通信專業(yè)畢業(yè)設(shè)計(jì)論文外文翻譯中英文對(duì)照WPF概述

1、通信專業(yè) 畢業(yè)設(shè)計(jì)論文 外文翻譯中英文對(duì)照： WPF概述理工學(xué)院 畢業(yè)設(shè)計(jì)外文資料翻譯專 業(yè):姓 名 :學(xué) 號(hào) :外文出處 : Matthew.Pro WPF in C# 2010 Apress.2010附 件 : 1. 外文資料翻譯譯文 ;2. 外文原文 指導(dǎo)教師評(píng)語(yǔ) :簽名: 年月日附件 1: 外文資料翻譯譯文WPF既述蜂窩無(wú)線電通信行業(yè)在過(guò)去十年中目睹了全球擁有了超過(guò)四十億無(wú)線用戶這一巨大發(fā)展，第一代(1G)模擬蜂窩系統(tǒng)只支持有限的漫游語(yǔ)音通信 ，而第二 代(2G)數(shù)字系統(tǒng)比第一代有更高的容量和更好的語(yǔ)音質(zhì)量。此外 ，由于在各個(gè)國(guó) 家特別是在歐洲國(guó)家對(duì)漫游有相同的標(biāo)準(zhǔn)和共同的頻譜分配 ,

2、 因此使之變得更為 普遍。在第二代(2G)蜂窩系統(tǒng)中,有兩個(gè)是比較廣泛部署的,他們分別是GSM全 球移動(dòng)通信系統(tǒng))和CDMA碼分多址)。相比于1G的模擬系統(tǒng),2G系統(tǒng)主要支持語(yǔ) 音通信。在后來(lái)發(fā)布 2G 版本的標(biāo)準(zhǔn)中 , 主要介紹了其支持?jǐn)?shù)據(jù)傳輸?shù)哪芰?。?而,2G的數(shù)據(jù)傳輸速率普遍低于撥號(hào)連接支持,因此有了 3G系統(tǒng)的出現(xiàn),而ITU-R 倡議的 IMT-2000（ 國(guó)際移動(dòng)電信 2000 年） 為向 3G 的演進(jìn)鋪平了道路。根據(jù) IMT-2000的倡議，相關(guān)部門發(fā)表了一系列要求，如2 Mb / s的峰值數(shù)據(jù)率和車輛 的流動(dòng)性支持。GSM和CDM形成了自己獨(dú)立的3G合作伙伴項(xiàng)目（3GPP和3G

3、PP2）, 使IMT-2000標(biāo)準(zhǔn)發(fā)展成基于CDM/技術(shù)的標(biāo)準(zhǔn)。3GPP的3G標(biāo)準(zhǔn)被稱為寬帶 CDMA（WCDM因?yàn)樗褂昧讼啾?GPP的 CDMA200系統(tǒng)中1.25兆赫帶寬來(lái)說(shuō)更 大的5兆赫帶寬。3GPP2還制定了一個(gè)5兆赫茲的版本,支持三個(gè)1.25兆赫到副 載波，其被稱為CDMA2000-3X為了分化從5兆赫茲的CDMA2000-3的標(biāo)準(zhǔn),1.25 兆赫茲的系統(tǒng)被稱為CDMA2000-1X或者干脆稱為3G-1%首次發(fā)布的 3G 標(biāo)準(zhǔn)并沒(méi)有履行其所說(shuō)的承諾 , 使高速數(shù)據(jù)傳輸?shù)臄?shù)據(jù)在 實(shí)踐中的支持率遠(yuǎn)遠(yuǎn)低于當(dāng)時(shí)聲稱的標(biāo)準(zhǔn)。 因此其需要作出一系列認(rèn)真努力來(lái)提 高有效地?cái)?shù)據(jù)來(lái)支持3G系統(tǒng)。3G

