- Nyob rau hauv nruab nrab ntawm lub xyoo pua xeem, cov neeg tau thov kom muaj ntau txoj kev sib txuas lus nrog ntau zaus band aliasing, xaiv kev sib nrig sib orthogonal cab kuj zaus raws li subcarriers, uas yog qhov peb hu ua COFDM. Qhov no "orthogonality" yog hais txog kev sib raug zoo lej ntawm tus cab kuj zaus. Raws li qhov kev xav no, COFDM tsis tuaj yeem siv tag nrho cov channel bandwidth, tab sis kuj tsis txhob siv high-speed equalization thiab anti-burst suab tsis raug. COFDM yog ib qho kev sib txuas lus tshwj xeeb ntawm ntau tus neeg nqa khoom. Cov ntaub ntawv ntws ntawm ib tus neeg siv ib leeg yog serially / parallel hloov dua siab tshiab rau hauv ntau tus lej qis qis, thiab txhua tus kwj dej yog xa nrog subcarrier. Es tsis txhob siv bandpass lim cais subcarriers, COFDM siv Fast Fourier Transform (FFT) xaiv waveforms uas nyob twj ywm orthogonal txawm aliasing.
- COFDM technology belongs rau multi-carrier modulation (Multi-Carrier Modulation, MCM) technology. Qee cov ntaub ntawv sib xyaw OFDM thiab MCM, uas yeej tsis nruj txaus. MCM thiab COFDM feem ntau yog siv hauv wireless channels. Qhov txawv ntawm lawv yog tias COFDM thev naus laus zis tshwj xeeb yog hais txog kev faib cov channel rau hauv orthogonal sub-channels, uas muaj tus nqi siab siv channel; thaum MCM tuaj yeem ua ntau txoj kev faib channel.
- Kev taw qhia ntawm COFDM thev naus laus zis tiag tiag yog txhawm rau txhim kho kev siv spectrum ntawm cov cab kuj, los yog txhim kho cov kev hloov kho ntawm ntau tus neeg nqa khoom. Nws tus yam ntxwv yog hais tias txhua tus sub-carrier yog orthogonal rau ib leeg, kom cov spectrum tom qab kis spectrum modulation tuaj yeem sib tshooj, yog li txo qhov kev sib nrig sib cuam tshuam ntawm subcarriers. Txoj kev hloov kho siv los ntawm txhua tus neeg nqa khoom ntawm COFDM tuaj yeem sib txawv. Txhua tus neeg nqa khoom tuaj yeem xaiv cov kev hloov pauv sib txawv raws li cov xwm txheej sib txawv, xws li BPSK, QPSK, 8PSK, 16QAM, 64QAM, thiab lwm yam, raws li lub hauv paus ntsiab lus ntawm qhov zoo tshaj plaws sib npaug ntawm spectrum siv thiab me ntsis yuam kev tus nqi. COFDM thev naus laus zis siv kev hloov pauv hloov pauv, thiab xaiv cov kev hloov pauv sib txawv raws li qhov zoo ntawm cov channel. COFDM kuj tau txais kev sib koom ua haujlwm ntawm kev tswj fais fab thiab kev hloov pauv hloov. Thaum zoo channel, lub zog kis tau tus mob tseem tsis hloov, thiab modulation hom (as 64 QAM) tuaj yeem txhim kho, los yog lub zog xa hluav taws xob tuaj yeem txo qis thaum cov kev hloov pauv qis (zoo li QPSK).
- COFDM thev naus laus zis yog lub hauv paus ntawm HPA Alliance (HomePlug Powerline Alliance) industrial specification. Nws siv lub tshuab tsis tu ncua ntau lub suab los ua ke kom muaj ntau lub teeb liab hauv ntau zaus hu ua cov cab kuj mus rau hauv ib lub teeb liab kom tiav cov teeb liab kis tau tus mob.. Vim tias cov cuab yeej no muaj peev xwm xa cov teeb liab hauv qab kev cuam tshuam, Nws yog feem ntau siv hauv kev sib kis xov xwm uas raug cuam tshuam rau sab nraud los yog tsis muaj peev xwm tiv thaiv kev cuam tshuam sab nraud.
