cdma綜述外文翻譯

1、<p><b>　　附 錄</b></p><p><b>　　1. 英文原文</b></p><p>　　An Overview of CDMA</p><p>　　CDMA Basics</p><p>　　CDMA systems spread a slow information

2、bit rate with a fast chip sequence, transmit it over the air and retrieve the original information. How to actually spread and retrieve the information is standardized in details in IS-95. Three main tools are used:</

3、p><p>　　Walsh codes, 64-chip orthogonal sequences</p><p>　　A short code: 215 - 1 = 32767 chips long, which has the property of being orthogonal to any nonzero offset of itself.</p><p>

4、　　A long code: 242 chips long, used to generate unique sequences, which are pseudo-orthogonal to one-another.</p><p>　　The following sections go into further details on where these tools are used in various

5、aspects of the IS-95 air interface: on forward links, reverse links, in access mode, and in traffic mode.</p><p>　　Walsh Codes</p><p>　　Forward Link Walsh codes are orthogonal codes, IS-95 uses

6、them to multiplex several mobile communications (and control channels) on the forward link. </p><p>　　In the forward link, each mobile uses a specific Walsh code sequence; all sequences are multiplexed toget

7、her in a total combined sequence:</p><p>　　(where si represents the information symbol (+1 or -1), gi is the individual channel gain.) That sequence is manipulated further and sent over the air; on the recei

8、ver side, that sequence is decoded by simply integrating for each channel: for channel k, the information bit is retrieved from the sign of the integral:</p><p>　　Reverse Link In the reverse link of IS-95, W

9、alsh codes are not used in that manner but simply encode bits in a 64-ary encoding scheme: that s each 6-bit sequence is mapped to a 26 = 64 bit Walsh code.</p><p>　　In further evolutions like IS-2000 and IS

10、-856, the reverse link multiplexes several channels similarly to the forward link, and Orthogonal properties of the Walsh codes provide the multiplexing scheme:</p><p>　　Short Code</p><p>　　Shor

11、t codes are bit sequences with very specific autocorrelation functions. IS-95 uses a 215 - 1 = 32767 chip short code. For a first example let us use here a 22 - 1 = 3 bit long short code: 100.</p><p>　　Permu

12、tated, that short code has the following property: if +1 is counted for every bit of the permutated sequence that is identical to the bit of the original sequence, and -1 is counted when that bit is different, every perm

13、utated sequence totals -1, whereas the original sequence obviously totals its length .</p><p>　　If we note < S,S(n) > the above computation, we have for a short code sequence:</p><p>　　Thi

14、s is a remarkable property of autocorrelation between bit sequences that is used in CDMA. As another example, verify the following two short code sequences (of length 23 - 1 = 7) verify the same property as the table abo

15、ve: s1 = 0011101 and s2 = 1110010. These two sequences are used for Gold codes in other CDMA standards. And another short code (of length 25 - 1 = 31) is s3 = 0000101011101100011111001101001.</p><p>　　IS-95

16、uses a much longer such sequence (215 - 1 = 32768 chips) which provides many possible sequences orthogonal to one another, used to differentiate between sectors on the forward link.</p><p><b>　　Long Co

17、de</b></p><p>　　Long code is a sequence of bits used for its pseudo-orthogonal properties; that much longer sequence does not have the perfect autocorrelation properties as the short code, but a simila

18、r one such that:</p><p>　　This pseudo orthogonal property is used in IS-95 reverse link in a 1.2288Mcps chip sequence to differentiate between mobiles. On the forward link the long code is decimated down to

19、a 19.2kbps bit stream for a unique user mask.</p><p>　　IS-95A Reverse Traffic Channel Detection Demo</p><p>　　The IS-95A Reverse Traffic Channel Detection demo simulates modulation and spreading

20、 of the data symbols at the mobile station transmitter, as well as despreading and noncoherent demodulation at the base station receiver. At the transmitter, the symbols are modulated by a Walsh modulator and spread, and