4、PP沖首先介紹了 HRPD系統(tǒng)（高速率分組數(shù)據(jù)） 系統(tǒng)使用的數(shù)據(jù)流量,如通道敏感的調(diào)度,快速鏈路自適應(yīng)和混合 ARC等 HRPD系 統(tǒng)。系統(tǒng)優(yōu)化的各種先進(jìn)技術(shù) , 需要一個(gè)獨(dú)立的 1.25 兆赫茲載波和只支持沒(méi)有 語(yǔ)音的服務(wù)。正因?yàn)槿绱?HRPD系統(tǒng)最初被稱為CDMA2000-1XEVD演進(jìn)數(shù)據(jù)）系 統(tǒng)。3GPP沿襲一種與之類似路徑,并介紹HSPA高速分組接入）技術(shù)提高對(duì) WCDMA 系統(tǒng)的訪問(wèn)。HSPA勺標(biāo)準(zhǔn)重復(fù)使用許多相同的數(shù)據(jù)優(yōu)化技術(shù)為 HRPD系統(tǒng)。然而， 一個(gè)相對(duì)于HRPD系統(tǒng)來(lái)說(shuō)的的差異是,在HSPAh相同的兩個(gè)5 MHz載波可以同 時(shí)進(jìn)行語(yǔ)音和數(shù)據(jù)傳輸。平行于HRPD系統(tǒng),3GP

5、P2同時(shí)也制定了一個(gè)聯(lián)合的語(yǔ)音 數(shù)據(jù)標(biāo)準(zhǔn),被稱為CDMA2000-1XEVDV演進(jìn)數(shù)據(jù)語(yǔ)音）。像 HSPA 一 樣,CDMA2000-1xEVD系統(tǒng)支持同一載波上語(yǔ)音和數(shù)據(jù),但是它從不商業(yè)化。在以 后公布的HRPD,VolP互聯(lián)網(wǎng)協(xié)議語(yǔ)音）,介紹了其提供語(yǔ)音和數(shù)據(jù)服務(wù)在同一載 體的能力?，F(xiàn)在,兩個(gè)3G標(biāo)準(zhǔn),即HSPA和HRPD系統(tǒng)終于能夠?qū)崿F(xiàn)3G的承諾,并 已被廣泛部署在主要的蜂窩市場(chǎng)提供無(wú)線數(shù)據(jù)接入。1.1超越3G系統(tǒng)當(dāng)HSPA HRPD系統(tǒng)得到了開(kāi)發(fā)和部署，IEEE 802 LMSC（局域網(wǎng)/城域網(wǎng)標(biāo) 準(zhǔn)委員會(huì) ）也推出了 lEEE 802.16e 移動(dòng)寬帶無(wú)線接入的標(biāo)準(zhǔn)。 這個(gè)標(biāo)準(zhǔn)作為一

6、種 增強(qiáng)被引入到一個(gè)較早的IEEE802.16的標(biāo)準(zhǔn)固定寬帶無(wú)線接入中去。以802.16e 標(biāo)準(zhǔn)命名的OFDMAf交頻分多址接入）采用不同的接入技術(shù),并聲稱比HSPA和 HRPD系統(tǒng)提供、更好的數(shù)據(jù)傳輸速率和頻譜效率。IEEE 802.16系列標(biāo)準(zhǔn)被正式 稱為IEEE無(wú)線都會(huì)網(wǎng)路，它被稱為名為 Wi論壇的一個(gè)產(chǎn)業(yè)群的 Wi（全球微波接 入互操作性 ） 。 Wi 論壇的使命是促進(jìn)和認(rèn)證寬帶無(wú)線接入產(chǎn)品的兼容性和互操作 性。支持在IEEE 802.16e標(biāo)準(zhǔn)的移動(dòng) Wi系統(tǒng)被稱為移動(dòng) Wi。除了無(wú)線電技術(shù) 的優(yōu)勢(shì) , 移動(dòng) Wi 還雇用了一個(gè)簡(jiǎn)單的基于 IP 協(xié)議的網(wǎng)絡(luò)架構(gòu)。引入移動(dòng) Wi,3GP

