HC VIN CNG NGH BU CHNH VIN THNG

---------------------------------------

TRN I NGHA

NGHIN CU GII PHP RELAY TRONG MNG LTE Chuyn ngnh : K Thut Vin Thng

M S : 60.52.02.08

TM TT LUN VN THC S

H NI - 2013

Lun vn c hon thnh ti :

HC VIN BU CHNH VIN THNG

Ngi hng dn khoa hc :TS. V TRNG THNH

Phn bin 1:

Phn bin 2 :

.

Lun vn c bo v trc Hi ng chm lun vn Thc s ti Hc Vin Cng Ngh

Bu Chnh Vin Thng.

Vo lc :..Gi..ngythng.nm 2013

C th tm hiu lun vn ti :

-Th vin ca Hc Vin Cng Ngh Bu Chnh Vin Thng.

M U

Thng tin di ng ngy nay tr thnh mt lnh vc pht trin rt nhanh v mang

li nhiu li nhun cho cc nh khai thc. S pht trin ca th trng vin thng di

ng thc y mnh m s nghin cu v pht trin cc h thng thng tin di ng

mi trong tng lai.

Mc d cc h thng thng tin di ng 3G vn ang pht trin khng ngng nhng

cc nh khai thc vin thng ln trn th gii tin hnh trin khai th nghim v

chun ha chun di ng 4G. Cng ngh 4G mang li nhng tin ch vt tri cho

ngi dng mi lc, mi ni k c khi ang di chuyn vi tc cao. chnh l im

khc bit gia mng di ng th h th ba (3G) v mng di ng th h th t (4G).

Nhm mc tiu cung cp dch v truyn dn d liu tc cao cho cc thu bao di

ng sau 3G, 3GPP nghin cu a ra cng ngh di ng LTE bt u t 3GPP

Release 8. LTE l mt chun cho cng ngh truyn thng d liu khng dy v l mt

s tin ha ca cc chun GSM/UMTS.

ti Gii php Relay trong mng LTE c la chn nghin cu v

trin khai trong mng LTE.Vi khun kh hn hp vi thi gian v trnh hc vn.

Mc ch chnh ca ti a ra hot ng c bn ca h thng mng LTE, tm hiu

cc cng ngh di ng mi tin tin, cc gii php ci thin v cht lng dch v

m bo p ng ngy cng cao nhu cu ca ngi s dng.

Ni dung lun vn gm 3 chng:

Chng 1: Tng Quan Mng Di Dng LTE.

Chng 2: Gii Thiu Cng Ngh Mng Relay LTE.

Chng 3: Nghin Cu Hot ng Ca Relay Trong Mng LTE

Kt lun: Tm tt kt qu nghin cu, cc xut, kin ngh

CHNG 1

TNG QUAN MNG DI NG LTE

1.1 Gii Thiu Chng.

p ng nhu cu ca ngi s dng ngy cng cao v cc dch v truy nhp d

liu, m thanh, hnh nh vi tc cao bng rng mi ni, mi lc, mi dch v, mi

thi im mng di ng th h th t 4G (Fourth Generation) c xut

nghin cu v trin khai trn th gii. Trong chng ny trnh by tng quan v mng

di ng LTE, tiu chun cht lng mng LTE v cc gii php nng cao cht lng

h thng trong mng LTE.

1.2. Tng Quan Mng LTE.

LTE l mt trong cc con ng tin ti 4G. LTE s tn ti trong giai on u ca

4G, tip theo s l IMT-Advanced. 3GPP bt u hng n IMT-Advance di

ci tn LTE-Advanced.

LTE c xem nh l th th th t, th h tng lai ca chun UMTS do 3GPP

pht trin.Nm 2008, phin bn pht hnh cui cng 3GPP 8, mang li nhiu hn s

ci tin i vi HSDPA v HSUPA, c xem nh l pht hnh u tin ca

LTE.3GPP phin bn 9 tp trung vo nhng m rng i vi LTE. Mc tiu ca LTE

l cung cp 1 dch v d liu tc cao, tr thp, cc gi d liu c ti u, cng

ngh v tuyn h tr bng thng mt cch linh hot khi trin khai.

Cc c im ca LTE pht hnh 9

- Tng tc truyn d liu.

- m bo hiu sut khi di chuyn .

- Gim tr i vi mt phng ngi s dng v mt phng iu khin.

- K thut chuyn mch gi .

- ph sng t 5-100km .

Cc c im ni bt ca cng ngh 4G l:

1.2.1. H tr lu lng IP

S xut hin ca dch v VoIP cho thy vic truyn thoi c th d dng thc hin

qua mng IP chuyn mch gi.Kin trc mng 4G c xy dng vi mc tiu cung

cp dch v IP cht lng cao.

1.2.2. H tr nhiu cng ngh v tuyn khc nhau.

Trong cc h thng 4G, s dng nhiu cng ngh truy nhp v tuyn khc nhau. Xu

hng hin nay l s dng ph tn trong bng tn khng cn cp php ISM (Industrial,

scientific and medical radio bands): cng ngh Bluetooth (IEEE 802.15.1), tiu chun

IEEE 802.11b, IEEE 802.11a, IEEE 802.11g. Nt mng 4G c th thch ng cc kh

nng khai thc mt cch hiu qu c cc di tn cn trng.

1.2.3. H tr tnh di ng tt.

Trong cc h thng 4G, ngi dng s di ng trong mt vng c kch thc ng k

v giao tip thng qua cc thit b u cui v tuyn.Ngi dng phi c kh nng lin

lc bng mt s nhn dng duy nht. Nh vy, mng 4G s phi c mt phng tin

ph hp nhn dng ngi dng v cho php ngi dng iu khin s nhn dng v

thc hin nh x mt cch hiu qu n im ch chung.

1.2.4. Khng cn lin kt iu khin.

Trong trng hp ca bng tn ISM th c th lp mng Adhoc t mt nhm nt, cho

php cc nt giao tip trc tip vi nhau, thm ch cc nt c th cng tc vi nhau,

chuyn tip lu lng ca nhau.

