外文翻譯--ASP. NET 中認(rèn)證安全特征評(píng)述

1、.南京郵電大學(xué)通達(dá)學(xué)院畢業(yè)設(shè)計(jì)(論文)外文資料翻譯學(xué) 院：通達(dá)學(xué)院 專業(yè)：網(wǎng)絡(luò)工程 學(xué)生姓名： 班級(jí)學(xué)號(hào)： 外文出處： Simulation of Time-Varying, Frequency-Selective Multipath Fading Channels forSpread-Spectrum Waveforms附件：1.外文資料翻譯譯文；2.外文原文指導(dǎo)教師評(píng)價(jià)：1翻譯內(nèi)容與課題的結(jié)合度： 優(yōu) 良 中 差2翻譯內(nèi)容的準(zhǔn)確、流暢： 優(yōu) 良 中 差3專業(yè)詞匯翻譯的準(zhǔn)確性： 優(yōu) 良 中 差4翻譯字符數(shù)是否符合規(guī)定要求： 符合 不符合 指導(dǎo)教師簽名：年月日附件1：外文資料翻譯譯文ASP.

2、NET 中認(rèn)證安全特征評(píng)述Narcisio Tumushabe ,譚冠正(音譯)(中南大學(xué)計(jì)算機(jī)科學(xué)與信息技術(shù)學(xué)院, 湖南長沙410083)摘要: 一個(gè)適用于任意的擴(kuò)頻信道模擬器傳輸任意隨時(shí)間變化的波形，頻率選擇性多徑瑞利衰落渠道的開發(fā)和實(shí)施。都多普勒（或時(shí)間）的多樣性和延遲（或頻率）多樣性被認(rèn)為是在信道模型的siinuhtor是根據(jù)。的信道被假定為是一個(gè)隨時(shí)間變化的服從不相關(guān)的高斯信道，散射的假設(shè)。模型由多個(gè)多普勒頻移的分支抽頭延遲線。沒有假設(shè)是由獨(dú)立的通道水龍頭。仿真結(jié)果為平坦慢衰落，平快衰落，頻率選擇性慢衰落和頻率選擇快衰落的例子給出。1 介紹多徑衰落的一種現(xiàn)象，介紹了信號(hào)通過在多個(gè)所引

3、起的失真的干擾傳播路徑上的通信信道。很好一種時(shí)變多徑衰落信道的例子是移動(dòng)無線通信信道。在移動(dòng)無線電信道，多徑傳播時(shí)發(fā)生的信號(hào)從周圍的物體反射，和相對(duì)運(yùn)動(dòng)發(fā)射機(jī)和接收機(jī)之間的介紹在通道中，表現(xiàn)為隨時(shí)間的變化多普勒展寬譜中的多徑組件。模擬多徑的最準(zhǔn)確的方法衰落信道的使用實(shí)際記錄的條寬帶信道測(cè)量。然而，由于系統(tǒng)性能分析的復(fù)雜性記錄的數(shù)據(jù)，從理論上推導(dǎo)了信道模擬器原則是感興趣的，特別是用于系統(tǒng)性能評(píng)價(jià)我。最常見的統(tǒng)計(jì)研究人員使用的信道模型是廣義的固定不相關(guān)的散射（WSSUS）模型貝洛 2 。先前設(shè)計(jì)模擬器，3-81主要是定制的WSSUS信道的特殊類型。在本文中開發(fā)的模擬器進(jìn)行了改進(jìn)在幾個(gè)方面。首先，它

4、是一個(gè)通用的信道模擬器具有對(duì)信道衰落的選擇沒有限制參數(shù)。沒有假設(shè)結(jié)構(gòu)的信道散射函數(shù)或發(fā)送的信號(hào)。任意定義的散射函數(shù)信號(hào)波形被提供給模擬器Matlab的M文件形式。其次，信道模型該模擬器是基于采用多普勒（或時(shí)間）的多樣性和延遲（或頻率）的多樣性為了消除信道抽頭的時(shí)間變化一個(gè)符號(hào)間隔內(nèi)。此外，雖然傳統(tǒng)的連續(xù)時(shí)間非相干散射采用的假設(shè)是，沒有假設(shè)在等效tapdelay信道抽頭的獨(dú)立性信道模型。那是，實(shí)際的協(xié)方差的信道抽頭結(jié)構(gòu)的計(jì)算和應(yīng)用。最后，而不是生成的信道的信封輸出，該模擬器產(chǎn)生的復(fù)雜多樣的價(jià)值的通道輸出通道上保存的相位失真。在本文中，我們討論的設(shè)計(jì)與實(shí)現(xiàn)的模擬和演示的性能對(duì)幾種多路模擬數(shù)據(jù)傳輸渠

