1、 5G 無線通信網(wǎng)絡(luò)中英文對照外文翻譯文獻(xiàn)5G 無線通信網(wǎng)絡(luò)中英文對照外文翻譯文獻(xiàn)(文檔含英文原文和中文翻譯) 5G 無線通信網(wǎng)絡(luò)中英文對照外文翻譯文獻(xiàn)翻譯：5G 無線通信網(wǎng)絡(luò)的蜂窩結(jié)構(gòu)和關(guān)鍵技術(shù)摘要第四代無線通信系統(tǒng)已經(jīng)或者即將在許多國家部署。然而，隨著無線移動設(shè)備和服務(wù)的激增，仍然有一些挑戰(zhàn)尤其是 4G 所不能容納的，例如像頻譜危機(jī)和高能量消耗。無線系統(tǒng)設(shè)計師們面臨著滿足新型無線應(yīng)用對高數(shù)據(jù)速率和機(jī)動性要求的持續(xù)性增長的需求，因此他們已經(jīng)開始研究被期望于 2020 年后就能部署的第五代無線系統(tǒng)。在這篇文章里面，我們提出一個有內(nèi)門和外門情景之分的潛在的蜂窩結(jié)構(gòu)，并且討論了多種可行性關(guān)于 5G

2、 無線通信系統(tǒng)的技術(shù)，比如大量的 MIMO 技術(shù)，節(jié)能通信，認(rèn)知的廣播網(wǎng)絡(luò)和可見光通信。面臨潛在技術(shù)的未知挑戰(zhàn)也被討論了。介紹信息通信技術(shù)（ICT）創(chuàng)新合理的使用對世界經(jīng)濟(jì)的提高變得越來越重要。無線通信網(wǎng)絡(luò)在全球 ICT 戰(zhàn)略中也許是最挑剔的元素，并且支撐著很多其他的行業(yè)，它是世界上成長最快最有活力的行業(yè)之一。歐洲移動天文臺（ EMO）報道 2010 年移動通信業(yè)總計稅收 1740 億歐元,從而超過了航空航天業(yè)和制藥業(yè)。無線技術(shù)的發(fā)展大大提高了人們在商業(yè)運(yùn)作和社交功能方面通信和生活的能力無線移動通信的顯著成就表現(xiàn)在技術(shù)創(chuàng)新的快速步伐。從 1991 年二代移動通信系統(tǒng)(2G)的初次登場到 200

3、1 年三代系統(tǒng)（3G）的首次起飛，無線移動網(wǎng)絡(luò)已經(jīng)實現(xiàn)了從一個純粹的技術(shù)系統(tǒng)到一個能承載大量多媒體內(nèi)容網(wǎng)絡(luò)的轉(zhuǎn)變。4G 無線系統(tǒng)被設(shè)計出來用來滿足 IMT-A 技術(shù)使用 IP 面向所有服務(wù)的需求。在 4G 系統(tǒng)中，先進(jìn)的無線接口被用于正交頻分復(fù)用技術(shù)（ OFDM），多輸入多輸出系統(tǒng)（MIMO）和鏈路自適應(yīng)技術(shù)。4G 無線網(wǎng)絡(luò)可支持?jǐn)?shù)據(jù)速率可達(dá) 1Gb/s 的低流度，比如流動局域無線訪問，還有速率高達(dá) 100M/s 的高流速，例如像移動訪問。LTE系統(tǒng)和它的延伸系統(tǒng) LTE-A，作為實用的 4G 系統(tǒng)已經(jīng)在全球于最近期或不久的將來部署。然而，每年仍然有戲劇性增長數(shù)量的用戶支持移動寬頻帶系統(tǒng)。越來

