^F^ Cong nghe-Giai phap<br />
1^1^"<br />
TONG QUAN VE KY T H U A T<br />
DA ANTEN<br />
TS. Nguyen Thjnh<br />
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Da anten la ten chung cho tap hop nhung ky thuat dUa tren viec<br />
siirciLing nhieu anten a phia thu/phia phat, va it nhieu ket hop v6i<br />
ky thuat xur ly tin hieu, thu'dng du'dc goi la MliVIO. Ky thuat da<br />
anten co the dUcJc su" dung de nang cao hieu nang he thong, bao<br />
gom lam tang dung lu'dng he thong (so ngu'di dung trong mot 6<br />
tang) va tang vCing phu (md rong 6) cung nhU la lam tang kha<br />
nang cung cap djch vu, vi du toe do dOr lieu ngu'di dung cao hdn.<br />
Bai viet so cung cap cai nhin tong quan nhat ve ky thuat nay.<br />
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1. CAU HINH DA ANTEN khoang each anten vao khoang 10 bUdc sdng<br />
Mdt trong nhifng dac tinh quan trpng thi mdi dam bao dp tUdng quan tha'p, trong<br />
trong cau hinh da anten la khoang each giCfa khi dd thi khoang each anten cho may dau<br />
hai phan tuf anten do khoang each cac anten cudi di ddng khoang nufa budc sdng. Ly do<br />
cd mdi quan he vdi dp tUdng quan giilci fading khac nhau giufa tram gdc vdi may dau cudi di<br />
kenh vd tuye'n (dUpc xac dinh bdi tin hieu tai ddng la do trong kich ban macro, phan xa da<br />
cac anten khac nhau). Cac anten dUdc dat xa dudng gay ra fading chu ye'u xuat hien d<br />
nhau de dp tUdng quan fading thap. NgUdc nhufng viing gan xung quanh may dau cudi di<br />
lai, cac anten dUdc dat gan nhau de dp tUdng ddng. Do do, khi nhin tif vi tri may dau cudi<br />
quan fading cao, ban chat la cac anten khac thi ta thay la nhOfng dudng khac nhau di de'n<br />
nhau se cd fading tufc thdi tUdng tuf nhau. trong mdt gdc Idn, dp tUdng quan vin se thap<br />
vdi khoang each anten tUdng ufng nho. Cdn<br />
nhin d vi tri tram gdc, nhting dUdng khac<br />
Khoang each thufc te can thie't giufa cac nhau se den trong mdt gdc nhd hon nhieu,<br />
anten de dp tUOng quan cao/thap phu thudc nen khoang each anten phai du Idn de dp<br />
vao budc sdng, tUOng ufng la tan so sdng tuong quan thap.<br />
mang dupc suf dung. Tuy nhien, nd cung phu<br />
thudc vao kich ban khi trien khai. TrUdng hpp<br />
cac anten tram gdc, mdi trUdng macro-cell Trong kich ban trien khai khac, vi du<br />
(tufc la d Id'n va vi tri anten tram gdc phai cao). trien khai kich ban micro-cell vdi cac anten<br />
tram gdc tha'p hon ndc nha va trien khai trong<br />
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TH S TIN KHKT & KINH TE BUU DIEN so 1/2010 43<br />
TR Cong nghe-Giai phap<br />
^ ^<br />
nha. Mdi trUdng tram gd'c luc nay gidng vdi Md hinh kenh MIMO tdng quat gdm Nf anten<br />
mdi trUdng may dau cud'i han, cho nen phat va N^ anten thu dUdc minh hpa trong<br />
khoang each giiJa cac anten tram gd'c se nhd<br />
hinh 1,<br />
hdn van dam bao dp tUdng quan thap.<br />
h.<br />
<br />
Cac anten gia thiet d tren cd ciing<br />
phan cufc. Mot each khac de dat dufdc dp<br />
tUdng quan fading thap la ap dung phan cUc<br />
