畢業(yè)論文外文翻譯---第三代cdma系統(tǒng)的仿真

1、<p>　　Simulation of Third Generation CDMA Systems</p><p><b>　　By</b></p><p>　　Fakhrul Alam</p><p><b>　　ABSTRACT</b></p><p>　　The goal for t

2、he next generation of mobile communications system is to seamlessly integrate a wide variety of communication services such as high speed data, video and multimedia traffic as well as voice signals. The technology needed

3、 to tackle the challenges to make these services available is popularly known as the Third Generation (3G) Cellular Systems. One of the most promising approaches to 3G is to combine a Wideband Code Division Multiple Acce

4、ss (WCDMA) air interface with the fixed networ</p><p><b>　　Chapter 1</b></p><p>　　Introduction</p><p>　　The goal for the next generation of mobile communications system

5、is to seamlessly provide a wide variety of communication services to anybody, anywhere, anytime. The intended service for next generation mobile phone users include services like transmitting high speed data, video and m

6、ultimedia traffic as well as voice signals. The technology needed to tackle the challenges to make these services available is popularly known as the Third Generation (3G) Cellular Systems. The first generation syst</

7、p><p>　　1.1 First Generation Cellular Systems</p><p>　　The first generation cellular systems generally employ analog Frequency Modulation</p><p>　　(FM) techniques. The Advanced Mobile

8、Phone System (AMPS) is the most notable of the first generation systems. AMPS was developed by the Bell Telephone System. It uses FM technology for voice transmission and digital signaling for control information. Other

9、first generation systems include:</p><p>　　· Narrowband AMPS (NAMPS)</p><p>　　· Total Access Cellular System (TACS)</p><p>　　· Nordic Mobile Telephone System (NMT-900

10、)</p><p>　　All the first generation cellular systems employ Frequency Division Multiple Access</p><p>　　(FDMA) with each channel assigned to a unique frequency band within a cluster of cells.<

11、;/p><p>　　1.2 Second Generation Cellular Systems</p><p>　　The rapid growth in the number of subscribers and the proliferation of many incompatible first generation systems were the main reason behi

12、nd the evolution towards second generation cellular systems. Second generation systems take the advantage of compression and coding techniques associated with digital technology. All the second generation systems employ

13、digital modulation schemes. Multiple access techniques like Time Division Multiple Access (TDMA) and Code Division Multiple Access (CDMA) are</p><p>　　??United States Digital Cellular (USDC) standards IS-54

14、and IS-136</p><p>　　??Global System for Mobile communications (GSM)</p><p>　　??Pacific Digital Cellular (PDC)</p><p><b>　　??cdmaOne</b></p><p>　　1.3 Third G

15、eneration Cellular Systems</p><p>　　Third generation cellular systems are being designed to support wideband services like high speed Internet access, video and high quality image transmission with the same

16、quality as the fixed networks. The primary requirements of the next generation cellular systems are:</p><p>　　??Voice quality comparable to Public Switched Telephone Network (PSTN).</p><p>　　??S

17、upport of high data rate. The following table shows the data rate requirement of</p><p>　　the 3G systems</p><p>　　Table 1.1: 3G Data Rate Requirements</p><p>　　??Support of both pac

18、ket-switched and circuit-switched data services.</p><p>　　??More efficient usage of the available radio spectrum</p><p>　　??Support of a wide variety of mobile equipment</p><p>　　??

19、Backward Compatibility with pre-existing networks and flexible introduction of</p><p>　　new services and technology</p><p>　　??An adaptive radio interface suited to the highly asymmetric nature

20、of most</p><p>　　Internet communications: a much greater bandwidth for the downlink than the uplink.</p><p>　　Research efforts have been underway for more than a decade to introduce multimedia&l

21、t;/p><p>　　capabilities into mobile communications. Different standard agencies and governing bodies are trying to integrate a wide variety of proposals for third generation cellular systems. The following figu