21、 a randomized gating is applied to the transmit bursts. At the receiver, the noncoherent rake demodulator recovers the data. The bit error rate for the data is displayed in the simulation.</p><p>　　You can o

22、pen the model by following the instructions in Opening a Demo, or by typing is95revchdetection2 at the MATLAB prompt.</p><p>　　Library Blocks in the Demo</p><p>　　The IS-95A Reverse Traffic Chan

23、nel Detection demo uses these library blocks from the CDMA Reference Blockset:</p><p>　　IS-95A Rev Ch Detector.</p><p>　　IS-95A Rev Ch Walsh Modulation and Spreading.</p><p>　　IS-95

24、A Short Code Generator.</p><p>　　How the Demo Works</p><p>　　Among the components used at the transmitter, the Data Source subsystem provides a source for random data bits, the data rate for the

25、 channel, and the short pseudonoise (PN) code used for the in-phase and quadrature spreading of the signal. In particular, the IS-95A Short Code Generator library block generates the short PN code.</p><p>　　

26、The Spreading and Modulation subsystem contains several blocks that are responsible for the Walsh modulation, and the spreading with the long and short PN codes. The IS-95A Rev Ch Walsh Modulation and Spreading library b

27、lock contains the IS-95A Rev Ch Burst Randomizer library block, which processes the long code and generates a gating signal based on the long code and the data rate of the input frame. The IS-95A Rev Ch Walsh Modulation

28、and Spreading library block also groups the input data in 6-</p><p>　　The Transmit Filter block generates the I and Q waveforms. The Q waveform is delayed by a 1/2-chip duration relative to the I waveform.&l

29、t;/p><p>　　The Rayleigh Multipath and AWGN Channel subsystem simulates the propagation through multiple paths of a Rayleigh fading channel. Complex white Gaussian noise is added to the channel output; this nois

30、e represents the interference generated by other base stations that are using the same frequency band.</p><p>　　In the receiver section, the incoming signal is first filtered by the Receive Filter block, whi

31、ch implements a filter matched to the transmit filter. The filters in this demo are designed to maximize the signal power within the desired frequency band.</p><p>　　Then the filtered signal is sent to the I

32、S-95A Rev Ch Detector library block, which contains the reverse channel rake receiver. The rake receiver consists of three rake fingers that are set to different delays to handle up to three multipaths. Each active rake

33、finger performs the despreading of the input data with the short PN sequence, followed by despreading with the long code. This is followed by the correlation with the entire set of 64 Walsh codes. The energies in the I a

34、nd Q components are</p><p>　　The Error Rate Calculation block compares the transmitted bits and the received decisions, and produces the raw (that is, without channel coding) bit error rate. This rate is dis

35、played in the model window during the simulation.</p><p>　　Visible Results of the Demo</p><p>　　The demo shows the raw bit error rate (BER) for the reverse channel. The BER depends on the channe

36、l conditions and the number of rake receiver fingers active. As the signal-to-noise ratio or the channel conditions are changed, the effect of these on the raw BER can be seen by running the model for these different con

37、ditions.</p><p>　　Changing Demo Parameters</p><p>　　This section suggests some ways that you can alter the parameters in the demo after you understand the model.</p><p>　　The simula

38、tion duration in this demo is set to 2 seconds. Because the frame duration in IS-95A is 0.02 second, this model processes 100 frames. This gives a sufficient time for the BER measurements to converge at reasonable SNR se

39、ttings. To run the simulation for a longer or shorter time, select Parameters from the Simulation menu and change the Stop time to 0.02 times the number of frames you want to simulate.</p><p>　　To change the

40、 data rate, double-click on the Data Source icon. Then double-click on the Mobile Station Transmitter Data Rate icon and change the Data Rate parameter. Choices are Full, Half, Quarter, and One-Eighth rates.</p>&

41、lt;p>　　To change the long code mask, double-click on the Spreading and Modulation icon. Then double-click on the IS-95A Rev Ch Walsh Modulation and Spreading icon, and enter a new value for the Long code mask paramete

