Pham Thj Minh Nguyet vd dig Tap chi KHOA HOC & CONG NGHE 81(05): 109- 114
ANH HlTONG CUA KHI QUYEN DEN TRUYEN DAN VO TUYEN TRONG DIEU K I E N KHI HAU TAI VIET NAM
Pham Thj Minh Nguyet'*, Tran Anh Tha^g^ Nguyin Dang Qui'
'Trudng CD Dien tu - Dien Ignh Ha Not. 'Trudng DH Ky thuat Cong nghiep- DH Thai Nguyen Vien Khoa hoc Khi tugng thuy van va moi trirdng - Bo Tdi nguyen va Moi trudng
TOMTAT
Cac yeu td khi hau nhu nhiet do, mua, suong md, tuyet... anh hudng rat Idn den chdt lugng truyin dan vd tuyen. Su ndng len loan cau do hieu dng khi nha kinh nhan tao gay ra bien ddi khi hau cd tac dgng nhat dinh den cau trdc cda khi quyen (mdi trudng truyen dan chinh cda sdng vd tuyen dien td). Bai bao nay de cap den anh hudng cua khi hau len truyen dan vd luyln, dac biet la anh hudng do mua - mdt trong sd cac yeu td chinh cua khi hau nhiet ddi gid mda d Viet Nam, ddng thdi budc dau nghien cdu md phdng suy hao tin hieu vd tuyen do mua, tu dd dua ra mot sd nhan xet phuc vu cho viec thiet ke cac tuyen truyen din vi ba mat ddt tdm nhin thdng (LOS) phu hgp vdi dieu kien khi hau Viet Nam.
Tu- khoa: Khi hdu nhiet ddi, Bien doi khi hdu, Truyen ddn vd tuyen, Suy hao do mua, truyen ddn viba MO DAU
Sir tac dgng cua mdi trudng khi quyen den tin hieu vd tuyen ddng mot vai trd quan trgng trong viec thiet ke ede dudng truyen ddn vd tuyen boat dgng tu cdc dai tdn so tren lOGHz.
Trong dd, su hdp thu, phdn xa vd tdn xa sdng vd tuyen tu cdc gigt mua ddn den suy hao tin hieu va Iam suy gidm kha nang, do tin cay cua he thdng truyen ddn vd tuyen. Tdn sd cdng cao thi muc do suy hao tin hieu do mua cdng tang manh vd bien ddi theo khu vuc dja ly, ddc biet tai cdc khu vuc nhiet ddi vd xich dao.
Chinh vi vay dieu quan trgng Id ehung la phdi dua ra dugc du doan chinh xac ve suy hao tin hieu do mua eho cdc dudng truyen sdng.
Trudc day, viec du dodn suy hao tin hieu vd tuyen do mua su dung phuong phdp ngoai suy kel qua do theo cdc dja diem, tan sd va do cao khac nhau. Tuy nhien do linh chat phirc tap vd su thay ddi cua lugng mua theo tung khu vuc lam cho each tiep can nay thudng khdng cho ket qud chinh xdc.
Trong thdi gian gdn ddy, nhieu bdi viet vd cdng trinh nghien cuu dd dua ra cdc phuang phdp liep can vd cong cu khde nhau de gidi quyet vdn de ndy. Muc dich cua cdc phucmg phdp ndy Id cung cap cdc cong cu de du dodn lugng mua va su suy gidm cudng do mua d dang bdn dd dudng ddng muc cho cdc nhd
' Tel; 0986385855
thiet ke he thong truyen ddn (nhu cdc he thdng ve tinh d cdc nude nam trong khu vuc nhiet ddi vd xich dao — Nigeria, Sudan). Cdc cong cu ndy dugc su dung de thiet ke so bg cdc dudng truyen ddn vo luyen vi ba mat dat vd ve linh [7, 8, 9].
