Ntau tus neeg muas zaub nug thaum xaiv ibtseem ceeb video transmitter- Dab tsi yog qhov txawv ntawmCOFDM wireless video transmitterthiab OFDM video transmitter?
COFDM yog Coded OFDM, Hauv blog no peb yuav tham txog nws los pab koj nrhiav seb qhov kev xaiv twg yuav zoo dua koj daim ntawv thov.
1. OFDM
OFDM thev naus laus zis faib cov channel muab rau hauv ntau qhov chaw orthogonal sub-channels hauv qhov ntau zaus.Ib lub subcarrier yog siv rau kev hloov kho ntawm txhua lub subchannel, thiab txhua tus subcarrier raug xa mus ua ke.Nyob rau hauv txoj kev no, txawm tias tag nrho cov channel tsis yog tiaj tus thiab ntau zaus xaiv.Tab sis txhua qhov subchannel yog qhov tiaj tus.Narrowband kis tau tus mob yog ua nyob rau hauv txhua lub sub-channel, thiab lub teeb liab bandwidth yog me dua lub coj bandwidth ntawm lub channel.Yog li ntawd, kev cuam tshuam ntawm cov teeb liab waveforms tuaj yeem raug tshem tawm ntau.
Txij li cov neeg nqa khoom ntawm txhua qhov sub-channel yog orthogonal rau ib leeg hauv OFDM system.Lawv spectrums sib tshooj.Qhov no tsis tsuas yog txo qhov kev cuam tshuam ntawm kev sib koom ua ke ntawm cov neeg nqa khoom, tab sis kuj tseem txhim kho kev siv spectrum.
2. COFDM
COFDMis Coded Orthogonal Frequency Division Multiplexing, uas txhais tau tias
ua ntej OFDM kev hloov kho, cov lej digital kwj yog encoded.
Qhov Coded no ua dab tsi?Nws yog channel coding (qhov chaw coding yog los daws qhov teeb meem ntawm kev ua tau zoo, thiab channel coding yog los xyuas kom meej qhov kev ntseeg tau ntawm kev sib kis).
Txoj kev tshwj xeeb yog:
2.1.Forward yuam kev kho (FEC)
Piv txwv li, 100 cov ntaub ntawv yuav tsum tau hloov khoraukis tauhauv.Ua ntej hloov nws mus rau 200 khoom,.Thaum lub teeb liab tau txais, txawm tias muaj teeb meem nrog kev sib kis ntawm 100 khoom, cov ntaub ntawv raug tseem tuaj yeem demodulated.Nyob rau hauv luv luv, nws yog ntxiv redundancy ua ntej modulation los txhim kho kev ntseeg tau ntawm kev sib kis.Qhov no yog hu ua Internal Error Correction (FEC) hauv COFDM systems.Thiab kuvt yog ib qho tseem ceeb parameter ntawm COFDM system.
2.2.Guard Interval
Flos yog lub hom phiaj ntawm solvhauvntau-kev teeb meemuas yogcov teeb liab kis tau mus txog qhov kawg tau txais los ntawm ntau txoj kev sib kis. ALub sijhawm tiv thaiv yog muab tso rau ntawm cov ntaub ntawv xa tawm.
3. Cov lus xaus
Qhov sib txawv ntawm COFDM thiab OFDM yog qhov kev ua yuam kev kho cov lej thiab cov kev tiv thaiv ib ntus ntxiv ua ntej orthogonal modulation kom teeb liab kis tau zoo.
OFDM daws cov channel xaiv fading hauv ntau-txoj kev ib puag ncig zoo, tab sis nws tseem tsis tau kov yeej cov channel tiaj tus fading.
COFDM ua rau lub fading ntawm txhua chav tsev code teeb liab thaum lub sij hawm kis tau tus mob raws li statistically ywj siab los ntawm coding, yog li tshem tawm cov kev cuam tshuam ntawm ca fading thiab Doppler zaus hloov.
4.Kev siv OFDM thiab COFDM
COFDM yog qhov tsim nyog rau kev xa xov wireless thaum lub sijhawmkev kub ceevtsiv.Xws li Hd wtsis xav li casttus ransmittervehiclemunt, nkojmesh kev sib txuas lus, nyoob hoom qav taubCofdm Hd Transmitter thiablongrnpau tawsdronevideottus ransmitter.
COFDM kuj muaj zog nlos muaj peev xwm.Nws yog qhov tsim nyog rau daim ntawv thov nyob rau hauv qhov chaw tsis pom thiab muaj kev cuam tshuam xws li thaj chaw hauv nroog, suburbs, thiab vaj tse, thiab nthuav tawm cov peev xwm "diffraction" thiab "kev nkag mus" zoo heev.
OFDM ua kom muaj kev siv tau zoo ntawm spectrum thiab nws tuaj yeem tiv taus qhov kev xaiv ntau zaus, uas ib txwm siv hauv LTE thiab wifi network.
Post lub sij hawm: Jun-12-2023