1.2.5. H tr bo mt u cui u cui.

Trong cc mng 4G, yu cu v bo mt ln hn rt nhiu so vi mng 3G do mng

4G c kin trc m. Do cn phi c mt mun bo mt tch hp bo v d liu

gia cc mng khc nhau v hn na l mt m hnh bo mt bo v nhiu thc th.

Cc nt di ng v c nh s tng tc vi nhau khng cn lin h vi iu hnh

mng.Cc giao thc v th tc phi c kh nng cho php ngi dng trong cc nt

mng ny nhn thc thng tin nhn dng ngi dng v c th kt ni.y chnh

l tnh nng bo mt u cui u cui.

1.3. Tiu chun cht lng h thng mng 4G.

Bng 1.1 lit k cc yu cu ca IMT Advanced t ra bi ITU:

Hng mc Tiu chun IMT Advanced

Peak Data Rate (Downlink) 1 Gbps

Peak Data Rate (Uplink) 500 Mbps

Cp pht ph tn > 40 MHz

tr (User Plane) 10 ms

tr (Control Plane) 100 ms

Hiu sut ph nh (Downlink) 15 bps/Hz (4x4)

Hiu sut ph nh (Uplink) 6,75 bps/Hz (2x4)

Hiu sut ph trung bnh (Downlink) 2,2 bps/Hz (4x2)

Hiu sut ph trungbnh (Uplink) 1,4 bps/Hz (2x4)

Hiu sut ph ti bin t bo(Downlink) 0,06 bps/Hz (4x2)

Hiu sut ph ti bin t bo (Uplink) 0,03 bps/Hz (2x4)

Kh nng di chuyn Ti 350 km/h.

1.4 Kin trc mng LTE.

H thng 3GPP LTE c thit k m bo rng giao thc IP c kt ni gia

giao din UE vo mng li( core Network ). LTE h tr cho cc dch v chuyn mch

gi, hng n cung cp cc kt ni IP gia cc UE (User Equipment) v PDN (Packet

Data Network).Phng php chuyn mch gi cho php h tr tt c cc dch v bao

gm c thoi thng qua cc kt ni gi.

1.4.1. Mng Li (Core Network).

Li tin ha (EPC) l s pht trin ca mng li GSM v WCDMA.Kin trc tng

ca n c th p ng c cc dch v thng lng cao vi tr thp hn. EPC bao

gm cc node logic khc nhau nh:

- Thc th qun l di ng (MME).

- Cng phc v (S-GW).

- Cng mng d liu gi (P-GW).

- Chc nng iu khin chnh sch v cc quy lut tnh cc (PCRF).

- Server thu bao ti nh (HSS).

- Cc dch v Mutilcast Broadcast a phng tin (MBMS).

1.4.2 Mng truy nhp (Access Network).

Mng truy nhp v tuyn LTE s hu kin trc tng, bao gm cc nt NodeB tin

ha (Enode B).N x l tt c cc chc nng lin quan n v tuyn ca mng di

ng.EnodeB s dng giao din S1 kt ni vi li gi tin ha (EPC).

1.4.3. Kin trc giao thc v tuyn ( Radio Protocol Architecture).

- Giao thc S1-AP (S1 Application Protocol) c s dng trn mt phng iu

khin gia EnodeB v mng li (Core Network), MME.

- Giao thc ng hm GPRS (GTP-U): c s dng trn cc giao din ca mng

li (Core Network).

- Tn hiu iu khin L1/L2 cha gn lp lch ng xung v h tr lp lch ng

ln v bo nhn H-ARQ.

- Giao thc hi t d liu gi (PDCP): thc hin nn tiu gi tin IP, truyn vi

s lng bt t hn trn giao din v tuyn.

- Lp RLC: chu trch nhim phn chia, ghp ni, truyn li v sp sp chui tip

nhn ti cc lp cao hn.

- Lp MAC: chu trch nhim ghp knh d liu t cc ti tin v tuyn khc nhau,

truyn li H-ARQ v lp lch cho ng ln v ng xung.

- Lp vt l (PHY): chu trch nhim m ha/gii m ha, iu ch/ gii iu ch, x

l a anten v lp bn ca tn hiu n cc ngun ti nguyn thi gian- tn s vt l.

1.4.4 Enode B.

- Mng truy nhp v tuyn ca LTE ch bao gm c cc EnodeB (c gi vi cc

tn Trm gc BS) v RNs, nu c. Khc vi mng truy nhp v tuyn WCDMA

(UMTS), ni m nhiu EnodeB lin kt vi mt iu khin mng v tuyn n l

(RNC).Nhim v ca EnodeB khng ch kt ni thng qua giao din v tuyn, m cn

lp k hoch, cn bng ti, qun l di ng, qun l chuyn giao v qun l nhiu.

1.4.5 Giao din v tuyn

S a truy nhp

Trm BS kt ni vi MS thng qua khng kh, do cc dng bt c sn ti lp

MAC phi c iu ch truyn thng qua giao din v tuyn. Theo hng

Downlink a truy nhp phn chia theo tn s trc giao (O-FDMA) c chn. Theo

ng ln, 3GPP chn a truy nhp phn chia theo tn s sng mang n (SC-

FDMA). u im ca SC-FDMA so vi O-FDMA l t l cng sut trung bnh nh

(PAPR) nh hn do thit k b khuych i cng sut hiu qu hn.

V d : bng thng sng mang l 10 Mhz th c khong 50 RB.

10 Mhz = 50RB* 180kHz (9MHz) + 1 MHz ( bng bo v) (1.1)

Khong thi gian ca 1 RB c gi l 1 khe cm.

2 khe cm gi l 1 khung.