- COFDM yog lub npe luv ntawm Coded Orthogonal Frequency Division Multiplexing, uas yog qhov zoo tshaj plaws thiab pheej yig tshaj modulation tshuab nyob rau hauv lub ntiaj teb no. Nws tus nqi siv tau yog nyob rau hauv kev txhawb nqa cov ntawv thov uas tawg los ntawm kev txwv ntawm kab-ntawm-pom pom. Nws yog ib lub tshuab uas ua rau tag nrho cov kev siv xov tooj cua spectrum thiab muaj kev tiv thaiv zoo rau lub suab nrov thiab cuam tshuam. Diffraction thiab nkag mus ntawm kev thaiv yog COFDM technologies. cov tub ntxhais. Nws lub hauv paus ntsiab lus tseem ceeb yog hloov cov ntaub ntawv ceev ceev mus rau ntau qhov kev sib txuas nrog qis dua tus nqi los ntawm kev hloov pauv mus rau qhov sib npaug rau kev sib kis..
- COFDM thev naus laus zis tuaj yeem cais ntau lub cim digital ib txhij thiab tuaj yeem ua haujlwm nyab xeeb ntawm kev cuam tshuam cov teeb liab. Nws yog precisely vim hais tias ntawm no tshwj xeeb teeb liab "nkag tau" tias COFDM thev naus laus zis tau hlub thiab txais tos los ntawm cov tuam txhab kev sib txuas lus. COFDM thev naus laus zis tuaj yeem saib xyuas kev hloov pauv tam sim ntawm cov yam ntxwv ntawm kev sib txuas lus nruab nrab. Lub peev xwm ntawm txoj kev sib txuas lus xa cov ntaub ntawv yuav hloov nrog lub sijhawm. COFDM tuaj yeem hloov kho kom haum rau nws, thiab hloov mus rau thiab tawm ntawm tus neeg nqa khoom sib txuas kom ntseeg tau tias muaj kev vam meej tas mus li. tsab ntawv xov xwm vam meej. COFDM tshuab yog tshwj xeeb tshaj yog haum rau siv nyob rau hauv high-sawv vaj tse, muaj neeg coob coob thiab thaj chaw tseem ceeb, thaj chaw uas cov teeb liab kis tau, thiab qhov chaw uas cov ntaub ntawv ceev tau xa mus.
Qhov zoo ntawm COFDM technology
- Ib tug loj npaum li cas ntawm cov ntaub ntawv kuj yuav xa nyob rau hauv nqaim bandwidth: COFDM thev naus laus zis tuaj yeem cais tsawg kawg 1000 digital signals tib lub sijhawm, thiab kev muaj peev xwm ua haujlwm nyab xeeb nyob ib puag ncig cuam tshuam cov teeb liab yuav cuam tshuam ncaj qha rau CDMA thev naus laus zis uas tau nrov hauv khw niaj hnub no. Cov qauv ntawm kev txhim kho ntxiv thiab kev loj hlob yog qhov tseeb vim qhov teeb meem tshwj xeeb no "nkag tau" uas ua rau COFDM thev naus laus zis nrov thiab nrov nrog European cov tswv lag luam thiab cov tuam txhab xov tooj ntawm tes, xws li California Cisco Systems, New York Flarion Institute of Technology thiab Lucent Institute of Technology thiab lwm tus tau pib siv cov thev naus laus zis no, thiab Canadian Wi-LAN Institute of Technology kuj tau pib siv cov thev naus laus zis no.
- COFDM thev naus laus zis tuaj yeem saib xyuas kev hloov pauv tam sim ntawm cov yam ntxwv ntawm kev sib txuas lus nruab nrab: Txij li thaum muaj peev xwm ntawm txoj kev sib txuas lus xa cov ntaub ntawv yuav hloov mus rau lub sijhawm, COFDM tuaj yeem hloov kho kom haum rau nws thiab hloov mus rau thiab tawm ntawm cov cab kuj sib txuas Los xyuas kom muaj kev sib txuas lus txuas ntxiv.;
- Cov thev naus laus zis no tuaj yeem kuaj pom tus neeg nqa khoom tshwj xeeb twg muaj cov teeb liab siab attenuation lossis cuam tshuam pulse nyob rau hauv nruab nrab kis tau tus mob, thiab tom qab ntawd siv cov kev ntsuas tsim nyog los ua kom tus neeg nqa khoom ntawm cov zaus teev kom sib txuas lus tau zoo;
- COFDM tshuab yog tshwj xeeb tshaj yog haum rau siv nyob rau hauv high-sawv vaj tse, muaj neeg coob coob thiab thaj chaw tseem ceeb, thiab thaj chaw uas cov teeb liab kis tau. Ob qhov kev sib kis ceev ceev thiab cov suab digital tshaj tawm cia siab tias yuav txo tau qhov cuam tshuam ntawm kev cuam tshuam ntau yam ntawm cov teeb liab.