22、re, adopted from [1], shows the evolution of third generation cellular systems:</p><p>　　Figure 1.1: Evolution of 3G</p><p>　　References [2] and [3] provide further discussion on the evolution o

23、f third generation cellular Systems.</p><p>　　1.4. WCDMA: Air Interface for 3G</p><p>　　One of the most promising approaches to 3G is to combine a Wideband CDMA</p><p>　　(WCDMA) air

24、 interface with the fixed network of GSM. Several proposal supporting</p><p>　　WCDMA were submitted to the International Telecommunication Union (ITU) and its</p><p>　　International Mobile Telec

25、ommunications for the year 2000 (IMT2000) initiative for 3G.</p><p>　　Among several organizations trying to merge their various WCDMA proposals are</p><p>　　??Japan’s Association of Radio Indust

26、ry and Business (ARIB)</p><p>　　??Alliance for Telecommunications Industry Solutions (ATIS)</p><p><b>　　??T1P1</b></p><p>　　??European Telecommunications Standards Insti

27、tute (ETSI) through its Special</p><p>　　Mobile Group (SMG)</p><p>　　All these schemes try to take advantage of the WCDMA radio techniques without ignoring the numerous advantages of the already

28、 existing GSM networks. The standard that has emerged is based on ETSI’s Universal Mobile Telecommunication System (UMTS) and is commonly known as UMTS Terrestrial Radio Access (UTRA) [1]. The access scheme for UTRA is D

29、irect Sequence Code Division Multiple Access (DS-CDMA). The information is spread over a band of approximately 5 MHz. This wide bandwidth has given rise to</p><p>　　??Frequency Division Duplex (FDD)</p>

30、;<p>　　??Time Division Duplex (TDD)</p><p>　　Since different regions have different frequency allocation schemes, the capability to operate in either FDD or TDD mode allows for efficient utilization o

31、f the available spectrum. A brief definition of FDD and TDD modes is given next.</p><p>　　FDD: The uplink and downlink transmissions employ two separated frequency bands</p><p>　　for this duplex

32、 method. A pair of frequency bands with specified separation is assigned for a connection.</p><p>　　TDD: In this duplex method, uplink and downlink transmissions are carried over the</p><p>　　sa

33、me frequency band by using synchronized time intervals Thus time slots in a physical channel are divided into transmission and reception part.</p><p>　　We developed the simulator for a WCDMA system operating

34、 in the FDD mode. So all</p><p>　　the system description provided in chapter 2 holds for the FDD mode only.</p><p>　　1.4.1 WCDMA Key Features</p><p>　　The key operational features o

35、f the WCDMA radio interface are listed below [3], [4]:</p><p>　　??Support of high data rate transmission: 384 kbps with wide area coverage, 2</p><p>　　Mbps with local coverage.</p><p&

36、gt;　　??High service flexibility: support of multiple parallel variable rate services on</p><p>　　each connection.</p><p>　　??Both Frequency Division Duplex (FDD) and Time Division Duplex (TDD).&

37、lt;/p><p>　　??Built in support for future capacity and coverage enhancing technologies like</p><p>　　adaptive antennas, advanced receiver structures and transmitter diversity.</p><p>　

38、　??Support of inter frequency hand over and hand over to other systems,</p><p>　　including hand over to GSM.</p><p>　　??Efficient packet access.</p><p>　　1.4.2 WCDMA Key Technical C

39、haracteristics</p><p>　　The following table shows the key technical features of the WCDMA radio interface:</p><p>　　Table 1.2: WCDMA Key Technical Characteristics</p><p>　　The chip

40、rate may be extended to two or three times the standard 3.84 Mcps to</p><p>　　accommodate for data rates higher than 2 Mbps. The 200 kHz carrier raster has been chosen to facilitate coexistence and interoper

41、ability with GSM.</p><p><b>　　Chapter 5</b></p><p>　　Conclusion and Future Work</p><p>　　We implemented a signal simulator according to the physical layer specification

42、of the IMT-2000 WCDMA system. The data is transmitted in a frame by frame basis through a time varying channel. The transmitted signal is corrupted by multiple access interference. The signal is further corrupted by AWGN

