMTS air interface is termed wideband 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

18、 the uplink and downlink by placing them at different frequency channels. Therefore an operator must have a pair of frequencies allocated 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 a

19、re separated by sending them at different times. The ITU-T spectrum usage, as shown in Figure 6, for FDD is 1920- 980MHz for uplink 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 19

20、0MHz. However, to provide comprehensive coverage and services, it is recommended that an operator be given three channels. Considering the spectrum allocation, there are 12 paired channels available, and many countries have now completed the licencing process for this spectrum, allocating between tw

21、o and four channels per licence. This has tended to work out a costly process for operators, since the regulatory authorities in some 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 c

22、ountries.The Time Division Duplex (TDD) system, which needs only one 5MHz band in which to operate, often referred to as unpaired spectrum. 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

23、of the two systems is the same. As the name suggests, the TDD system separates uplink and downlink traffic by placing them in different 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

24、,with one or more breakpoints between the two in a frame defined. In this way, it is well suited to packet traffic, since this allows 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

25、supplement for an FDD system to provide hotspot coverage at higher data rates. It is rather unsuitable for large scale deployment 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 f

26、rom a nearby BTS. TDD is ideal for indoor coverage over small areas.Since FDD is the main access technology being developed currently, the explanations presented here will focus purely on this system.1.3 UMTS Bearer ModelThe procedures of a mobile device connecting to a UMTS network can be split int

27、o two areas: the access stratum (AS) and the non-access stratum (NAS). The access stratum involves all the layers and subsystems that 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 AT

28、M transport network, and the various mechanisms such as those to provide reliable information exchange. All of the non-access stratum 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

29、 NAS through the use of service access points (SAPs). UMTS radio access network (UTRAN) provides this separation of NAS and AS functions, 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

30、 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 these 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 defin

31、ed by a certain set of characteristics. In the case of UMTS, the bearer service is delivered using radio access bearers.A Radio access bearer (RAB) is defined as the service that the access stratum (i.e.UTRAN) provides to the non-access stratum for transfer of user data between the User Equipment an

32、d 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 characteristics,such as different reliabilities. A common example of this is different classes of bits with different bit error rates can be realised as differ

33、ent RAB subflows. RAB subflows are established and released at the time the RAB is established and released, and are delivered together over the 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

34、. It is physically comprised of one or more radio bearers and should not be confused with radio access bearer.Looking within the UTRAN, the general 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 thei

35、r respective internal interfaces. The UTRAN is subdivided into blocks referred to as Radio Network Subsystems (RNS), where each RNS consists of one controlling 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 ha

36、ndover 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 layer. 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

37、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

38、 beyond that element to another network element. For each user connection to the core network, there is only one RNC, which maintains the link between the UE and core network domain, as highlighted in Figure 10. This RNC is referred to as the serving RNC or SRNC. That SRNC plus the BTSs under its co

39、ntrol is then referred to as the SRNS. This is a logical definition with reference to that UE only. In an RNS, the RNC that controls a BTS is known as the controlling RNC or CRNC. This is with reference to the BTS, cells under its control and all the common and shared channels within.As the UE moves

40、, it may perform a soft or hard handover to another cell. In the case of a soft handover, the SRNC will activate the new connection to the new BTS. Should the new BTS be under the control of another RNC, the SRNC will also alert this new RNC to activate a connection along the Iur interface. The UE n

41、ow has two links, one directly to the SRNC, and the second, through the new RNC along the Iur interface. In this case, this new RNC is logically referred to as a drift RNC or DRNC, see Figure 10. It is not involved in any processing of the call and merely relays it to the SRNC for connection to the

42、core. In summary, SRNC and DRNC are usually associated with the UE and the CRNC is associated with the BTS. Since these are logical functions it is normal practice that a single RNC is capable of dealing with all these functions.A situation may arise where a UE is connected to a BTS for which the SR

43、NC is not the CRNC for that BTS. In that situation, the network may invoke the Serving RNC Relocation procedure to move the core network connection. This process is described inSection 3.中文翻譯：通用移動通信系統(tǒng)的回顧1.1 UMTS網(wǎng)絡(luò)架構(gòu)歐洲/日本的3G標準，被稱為UMTS。 UMTS是一個在IMT-2000保護傘下的ITU-T批準的許多標準之一。隨著美國的CDMA2000標準的發(fā)展，它是目前占主導(dǎo)地位的

