Modulation vs Multiplexing
Kev hloov pauv thiab kev sib tw yog ob lub ntsiab lus siv hauv kev sib txuas lus txhawm rau ua kom muaj kev sib txuas lus. Modulation yog qhov sib txawv ntawm cov khoom ntawm kev ua haujlwm teeb liab xa cov ntaub ntawv, whereas multiplexing yog ib txoj hauv kev sib txuas ntau lub teeb liab. Ob qhov kev ua haujlwm yog qhov tseem ceeb rau kev sib txuas lus zoo.
Modulation
Modulation yog lub npe hu ua qhov sib txawv ntawm cov khoom ntawm lub sijhawm waveform, hu ua 'carrier', raws li lub teeb liab uas nqa cov ntaub ntawv peb xav tau xa. Cia peb hais, peb yuav tsum xa me ntsis ntu (10100) los ntawm kev sib txuas lus wireless. Txhawm rau xa cov ntu me me no, peb tuaj yeem siv lub teeb liab ntau zaus (cia peb hais 40MHz), nrog rau qhov sib txawv ntawm cov teeb liab ntawm ob theem. Peb tuaj yeem siv cov ntawv sau, uas yog '1' los sawv cev siab amplitude thiab '0' los sawv cev qis amplitude. Hom kev hloov kho no yog hu ua 'amplitude modulation' (AM). Ntawm qhov tod tes, peb tuaj yeem sib txawv me ntsis qhov zaus. Piv txwv li, peb tuaj yeem xa 40MHz rau '1' thiab 41MHz rau '0'. Ntawm no, peb tab tom sib txawv qhov zaus raws li lub teeb liab thawj, thiab hom kev hloov kho no hu ua 'frequency modulation' (FM). Lwm qhov sib txawv yog theem ntawm lub teeb liab. Nws yog lub npe hu ua 'phase modulation' (PM).
Qee zaum, ob qhov tsis sib xws. Piv txwv li, nyob rau hauv QAM (Quadrature Amplitude Modulation), ob qho tib si lub amplitude thiab theem yog sib txawv nyob rau hauv thiaj li yuav ua tau ib tug ntau dua ntawm cov theem los sawv cev rau lub teeb liab. Tau txais qhov qub teeb liab los ntawm lub teeb liab modulated hu ua demodulation. Cov teeb liab yog modulated ntawm lub transmitter thiab demodulated ntawm tus receiver.
Multiplexing
Multiplexing yog xav tau thaum peb yuav tsum sib txuas thiab xa ntau lub teeb liab uas nqa cov ntaub ntawv hla ib qho nruab nrab sib koom. Piv txwv li, ntau lub xov tooj txuas nrog ib kab thiab tswj kev siv multiplexing.
Cia peb hais cov neeg xa xov A1, A2, A3, A4 yuav tsum xa plaub me ntsis (hais 100, 111, 101, thiab 110) ib txhij rau cov txais B1, B2, B3, B4 los ntawm ib qho channel. Txhawm rau xa qhov no, peb tuaj yeem sib tov lawv cov kwj me ntsis rau hauv ib lub kwj deg los ntawm kev noj txhua tus neeg xa khoom thawj zaug, thib ob thiab thib peb cov khoom sib npaug. Ua ntej peb tuaj yeem nqa txhua tus xa ntawv thawj me ntsis li 1111 (ntawm qhov kev txiav txim ntawm A1, A2, A3, A4), tom qab ntawd thib ob (0101) thiab zaum kawg thib peb (0110). Li no peb tuaj yeem tsim cov kwj ua ke 1111 0101 0110. Cov txheej txheem no hu ua multiplexing. Ntawm tus txais, cov kwj dej no tuaj yeem faib ua plaub kwj thiab xa mus rau B1, B2, B3 thiab B4 raws li qhov kev txiav txim paub. Cov txheej txheem no hu ua de-multiplexing.
Muaj ntau hom kev txwv uas tuaj yeem sib koom. Hauv Time Division Multiplexing (TDM), lub sij hawm axis tau sib koom, whereas nyob rau hauv Frequency Division Multiplexing (FDM), zaus band yog sib koom.
Qhov txawv ntawm Modulation thiab Multiplexing yog dab tsi?
1. Modulation yog siv lub teeb liab ua haujlwm los xa cov ntaub ntawv, whereas multiplexing is a way of combining multiple signals.
2. Hauv kev hloov pauv nthwv dej muaj ntau yam sib txawv txhawm rau sawv cev rau lub teeb liab, whereas nyob rau hauv multiplexing yoj parameters tau sib koom rau ntau txoj kev.
3. Feem ntau, kev hloov pauv yog ua tiav tom qab multiplexing.