1.4.6 Cc vn v thu pht tn hiu

Trong phn ny chng ta cp n cc l thuyt v m hnh tnh ton lin quan

thu pht tn hiu

1.4.6.1 Chiu di tn hiu tip nhn

Trc tin chng ta mun bit cng sut tip nhn Prx l mt hm ca khong cch d

v cng sut chiu di tnh hiu truyn Ptx . Khi gi nh mi trng th, M hnh

suy hao ng truyn Hata c xem xt :

L(di ) = Lfix + 10a log10 (d) [dB] (1.2)

Trong Lfix l mt tham s ph thuc vo chiu cao anten, tn s truyn sng ... a l

tn hao ng truyn theo quy lut hm m, d l khong cch gia MS vi EnodeB

(km).

1.4.6.2 Nhiu v tp m

Nhiu

Nhiu l 1 iu khng mong mun t cc thit b trong cc Cell phc v khc nhau.

Bi v trong Cu trc mng LTE/E-UTRAN mi Cell s dng cng bng tn ging

nhau, iu ny ny sinh mt vn . ngn chn iu ny cc EnodeB phi giao tip

vi nhau VD: hai MS trn hai Cell phc v khc nhau s khng pht tn s ging nhau

ti 1 thi im.

Tp m

Tp m l 1 bin ngu nhin trong tn hiu in. Tn ti nhiu ngun tp m khc

nhau nh tm m do nhit , do bn, tp m nhp nhy v tp m n. y chng

ta quan tm n tp m do nhit c m t bi phng trnh:

P= Kb T *f [W] (1.4)

Hoc c th tnh theo dBm:

PdBm = 10 Log10 (Kb T f *1000 ) = 10 Log10(Kb T *1000 ) + 10 Log10(f) (dBm).

Vi Kb = 1.38 10-23 J / K , nhit phng T= 293K PdBm = -174 + 10 Log10(f)

[dBm] .

1.4.6.3 Tc d liu

Theo nh l Shannon- Hartly :

C=BW* Log2(1+S/N ) (1.5)

Trong : C l ti a kh nng knh li (b/s)

BW bng thng (Hz)

S Trung bnh cng sut tn hiu

N ting n Gauss trng cng

y chng ta thy rng vi t l S/N cao hn, th bn c th t c cng sut ti

a C cao hn.S dng cng ngh LTE, cng sut ti a ny khng c. Tuy nhin

theo 3GPP11 tc d liu s dng cng ngh LTE ng ln t l thun vi cng

sut ti a bng cch s dng lin tc ton t = 0,4

Do m hnh tc d liu ng ln tr thnh

C= 0.4*180kHz* Log2 (1+S/N )

M hnh ny tnh ton chnh xc hn tc d liu trong LTE/UTRAN. Ngoi tra

trn thc t tc d liu cn phc thuc vo ch s ring bit MCS (s iu ch v

m ha), CQI (cht lng knh truyn) m phng tc d liu ca MS. iu ch

s dng trong cng ngh LTE l 16QAM nhng trong phin bn LTE-advanced l

64QAM nhng khng phi tt c MS u h tr 64QAM. Nn 16 QAM c dng

iu ch ti a.

1.5. Gii php nng cao dung lng v cht lng dch v h thng 4G

LTE

1.5.1. Kt hp bng thng

Gii php ny nhm mc ch t c yu cu v tc d liu nh (peak data

rate). Vic kt hp bng thng cc knh tn s 20 MHz l phng n kh quan hn

v d tm kim ph tn. N l mt trong nhng chc nng quan trng ca LTE-

Avanced.

Hnh 1.7 Kt hp sng mang trong mng LTE-Advanced.

1.5.2. H MIMO bc cao v nh hng bp sng

LTE phin bn 8 h tr ti 4 my thu v my pht trn eNB, ti 2 my pht v 4 my

thu cho UE. Kh nng tng li thu t cc h MIMO v t iu khin bp sng

(beamsteering) l hm ca s lng cc anten. xut c th tng con s ny ca h

thng ln n 8x8 vi eNB v 4x4 cho UE. Ti eNB, anten 4x ang c s dng. Nu

tng ln 8x phi lp t thm mt s thit b trn ct trnh chi ph khi tng thm

cp.

Hnh1.8 H MIMO bc cao

1.5.3. H MIMO phi hp

S khc bit gia h MIMO tiu chun v h MIMO phi hp c th hin trn

hnh sau:

Hnh 1.9 Ba kiu MIMO phi hp trong h thng di ng

S khc nhau r rng nht l h MIMO phi hp, thit b pht khng t gn nhau

v mt vt l. H MIMO nhiu ngi dng trong ng uplink cng c cc thit b

pht c lp theo cc UE khc nhau nhng khng c kh nng chia s d liu gia cc

UE phc v mc ch phi hp tin m ha.

1.5.4. S dng Relay.

Mt phng php khc khc phc, m rng vng ph sng trong cc iu kin

kh trin khai l s dng Gii Php Relay.

Hnh 1.10 S dng Relay

Phng php n gin nht l s dng mt b lp (Repeater) lm nhim v tip

nhn, khuch i v truyn li tn hiu downlink v uplink khc phc tnh trng ph

sng yu.

1.5.5. Mng t ti u ha.

Ngy nay cc h thng thng tin di ng t bo ngy cng c tp trung v vic a

thm cc node vo mng s gy tn km v ti chnh v thi gian.Mt tnh nng ang

c xem xt ca LTE Advanced l khi nim Mng t ti u ha (Self

Optimizing Network SON).Li ch ca n l gip gim nh hng ca vic a

thm cc node mi vo mng.Cc khi nim ny c cp n phin bn 8 v tip

tc trong cc phin bn 9 v 10.

1.5.6. S dng Femtocell.

Femtocell c th c trin khai ti cc h gia nh, cng ty hoc ti cc khu vc

cng cng nh nh ga sn bay .Phn ln femtocell c trin khai trong nh nn c s

cch ly gia femtocell v macrocell. Vic trin khai femtocell/hotspot khng phi l

cnh tranh vi micro/macro cell m l b sung, m bo cht lng h thng.

Hnh 1.11.Femtocell trong LTE.

1.5.7. iu phi v gt nhiu.

