Eli phepha lichaza UkuBulala okusisiseko kunye neentlobo zokuphela konxibelelwano olungenazingcingo. Iindidi zokuBulala zohlulwe zibe sisikali esikhulu esibunayo kunye nesikali esincinci esinciphayo (ukulibaziseka kweendlela ezininzi kunye nokusasazeka kwedoppler).
Ukuphela kweflethi kunye nokukhetha ukuphelelwa rhoqo yinxalenye yobuninzi beendlela apho ukuncipha okukhawulezayo kunye nokuncipha okucothayo kuyinxenye yokuncipha kwe-doppler. Ezi ndidi eziphelayo ziphunyezwa ngokweRayleigh, Rician, Nakagami kunye ne-Weibull unikezelo okanye imifuziselo.
Intshayelelo:
Njengoko sisazi inkqubo yonxibelelwano engenazingcingo iquka umthumeli kunye nomamkeli. Indlela esuka kumthumeli ukuya kumamkeli ayigudi kwaye isignali egqithisiweyo inokudlula kwiindidi ezahlukeneyo zokuthomalalisa kubandakanywa ukulahleka kwendlela, ukucutha iindlela ezininzi njalo njalo. Ukunciphisa umqondiso endleleni kuxhomekeke kwizinto ezahlukeneyo. Lixesha, amaza kanomathotholo kunye nendlela okanye indawo yesidlulisi/umamkeli. Ijelo eliphakathi komthumeli kunye nomamkeli linokuba lixesha lokwahluka okanye elizinzileyo kuxhomekeke ekubeni umthumeli/umamkeli uzinzile okanye uyashukuma ngokubhekiselele komnye nomnye.
Yintoni ukuphelelwa?
Ukwahluka kwexesha lamandla omqondiso afunyenweyo ngenxa yotshintsho kwindlela yothumelo okanye iindlela zaziwa njengokuncipha. Ukuncipha kuxhomekeke kwizinto ezahlukeneyo njengoko kukhankanyiwe ngasentla. Kwimeko esisigxina, ukuncipha kuxhomekeke kwiimeko zomoya ezifana nemvula, ukukhanya njalo njalo. Kwimeko ehambayo, ukuncipha kuxhomekeke kwimiqobo engaphaya kwendlela eyahlukayo malunga nexesha. Le miqobo idala iziphumo ezintsonkothileyo zothumelo kumqondiso ogqithisiweyo.
Umzobo-1 ubonisa i-amplitude xa ithelekiswa netshati yomgama yokuphela kancinci kunye neentlobo eziphela ngokukhawuleza esiza kuzixoxa kamva.
Iintlobo eziphelayo
Ukuthathela ingqalelo ukonakaliswa okunxulumene nejelo kunye nendawo yesithumeli/umamkeli zilandelayo ziindidi zokuphela kwenkqubo yonxibelelwano engenazingcingo.
➤UkuBulala koMda omkhulu: Kubandakanya ukulahleka kwendlela kunye neziphumo zesithunzi.
➤UkuBulala koMkhamo omncinci: Wohlulwe ngokweendidi ezimbini eziphambili ezizezi. Ukulibaziseka kweendlela ezininzi kunye nokusasazeka kwe-doppler. Ukusasazeka kokulibaziseka kweendlela ezininzi kwahlulahlulwe ngakumbi kwi-flading ethe tyaba kunye nokuphela kokukhetha rhoqo. Ukusasazeka kwe-Doppler yohlulwe ngokuphela ngokukhawuleza kunye nokuncipha ngokukhawuleza.
➤Iimodeli eziphelayo: Iindidi eziphezulu eziphelayo ziphunyezwa kwiimodeli ezahlukeneyo okanye usasazo oluquka uRayleigh, uRician, uNakagami, Weibull njl.
Njengoko sisazi, imiqondiso ephelayo iyenzeka ngenxa yokubonakaliswa komhlaba kunye nezakhiwo ezijikelezileyo kunye nemiqondiso esasazekileyo evela kwimithi, abantu kunye neenqaba ezikhoyo kwindawo enkulu. Zimbini iindidi zokufiphala ezizezi. ukuncipha okukhulu kunye nokuncipha kwesantya esincinci.
1.) UkuBulala kweSikali esikhulu
Ukuncipha komlinganiselo omkhulu kwenzeka xa umqobo ungena phakathi komthumeli kunye nomamkeli. Olu hlobo lokuphazamiseka lubangela inani elibalulekileyo lokunciphisa amandla omqondiso. Oku kungenxa yokuba i-EM wave isithunzi okanye ivalwe ngumqobo. Inxulumene nokuguquguquka okukhulu komqondiso kumgama.
1.a) Ukulahleka kwendlela
Ilahleko yendawo yasimahla ingabonakaliswa ngolu hlobo lulandelayo.
➤ Pt/Pr = {(4 * π * d)2/ λ2} = (4*π*f*d)2/c2
Apho,
Pt = Thumela amandla
Pr = Fumana amandla
λ = ubude bamaza
d = umgama phakathi kothumelo nokufumana i-eriyali
c = isantya sokukhanya okt 3 x 108
Ukusuka kwinxaki kuthetha ukuba isiginali egqithisiweyo ithomalalisa kumgama njengoko umqondiso usasazwa kwindawo enkulu kunye nenkulu ukusuka ekupheleni kodluliselo ukuya esiphelweni sokufumana.