42、r. This parameter can be any nonnegative integer less than 242-1. The block uses the binary representation of this number to generate the code. The value for the Long code mask parameter is also required in the IS-95A Re

43、v Ch Detector library block. Experiment with using the same or differe</p><p>　　To change the Doppler frequency, double-click on the Rayleigh Multipath and AWGN Channel icon. Then double-click on the Multipa

44、th Rayleigh Fading icon, and change the Doppler frequency parameter. Reasonable Doppler frequencies representative of the cellular mobile environment are in the 0 to 200 Hz range.</p><p>　　Change the Es/No p

45、arameter in the AWGN Channel block in the channel subsystem. The detection performance improves with an increase in the signal-to-noise ratio.</p><p>　　To run the simulation with different seeds, change the

46、Initial seed parameters in one or more of these:</p><p>　　Random Data Frame Generator</p><p>　　Multipath Rayleigh Fading</p><p>　　AWGN Channel</p><p>　　The first item i

47、s inside the Data Source subsystem and the last two blocks are inside the Rayleigh Multipath and AWGN Channel subsystem.</p><p>　　Channel Paths and Rake Fingers. Changes in the number or delay of fading ch

48、annel paths and rake fingers must correspond to each other. To change the number or delay of fading channel paths, double-click on the Rayleigh Multipath and AWGN Channel icon. Then double-click on the Multipath Rayleigh

49、 Fading icon and change the Delay vector parameter. The vector length of this parameter is the number of paths and the vector elements measure the delay of each path in seconds.</p><p>　　To change the number

50、 or delay of rake fingers, double-click on the Initial Phases and Finger Enables icon and change the Constant value parameter. The three consecutive pairs of elements of this length-six vector indicate the delay and stat

51、us of the three rake fingers. The delay is measured in samples, not in seconds. A status of zero disables the finger and a status of one enables the finger. By default, this demo enables two rake fingers, with delays of

52、96 and 116 samples, respectively. These </p><p><b>　　2. 中文翻譯</b></p><p><b>　　CDMA綜述</b></p><p><b>　　CDMA的基礎(chǔ)</b></p><p>　　CDMA系統(tǒng)中傳播緩

53、慢的信息比特率，快速的芯片序列空中傳輸和檢索的原始信息。如何傳播和獲取信息是在IS-95的詳細(xì)信息的標(biāo)準(zhǔn)化。三個(gè)主要的工具是：Walsh碼，正交序列64片</p><p>　　一個(gè)簡(jiǎn)短的代碼：215 - 1 = 32767芯片，它具有本身任何非零偏移正交的財(cái)產(chǎn)。</p><p>　　一個(gè)長(zhǎng)碼：長(zhǎng)242芯片，用于生成唯一的序列，這是一個(gè)另一個(gè)偽正交。</p><p>

54、　　以下各節(jié)進(jìn)入這些工具的使用在各方面的IS-95空中接口的進(jìn)一步的細(xì)節(jié)：正向鏈接，反向鏈接，訪問(wèn)模式，并在交通模式。</p><p><b>　　Walsh碼</b></p><p>　　前向鏈路Walsh碼的正交碼，IS-95采用復(fù)用移動(dòng)通信的前向鏈路（控制通道）。</p><p>　　在前進(jìn)的鏈接，每個(gè)移動(dòng)使用特定的Walsh碼序列;序列

55、復(fù)總結(jié)合序列：</p><p>　?。⊿I代表的信息符號(hào)（+1或-1），gi是個(gè)別通道的增益。）該序列的進(jìn)一步操縱，并在空中發(fā)送，在接收端，該序列是簡(jiǎn)單地為每個(gè)通道集成解碼： ?通道，積分的標(biāo)志位信息檢索：</p><p>　　在IS-95的反向鏈接，反向鏈接，Walsh碼不使用這種方式，但簡(jiǎn)單的編碼位64進(jìn)制編碼方案：那每6位序列映射到26 = 64位Walsh碼。</p>