4、越多的 5G 無線通信網(wǎng)絡(luò)中英文對照外文翻譯文獻(xiàn)人渴望更快的網(wǎng)絡(luò)訪問速度，時髦的手機(jī)，總的來說就是更快地與他人通信或信息訪問。如今更多功能強(qiáng)大小巧的手機(jī)和便捷電腦可以滿足先進(jìn)的多媒體功能變得越來越受歡迎。這就造成了無線移動設(shè)備和服務(wù)的激增。EMO 指出自從 2006年起，移動寬頻每年有 92%的增長。無線世界研究論壇（WWRF）預(yù)言到 2017年會有七萬億的無線設(shè)備來服務(wù)七十億的人口；也就是說無線網(wǎng)絡(luò)連接設(shè)備的數(shù)量將會是世界人口數(shù)量的 1000 倍。隨著越來越多的設(shè)備無線化許多研究難題需要被解決。最重要的難題之一就是蜂窩通信中射頻光譜分配的物質(zhì)缺乏。蜂窩頻率把極高頻帶用于蜂窩手機(jī)，一般來講范圍

5、可從幾百兆赫茲到幾千兆赫茲。這些頻譜被嚴(yán)重的使用以至于對操作員更多的獲取造成困難。另一個難題就是先進(jìn)無線技術(shù)的部署面臨高能量消耗的費(fèi)用。無線通信系統(tǒng)中高能消耗的增長間接造成了二氧化碳排放量的增長，后者被視為當(dāng)前生態(tài)環(huán)境的主要威脅。此外，據(jù)手機(jī)運(yùn)營商反映基站的能源消耗貢獻(xiàn)了超過 70%的電力賬單。事實上，節(jié)能通信并不是 4G無線系統(tǒng)中的最初需求之一，但是它在之后的舞臺上被作為問題所提及。其他的難題，例如平均頻譜效率、高傳輸率和高遷移率、無縫覆蓋、多樣化的服務(wù)質(zhì)量請求以及分散的用戶體驗（不同無線設(shè)備/接口的不兼容和異構(gòu)網(wǎng)絡(luò)），僅僅提及一點點。以上所有問題正給手機(jī)服務(wù)提供商帶來更多壓力，他們正面臨著

6、有更高傳輸率、更大的網(wǎng)絡(luò)容量、更高的頻譜效率、更高的能源利用率和更高的利用率規(guī)定的新型無線應(yīng)用的持續(xù)增長需求。另一方面，在當(dāng)前的技術(shù)條件下，4G 網(wǎng)絡(luò)在傳輸率方面幾乎已經(jīng)達(dá)到了理論上的限制，因此并不能充分的解決以上難題。從這層意義上來說，我們需要開創(chuàng)性的無線技術(shù)來解決以上由數(shù)萬億無線設(shè)備造成的問題，并且研究員們已經(jīng)著手研究超4G（B4G）或者5G 無線技術(shù)。中英科學(xué)橋工程：B4G 無線移動通信(http:/www.ukchinab4g. ac.uk/)可能是世界上著手 B4G研究的首批項目之一，其中的一些潛在的 B4G 技術(shù)已經(jīng)被確定了。歐洲和中國也 已 經(jīng) 開 始 了 一 些 5G 項 目

7、， 比 如 由 歐 盟 支 持 的 METIS2020(https:/www.metis2020. com/)和由中國科學(xué)院支持的在 5G 方面的國家 863重點工程。諾基亞西門子通信公司描述通過對比 2010 年的通信水準(zhǔn)今后十年潛在的無線接入技術(shù)可以被進(jìn)一步開發(fā)用來支持多大超過一千倍的通信量。三星公 5G 無線通信網(wǎng)絡(luò)中英文對照外文翻譯文獻(xiàn)司展示了一個運(yùn)用微波技術(shù)使傳輸率在兩千米的范圍內(nèi)超過 1Gb/s 的無線系統(tǒng)。5G 網(wǎng)絡(luò)，預(yù)期大約在 2020 年被標(biāo)準(zhǔn)化，究竟是什么呢？由于現(xiàn)在太早以至于不能確切地定義。廣泛的認(rèn)同是與 4G 網(wǎng)絡(luò)相比，5G 網(wǎng)絡(luò)應(yīng)該達(dá)到 1000 倍的系統(tǒng)容量，10