- Nws tuaj yeem tiv thaiv kev cuam tshuam ntawm cov teeb liab waveforms, thiab yog haum rau high-ceev cov ntaub ntawv kis tau tus mob nyob rau hauv multipath ib puag ncig thiab fading raws. Thaum ntau zaus xaiv fading tshwm sim vim kev sib kis ntau hauv cov channel, tsuas yog cov subcarriers poob rau hauv lub zaus band kev nyuaj siab thiab cov ntaub ntawv nqa los ntawm lawv raug cuam tshuam, thiab lwm yam subcarriers tsis puas, yog li tag nrho me ntsis yuam kev tus nqi kev ua tau zoo ntawm lub system yog zoo dua ntau.
- Los ntawm kev sib koom coding ntawm txhua tus subcarrier, nws muaj zog anti-fading muaj peev xwm. COFDM thev naus laus zis nws tus kheej twb tau siv ntau qhov sib txawv ntawm cov channel, yog tias fading tsis yog tshwj xeeb, tsis tas yuav ntxiv ib lub sij hawm sau equalizer. Los ntawm kev sib koom ua ke ntawm txhua tus channel, qhov system kev ua tau zoo tuaj yeem txhim kho.
- COFDM thev naus laus zis muaj kev tiv thaiv zoo rau kev cuam tshuam nqaim, vim tias cov kev cuam tshuam no tsuas yog cuam tshuam rau ib feem me me ntawm cov sub-channels.
- Txoj kev siv ntawm OFDM raws li IFFT / FFT tuaj yeem xaiv;
- Tus nqi siv channel yog siab heev, uas yog ib qho tseem ceeb tshwj xeeb tshaj yog nyob rau hauv ib puag ncig wireless nrog tsawg spectrum peev txheej; thaum tus naj npawb ntawm sub-carriers loj, spectrum siv tus nqi ntawm lub cev nyhav yog 2Baud / Hz.
- Daim ntawv thov ntawm COFDM thev naus laus zis hauv kev xa cov duab wireless muaj cov txiaj ntsig zoo hauv qab no:
- Siv rau hauv qhov chaw tsis pom thiab thaiv qhov chaw, qhov zoo heev "kev txawv txav" thiab "nkag mus" muaj peev xwm ua rau nws haum rau lub sijhawm tiag tiag wireless cov duab xa mus rau hauv nroog, suburb, thiab cov tsev. Cov khoom siv microwave ib txwm yuav tsum pom nyob rau hauv qhov pom kev. (Yuav tsum tsis muaj kev cuam tshuam ntawm ob qho kev xa thiab txais cov ntsiab lus) tsim kom muaj ib lub wireless txuas channel, yog li kev siv tau txwv ntau heev los ntawm ib puag ncig. Nws yog ib qho tsim nyog los tshuaj xyuas qhov chaw thov ua ntej, xaiv thiab kuaj cov ntsiab lus xa thiab txais, kho cov kev taw qhia ntawm tus kav hlau txais xov, thiab xam qhov siab ntawm lub kav hlau txais xov, thiab lwm yam. , kev ua haujlwm yog hnyav heev thiab cumbersome, uas tsis tsuas txwv ncaj qha rau kev sib kis thiab txais tos ntawm lub suab thiab video, tab sis kuj zoo heev txo qhov kev ntseeg siab thiab kev ua haujlwm ntawm qhov system.
COFDM wireless duab cov cuab yeej tau hloov tag nrho cov xwm txheej no. Vim nws cov yam ntxwv xws li multi-carrier, Cov khoom siv COFDM muaj qhov zoo ntawm "tsis yog kab ntawm kev pom" thiab "kev txawv txav" kis tau tus mob. Paub qhov ruaj khov kis ntawm cov duab, tsis cuam tshuam los ntawm ib puag ncig lossis cuam tshuam los ntawm ib puag ncig. Lub kaw lus adopts omnidirectional kav hlau txais xov, uas tuaj yeem teeb tsa qhov txuas txuas wireless hauv lub sijhawm luv tshaj plaws. Qhov kawg ntawm qhov tau txais thiab qhov kawg tau txais kuj tuaj yeem txav mus los yam tsis muaj kev txwv los ntawm kev taw qhia. Qhov system yog yooj yim, ntseeg tau, thiab yoog raws hauv kev thov.
