Wannan shafin yana bayanin tushen Fadewa da nau'ikan dusashewa a cikin sadarwa mara waya. Nau'in Fading sun kasu kashi-kashi zuwa manyan ma'auni da raguwar sikelin (yawan jinkiri da yawa da yaduwar doppler).
Fashewar lebur da faɗuwar mitar mitoci wani ɓangare ne na faɗuwar hanyoyi da yawa inda saurin faɗuwa da raguwar jinkirin wani ɓangare ne na faɗuwar doppler. Ana aiwatar da waɗannan nau'ikan faɗuwa kamar yadda Rayleigh, Rician, Nakagami da Weibull ke rabawa ko samfuri.
Gabatarwa:
Kamar yadda muka sani tsarin sadarwa mara waya ya ƙunshi watsawa da karɓa. Hanya daga mai watsawa zuwa mai karɓa ba ta da santsi kuma siginar da aka watsa na iya wucewa ta hanyoyi daban-daban ciki har da asarar hanya, attenuation multipath da dai sauransu. Ƙarƙashin siginar ta hanyar ya dogara da dalilai daban-daban. Su ne lokaci, mitar rediyo da hanya ko matsayi na mai watsawa/ karɓa. Tashar tsakanin mai watsawa da mai karɓa na iya bambanta lokaci ko ƙayyadaddun dangane da ko an daidaita mai watsawa ko mai karɓa ko motsi dangane da juna.
Me ke fadewa?
Bambancin lokaci na ƙarfin siginar da aka karɓa saboda canje-canje a matsakaicin watsawa ko hanyoyi ana kiransa shuɗewa. Fadewa ya dogara da abubuwa daban-daban kamar yadda aka ambata a sama. A cikin ƙayyadaddun yanayin, faɗuwa ya dogara da yanayin yanayi kamar ruwan sama, walƙiya da sauransu. A cikin yanayin wayar hannu, dusashewa ya dogara da cikas kan hanyar da ke bambanta dangane da lokaci. Wadannan cikas suna haifar da hadaddun tasirin watsawa zuwa siginar da aka watsa.
Hoton-1 yana nuna girman girma da ginshiƙi mai nisa don raguwar jinkiri da nau'in faɗuwa mai sauri wanda zamu tattauna daga baya.
Nau'ukan dusashewa
Yin la'akari da lahani iri-iri da ke da alaƙa da tashoshi da matsayi na watsawa / mai karɓa na biye su ne nau'ikan dusashewa a cikin tsarin sadarwar mara waya.
➤Large Scale Fading: Ya haɗa da asarar hanya da tasirin inuwa.
➤Ƙaramin Faɗuwa: Ya kasu kashi biyu manya-manyan nau'i. Multipath jinkirin yadawa da kuma yaduwar doppler. An ƙara rarrabuwar jinkirin jinkirin hanyoyi zuwa faɗuwar faɗuwa da mitar zaɓe. Doppler yadudduka ya kasu kashi-kashi mai saurin faduwa da raguwar jinkirin.
Samfuran Fading: Sama da nau'ikan faduwa ana aiwatar da su a cikin nau'o'i daban-daban ko rarrabawa waɗanda suka haɗa da Rayleigh, Rician, Nakagami, Weibull da sauransu.
Kamar yadda muka sani, sigina masu dusashewa suna faruwa saboda tunani daga ƙasa da gine-ginen da ke kewaye da kuma tarwatsa sigina daga bishiyoyi, mutane da hasumiya da ke cikin babban yanki. Akwai nau'ikan faduwa iri biyu. babban ma'auni yana faɗuwa da ƙaramar ma'auni.
1.) Babban Fassara
Babban fashewar ma'auni yana faruwa lokacin da cikas ya shiga tsakanin mai aikawa da mai karɓa. Wannan nau'in tsangwama yana haifar da babban adadin rage ƙarfin sigina. Wannan saboda EM taguwar ruwa yana inuwa ko toshe shi ta hanyar cikas. Yana da alaƙa da manyan jujjuyawar sigina akan nisa.
1.a) Rasa tafarki
Ana iya bayyana asarar hanyar sarari kyauta kamar haka.