8、倍的頻譜利用率、能源利用率和傳輸率（低流動性下最高傳輸率為 10Gb/s，高流動性下最高傳輸率為 1Gb/s）還有 25 倍平均系統(tǒng)吞吐量。5G 網(wǎng)絡(luò)的目標(biāo)在于連接整個世界以及實現(xiàn)任何人之間（人與人），任何事物之間（人與機(jī)器，機(jī)器與機(jī)器）的無縫的、無處不在的通信，無論他們在哪，無論他們什么時候需要，也無論他們用什么電子設(shè)備/服務(wù)/網(wǎng)絡(luò)。這就意味著 5G 網(wǎng)絡(luò)應(yīng)該能夠支持一些 4G 網(wǎng)絡(luò)所不能支持的特殊情況（例如乘坐高鐵的用戶）。高鐵車速可輕松達(dá)到 350 到 500km/h，然后 4G 網(wǎng)絡(luò)所能支持通信的情況是 250km/h。本篇文章中，我們提出了一個潛在的5G 蜂窩結(jié)構(gòu)并且討論有希望的技術(shù)

9、用來部署以便滿足 5G 的需求。這篇文章剩下的安排如下。我們提出了一個潛在的 5G 蜂窩結(jié)構(gòu)。我們描述一些可行性的關(guān)鍵技術(shù)可以被 5G 系統(tǒng)采用。未來的挑戰(zhàn)是顯著的，最終我們會得出結(jié)論。潛在的 5G 無線蜂窩結(jié)構(gòu)為了解決以上難題并且滿足 5G 系統(tǒng)的需求，我們需要在蜂窩結(jié)構(gòu)的設(shè)計上做個戲劇性的改變。我們知道無線用戶 80%的時間都是待在戶內(nèi)，待在戶外的僅僅約有 20%。當(dāng)前常見的蜂窩結(jié)構(gòu)通常是為移動用戶在蜂窩通信中間建立一個露天基站，這樣就不用管他們實在戶內(nèi)還是戶外。對于戶內(nèi)用戶與戶外基站間的通信，信號不得不穿過建筑墻，造成很高的穿透損耗，從而顯著損傷無線傳輸?shù)膫鬏斔俾省㈩l譜利用率、能源利用率

10、。設(shè)計 5G 蜂窩結(jié)構(gòu)的中心思想就是分開戶內(nèi)和戶外的情況這樣穿透損耗經(jīng)過建筑墻后可以在某種意義上來說避免掉。這些將會由分布式天線系統(tǒng)（DAS）和大量的 MIMO 技術(shù)來實現(xiàn),即在地面上部署由幾十個或幾百個天線單組成的分布式天線陣。然而目前最主流的 MIMO 系統(tǒng)使用兩個或四個天線，大量使用 MIMO系統(tǒng)的目的是為了開發(fā)盡可能大的容量效益以提升更大的天線陣。戶外基站將會裝備由一些天線單元（也有大陣列天線）組成的大陣列天線，這些大陣列天線分布在覆蓋區(qū)周圍，通過光纖連接基站，從而從DAS 和大量的 MIMO 技術(shù)中都能 5G 無線通信網(wǎng)絡(luò)中英文對照外文翻譯文獻(xiàn)受益。戶外手機(jī)用戶通常配備有限數(shù)量的天線

11、單元，但是他們可以通過互相合作形成一個虛擬的大陣列天線，連同基站天線陣將會構(gòu)造虛擬的大規(guī)模 MIMO 鏈接群。大陣列天線也將被安裝在每個建筑的外面以便與戶外基站群或者擁有分布式天線單元的基站群相互通信，與可見組件通信也是有可能的。大陣列天線用電纜連接到能與戶內(nèi)用戶之間通信的建筑內(nèi)部的無線接入點。這樣必定會在短時間內(nèi)提高基礎(chǔ)設(shè)備的花費(fèi)最終顯著提升覆蓋區(qū)平均生產(chǎn)力，頻譜效率，能源效率還有蜂窩系統(tǒng)傳輸率。采用這樣的蜂窩結(jié)構(gòu)，戶內(nèi)用戶僅需要使用安裝在戶外建筑的大陣列天線便可與戶內(nèi)無線接入點通信，很多的技術(shù)可以被利用以便適用高數(shù)據(jù)速率進(jìn)行的短程通信。舉一些例子包括 WiFi，毫微微蜂窩，超寬頻（UWB）

