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Trong nhng nm gn y, mng khng dy ngy cng tr nn ph bin vi s ra i ca hng lot nhng cng ngh khc nhau nh Wi-Fi (802.1x), WiMax (802.16)...Cng vi l tc pht trin nhanh, mnh ca mng vin thng phc v nhu cu s dng ca hng triu ngi mi ngy. H thng di ng th h th hai, vi GSM v CDMA l nhng v d in hnh pht trin mnh m nhiu quc gia. Tuy nhin, th trng vin thng cng m rng cng th hin r nhng hn ch v dung lng v bng thng ca cc h thng thng tin di ng th h th hai. S ra i ca h thng di ng th h th ba vi cc cng ngh tiu biu nh WCDMA hay HSPA l mt tt yu c th p ng c nhu cu truy cp d liu, m thanh, hnh nh vi tc cao, bng thng rng ca ngi s dng.

Mc d cc h thng thng tin di ng th h 2.5G hay 3G vn ang pht trin khng ngng nhng cc nh khai thc vin thng ln trn th gii bt u tin hnh trin khai th nghim mt chun di ng th h mi c rt nhiu tim nng v c th s tr thnh chun di ng 4G trong tng lai, l LTE. Cc cuc th nghim v trnh din ny chng t nng lc tuyt vi ca cng ngh LTE v kh nng thng mi ha LTE n rt gn.

Tuy vn cn kh mi m nhng mng di ng bng rng 4G ang c k vng s to ra nhiu thay i khc bit so vi nhng mng di ng hin nay. Chnh v vy, em la chn lm n tt nghip v ti CNG NGH LTE V QUY HOCH MNG 4G LTE hiu bit hn v cng ngh mi ny.

Em xin gi li cm n chn thnh n c TS. Nguyn Th Qunh Hoa v cc thy c gio gip em hon thnh n ny!

Ngh An, ngy 6 thng 1 nm 2012

TM TT N n ny i vo tm hiu tng quan v cng ngh LTE, vi nhng yu cu ca LTE c t ra nh gim gi thnh so vi cc cng ngh trc , tng cng h tr cho cc dch v li nhun cao v ci thin khai thc bo dng cng nh cung cp dch v, nng cao hiu qu ph tn, thng lng ngi s dng, gim thi gian tr. t c cc mc ch LTE s dng nhng tnh nng quan trng nh cng ngh truyn dn OFDM cho ng ln, SC-OFDM cho ng xung, cng ngh a ng ten MIMO cho h thng thu pht, truyn dn v tuyn tc cao dng bng thng rng. Kt hp vi cc cng ngh khc nh: thch ng ng truyn v lp biu, cc k thut chuyn giao, iu khin cng sut v HARQ. Cc cng ngh mi ny c p dng cho truy cp v tuyn cho php tng hiu nng truyn dn v tuyn ca LTE. Trong n ny cng trnh by chi tit qu trnh quy hoch mng LTE cng nh s dng phn mm Visual Basic cho vic m phng tnh ton quy hoch mng LTE.This thesis go to study an overview of LTE technology, with the requirements of LTE is defined as cost reduction compared to previous technologies, enhanced support for high-profit services and improve implementation maintenance and operation services, improve spectrum efficiency, user throughput, reduced latency. To achieve that end LTE using the important features such as OFDM technology transmission for uplink, SC-OFDM for downlink, MIMO technology for multi-antenna transceiver system, radio transmission rate high-bandwidth users. Combined with other technologies such as adaptive transmission and scheduling, delivery techniques, power control and HARQ. The new technology has been applied to wireless access for high performance wireless LTE transmission. In this thesis also present details the process of planning LTE networks as well as using Visual Basic software for the simulation LTE network planning.MC LC1CHNG 1 GII THIU V H THNG THNG TIN DI NG V TNG QUAN V MNG 4G

