無線(xian)(xian)(xian)(xian)上(shang)網卡(ka)是(shi)一種把UIM或SIM卡(ka)，集成到(dao)一個(ge)類似于傳統(tong)貓的硬件設(she)備，也就(jiu)是(shi)說(shuo)我們通(tong)(tong)過(guo)無線(xian)(xian)(xian)(xian)上(shang)網卡(ka)和以前通(tong)(tong)過(guo)電話(hua)線(xian)(xian)(xian)(xian)和貓上(shang)網是(shi)一樣的，都需(xu)要撥號，只不過(guo)過(guo)去(qu)的貓被現在的無線(xian)(xian)(xian)(xian)上(shang)網卡(ka)取(qu)代，過(guo)去(qu)的電話(hua)線(xian)(xian)(xian)(xian)被手機UIM和SIM卡(ka)替代，當我們想上(shang)網的時候就(jiu)讓終(zhong)端(duan)設(she)備通(tong)(tong)過(guo)這個(ge)無線(xian)(xian)(xian)(xian)上(shang)網卡(ka)連(lian)接internet即可。

無(wu)線(xian)(xian)上(shang)(shang)網(wang)卡(ka)的(de)(de)工作原理是微波(bo)射頻技(ji)術，一般(ban)采(cai)用(yong)(yong)CDMA2000實(shi)現通訊，也可采(cai)用(yong)(yong)GPRS通訊。它遵循802.11g標準，通過無(wu)線(xian)(xian)傳輸，由無(wu)線(xian)(xian)接入點發(fa)出信(xin)(xin)(xin)(xin)號(hao)，用(yong)(yong)無(wu)線(xian)(xian)上(shang)(shang)網(wang)卡(ka)接受和發(fa)送數(shu)據。按(an)照IEEE802.11協(xie)議，無(wu)線(xian)(xian)上(shang)(shang)網(wang)卡(ka)卡(ka)分為媒體訪(fang)問控(kong)制（MAC）層(ceng)和物(wu)理層(ceng)（PHY Layer）。物(wu)理層(ceng)能夠實(shi)現無(wu)線(xian)(xian)電(dian)信(xin)(xin)(xin)(xin)號(hao)的(de)(de)接收與(yu)發(fa)射，它與(yu)無(wu)線(xian)(xian)上(shang)(shang)網(wang)卡(ka)硬件中的(de)(de)擴頻通信(xin)(xin)(xin)(xin)機相對應。物(wu)理層(ceng)提供(gong)空閑信(xin)(xin)(xin)(xin)道(dao)估計CCA信(xin)(xin)(xin)(xin)息給MAC層(ceng)，以便決定是否可以發(fa)送信(xin)(xin)(xin)(xin)號(hao)，通過MAC層(ceng)的(de)(de)控(kong)制來(lai)實(shi)現無(wu)線(xian)(xian)網(wang)絡(luo)的(de)(de)CCSMA/CA協(xie)議，而MAC-PHY子(zi)層(ceng)主要實(shi)現數(shu)據的(de)(de)打包(bao)與(yu)拆包(bao)，把必要的(de)(de)控(kong)制信(xin)(xin)(xin)(xin)息放在數(shu)據包(bao)的(de)(de)前面(mian)，從而實(shi)現上(shang)(shang)網(wang)。