12、，毫米波通信（3300GHz），還有可見光通信(VLC)（400490THz）。值得說明的是毫米波和 VLC 技術(shù)使用更高的頻率并不適用傳統(tǒng)的蜂窩通信。這些高頻波并不能很好地穿透固體材料并且很容易就會被氣體，雨水還有植物吸收或分散。因此，很難將這些波用于戶外和遠(yuǎn)距離應(yīng)用。然而，隨著寬頻帶的實現(xiàn)，毫米波和 VLC 技術(shù)可以大大提高在戶內(nèi)情況下的數(shù)據(jù)傳輸速率。為了解決頻譜缺乏問題，并且找到新的不為傳統(tǒng)無線服務(wù)（例如毫米波通信和 VLC）所用的頻帶，我們可以盡力提高現(xiàn)有無線頻譜的頻譜利用率，比如取道認(rèn)識的無線網(wǎng)絡(luò)。5G 蜂窩結(jié)構(gòu)同樣應(yīng)該是一種有宏蜂窩，微蜂窩，小基站和繼電器組成的混雜結(jié)構(gòu)。為了適應(yīng)高

13、機(jī)動性用戶比如乘車和乘高鐵的用戶，我們已經(jīng)提出了超小型移動基站的概念，即結(jié)合移動中繼和超小型基站的概念。超小型移動基站位于車輛內(nèi)部可以和位于車內(nèi)的用戶通信，而大陣列天線位于車輛外面和戶外的基站通信。一個超小型移動基站和它關(guān)聯(lián)的用戶都被基站看作一個單元。從用戶的角度來看，超小型移動基站被看作正式的基站。這和上面區(qū)分戶內(nèi)（車輛內(nèi)部）和戶外情況的觀點非常相似。已經(jīng)能表明的是用戶使用超小型移動基站 在享受高數(shù)據(jù)速率的服務(wù)的同時減少信令開銷。以上提出的 5G 混雜蜂窩結(jié)構(gòu)在圖 1 闡明。有前景的 5G 無線網(wǎng)絡(luò)的關(guān)鍵技術(shù)在這一部分，基于以上提出的混雜式蜂窩結(jié)構(gòu)，我們討論了一些有前景的無線網(wǎng)絡(luò)關(guān)鍵技術(shù)使之

14、能夠滿足 5G 無線網(wǎng)絡(luò)的性能要求。發(fā)展這些技術(shù)的目的是通過有效利用所有可能的資源以適應(yīng)戲劇性的容量增長。基于著名的香農(nóng)定理，系統(tǒng)的總?cè)萘緾 可以近似的表示為sum 5G 無線通信網(wǎng)絡(luò)中英文對照外文翻譯文獻(xiàn) PiNC sumB log 1（1）2i網(wǎng)路 通道p其中 B 是第 i 條信道的帶寬， P 是第 i 條信道的信號功率， N 表示噪聲功ipi率。從公式 1 可以看出系統(tǒng)總?cè)萘緾 等于所有子通道和網(wǎng)路容量之和。為了增加sumC，我們可以提高網(wǎng)絡(luò)覆蓋范圍（通過使用含有宏蜂窩，微蜂窩，小基站，繼sum電器，超小型移動基站的網(wǎng)絡(luò)），子通道的數(shù)量（通過使用大量的 MIMO 技術(shù)，空間調(diào)整，協(xié)作式

