Peji rino rinotsanangura zvinhu zvekutanga zvekudzima uye mhando dzekudzima mukutaurirana kusina waya. Mhando dzeKudzima dzakakamurwa kuita kudzima kukuru uye kudzima kudiki (multipath delay spread uye doppler spread).
Kupera kwechiedza chakatsetseka uye kupera kwesarudzo dzenguva nenguva chikamu chekupera kwenzira dzakawanda apo kupera nekukurumidza uye kupera zvishoma nezvishoma chikamu chekupera kwedoppler spread. Mhando idzi dzekupera dzinoitwa zvichienderana nekugoverwa kana mamodheru eRayleigh, Rician, Nakagami neWeibull.
Nhanganyaya:
Sezvatinoziva sisitimu yekutaurirana isina waya ine transmitter nereceiver. Nzira kubva kune transmitter kuenda kune receiver haina kutsetseka uye chiratidzo chinotumirwa chinogona kupfuura nenzira dzakasiyana-siyana dzinosanganisira kurasikirwa nenzira, kudzikira kwenzira dzakawanda nezvimwewo. Kudzikira kwechiratidzo munzira kunoenderana nezvinhu zvakasiyana-siyana. Izvi inguva, mafrequency eredhiyo uye nzira kana nzvimbo yetransmitter/receiver. Nzira iri pakati petransmitter nereceiver inogona kusiyana kana kugadziriswa nguva zvichienderana nekuti transmitter/receiver yakagadzikana here kana kuti inofamba zvakanaka.
Chii chiri kupera?
Kuchinja kwenguva kwesimba rechiratidzo rinogamuchirwa nekuda kwekuchinja kwenzira yekutumira kana nzira kunozivikanwa sekudzima. Kudzima kunoenderana nezvinhu zvakasiyana-siyana sezvambotaurwa pamusoro apa. Mumamiriro ezvinhu akagadzika, kupera kunoenderana nemamiriro ekunze akadai semvura inonaya, mheni nezvimwewo. Mumamiriro ezvinhu ekufamba, kupera kunoenderana nezvipingamupinyi zviri munzira izvo zvinosiyana maererano nenguva. Zvipingamupinyi izvi zvinogadzira mhedzisiro yakaoma yekutumira kune chiratidzo chinotumirwa.
Mufananidzo-1 unoratidza chati yehukuru kana daro yemhando dzekudzima zvishoma nezvishoma uye dzinodzima nekukurumidza dzatichakurukura gare gare.
Mhando dziri kupera
Tichifunga nezvematambudziko akasiyana-siyana ane chekuita nechiteshi uye nzvimbo yemuchina wekutumira/kugamuchira, zvinotevera ndizvo zvinopera muhurongwa hwekutaurirana husina waya.
➤Kupera Kwechikero Chikuru: Kunosanganisira kurasikirwa nenzira uye mhedzisiro yemumvuri.
➤Kupera Kwechikero Chidiki: Kwakakamurwa muzvikamu zviviri zvikuru zvinoti kupararira kwekunonoka kwenzira dzakawanda uye kupararira kwedoppler. Kupararira kwekunonoka kwenzira dzakawanda kunokamurwazve mukuita kunopera kwakadzikama uye kunopera kwefrequency. Kupararira kwedoppler kunokamurwa mukuita kunopera nekukurumidza uye kunopera zvishoma nezvishoma.
➤Mamodheru anopera: Mhando dzinopera pamusoro dzinoshandiswa mumamodheru akasiyana-siyana kana kugoverwa kunosanganisira Rayleigh, Rician, Nakagami, Weibull nezvimwewo.
Sezvatinoziva, zviratidzo zvinopera zvinokonzerwa nekuratidzwa kwechiedza kubva pasi nezvivakwa zvakapoteredza pamwe chete nezviratidzo zvakapararira kubva kumiti, vanhu neshongwe dziri munzvimbo yakakura. Kune mhando mbiri dzekupera kwechiedza dzinoti, kupera kwechiedza kukuru uye kupera kwechiedza chidiki.
1.) Kupera Kwechikero Chikuru
Kudzima kukuru kunoitika kana chipingamupinyi chikapinda pakati petransmitter nereceiver. Rudzi urwu rwekupindirana runokonzera kudzikiswa kukuru kwesimba remasaini. Izvi zvinokonzerwa nekuti EM wave inovharirwa kana kuvharwa nechipingamupinyi. Izvi zvine chekuita nekuchinja kukuru kwechiratidzo padaro.
1.a) Kurasikirwa nenzira
Kurasikirwa kwenzira yemahara kunogona kuratidzwa seizvi.