43、 at the front end of the receiver. Simple rake diversity combining is employed at the receiver.</p><p>　　We investigated the bit error rate at both uplink and downlink for two different time</p><p

44、>　　varying channels. As expected the system is interference limited for higher number of users.We observed that without any channel coding schemes and antenna diversity techniques, the BER approaches to 10% as the sys

45、tem load goes beyond 50%. This is not an acceptable performance. However the BER can be pushed back to an acceptable limit with channel coding and antenna diversity techniques.</p><p>　　The developed simulat

46、or can be an invaluable tool to investigate the performance of a WCDMA under various conditions. As for example the simulator can be used to investigate antenna diversity schemes at the receiver. The simulator is very fl

47、exible</p><p>　　and one can very easily make the necessary modification to incorporate complex statistical channel model based on measurement and investigate the WCDMA performance under practical mobile chan

48、nel condition. We have shown that it is very simple to employ the simulator to observe the performance of error correction coding. We implemented a convolutional coding scheme for an uplink voice application of 9.6 kbps.

49、 It was observed that channel coding could significantly lower the required SNR for a par</p><p>　　The simulator employs a simple rake receiver to exploit the gain arising from temporal diversity. Spatial pr

50、operty of the multipath environment can be another source of diversity.Adaptive antennas are used at the receiver to take the advantage of this diversity gain. The simulator can be used to investigate the diversity gain

51、of different adaptive algorithms.Space-Time rake receivers [21], [22] or 2-D rake receivers [23] have been proposed to combine the temporal and spatial diversity at the rec</p><p>　　Turbo coding has been spe

52、cified for applications that require very low bit error rate.</p><p>　　Turbo coding schemes can be incorporated to the simulator in the same way we employed convolutional coding.</p><p>　　The si

53、mulator can be further improved by using statistical channel models based on</p><p>　　measured data. The improvement in system performance by using multi user detection and interference cancellation can also

54、 be investigated.</p><p>　　第三代CDMA系統(tǒng)的仿真</p><p>　　--Fakhrul Alam</p><p><b>　　摘要</b></p><p>　　下一代移動(dòng)通信系統(tǒng)的目標(biāo)是進(jìn)行無(wú)縫集成高速數(shù)據(jù)、視頻和多媒體以及聲音信號(hào)。需要解決的提供這些服務(wù)所面臨的挑戰(zhàn)的技術(shù)即為俗稱的第三

55、代（3g） 蜂窩系統(tǒng)。。3g 最有前途的途徑之一就是結(jié)合寬帶碼分多址(WCDMA) 空中接口與固定網(wǎng)絡(luò)的移動(dòng)通信的全球系統(tǒng)通信 (GSM)。在這篇論文中信號(hào)模擬器實(shí)施根據(jù)物理層的 imt-2000 WCDMA 系統(tǒng)的技術(shù)規(guī)范。數(shù)據(jù)的傳輸是基于時(shí)變信道的幀基礎(chǔ)。傳輸?shù)男盘?hào)的破壞是結(jié)構(gòu)化的方式生成的多址干擾而不是把它當(dāng)作加性高斯白噪聲 (AWGN)。信號(hào)被進(jìn)一步破壞在 AWGN接收器的前端。簡(jiǎn)單的分集信號(hào)的合并依靠接收器。我們調(diào)查不同信道條

56、件下的上行和下行通道誤碼率。顯示于改善錯(cuò)誤修正編碼方案性能。仿真器將發(fā)展成為進(jìn)行WCDMA通信系統(tǒng)設(shè)計(jì)與實(shí)現(xiàn)的非常有用的工具。</p><p><b>　　第 1 章</b></p><p><b>　　簡(jiǎn)介</b></p><p>　　下一代移動(dòng)通信系統(tǒng)的目標(biāo)是提供一個(gè)無(wú)縫的通信服務(wù)給任意人、任意時(shí)間與任意地點(diǎn)。預(yù)期下一