15、MIMO，DAS,管理干涉等等），帶寬（通過 CR 網(wǎng)絡(luò)，毫米波通信，VLC，多標(biāo)準(zhǔn)系統(tǒng)等等）還有功率（能源利用率和綠色通信）。在下文中，我們重點聚焦于一些關(guān)鍵技術(shù)。 5G 無線通信網(wǎng)絡(luò)中英文對照外文翻譯文獻(xiàn)外文原文：ABSTRACTThe fourth generation wireless communica-tion systems have been deployed or are soon tobe deployed in many countries. However, withan explosion of wireless mobile devices and ser-vice

16、s, there are still some challenges that cannotbe accommodated even by 4G, such as the spec-trum crisis and high energy consumption. Wire-less system designers have been facing thecontinuously increasing demand for high datarates and mobility required by new wirelessapplications and therefore have st

17、arted researchon fifth generation wireless systems that areexpected to be deployed beyond 2020. In thisarticle, we propose a potential cellular architec-ture that separates indoor and outdoor scenar-ios, and discuss various promising technologiesfor 5G wireless communication systems, such asmassive

18、MIMO, energy-efficient communica-tions, cognitive radio networks, and visible light 5G 無線通信網(wǎng)絡(luò)中英文對照外文翻譯文獻(xiàn)communications. Future challenges facing thesepotential technologies are also discussed.INTRODUCTIONThe innovative and effective use of informationand communication technologies (ICT) isbecoming i

19、ncreasingly important to improve theeconomy of the world 1. Wireless communica-tion networks are perhaps the most critical ele-ment in the global ICT strategy, underpinningmany other industries. It is one of the fastestgrowing and most dynamic sectors in the world.The European Mobile Observatory (EM

20、O)reported that the mobile communication sectorhad total revenue of 174 billion in 2010, there-by bypassing the aerospace and pharmaceuticalsectors 2. The development of wireless tech-nologies has greatly improved peoples ability tocommunicate and live in both business opera-tions and social functio

21、ns.The phenomenal success of wireless mobilecommunications is mirrored by a rapid pace oftechnology innovation. From the second genera- 5G 無線通信網(wǎng)絡(luò)中英文對照外文翻譯文獻(xiàn)tion (2G) mobile communication system debutedin 1991 to the 3G system first launched in 2001,the wireless mobile network has transformedfrom a p

22、ure telephony system to a network thatcan transport rich multimedia contents. The 4Gwireless systems were designed to fulfill therequirements of International Mobile Telecom-munications-Advanced (IMT-A) using IP for allservices 3. In 4G systems, an advanced radiointerface is used with orthogonal fre

23、quency-divi-sion multiplexing (OFDM), multiple-input multi-ple-output (MIMO), and link adaptationtechnologies. 4G wireless networks can supportdata rates of up to 1 Gb/s for low mobility, suchas nomadic/local wireless access, and up to 100Mb/s for high mobility, such as mobile access.Long-Term Evolu

24、tion (LTE) and its extension,LTE-Advanced systems, as practical 4G systems,have recently been deployed or soon will bedeployed around the globe.However, there is still a dramatic increase inthe number of users who subscribe to mobile 5G 無線通信網(wǎng)絡(luò)中英文對照外文翻譯文獻(xiàn)broadband systems every year. More and morepeo

25、ple cravefaster Internet access on the move,trendier mobiles, and, in general, instant com-munication with others or access to information.More powerful smartphones and laptops arebecoming more popular nowadays, demandingadvanced multimedia capabilities. This hasresulted in an explosion of wireless

26、mobiledevices and services. The EMO pointed out thatthere has been a 92 percent growth in mobilebroadband per year since 2006 2. It has beenpredicted by the Wireless World ResearchForum (WWRF) that 7 trillion wireless deviceswill serve 7 billion people by 2017; that is, thenumber of network-connecte

27、d wireless deviceswill reach 1000 times the worlds population 4.As more and more devices go wireless, manyresearch challenges need to be addressed.One of the most crucial challenges is thephysical scarcity of radio frequency (RF) spectraallocated for cellular communications. Cellularfrequencies use