S p dng cng ngh OFDMA vo h thng thng tin di ng t ong (bt u t

802.16e v tip tc vi LTE/SAE) lm thay i ln v gt nhiu bin t

bo.Trong k thut OFDMA kh nng lp lch chn tn vi knh truyn m ra kh

nng v ti u ha cc thng s trong t bo nhng nhiu ng knh trong t bo tr

nn bin i nhiu hn.Vic nghin cu cc tc ng ca loi nhiu ny vn ang

c tin hnh.

1.6. Kt lun chng

Mng LTE ra i th hin nhng u im vt tri so vi cc mng 3G th h

trc. Chng ny trnh by nhng tiu chun ca mng 4G IMT Advanced ca

ITU v a ra mt s gii php nng cao cht lng h thng, trong c vn

Gii Php Relay trong mang LTE. Trong chng 2, chng ta s phn tch gii php

ny trong h thng thng tin di ng v trong mng 4G LTE.

CHNG 2 GII THIU CNG NGH MNG RELAY TRONG LTE

2.1 Gii Thiu Chng

Trong chng ny chng ta s cp n cc vn lin quan n trin khai mng

LTE, Cc cng ngh mng Relay, mc ch s dng, cc u v nhc im ca trm

Relay, phn loi trm Relay trong mng LTE. Phn tch s truy nhp v tuyn v kin

trc cho trm Relay.

2.2 Gii Thiu Cng Ngh Mng Relay Trong LTE.

Trong qu trnh chun ha h thng thng tin di ng th h tip theo, nh l 3GPP

LTE_advanced, cng ngh trm chuyn tip ang c xem xt v nguyn cu. Mt

c s h tng mng dy c c th c trin khai bng cch trin khai cc trm

chuyn tip Relay, iu ny lm gim khong cch ngi dng thit b di ng UE n

trm pht sng do t tc truyn ti cao hn. Bn knh vng ph sng v nng

lc ti vng bin gii ca Cell ph sng vn cn tng i nh do t s SINR thp.

Vic pht trin cc Node trm chuyn tip Relay ti cc vng bin gii ca Cell ph s

gip tng cng nng lc vng ph v m rng bn knh vng ph sng .

Theo cch m lin kt truyn dn khng dy c phn b, cc RNs c th c

phn loi nh sau :

+ Trong bng, khi kt ni backhaul c phn b trn cng tn s sng mang nh

cc kt ni truy nhp.

+ Ngoi bng, khi kt ni bachhaul v kt ni truy nhp c phn b tn s khc

nhau.

2.2.1 Cc vn lin quan ti trin khai mng LTE

2.2.1.1 Th tc khi ng trm chuyn tip Relay

Khi 1 trm chuyn tip mi c trin khai trong mng, n s t ng gn n vo

mng di ng.Th tc ny da trn th tc thit b ngi dng UE thng thng kt

ni vo mng.C 2 phn trong th tc khi ng ca trm chuyn tip.

Giai on th nht : nt chuyn tip Relay to ra kt ni RRC ti trm gc EnodeB

v lin kt vi chnh n nh l mt thit b ngi dng UE thng thng cu hnh

khi to.

Giai on th hai: nt chuyn tip Relay kt ni n trm gc (BS) la chn t

danh sch trong gian on u tin. Cc nt chuyn tip Relay s gi mt ch s

chuyn tip n trm gc (BS) trong qu trnh thit lp kt ni RRC.

2.2.1.2 Th tc UE lin kt.

C 2 trng hp lin quan n th tc lin kt UE vo trm chuyn tip. Trng hp

th nht UE ban u lin kt vi trm Relay khi khi ng v trng hp khc l UE

ban u lin kt vi trm gc sau khi khi ng, v by gi n cn lin kt vi trm

chuyn tip sau khi la chn li vng ph Cell trong trng thi RRC IDLE.

Trong trng hp u tin, vic hon thnh kt ni logic S1 lin kt vi UE ti

mng li c thc hin do 1 thit lp kt ni RRC c kch hot bi 1 nt chuyn

tip.

Trng hp 2 thuc v loi di ng LTE trong trng thi RRC IDLE.Tt c cc th

tc di ng LTE trong trng thi RRC-IDLE c thc hin c lp trong UE.

2.2.1.3 Th tc chuyn giao

2.2.1.3.1. Chuyn giao t trm Relay n trm gc EnodeB

Trong RRC_CONNECTED, E-UTRAN quyt nh Cell ph m UE nn chuyn giao

m bo ng truyn v tuyn .

Trong hnh trn da trn bo co o c trn UE, nt chuyn tip quyt nh c nn

bt u mt chuyn giao hay khng. Nu c, nt chuyn tip Relay s la chn mt

mc tiu Cell ph cho UE.Sau , Relay s gi bn tin yu cu chuyn giao ti trm

EnodeB.EnodeB s tm mc tiu EnodeB t bn tin v chuyn tip bn tin X2 hng

ti EnodeB.Sau khi tip nhn bn tin bo nhn ACK yu cu chuyn giao, nt chuyn

tip gi mt lnh chuyn giao ti UE.UE sau s tch ra v ng b vi mc tiu

EnodeB.

2.2.1.3.2 Chuyn giao t EnodeB ti Relay

Trong trng hp chuyn giao t EnodeB n Relay, th tc ca n ging nh

chuyn giao t ngun EnodeB n mc tiu Enodeb khc.T quan im ca UE, Relay

ging nh mt EnodeB. UE thng bo o lng ca n ti ngun EnodeB. Ngun

EnodeB s quyt nh chuyn giao ti trm Relay.Sau trng thi chuyn giao c

thc hin, yu cu chuyn giao c gi n trm Relay thng qua EnodeB.Nu trm

chuyn tip Relay c th chp nhn UE, mt bn tin c chuyn ti UE bt u

chuyn giao. D liu ng xung n ti EnodeB ngun ti UE c truyn n trm

Relay.