7、P和 3GPP2超越基于OFDM技術(shù)和網(wǎng)絡(luò)架構(gòu)，在類似的移 動(dòng)Wi的3G系統(tǒng)上開(kāi)發(fā)自己的版本。在 3GPP的 3G系統(tǒng)之外,也被叫做進(jìn)化的通 用無(wú)線電臺(tái)訪問(wèn)（進(jìn)化UTRA）,也被廣泛稱為L(zhǎng)TE（長(zhǎng)期演進(jìn)）,或被稱為3GPP版本 的UMB超移動(dòng)寬帶）如圖1.1。應(yīng)當(dāng)指出的是，這三個(gè)3G系統(tǒng)即超越移動(dòng) Wi,LET,IMT-2000要求的UMB滿足,因此它們可以滿足IMT-2000標(biāo)準(zhǔn)。圖 1.1 蜂窩系統(tǒng)演化。表 1.1 LTE 系統(tǒng)的屬性。1.2 長(zhǎng)期演進(jìn) （LTE）LTE 的目標(biāo)是提供一個(gè)高數(shù)據(jù)速率 , 低延遲技術(shù)支持和分組優(yōu)化的無(wú)線接 入技術(shù),并支持靈活的帶寬部署。與此同時(shí) ,新的網(wǎng)絡(luò)架構(gòu)

8、的設(shè)計(jì)目標(biāo)是 , 支持與 分組交換通信的無(wú)縫移動(dòng)性 , 優(yōu)質(zhì)的服務(wù)服和最低限度的延遲。空中接口相關(guān)的屬性總結(jié)在表1.1中。系統(tǒng)支持靈活的帶寬OFDMA和SC-FDMA勺訪問(wèn)，此外,FDD（頻分雙工）和TDD時(shí)分雙工）,半雙工FDD支持低成本 的UE不像軟驅(qū),它在半雙工FDD在同一時(shí)間內(nèi)操作的問(wèn)題上是不需要發(fā)送和接 收的,這樣就避免了為UE而需要的昂貴的雙工器。該系統(tǒng)主要是優(yōu)化低轉(zhuǎn)速可達(dá) 15公里/小時(shí)。然而,系統(tǒng)規(guī)范允許一些性能下降超過(guò) 350公里/ 小時(shí)的流動(dòng)性 支持。基于單載波頻分多址的接入（SC-FDMA）由于低峰均值功率比（PAPR）相對(duì)的 OFDM上行接入，因此要增加上行覆蓋。該系統(tǒng)

9、支持4X 4 MIMO侈輸入多輸出）在20 MHz帶寬326 Mb / s的下行 峰值數(shù)據(jù)傳輸速率。由于上行MIMO未受聘在首次發(fā)布的LTE標(biāo)準(zhǔn),因此上行峰值 數(shù)據(jù)傳輸速率被限制在 86 Mb / s 的 20兆赫帶寬。除了峰值數(shù)據(jù)傳輸速率的改 善外丄TE系統(tǒng)提供兩到四倍較高的細(xì)胞相對(duì)推出 6 HSPA系統(tǒng)的頻譜效率。在小 區(qū)邊緣的吞吐量為HSPA勺部署，同時(shí)保持同一站點(diǎn)的位置觀察到類似的改進(jìn)。在 延遲方面丄TE無(wú)線接口和網(wǎng)絡(luò)提供了一個(gè)數(shù)據(jù)包從網(wǎng)絡(luò)到UE的傳輸延遲小于10毫秒的能力。1.3 演進(jìn)到 4G移動(dòng)Wi和UMB6線電接口屬性表和表1.1給出的LTE屬性表是非常相似。 這三個(gè)系統(tǒng)都是支持

