無線(xian)(xian)上(shang)(shang)網(wang)(wang)卡(ka)(ka)是一種把UIM或SIM卡(ka)(ka),集成到一個(ge)類似于傳統貓(mao)的(de)硬件設備,也(ye)就是說我(wo)(wo)們(men)(men)通(tong)過(guo)無線(xian)(xian)上(shang)(shang)網(wang)(wang)卡(ka)(ka)和(he)以前通(tong)過(guo)電(dian)話(hua)線(xian)(xian)和(he)貓(mao)上(shang)(shang)網(wang)(wang)是一樣(yang)的(de),都需(xu)要撥號,只(zhi)不過(guo)過(guo)去(qu)的(de)貓(mao)被現在(zai)的(de)無線(xian)(xian)上(shang)(shang)網(wang)(wang)卡(ka)(ka)取(qu)代(dai)(dai),過(guo)去(qu)的(de)電(dian)話(hua)線(xian)(xian)被手機UIM和(he)SIM卡(ka)(ka)替(ti)代(dai)(dai),當我(wo)(wo)們(men)(men)想上(shang)(shang)網(wang)(wang)的(de)時候(hou)就讓終(zhong)端(duan)設備通(tong)過(guo)這(zhe)個(ge)無線(xian)(xian)上(shang)(shang)網(wang)(wang)卡(ka)(ka)連(lian)接internet即可。
無(wu)線(xian)(xian)上網(wang)卡(ka)的(de)工作原理是微波(bo)射(she)頻技術,一般(ban)采用(yong)CDMA2000實(shi)現(xian)通(tong)訊,也可(ke)采用(yong)GPRS通(tong)訊。它(ta)遵循802.11g標準,通(tong)過無(wu)線(xian)(xian)傳輸(shu),由無(wu)線(xian)(xian)接(jie)入點發(fa)出(chu)信號,用(yong)無(wu)線(xian)(xian)上網(wang)卡(ka)接(jie)受和(he)發(fa)送數(shu)據(ju)。按照IEEE802.11協議,無(wu)線(xian)(xian)上網(wang)卡(ka)卡(ka)分(fen)為媒體訪(fang)問控制(MAC)層(ceng)和(he)物(wu)理層(ceng)(PHY Layer)。物(wu)理層(ceng)能夠(gou)實(shi)現(xian)無(wu)線(xian)(xian)電信號的(de)接(jie)收與發(fa)射(she),它(ta)與無(wu)線(xian)(xian)上網(wang)卡(ka)硬件中的(de)擴頻通(tong)信機相(xiang)對應。物(wu)理層(ceng)提(ti)供空閑信道估(gu)計CCA信息給MAC層(ceng),以便(bian)決定是否(fou)可(ke)以發(fa)送信號,通(tong)過MAC層(ceng)的(de)控制來實(shi)現(xian)無(wu)線(xian)(xian)網(wang)絡(luo)的(de)CCSMA/CA協議,而(er)MAC-PHY子層(ceng)主要實(shi)現(xian)數(shu)據(ju)的(de)打包(bao)(bao)與拆包(bao)(bao),把必(bi)要的(de)控制信息放在數(shu)據(ju)包(bao)(bao)的(de)前面(mian),從而(er)實(shi)現(xian)上網(wang)。