Mot van de ddt ra trong thuc te Id tai Viet Nam, khdng chi Id mgl qudc gia ndm trong khu vuc nhiet ddi gid mua md cdn cd dja binh phuc lap nen da chia khi hau Viet Nam ra bdy vung cd khi hdu khac nhau: Tdy Bde, Ddng Bde, Ddng bang Bac Bg, Bde Trung Bg, Nam Trung Bg, Tdy Nguyen va Nam Bg [ 1 ].
Vi vay, bdi bdo ndy da budc ddu de xuat den viec linh todn md phong suy hao tin hieu vd tuyen do mua tren Idnh thd Viet Nam, cu the Id cho truyen dan vi ba mat ddt. De tu nhung ket qua thu dugc trong khuon khd bdi bdo se Idm lien de cho nhung nghien cuu liep theo ve anh hudng cua khi hdu den truyen ddn vd tuyen tai Viet Nam, ddc biet xet cho lung vung khi hdu dien hinh cda Viet Nam.
Bdi gdm 4 phdn tiep theo nhu sau. Phdn II trinh bdy khdi qudt ve anh hudng cua khi hdu den truyen ddn vd tuyen, dac biet Id suy hao lin hieu vd luyen do mua. Phdn III trinh bdy ve phuong phdp, cdc budc linh todn md phdng suy hao do mua tren Idnh tho Viet Nam. Phdn IV thuc hien phdn tich ket qud dat dugc khi Ihuc hien tinh loan md phdng suy hao do mua tren lanh tho Viet Nam vd phdn V la ket luan cua bdi bao.
109
Pham Thi Minh Nguyet vd dig Tap chi KHOA HOC & CONG NGHE 81(05): 1 0 9 - 1 1 ^
KHAI QUAT VE ANH HUC)NG CUA KHI
H A U DEN TRUYEN DAN VO TUYEN Anh hudng cua khi quyen den truyen tldn vo tuyen
Khi truyin tdi cdc tin hieu vo tuyen qua khi quyin cd rdt nhilu yeu to moi truong dnh hudng ldi chdt lugng tin hieu do thudng hay xdy ra cdc hien tugng phdn xa, tan xa tu tdng dien ly & lang doi luu.
Cdc CO chi quan trgng nhdt cua khi quyen Id khong bi ion hod tdc dgng vd co the gdy bien thien cudng do tin bieu song vo tuyen dien tu (fading) d cac tan so dudi 30 MHz bao gom:
buc xa trong khong gian tu do, su khong dong nhat cua khi quyen, cdc hieu dng khuc xa, phdn xa, tdn xa. Cdc dudng thong tin vi ba khong bi fading nghiem Irgng trong hdu bet cdc dilu kien khi tugng. Tuy nhien, su phan tdng khi quyen vd nhung dieu kien khi tugng khde cd the gdy ra fading nghiem trgng.
Co che tdc dgng cua khi quyen len tin bieu vo tuyen d ddi tdn cao hon 30MHz bao gom: buc xa vdo khong gian tu do, khuc xa, phdn xa tu- cdc lap khi quyen Idng cao, tan xa ve phia trudc lu nhung khu vuc khong dong nhdt cua cdc lap chdt khi, tdn xa va hap thu do cac thanh phdn khi quyen. Cdc dieu kien khi lugng ddng vai tro quan trgng khi xac djnh cudng do vd tinh chdt fading cua truyen sdng thong qua tang doi luu. Suy hao truyen ddn do nhieu xa tang nhanh theo khodng cdch vd dugc coi nhu Id fading do tan xa tdng doi luu.
De tinh todn kha ndng thay doi ede dudng tan xa ve phia trudc trong khodng thdi gian ddi, cdn su dung thong tin ve khi hdu de phdn biet su thay doi ndy giu-a cdc vung dia ly.
0 ddi tan so cao hon 7 GHz, ngodi hieu ung nhieu xa vd da dudng, suy hao vd khu phdn cue do cae chdt khi, bui, nude trong khi quyen cung can dugc quan tam.