44、標準，特別是運營商將cdmaOne部署為他們的2G技術(shù)。在寫這本書時，日本是在3G網(wǎng)絡(luò)部署方面最先進的。三名現(xiàn)任運營商已經(jīng)實施了三個不同的技術(shù)：J - PHONE使用UMTS，KDDI擁有CDMA2000網(wǎng)絡(luò)，最大的運營商NTT DoCoMo正在使用品牌的FOMA（自由多媒體接入）系統(tǒng)。 FOMA是基于原來的UMTS協(xié)議，而且更加的協(xié)調(diào)和標準化。UMTS標準被定義為一個通過通用分組無線系統(tǒng)（GPRS）和全球演進的增強數(shù)據(jù)技術(shù)（EDGE）從第二代GSM標準到UNTS的遷移，如圖。這是一個廣泛應(yīng)用的基本原理，因為自2003年4月起，全球有超過847萬GSM用戶，占全球的移動用戶數(shù)字的68。重點是在

45、保持盡可能多的GSM網(wǎng)絡(luò)與新系統(tǒng)的操作。我們現(xiàn)在在第三代（3G）的發(fā)展道路上，其中網(wǎng)絡(luò)將支持所有類型的流量：語音，視頻和數(shù)據(jù)，我們應(yīng)該看到一個最終的爆炸在移動設(shè)備上的可用服務(wù)。此驅(qū)動技術(shù)是IP協(xié)議?，F(xiàn)在，許多移動運營商在簡稱為2.5G的位置，伴隨GPRS的部署，即將IP骨干網(wǎng)引入到移動核心網(wǎng)。在下圖中，圖2顯示了一個在GPRS網(wǎng)絡(luò)中的關(guān)鍵部件的概述，以及它是如何適應(yīng)現(xiàn)有的GSM基礎(chǔ)設(shè)施。 SGSN和GGSN之間的接口被稱為Gn接口和使用GPRS隧道協(xié)議（GTP的，稍后討論）。引進這種基礎(chǔ)設(shè)施的首要原因是提供連接到外部分組網(wǎng)絡(luò)如，Internet或企業(yè)Intranet。這使IP協(xié)議作為SGSN和

46、GGSN之間的運輸工具應(yīng)用到網(wǎng)絡(luò)。這使得數(shù)據(jù)服務(wù)，如移動設(shè)備上的電子郵件或瀏覽網(wǎng)頁，用戶被起訴基于數(shù)據(jù)流量，而不是時間連接基礎(chǔ)上的數(shù)據(jù)量。3G網(wǎng)絡(luò)和服務(wù)交付的主要標準是通用移動通信系統(tǒng)，或UMTS。首次部署的UMTS是發(fā)行'99架構(gòu)，在下面的圖3所示。在這個網(wǎng)絡(luò)中，主要的變化是在無線接入網(wǎng)絡(luò)（RAN的）CDMA空中接口技術(shù)的引進，和在傳輸部分異步傳輸模式作為一種傳輸方式。這些變化已經(jīng)引入，主要是為了支持在同一網(wǎng)絡(luò)上的語音，視頻和數(shù)據(jù)服務(wù)的運輸。核心網(wǎng)絡(luò)保持相對不變，主要是軟件升級。然而，隨著目前無線網(wǎng)絡(luò)控制器使用IP與3G的GPRS業(yè)務(wù)支持節(jié)點進行通信，IP協(xié)議進一步應(yīng)用到網(wǎng)絡(luò)。未來的