56、<p>　　像IS-2000 IS-856的進(jìn)一步演變，在反向鏈路復(fù)用多種渠道同樣的前向鏈路，Walsh碼的正交特性提供的復(fù)用方案：</p><p><b>　　短碼</b></p><p>　　短碼是非常具體的自相關(guān)函數(shù)的位序列。 IS-95采用的是215 - 1 = 32767芯片的短碼。對(duì)于第一個(gè)例子，讓我們?cè)谶@里使用了22 - 1 = 3位長(zhǎng)的短的

57、代碼：100。</p><p>　　這短短的代碼具有以下屬性：如果+1每的permutated序列位是相同的原始序列的位，并計(jì)算-1時(shí)，該位??是不同的的計(jì)算，每permutated的序列總數(shù)-1 ，而原來(lái)的序列顯然總長(zhǎng)度。</p><p>　　如果我們注意到<選，（N）>上面的計(jì)算，我們有一個(gè)簡(jiǎn)短的代碼序列：</p><p>　　這是自相關(guān)的位序列在C

58、DMA之間的顯著特性。作為另一個(gè)例子，驗(yàn)證以下兩個(gè)短代碼序列（長(zhǎng)度為23 - 1 = 7）核實(shí)上述表格的相同的屬性：S1 = 0011101和s2 = 1110010。這兩個(gè)序列被用于在其他CDMA標(biāo)準(zhǔn)的黃金守則。和另一個(gè)短碼（長(zhǎng)度為25 - 1 = 31）是S3 = 0000101011101100011111001101001。</p><p>　　IS-95，使用更長(zhǎng)的序列（215 - 1 = 32768芯

59、片），它提供了許多可能的序列彼此正交的，用來(lái)區(qū)分前向鏈路上的扇區(qū)。</p><p><b>　　長(zhǎng)碼</b></p><p>　　長(zhǎng)碼是用于其偽正交特性的比特序列較長(zhǎng)的序列不具有完美的自相關(guān)特性為短碼，但類似的一個(gè)這樣：</p><p>　　這個(gè)偽正交屬性用于在1.2288Mcps芯片序列在IS-95反向鏈接到手機(jī)之間的區(qū)分。長(zhǎng)碼前向鏈路上被消

60、滅了一個(gè)獨(dú)特的用戶面具到19.2kbps的比特流。</p><p>　　IS-95A反向業(yè)務(wù)信道檢測(cè)演示</p><p>　　IS-95A的反向業(yè)務(wù)信道檢測(cè)演示，模擬調(diào)制，在移動(dòng)臺(tái)發(fā)射機(jī)的數(shù)據(jù)符號(hào)和傳播，以及在基站接收機(jī)和非相干解擴(kuò)解調(diào)。在發(fā)射機(jī)，符號(hào)是由沃爾什的調(diào)制和傳播調(diào)制，隨機(jī)門適用于發(fā)射陣陣。在接收端，非相干的耙解調(diào)器恢復(fù)數(shù)據(jù)。誤碼率的數(shù)據(jù)顯示，在模擬中。</p>&

61、lt;p>　　您可以通過(guò)打開(kāi)一個(gè)演示，說(shuō)明或模型通過(guò)鍵入MATLAB提示符is95 rev ch detection2的。</p><p>　　IS-95A的反向業(yè)務(wù)信道檢測(cè)演示使用這些庫(kù)塊從CDMA參考模塊庫(kù)：</p><p>　　IS-95A啟通道探測(cè)器</p><p>　　IS-95A馮總沃爾什調(diào)制和蔓延，這是內(nèi)的傳播與調(diào)制子系統(tǒng)</p>

62、<p>　　IS-95A短碼發(fā)生器，這是內(nèi)部的數(shù)據(jù)源子系統(tǒng)</p><p>　　在發(fā)射中使用的組件，數(shù)據(jù)源子系統(tǒng)提供了一個(gè)隨機(jī)數(shù)據(jù)位，通道的數(shù)據(jù)傳輸速率，和短期相和正交擴(kuò)頻信號(hào)的偽噪聲（PN）碼用于源。特別是，IS-95A短碼Generator庫(kù)模塊生成的短PN碼。</p><p>　　傳播和調(diào)制子系統(tǒng)包含沃爾什調(diào)制和蔓延的長(zhǎng)期和短期的PN碼，是負(fù)責(zé)的幾個(gè)街區(qū)。 IS-95A馮總

