無(wu)(wu)線上(shang)網(wang)(wang)(wang)卡(ka)(ka)是(shi)一種把UIM或SIM卡(ka)(ka)，集成到一個類(lei)似于傳統貓的硬件設備，也(ye)就是(shi)說我們通(tong)過(guo)(guo)無(wu)(wu)線上(shang)網(wang)(wang)(wang)卡(ka)(ka)和以前(qian)通(tong)過(guo)(guo)電話(hua)線和貓上(shang)網(wang)(wang)(wang)是(shi)一樣(yang)的，都需要撥(bo)號，只不過(guo)(guo)過(guo)(guo)去(qu)的貓被現(xian)在(zai)的無(wu)(wu)線上(shang)網(wang)(wang)(wang)卡(ka)(ka)取(qu)代，過(guo)(guo)去(qu)的電話(hua)線被手(shou)機UIM和SIM卡(ka)(ka)替代，當我們想上(shang)網(wang)(wang)(wang)的時(shi)候就讓(rang)終端設備通(tong)過(guo)(guo)這個無(wu)(wu)線上(shang)網(wang)(wang)(wang)卡(ka)(ka)連(lian)接internet即(ji)可。

無(wu)(wu)線(xian)(xian)(xian)上(shang)(shang)網卡(ka)的(de)(de)(de)(de)(de)(de)工(gong)作原理(li)是微波射(she)頻(pin)技術，一般采(cai)用CDMA2000實(shi)(shi)(shi)現(xian)(xian)(xian)通(tong)(tong)(tong)(tong)訊，也可(ke)(ke)采(cai)用GPRS通(tong)(tong)(tong)(tong)訊。它(ta)遵(zun)循802.11g標(biao)準，通(tong)(tong)(tong)(tong)過無(wu)(wu)線(xian)(xian)(xian)傳輸(shu)，由無(wu)(wu)線(xian)(xian)(xian)接(jie)入點發(fa)(fa)出信(xin)(xin)號，用無(wu)(wu)線(xian)(xian)(xian)上(shang)(shang)網卡(ka)接(jie)受和發(fa)(fa)送(song)數據(ju)。按(an)照IEEE802.11協議，無(wu)(wu)線(xian)(xian)(xian)上(shang)(shang)網卡(ka)卡(ka)分為媒體(ti)訪問控制（MAC）層和物(wu)理(li)層（PHY Layer）。物(wu)理(li)層能(neng)夠(gou)實(shi)(shi)(shi)現(xian)(xian)(xian)無(wu)(wu)線(xian)(xian)(xian)電信(xin)(xin)號的(de)(de)(de)(de)(de)(de)接(jie)收與發(fa)(fa)射(she)，它(ta)與無(wu)(wu)線(xian)(xian)(xian)上(shang)(shang)網卡(ka)硬件(jian)中(zhong)的(de)(de)(de)(de)(de)(de)擴頻(pin)通(tong)(tong)(tong)(tong)信(xin)(xin)機相(xiang)對應。物(wu)理(li)層提(ti)供空閑信(xin)(xin)道(dao)估計CCA信(xin)(xin)息(xi)給MAC層，以便決定是否可(ke)(ke)以發(fa)(fa)送(song)信(xin)(xin)號，通(tong)(tong)(tong)(tong)過MAC層的(de)(de)(de)(de)(de)(de)控制來(lai)實(shi)(shi)(shi)現(xian)(xian)(xian)無(wu)(wu)線(xian)(xian)(xian)網絡的(de)(de)(de)(de)(de)(de)CCSMA/CA協議，而MAC-PHY子(zi)層主要(yao)(yao)實(shi)(shi)(shi)現(xian)(xian)(xian)數據(ju)的(de)(de)(de)(de)(de)(de)打包與拆包，把必要(yao)(yao)的(de)(de)(de)(de)(de)(de)控制信(xin)(xin)息(xi)放在數據(ju)包的(de)(de)(de)(de)(de)(de)前面，從而實(shi)(shi)(shi)現(xian)(xian)(xian)上(shang)(shang)網。