MER: Qhov piv txwv ntawm qhov yuam kev modulation, uas yog qhov sib piv ntawm qhov txiaj ntsig zoo ntawm qhov vector magnitude rau qhov txiaj ntsig zoo ntawm qhov yuam kev magnitude ntawm daim duab constellation (qhov sib piv ntawm lub square ntawm qhov vector magnitude zoo tagnrho rau lub square ntawm qhov yuam kev vector magnitude). Nws yog ib qho ntawm cov cim qhia tseem ceeb los ntsuas qhov zoo ntawm cov teeb liab digital TV. Nws yog qhov tseem ceeb heev rau cov txiaj ntsig ntsuas logarithmic ntawm qhov distortion superimposed ntawm lub teeb liab digital modulation. Nws zoo ib yam li qhov piv ntawm lub teeb liab mus rau suab nrov lossis qhov piv ntawm tus neeg nqa khoom mus rau suab nrov siv hauv lub kaw lus analog. Nws yog lub kaw lus txiav txim siab qhov tseem ceeb ntawm kev ua tsis tiav. Lwm cov cim qhia zoo sib xws xws li BER bit error rate, C/N carrier-to-noise ratio, lub zog theem nruab nrab, daim duab constellation, thiab lwm yam.
Tus nqi ntawm MER yog qhia hauv dB, thiab qhov loj dua tus nqi ntawm MER, qhov zoo dua qhov zoo ntawm lub teeb liab. Qhov zoo dua qhov teeb liab, qhov ze dua cov cim modulated yog rau qhov chaw zoo tagnrho, thiab vice versa. Qhov tshwm sim ntawm kev sim ntawm MER qhia txog lub peev xwm ntawm lub receiver digital los rov qab tus lej binary, thiab muaj qhov sib piv ntawm lub teeb liab-rau-suab nrov (S / N) zoo ib yam li ntawm lub teeb liab baseband. Lub teeb liab QAM-modulated yog tso tawm los ntawm qhov kawg pem hauv ntej thiab nkag mus rau hauv tsev los ntawm lub network nkag mus. Lub cim MER yuav maj mam poob qis. Hauv qhov xwm txheej ntawm daim duab kos duab 64QAM, tus nqi empirical threshold ntawm MER yog 23.5dB, thiab hauv 256QAM nws yog 28.5dB (qhov tso zis pem hauv ntej yuav tsum yog Yog tias nws siab dua 34dB, nws tuaj yeem ua kom ntseeg tau tias lub teeb liab nkag mus rau hauv tsev ib txwm, tab sis nws tsis txiav txim siab qhov tsis zoo los ntawm qhov zoo ntawm cov xov hlau xa lossis qhov kawg pem hauv ntej). Yog tias nws qis dua tus nqi no, daim duab kos duab constellation yuav tsis raug xauv. Qhov yuav tsum tau ua ntawm MER qhov ntsuas qhov tso zis pem hauv ntej: Rau 64/256QAM, pem hauv ntej > 38dB, sub-front-end > 36dB, optical node > 34dB, amplifier > 34dB (theem ob yog 33dB), tus neeg siv kawg > 31dB (theem ob yog 33dB), saum toj no 5 Ib qho tseem ceeb MER kuj feem ntau siv los nrhiav cov teeb meem cable TV kab.
Qhov tseem ceeb ntawm MER MER yog suav hais tias yog ib daim ntawv ntawm kev ntsuas SNR, thiab lub ntsiab lus ntawm MER yog:
①. Nws suav nrog ntau hom kev puas tsuaj rau lub teeb liab: suab nrov, kev xau ntawm cov cab kuj, IQ amplitude tsis sib npaug, thiab suab nrov theem.
②. Nws qhia txog lub peev xwm ntawm cov haujlwm digital los rov qab tau cov lej binary; nws qhia txog qib kev puas tsuaj rau cov teeb liab digital TV tom qab xa mus los ntawm lub network.
3. SNR yog ib qho parameter baseband, thiab MER yog ib qho parameter zaus xov tooj cua.
Thaum lub teeb liab zoo poob qis mus rau ib qib, cov cim thaum kawg yuav raug txhais tsis raug. Lub sijhawm no, qhov yuam kev me ntsis tiag tiag BER nce ntxiv. BER (Bit Error Rate): Qhov yuam kev me ntsis, txhais tias yog qhov sib piv ntawm tus lej ntawm cov yuam kev me ntsis rau tag nrho cov lej ntawm cov me ntsis. Rau cov teeb liab digital binary, txij li cov me ntsis binary raug xa mus, qhov yuam kev me ntsis hu ua qhov yuam kev me ntsis (BER).
BER = Qhov Yuam Kev Bit Rate / Tag Nrho Bit Rate.
Feem ntau BER yog qhia hauv kev sau ntawv txog kev tshawb fawb, thiab qhov qis dua BER, qhov zoo dua. Thaum lub teeb liab zoo heev, cov nqi BER ua ntej thiab tom qab kev kho qhov yuam kev zoo ib yam; tab sis nyob rau hauv cov ntaub ntawv ntawm qee qhov kev cuam tshuam, cov nqi BER ua ntej thiab tom qab kev kho qhov yuam kev sib txawv, thiab tom qab kev kho qhov yuam kev Tus nqi yuam kev me ntsis qis dua. Thaum qhov yuam kev me ntsis yog 2 × 10-4, ib feem mosaic tshwm sim qee zaum, tab sis nws tseem tuaj yeem pom; qhov tseem ceeb BER yog 1 × 10-4, ntau tus mosaics tshwm sim, thiab cov duab rov ua dua tsis tu ncua; BER ntau dua 1 × 10-3 tsis tuaj yeem pom txhua. saib. Lub BER index tsuas yog tus nqi siv thiab tsis qhia tag nrho cov xwm txheej ntawm tag nrho cov khoom siv network. Qee zaum nws tsuas yog tshwm sim los ntawm kev nce sai sai vim muaj kev cuam tshuam tam sim ntawd, thaum MER yog qhov sib txawv kiag li. Tag nrho cov txheej txheem tuaj yeem siv los ua kev tshuaj xyuas cov ntaub ntawv yuam kev. Yog li ntawd, MER tuaj yeem muab kev ceeb toom ntxov rau cov teeb liab. Thaum qhov zoo ntawm cov teeb liab txo qis, MER yuav txo qis. Nrog rau kev nce ntawm suab nrov thiab kev cuam tshuam rau qee qhov, MER yuav maj mam txo qis, thaum BER tseem tsis hloov pauv. Tsuas yog thaum kev cuam tshuam nce mus rau qee qhov, MER Lub BER pib poob qis thaum MER poob qis tas li. Thaum MER poob rau qib pib, BER yuav poob qis heev.
Lub sijhawm tshaj tawm: Lub Ob Hlis-23-2023