5、道。本文的組織如下。通道模型，給出了模擬器的基礎(chǔ)2節(jié)，和模擬器的實(shí)現(xiàn)在3節(jié)中簡要的討論。仿真結(jié)果演示的信道模擬器的性能在第4節(jié)。最后，在第5節(jié)中，我們討論未來的工作和目前的一些總結(jié)。2 信道模型所考慮的基帶信道建模作為一個(gè)隨時(shí)間變化的復(fù)值隨機(jī)過程，其中，表示的輸出由于一個(gè)脈沖在時(shí)間f的信道在時(shí)間發(fā)送。據(jù)推測(cè)，是一個(gè)零均值，復(fù)高斯隨機(jī)過程是，固定在t，滿足非相關(guān)散射假設(shè)，即，其中一個(gè)橫杠表示復(fù)共軛，代表平均輸出功率的信道和（t）是Dirac函數(shù)9，10。如果一個(gè)基帶信號(hào)單側(cè)帶寬CL通過低通脈沖信道傳輸響應(yīng)，然后不加性噪聲，低通通道輸出的R（t）是由其中是H（R），一個(gè)fiinction的的投影，

6、到帶寬限制的功能的空間的間隔 11。假設(shè)的信號(hào)也是有限的時(shí)間到的時(shí)間間隔0，T，我們得到其中， x，數(shù)，（r）= ei'NJ'/ Tx的（t）表示的原始信號(hào)多普勒頻移由n / T的赫茲，和表示的傅里葉變換，相對(duì)于所述變量t，突起相關(guān)的空間上的時(shí)間有限的時(shí)間間隔0，T的功能。關(guān)于二階在規(guī)定的假設(shè)過程克， 的結(jié)構(gòu)將是零均值復(fù)雜KIT R'高斯隨機(jī)變量。另外，如果散射功能（實(shí)質(zhì)上）有限時(shí)間區(qū)間0，和帶限的時(shí)間間隔，只有有限的水龍頭將有非零的差異。在特別是，最大值所需的k是約和最大的n值需要的是約N = 待定。相當(dāng)于tapdelay線模型的信道在圖1中示出以下。請(qǐng)注意，對(duì)于在區(qū)

7、間O，T，它代表一個(gè)任意碼元周期中，信道是完全其特征在于由該矢量的信道抽頭這意味著，在任何符號(hào)的信道行為時(shí)間間隔可以是通過生成一個(gè)實(shí)現(xiàn)了模擬高斯隨機(jī)向量克。如果我們假設(shè)信道解相關(guān)在一個(gè)符號(hào)間隔（TBd> I），然后多個(gè)符號(hào)的時(shí)間間隔可以通過產(chǎn)生模擬多個(gè)獨(dú)立的實(shí)現(xiàn)的向量網(wǎng)絡(luò)連接。在為了做到這一點(diǎn)，我們首先需要確定R.的協(xié)方差結(jié)構(gòu)測(cè)定必要的協(xié)方差結(jié)構(gòu)很簡單，但繁瑣的。為方便起見，我們簡單地總結(jié)協(xié)方差的結(jié)果在下面的散射函數(shù)（T，H）的通道。等價(jià)表示可以中給出的二維傅里葉變換的散射函數(shù)，它代表了間隔時(shí)間，間隔頻率的相關(guān)函數(shù)的通道。3 實(shí)施問題在本節(jié)中，我們先簡要地說明實(shí)施該模擬器使用MATLAB

8、。以下變量需要來自用戶的輸入：文件名定義傳輸信號(hào)的功能（符號(hào)波形），發(fā)射的信號(hào)的持續(xù)時(shí)間（T），假設(shè)發(fā)送的信號(hào)的帶寬（Q），文件名的功能定義通道散射功能，0假設(shè)信道多普勒擴(kuò)展（BD），假設(shè)信道時(shí)延擴(kuò)展（TNR）數(shù)量：多普勒分支模擬（2 N+ l）中，數(shù)延遲抽頭模擬（K +1），使用預(yù)先計(jì)算好的水龍頭 - 協(xié)方差矩陣的選項(xiàng)（Z）或計(jì)算一個(gè)新的。該程序會(huì)自動(dòng)生成輸出采樣的輸出信號(hào)的奈奎斯特速率。為了確定用于輸出信號(hào)的奈奎斯特速率，該程序必須結(jié)合上的通道的擴(kuò)展的影響發(fā)送的信號(hào)。片面帶寬發(fā)送的信號(hào)是0。渠道傳播的2xBd=2XN/ T.因此，發(fā)送信號(hào)片面的總帶寬是氯'= R+ RN I T。為