1.b) Isiphumo somthunzi
• Ijongwa kunxibelelwano olungenazingcingo. Ukwenza isithunzi kukutenxa kumandla afunyenweyo wophawu lwe-EM ukusuka kwixabiso eliphakathi.
• Kusisiphumo semiqobo kwindlela ephakathi komthumeli kunye nomamkeli.
• Kuxhomekeke kwindawo ekuyo nakunomathotholo wamaza e-EM (ElectroMagnetic).
2. Isikali esiNcinci sokuBulala
Ukufiphala kwesikali esincinci kunento yokwenza nokuguquguquka okukhawulezileyo kwamandla ophawu olufunyenweyo kumgama omfutshane kakhulu kunye nexesha elifutshane.
Ngenxa yeukulibaziseka kweendlela ezininzikukho iindidi ezimbini zesikali esincinci esiphelayo, oko kukuthi. Ukufiphala okuthe tyaba kunye nokuncipha okukhethiweyo rhoqo. Ezi ntlobo zokwahlukana kwendlela ezininzi zixhomekeke kwindawo yosasazo.
2.a) Ukunyamalala okuthe tyaba
Itshaneli engenazingcingo kuthiwa i-flat fading ukuba inenzuzo eqhubekayo kunye nempendulo yesigaba somgca kwi-bandwidth enkulu kune-bandwidth yesiginali edlulisiweyo.
Kolu hlobo lokufiphala onke amacandelo e-frequency ye-signal efunyenweyo aguquguquka ngomlinganiselo ofanayo ngaxeshanye. Ikwabizwa ngokuba yi-non-selective fading.
• Umqondiso u-BW << Ijelo le-BW
• Ixesha leSimboli >> Ukulibazisa ukuSasazeka
Isiphumo sokufiphala kweflethi sibonwa njengokuncipha kwe-SNR. Ezi tshaneli ezisicaba ziyaziwa ngokuba yi-amplitude eyahlukileyo itshaneli okanye imijelo emxinwa.
2.b) Ukufiphala rhoqo okukhethiweyo
Ichaphazela amacandelo e-spectral ahlukeneyo esignali yerediyo ene-amplitudes ezahlukeneyo. Kungoko igama elikhethiweyo liyaphela.
• Umqondiso BW > Ijelo BW
• Ixesha leSimboli < Ukulibazisa ukuSasazeka
Ngenxa yeukusasazeka kwe-dopplerkukho iindidi ezimbini zokufiphala ezizezi. ukuncipha ngokukhawuleza kunye nokuncipha ngokukhawuleza. Ezi ntlobo ze-doppler zisasazeka zixhomekeke kwisantya esihambahambayo, oko kukuthi, isantya somamkeli ngokuphathelele kwi-transmitter.
2.c) Ukuphela ngokukhawuleza
Isenzeko sokuphela ngokukhawuleza simelwe kukuguquguquka okukhawulezileyo komqondiso kwiindawo ezincinci (okt i-bandwidth). Xa imiqondiso ifika isuka kuzo zonke izikhokelo zenqwelomoya, ukufiphala okukhawulezayo kuya kujongwa kuwo onke amacala entshukumo.
Ukuphela ngokukhawuleza kwenzeka xa impendulo yempembelelo yetshaneli itshintsha ngokukhawuleza kakhulu ngexesha lesimboli.
• Ukusasazeka kwe-doppler ephezulu
• Ixesha lophawu > Ixesha lokuyondelelana
• Ukwahluka koMqondiso < Ukwahluka kweChaneli
Ezi parameters zikhokelela ekuhlakazekeni rhoqo okanye ukucima okukhethiweyo kwexesha ngenxa yokusasazeka kwe-doppler. Ukuphela ngokukhawuleza kusisiphumo sokubonakaliswa kwezinto zasekhaya kunye nokushukuma kwezinto ezinxulumene nezo zinto.
Ukuphela ngokukhawuleza, isiginali yokwamkela sisimbuku semiqondiso emininzi ebonakaliswa kwiindawo ezahlukeneyo. Lo mqondiso sisixa okanye umahluko wemiqondiso emininzi enokwakha okanye eyonakaliseyo ngokusekelwe kutshintsho lwesigaba esizalanayo phakathi kwabo. Ubudlelwane besigaba buxhomekeke kwisantya sentshukumo, ukuphindaphindwa kothumelo kunye nobude bendlela ehambelanayo.
Ukuphela ngokukhawuleza kuphazamisa ubume be-baseband pulse. Oku kugqwethwa kumgca kwaye kuyadalaISI(Uphazamiseko lweSimboli). Ukulinganisa okuguquguqukayo kunciphisa i-ISI ngokususa ukuguqulwa komgca owenziwe ngumtshaneli.
2.d) Ukuphela kancinci
Ukufiphala kancinci kusisiphumo somthunzi wezakhiwo, iinduli, iintaba kunye nezinye izinto eziphezu kwendlela.