63、沃爾什調(diào)制和傳播庫(kù)塊包含的IS-95A章啟爆隨機(jī)函數(shù)庫(kù)塊，處理代碼和生成基于長(zhǎng)的代碼和數(shù)據(jù)傳輸速率的輸入框的門控信號(hào)。 IS-95A馮總沃爾什調(diào)制和團(tuán)體也傳播圖書(shū)館大樓6位組輸入數(shù)據(jù)，每組6位到64符號(hào)的Walsh碼地圖，上取樣的4倍，這64個(gè)符號(hào)帶來(lái)的結(jié)果碼片速率，然后蔓延門長(zhǎng)碼的頻符號(hào)。確保此門只為一幀時(shí)間的一小部分（一半的時(shí)間為半速率等）進(jìn)行傳輸。最后，其他部分的蔓延和調(diào)制子系統(tǒng)傳播正交PN碼的數(shù)據(jù)。</p><

64、;p>　　發(fā)射濾波器塊生成I和Q波形。 Q波形由1/2-chip我波形持續(xù)時(shí)間相對(duì)延遲。</p><p>　　瑞利多徑和AWGN信道子系統(tǒng)模擬通過(guò)多條路徑傳播的瑞利衰落信道。復(fù)雜性高斯白噪聲被添加到輸出通道;噪聲代表其他基站都使用相同的頻段產(chǎn)生的干擾。</p><p>　　輸入信號(hào)在接收器部分，首先由接收過(guò)濾塊，它實(shí)現(xiàn)了一個(gè)過(guò)濾器相匹配的發(fā)射濾波器過(guò)濾。在本演示中的過(guò)濾器，旨在最大限

65、度地所需的頻段內(nèi)的信號(hào)功率。</p><p>　　然后，過(guò)濾后的信號(hào)被發(fā)送到IS-95A馮總探測(cè)器庫(kù)塊，其中包含的反向信道RAKE接收機(jī)。 Rake接收機(jī)組成三個(gè)手指耙，設(shè)置不同的延誤長(zhǎng)達(dá)三個(gè)多徑處理。每個(gè)活躍耙手指短PN序列輸入的數(shù)據(jù)進(jìn)行解擴(kuò)，其次是長(zhǎng)碼解擴(kuò)。其次是64 Walsh碼的一整套相關(guān)。在I和Q分量的能量增加，從手指的結(jié)果相加。這是處理由沃爾什的解調(diào)器，從而產(chǎn)生組6位，用于調(diào)制大小決定。沃爾什解調(diào)器輸

66、出既柔軟的的雙極價(jià)值的決定和艱難的決定。兩者都是由數(shù)據(jù)門爆裂隨機(jī)發(fā)生器信號(hào)。</p><p>　　錯(cuò)誤率計(jì)算塊比較傳輸?shù)谋忍睾妥越拥教幚頉Q定，以及生產(chǎn)原料（即無(wú)信道編碼）的誤碼率。在模擬過(guò)程中，這個(gè)比率是顯示在模型窗口。</p><p><b>　　明顯的效果演示。</b></p><p>　　該演示展示了原始誤碼率（BER）為反向通道。誤碼率

67、取決于信道條件和積極RAKE接收機(jī)的手指。由于信號(hào)信噪比或信道條件發(fā)生了改變，這些對(duì)原始誤碼率的影響可以看出，這些不同的條件下運(yùn)行的模型。</p><p><b>　　更改演示參數(shù)</b></p><p>　　本節(jié)提出了一些方法，你可以改變參數(shù)后，你理解了模型在演示。</p><p>　　模擬的時(shí)間。在本演示中的模擬時(shí)間設(shè)定為2秒。因?yàn)樵贗S-