➤ Pt/Pr = {(4 * π * d)2/ λ2} = (4*π*f*d)2/c2
Kupi,
Pt = Simba rekutumira
Pr = Gamuchira simba
λ = kureba kwehurefu
d = chinhambwe pakati pekutumira nekugamuchira antenna
c = kumhanya kwechiedza kureva 3 x 108
Kubva muequation zvinoreva kuti chiratidzo chinotumirwa chinodzikira kana chiratidzo chave kure sezvo chiri kupararira panzvimbo yakakura kubva kumagumo ekutumira kuenda kumagumo ekugamuchira.
1.b) Mhedzisiro yemumvuri
• Zvinoonekwa mukutaurirana kusina waya. Kusviba kutsauka kwesimba rinogamuchirwa rechiratidzo cheEM kubva paavhareji.
• Izvi zvinokonzerwa nezvipingamupinyi munzira iri pakati pemutumidziri nemugamuchiri.
• Zvinoenderana nenzvimbo pamwe chete neredhiyo yemafungu eEM (ElectroMagnetic).
2. Kupera Kwechikero Chidiki
Kudzima kwesimba rechiratidzo kudiki kunokonzerwa nekuchinja-chinja kwesimba rechiratidzo chinogamuchirwa munguva pfupi uye munguva pfupi.
Maererano nekupararira kwekunonoka kwenzira dzakawandaKune mhando mbiri dzesmall scale fading dzinoti flat fading uye frequency selective fading. Mhando idzi dze multipath fading dzinoenderana nenzvimbo yekupararira.
2.a) Kupera kwakati sandara
Chiteshi chewaya chisina waya chinonzi chinopera simba kana chiine mhinduro yekuwedzera uye yechikamu chemutsetse pamusoro pebandwidth yakakura kupfuura bandwidth yechiratidzo chinotumirwa.
Murudzi urwu rwekudzima, zvikamu zvese zvefrequency zvechiratidzo chinogamuchirwa zvinochinja-chinja zvakaenzana panguva imwe chete. Zvinozivikanwawo sekusadzima kusingasarudze.
• Chiratidzo BW << Chiteshi BW
• Nguva yezviratidzo >> Kupararira kweKunonoka
Mhedzisiro yekuderera kwechiedza inoonekwa sekuderera kweSNR. Aya machannels ekuderera kwechiedza anozivikanwa seamplitude varying channels kana kuti narrowband channels.
2.b) Kupera kwehuwandu Kusarudza kupera
Inokanganisa zvikamu zvakasiyana zvespectral zvesignali yeredhiyo ine amplitudes dzakasiyana. Nokudaro zita rinosarudza kupera.
• Chiratidzo BW > Chiteshi BW
• Nguva yechiratidzo < Kunonoka Kupararira
Maererano nekupararira kwedopplerKune mhando mbiri dzekudzima dzinoti, kukurumidza kupera uye kunonoka kupera. Mhando idzi dzekudzima dzinoenderana nekumhanya kwefoni, kureva kumhanya kwemugamuchiri maererano netransmitter.
2.c) Kupera simba nekukurumidza
Chiitiko chekudzima nekukurumidza chinomiririrwa nekuchinja-chinja kwechiratidzo munzvimbo diki (kureva bandwidth). Kana zviratidzo zvasvika kubva kumativi ese ari mundege, kupera nekukurumidza kuchaonekwa kune ese mafambiro.
Kupera kwesimba kunoitika kana mhinduro yemuchina ichichinja nekukurumidza mukati menguva yechiratidzo.
• Kupararira kwedoppler yakawanda
• Nguva yezviratidzo > Nguva yekubatana
• Kuchinja kweChiratidzo < Kuchinja kweChiteshi
Izvi zvinokonzera kupararira kwema frequency kana kupera kwenguva nekuda kwekupararira kwedoppler. Kupera kwekukurumidza kunokonzerwa nekuratidzwa kwezvinhu zvemuno uye kufamba kwezvinhu zvichienzaniswa nezvinhu izvozvo.
Mukukurumidza kupera, chiratidzo chekugamuchira chiratidzo chinosanganisira huwandu hwezviratidzo zvakawanda zvinoratidzwa kubva panzvimbo dzakasiyana-siyana. Chiratidzo ichi chinosanganisira huwandu kana musiyano wezviratidzo zvakawanda zvinogona kuvaka kana kuparadza zvichibva pakuchinja kwechikamu pakati pazvo. Hukama hwechikamu hunoenderana nekumhanya kwekufamba, kuwanda kwekutumira uye kureba kwenzira.
Kupera nekukurumidza kunokanganisa chimiro chekurova kwesimbi yebaseband. Kukanganisa uku kwakanangana uye kunogadziraISI(Inter Symbol Interference). Adaptive equalization inoderedza ISI nekubvisa linear distortion inokonzerwa nechannel.