28、ultra-high-frequency bands for 5G 無線通信網(wǎng)絡(luò)中英文對照外文翻譯文獻(xiàn)cellular phones, normally ranging from severalhundred megahertz to several gigahertz. Thesefrequency spectra have been used heavily, mak-ing it difficult for operators to acquire more.Another challenge is that the deployment ofadvanced wireless tech

29、nologies comes at the costof high energy consumption. The increase ofenergy consumption in wireless communicationsystems causes an increase of CO 2 emission indi-rectly, which currently is considered as a majorthreat for the environment. Moreover, it hasbeen reported by cellular operators that theen

30、ergy consumption of base stations (BSs) con-tributes to over 70 percent of their electricity bill5. In fact, energy-efficient communication wasnot one of the initial requirements in 4G wire-less systems, but it came up as an issue at a laterstage. Other challenges are, for example, aver-age spectral

31、 efficiency, high data rate and highmobility, seamless coverage, diverse quality ofservice (QoS) requirements, and fragmenteduser experience (incompatibility of different 5G 無線通信網(wǎng)絡(luò)中英文對照外文翻譯文獻(xiàn)wireless devices/interfaces and heterogeneousnetworks), to mention only a few.All the above issues are puttin

32、g more pres-sure on cellular service providers, who are facingcontinuously increasing demand for higher datarates, larger network capacity, higher spectralefficiency, higher energy efficiency, and highermobility required by new wireless applications.On the other hand, 4G networks have just aboutreac

33、hed the theoretical limit on the data ratewith current technologies and therefore are notsufficient to accommodate the above challenges.In this sense, we need groundbreaking wirelesstechnologies to solve the above problems causedby trillions of wireless devices, and researchershave already started t

34、o investigate beyond 4G(B4G) or 5G wireless techniques. The projectUK-China Science Bridges: (B)4G Wireless MobileCommunications (http:/www.ukchinab4g. ac.uk/) isperhaps one of the first projects in the world tostart B4G research, where some potential B4Gtechnologies were identified. Europe and Chin

35、a 5G 無線通信網(wǎng)絡(luò)中英文對照外文翻譯文獻(xiàn)have also initiated some 5G projects, such asMETIS 2020 (https:/www.metis2020. com/) sup-ported by EU and National 863 Key Project in5G supported by the Ministry of Science andTechnology (MOST) in China. Nokia SiemensNetworksdescribed how the underlying radioaccess technologies

36、 can be developed further tosupport up to 1000 times higher traffic volumescompared to 2010 travel levels over the next 10years 6. Samsung demonstrated a wireless sys-tem using millimeter (mm) wave technologieswith data rates faster than 1 Gb/s over 2 km 7.What will the 5G network, which is expected

37、to be standardized around 2020, look like? It isnow too early to define this with any certainty.However, it is widely agreed that compared tothe 4G network, the 5G network should achieve1000 times the system capacity, 10 times thespectral efficiency, energy efficiency and datarate (i.e., peak data r

38、ate of 10 Gb/s for lowmobility and peak data rate of 1 Gb/s for highmobility), and 25 times the average cell through- 5G 無線通信網(wǎng)絡(luò)中英文對照外文翻譯文獻(xiàn)put. The aim is to connect the entire world, andachieve seamless and ubiquitous communica-tions between anybody (people to people), any-thing (people to machine,

39、machine to machine),wherever they are (anywhere), whenever theyneed (anytime), by whatever electronicdevices/services/networks they wish (anyhow).This means that 5G networks should be able tosupport communications for some special sce-narios not supported by 4G networks (e.g., forhigh-speed train us

40、ers). High-speed trains caneasily reach 350 up to 500 km/h, while 4G net-works can only support communication scenariosup to 250 km/h. In this article, we propose apotential 5G cellular architecture and discusssome promising technologies that can bedeployed to deliver the 5G requirements.The remaind

41、er of this article is organized asfollows. We propose a potential 5G cellulararchitecture. We describe some promising keytechnologies that can be adopted in the 5G sys-tem. Future challenges are highlighted. Finally, 5G 無線通信網(wǎng)絡(luò)中英文對照外文翻譯文獻(xiàn)conclusions are drawn.A POTENTIAL 5G WIRELESSCELLULAR ARCHITECT