9、了達(dá)到奈奎斯特速率，采樣頻率必須至少2倍的速度比的輸出信號(hào)的帶寬，這是程序加載存儲(chǔ)的自來水協(xié)方差矩陣或計(jì)算一個(gè)新的抽頭 - 協(xié)方差矩陣，這取決于由用戶選擇的選項(xiàng)。如果是后者的選項(xiàng)被選擇，該方案將計(jì)算協(xié)方差矩陣數(shù)值使用方程（2.1）（2.4）和散射中定義的所提供的功能的功能用戶。該程序的其余部分產(chǎn)生一個(gè)單獨(dú)為每個(gè)發(fā)射符號(hào)矢量輸出然后結(jié)合單獨(dú)的輸出矢量，表示總的信道輸出到一個(gè)輸出流，包括任何的符號(hào)間干擾。為了完成此時(shí)，程序首先生成信道抽頭vectorfi在下面的一個(gè)特定符號(hào)的輸入時(shí)尚： 一個(gè)復(fù)雜的零均值高斯隨機(jī)向量和協(xié)方差矩陣I產(chǎn)生。 將所得的復(fù)高斯矢量乘以抽頭 - 協(xié)方差矩陣的平方根產(chǎn)生信道抽頭

10、實(shí)現(xiàn)。抽頭產(chǎn)生后，該程序計(jì)算根據(jù)輸出樣本最后，將樣品對(duì)應(yīng)于當(dāng)前符號(hào)被添加到適當(dāng)?shù)奈恢迷谕ǖ赖妮敵鼍彌_器。4 仿真結(jié)果在本節(jié)中，我們提出了幾個(gè)例子說明新的信道模擬器的性能。所有的結(jié)果dikcussed這部分對(duì)應(yīng)于簡單的直接序列碼分多存取波形組成的序列矩形芯片波形。所有的擴(kuò)頻碼是隨機(jī)生成的碼片持續(xù)時(shí)間和傳播增益取決于信道的特征模擬。1毫秒一個(gè)符號(hào)持續(xù)時(shí)間所有信道的假設(shè)，和信道的散射功能被認(rèn)為有以下的高斯參數(shù)形式：在stvtul = SDT，。信道衰落參數(shù)四個(gè)案例說明在這里了表1。-為每個(gè)四例仿真結(jié)果在圖5給出了。這些數(shù)字表明，該仿真結(jié)果與預(yù)期渠道吻合下的衰落的情況下考慮的行為。5 結(jié)論與未來工作以

11、前開發(fā)的多徑衰落模擬器通道，主要設(shè)計(jì)用于特定類型的通道。通過將多普勒和延遲在模擬器的設(shè)計(jì)以及正確的多樣性模擬信道抽頭之間的相關(guān)性，一般用途多徑模擬器已經(jīng)研制成功。幾個(gè)不同的衰落情況下的模擬結(jié)果同意與預(yù)期的通道的行為，從而驗(yàn)證模擬器的正確性。目前執(zhí)行的模擬器假設(shè)在一個(gè)符號(hào)中的信道行為解相關(guān)間隔。因此，它是必要的使用很長的符號(hào)的時(shí)間間隔準(zhǔn)確地模擬慢衰落特性。使用模擬器的復(fù)雜性，并建立不必要的高計(jì)算復(fù)雜度。當(dāng)前工作的重點(diǎn)是提高sirnulator模型正確符號(hào)間隔之間的相關(guān)性。參考文獻(xiàn):1 Bell ,J . , et al ,2001 ,ASP. NET Programmers Reference

12、,Wrox Press Ltd. ,USA.2 Chilakala ,V. ,2001 ,Microsoft ASP. NET Security ,Microsoft Support WebCasts.3 Gonzales ,J . ,2002 ,15 Seconds : Using Forms Authentication in ASP. NET Part 14 Kercher ,J . ,2001 ,Authentication in ASP. NET : . NET, Security Guidance ,MSDN Magazine August 2001.5 Lassan ,R. ,S

13、mith , E. ,2002 ,ASP. NET Bible ,Hungry ,Minds Inc. ,USA.6 Leinecker , R. , 2002 ,Using ASP. NET ,Que Corporation , Indiana.7 NET Framework Developers Guide : ASP. NET Web.Application Security ,Link.8 Kieley ,J . ,2001 ,Migrating to ASP. NET : Key Consid2eration ,MSDN Magazine November 2001.附件2：外文原文