2.d) Kupera zvishoma nezvishoma
Kupera zvishoma nezvishoma kunokonzerwa nemumvuri wezvivakwa, zvikomo, makomo nezvimwe zvinhu zviri munzira.
• Kupararira kweDoppler Yakaderera
• Nguva yechiratidzo <
• Kuchinja kweSignali >> Kuchinja kweChiteshi
Kushandiswa kwemamodheru eFading kana kugoverwa kwefading
Kushandiswa kwemamodheru anodzima kana kugoverwa kwefading kunosanganisira Rayleigh fading, Rician fading, Nakagami fading uye Weibull fading. Aya ma channel distributions kana mamodheru akagadzirwa kuti aise fading mu baseband data signal zvichienderana nezvinodiwa ne fading profile.
Kupera kweRayleigh
• Mumuenzaniso weRayleigh, zvikamu zveNon Line of Sight (NLOS) chete ndizvo zvinotevedzerwa pakati petransmitter nereceiver. Zvinofungidzirwa kuti hapana nzira yeLOS iripo pakati petransmitter nereceiver.
• MATLAB inopa basa rekuti "rayleighchan" kutevedzera modhi yechiteshi cherayleigh.
• Simba racho rinoparadzirwa zvakanyanya.
• Chikamu ichi chakapararira zvakaenzana uye chakazvimiririra kubva pahukuru. Ndiwo marudzi anonyanya kushandiswa eFading mukutaurirana kusina waya.
Kupera simba kweRician
• Mumuenzaniso weRician, zvese zviri zviviri Line of Sight (LOS) uye zvisiri Line of Sight (NLOS) zvinotevedzerwa pakati petransmitter nereceiver.
• MATLAB inopa basa rekuti "ricianchan" kutevedzera muenzaniso weRician channel.
Nakagami iri kupera simba
Nakagami fadding channel imhando yenhamba inoshandiswa kutsanangura nzira dzekutaurirana dzisina waya umo sgnal inogamuchirwa inodzikira nekufamba nenzira dzakawanda. Inomiririra nzvimbo dzine kupera kuri pakati nepakati kusvika kwakanyanya senge nzvimbo dzemumaguta kana dzemumaguta. Equation inotevera inogona kushandiswa kutevedzera muenzaniso weNakagami fading channel.
• Muchiitiko ichi tinoratidza h = r*ejΦuye kona Φ inogoverwa zvakaenzana pa [-π, π]
• Variable r na Φ vanofungidzirwa kuti vakazvimirira.
• Nakagami pdf inoratidzwa sezviri pamusoro apa.
• MuNakagami pdf, 2σ2= E{r2}, Γ(.) ibasa reGamma uye k >= (1/2) inhamba iri kupera (madhigirii erusununguko ane chekuita nehuwandu hwezvakaiswa Gaussion random variables).
• Pakutanga yakagadzirwa zvichibva pakuongorora kwakaitwa.
• Simba rekugamuchira ipapo ipapo rinogoverwa neGamma. • Na k = 1 Rayleigh = Nakagami
Kupera kweWeibull
Iyi nzira ndeimwe nzira yekuverenga inoshandiswa kutsanangura nzira yekutaurirana isina waya. Nzira yeWeibull fading inowanzoshandiswa kumiririra nzvimbo dzine marudzi akasiyana-siyana emamiriro ekudzima anosanganisira kupera simba uye kupera kwakanyanya.
Kupi,
2σ2= E{r2}
• Kugoverwa kweWeibull kunomiririra kumwe kutsanangurwa kwekugoverwa kweRayleigh.
• Kana X na Y zviri mavariable epakati pe gaussian e iid zero, envelopu ye R = (X)2+ Y2)1/2Rayleigh inogoverwa. • Zvisinei, hamvuropu inotsanangurwa R = (X)2+ Y2)1/2, uye pdf inoenderana nayo (power distribution profile) ndiyo Weibull yakagoverwa.
• Equation inotevera inogona kushandiswa kutevedzera modhi yeWeibull fading.
Mupeji rino takaongorora nyaya dzakasiyana-siyana pamusoro pekudzima senge chiri kufa, mhando dzacho, mamodheru ekudzima, mashandisirwo azvo, mabasa azvo nezvimwewo. Munhu anogona kushandisa ruzivo rwuri papeji rino kuti aenzanise uye awane mutsauko uripo pakati pekudzima kudiki nekudzima kukuru, mutsauko uripo pakati pekudzima kwakadzika uye kudzima kwefrequency, mutsauko uripo pakati pekudzima nekukurumidza nekudzima zvishoma nezvishoma, mutsauko uripo pakati pekudzima kwerayleigh nekudzima kwerician nezvimwewo.
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Nguva yekutumira: Nyamavhuvhu-14-2023
