碼分多址通信系統(tǒng)、擴(kuò)頻通信外文翻譯-其他專業(yè)(存儲(chǔ)版)
【正文】 語音壓縮等多項(xiàng)新技術(shù)，更加適用于計(jì)算機(jī)網(wǎng)絡(luò)以及數(shù)字化的語音、圖像信息傳輸。相比之下，頻分多址（ FDMA）由頻率劃分。 CDMA 還耐干擾。像窄帶干擾 ，這將導(dǎo)致只有一小數(shù)據(jù)丟失，并且可以被克服。在 FDMA 和 TDMA 系統(tǒng)中頻率規(guī)劃是重要的考慮因素。這與其他蜂窩系統(tǒng)的硬切換不同。 。軟切換允許移動(dòng)電話同時(shí)與兩個(gè)或更多個(gè)用戶通信。 RAKE 接收器整合多個(gè)相關(guān)器的信息，每一個(gè)調(diào)諧到不同的路徑延遲，產(chǎn)生一個(gè)比相關(guān)的簡(jiǎn)單調(diào)整，以最強(qiáng)的信號(hào)路徑延遲接收的信號(hào)更強(qiáng)的信號(hào)版本。 CDMA 信號(hào)也耐多徑衰落。異步 CDMA 有一些內(nèi)置的隱私級(jí)別，因?yàn)樾盘?hào)傳 播使用偽隨機(jī)碼，這個(gè)代碼使擴(kuò)頻信號(hào)出現(xiàn)隨機(jī)或有噪聲性能。這個(gè)概念被稱為多址接入。 由于擴(kuò)頻通信又采取了相關(guān)接收這一技術(shù)，信號(hào)發(fā)送功率極低（＜ 1W，一般為1~100mW），且可工作在信道噪聲和熱噪聲背景中，易于在同一地區(qū)重復(fù)使用同一頻率，也可以在現(xiàn)今各種窄帶通信共享同一頻率資源。 擴(kuò)頻通信技術(shù)的基本概念 擴(kuò)頻通信的基本特點(diǎn)：其傳輸信息所用信號(hào)的帶寬（ W）遠(yuǎn)大于信息本 身實(shí)際所需的最?。ㄓ行В挘?F? ），其比值稱為處理增益 FWGP ?? / 眾所周知，在普通的調(diào)幅、調(diào)頻或者脈沖編碼調(diào)制通信中， PG 值一般都在十多倍范圍內(nèi)，稱為“窄帶通信”，而擴(kuò)頻通信的 PG 值高達(dá)幾百甚 至幾千倍，可以稱為“寬帶通信”。 chirp frequency system is a linear extension of the process of change. Combination of a number of ways of hybrid systems are often applied. The most important measure pf spreadspectrum system is an indicator of spreading gain, also known as processing gain. It is precisely because of the spread spectrum system itself with its performance characteristics with a series of advantages. Code division multiple access Code division multiple access (CDMA) is a channel access method used by various radio munication technologies. It should not be confused with the mobile phone standards called cdmaOne, CDMA2021(the 3G evolution of cdmaOne) and WCDMA (the 3Gstandard used by GSM carrier), which are often referred to as simply CDMA, and use CDMA as an underlying channel access method. One of the concepts in data munication is the idea of allowing several transmitters to send information simultaneously over a signal munication channel. This allows several users to share a band of frequencies (see bandwidth). This concept is called multiple access. CDMA employs spreadspectrum technology and a special coding scheme( where each transmitter is assigned a code) to allow multiple user to be multiplexed over the same physical channel. By contrast, time division multiple access (FDMA) divides it by frequency. CDMA is a form of spreadspectrum signaling, since the modulated coded signal has a much higher data bandwidth than the data being municated. Spreadspectrum characteristic of CDMA Most modulation schemes try to minimize the bandwidth of this signal since bandwidth is a limited resource. However, spread spectrum use a transmission bandwidth that is several orders of magnitude greater than the minimum required signal bandwidth. One of the initial reasons for doing this was military applications including guidance and munication systems. These system were designed using spread spectrum because if its security and resistance to jamming. Async hronous CDMA has some level of privacy built in because the signal is spread using a pseudorandom code。 TH is the data transmission time slot is a pseudorandom。正是因?yàn)閿U(kuò)頻系統(tǒng)本身具有的特征使其性能具有一系列的優(yōu)勢(shì)。為此，世界各地都設(shè)立了頻譜管理機(jī)構(gòu)，用戶只能使用申請(qǐng)獲得的頻率， 依靠頻率劃分來防止信道之間的干擾。這允許多個(gè)用戶共享一個(gè)頻帶（見帶寬）。這些系統(tǒng)的設(shè)計(jì)使用，因?yàn)槠浒踩院涂垢蓴_擴(kuò)頻。卷積編碼和交織可以用來協(xié)助回收這丟失的數(shù)據(jù)。 一些 CDMA 設(shè)備使用 RAKE 接收器，它利用多
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