0 ddi tdn cao bon 10 GHz, chu yeu xdy ra cac bieu ung lan xa, hap thu do hoi nude, cdc hat dm va oxy. Suy hao ndng lugng tin hieu buc xa do hdp thu trong khi quyen xdy ra tu sir hdp thu sdng vo tuyen do oxy va hoi nude trong khong khi. Cdc hat nude trong khi quyen, md chu yeu Id hat mua gdy ra cd suy
hao Idn tan xa eho song vo tuyen. Vi the viec nghien euu ddnh gid do Ion eua trudng nhieu tilm tang do cdc hat mua tan xa gay ra trong ddi tdn so ndy la rat quan trgng.
6 dai tan so trung binh va cao, phan xa d tang dien ly eho phep truyen dan vo tuyen tren khoang each Idn. Suy hao dang ke nhdl Irong ddi tan nay la suy hao do mua (vdi cdc sdng CO bu'O'c song A, ca vdi cm hoac nho hon) va do tuylt. Vdi cac song co buoe song X co vai mm, suy hao chu yeu Id do suang md, hoi nude vd cae chat khi khde trong khi quyen.
Anh huong eua may, cat vd bui mac dd it ro ret hon, song tuy thuge vdo tinh chdt cda cac vung khi hdu dang quan tam ma cung can phdi xem xet den. Tuyet va mua da chua hdn hgp cua tinh the da vd nuoe eung gdy suy hao tin hieu vo luyen. Suy hao cua ddi vi sdng trong tuyet kho nho hon mot bae so vdi suy hao trong mua eung toe do. Suy hao do tuyet udt CO thi xap xi suy hao do mua vd tham chi eo the eao ban suy hao d ddi sdng mm [2].
Nhu vay, doi vdi truyen dan vo tuyen, cau true ede ehdt khi trong khi quyen va ddc biet Id eae yeu to khi hdu nhu nhiet do, mua, suong mu, tuyet... anh huong rat Idn den chat lugng tin hieu. Vdi cdc vung eo che do khi hdu nhiet ddi ddc thu nhu Viet Nam thi suy hao do mua dnh hudng rat lon den moi trudng truyen ddn vo tuyen.
Ca sd ly thuyet tinh suy hao tin hieu tlo mua Suy hao tin hieu vo tuyen do mua d lan so khodng 7 GHz thudng eao hon su hap thu to hgp do oxy, hoi nuac. Suy hao ndy ndy sinh tu sir hap thu nang lugng eua cac gigt nude va tu tan xa ndng lugng cua ehung khdi chum anten. Hap thu vd tan xa do mua phu thugc chu yeu vdo hinh dang, kich thuac, hang so dien moi eua cdc hat mua, su phdn cue va budc song dien tu. Viee xdc djnh suy hao do mua Id rdt phuc tap vi tren thue te truong mua thuong khong dong nhdt vd c6 do bien dgng rat lon. Mua thay doi ddng ke ve mat do, kich thuoc vd hinh dang cua hat mua. Trong bat ky dang mua nao deu co kich thudc hat khong dong deu, thay doi theo thai gian vd khdng gian. Cdc gigt mua nho dnh hudng rat Idn den buac sdng milimet, lac dgng manh me den muc do suy hao ndng lugng song dien tu.
Pham Thi Minh Nguyet vd dig Tap chi KHOA HOC & CONG NGHE 81(05): 109- 114 Suy hao ndng lugng song dien tu thudng
dugc bieu thj bang mot hdm cda lugng mua R bao gdm ca lugng nude, toe do roi vd kich thudc cua cdc gigt mua. Tong do suy hao A,.
