Iri peji rinotsanangura Kupera kwekutanga uye mhando dzekupera mukutaurirana pasina waya. Mhando dzeFading dzakakamurwa kuita chiyero chikuru chinopera uye chidiki chinopera (multipath kunonoka kupararira uye doppler kupararira).
Kupera kweflat uye kusarudza kupera nguva zhinji chikamu chekuwanda kwenzira apo kupera nekukurumidza uye kupera zvishoma nezvishoma chiri chikamu chekupararira kwedoppler. Aya marudzi ari kupera anoitwa sekugoverwa kwaRayleigh, Rician, Nakagami uye Weibull kana modhi.
Nhanganyaya:
Sezvatinoziva isina waya yekutaurirana system ine inotumira uye inogamuchira. Iyo nzira kubva kune inofambisa kuenda kune inogamuchira haina kutsvedzerera uye iyo inotapurira chiratidzo inogona kupfuura nemhando dzakasiyana dzekurebesa kusanganisira kurasikirwa kwenzira, kuwanda kwenzira, etc. Kudzikiswa kwechiratidzo kuburikidza nenzira kunoenderana nezvinhu zvakasiyana. Inguva, redhiyo frequency uye nzira kana chinzvimbo chetransmitter/receiver. Iyo chiteshi pakati pemutakuri uye inogamuchira inogona kuva nguva inosiyana kana yakagadziriswa zvichienderana nekuti iyo inofambisa / inogamuchira yakagadziriswa kana kufamba zvine ruremekedzo kune mumwe nemumwe.
Chii chiri kupera?
Iyo nguva yekusiyana kwesimba rakagamuchirwa rechiratidzo nekuda kwekuchinja kwenzira yekutapurirana kana nzira dzinozivikanwa sekupera. Kupera kunoenderana nezvinhu zvakasiyana sezvataurwa pamusoro apa. Mumamiriro ezvinhu akatarwa, kupera kunoenderana nemamiriro emuchadenga akadai sekunaya kwemvura, kupenya, nezvimwewo. Mumamiriro ezvinhu anofambisa, kupera kunoenderana nezvipingamupinyi pamusoro penzira izvo zvinosiyana maererano nenguva. Izvi zvipingamupinyi zvinogadzira yakaoma kutapurirana mhedzisiro kune inotumirwa chiratidzo.
Iyo nhamba-1 inoratidza amplitude inopesana nechati yedaro yeinononoka kupera uye inokurumidza kupera mhando dzatichakurukura gare gare.
Fading types
Kufunga kwakasiyana siyana kukanganiswa kwechaneli uye chinzvimbo cheanotapurirana / anogamuchira anotevera ndiwo marudzi ekupera mune isina waya yekutaurirana system.
➤Chikero Chikuru Kupera: Kunosanganisira kurasikirwa kwenzira uye mhedzisiro yemumvuri.
➤Chikero Chiri Kuparara: Chakakamurwa kuita zvikamu zviviri zvikuru zvinoti. multipath kunonoka kupararira uye doppler kupararira. Iyo multipath inononoka kupararira inopatsanurwazve kuita flat fading uye frequency inosarudza kupera. Doppler kupararira kwakakamurwa kuita kukurumidza kupera uye kunonoka kupera.
➤Mamodheru ari kusvava: Mhando dziri pamusoro dziri kupera dzinoiswa mumhando dzakasiyana kana kugovera dzinosanganisira Rayleigh, Rician, Nakagami, Weibull nezvimwe.
Sezvatinoziva, zviratidzo zvinopera zvinoitika nekuda kwekufungidzira kubva pasi uye zvivakwa zvakapoteredza pamwe chete nezviratidzo zvakapararira kubva pamiti, vanhu uye shongwe dziripo munzvimbo huru. Kune mhando mbiri dzekusvava dzinoti. hombe iri kupera uye diki iri kupera.
1.) Yakakura Scale Inopera
Kupera kwehukuru hwakakura kunoitika kana chipingamupinyi chauya pakati pemutakuri neanogamuchira. Rudzi rwekukanganisa urwu runokonzeresa huwandu hwakakosha hwekudzikisa simba rechiratidzo. Izvi zvinodaro nekuti EM wave yakafukidzwa kana kuvharwa nechipinganidzo. Izvo zvinoenderana nekushanduka kukuru kwechiratidzo pamusoro pechinhambwe.
1.a) Kurasika kwenzira
Iyo yemahara nzvimbo nzira kurasikirwa inogona kuratidzwa sezvinotevera.