57、代移動(dòng)電話用戶服務(wù)包括像高速傳輸數(shù)據(jù)服務(wù)、 視頻和多媒體通信以及聲音信號(hào)。需要解決的提供這些服務(wù)所面臨的挑戰(zhàn)的技術(shù)俗稱第三代（3g） 蜂窩系統(tǒng)。第一代系統(tǒng)是為了傳輸語(yǔ)音應(yīng)用程序的模擬通信系統(tǒng)。隨后的數(shù)字通信被稱為第二代蜂窩系統(tǒng)。第三代系統(tǒng)與當(dāng)前二代標(biāo)準(zhǔn)相比，在應(yīng)用程序和能力方面，標(biāo)志著重大的飛躍。而當(dāng)前的數(shù)字移動(dòng)電話系統(tǒng)是優(yōu)化的聲音通信，3g 傳達(dá)者是面向多媒體消息的能力。</p><p>　　1.1 第一代蜂窩

58、系統(tǒng)</p><p>　　第一代蜂窩系統(tǒng)通常采用模擬頻率調(diào)制(FM) 技術(shù)。先進(jìn)移動(dòng)電話系統(tǒng) （AMPS） 是最顯著的第一代系統(tǒng)。AMPS是由貝爾電話系統(tǒng)開發(fā)的。它使用調(diào)頻語(yǔ)音傳輸和數(shù)字信號(hào)控制信息的技術(shù)。其他第一代生成的系統(tǒng)包括：</p><p>　　·窄帶模擬移動(dòng)電話業(yè)務(wù)（NAMPS）</p><p>　　·全接入通信系統(tǒng) （TACS)<

59、;/p><p>　　·北歐移動(dòng)電話系統(tǒng) (NMT-900)</p><p>　　所有第一代的蜂窩系統(tǒng)采用頻分多址(多址接入）在同一小區(qū)內(nèi)分配給每個(gè)信道唯一頻段。</p><p>　　1.2 第二代蜂窩系統(tǒng)</p><p>　　用戶數(shù)量迅速增長(zhǎng)和第一代系統(tǒng)的不兼容是走向第二代蜂窩系統(tǒng)的主要原因。第二代系統(tǒng)利用編碼技術(shù)與數(shù)字技術(shù)相關(guān)聯(lián)。所有

60、第二代系統(tǒng)采用數(shù)字調(diào)制方式。采用多址技術(shù)如時(shí)分多址(TDMA) 、碼分多址 (CDMA)與頻分多址一起使用。第二代蜂窩系統(tǒng)包括：</p><p>　　·美國(guó)第一套蜂窩系統(tǒng) （USDC） 標(biāo)準(zhǔn)是 IS-54 和 IS-136</p><p>　　·全球移動(dòng)通信 (GSM) 系統(tǒng)</p><p>　　·太平洋數(shù)字蜂窩 (PDC)</p

61、><p><b>　　·cdmaOne</b></p><p>　　1.3 第三代蜂窩系統(tǒng)</p><p>　　第三代蜂窩系統(tǒng)被設(shè)計(jì)為支持寬帶服務(wù)如高速互聯(lián)網(wǎng)接入、 視頻等具有相同的高質(zhì)量圖像傳輸作為固定網(wǎng)絡(luò)的質(zhì)量。下一代蜂窩系統(tǒng)的基本要求是：</p><p>　　·話音質(zhì)量敵得過(guò)公共交換電話網(wǎng)絡(luò) (PS

62、TN)。</p><p>　　·支持高數(shù)據(jù)速率。下表顯示3g 系統(tǒng)數(shù)據(jù)速率的要求</p><p>　　表 1.1： 3 G 數(shù)據(jù)速率要求</p><p>　　·支持分組交換和電路交換數(shù)據(jù)服務(wù)。</p><p>　　·更有效地使用可用的無(wú)線電頻譜</p><p><b>　　