10、靈活的帶寬,下行的OFDM和MIMS案,FDD / TDD的雙工。 有如一些分歧,就是在LTE上行SC-FDMA勺基于OFDM技術(shù)在移動(dòng) Wi和UMBt。三個(gè)系統(tǒng)的性能有所不同 , 因此預(yù)計(jì)將有微小的差別。類似于IMT-2000的主動(dòng)性，ITU-R 的5D工作組指出的IMT-Advaneed系 統(tǒng)的要求。其中 ,這些要求包括平均下行 100 Mbit / s 的廣域網(wǎng)數(shù)據(jù)傳輸速率 , 最高可達(dá) 1 Gbit / s 的本地訪問(wèn)和低流動(dòng)性的情景。此外 , 在世界無(wú)線電通信大 會(huì)上(WRC-2007),最大的428兆赫的新頻譜被確定為IMT系統(tǒng)，其中還包括一個(gè)在 全球性的基礎(chǔ)上分配 136 兆赫的

11、頻譜。3GPP和IEEE 802 LMSC正在積極發(fā)展自己的標(biāo)準(zhǔn),以提交IMT-Advaneed 為目標(biāo)丄TE和IEEE802.16的標(biāo)準(zhǔn)是要進(jìn)一步提高系統(tǒng)的頻譜效率和數(shù)據(jù)傳輸速 率,同時(shí)支持各自的早期版本的向后兼容性。其中幾個(gè)增強(qiáng) ,包括支持一個(gè)大于 20 MHz的帶寬和較高階 MIMO的LTE-Advaneed和IEEE 802.16標(biāo)準(zhǔn)發(fā)展的一部 分, 目前正在討論中 , 以滿足 IMT-Advaneed 的要求。2 網(wǎng)絡(luò)架構(gòu)和協(xié)議LTE的網(wǎng)絡(luò)結(jié)構(gòu)設(shè)計(jì)與無(wú)縫移動(dòng)性，質(zhì)量和服務(wù)質(zhì)量(QoS)的最小延遲支 持分組交換流量的目標(biāo)。分組交換的方式,允許所有服務(wù),包括對(duì)語(yǔ)音通過(guò)數(shù)據(jù)包 連接的支持。

12、結(jié)果一個(gè)高度簡(jiǎn)化的平坦架構(gòu)只有兩個(gè)節(jié)點(diǎn)，即演變節(jié)點(diǎn)B(ENB)和 移動(dòng)性管理實(shí)體/網(wǎng)關(guān)(MME毛重)。相反的，在目前的3G系統(tǒng)的分層網(wǎng)絡(luò)架構(gòu)有 更多的網(wǎng)絡(luò)節(jié)點(diǎn)。一個(gè)重大變化是，從數(shù)據(jù)路徑和無(wú)線網(wǎng)絡(luò)控制器(RNC)被淘汰， 到現(xiàn)在在ENB納入其職能。在單個(gè)節(jié)點(diǎn)接入網(wǎng)絡(luò)的好處是減少延遲和多個(gè)eNB到RNC勺處理負(fù)荷分布。消除在接入網(wǎng)絡(luò)的 RNC是可能的，一方面是因?yàn)長(zhǎng)TE系 統(tǒng)不支持宏多樣性或軟切換。在這一章中 , 我們討論了單播和廣播流量 ,QoS 架構(gòu)和接入網(wǎng)絡(luò)的移動(dòng)性管理的網(wǎng)絡(luò)體系結(jié)構(gòu)設(shè)計(jì)。此外我們還簡(jiǎn)要討論 2層結(jié)構(gòu)和不同的邏輯 ,運(yùn)輸和 物理信道 , 隨著它們的映射問(wèn)題。2.1 網(wǎng)絡(luò)架構(gòu)