khac nhau ddi vdi anten khac nhau. Khi do<br />
cac anten cd the dUdc drt gan nhau.<br />
2. LOI ICH CUA KY THUAT DA ANTEN<br />
Ky thuat da anten mang lai nhiSng Ipi<br />
ich khac nhau phu thudc vao nhufng muc dich<br />
khac nhau:<br />
<br />
Nhieu anten phat/thu cd the dUdc suf Hinh 1. Md hinh kenh MIMO vdi Nt anten<br />
dung de phan tap, chdng lai fading kenh vd phdt vd Nr anten thu<br />
tuye'n. Trong trUdng hpp nay, kenh khac nhau Trong dd:<br />
tren cac anten khac nhau se cd dp tUOng quan - hnm la dp Ipi kenh giufa anten phat thuf n va<br />
tha'p. De dat dupc dieu dd thi khoang each - anten thu thuf m.<br />
giiia cac anten phai du Idn (phan tap khdng - X la so lieu phat.<br />
gian) hoac suf dung cac anten cd phan cUc - y la so lieu thu.<br />
khac nhau (phan tap phan cUc). 4. LTNG DUNG MIMO TRONG HSPA vA<br />
LTE<br />
Nhieu anten phat/thu cd the dUdc suf<br />
dung de 'dinh binh' cho bup sdng anten td'ng Ung dung ky thuat da anten trong<br />
(bup sdng phia phat va bup sdng phia thu) HSPA+<br />
theo mdt each nao dd. Vi du, tdi da hda dp ldi Qua trinh tich hdp cdng nghe MIMO<br />
anten theo mdt hUdng thu/phat nhat dinh trong HSPA phai mat mot thdi gian kha lau.<br />
hoac de triet nhilu lan at tin hieu. Ky thuat Cd rat nhieu phUdng an dUdc danh gia va<br />
tao bup sdng nay cd the dua tren ca dp tUdng thufc hien. Ke't qua cud'i cuing la quye't dinh md<br />
quan cao hoac thap giite cac anten.<br />
rong sP do phan tap phat vdng kin cua<br />
WCDMA R99 bao gom ca ghep kenh khdng<br />
Dp kha dung cua da anten phat va thu gian. PhUdng phap nay dupc gpi la D-TxAA<br />
cd the dugc suf dung de tao ra nhieu kenh (Double Transmit Antenna Array) . Nd chi ap<br />
truyen song song thdng qua giao dien vd dung dugc cho kenh chia se dudng xud'ng tdc<br />
tuye'n. Dieu nay mang lai kha nang tan dung dp cao HS- DSCH.<br />
bang thdng ma khdng can giam thdng tin vdi<br />
ciing cdng suat. Ndi each khac la kha nang Tmyen dan tren hai ludng trd len dUpc<br />
cho tdc dp diJ lieu cao vdi bang tan ban che hd trd bdi HSDPA-MIMO. HSDPA- MIMO la<br />
ma khdng can thu hep vung phu. Ta gpi day mdt sd do nhieu tif ma va cho phep may thu<br />
la ky thuat ghep kenh khdng gian. triet nhilu thanh cdng d phia thie't bi ngUdi<br />
diing. Mdi ludng se dUdc xuf ly tai tang vat ly<br />
3. M(!) HINH MIMO TONG QUAT gidng nhau: ma hda, trai phd va dieu che<br />
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44 so 1/2010 THONG TIN KHKT & KINH TE BUU DIEN<br />
^<br />
Cong nghe-Giai phap<br />
t^I^<br />
gidng nhu trong trUdng hpp 1 ISDPA.<br />
Sau khi ma hda, trai phd va dieu che, Tuma Ngau lap Sap \ep laonn<br />
^ pliatirir<br />
tien ma hda tuyen tinh se dUdc thufc nhien hoa<br />
Dit'U che<br />
tai nguyen Y<br />
hieu<br />
OKDM<br />
hien trUdc khi sap xep tdi 2 anten Sap Tieti<br />
xep ldp inahua<br />
phat. Tien ma hda mang lai nhieu Ipi<br />
ich khdng chi vdi truyen da luong ma<br />
r<br />
Sap xep Tao (in<br />
Ni;au<br />
Dieu che phan cu hieu<br />
ngay ca vdi truyen din mdt ludng khi<br />
suf dung phan tap phat. Do vay, tien<br />