1.1 S pht trin ca h thng thng tin di ng11.1.1 H thng thng tin di ng th h 1 (1G)21.1.1.1 c im21.1.1.2 Nhng hn ch ca h thng thng tin di ng th h 121.1.2 H thng thng tin di ng th h 2 (2G)31.1.2.1 a truy cp phn chia theo thi gian TDMA31.1.2.2 a truy cp phn chia theo m CDMA41.1.3 H thng thng tin di ng th h 3 (3G)51.1.4 H thng thng tin di ng th h 4 (4G)71.2 Tng quan v mng 4G81.3 S khc nhau gia 3G v 4G111.3.1 u im ni bt111.3.2 Cc ng dng to nn u im ca 4G LTE so vi 3G111.4 Kt lun chng13CHNG 2 CU TRC MNG 4G LTE V CC VN LIN QUAN142.1 Gii thiu v cng ngh LTE142.2 Cu trc ca LTE232.3. Cc knh s dng trong E-UTRAN282.4 Giao thc ca LTE (LTE Protocols)302.5 Mt s c tnh ca knh truyn332.5.1 Tri tr a ng332.5.2 Cc loi fading332.5.2.1 Rayleigh fading332.5.2.2 Fading chn lc tn s v fading phng332.5.3 Dch tn Doppler342.5.4 Nhiu MAI i vi LTE342.6 Cc k thut s dng trong LTE352.6.1 K thut truy cp phn chia theo tn s trc giao OFDM [1]352.6.2 K thut SC-FDMA [1]452.6.3 K thut MIMO [1]472.6.4 M ha Turbo [10]502.6.5 Thch ng ng truyn [10]502.6.6 Lp biu ph thuc knh [10]512.6.7 HARQ vi kt hp mm [10]512.7 Chuyn giao522.7.1 Mc ch chuyn giao522.7.2 Trnh t chuyn giao532.7.3 Cc loi chuyn giao562.7.3.1 Chuyn giao mm v mm hn562.7.3.2 Chuyn giao cng572.7.4 Chuyn giao i vi LTE [3]582.8 iu khin cng sut602.9 Kt lun chng61CHNG 3 QUY HOCH MNG 4G LTE633.1 Gii thiu chng633.2 Gii thiu v nh c mng v tuyn633.3 Tin trnh nh c mng LTE673.3.1 u vo nh c mng LTE683.3.2 u ra nh c mng LTE693.3.3 Tin trnh nh c mng LTE703.4 Quy hoch vng ph733.4.1 Qu ng truyn733.4.1.1 Tnh ton qu ng ln cho LTE733.4.1.2 Tnh ton qu ng xung cho LTE753.4.1.3 V d v qu ng truyn763.4.2 Cc m hnh truyn sng803.4.2.1 M hnh Hata-Okumura813.4.2.2 M hnh Walfish-Ikegami823.4.3 Tnh bn knh cell843.5 Quy hoch dung lng [5]853.6 M phng903.6.1 Giao din chnh903.6.2 Form tnh qu ng truyn913.6.3 Quy hoch vng ph923.6.4 Quy hoch dung lng933.7 Kt lun chng94KT LUN V HNG PHT TRIN CA TI95TI LIU THAM KHO96

CHNG 1 GII THIU V H THNG THNG TIN DI NG V TNG QUAN V MNG 4GThng tin di ng l mt lnh vc rt quan trng trong i sng x hi. X hi cng pht trin, nhu cu v thng tin di ng ca con ngi cng tng ln v thng tin di ng cng khng nh c s cn thit v tnh tin dng ca n. Cho n nay, h thng thng tin di ng tri qua nhiu giai on pht trin, t th h di ng th h 1 n th h 3 v th h ang pht trin trn th gii - th h 4. Trong chng ny s trnh by khi qut v cc c tnh chung ca cc h thng thng tin di ng v tng quan v mng 4G.

1.1 S pht trin ca h thng thng tin di ng

Khi cc ngnh thng tin qung b bng v tuyn pht trin th tng v thit b in thoi v tuyn ra i v cng l tin thn ca mng thng tin di ng sau ny. Nm 1946, mng in thoi v tuyn u tin c th nghim ti ST Louis, bang Missouri ca M.

Sau nhng nm 50, vic pht minh ra cht bn dn cng nh hng ln n lnh vc thng tin di ng. ng dng cc linh kin bn dn vo thng tin di ng ci thin mt s nhc im m trc y cha lm c.

Thut ng thng tin di ng t bo ra i vo nhng nm 70, khi kt hp c cc vng ph sng ring l thnh cng, gii c bi ton kh v dung lng.

Hnh 1.1 L trnh pht trin ca h thng thng tin di ng t bo

1.1.1 H thng thng tin di ng th h 1 (1G)

Nhng h thng thng tin di ng u tin, nay c gi l th h th nht (1G), s dng cng ngh analog gi l a truy nhp phn chia theo tn s (FDMA) truyn knh thoi trn sng v tuyn n thu bao in thoi di ng. Vi FDMA, ngi dng c cp pht mt knh trong tp hp c trt t cc knh trong lnh vc tn s. Trong trng hp nu s thu bao nhiu vt tri so vi cc knh tn s c th, th mt s ngi b chn li khng c truy cp.