2.2.2 Mc ch s dng Relay trong Mng LTE

Mc ch s dng Relay trong mng Long Term Evolution (LTE) l cung cp m

rng vng ph sng v tc cao hn cho ngi dng di ng cnh bin ca Cell

phc v .Tng t nh bt k cc nt mi khc trong mng LTE, Trm chuyn tip

mang li nhng thch thc mi.Mt trong nhng thch thc lin quan n tnh di

ng.C th hn, truyn ti d liu qua ligia cc trm DeNB v nt Relay (RN)

trong qu trnh chuyn giao c th xy ra.

2.2.3 Cc u im v nhc im trong vic s dng trm chuyn tip

Relay

2.2.3.1 Cc u im

+ Mc ch chnh ca gii php Relay l cung cp tc d liu nh h tr cc

dch v d liu cao hn.

+ RNs tng cng thng lng trn ton mng bng cch s dng hiu qu cc tin

ch ngun ti nguyn mng.

+ RNs ang l 1 gii php chi ph trin khai hiu qu, ang c nhiu nh iu hnh

mng quan tm.

+ RN mang li li ng k cho ch s SINR thng qua k hoch mng hp l.

2.2.3.2 Nhc im.

+Trong chuyn tip, DenodeB s dng mt vng ti nguyn v tuyn chung mt

trong 3 lin kt: lin kt trc tip (UEs n DenodeB), lin kt Relay (t DenodeB n

Relay) v lin kt truy nhp (t UEs n trm Relay). Hn na, trong chuyn tip

trong bng, lin kt Relay v lin kt truy nhp s dng chung ti nguyn v tuyn

thng qua s dng k thut ghp knh phn chia theo thi gian (TMA), do n cng

lm gim hiu sut ca RN.

+RNs c bn knh vng ph nh do cng sut pht thp, li anten thp v tn hao

ng truyn cao theo s m.

+RNs cng cn c ti nguyn v tuyn cho cc ng kt ni Relay, kt ni

vi DenodeB.

+RN cng l nguyn nhn gy ra tr h thng trong qu trnh x l tn hiu trc khi

truyn i.

2.3 Chuyn Tip Trong LTE

2.3.1.1 Chuyn tip loi 1.

Chuyn tip loi 1 cn c gi vi 1 ci tn khac l Booster hay Repeater. y l

mt kiu cng ngh chuyn tip khuych i v chuyn tip tn hiu (AF) bng cch

tn s tn hiu v tuyn ng xung ( downlink) t trm gc s c khuych i v

truyn n thit b ngi dng UE.. Vi nhng c im trn, chuyn tip loi 1 c

s dng rng trong cc h thng thng tin di dng 2G v 3G. N c nghin cu

m rng vng ph cc khu vc i ni cao, cc khu vc dn c tha tht v cc khu

vc nng thn. Tuy nhin n cng khuych i i nhiu lin Cell (inter-cell) v tp

m cng vi tn hiu mong i .

iu ny lm gim t s tn hiu trn nhiu SINR v lm gim li nng cao thng

lng ( throughput-enhancement).

2.3.1.2 Chuyn tip loi 2.

Chuyn tip loi 2 l mt kiu cng ngh chuyn tip gii m ha v chuyn tip

(DF) bng cch tn hiu tip nhn RF ng xung t trm gc c gii iu ch v

gii m ha v sau c gii m ha v iu ch mt ln na trc khi chuyn n

cho thit b ngi dng UE. Vic x l gii m ha v gii iu ch c thc hin ti

cc trm chuyn tip qua. iu ny lm tng t s SINR, cc nhiu lin Cell v tp

m s c x l v khng c khuych i chuyn tip. Do nng cao thng

lng s tt hn khi so snh vi chuyn tip loi 1.

2.3.1.3 Chuyn tip loi 3

Chuyn tip loi 3 cng thc hin tip gii iu ch v gii m ha ca tn hiu v

tuyn RF tip nhn trn ng xung t trm gc nhng sau cng thc hin x l

(mt m ha (Ciphering), s ghp ni/ phn chia/ rp li d liu ngi dng User-data)

truyn li d liu ngi dng trn giao din v tuyn v cui cng thc hin gii m

ha v iu ch v truyn n thit b ngi dng UE. Cng ging nh chuyn tip

loi 2, chuyn tip loi 3 cng lm ci thin thng lng bng cc loi b nhiu lin

Cell (inter-cell) v ting n .

2.4 Truy nhp v tuyn cho cc trm chuyn tip Relay.

2.4.1 Cu hnh khung v tuyn cho cc trm chuyn tip

Mt gii php l s dng mng tn s n l Muticast /Broadcast (MBSFN), cu

hnh cc khung con trong cc khung con tip nhn bi trm chuyn tip tip nhn tn

hiu t trm gc (BS). Trong phng php ny mt tn hiu tham kho v cc tn hiu

iu khin Relay loi 1/ Relay loi 2 c t ti rt nhiu pha trc ca khung con,

ch chim 2 k t. Trong phng php ny mt thit b ngi dng UE c th nhn ra

rng khng c d liu truyn t trm chuyn tip trong 1 khung con ca chnh n trong

cc trm chuyn tip tip nhn cc tn hiu t trm gc. Ti 1 thi im ging nh

vy, thit b ngi dng UE c th o cng tn hiu RF tip nhn t trm chuyn

tip Relay so vi tn hiu tham kho trong 2 k t u tin ti pha trc khu nh.

2.5 Giao thc v Tuyn cho cc trm truyn tip Relay.

Trong cng ngh chuyn tip loi 3,Trn thc t, trm chuyn tip c trang b giao

thc hi t gi d liu (PDCP) v mt m ha v nn tiu cho d liu ngi

dng.Giao thc iu khin kt ni v tuyn (RLC) iu khin truyn li bi ARQ.S

trng hp/ phn khc/ rp li cho khi d liu dch v (SDU) v trnh t gi tin tip

nhn.Giao thc iu khin truy nhp trung bnh (MAC) cho HARQ v s d liu

ngi dng v giao thc iu khin ngun v tuyn cho di ng, cht lng dch v

(QoS) v iu khin bo mt.

