Ngā Kaupapa Taketake o te Whakangaromanga me ngā Momo Whakangaromanga i roto i te Whakawhitiwhiti Kōrero Ahokore

I runga i ngā ngoikoretanga e pā ana ki te hongere me te tūranga o te tuku/kaiwhiwhi, koinei ngā momo memeha o te pūnaha whakawhitiwhiti kōrero ahokore.
➤Te Whakangaromanga Nui: Kei roto ko te ngaronga ara me ngā pānga atarangi.
➤Te Whakaroa Iti: E rua ngā wāhanga matua, arā, te horapa whakaroa maha-ara me te horapa doppler. Ka wehea anō te horapa whakaroa maha-ara ki te whakaroa papatahi me te whakaroa auau-whiriwhiri. Ka wehea te horapa Doppler ki te whakaroa tere me te whakaroa puhoi.
➤Ngā tauira memeha: Ka whakatinanahia ngā momo memeha o runga ake nei i roto i ngā tauira, i ngā tohatoha rānei, tae atu ki a Rayleigh, Rician, Nakagami, Weibull me ētahi atu.

E mōhio ana tātou, ka puta ngā tohu memeha nā ngā whakaata mai i te whenua me ngā whare e karapoti ana, tae atu ki ngā tohu marara mai i ngā rākau, ngā tāngata me ngā pourewa kei roto i te rohe whānui. E rua ngā momo memeha, arā, te memeha nui me te memeha iti.

1.) Te memeha nui

Ka puta te memeha nui ina tae mai he arai i waenganui i te tuku me te kaiwhiwhi. Ka nui te hekenga o te kaha o te tohu e tēnei momo pokanoa. Nā te mea kei te atarangi, kei te āraia rānei te ngaru EM e te arai. E pā ana tēnei ki ngā piki me ngā heke nui o te tohu i tawhiti.

1.a) Te ngaronga o te ara

Ka taea te whakaatu i te ngaronga o te ara mokowā kore utu penei.
➤ Pt/Pr = {(4 * π * d)²/ λ²} = (4*π*f*d)²/c²
Kei hea,
Pt = Mana tuku
Pr = Mana whiwhi
λ = te roangaru
d = te tawhiti i waenga i te pūihi tuku me te pūihi whiwhi
c = te tere o te mārama, arā, 3 x 10⁸

Mai i te whārite, e kīia ana ka ngoikore te tohu i tukuna i tawhiti i te mea ka horahia te tohu ki te rohe nui haere mai i te pito tuku ki te pito whiwhi.

1.b) Pānga atarangi

• Ka kitea tēnei i roto i te whakawhitiwhiti kōrero ahokore. Ko te atarangi he rerekētanga o te mana i whiwhihia o te tohu EM mai i te uara toharite.
• He hua tēnei nō ngā arai i te ara i waenganui i te tuku me te kaiwhiwhi.
• Kei te tūnga whenua me te auau reo irirangi o ngā ngaru EM (Electromagnetic) hoki.

2. Te memeha haere o te tauine iti

Ko te memeha iti e pā ana ki ngā piki me ngā heke tere o te kaha o te tohu e whiwhihia ana i roto i te tawhiti poto me te wā poto.

I runga ite horapa whakaroa maha-araE rua ngā momo memeha iti, arā, te memeha papatahi me te memeha auau whiriwhiri. Ka whakawhirinaki ēnei momo memeha maha-ara ki te taiao horapa.

2.a) Te memeha papatahi

Ka kiia te hongere ahokore he memeha papatahi mēnā he pikinga pumau me te urupare ā-wāhanga rārangi i runga i te whānuitanga whānui e nui ake ana i te whānuitanga whānui o te tohu kua tukuna.

I roto i tēnei momo memeha, ka rerekē haere ngā wāhanga auau katoa o te tohu e whiwhihia ana i roto i ngā ōwehenga ōrite i te wā kotahi. E mōhiotia ana hoki ko te memeha kore-whiriwhiri.

• Tohu BW << Hongere BW
• Wā tohu >> Horahanga whakaroa

Ko te pānga o te memeha papatahi ka kitea ko te hekenga o te SNR. E mōhiotia ana ēnei hongere memeha papatahi ko ngā hongere rerekē te amplitude, ko ngā hongere whaiti rānei.

2.b) Auautanga Kōwhiringa memeha

Ka pā ki ngā wāhanga hihi rerekē o te tohu reo irirangi me ngā kaha rerekē. Nō reira te ingoa o te memeha whiriwhiri.

