CDMA vs LTE Network Technology
CDMA (Code Division Multiple Access) thiab LTE (Long Term Evolution) yog qhov sib txawv ntawm qhov kev txiav txim siab tias CDMA yog ntau yam kev siv thev naus laus zis thaum LTE yog cov qauv kev sib txuas lus hauv xov tooj tom ntej (4G). Ntau yam kev siv thev naus laus zis tau siv hauv cov xov tooj ntawm tes txhawm rau txhawb nqa ntau tus neeg siv ib lub xov tooj ntawm tes nrog cov peev txheej tsawg. TDMA, FDMA yog thawj cov thev naus laus zis zoo li no thiab tom qab ntawd CDMA tau tsim, uas siv tag nrho cov peev txheej rau txhua tus neeg hauv lub network. LTE yog txhais los ntawm 3GPP (3rd Generation Partnership Project) txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau ua rau muaj kev pheej hmoo ntawm cov kab mob, LTE yuav tsum tau ua raws li cov lus pom zoo los ntawm cov kws tshaj lij kev lag luam.
CDMA
Qhov no yog cov txheej txheem kev nkag tau siv ntau yam siv los ntawm kev sib txuas lus uas cov txheej txheem TDMA thiab FDMA paub zoo tau ua ke los tsim cov txheej txheem tshiab thiab tuaj yeem suav tau tias yog ib qho kev sib txuas ntawm cov thev naus laus zis saum toj no. Qhov tseem ceeb tshaj plaws ntawm cov txheej txheem yog tias kev sib txuas lus ruaj ntseg tau ua tiav los ntawm kev siv lub suab nrov nrov rau txhua tus neeg siv khoom thiab cov txheej txheem no tseem hu ua kev sib txuas ncaj qha kis spectrum technology. Nyob rau hauv cov ntaub ntawv no nws yog tiav los ntawm kev hloov cov thawj digital teeb liab ncaj qha mus rau ntau dua zaus los ntawm kev siv lub pseudo random suab nrov teeb liab. Raws li qhov tshwm sim ntawm qhov ncaj qha hloov dua siab tshiab ntawm lub teeb liab nyob rau hauv ntau zaus lub spectrum ntawm tus thawj teeb liab yog flattened (kis) nyob rau hauv lub zaus domain li no lub npe kis spectrum. Raws li qhov tshwm sim ntawm qhov teeb liab pom tau zoo li lub suab nrov tsis muaj qhov tseeb pseudo-suab nrov code ntawm cov receivers kawg. Qhov no tau tso cai nce tus naj npawb ntawm cov neeg siv khoom hauv ib lub xov tooj ntawm tes thiab muaj kev sib txuas lus ruaj ntseg dua.
LTE
LTE tuaj yeem suav tau tias yog 4G ntawm cov qauv kev sib txuas lus hauv xov tooj uas yog ib txoj haujlwm ntawm 3GPP (kev sib koom ua ke thib peb) tau pib rau xyoo 2004 thiab ua tiav nws tso tawm 8 xyoo 2009. Cov xov tooj cua hauv qab no tau siv MIMO (Multiple Input. Ntau Qhov Tso Tawm), OFDMA (Orthogonal Frequency Division Multiple Access) thiab SC-FDMA (Ib leeg Tus Neeg Mob FDMA).
Los ntawm kev siv MIMO hauv kev sib txuas lus hauv xov tooj nws txhim kho lub xov tooj cua channel muaj peev xwm hauv kev sib txuas lus xov tooj ntawm tes yog li pom zoo los ntawm 3GPP txhawm rau ua tiav cov ntaub ntawv siab. OFDMA yog cov cuab yeej siv ntau yam siv nrog LTE thiab txhawm rau ua tiav qhov kev sib txuas ib puag ncig 100 Mbps ntau yam thiab nws yog cov txheej txheem zoo tshaj plaws tam sim no muaj vim nws cov qauv txais tau yooj yim thiab kev ua haujlwm ntawm spectral. LTE muaj downlink ncov tus nqi nyob ib ncig ntawm 360 Mbps thaum uplink yog nyob ib ncig ntawm 86 Mbps nrog ib tug channel bandwidth ntawm 20 MHz uas yog scalable los ntawm 1.25MHz mus rau upwards. Tsis tas li ntawd lub sij hawm mus txawv tebchaws los ntawm lub hauv paus chaw nres tsheb mus rau lub chaw nres tsheb txawb tau txhim kho nrog 10 ms ntau.
SC FDMA zoo ib yam li OFDMA tshwj tsis yog tias nws siv qee qhov kev ua DFT ntxiv thiab tam sim no qhov no tau pom zoo los ntawm 3GPP kom siv los ua cov txheej txheem kev sib txuas lus uplink vim kev xa hluav taws xob ua haujlwm tau zoo thiab tus nqi hais txog cov khoom siv txawb.
Qhov txawv ntawm CDMA thiab LTE
• CDMA yog ntau yam kev siv thev naus laus zis siv hauv kev sib txuas lus (3G) thiab LTE yog 4th tiam qauv kev sib txuas lus mobile.
• CDMA variations yog siv nyob rau hauv 3G thev naus laus zis xws li CDMA ib qho, CDMA 2000 (1.25 MHz bandwidth), WCDMA (5 MHz bandwidth) kom ua tiav cov ntaub ntawv ntau dua thiab siv tau zoo hauv kev sib txuas lus thoob ntiaj teb.
• LTE tab tom yuav siv OFDMA raws li cov txheej txheem nkag mus rau ntau yam txhawm rau txhawm rau ua kom cov ntaub ntawv nyob ib puag ncig 350 Mbps (downlink) thiab CDMA txheej txheem muaj ntau tus qauv sib txuas rau ntau tus nqi cov ntaub ntawv xws li CDMA 1 muaj 144Kbps thiab CDMA 1 Ev (CDMA ib qho kev hloov pauv) sib raug rau 2 Mbps.