- Nws yog tsim rau wireless kis tau tus mob ntawm real-time dluab nyob rau hauv high-ceev txav, thiab tuaj yeem siv microwave (digital microwave, kis spectrum microwave) thiab cov khoom siv LAN wireless ntawm lub platform xws li tsheb, nkoj, thiab helicopters. Vim technical system vim li cas, Qhov kev tau txais lub davhlau ya nyob twg tsis tuaj yeem paub nws tus kheej thiab qhov kawg tau txais cov duab xa tawm hauv lub sijhawm tiag tiag thaum lub zog ceev. Thaum siv cov khoom siv microwave thiab wireless LAN ntawm cov tsheb thiab nkoj rau kev xa cov duab wireless, qhov kev daws teeb meem ib txwm yog los teeb tsa ib qho ntxiv "servo stability" ntaus ntawv los daws teeb meem xws li electromagnetic yoj taw qhia, taug qab, thiab stabilization, tab sis nws tsuas yog siv tau raws li qee yam xwm txheej. Paub txog qhov kis tau tus mob ntawm qhov taw tes mobile mus rau qhov chaw ruaj khov nyob rau hauv ib puag ncig, thiab cov duab feem ntau cuam tshuam, uas cuam tshuam rau cov nyhuv ntawm kev sib kis thiab kev txais tos. Engineering yog complex, qhov kev ntseeg tau raug txo, thiab tus nqi yog siab heev.
Tab sis rau cov khoom siv COFDM, nws tsis xav tau cov khoom siv ntxiv, thiab nws tuaj yeem siv nruab nrab ntawm kev ruaj ntseg mobile, mobile-kev, thiab yog heev haum rau installation ntawm mobile platforms xws li tsheb, nkoj, thiab helicopters. Tsis tsuas yog kis tau tus mob muaj kev ntseeg siab, tab sis kuj qhia tau hais tias tus nqi siab ua haujlwm.
- Cov kis tau tus mob bandwidth siab, uas yog tsim rau siab me ntsis tus nqi thiab cov duab zoo suab thiab video kis tau tus mob. Cov duab me ntsis tus nqi feem ntau tuaj yeem siab dua 4M bps. In general digital microwave and spread spectrum microwave transmission links, although MPEG-2 encoding is used, the channel mostly adopts 2M rate, such as E1, so that the decoded image resolution can reach 720×576, but the image compressed code stream is only 1M Left and right, unable to meet the specific requirements of the receiving end for post-audio and video analysis, cia, and editing.
Each subcarrier of COFDM technology can choose high-speed modulation such as QPSK, 16QAM, 64QAM, thiab lwm yam, and the combined channel rate is generally greater than 4M bps. Yog li ntawd, high-quality codec images such as 4:2:0 thiab 4:2:2 in MPEG-2 can be transmitted, the image resolution of the receiving end can reach 720×576 or 720×480, and the code stream can be around 6M. The image quality is close to that of DVD, uas tuaj yeem ua tau raws li cov kev cai tshwj xeeb ntawm qhov kawg tau txais rau kev tshuaj xyuas tom qab-suab thiab video, cia, and editing.
- Nyob rau hauv ib tug complex electromagnetic ib puag ncig, COFDM muaj kev cuam tshuam zoo heev tiv thaiv kev cuam tshuam ntau zaus xaiv fading lossis nqaim-band cuam tshuam thiab cuam tshuam ntawm cov teeb liab waveforms. Los ntawm kev sib koom coding ntawm txhua tus sub-carrier, nws muaj peev xwm tiv thaiv fading. Nyob rau hauv ib leeg-carrier systems (xws li digital microwave, kis-spectrum microwave, thiab lwm yam), ib qho fading los yog cuam tshuam tuaj yeem ua rau tag nrho kev sib txuas lus tsis ua haujlwm, tab sis nyob rau hauv ib tug multi-carrier COFDM system, tsuas yog ib feem me me ntawm sub-carriers yuav cuam tshuam, thiab cov sub-carriers Cov channel tseem tuaj yeem siv cov lej kho qhov yuam kev rau kev kho qhov yuam kev los xyuas kom meej qhov tsawg me ntsis yuam kev rau kev sib kis..