➤ Pt/Pr = {(4 * π * d)2/ λ2} = (4*π*f*d)2/c2
Kupi,
Pt = Tumira simba
Pr = Gamuchira simba
λ = wavelength
d = chinhambwe pakati pekutumira uye kugamuchira antenna
c = kumhanya kwechiedza kureva 3 x 108
Kubva paequation zvinoreva kuti chiratidzo chinofambiswa chinodzikisira chinhambwe sezvo chiratidzo chiri kuparadzirwa pamusoro penzvimbo hombe uye yakakura kubva kumagumo ekufambisa kuenda kumagumo ekugamuchira.
1.b) Shadowing maitiro
• Inoonekwa mukutaurirana kusina waya. Mvuri kutsauka kwesimba rakagamuchirwa rechiratidzo cheEM kubva paavhareji kukosha.
• Imhaka yezvipingamupinyi pamusoro penzira iri pakati pemutakuri neanogamuchira.
• Zvinoenderana nenzvimbo yenzvimbo pamwe neredhiyo frequency yeEM (ElectroMagnetic) masaisai.
2. Diki Scale Fading
Kudzikira kudiki kune chekuita nekuchinja nekukurumidza kwesimba rechiratidzo rakagamuchirwa pamusoro pechinhambwe chipfupi uye nguva pfupi.
Maererano nemultipath kunonoka kupararirakune marudzi maviri ezvikero zvidiki zvinopera zvinoti. flat fading uye frequency inosarudza kupera. Aya marudzi akawanda ekudzima anotsamira panharaunda yekuparadzira.
2.a) Kupera kwakadzikama
Iyo isina waya chiteshi inonzi yakadzika kudzima kana ichigara ichiwana uye mutsara wechikamu mhinduro pamusoro pe bandwidth iyo yakakura kupfuura bandwidth yechiratidzo chinofambiswa.
Murudzi urwu rwekudzima zvese zvikamu zve frequency yechiratidzo chakagamuchirwa chinochinja-chinja muzvikamu zvakafanana panguva imwe chete. Iyo inozivikanwawo seisina-selective fading.
• Chiratidzo BW << Channel BW
• Symbol nguva >> Kunonoka Kupararira
Mhedzisiro yekudzika kwakadzika inoonekwa sekuderera kweSNR. Aya akafuratira fading chiteshi anozivikanwa se amplitude akasiyana chiteshi kana narrowband chiteshi.
2.b) Frequency Sarudzo inopera
Iyo inokanganisa akasiyana spectral zvikamu zveredhiyo siginecha ine akasiyana amplitudes. Saka zita rinosarudza kupera.
• Chiratidzo BW > Chiteshi BW
• Symbol nguva < Kunonoka Kupararira
Maererano nekupararira kwedopplerkune mhando mbiri dzekusvava dzinoti. kukurumidza kupera uye kunonoka kupera. Aya marudzi edoppler anopararira anopera anoenderana nekumhanya kwenhare, kureva kumhanya kweanogamuchira maererano nekutapurirana.
2.c) Kukurumidza kupera
Chiitiko chekukurumidza kupera chinomiririrwa nekukurumidza kuchinja kwechiratidzo panzvimbo diki (kureva bandwidth). Kana masaini asvika kubva kumativi ese mundege, kukurumidza kupera kunozoonekwa kune ese mafambiro.
Kukurumidza kupera kunoitika kana chiteshi chekupindura mhinduro ichichinja nekukurumidza mukati menguva yechiratidzo.
• High doppler kupararira
• Nguva yechiratidzo > Nguva yekubatana
• Signal Variation <Channel variation
Aya ma paramita anokonzeresa kupararira kana nguva inosarudza kupera nekuda kwekupararira kwedoppler. Kukurumidza kupera kunokonzerwa nekuratidzwa kwezvinhu zvemuno uye kufamba kwezvinhu zvine chekuita nezvinhu izvozvo.
Mukukurumidza kupera, kugashira chiratidzo ihuwandu hwezviratidzo zvakawanda zvinoratidzwa kubva kwakasiyana siyana. Chiratidzo ichi chiverengero kana musiyano wezviratidzo zvakawanda zvinogona kuvaka kana kuparadza zvichibva pakuchinja kwechikamu pakati pazvo. Hukama hwechikamu hunoenderana nekumhanya kwekufamba, kuwanda kwekutapurirana uye kureba kwenzira.
Kukurumidza kupera kunokanganisa chimiro che baseband pulse. Kukanganisa uku kwakajeka uye kunogadziraISI(Inter Symbol Kupindira). Adaptive equalization inoderedza ISI nekubvisa mutsara kukanganisa kunokonzerwa nechiteshi.