68、95A幀的持續(xù)時(shí)間為0.02秒，這個(gè)模型處理100幀。這給人以足夠的時(shí)間銜接合理的信噪比設(shè)置的BER測(cè)量。要運(yùn)行一個(gè)或長(zhǎng)或短的時(shí)間內(nèi)模擬，從模擬菜單選擇的參數(shù)和改變停止時(shí)間要模擬的幀數(shù)量的0.02倍。</p><p>　　數(shù)據(jù)傳輸速率。要更改的數(shù)據(jù)傳輸速率，數(shù)據(jù)源圖標(biāo)上雙擊。然后雙擊移動(dòng)臺(tái)發(fā)射機(jī)數(shù)據(jù)速率圖標(biāo)和更改數(shù)據(jù)傳輸速率參數(shù)。選擇是全部，一半，四分之一，八分之一的價(jià)格。</p><p>

69、;<b>　　長(zhǎng)碼掩碼</b></p><p>　　要改變長(zhǎng)碼掩碼，對(duì)擴(kuò)頻和調(diào)制圖標(biāo)雙擊。然后雙擊IS-95A馮總沃爾什調(diào)制和蔓延的圖標(biāo)，并輸入一個(gè)長(zhǎng)碼掩碼參數(shù)的新值。這個(gè)參數(shù)可以是任何非負(fù)整數(shù)比242-1。塊使用這個(gè)號(hào)碼的生成代碼的二進(jìn)制表示。長(zhǎng)碼掩碼參數(shù)值，還需要在IS-95A啟通道探測(cè)器圖書(shū)館大樓。實(shí)驗(yàn)使用相同或不同的值，在兩個(gè)街區(qū)。這說(shuō)明了為什么接收機(jī)沒(méi)有信號(hào)解調(diào)不打算，雖然他們?cè)谕?/p>

70、一頻段內(nèi)傳輸。欲了解更多信息，請(qǐng)參閱IS-95A的規(guī)格。</p><p>　　在通道的多普勒頻率。要改變的多普勒頻率，瑞利多徑和AWGN信道下的圖標(biāo)上雙擊。然后雙擊多徑瑞利衰落圖標(biāo)，改變多普勒頻率參數(shù)。在0至200 Hz范圍內(nèi)，合理的多普勒頻率代表的蜂窩移動(dòng)環(huán)境。</p><p>　　信號(hào)信噪比。改變ES /否在AWGN信道塊的通道子系統(tǒng)的參數(shù)。檢測(cè)性能提高了信號(hào)信噪比的增加。</p

71、><p>　　隨機(jī)種子。模擬運(yùn)行與不同的種子，改變一個(gè)或多個(gè)這些初步種子參數(shù)：</p><p><b>　　隨機(jī)數(shù)據(jù)幀發(fā)生器。</b></p><p><b>　　AWGN信道</b></p><p>　　第一項(xiàng)是內(nèi)部的數(shù)據(jù)源子系統(tǒng)和瑞利多徑和AWGN信道子系統(tǒng)內(nèi)的最后兩個(gè)街區(qū)。</p>

72、<p>　　通道路徑和犁耙手指。在衰落信道的路徑和耙手指的數(shù)量或延遲的變化，必須相互對(duì)應(yīng)。要更改電話號(hào)碼或衰落信道的路徑延遲，瑞利多徑和AWGN信道下的圖標(biāo)上雙擊。然后雙擊多徑瑞利衰落圖標(biāo)和更改延遲向量參數(shù)。此參數(shù)向量的長(zhǎng)度是路徑的??數(shù)量和向量元素的測(cè)量每個(gè)路徑在幾秒鐘的延遲。</p><p>　　要更改電話號(hào)碼或延遲耙手指，雙點(diǎn)擊的初始階段，手指啟用圖標(biāo)，改變常量的值參數(shù)。三個(gè)連續(xù)對(duì)這個(gè)長(zhǎng)度六個(gè)載體