Thm vo khi qun l ng kt ni backhaul v kt ni truy nhp v tuyn trn

cng tn s c miu t nh trn. Qun l vic ghp knh phn chia theo thi gian

TDM c yu cu gia hai kt ni trn vic yu cu iu khin v tuyn lin kt.

iu ny c hon tt bi cung cp 1 phng php cho vic nh v ngun ti nguyn

ti kt ni v tuyn backhaul.

2.6 X l tn hiu trong trm chuyn tip ca h thng s dng m turbo.

M turbo c la chn nghin cu trong cc h thng dng trm chuyn tip

thng minh v gn y loi m ny c xut s dng trong hu ht cc chun di

ng mi nh W-CDMA (HSPA), cdma2000 1x EV-DO (Rev A, B, C) hay Mobile

WiMAX nhm nng cao cht lng truyn dn tn hiu trong mi trng v tuyn

h.Vic ghp xen k cc bit thng tin ca ngi dng trm chuyn tip thng minh

nhm mc ch to s lin kt gia thng tin ca cc ngi dng vi nhau tng

li phn tp khng gian

2.7 Kin trc mng cho cc trm chuyn tip

Trm chuyn tip (Relay station) phi c chc nng tng ng vi nhng chc nng

ca trm pht sng gc, cc nghin cu mi phi c thc hin trn nhng chc nng

iu khin v phng thc truyn ti ngi dng cn thit ti giao din gia trm pht

sng gc v trm chuyn tip v ti giao din gia trm chuyn tip v 1 trm chuyn

mch nh l mt thc th qun l di dng (MME) hoc l cng phc v (S-PW).

Hnh 2.10 Kin trc mng v tuyn cho trm chuyn tip loi 3.

2.8 Kt Lun Chng

Trong chng ny lun vn gii thiu ton cnh cng ngh chuyn tip hin tai

c tiu chun trong h thng LTE-Advanced. Cho n nay trm chuyn tip c

pht trin nh mt Repeater m rng vng ph cho h thng kt ni di ng 3G ti

cc vng i ni, cc vng dn c tha tht v cc hi o xa xi. Trong h thng

LTE, cng ngh chuyn tip loi 3 c gii thiu thay v cc repeater (gy nhiu lin

Cell( inter-cell) v ting n) lm cho t s SINR tng ln v tng cng s dng thng

lng hiu qu. Cc tiu chun k thut trm truyn tip ang c nghin cu v pht

trin trong phin bn LTE.10 m rng vng dch v LTE mt cch c hiu qu v

kp thi.

CHNG 3 NGHIN CU HOT NG CA RELAY TRONG MNG LTE

3.1 Gii Thiu Chng

Mt trong nhng thnh phn cng ngh mi trong pht hnh phin bn cho LTE-

Advanced chnh l kt ni chuyn tip (Relay).LTE-Advanced s dng kt ni

chuyn tip tng hiu nng ca mng LTE bng bng cch thm vo cc nt mng

trong cc vng, ni c cc vn nht nh v vng ph.Cc nt chuyn tip c cng

sut pht nh hn so vi cc Nt B pht trin c vng ph rng ln (cc nt B pht

trin macro) v ng trc l khng dy.

3.2 Vn can nhiu khi s dng Relay.

Phi hp nhiu lin Cell (CICI) c nghin cu t h thng GSM. Trong k

thut ny, ba t bo ln cn chia tng s bng thng ca h thnh ba phn vi mi t

bo s dng 1 phn ca n nh m hnh hnh lc gic ang c s dng, cc t bo

vi cc bng thng ging nhau s khng bao gi lin k nhau. Vi k thut ny r rng

gp mt bt li, l tng s bng thng c chia thnh 3 phn v khi phn b ti

nguyn trong h thng LTE gim ng k.

Thng qua vic s dng cng tn s vi trm gc l nguyn nhn gy ra nhiu knh

lin Cell (inter Cell co-channel interference).

3.3 Mt S c im Ca Cc Relay Station

3.3.1 Da trn tiu ch k thut .

3.3.1.1 Relay Amlify and forward.

Chuyn tip khuych i v chuyn tip AF: l mt dng chuyn tip song cng,

khuych i tn hiu t bc trc v truyn li ti bc th 2. AF c mt h ch l

khuch i c nhiu v tp m cng vi tn hiu mong mun . iu ny lm gim t

s SINR tng th cng nh hn ch thng lng ca h thng. Trong chuyn tip AF,

tn hiu truyn trn ng truy nhp c th r r ti ng tip nhn tn hiu chuyn

tip gy nhiu vng (Loop interference) .

3.3.1.2 Relay Decode and Forward.

Gii m v chuyn tip (DF): l mt k thut chuyn tip , ton b tn hiu tip nhn

t nt trc c gii m v truyn li cho thit b ngi dng UE. N gy ra tr x l

tn hiu v phc tp trong qu trnh m ha /gii m ha li ca tn hiu.Trong chuyn

tip DF, thng lng qua trm chuyn tip Relay v cc truy nhp lin kt c th c

ti a, nu c hai lin kt c thng lng bng nhau.

3.3.2 Da trn c s h tng.

3.3.2.1 Fixed Relay Sation.

RNs c th c phn loi t quan im trin khai mng , n c th trao i thng

tin cho nhau v c th trin khai trn cc phng tin giao thng di ng . RNs c nh

thng c trin khai trong mng ci thin vng ph sng v nng lc mng ti

cc vng bin ca Cell ph, cc vng lm do b che chn nh trong hnh sau :

Hnh 3.7 Trm chuyn tip c nh.

Chng c th c s dng vng ph sng trong mng cho cc ngi dng bn

ngoi khu vc di dng . RN c th c trin khai trn cc thp , ct, cc nh ca ta

nh hoc cc ct n in. Chiu cao anten c gi thp hn so vi trm gc.Cc nh

khai thc mng c th lp k hoch t c v tr RN tm nhn thng (LOS) so

vi trm gc.