63、83;支持各種移動(dòng)設(shè)備</b></p><p>　　·與原有的網(wǎng)絡(luò)和靈活引進(jìn)的新的服務(wù)和技術(shù)兼容</p><p>　　·自適應(yīng)的無(wú)線接口，適合于大多數(shù)的高度不對(duì)稱性質(zhì)</p><p>　　互聯(lián)網(wǎng)通訊: 下行比上行鏈路更大的帶寬。</p><p>　　引入多媒體到移動(dòng)通信的能力研究工作已進(jìn)行超過(guò)十年。不同的標(biāo)準(zhǔn)機(jī)

64、構(gòu)和理事機(jī)構(gòu)正試圖集成多種第三代蜂窩系統(tǒng)的建議。</p><p>　　下圖中，通過(guò)從 [1]，顯示的第三代蜂窩系統(tǒng)：</p><p>　　圖 1.1： 演化的 3g</p><p>　　引用演變 [2] 和 [3] 提供進(jìn)一步討論的第三代蜂窩演變系統(tǒng)。</p><p>　　1.4.WCDMA： 3g的空中接口</p><p

65、>　　3G 最有前途的途徑之一就是結(jié)合寬帶碼分多址(WCDMA) 空中接口與固定的 GSM 網(wǎng)絡(luò)。幾個(gè)提案支持WCDMA 被提交到國(guó)際電信聯(lián)盟 (ITU) 和其國(guó)際移動(dòng)電信在2000年 （IMT2000) 的3G倡議。他們 WCDMA 的各項(xiàng)建議是試圖合并幾個(gè)組織之間：</p><p>　　·日本協(xié)會(huì)的無(wú)線電行業(yè)和業(yè)務(wù) （ARIB）</p><p>　　·電信行業(yè)

66、解決方案 (ATIS) 聯(lián)盟</p><p><b>　　·T1P1</b></p><p>　　·歐洲電信標(biāo)準(zhǔn)協(xié)會(huì) (ETSI） 通過(guò)其特殊移動(dòng)集團(tuán) (SMG)</p><p>　　所有這些計(jì)劃的嘗試不忽視 WCDMA 無(wú)線電技術(shù)利用現(xiàn)有的 GSM 網(wǎng)絡(luò)的眾多優(yōu)勢(shì)。有的標(biāo)準(zhǔn)</p><p>　　出現(xiàn)

67、是基于對(duì) ETSI 的通用移動(dòng)通信系統(tǒng) (UMTS)俗稱為 UMTS 陸地電臺(tái)訪問 (UTRA) 。UTRAD的訪問計(jì)劃是直接序列碼分多址 （DS-CDMA）。信息遍布大約 5 MHz 頻帶。這種寬的帶寬引出名稱寬帶碼分多址或 WCDMA。即有兩種不同的模式</p><p>　　·頻分雙工 (FDD) </p><p>　　·時(shí)分雙工 (TDD)</p>

68、<p>　　由于不同地區(qū)有不同的頻率分配計(jì)劃，進(jìn)行操作的功能軟驅(qū)或 TDD 模式允許有效運(yùn)用現(xiàn)有的頻譜。簡(jiǎn)介FDD，TDD 模式的定義是考慮下一步。</p><p>　　FDD： 對(duì)于這種雙工的方法上行及下行傳輸采用兩個(gè)不同的頻段。一雙頻段與指定的用戶連接。</p><p>　　TDD： 在這雙工的方法中，上行和下行傳輸?shù)霓D(zhuǎn)接通過(guò)同步的時(shí)間間隔，因此時(shí)段在同一頻段通道分為傳輸和接

69、收的一部分。</p><p>　　我們制定了在 FDD 模式下運(yùn)行的 WCDMA 系統(tǒng)仿真。因此，所有第 2 章中提供的系統(tǒng)描述僅適用于FDD 模式。</p><p>　　1.4.1 WCDMA 關(guān)鍵技術(shù)</p><p>　　WCDMA 無(wú)線接口的操作要點(diǎn)如下 [3] [4]：</p><p>　　·支持高數(shù)據(jù)速率傳輸： 384 k