• Ukusasazeka kweDoppler ephantsi
• Ixesha lophawu <
• Ukwahluka koMqondiso >> Ukwahluka kweSitishi
Ukuphunyezwa kweemodeli eziBumayo okanye ukusasazwa oluphelayo
Ukuphunyezwa kweemodeli eziphelayo okanye ukusasazwa oluphelayo luquka uRayleigh fading, Rician fading, Nakagami fading kunye neWeibull fading. Ezi zisasazo zetshaneli okanye iimodeli ziyilelwe ukubandakanya ukufiphala kumqondiso wedatha ye-baseband ngokweemfuno zeprofayile eziphelayo.
I-Rayleigh iyancipha
• Kwimodeli yeRayleigh, kuphela ngamacandelo angeNgawo umgca wokuSight(NLOS) alinganisiweyo phakathi komthumeli kunye nomamkeli. Kucingelwa ukuba akukho ndlela ye-LOS ekhoyo phakathi komthumeli kunye nomamkeli.
• I-MATLAB ibonelela ngomsebenzi we-"rayleighchan" ukulinganisa imodeli yetshaneli yerayleigh.
• Amandla asasazwa ngokukhawuleza.
• Isigaba sisasazwa ngokufanayo kwaye sizimele kwi-amplitude. Yeyona ntlobo isetyenziswayo yokuFading kunxibelelwano olungenazingcingo.
URician uyaphela
• Kwimodeli ye-rician, zombini iinxalenye zeNdlela yokuJongana (LOS) kunye ne-non Line of Sight(NLOS) ziye zalingisa phakathi komthumeli kunye nomamkeli.
• I-MATLAB ibonelela ngomsebenzi we-"ricianchan" ukulinganisa imodeli yesitishi.
I-Nakagami iyaphela
Ijelo leNakagami fadding yimodeli yeenkcukacha-manani esetyenziswa ukuchaza amajelo onxibelelwano angenazingcingo apho i-sgnal efunyenweyo idlula kwiindlela ezininzi. Imele imo engqongileyo enobuphakathi ukuya ebubunzimeni njengemimandla yasezidolophini okanye yasezidolophini. Le nxaki ilandelayo ingasetyenziselwa ukulinganisa imodeli yetshaneli yeNakagami.
• Kule meko sichaza h = r*ejΦkunye ne-engile Φ isasazwe ngokufanayo kwi [-π, π]
• Uguqulo r kunye no-Φ zithathwa njengezizimeleyo.
• I-pdf yeNakagami ichazwe ngolu hlobo lungasentla.
• Kwi-pdf yeNakagami, 2σ2= E{r2}, Γ(.) ngumsebenzi weGamma kwaye k >= (1/2) linani elicimayo (amaqondo enkululeko anxulumene nenani leGaussion eguquguqukayo eyongeziweyo).
• Ekuqaleni yayiphuhliswe ngokweempirically ngokusekelwe kwimilinganiselo.
• Amandla okufumana ngoko nangoko asasazwa i-Gamma. • Nge k = 1 Rayleigh = Nakagami
I-Weibull iyaphela
Eli jelo lelinye imodeli yamanani esetyenziselwa ukuchaza itshaneli yonxibelelwano engenazingcingo. Umjelo we-Weibull fading uqhele ukusetyenziswa ukumela imeko-bume eneendidi ezahlukeneyo zeemeko eziphelayo ezibandakanya zombini ubuthathaka kunye nokuncipha okukhulu.
Apho,
2 σ2= E{r2}
• Unikezelo lwe-Weibull lumele olunye ulungelelwaniso losasazo lweRayleigh.
• Xa u-X no-Y bezii-iid zero kuthetha izinto eziguquguqukayo ze-gaussian, imvulophu ye-R = (X2+ Y2)1/2iRayleigh isasazwe. • Nangona kunjalo imvulophu ichazwa R = (X2+ Y2)1/2, kunye ne-pdf ehambelanayo (iprofayili yokuhanjiswa kwamandla) yi-Weibull isasazwe.
• Le nxaki ilandelayo ingasetyenziswa ukulinganisa imodeli ye-Weibull fading.
Kweli phepha sidlule kwimixholo eyahluka-hlukeneyo yokuphela kwayo enje ngokuba yintoni itshaneli ephelayo, iintlobo zayo, imifuziselo ephelayo, usetyenziso lwazo, imisebenzi njalo njalo. Umntu unokusebenzisa ulwazi olunikeziweyo kweli phepha ukuze athelekise kwaye afumane umahluko phakathi kokuphela komlinganiselo omncinci kunye nokuncipha okukhulu, umahluko phakathi kokuphela kweflethi kunye nokuncipha okukhethiweyo okuphindaphindiweyo, umahluko phakathi kokuphela ngokukhawuleza kunye nokuncipha kancinci, umahluko phakathi kokuphela kwerayleigh kunye nokuncipha kwe-rician kunye njalo njalo.
E-mail:info@rf-miso.com
Ifowuni: 0086-028-82695327
iwebhusayithi: www.rf-miso.com
Ixesha lokuposa: Aug-14-2023