Daim ntawv thov ntawm COFDM Wireless Transmission Technology hauv Kev Saib Xyuas Video
Cov duab xaim hluav taws xob wireless siv COFDM thev naus laus zis muaj qhov tsis zoo-kab-ntawm-pob qhov muag pom thiab kev ua haujlwm siab ceev ntawm lub xov tooj ntawm tes., thiab tuaj yeem muab cov duab thiab suab ntawm lub sijhawm tiag tiag ntawm DVD zoo. Lub suab thiab yees duab nyob rau ntawm qhov chaw tuaj yeem kis tau yooj yim thiab nrawm ncaj qha los ntawm lub tsheb-mounted lossis portable khoom lossis xa rov qab mus rau qhov chaw hais kom ua los ntawm chaw nres tsheb relay, optical fiber ntau network, thiab lwm yam. Cov khoom siv tuaj yeem tsim kev sib txuas mus ntev nrog lwm lub microwave, satellite, thiab cov khoom siv sib txuas lus kho qhov muag fiber ntau los tsim kom muaj kev ua tau zoo thiab muaj txiaj ntsig zoo ntawm cov duab xa mus. Lub ntsiab daim ntawv thov ib puag ncig ntawm wireless duab kis tau tus mob cov cuab yeej ntawm COFDM technology yog: nroog tsim thaiv ib puag ncig, nruab nrab ntawm cov tsev, sab hauv thiab sab nraum cov tsev, nruab nrab ntawm underground thiab hauv av ntawm cov tsev; siv hauv mobile; hiav txwv duab, aerial duab kis tau tus mob, thiab lwm yam. Nws yog cov duab zoo tshaj plaws wireless uas xav tau sai sai los ntawm kev ruaj ntseg pej xeem hauv tsev, tub rog, tub ceev xwm tub rog, tiv thaiv hluav taws, Civil Air Defense (kev tiv thaiv pej xeem), kev txuag dej, maritime affairs, kev lis kev cai, xov tooj cua thiab TV thiab lwm yam kev lag luam hauv kev ruaj ntseg, teb hais kom ua, lub luag haujlwm nrhiav, kev cawm dim, nyob tshaj tawm thiab lwm yam hauj lwm kis tau tus mob ntaus ntawv.
hanhsx wireless image real-time transmission monitoring system txais COFDM thev naus laus zis, uas tuaj yeem ua kom ruaj khov kis tau tus mob thiab saib xyuas lub sijhawm tiag tiag hauv kev txav nrawm, anti-fading thiab multi-txoj kev cuam tshuam (txav ceev tuaj yeem ncav cuag 150 km / h), thiab muab high-txhais tshaj tawm-qib DVD zoo Duab, muaj zog tsis-kab-ntawm-pob ntseg kis tau tus mob, zoo tagnrho rau nroog thaiv ib puag ncig daim ntawv thov hu ua nyuaj heev "kev sib txuas lus canyon", tsis muaj kav hlau txais xov orientation. Cov khoom muaj cov yam ntxwv hauv qab no: audio thiab video digital kis tau tus mob, cov duab xa tawm ntawm lub sijhawm, me me ntim ntawm tau txais thiab transmitter, muaj zog txav, yoog raws thiab yooj yim, siv tau los ntawm tes, encrypted kis tau tus mob, zoo tsis pub lwm tus paub, thiab qhov kev sib txuas sib kis tau mus txog 10KM-50KM.
Cov khoom siv dav siv hauv kev ruaj ntseg pej xeem, tiv thaiv hluav taws, tub ceev xwm tsheb, Civil Air Defense Emergency, kev cai lij choj hauv nroog, kev saib xyuas kev tiv thaiv ib puag ncig, hluav taws kub ceev, kev txuag dej thiab kev tswj dej nyab, hluav taws xob thaum muaj xwm ceev, railway xwm ceev, tub ceev xwm maritime, kev soj ntsuam xyuas dej hiav txwv, kev lis kev cai ciam teb tiv thaiv, saib xyuas qhov chaw nres nkoj, hav zoov tiv thaiv hluav taws, roj teb tiv thaiv tub sab nyiag , tub rog tshawb nrhiav thiab lwm yam, haum rau lub sijhawm tiag tiag ntawm kev xa xov tooj ntawm tes thiab saib xyuas cov duab zoo hauv ntau qhov chaw nyuaj xws li hauv nroog, hiav txwv, thiab roob.