70、bps 的廣域覆蓋，2Mbps本地覆蓋。</p><p>　　·高服務(wù)靈活性： 每個(gè)連接支持多個(gè)并行的變率的服務(wù)。</p><p>　　·共同支持頻分雙工 (FDD) 和時(shí)分雙工 (TDD)。</p><p>　　·建于對(duì)未來(lái)的容量和覆蓋加強(qiáng)技術(shù)支持如自適應(yīng)天線，先進(jìn)的接收機(jī)結(jié)構(gòu)和變送器的多樣性。</p><p>

71、;　　·支持頻率與其他系統(tǒng)的兼容，包括兼容GSM 系統(tǒng)。</p><p>　　·有效數(shù)據(jù)包的訪問。</p><p>　　1.4.2 WCDMA 關(guān)鍵技術(shù)特征</p><p>　　芯片的速度可能會(huì)延長(zhǎng)至兩倍或三倍到標(biāo)準(zhǔn)的 3.84 Mcps到容納數(shù)據(jù)率高于 2 Mbps。選擇了 200khz 載波間隔為方便共存和 GSM 系統(tǒng)的互操作性。</

72、p><p><b>　　第 5 章</b></p><p><b>　　結(jié)論及未來(lái)工作</b></p><p>　　我們實(shí)施了一種信號(hào)物理層規(guī)范仿真的 IMT-2000 WCDMA 系統(tǒng)。不同信道數(shù)據(jù)的傳輸是基于幀基礎(chǔ)。多址干擾的情況下，傳輸?shù)男盘?hào)是已損壞。信號(hào)被進(jìn)一步破壞是在信道前端的接收器。簡(jiǎn)單的Rake分集接收是利用接收

73、器。</p><p>　　我們?cè)诓煌臅r(shí)間不同的信道調(diào)查上行和下行信道的誤碼率。按預(yù)期系統(tǒng)干擾受限于更多的用戶。</p><p>　　我們注意到，沒有任何的信道編碼方案和天線分集技術(shù)，誤碼率接近 10%作為系統(tǒng)負(fù)載超出 50%。這不是一種可接受性能。但是 BER 可以推回到通道可接受的限度編碼和天線分集技術(shù)。</p><p>　　發(fā)達(dá)國(guó)家的仿真器可以是寶貴的工具，以

74、調(diào)查WCDMA 在不同條件下的性能。例如可以仿真用于天線分集接收機(jī)在調(diào)查。仿真是基于測(cè)量和研究 WCDMA 性能非常靈活和一個(gè)可以很輕松地把所需的復(fù)雜統(tǒng)計(jì)修改信道模型實(shí)用的移動(dòng)通信信道條件。我們已經(jīng)證實(shí)它可以很簡(jiǎn)單的仿真觀察性能的糾錯(cuò)編碼。我們實(shí)施9.6 kbps 的上行語(yǔ)音應(yīng)用程序中的的卷積編碼方案。有人說(shuō)信道編碼可以大大降低特定信噪比下的誤碼率。</p><p>　　該仿真采用簡(jiǎn)單的 rake 接收機(jī)，利用時(shí)

75、間所產(chǎn)生的增益多樣性。多徑環(huán)境的空間屬性可以是多樣性的另一個(gè)來(lái)源。自適應(yīng)天線接收器用于利用此分集增益。仿真可以用于研究不同的自適應(yīng)算法的增益多樣性。時(shí)空rake接收機(jī)或已擬二維RAKE接收機(jī)結(jié)合時(shí)間和空間的多樣性。分集技術(shù)在下行日趨快速普及因?yàn)樗麄儾粫?huì)導(dǎo)致更多硬件移動(dòng)基站的復(fù)雜性。我們正在研究各種發(fā)射分集計(jì)劃和 WCDMA系統(tǒng)不同的二維 rake 接收機(jī)。該仿真器是動(dòng)態(tài)的以便一大批幀傳輸而不是一次發(fā)射一個(gè)幀。</p>&l