do lugng mua tren quang dudng ddi r,, co the xac dinh dugc boi lich phdn he so hap thu do mua yfrj dgc theo dudng tdm nhin thang giua hai anten [3]:
A, = \yA>')dr dB (1)
0
Ddi vdi dp dung thue te, quan be gida he so suy hao yr(dB/km) vd lugng mua R (mm/h) d ddi tan sd dd cho ed the dugc xdp xi theo djnh luat hdm mu [6]:
Yr=k.R° (dB/km) (2)
Trong dd, tham sd k vd a dugc tinh tren ddi tan rdng vdi dang mua cd nhiet do vd phdn bd kich thudc gigt khac nhau. Tren thuc te sd lieu lugng mua trong mot vung, dugc cdc co quan khi tugng cung cdp, khong cd du cdc dac trung thong ke cdn thiet cho cdc phep linh suy hao. Ddi vdi cdc linh todn muc do suy hao tren dudng truyen tin hieu trong khi quyen yeu cdu thong tin mua phdc lap hon, dd Id can phdi biet do cao md mua bdt ddu roi.
Cac he sd a va k phu thugc tdn sd dugc dua ra trong bang 1 [6]. Cdc be sd ndy Id cho phdn cue tuyen tinb (dung-V vd ngang-H) vd cac dudng truyen ngang.
Ddi vdi phdn cue trdn, k vd a dugc tinh tu cac gid Irj trong bdng 1 su dung cdc phuong trinh sau[6];
k = [k„+k,]l2 (3) a = [k^a„+k,a,]l2k (4) Bang 1. Cac he sd phu thugc tan sd phuc vu tinh suy hao do mua khi sd dung phuonti trinh (2), (3)
va (4) [6]
Frequency
(GHz) a-H ky a,-
Frequency (GHz)
10 11 12 13 14 15
k„
0.01217 0.01772 0.02386 0.03041 0.03738 0.04481
Ct-H
1.2571 1.2140 1.1825 1.1586 1.1396 1.1233
A,
0.01129 0.01731 0.02455 0.03266 0.04126 0.05008
a.
1.2156 1.1617 I.I2I6 1.0901 1.0646 1.0440
16 0.05282 1.1086 0.05899 1.0273 17 0.06146 1.0949 0.06797 1.0137 18 0.07078 1.0818 0.07708 1.0025 19 0.08084 1.0691 0.08642 0.9930 20 0.09164 1.0568 0.09611 0.9847 TINH T O A N M O PHONG SUY HAO DO MUA TREN L A N H THO VIET NAM
1. Nhu chung ta da biet lanh thd Viet Nam nam trong khu vuc Dong Nam chau A cd che do khi hdu nbiel ddi gid mua khd dac trung - ndng, dm vd mua nhieu. Ldnh thd Viet Nam nam trgn trong vung ngi chi luyen bac, cd che do birc xa mat trdi ddi ddo nen nen nhiet do trung binh nam khd cao. Lugng mua tren hau bet cdc vung khi hdu deu cao. song phdn bd khong deu trong nam. Khoang 85% lugng mua tap trung trong mua intra vd chi cd khoang 15% trong cdc thdng mua kho. Viet Nam ndm trong khu vuc cd bao vdo loai nhieu vd hoat dgng manh nhdt the gidi [1].
Bao gdy ra nhung dgt mua vdi cudng do Idn va keo ddi trong nhieu ngdy gdy nen tinh trang ngap lut nghiem trgng Idm dnh hudng den mgi boat dgng kinh le - xd hdi, trong dd cd ngdnh truyen thdng.
Viec ddnh gid tdc dgng cua bien tugng mua den truyen ddn vd luyen d Viet Nam Id het sue cdn thiet ddi vdi cong nghe vd tuyen. Vi vay, trong bdi ndy chung tdi lira chgn thuc hien viec tinh loan md phdng suy hao tin hieu vd tuyen do intra diia tren sd lieu Ibdng ke ddi ban ve lugng mua tren lanh thd Viet Nam.
2. Hien nay d Viet Nam, de truyen tdi sdng vd luyen trong khodng each lu 2-10km, he thdng vi ba mat ddt dang sir dung ddi tan 14, 15 GHz. Tuy vay, thuc te cho thay cac dai tdn so ndy dang trd nen qud tdi. Vi le dd, Bg thong lin & truyen thdng Viet Nam len quy hoach su dung ddi tdn so 17 GHz. De phuc vu cho muc dich neu tren, trong cong trinh ndy chdng tdi lira chgn linh loan md phdng suy hao do mua tren ddi tdn so 17 GHz.