14、Simulation of Time-Varying, Frequency-Selective Multipath Fading Channels forSpread-Spectrum WaveformsLei-Lei LockCadence Design SystemsSan Jose, CAXiangming Kong and Richard J. BartonElectrical and Computer Engineering DepartmentIowa State UniversityAmes, IA 5001 1Abstract : A channel simulator app

15、ropriate for arbitrary spread spectrum waveforms transmitted over arbitrary time varying, frequency-selective multipath Rayleigh fading channels has been developed and implemented. Both Doppler (or time) diversity and delay (or frequency)diversity are considered in the channel model on which the sim

16、ulator is based. The channel is assumed to be a time varying Gaussian channel that obeys the uncorrelated scattering assumption. The model developed consists of multiple Doppler-shifted branches of tap-delay lines. Noassumptions are made about the independence of channel taps. Simulation results for

17、 flat slow fading, flat fast fading, frequency-selective slow fading and frequency selective fast fading examples are presented1. IntroductionMultipath fading is a phenomenon that describes signal distortion caused by interference among multiple propagation paths on a communication channel. A good e

18、xample of a time-varying multipath fading channel is the mobile radio communication channel. In a mobile radio channel, multipath propagation occurs as the signal is reflected from surrounding objects, and the relative motion between the transmitter and the receiver introduces temporal variation in

19、the channel that is manifested as a Doppler spread in the spectrum of the multipath components. The most accurate method of simulating multipath fading channels is to use recorded strips of actual wideband channel measurements. However, due to the complexity of analyzing system performance using rec

20、orded data, channel simulators derived from theoretical principles are of interest, particularly for use in system performance evaluation I. The most common statistical channel model used by researchers is the wide-sense stationary uncorrelated scattering. Simulators designed previously l , 3-81 wer

21、e primarily tailored for particular types of WSSUS channels. The simulator developed in this paper is improved in several respects. Firstly, it is a general purpose channel simulator with no constraint on the choice of channel fading parameters. No assumptions are made regarding the structure of the

22、 channel scattering function or the transmitted signal. Arbitrarily defined scattering functions and signaling waveforms are provided to the simulator in the form of MatLab m-files. Secondly, the channel model on which the simulator is based incorporates both Doppler (or time) diversity and delay (o

23、r frequency) diversity in order to eliminate temporal variation of the channel taps within a single symbol interval. Furthermore, although the conventional continuous-time uncorrelated scattering assumption is adopted, no assumption is made regarding the independence of channel taps in the equivalen

24、t tapdelay channel model. That is, the actual covariance structure of the channel taps is computed and utilized. Finally, instead of generating the envelope of the channel output, the simulator generates cornplex valued channel output to preserve the phase distortion on the channel.In this paper we

25、discuss the design and implementation of the simulator and demonstrate its performance by simulating data transmission on several multipath channels. The paper is organized as follows. The channel model on which the simulator is based is presented in Section 2, and the implementation of the simulato

26、r is discussed briefly in Section 3. Simulation results demonstrating the performance of the channel simulator are presented in Section 4. Finally, in Section 5, we discuss future work and present some concluding remarks.2. Channel ModelThe baseband channel under consideration is modeled as a time-v

27、arying complex-valued random process h(7;r)17 2 0,r E R, where h(7;r) represents the output of the channel at time f due to an impulse transmitted at time t - r . It is assumed that h(.r;r) is a zero mean, complex Gaussian random process that is causal in 7, stationary in t, and satisfies the uncorr

28、elated scattering assumption; i.e., where an overbar indicates complex conjugation, $, represents the average power output of the channel and 8(t) is the Dirac delta function 9, IO. If a baseband signal x(r) with one-sided bandwidth Cl is transmitted through a channel with low-pass impulse response

29、h(.t;t), then ignoring additive noise, the low-pass chann-el output r(r) is given by where i ( T ; f ) is the projection of h ( ; r )a,s a fiinction of T, onto the space of functions bandlimited to the interval -fl,fl l 11. Assuming the signal is also time-limited to the interval 0, TI, we getwhere

30、x, ( r ) = ei'NJ'/Tx(t) represents the original signal Doppler shifted by n/T Hz, and represents the Fourier transform, with respect to the variable f, of the projection of h(r;r + T) onto the space of functions time-limited to the interval 0, TI. Under the stated assumptions concerning the

31、secondorder structure of the process g ( T ; r ) , the taps, , k = - RA ( x k . z n ) will be zero-mean complex KIT R ' T Gaussian random variables. Furthermore, if the scattering function is (essentially) time-limited to the interval 0, T, and bandlimited to the interval -2rtBd,2xBd, only finit

