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cc lung d liu tc thp hn v pht
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Nguyn l c bn ca OFDM l chia 1 lung d liu tc cao thnh cc lung
d
liu tc thp hn v pht ng thi trn 1 cc sng mang con trc giao. V
khong thi gian symbol tng ln cho cc sng mang con song song tc
thp
hn, cho nn lng nhiu gy ra do tri tr a ng c gim xung. Nhiuxuyn k
t ISI c hn ch hu nh hon ton do vic a vo 1 khong thi
gian bo v trong mi symboy OFDM. Trong khong thi gian bo v,
mi
symboy OFDN c bo v theo chu k trnh nhiu gia cc sng mang ICI
Kin trc LTE:
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7/30/2019 Nguyn l c bn ca OFDM l chia 1 lung d liu tc cao thnh
cc lung d liu tc thp hn v pht
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Cc mc tiu ca cng ngh ny l:
- Tc nh tc thi vi bng thng 20 MHz:
Ti xung: 100 Mbps; Ti ln: 50 Mbps
- Dung lng d liu truyn ti trung bnh ca mt ngi dng trn 1
MHz so vi mng HSDPA Rel. 6:
Ti xung: gp 3 n 4 ln; Ti ln: gp 2 n 3 ln.
- Hot ng ti u vi tc di chuyn ca thu bao l 0 15 km/h. Vn
hot ng tt vi tc t 15 120 km/h. Vn duy tr c hot ng khi
thu bao di chuyn vi tc t 120 350 km/h (thm ch 500 km/h ty
bng tn)
- Cc ch tiu trn phi m bo trong bn knh vng ph sng 5km, gim
cht t trong phm vi n 30km. T 30 100 km th khng hn ch.
- di bng thng linh hot: c th hot ng vi cc bng 1.25 MHz, 1.6 MHz,
2.5MHz, 5 MHz, 10 MHz, 15 MHz v 20 MHz c chiu ln v xung.
H tr c 2 trng hp di bng ln v bng xung bng nhau hoc khng.
t c mc tiu ny, s c rt nhiu k thut mi c p dng, trong
ni bt l k thut v tuyn OFDMA (a truy cp phn chia theo tn s trc
giao), kthut anten MIMO (Multiple Input Multiple Output - a nhp a
xut).
Ngoi ra h thng ny s chy hon ton trn nn IP (all-IP network), v h
tr c
2 ch FDD v TDD
Cu trc mng 4G LTE
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7/30/2019 Nguyn l c bn ca OFDM l chia 1 lung d liu tc cao thnh
cc lung d liu tc thp hn v pht
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S chuyn i cu trc mng t UTRAN sang E- UTRAN
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cc lung d liu tc thp hn v pht
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Mng li (EPC): p ng cho vic iu khin UE v thit lp cc thng bo
Mng truy cp(E- UTRAN) : l mt mng li cc eNodeB
So snh OFDM vi SG-OFDM
Truyn d liu hng xung
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7/30/2019 Nguyn l c bn ca OFDM l chia 1 lung d liu tc cao thnh
cc lung d liu tc thp hn v pht
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S dng k thut OFDM cho hng xung.
u im
S dng c hiu qu bng thng
OFDM cho php truyn dn tc cao trong mi trng di
ng
Chu k k t tng ln v vy nhy cm ca h thng vi tri
rng tr gim xung.
Nhc im
Tn hiu OFDM b nh hng bi mo phi tuyn ca b khuch
i cng sut pha pht
OFDM nhy cm vi dch tn s sng mang
Truyn d liu hng ln
S dng k thut SC- FDMA
u im
S dng SC-FDMA, cho PAPR nh hn nn tiu th cng sut t hn u cui di
ng, do vy tit kim pin cho thit b u cui.
S dng SC-FDMA t nhy cm vi hiu ng Doppler nn tng tnh di
ng cho thit b u cui.
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7/30/2019 Nguyn l c bn ca OFDM l chia 1 lung d liu tc cao thnh
cc lung d liu tc thp hn v pht
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Nhc im
bng thng thp hn so vi OFDM nhng c ci thin nh s dng k
thut MIMO
Cc k thut truy nhp v tuyn trong LTE
K thut OFDM : l kiu truyn dn a sng mang vi cc c
im sau
S dng nhiu sng mang, cng bng thng l 20MHz
nhng MC- WCDMA s dng 4 sng mang cn OFDM s
dng 2048 sng mang
Cc sng mang con trc giao vi nhau
Khong cch gia cc sng mang con
-Khong cch gia cc sng mang con cn nh cng tt
- Khong cch gia cc sng mang con qu nh s tng s
nhy cm ca truyn dn OFDM vi tri Doppler
S lng sng mang con
- c xc nh da trn bng thng kh dng v pht x
ngoi bng
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cc lung d liu tc thp hn v pht
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S dng OFDM cho ghp knh v a truy
nhp
-Trn ng xung OFDM s dng lm s ghp knhcho nhng ngi s dng
-Tr n ng ln OFDM c s dng lm s a truy
nhp
S iu ch tn hiu OFDM trm pht v thu
OFDMA
- Cho php cc nhm nh ca sng mang con c cp pht
dao ng gia nhng ngi dng khc nhau trn cng bng tn
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cc lung d liu tc thp hn v pht
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- Vn a truy cp c thc hin bng cchcung cp cho
mi ngi dng mt phn trong s cc sng mang c sn
K thut SC-FDMA : l k thut a truy cp phn tn mt knh
truyn duy nht, c s dng v c tn hiu PARP tt hn
OFDMA
-Truyn d liu qua giao tip v tuyn trong nhiu knh con
- So vi OFDM t cc bit vi nhau to thnh tn hiu cho
mt knh con th SC-FDMA tri thng tin ca mi bt trn tt
c cc knh con
Tn hiu SC-FDMA c to ra bng k thut tri ph DFT-s-OFDM
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7/30/2019 Nguyn l c bn ca OFDM l chia 1 lung d liu tc cao thnh
cc lung d liu tc thp hn v pht
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