3.3.2.2 Nomadic Relay Staion.

Trm chuyn tip tm thi cho php trin khai trm RN tm thi cung cp b

xung vng ph v nng lc mng ti cc khu vc , ni m cc trm ENodeB hoc trm

Fixed Relay c vng ph yu khng m bo QoS , hoc ni ang xy ra cc s c tc

nghn mng (vd cc l hi , cc ni tp trung ng ngi trong 1 thi im nht nh).

Chiu cao anten tng i thp . Cc kt ni truy nhp c th c thc hin trn c

hai knh tm nhn thng (LOS) v knh b che chn ( NLOS). N thng hot ng

ch acquy nn cu trc vt l tng i nh gn so vi trm Relay thng thng.

Hnh 3.8 Trm chuyn tip tm thi

3.3.2.3 Mobile Relay Station

Trm chuyn tip di ng thng c gn trn cc thit b giao thng (Vd xe but,

xe la ) nhm mc tiu cung cp dch v di ng tt bn trong cc phng tin giao

thng. N kt ni vi trm gc thng qua lin kt chuyn tip di ng khi kt ni vi

thit b ngi dng UE bn trong phng tin thng qua lin kt truy nhp. Chiu cao

anten tng i thp do hn ch ca phng tin giao thng v vn hnh an ton.

Hnh 3.9 Trm chuyn tip di ng.

3.4Tiu ch la chn v tr t trm chuyn tip

3.4.1 Khu vc dch v ca trm chuyn tip

Trong phn th nghim ny, khu vc dch v ca RN s c tnh ton.Khu vc dch

v cho thy vng ph ca RN c thit b ngi dng s dng UE. Chng ti s

dng 1000 zones v 999 secters m phng Cell ph. Chng ti tnh ton khu vc

dch v cho 3 v tr khc nhau ca RN, c th l 25%, 50% v 75% i vi phn bin

ca Cell nhn t trm gc.

Chng ta thy khu vc c trm chuyn tip s cho kt qu tc cao hn.Vic s

dng nhiu hn 1 RN s m rng khu vc dch v cho thit b ngi dng UE.

iu ny cng cho thy rng vic m rng khu vc dch v ln hn khng c ngha

lm gia tng s nh hng ca trm chuyn tip ln ton b thng lng v thi gian

chuyn gi tin trung bnh trn Cell ph .

3.4.2 Tng s Thng lng Uplink v nh hng n khn nng ca Cell

phc v.

Chng ti cng lm theo kch bn trong th nghim trc nhng khu vc dch v

gim xung cn 500 zones v 499 sectors. Vic lm nh vng phc v s lm tc

m phng nhanh hn v cho kt qu m khng nh hng nhiu n kt qu chnh xc

ca m phng.

Phn m phng ny c thc hin vi tc n gi tin t 4-7Mbit/s vi 0,5

mi bc, v trng hp trm chuyn tip v khng c trm chuyn tip.

Hnh 3.13 Tc n ca gi tin trong trng hp c v khng c trm chuyn tip.

Trng hp khng trin khai trm v trin khai trm chuyn tip ti mc 25% t

cng sut ti a l 5.3Mbit/s. Trm chuyn tip Relay mc 50% v 100% cho cng

sut ti a l 5,7 Mbit/s v trm chuyn tip mc 75% t 5,8Mbit/s. Trong hnh trn

chng ta cng thy c tng thng lng h thng c th tng 10 % khi lin kt vi 1

trm chuyn tip.

Trong hnh trn cng th hin RN ti mc 75% cho kt qu tng thng lng ng

ln (uplink) cao nht iu ny khng ng ngha vi khu vc phc vc l ln nht. L

do c th c gii thch 2 phn sau :

+Thi gian chuyn d liu UE c h tr c tng tng i v UE gn trm

Relay hn nhng vng sng yu.

+ Hu ht iu khin t xa ca thit b ngi dng do nt c trai ca h thng iu

khin nn h s gi cho trm Relay lun bn h tr UE trong vng ph ca n tt

hn.

3.4.3 nh hng ca v tr RS

Trong phn th nghim ny , chng ta gim bt vng phc v xung cn 50 zones v

49 sectors. Vi tc n t 1-6 Mbits/s vi mi bc cch nhau 1 v cho cc khu

vc Relay mc 25%, Relay mc 50%, Relay mc 75% v Relay mc 100% i vi

bn knh bin Cell ph sng. Hiu sut o lng c nghin cu trong th nghim

ny l thi gian chuyn d liu (file) trung bnh.

Ti v tr Relay mc 25% gn bin ca cell c khu vc dch v hp l v Relay gn

trm gc hn c nn nh hng ca trm Relay l st gii hn. Vi = 5 ti v tr

Relay mc 25% thi gian truyn d liu trung bnh kh cao v lm h thng hu nh

khng n nh. Vi v tr Relay mc 50 % v Relay mc 100 % c hiu nng h thng

tt hn. V Relay mc 75% cho thi gian truyn d liu trung bnh tt nht.

3.5 Phng n s dng Relay trong mng LTE

3.5.1 i vi khu vc nng thn ( Rural Area).

Cc dch v khu vc nng thn c c tnh vng ph sng rng v mt ngi

dng thp.V vy, mt cu hi u tin quan tm n l cc nh iu hnh mng lm

th no gim chi ph trin khai.Trong 1 kch bn nh vy, trm chuyn tip Relay s

cung cp mt gii php hiu qu trong vic gim s lng cc trm Marco EnodeB.

Nhn chung do a hnh nng thn nn ng truyn LOS s c chi phi, ng

truyn NLOS l tng i him tr khi a hnh i ni cao hoc c ph bi thm

thc vt cao.

Hnh 3.17 Khu vc nng thn cho cc trm Relay.

Vic trin khai cc trm Relay c cng sut cao v vic quy hoch mng l rt quan

trng.

3.5.2Khu vc th ( Urban Host Spot)

Tri ngc vi khu vc nng thn, khu vc th mt ngi s dng l kh cao

v thng phn b khng ng u.Mc ch chnh trin khai trong khu vc ny l

nng cao nng lc ca mng. Do phm vi vng ph ca mi RN tng i nh v

nhiu RN s c trin khai trong phm v vng ph Marco EnodeB. C th c nhiu

vng ph chng ln nhau gia cc RN.