➤ Pt/Pr = {(4 * π * d)2/ λ2} = (4*π*f*d)2/c2
Ina,
Pt = watsa iko
Pr = Karba iko
λ = tsawo
d = nisa tsakanin watsawa da karɓar eriya
c = gudun haske watau 3 x 108
Daga lissafin yana nuna cewa siginar da aka watsa yana raguwa a kan nisa yayin da ake yada siginar a kan mafi girma kuma mafi girma yanki daga ƙarshen watsawa zuwa ƙarshen karɓa.
1.b) Tasirin inuwa
Ana lura da shi a cikin sadarwa mara waya. Shadowing shine karkatar da ikon da aka karɓa na siginar EM daga matsakaicin ƙima.
• Sakamakon cikas a kan hanyar da ke tsakanin watsawa da mai karɓa.
• Ya dogara da matsayi na yanki da kuma mitar rediyo na raƙuman ruwa na EM (ElectroMagnetic).
2. Karamin Sikeli Fade
Ƙananan faɗuwa yana damuwa da saurin saurin saurin sigina da aka karɓa akan ɗan gajeren tazara da ɗan gajeren lokaci.
Bisa gamultipath jinkirta yadaakwai nau'i biyu na ƙananan sikelin fading wato. faduwar faɗuwa da mitar zaɓen faɗuwa. Waɗannan nau'ikan faɗuwar hanyoyi da yawa sun dogara da yanayin yaduwa.
2.a) Fassara lebur
An ce tashar mara igiyar waya tana raguwa idan tana da ci gaba da samun ci gaba da amsa lokaci na layi akan bandwidth wanda ya fi bandwidth na siginar da aka watsa.
A cikin irin wannan nau'in faɗuwa duk abubuwan mitar siginar da aka karɓa suna canzawa daidai gwargwado a lokaci guda. Hakanan ana kiranta da fading mara zaɓi.
• Siginar BW << Tashar BW
• Lokacin Alama >> Jinkirin Yaduwa
Ana ganin tasirin faɗuwar lebur a matsayin raguwa a cikin SNR. Waɗannan tashoshi masu faɗuwa an san su da girman tashoshi daban-daban ko tashoshi masu kunkuntar.
2.b) Matsakaicin Zaɓen Fashewa
Yana rinjayar sassa daban-daban na siginar rediyo tare da amplitudes daban-daban. Saboda haka sunan zaɓaɓɓen fade.
• Siginar BW > Tashar BW
• Lokacin Alama < Jinkirta Yadawa
Bisa gadoppler yadaakwai nau'ikan fadewa iri biyu. saurin fashewa da raguwa a hankali. Waɗannan nau'ikan faɗuwar doppler sun dogara da saurin wayar hannu watau saurin mai karɓa dangane da watsawa.
2.c) Saurin gushewa
Lamarin faɗuwa da sauri yana wakilta ta saurin saurin sigina akan ƙananan yankuna (watau bandwidth). Lokacin da siginonin suka zo daga dukkan kwatance a cikin jirgin, za a lura da faɗuwa da sauri don duk hanyoyin motsi.
Fasawa da sauri yana faruwa lokacin da martanin tasha ya canza da sauri cikin tsawon alamar.
• Babban yaduwar doppler
Lokacin Alama > Lokacin haɗin kai
• Bambancin sigina <Bambancin tashoshi
Wannan sigogi suna haifar da tarwatsewar mita ko ɓataccen lokaci saboda yaduwar doppler. Fasawa da sauri shine sakamakon tunanin abubuwa na gida da motsin abubuwa dangane da waɗannan abubuwan.
A cikin faɗuwa da sauri, karɓar sigina shine jimlar sigina masu yawa waɗanda ke nunawa daga saman daban-daban. Wannan siginar jimla ce ko bambanci na sigina da yawa waɗanda zasu iya zama masu haɓakawa ko ɓarna dangane da canjin lokaci tsakanin su. Dangantaka na lokaci sun dogara ne akan saurin motsi, yawan watsawa da tsayin hanyar dangi.
Fasawa da sauri yana karkatar da siffar bugun bugun gindi. Wannan murdiya ta layi ce kuma tana haifarwaISI(Inter Symbol Interference). Daidaitaccen daidaitawa yana rage ISI ta hanyar cire murdiya ta layi wanda tashar ta jawo.
2.d) Sannu a hankali
Guduwar sannu a hankali shine sakamakon inuwar gine-gine, tsaunuka, tsaunuka da sauran abubuwa akan hanyar.