3. Viec tinb todn do suy hao tin hieu vd tuyen do mua theo cdc ddc trung thdng ke dai ban duoe thuc hien theo cdc budc:
11
Pham Thi Minh Nguyet vd dig Tap chi KHOA HOC & CONG NGHE 81(05): 109-114 Bitdc 1: Thu thap cuong do mua (RQOI) eo ti
phdn thdi gian cao hon 0,0 l%o cua nam trung binh (buoe linh bdng mot phut). So lieu ve cuong do mua trong cong trinh ndy duge tinh toan, trich xuat tu tap so lieu tdi phdn tich ve lugng mua cua Trung tdm du bao thdi tiet han vua Chdu Au (ECMWF) - ERA 40, tuong tu nhu Khuyin cdo ITU-R P.837-5 [4]. Theo do Ihi vin^. Jdnln tho Viet Nam co cuong do mua (Rooi"* vdi ty phdn thdi gian cao hon 0,01%) ndm trung binh la 90mm/h.
Budc 2: Xdc dinh cdc he so k vd a cho cdc kieu phdn cue ngang, ddrng vd trdn.
Doi vdi tan so 17 GHz, theo cong thuc (3), (4) vd bdng 1, cdc gid In k vd a cho cdc trudng hgp phdn cue ngang, dung vd Iron dugc tinh vd trinh bay Irong bdng 2 sau:
Bang 2. Gia tri cac he sd k va a ddi vdi dai 17 GHz cho phan cue ngang, dung va trdn
Kieu phan cue k ct Ngang
Ddng Trdn
0,06146 0,06797 0,064715
1,0949 1,0137 1,0526 Budc 3: Tinh do suy hao, y^ (dB/km), cho cdc ddi tan so, kieu phdn cue vd cudng do mua da tinh d budc 1 lbeo cong thue (2).
Bitdc 4: Tinh chieu ddi dudng truyen sdng hieu qud, d^,ff, bdng cdch nhdn chieu ddi dudng ddn thuc le d vdi he so khoang cdch r.
Vdi: 1 (5) r = -d I dr,
Trong do:
KhiRooi < 100inin/h:do = 35e -0.015 7?, 0.01 ( 6 )
Khi RQOI > lOOmm/h: su dung gid tri RQOI = lOOmm/h.
Budc 5: Tinh long suy hao do mua, Ar, tren qudng dudng voi cuong do mua ed li phdn thai gian cao ban 0,01%) cua ndm trung binh:
^0.01 = Y« detf = y« dr (dB) (7) PHAN TICH KET QUA
Viec tinh todn mo phong suy hao do mua, khoang cdch dudng hieu qua (deff) a tdn so
1 7 G H Z dugc thuc hien bang phan mim Matlab. Ket qud tinh todn mo phdng dugc dua ra dudi dang bai do tbi:
Do thi dau tien bieu thj do suy hao tin hieu vo tuyin (dB/km) tuong irng voi cudng do mua (mm/h). Suy hao dugc mo phong trong khoang gia trj cuong do mua tir 0-150 mm/h. Mua phun CO toe do 0,25 mm/h, mua nhe la Imm/h, mua nang hat la 25 mm/h va mua to len den
150 mm/h. Ba duong khde nhau tren dd thj ddu dai dien cho mu'c do suy hao khde nhau cda ba kieu phan cue ngang, dung va tron.
Do thj thu hai Id long suy hao (dB) luong img vdi khoang each duong truyen (km). Dd thj thir hai cung eho thay muc do suy hao khac nhau eua ba kieu phan cue. Muc dich chinh cua do thi ndy la xdc dinh chieu ddi quang dudng toi da c6 the dat duge. Vi du, hinh 2 cho thay miJC suy hao theo cuong do mua 90 mm/h doi vdi timg khodng cdch dudng cu the.
