【正文】 so far, eachsuccessive generation more reliable and flexible than the，已先后出現(xiàn)了三代移動電話，而且一代比一代更可靠、更靈活。 on the heels of analog and digital technology,the Third Generation will be digital mobile multimediaoffering broadband mobile munications with voice , video,graphics, audio and other ，第三代將會是數(shù)字移動多媒體技術(shù)。 are all derivatives of the World Wide Web aimed atconnecting different munities of ，其目的在于能與不同的對象進(jìn)行聯(lián)系?！?Generation（3G）facilitates several newapplications that have not previously been readily availableover mobile networks due to the limitations in datatransmission 促進(jìn)了一些新的應(yīng)用，而這些應(yīng)用在先前的移動通信網(wǎng)上由于數(shù)據(jù)傳輸速率的限制不太容易實(shí)現(xiàn)。BSC基站控制器MSC移動交換中心PSTN 公共交換的電話網(wǎng)絡(luò) speed and rapidity with which the personalmunications revolution takes place is, unlike fixedtransmission systems, highly dependent on technology andmunications ，個人通信的快速發(fā)展在很大程度上依賴于技術(shù)和通信標(biāo)準(zhǔn)的發(fā)展。 second generation is very much dominated by the standardfirst set out in Europe by the Group Special Mobile(GSM)mittee, which was designed as a global mobilemunications 訂的標(biāo)準(zhǔn)所決定的，被設(shè)計(jì)成為一種全球移動通信系統(tǒng)。 transmits light rather than electronic signalseliminating the problem of electrical ，因此避免了電干擾的問題。 NICs are internal, with the card fitting into anexpansion slot inside the ，這張卡插入到計(jì)算機(jī)內(nèi)部的一個擴(kuò)展槽中。 a signal loses strength as it passes along a cable,it is often necessary to boost the signal with a device calleda ，所以需要一個設(shè)備來放大信號，這個設(shè)備就是通常所說的中繼器。 router translates information from one network to another。路由器基于目的地地址和源地址來為消息選擇最好的路徑。一 Web has bee a very popular resource since it firstbecame possible ??自從1993年萬維網(wǎng)可以在一個世界范圍的電腦網(wǎng)絡(luò)因特網(wǎng)上瀏覽圖片和其他多媒體后，它就變成了一個非常流行的資源。3.●The World Wide Web is the part of the internet that letsyou see information using words??..萬維網(wǎng)就是因特網(wǎng)中通過文字、圖片、聲音、顏色來得到信息的那個部分。 World Wide Web has been the most popular developmentof the internet ???萬維網(wǎng)已經(jīng)成為因特網(wǎng)發(fā)展最快的一部分，他就像是由數(shù)百萬頁面組成的一本巨大的電子書，這些頁面就稱為主頁。 many methods focus on ordering information orputting information in a hierarchy, hypertext focuses oncreating relationships between ，而不像其他許多方法關(guān)注于把信息排序或是分層次(hypertext markup language)describes a web page,which is stored in a plain text file with HTM or HTML fileextension..HTML用來生成一個網(wǎng)頁，他們被保存在以HTM或HTML為文件擴(kuò)展名的純文本文件里。二 detection and correction are required incircumstance where errors cannot be ，如一些錯誤是不可接受的時候需要檢錯糾錯功能 properties of the signal, such as form and intensity,must be such that they are :(1)capable of being propagatedthrough the transmission system ,and(2)interpretable asdata at the ，例如他的形態(tài)和強(qiáng)度必須是：（1）能夠經(jīng)過傳輸系統(tǒng)的；（2）能夠?yàn)榻邮斩私邮詹⒆R別的。 formatting has to do with an agreement between twoparties as to as form of the data to be exchanged ortransmitted, such as the binary code for ，這個協(xié)議就是關(guān)于數(shù)據(jù)的交換和傳輸形式兩方面的，例如他的形式是字符的二進(jìn)制編碼。接收器將在r(t)和它的傳輸媒介的基礎(chǔ)上對原始信號s(t)進(jìn)行測試，并產(chǎn)生一個順序脈沖g(t)。 WANs have been implemented using one of twotechnologies: circuit switching and packet switching???傳統(tǒng)上，WANs實(shí)施使用兩項(xiàng)技術(shù)當(dāng)中的一個：電路交換和包交換。 personal puter is connected to some transmissionmedium, such as local network or a telephone line, by an I|