2.d) Kunonoka kupera
Kuderera zvishoma nezvishoma kunokonzerwa nemumvuri nezvivakwa, zvikomo, makomo uye zvimwe zvinhu pamusoro penzira.
• Low Doppler Kupararira
• Symbol period <
• Signal Variation >> Channel Variation
Kuitwa kweFading modhi kana kupera kugovera
Kuitwa kwemamodhi ari kupera kana kugovaniswa kuri kupera kunosanganisira Rayleigh kupera, Rician kupera, Nakagami kupera uye Weibull kupera. Aya ekugovera chiteshi kana mamodheru akagadzirirwa kubatanidza kupera mu baseband data siginecha sezviri kuderera zvinodikanwa.
Rayleigh kupera
• MuRayleigh modhi, chete Non Line of Sight(NLOS) zvikamu zvinoteedzerwa pakati petransmitter ne receiver. Zvinofungidzirwa kuti hapana LOS nzira iripo pakati peanotumira uye anogamuchira.
• MATLAB inopa "rayleighchan" basa rekutevedzera rayleigh chiteshi modhi.
• Simba rinoparadzirwa zvakanyanya.
• Chikamu chakagoverwa zvakafanana uye chakasununguka kubva kune amplitude. Ndiwo anonyanya kushandiswa marudzi eFading mukutaurirana pasina waya.
Rician achipera
• Mune rician modhi, ese ari maviri Mutsetse Wekuona (LOS) uye asiri Mutsetse Wekuona (NLOS) zvikamu zvinoteedzerwa pakati pemupepeti neanogamuchira.
• MATLAB inopa "ricianchan" basa rekutevedzera rician chiteshi modhi.
Nakagami fading
Nakagami fadding chiteshi imhando yezviverengero inoshandiswa kurondedzera isina waya yekutaurirana nzira umo iyo yakagamuchirwa sgnal inoenda kuwanda kupera. Inomiririra nharaunda dzine mwero kusvika kune dzakanyanya kupera senge nzvimbo dzemudhorobha kana dzemudhorobha. Iyo inotevera equation inogona kushandiswa kutevedzera Nakagami inopera chiteshi modhi.
• Muchiitiko ichi tinoratidza h = r * ejΦuye kona Φ yakagoverwa zvakafanana pa [-π, π]
• Mutsauko r uye Φ unofungidzirwa kuti akazvimirira.
• Iyo Nakagami pdf inoratidzwa sepamusoro.
• MuNakagami pdf, 2σ2= E{r2}, Γ(.) ndiro basa reGamma uye k >= (1/2) chiverengero chiri kupera (madhigirii erusununguko ane chekuita nenhamba yekuwedzera Gaussion zvisina tsarukano).
• Yakatanga kugadzirwa empirically zvichibva pazviyero.
• Simba rekugamuchira pakarepo rinogoverwa neGamma. • Ne k = 1 Rayleigh = Nakagami
Weibull kupera
Iyi chiteshi ndiyo imwe nhamba yemhando inoshandiswa kutsanangura isina waya yekutaurirana chiteshi. Weibull fading chiteshi chinowanzo shandiswa kumiririra nharaunda dzine marudzi akasiyana-siyana emamiriro ari kupera anosanganisira ese ari maviri asina kusimba uye akanyanya kupera.
Kupi,
2σ2= E{r2}
• Weibull kugovera kunomiririra kumwe kuenzanirana kwekugovera kweRayleigh.
• Kana X na Y ari iid zero kureva gaussian variables, hamvuropu yeR = (X2+Y2)1/2iri Rayleigh yakagoverwa. • Zvisinei hamvuropu inotsanangurwa R = (X2+Y2)1/2, uye inoenderana pdf (simba rekugovera mbiri) ndeye Weibull yakagoverwa.
• Equation inotevera inogona kushandiswa kutevedzera Weibull fading modhi.
Mupeji rino takapfuura nemisoro yakasiyana-siyana pamusoro pekudzima sekuti chii chiri kupera chiteshi, mhando dzayo, mamodheru ari kupera, maapplication adzo, mabasa nezvimwe. Mumwe anogona kushandisa ruzivo rwakapihwa papeji ino kuti aenzanise uye awane mutsauko pakati pediki diki kupera uye chiyero chikuru kupera, musiyano pakati pe flat fading uye frequency selective fading, musiyano pakati pekukurumidza kupera uye kunonoka kupera, musiyano pakati pe rayleigh fading uye rician fading uye zvichingodaro.
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Nguva yekutumira: Aug-14-2023