13、所有的網(wǎng)絡(luò)接口都基于IP協(xié)議。通過(guò)S1接口的互連，如在圖2.1所示的 eNBs通過(guò)X2接口和 MME毛重實(shí)體。S1接口支持 MME勺/毛重和eNBs的1之 間的一對(duì)多的關(guān)系。eNB和MM之間的功能分割關(guān)系圖如圖 2.2所示。兩個(gè)實(shí)體的邏輯網(wǎng)關(guān)即 服務(wù)網(wǎng)關(guān)（GW和分組數(shù)據(jù)網(wǎng)網(wǎng)關(guān)（GW> S-GW乍為本地移動(dòng)錨轉(zhuǎn)發(fā)和接收數(shù)據(jù)包, 并服從ENB-UE的服務(wù)。與外部分組數(shù)據(jù)網(wǎng)絡(luò)（如In ternet）和IMS（PDNS的P-GW 的接口。在P-GW丕執(zhí)行了多個(gè)IP地址分配,執(zhí)行政策,包過(guò)濾和路由等功能。MME是一個(gè)信號(hào)的唯一實(shí)體,因此，用戶的IP數(shù)據(jù)包是不通過(guò)MME勺。一 個(gè)優(yōu)勢(shì)是一個(gè)單獨(dú)的網(wǎng)絡(luò)

14、實(shí)體的信令信號(hào)和交通網(wǎng)絡(luò)容量可以獨(dú)立成長(zhǎng)。MME的主要職能是包括控制和執(zhí)行尋呼轉(zhuǎn)播的空閑模式UE的可達(dá)性，跟蹤區(qū)列表管理,漫游,認(rèn)證,授權(quán),P-GW/S-GW選擇,承載管理,包括專用的承載建立,安全談判 NAS信令等。進(jìn)化節(jié)點(diǎn)B實(shí)現(xiàn)節(jié)點(diǎn)B的功能,以及傳統(tǒng)上RNC中實(shí)現(xiàn)的協(xié)議。eNB的主 要功能是報(bào)頭壓縮 , 加密和數(shù)據(jù)包的可靠傳遞。在控制方面 ,ENB 采用 , 如 admissioncontrol 和無(wú)線資源管理的職能。在單個(gè)節(jié)點(diǎn)接入網(wǎng)絡(luò)的好處是減少 延遲和RNC勺處理負(fù)載分布到多個(gè)eNB圖 2.1 網(wǎng)絡(luò)架構(gòu)。圖2.2eNB和MME毛重之間的功能分割線鏈路控制（RLC）傳統(tǒng)RNC勺網(wǎng)絡(luò)側(cè)終止

15、層圖 2.3 用戶平面協(xié)議。附件 2: 外文原文 （ 復(fù)印件 ）Introducing WPFThe cellular wireless communications industry witnessed tremendous growth in the past decade with over four billion wireless subscribers worldwide. The first generation 1G analog cellular systems supported voice communication with limited roaming. The s

16、econd generation 2G digital systems promised higher capacity and better voice quality than did their analog counterparts. Moreover, roaming became more prevalent thanks to fewer standards and common spectrum allocations across countries particularly in Europe. The two widely deployed second-generati

17、on 2G cellular systems are GSM global system for mobile communications and CDMA code division multiple access. As for the 1G analog systems, 2G systems were primarily designed to support voice communication. H In later releases of these standards, capabilities were introduced to support data transmi

18、ssion. However, the data rates were generally lower than that supported by dial-up connections. The ITU-Rinitiativeon IMT-2000 internationalmobile telecommunications 2000paved the way for evolution to 3G. A set of requirements such as a peakdata rate of 2 Mb/s and support for vehicular mobility were

19、 published under IMT-2000 initiative. Both the GSMand CDMAcampsformed their ownseparate 3G partnership projects 3GPPand 3GPP2,respectively to develop IMT-2000 compliant standards based on the CDMAtechnology. The 3G standard in 3GPP is referred to as wideband CDMA WCDMA because it uses a larger 5 MHz

20、 bandwidth relative to 1.25 MHzbandwidth used in 3GPP2's cdma2000system. The 3GPP2 also developed a 5 MHz version supporting three 1.25 MHz subcarriers referred to as cdma2000-3x. In order to differentiate from the 5 MHz cdma2000-3x standard, the 1.25 MHz system is referred to as cdma2000-1x or

