無(wu)線(xian)(xian)上網(wang)卡(ka)(ka)是(shi)一(yi)種把(ba)UIM或(huo)SIM卡(ka)(ka)，集成到(dao)一(yi)個類(lei)似于(yu)傳統貓(mao)(mao)的硬件設備，也就(jiu)是(shi)說我(wo)們通過(guo)無(wu)線(xian)(xian)上網(wang)卡(ka)(ka)和以前通過(guo)電話(hua)線(xian)(xian)和貓(mao)(mao)上網(wang)是(shi)一(yi)樣的，都需(xu)要(yao)撥號，只不過(guo)過(guo)去(qu)的貓(mao)(mao)被現在的無(wu)線(xian)(xian)上網(wang)卡(ka)(ka)取代(dai)，過(guo)去(qu)的電話(hua)線(xian)(xian)被手機UIM和SIM卡(ka)(ka)替代(dai)，當我(wo)們想上網(wang)的時候就(jiu)讓終(zhong)端設備通過(guo)這個無(wu)線(xian)(xian)上網(wang)卡(ka)(ka)連接internet即(ji)可(ke)。

無(wu)線上(shang)(shang)網(wang)(wang)卡的(de)工作原理(li)(li)是微波射頻技術(shu)，一般采用(yong)CDMA2000實現(xian)通(tong)(tong)(tong)(tong)訊，也可采用(yong)GPRS通(tong)(tong)(tong)(tong)訊。它遵循802.11g標(biao)準，通(tong)(tong)(tong)(tong)過無(wu)線傳(chuan)輸，由無(wu)線接(jie)(jie)入點發(fa)(fa)出信號，用(yong)無(wu)線上(shang)(shang)網(wang)(wang)卡接(jie)(jie)受和發(fa)(fa)送數(shu)據。按(an)照IEEE802.11協(xie)議，無(wu)線上(shang)(shang)網(wang)(wang)卡卡分為媒體訪問控(kong)制(zhi)（MAC）層(ceng)(ceng)和物理(li)(li)層(ceng)(ceng)（PHY Layer）。物理(li)(li)層(ceng)(ceng)能夠實現(xian)無(wu)線電信號的(de)接(jie)(jie)收與(yu)發(fa)(fa)射，它與(yu)無(wu)線上(shang)(shang)網(wang)(wang)卡硬件(jian)中的(de)擴頻通(tong)(tong)(tong)(tong)信機(ji)相對應。物理(li)(li)層(ceng)(ceng)提供空閑信道估計(ji)CCA信息給MAC層(ceng)(ceng)，以便決定是否可以發(fa)(fa)送信號，通(tong)(tong)(tong)(tong)過MAC層(ceng)(ceng)的(de)控(kong)制(zhi)來實現(xian)無(wu)線網(wang)(wang)絡的(de)CCSMA/CA協(xie)議，而MAC-PHY子(zi)層(ceng)(ceng)主要實現(xian)數(shu)據的(de)打包與(yu)拆(chai)包，把必要的(de)控(kong)制(zhi)信息放在(zai)數(shu)據包的(de)前面，從而實現(xian)上(shang)(shang)網(wang)(wang)。