47、進化步驟是第4版架構(gòu)，如圖4。在這里，GSM的核心被以語音IP技術(shù)為基礎(chǔ)的IP網(wǎng)絡(luò)基礎(chǔ)設(shè)施取代。海安的發(fā)展分為兩個獨立部分：媒體網(wǎng)關(guān)（MGW）和MSC服務(wù)器（MSS）的。這基本上是打破外連接的作用和連接控制。一個MSS可以處理多個MGW，使網(wǎng)絡(luò)更具有擴展性。因為現(xiàn)在有一些在3G網(wǎng)絡(luò)的IP云，合并這些到一個IP或IP/ ATM骨干網(wǎng)是很有意義的（它很可能會提供兩種選擇運營商）。這使IP權(quán)利拓展到整個網(wǎng)絡(luò)，一直到BTS(基站收發(fā)信臺)。這被稱為全IP網(wǎng)絡(luò)，或推出五架構(gòu)，如圖五所示。在HLR/ VLR/VLR/EIR被推廣和稱為HLR的子系統(tǒng)（HSS）?，F(xiàn)在傳統(tǒng)的電信交換的最后殘余被刪除，留下完全基

48、于IP協(xié)議的網(wǎng)絡(luò)運營，并推廣了許多服務(wù)類型的運輸。實時服務(wù)通過引入一個新的網(wǎng)絡(luò)域名得到支持，即IP多媒體子系統(tǒng)（IMS）。目前3GPP作用于第6版，意在包含冷凍版本沒有涵蓋所有方面。有些人稱UMTS 第6版為4G和它包括熱點無線電接入技術(shù)，如無線局域網(wǎng)互聯(lián)互通的問題。1.2 UMTS的FDD和TDD像任何CDMA系統(tǒng)，UMTS需要一個寬的頻帶，在這個頻帶上有效地傳播信號。該系統(tǒng)的特點是芯片的速度，芯片是一個符號的CDMA代碼的寬度。 UMTS使用的芯片速率為3.84Mchips/秒，這轉(zhuǎn)換到所需的頻譜載波寬度為5MHz。由于這比現(xiàn)有的cdmaOne系統(tǒng)所需的1.25MHz帶寬要寬，UNTS空中

49、接口被稱為“寬帶”CDMA.實際上在UMTS下有兩個無線電技術(shù)：UMTS軟盤驅(qū)動器和時分雙工。FDD代表頻分雙工，如GSM，通過把它們放置在不同的頻率信道分離為交通上行和下行。因此，一個運營商必須有一對頻率分配，使他們能夠運行網(wǎng)絡(luò)，即術(shù)語成對頻譜。TDD或時分雙工只需要一個頻率通道，上行和下行流量是在不同的時間分開發(fā)送。 ITU-T的頻譜使用，如在圖6所示。對于FDD是1920 - 1980MHz的為上行流量，2110-2170MHz為下行的。運營商需要的最小分配是兩個成對5MHz的信道，一個用于上行，一個用于下行的，兩者相分離190MHz。然而，為了給客戶提供全面的覆蓋和服務(wù)，建議給予每個運

50、營商三個信道?？紤]到頻譜分配，有12對可用的渠道，現(xiàn)在許多國家都完成了這個頻譜的許可過程，每個許可證配置兩個到四個信道。這趨向給運營商造成一個昂貴的花費，因為一些國家的監(jiān)管部門，特別是在歐洲，已經(jīng)將這些許可證拍賣給出價最高的人。這就造成了頻譜費用在一些國家高達數(shù)十億美元。時分雙工（TDD）系統(tǒng)，只需要一個5MHz的帶寬在其中操作，通常被稱為非成對頻譜。UMTS FDD和TDD之間的差異只有在較低層明顯，特別是在無線接口。在更高的層次，兩個系統(tǒng)的運作大部分是相同的。正如它的名字表明，TDD系統(tǒng)通過把它們放置在不同的時間空擋分為上行流量和下行流量。正如我們以后可以看到的， UMTS使用一個分為15個相等的時隙的10ms幀結(jié)構(gòu)。 時分雙工可以分配這些為上行或下行，在一個確定的幀結(jié)構(gòu)中這兩者間可以有一個或多個斷點。以這種方式，這是非常適合數(shù)據(jù)包通信的，因為這對于不對稱的通信流的動態(tài)標注可以有極大的靈活性。TDD系統(tǒng)真的不應(yīng)該被視為一個獨立的網(wǎng)絡(luò)，而是作為一個FDD系統(tǒng)的補充，提供更高的數(shù)據(jù)傳輸率