21、simply 3G-1x.The first release of the 3G standards did not fulfill its promiseof high-speed data transmissions as the data rates supported in practice were much lower than that claimed in the standards. A serious effort was then madeto enhance the 3Gsystems for efficient data support. The 3GPP2 firs

22、t introduced the HRPD high rate packet data 1 system that used various advanced techniques optimized for data traffic such as channel sensitive scheduling, fast link adaptation and hybrid ARQ,etc. The HRPD system required a separate 1.25 MHzcarrier and supported no voice service. This was the reason

23、 that HRPDwas initially referred to as cdma2000-1xEVDO evolution data only system. The 3GPP followed a similar path andintroduced HSPA high speed packet access 2 enhancement to the WCDMA system. The HSPA standard reused many of the same data-optimized techniques as the HRPD system. A difference rela

24、tive to HRPD, however, is that both voice and data can be carried on the same 5 MHz carrier in HSPA.In parallel to HRPD,3GPP2also developed a joint voice data standard that was referred to as cdma2000-1xEVDV evolution data voice 3. Like HSPA,the cdma2000-1xEVDVsystem supported both voice and data on

25、 the same carrier but it was never commercialized. In the later release of HRPD, VoIP Voice over Internet Protocol capabilities were introduced to provide both voice and data service on the same carrier. The two 3G standards namely HSPAand HRPDwere finally able to fulfill the 3G promise and have bee

26、n widely deployed in major cellular markets to provide wireless data access.1.1 Beyond 3G systemsWhile HSPAand HRPDsystems were being developed and deployed, IEEE 802 LMSCLAN/MANStandard Committee introduced the IEEE 802.16e standard 4 for mobile broadband wireless access. This standard was introduc

27、ed as an enhancement to an earlier IEEE 802.16 standard for fixed broadband wireless access. The 802.16e standard employed a different access technology namedOFDMAorthogonal frequency division multiple access and claimed better data rates and spectral efficiency than that provided by HSPAand HRPD.Al

28、though the IEEE 802.16 family of standards is officiallycalled WirelessMAN in IEEE, it has been dubbed Wi worldwide interoperability for microwave access by an industry group named the Wi Forum. The mission of the Wi Forum is to promote and certify the compatibility and interoperability of broadband

29、 wireless access products. The Wi system supporting mobility as in IEEE 802.16e standard is referred to as Mobile Wi. In addition to the radio technology advantage, Mobile Wi also employed a simpler network architecture based on IP protocols The introduction of Mobile Wi led both 3GPP and 3GPP2 to d

30、evelop their own version of beyond 3G systems based on the OFDMA technology and network architecture similar to that in Mobile Wi. The beyond 3G system in 3GPP is called evolved universal terrestrial radio access evolved UTRA5 and is also widely referred to as LTE Long-Term Evolution while 3GPP2 

31、9;sversion is called UMB ultra mobile broadband 6 as depicted in Figure 1.1. It should be noted that all three beyond 3G systems namely Mobile Wi, LTE and UMB meet IMT-2000 requirements and hence they are alsoFigure 1.1. Cellular systems evolution.Table 1.1. LTE system attributes.part of IMT-2000 fa

32、mily of standards.1.2 Long-Term Evolution LTEThe goal of LTE is to provide a high-data-rate, low-latency and packet-optimized radio-access technology supporting flexible bandwidth deployments 7. In parallel, new network architecture is designed with the goal to support packet-switched traffic with s

33、eamless mobility, quality of service and minimal latency 8 The air-interface related attributes of the LTE system are summarized in Table 1.1. The system supports flexible bandwidths thanks to OFDMAand SC-FDMAaccess schemes. In addition to FDD frequency division duplexing and TDD time division duple