42、URETo address the above challenges and meet the5G system requirements, we need a dramaticchange in the design of cellular architecture. Weknow that wireless users stay indoors for about80 percent of time, while only stay ourdoorsabout 20 percent of the time 8. The currentconventional cellular archit

43、ecture normally usesan outdoor BS in the middle of a cell communi-cating with mobile users, no matter whether theystay indoors or outdoors. For indoor users com-municating with the outdoor BS, the signals haveto go through building walls, and this causes veryhigh penetration loss, which significantl

44、y dam-ages the data rate, spectral efficiency, and ener-gy efficiency of wireless transmissions.One of the key ideas of designing the 5G cel-lular architecture is to separate outdoor andindoor scenarios so that penetration loss throughbuilding walls can somehow be avoided. This will 5G 無線通信網(wǎng)絡(luò)中英文對照外文

45、翻譯文獻(xiàn)be assisted by distributed antenna system (DAS)and massive MIMO technology 9, where geo-graphically distributed antenna arrays with tensor hundreds of antenna elements are deployed.While most current MIMO systems utilize twoto four antennas, the goal of massive MIMO systems is toexploit the pote

46、ntially large capacitygains that would arise in larger arrays of anten-nas. Outdoor BSs will be equipped with largeantenna arrays with some antenna elements (alsolarge antenna arrays) distributed around the celland connected to the BS via optical fibers, bene-fiting from both DAS and massive MIMO te

47、ch-nologies. Outdoor mobile users are normallyequipped with limited numbers of antenna ele-ments, but they can collaborate with each otherto form a virtual large antenna array, whichtogether with BS antenna arrays will constructvirtual massive MIMO links. Large antennaarrays will also be installed o

48、utside of everybuilding to communicate with outdoor BSs ordistributed antenna elements of BSs, possibly 5G 無線通信網(wǎng)絡(luò)中英文對照外文翻譯文獻(xiàn)with line of sight (LoS) components. Large anten-na arrays have cables connected to the wirelessaccess points inside the building communicatingwith indoor users. This will cert

49、ainly increase theinfrastructure cost in the short term while signifi-cantly improving the cell average throughput,spectral efficiency, energy efficiency, and datarate of the cellular system in the long run.Using such a cellular architecture, as indoorusers only need to communicate with indoorwirele

50、ss access points (not outdoor BSs) withlarge antenna arrays installed outside build-ings, many technologies can be utilized that aresuitable for short-range communications withhigh data rates. Some examples include WiFi,femtocell, ultra wideband (UWB), mm-wavecommunications (3300 GHz) 7, and visible

51、light communications (VLC) (400490 THz)10. It is worth mentioning that mm-wave andVLC technologies use higher frequencies nottraditionally used for cellular communications.These high-frequency waves do not penetrate 5G 無線通信網(wǎng)絡(luò)中英文對照外文翻譯文獻(xiàn)solid materials very well and can readily beabsorbed or scattere

52、d by gases, rain, andfoliage. Therefore, it is hard to use these wavesfor outdoor and long distance applications.However, with large bandwidths available, mm-wave and VLC technologies can greatlyincrease the transmission data rate for indoorscenarios. To solve the spectrum scarcity prob-lem, besides

53、 finding new spectrum not tradi-tionally used for wireless services (e.g.,mm-wave communications and VLC), we canalso try to improve the spectrum utilization ofexisting radio spectra, for example, via cogni-tive radio (CR) networks 11.The 5G cellular architecture should also be aheterogeneous one, w

54、ith macrocells, microcells,small cells, and relays. To accommodate high-mobility users such as users in vehicles and high-speed trains, we have proposed the mobilefemtocell (MFemtocell) concept 12, whichcombines the concepts of mobile relay and fem-tocell. MFemtocells are located inside vehicles 5G 無線通信網(wǎng)絡(luò)中英文對照外文翻譯文獻(xiàn)to communicate with users within the vehicle,while large antenna arrays are locat