• Tohu BW > Hongere BW
• Wā tohu < Horahanga whakaroa

I runga ihorapa dopplerE rua ngā momo memeha, arā, te memeha tere me te memeha puhoi. Ko ēnei momo memeha horapa doppler e whakawhirinaki ana ki te tere pūkoro, arā, te tere o te kaiwhiwhi e pā ana ki te tuku.

2.c) Te memeha tere

Ko te āhua o te memeha tere e tohuhia ana e ngā piki me ngā heke tere o te tohu i runga i ngā wāhi iti (arā, te whānui o te whānui). Ina tae mai ngā tohu mai i ngā ahunga katoa o te papa, ka kitea te memeha tere mō ngā ahunga nekehanga katoa.

Ka puta te memeha tere ina tino tere te hurihanga o te urupare akiaki hongere i roto i te roanga o te tohu.

• Te horapa doppler teitei
• Wā tohu > Wā taurite
• Rerekētanga Tohu < Rerekētanga Hongere

Ko te hua o ēnei tawhā ko te horapa auau, ko te memeha wā rānei nā te horapa doppler. Ko te memeha tere he hua o ngā whakaata o ngā mea ā-rohe me te nekehanga o ngā mea e pā ana ki aua mea.

I roto i te memeha tere, ko te tohu whiwhi he tapeke o ngā tohu maha e whakaatahia ana mai i ngā mata rerekē. Ko tēnei tohu he tapeke, he rerekētanga rānei o ngā tohu maha ka taea te hanga, te whakangaro rānei i runga i te nekehanga ā-wāhanga i waenganui i a rātou. Ko ngā whanaungatanga ā-wāhanga ka whakawhirinaki ki te tere o te nekehanga, te auau o te tuku me te roa o te ara ā-wāhanga.

Ka whakapōturitia te āhua o te pāoro turanga e te memeha tere. He rārangi tēnei whakapōturi, ā, ka putaISI(Whakakorenga Tohu Iwi). Ka whakaitihia te ISI e te whakataurite urutau mā te tango i te whakapōturitanga rārangi i puta mai i te hongere.

2.d) Te memeha haere

Ko te memeha haere o te ara he hua nō te atarangi e taupokina ana e ngā whare, e ngā pukepuke, e ngā maunga me ērā atu mea i runga i te ara.

• Te horapa iti o te Doppler
• Wā tohu <
• Rerekētanga Tohu >> Rerekētanga Hongere

Te whakatinanatanga o ngā tauira memeha, ngā tohatoha memeha rānei

Ko ngā whakatinanatanga o ngā tauira memeha, ngā tohatoha memeha rānei ko te memeha Rayleigh, te memeha Rician, te memeha Nakagami me te memeha Weibull. Kua hangaia ēnei tohatoha hongere, tauira rānei hei whakauru i te memeha ki roto i te tohu raraunga turanga e ai ki ngā whakaritenga kōtaha memeha.

Te memeha haere o Rayleigh

• I roto i te tauira Rayleigh, ko ngā wāhanga Kore-Raina-Tirohanga (NLOS) anake ka whakatauirahia i waenga i te tuku me te kaiwhiwhi. E whakaarohia ana kāore he ara LOS i waenga i te tuku me te kaiwhiwhi.
• Ka whakaratohia e MATLAB te mahi "rayleighchan" hei whakatauira i te tauira hongere rayleigh.
• Ka tohatohahia te mana ki te taupūnga.
• He ōrite te tohatoha o te āhua, ā, he motuhake mai i te kaha. Koinei te momo Whakangaromanga e whakamahia whānuitia ana i roto i te whakawhitiwhiti kōrero ahokore.

Te memeha haere o Riki

• I roto i te tauira Rician, ka whakatauirahia ngā wāhanga Raina Tirohanga (LOS) me ngā wāhanga kore-Raina Tirohanga (NLOS) i waenganui i te tuku me te kaiwhiwhi.
• Ka whakaratohia e MATLAB te mahi "ricianchan" hei whakatauira i te tauira hongere rician.

Ngāwari o Nakagami

Ko te hongere memeha Nakagami he tauira tatauranga e whakamahia ana hei whakaahua i ngā hongere whakawhitiwhiti ahokore e pāngia ana e te memeha maha-ara o te tohu kua whiwhihia. E tohu ana i ngā taiao he memeha ngawari ki te kino pērā i ngā tāone nui, ngā tāone iti rānei. Ka taea te whakamahi i te whārite e whai ake nei hei whakatauira i te tauira hongere memeha Nakagami.