nhien ho2<br />
' lai nguyen r<br />
OFDM<br />
<br />
<br />
<br />
ma hda trong truyen din ddn ludng<br />
Hinh 2. Sa do tdng quat tao tin hieu bang goc<br />
cung gidng nhu phan tap phat che<br />
dudng xudng.<br />
dp vdng kin (suf khac nhau chu ye'u d<br />
bao hieu va tdc dp cap nhat). Ve cd<br />
4. Ndi each khac, la trong trudng hpp ghep<br />
ban, cd the coi day la mdt kieu tao bup don<br />
kenh, thi so ludng ghep Idn nhat dUdc quy<br />
gian. Ngoai ra, tien ma hda cdn dupc suf duing<br />
dinh la 2.<br />
de lam cho hai luong tin hieu gan nhu trufc<br />
Viec xii ly kenh bao gom viec sap xep<br />
giao tai phia thu. Nd se lam giam nhilu giiia<br />
anten, tufc la xuf ly cac khdi ky hieu dieu che tuf<br />
hai luong tin hieu cung nhu lam giam viec xuf<br />
hai khdi da ma hda va sau dd sap xep len cac<br />
ly tin hieu so d phia thu.<br />
anten phat. Viec sap xep anten LTE bao gom<br />
Ung dung ky thuat da anten trong LTE hai budc la Sap xep theo ldp va Tien ma<br />
hda.<br />
Ngay tuf dau, LTE hd trd da anten d ca<br />
tram gd'c va may dau cud'i di ddng nhU mot Viec chia thanh hai chufc nang tach<br />
thanh phan khdng the thieu. Trong nhieu biet nhu tren de cd the dl dang xac dinh va<br />
khia canh, viec suf dung ky thuat da anten rat bieu diln cac sd do da anten khac nhau, bao<br />
quan trpng de dat dUdc bieu nang LTE. Da gom phan tap phat vdng hd, tao bup sdng va<br />
anten cd the dUdc suf dung trong nhieu each ghep kenh khdng gian trong mdt co cau da<br />
khac nhau vdi muc dich khac nhau. anten. Dang sau nhufng vi du ve sd do truyen<br />
dan da anten la dufa ra viec thUc bien chung<br />
Sd do MIMO dudng len cho LTE khac<br />
trong cd cau da anten LTE.<br />
vdi so do dudng xud'ng vi ban che ve dp phufc<br />
tap may dau cud'i. Vdi dUdng len, MU-MIMO<br />
5. KET LUAN:<br />
(Multi user MIMO) cd the dPdc suf dung. Nhieu<br />
ngUcrt suf dung phat tin hieu tren ciing khdi tai<br />
nguyen. Nd cdn dUdc gpi la SDMA. Sddd nay Nhung nam gan day cac he thdng da anten<br />
yeu cau chi cd mdt anten phat d phia UE (user MIMO da trd thanh cac chu de thu hut nhieu<br />
equipment). Nhifng UE ciing chia se mdt khdi td chufc nghien cufu tren toan cau. He thd'ng<br />
tai nguyen se phai ap dung cac mau hoa tieu MIMO rat cd trien vpng trong cac he thd'ng<br />
trufc giao. O day gidi thieu ky thuat da anten thdng tin di ddng the' he sau bdi le nd khdng<br />
tren dUdng xud'ng cua LTE. cbi cho phep dat dUdc hieu qua suf dung phd<br />
tan cao hdn nufa ma cdn cd tinh kha thi ve<br />
phan cufng cung nhU phan mem. Tuy nhien<br />
Hinh 2 trinh bay sd lUdc ve cac bUdc MIMO lai la mot van de phdc tap vdi nhieu ky<br />
trong qua trinh tao tin hieu bang gd'c dudng thuat rac rdi, do do can tie'p tuc cd nhieu<br />
xud'ng LTE bao gdm cac bUdc truyen din nghien cufu hOn nufa ve van de nay.Q<br />
MIMO.<br />
Dd'i vdi dudng xud'ng LTE, so tif ma<br />
Idn nhat bang hai, so anten phat Idn nhat la<br />
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THONG TIN KHKT & KINH TE BUU DIEN S O I /2010 45<br />