Tir do thj thay rdng, mue suy hao 15 dB tuong dng vdi khoang cdch khoang 3 km, 20 dB tuong ung voi khoang each khoang 4,7 km. Vi vdy, doi vdi dudng eong ed suy hao 15 dB (phdn cue dung), do ddi chuang dudng dat dugc la 3 km vd dat 4,7 km doi vdi dudng eong CO suy hao 20 dB.
Suy hao do tnua tai lan so 17GHz
Phan cue ngang Phan cue dung Phan cue Iron
Luong mua. (mm/hr)
Hinh 1. Suy hao tin hieu vd tuyen do mua lai tan sd 17GHz
Suy hao voi luong mua 90 m m / h
: ^^^:,^^>^.-: .
• > . > • • - "
/'vT /y.'
. V-
' 1
Phan cue dung Phan cue Iron Phan cue ngang
,
•
Khoang c a c h . (km)
Hinh 2. Suy hao tin hieu vd luyen theo khoang each dudng vdi cudng do mua Rooi = 90mm/h
Pham Thi Minh Nguyet vd dtg Tap chi KHOA HOC & CONG NGHE 81(05): 109- 114 Khi thay lan lugt cae gia trj khoang each
dudng truyen giira hai tram vi ba mat ddl ldm nhin thdng (lu 2 den 10 km) thi chdng tdi thu dugc cac ket qua nhu bang 3 & 4 sau:
Bang 3. Tdng suy hao (dB) theo khoang each (2-5km) vdi ba kieu phan cue
Phan cue 2km 3 km 4km 5km Dung 13,0126 14.6688 18.0624 20.9737
Tron 14,7368 16.6125 20.4557 23.7527 Ngang 16,956 19.1141 23.5361 27.3296 Bang 4 Tong suy hao (dB) theo khoang each (6-
lOkm) vdi ba kieu phan cue
' ' ^ ^ " 6km 7km 8km 9km 10km cue
Dung 23.4987 25.7095 27.6613 29.3972 30.951 Tron 26.6123 29.1161 31.3265 33.2924 35.0521 Ngang 30.6198 33.5006 36.044 38.3059 40.3306 Qua phdn tich cho thdy phdn cue ngang bi suy hao nhieu nhdt (Hinh 1), phdn cue dung bj suy hao it nhdl, trong khi phdn cue Iron cd mdc suy hao trung binh giua hai kieu phdn cue ngang va phan cue dung.
Ngodi ra, vdi cudng do mua Rooi = 90mm/h, chdng tdi thuc hien tinh them tren quang dudng 10 km vdi cdc tdn sd 10, 12 & 15GHz vd thu dugc kel qud nhu bdng 5:
Bang 5. Tdng suy hao (dB) tren 10km tai cac tan sd khac nhau vdi ba kieu phan cue Kieu
phan cue lOGHz 12GHz 15GHz l7GHz Dung 12.4574 17.6906 25.5136 30.951
Tron 13.7097 19.5163 28.4183 35.0521 Ngang 14.9719 21.3704 31.4198 40.3306 Tu bang 5 cho thay, cdng khodng each dudng truyen vd cung kieu phan cue, nhung tan sd cang cao thi tdng suy hao cdng Idn.
Ddi vdi khodng cdch dudng truyen bieu qud (deff), do ddi quang dudng tuong dng vdi cudng do mua 90mm/h tai tan sd 17GHz, chdng tdi thu dugc kel qua nhu bdng 6. Tu bang 6 cho thdy, den (km) bi ban che khi khodng cdch dudng truyen ddi. Phuong an nay chi thich hgp cho he thdng tam nhin thang khodng cdch ngdn. Dieu ndy ddng nghTa vdi viec ban che tinh linh boat cda he thdng
LOS khi lam viec d khodng each dudng truyen ddi, ddi tan cao.