Hnh 3.18 Trin khai Relay trong khu vc ni th.

3.5.3 im cht ( Dead Spot).

Cc im cht thng pha sau xung quang cc ton nh cao tng ni m sng v

tuyn ca trm gc khng th n c .Mi trng truyn tng t nh mi trng

th.Nhiu ch yu l ting n ni Repeater c th l mt gii gip thay th ngoi

chuyn tip DF.

Hnh 3.19 Trin khai Relay trong khu vc im cht.

3.5.4 im Nng Ta Nh (indoor host spot).

Chuyn tip c th c s dng t c thng lng d liu cao trong nh.

Hin tng Fading c xu hng tng do sng phn x v khc x i vi cc bc

tng chn. Chuyn tip cung cp tng cng thng lng v phc v ngi dng

trong nh cc khu vc vng ph sng yu. Do vy nng lc vng ph Marco c

tng ln.

Trong cc ta nh cao tng, ngi dng ti cc tng khc nhau s tri nghim cht

lng knh truyn khc nhau.T s SINR s thp. Do trong trng hp ny, mt

anten nh hng trn nt chuyn tip Relay ch v pha EnodeB c th tng cng

hiu qu cng tn hiu t EnodeB lm ci thin t s SINR. Ngi ta mong i

mt s lng ln thit b ngi dng UE (t 30-100) c th c h tr t Relay.

Hnh 3.20 Trin khai Relay trong cc ta nh

3.6 Kt Lun Chng

Cc mng li v cc mng truy cp v tuyn, ni m cc mng truy cp kim sot

ca giao din v tuyn.V vy kim sot ti nguyn ng ln, cc ngun ti nguyn

v tuyn c chia cho cc trm chuyn tip Relay, l lch trnh ca eNode-B.

Mt cu tr li quan trng c lin quan n thc t l vic s dng trm chuyn tip

lm hn ch v vic s dng cc khi ti nguyn, nh MS s dng trm chuyn tip

Relay ch c th truyn trn mt na ca trm chuyn tip Relay c giao cho n,

nh l mt na khc l cn thit cho cc giao tip gia trm chuyn tip Relay v trm

gc (BS).

Lun vn pht trin mt m hnh Matlab m phn tch t bo thnh nhiu phn,

mi phn c kch thc bng nhau, c gii quyt bng mt khu vc v khu vc ta

. S dng ny m hnh ca t bo, chng ta c th d dng m phng cc dch v

ca ngi dng bn trong t bo: tnh ton tc d liu ca MS mt m hnh mt

ng dn v nh l Shannon cho tc d liu ti a c s dng.

Mt s th nghim hiu sut c thc hin. u tin khu vc dch v ca trm

chuyn tip c kho st, s dng cc v tr khc nhau ca RS v khc nhau s

lng RBS c sn cho MS. Quan st thy rng RS nm 75% i vi bin vng ph

sng, c khu vc dch v nh nht, nhng c th kt lun rng iu ny khng c

ngha rng n l thc hin chc nng yu nht.

Lun vn nghin cu tng lng ng ln v nng lc h thng. Ngi ta thy rng

cc RS t 75% i vi cc bin vng ph c tng lng ng ln cao nht, v do

cng c cng sut h thng cao nht. iu ny c th hin hn na trong cc

th nghim cui cng, ni m thi gian chuyn i cc tp tin trung bnh cho tng

phn khc gn vi cc v tr khc nhau v RS c kho st .

V vy, c th kt lun rng ni tt nht xc nh v tr mt RS l 75% gn bin

vng ph sng , gi nh rng ch c mt vng ph sng duy nht c s dng, khng

c s can thip t cc vng ph ca cc Cell khc, lp lch FWC c s dng. Trong

nghin cu ny khng th hin s tc ng nhiu t cc trn chuyn tip Relay vo

vng ph ca Cell cng nh s dng k thut ti s dng tn s trnh nhiu.

KT LUN V HNG NGHIN CU TIP THEO

1. KT LUN

Sau qu trnh tm hiu v nghin cu thc hin lun vn tt nghip, vi s n lc ca

bn thn, cng vi s hng dn tn tnh ca TS. V Trng Thnh v cc ng

nghip cho n nay ti hon thnh lun vn c bn p ng c cc yu cu t

ra.

Kt qu t c ca lun vn

- Ph tn v tuyn ti nguyn c bn s thc y chnh i vi cc nghin cu LTE

v sau LTE trn th gii trc tip dn n cc h thng s dng ph tn hiu qu.

- Ch ra c cc c im k thut vt tri mng di ng 4G LTE so vi cc mng

trc v tc d liu, khn nng p ng tt vi cc ng dng thi gian thc cht

lng cao.

- Phn tch cc gii php nng cao dung lng h thng mng 4G : Kt hp bng

thng, H MIMO bc cao, H MIMO phi hp, s dng Relay, s dng Femtocell,

mng t ti u ha v iu phi v gt nhiu

- Phn tch su gii php Relay trong mng LTE v nguyn l hot ng, cc u

nhc im, phn loi cc loi trm chuyn tip v khn nng ng dng Relay trong

mng 4G LTE.

- Lun vn nghin cu tng lng ng ln v nng lc h thng. Ngi ta thy

rng cc RS t 75% i vi cc bin vng ph c tng lng ng ln cao nht,

v do cng c cng sut h thng cao nht. Lun vn ch ra cc khn nng ng

dng ca trm Relay trong mng LTE trong cc mi trng, khu vc khc nhau.

2.Kin ngh v hng nghin cu tip theo

-Nghin cu, ng dng gii php Relay trong qu trnh trin khai mng 4G LTE trn

th gii ni chung v Vit nam ni ring.

-Nghin cu cc gii php khc khc phc vng ph bn cnh gii php Relay nh

Pico hay Femtocell