32、ely many of the taps will have nonzero variance. In particular, the maximum value of k required is approximately K = RT,/x and the maximum value of n required is approximately N = TBd. The equivalent tapdelay line model of the channel is illustrated in Figure 1 below.Figure 1. The tap delay structur

33、e of the channelNotice that for the interval O,T, which represents an arbitrary symbol period, the channel is completely characterized by the vector of channel taps This implies that the channel behavior during any symbol interval can be simulated by generating a realization of the Gaussian random v

34、ector g . If we assume that the channel decorrelates over one symbol interval (TBd > I), then multiple symbol intervals can be simulated by generating multiple independent realizations of the vector fi. In order to accomplish this, we first need to determine the covariance structure of R. The det

35、ermination of the necessary covariance structure is straightforward but tedious. For convenience, we simply summarize the covariance results below in terms of the scattering function s(T;h) of the channel. An equivalent representation can be given in terms of the two-dimensional Fourier transform of

36、 the scattering function, which represents the spaced-time, spaced-frequency correlation function of the channel.If k = 1 and m = n,3. Implementation IssuesIn this section we explain briefly the implementation of the simulator using MatLab. The following variables are required as input from the user

37、: File name of function defining transmitted signal (symbol waveform), Duration of transmitted signal (T), Assumed bandwidth of transmitted signal (Q), File name of function defining channel scattering function, 0 Assumed channel Doppler spread ( Bd), Assumed channel delay spread ( Tnr), Number of D

38、oppler branches simulated ( 2 N + l), Number of Delay taps simulated ( K + 1), Option of using precomputed tap-covariance matrix (Z,) or computing a new one. The program automatically generates output samples at the Nyquist rate of the output signal. To determine the Nyquist rate for the output sign

39、al, the program must incorporate the spreading effects of the channel on the transmitted signal. The one-sided bandwidth of the transmitted signal is 0. The channel spreads the transmitted signal by 2xBd = 2xN / T. Therefore, the total one-sided bandwidth is Cl' = R + RN I T . To reach Nyquist r

40、ate, we must sample at least two times faster than the output-signal bandwidth, which is -=It -= x x/Q x x R+-N 1 + - N T TR The program loads a stored tap-covariance matrix or calculates a new tap-covariance matrix, depending on the option selected by the user. If the latter option is chosen, the p

41、rogram will compute the covariance matrix numerically using Equations (2.1) - (2.4) and thescattering function as defined in the function provided by the user.The remaining portion of the program generates a vector of output for each transmitted symbol individually and then combines the individual o

42、utput vectors into an output stream that represents the total channel output, including any intersymbol interference. To accomplish this, the program first generates the channel tap vectorfi for a particular symbol of the input in the following fashion:A complex Gaussian random vector with mean zero

43、 and covariance matrix I is generated.The resulting complex Gaussian vector is multiplied by the square root of the tap-covariance matrix to generate a realization of the channel taps.After the taps are generated, the program computes the output samples according toFinally, the samples corresponding

44、 to the currentsymbol are added to the appropriate locations in thechannel output buffer.4. Simulation ResultsIn this section, we present several examples illustrating the performance of the new channel simulator. All of the results discussed in this section correspond to the transmission of simple

45、direct-sequence code-division-multiple-access waveforms consisting of sequences of rectangular chip waveforms. All spreading codes were randomly generated and the chip duration and spreading gain varies depending on the characteristics of the channel being simulated. A symbol duration of 1 milliseco

46、nd was assumed for all of the channels, and the channel scattering function was assumed to have the following Gaussian 1 7 7 1- parametric form:where StVtul = SdT, . The channel fading parameters for each of the four cases illustrated here are summarized in Table 1 .- The simulation results for each

47、 of the four cases are presented in Figures 2-5. As these figures indicate, the simulation results agree well with the expected channel behavior under each of the fading scenarios considered.5. Conclusions and Future WorkPreviously developed simulators for multipath fading channels were designed pri

48、marily for a particular type of channel. By incorporating both Doppler and delay diversity in the simulator design as well as correctly modeling the correlation between channel taps, a generalpurpose multipath simulator has been developed. Simulation results for several different fading scenarios ag

49、ree well with anticipated channel behavior and thus verify the correctness of the simulator.The current implementation of the simulator assumes that the channel behavior decorrelates in one symbol interval. Hence, it is necessary to use very long symbol intervals to accurately simulate slow fading characteristics. This complicates use of the simulator and creates unnecessarily high computational complexity. Curr