34、xing, half-duplex FDDis allowed to support low cost UEs. Unlike FDD, in half-duplex FDDoperation a UEis not required to transmit and receive at the same time. This avoids the need for a costly duplexer in the UE.The system is primarily optimized for low speeds up to 15 km/h. However, the system spec

35、ifications allow mobility support in excess of 350 km/h with some performance degradation. The uplink access is based on single carrier frequency division multiple access SC-FDMA that promises increased uplink coverage due to low peak-to-average power ratio PAPR relative to OFDMA.The system supports

36、 downlink peak data rates of 326 Mb/s with 4 x4 MIMO multiple input multiple output within 20 MHz bandwidth. Since uplink MIMOis not employed in the first release of the LTE standard, the uplink peak data rates are limited to 86 Mb/s within 20 MHz bandwidth.In addition to peak data rate improvements

37、, the LTE system provides two to four times higher cell spectral efficiency relative to the Release 6 HSPA system. Similar improvements are observed in cell-edge throughput while maintaining same-site locations as deployed for HSPA. In terms of latency, the LTE radio-interface and network provides c

38、apabilities for less than 10 ms latency for the transmission of a packet from the network to the UE.1.3 Evolution to 4GThe radio-interface attributes for Mobile Wi and UMB are very similar to those of LTE given in Table 1.1. All three systems support flexible bandwidths, FDD/TDD duplexing, OFDMA in

39、the downlink and MIMO schemes. There are a few differences such as uplink in LTE is based on SC-FDMA compared to OFDMA in Mobile Wi and UMB. The performance of the three systems is therefore expected to be similar with small differences Similar to the IMT-2000 initiative, ITU-R Working Party 5D has

40、stated requirements for IMT-advanced systems. Amongothers, these requirements include average downlink data rates of 100 Mbit/s in the wide area network, and up to 1 Gbit/s for local access or low-mobility scenarios. Also, at the World Radiocommunication Conference 2007 WRC-2007, a imum of a 428 MHz

41、 new spectrum is identified for IMT systems that also include a 136 MHz spectrum allocated on a global basis.Both 3GPP and IEEE 802 LMSC are actively developing their own standards for submission to IMT-advanced. The goal for both LTE-advanced 9 and IEEE 802.16 m10 standards is to further enhance sy

42、stem spectral efficiency and data rates while supporting backward compatibility with their respective earlier releases. As part of the LTE-advanced and IEEE802.16 standards developments, several enhancements including support for a larger than 20 MHz bandwidth and higher-order MIMO are being discuss

43、ed to meet the IMT-advanced requirements.2 Network architecture and protocolsThe LTE network architecture is designed with the goal of supporting packet-switched traffic with seamless mobility, quality of service QoS and minimal latency. A packet-switched approach allows for the supporting of all se

44、rvices including voice through packet connections. The result in a highly simplified flatter architecture with only two types of node namely evolved Node-B eNBand mobility managemententity/gateway MME/GW. This is in contrast to manymore network nodes in the current hierarchical network architecture

45、of the 3G system. One major change is that the radio network controller RNCis eliminated from the data path and its functions are now incorporated in eNB. Someof the benefits of a single node in the access network are reduced latency and the distribution of the RNC processing load into multiple eNBs

46、. The elimination of the RNC in the access network was possible partly because the LTEsystem does not support macro-diversity or soft-handoff.In this chapter, we discuss network architecture designs for both unicast and broadcast traffic, QoS architecture and mobility management in the access networ

47、k. We also briefly discuss layer 2 structure and different logical, transport and physical channels along with theirmapping.2.1 Network architectureAll the network interfaces are based on IP protocols. The eNBs are interconnected by means of an X2 interface and to the MME/GW entity by meansof an S1

48、interface as shown in Figure 2.1. The S1 interface supports a many-to-many relationship between MME/GW and eNBs 1 Thefunctionalsplit between eNB and MME/GW is shownin Figure 2.2. Two logical gateway entities namely the serving gateway S-GW and the packet data network gateway P-GW are defined. The S-GW acts as a local mobilit