Bang 6: Khoang each dudng truyen hieu qua (decr) theo do dai quang dudng
Do dai quang dudng (km) deff (km) 4
5 6 7 8 9 10
2,2546 2,7761 3,2236 3,6117 3,9515 4,2515 4,5183 4,7571 KET LUAN
Cdc dieu kien khi hau dnh hudng rat Idn den chat lugng truyen ddn thdng tin vd luyen, ddc biet Id mua nen phdi nghien ciru xu ly tren co' sd su dung so lieu thong ke ddi ban cho tirng vdng khi hdu dien hinh cda Viet Nam.
Che do khi hdu d Viet Nam, ddc biet la che do mua cd tinh ddc thu rdt cao. Mua phan bd khdng deu trong ndm vd giua cdc khu vuc khac nhau tren lanh thd. Ket qud tinh todn do suy hao do mua d Viet Nam cho thdy, vdi cudng do mua 90inm/h, he thdng truyen thdng vi ba mat ddt 17 GHz Id thich hgp nhdt vdi khodng cdch dudng truyen ngdn va theo kieu phdn cue dung.
Cdc ket qud neu tren cho thdy, neu tdi nguyen tdn sd d nhirng ddi tan thdp dd bet, khi mudn md rdng ra nhirng ddi tdn Idn ban trong thiet ke cdc tuyen truyen ddn vi ba trong tuong lai cdn phdi tham khdo kel qud tinh todn tdng muc suy hao do dieu kien khi hdu, dac biet Id do mua nhu da trinh bdy tren ddy de tu dd de ra cdc bien phdp tdng cong sudt phdt tin hieu nhdm dat dugc bieu qud tdi uu.
TAI LIEU T H A M K H A O
[l].Nguyen Due NgQ- (chu bien). Blin ddl khi hdu, Nxb Khoa hgc Ky thuat, 2008.
[2].Donald G.Fink-Donald Christiansen, Sd tay ky Slf dien tit, Nxb Khoa hoc-Ky thuat, 2000.
[3].Robert E.Collin, ''Antennas and Radiowave Propagation", McGraw-Hill Book Company, 1985 [4]. "Characteristic of precipitation for propagation modelling", Rec ITU-R p837-5, 2007.
113
Pham Thi Minh Nguyet vd dig Tap chi KHOA HOC & CONG NGHE 81(05): 109-114
[5]. Propagation data and prediction methods required for the design of terrestrial llne-of-slght system, Rec ITU-R p530-12, 2007.
[6]. Specific attenuation model for rain for use In prediction methods, Rec ITU-R p838-3, 2005.
[7].Dusan Cermak, Ondrej Fiser, Vladimir Schejbal, Electromagnetic scattering by rain drop, Dusan Cermak, Ondrej Fiser, Vladimir Schejbal June, 2005.
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S U M M A R Y
T H E E F F E C T S O F T H E A T M O S P H E R E O N W I R E L E S S C O M M U N I C A T I O N IN C L I M A T E C O N D I T I O N S O F V I E T N A M
! :i-t
Pham Thi Minh Nguyet'*, Tran Anh Thang^ Nguyen Dang Que^
'College of Electronics - Refrigeration Hanoi' Thai Nguyen University ofTechnology - TNU 'institute of Hydrometeorology and Environment - Ministry of Natural Resources and Environment
The climatic factors such as temperature, rain, fog, snow... affect strongly to the quality of the wireless transmission. Global warming effects of artificial greenhouse gases increase as a giant energy source to supplement the earth's surface, is certain to impact on the structure of the atmosphere (the main transmission medium of electromagnetic radio waves). This article discussed about the influence of climate on radio transmissions, especially influence of rain - one of main factors of a tropical monsoon climate in Vietnam. In this article, some results of initial simulation of the attenuation by rain, which made some comments for the design of line-of-sight (LOS) terrestrial system lines in accordance with typically climatic conditions in Vietnam.
Keywords: Tropical climate, climate change, radio transmission, attenuation due to rain, microwave transmission.