• Ƙananan Doppler Yaduwa
• Lokacin alamar <
• Bambancin sigina >> Bambancin tashoshi
Aiwatar da samfuran Fading ko raguwar rarrabawa
Aiwatar da ƙira masu shuɗewa ko raguwar rarraba sun haɗa da faɗuwar Rayleigh, faɗuwar Rician, Fading Nakagami da Fading Weibull. An tsara waɗannan rabe-raben tashoshi ko ƙira don haɗa faɗuwa a cikin siginar bayanai na baseband kamar yadda buƙatun bayanan faɗuwa.
Rayleigh faduwa
• A cikin samfurin Rayleigh, abubuwan da ba Layin Gani ba (NLOS) kawai aka kwaikwayi tsakanin mai watsawa da mai karɓa. Ana ɗauka cewa babu wata hanya ta LOS tsakanin mai aikawa da mai karɓa.
• MATLAB yana ba da aikin "rayleighchan" don kwaikwayi samfurin tashar rayleigh.
• An rarraba wutar lantarki da yawa.
• An rarraba lokaci daidai gwargwado kuma mai zaman kanta daga amplitude. Shi ne nau'in Fading da aka fi amfani da shi wajen sadarwa mara waya.
Rician faduwa
• A cikin ƙirar rician, duka Lines of Sight (LOS) da waɗanda ba Layin Gani (NLOS) an daidaita su tsakanin masu watsawa da mai karɓa.
• MATLAB yana ba da aikin "ricianchan" don kwaikwayi samfurin tashar rician.
Nakagami faduwa
Nakagami fadding tashar sigar ƙididdiga ce da ake amfani da ita don bayyana tashoshi na sadarwa mara igiyar waya wanda sgnal da aka karɓa a cikin su ke fuskantar faɗuwar hanyoyi masu yawa. Yana wakiltar mahalli masu matsakaicin matsakaici zuwa mai tsanani kamar yankunan birni ko kewayen birni. Ana iya amfani da ma'auni mai zuwa don kwaikwayi samfurin tashar Nakagami mai faɗuwa.
A wannan yanayin muna nuna h = r*ejΦkuma an rarraba kusurwa Φ akan [-π, π]
• Ana ɗaukar m r da Φ masu zaman kansu ne.
• Nakagami pdf an bayyana shi kamar yadda yake sama.
• A cikin Nakagami pdf, 2σ2= E {r2}, Γ(.) shine aikin Gamma kuma k>= (1/2) shine adadi mai faɗuwa (digiri na 'yanci da ke da alaƙa da adadin ƙarin masu canji na Gaussion).
An samo asali ne bisa ma'auni.
• Ana rarraba wutar lantarki nan take Gamma. • Tare da k = 1 Rayleigh = Nakagami
Weibull yana faɗuwa
Wannan tasha wata ƙididdiga ce da ake amfani da ita don bayyana tashar sadarwa mara waya. Ana amfani da tashar faɗuwar Weibull don wakiltar mahalli tare da nau'ikan yanayin faɗuwa iri-iri da suka haɗa da rarrauna da faɗuwa mai tsanani.
Ina,
2 σ2= E {r2}
• Rarraba Weibull yana wakiltar wani gama-gari na rarraba Rayleigh.
• Lokacin da X da Y ke iid sifili suna nufin masu canjin gaussian, ambulaf na R = (X2+ Y2)1/2an rarraba Rayleigh. Duk da haka an bayyana ambulaf R = (X2+ Y2)1/2, kuma madaidaicin pdf (profile rarraba wutar lantarki) ana rarraba Weibull.
Ana iya amfani da ma'auni mai zuwa don kwaikwayi samfurin faɗewar Weibull.
A cikin wannan shafi mun tabo batutuwa daban-daban a kan dusashewa kamar su tashar da ke dishewa, nau'insa, nau'ikansa masu shudewa, aikace-aikacen su, ayyukansu da dai sauransu. Ana iya amfani da bayanan da aka bayar a wannan shafi don kwatantawa da samun bambanci tsakanin faɗuwar ƙarami da faɗuwar ma'auni mai girma, bambanci tsakanin faɗuwar faɗuwa da mitar zaɓe, bambanci tsakanin faɗuwar sauri da faɗuwar jinkiri, bambanci tsakanin rayleigh fading da rician fading haka kuma.
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Lokacin aikawa: Agusta-14-2023