1.1.1.1 c im

Mi MS c cp pht i knh lin lc sut thi gian thng tuyn.

Nhiu giao thoa do tn s cc knh ln cn nhau l ng k.

Trm thu pht gc BTS phi c b thu pht ring lm vic vi mi MS trong cell.

H thng FDMA in hnh l h thng in thoi di ng tin tin AMPS.

1.1.1.2 Nhng hn ch ca h thng thng tin di ng th h 1

H thng di ng th h 1 s dng phng php a truy cp n gin. Tuy nhin h thng khng tha mn nhu cu ngy cng tng ca ngi dng v c dung lng v tc . N bao gm cc hn ch sau:

Phn b tn s rt hn ch, dung lng nh.

Ting n kh chu v nhiu xy ra khi my di ng chuyn dch trong mi trng fading a ng.

Khng cho php gim ng k gi thnh ca thit b di ng v c s h tng.

Khng m bo tnh b mt ca cc cuc gi.

Khng tng thch gia cc h thng khc nhau, c bit chu u, lm cho thu bao khng th s dng c my di ng ca mnh cc nc khc.

Cht lng thp v vng ph sng hp.

Gii php duy nht loi b cc hn ch trn l phi chuyn sang s dng k thut thng tin s cho thng tin di ng cng vi k thut a truy cp mi u im hn v c dung lng v cc dch v c cung cp. V vy xut hin h thng thng tin di ng th h 2. 1.1.2 H thng thng tin di ng th h 2 (2G)

H thng thng tin di ng s s dng k thut a truy cp phn chia theo thi gian (TDMA) u tin trn th gii c ra i chu u v c tn gi l GSM. Vi s pht trin nhanh chng ca thu bao, h thng thng tin di ng th h 2 lc p ng kp thi s lng ln cc thu bao di ng da trn cng ngh s. H thng 2G hp dn hn h thng 1G bi v ngoi dch v thoi truyn thng, h thng ny cn c kh nng cung cp mt s dch v truyn d liu v cc dch v b sung khc. Vit Nam, h thng thng tin di ng s GSM c a vo t nm 1993, hin nay ang c Cng ty VMS v GPC khai thc rt hiu qu vi hai mng thng tin di ng s VinaPhone v MobiFone theo tiu chun GSM.

Tt c h thng thng tin di ng th h 2 u s dng k thut iu ch s. V chng s dng 2 phng php a truy cp:

a truy cp phn chia theo thi gian (Time Division Multiple Access - TDMA): phc v cc cuc gi theo cc khe thi gian khc nhau.

a truy cp phn chia theo m (Code Division Multiple Access - CDMA): phc v cc cuc gi theo cc chui m khc nhau.

1.1.2.1 a truy cp phn chia theo thi gian TDMATrong h thng TDMA ph tn s quy nh cho lin lc di ng c chia thnh cc di tn lin lc, mi di tn lin lc ny c dng chung cho N knh lin lc, mi knh lin lc l mt khe thi gian (Time slot) trong chu k mt khung. Tin tc c t chc di dng gi, mi gi c bit ch th u gi, ch th cui gi, cc bit ng b v cc bit d liu. Khng nh h thng FDMA, h thng TDMA truyn dn d liu khng lin tc v ch s dng cho d liu s v iu ch s.

Cc c im ca TDMA: - TDMA c th phn pht thng tin theo hai phng php l phn nh trc v phn pht theo yu cu. Trong phng php phn nh trc, vic phn pht cc cm c nh trc hoc phn pht theo thi gian. Ngc li trong phng php phn nh theo yu cu cc mch c ti p ng khi c cuc gi yu cu, nh tng c hiu sut s dng mch.

- Trong TDMA cc knh c phn chia theo thi gian nn nhiu giao thoa gia cc knh k cn gim ng k.

- TDMA s dng mt knh v tuyn ghp nhiu lung thng tin thng qua vic phn chia theo thi gian nn cn phi c vic ng b ha vic truyn dn trnh trng lp tn hiu. Ngoi ra, v s lng knh ghp tng nn thi gian tr do truyn dn a ng khng th b qua c, do s ng b phi ti u.

1.1.2.2 a truy cp phn chia theo m CDMAi vi h thng CDMA, tt c ngi dng s s dng cng lc mt bng tn. Tn hiu truyn i s chim ton b bng tn ca h thng. Tuy nhin, cc tn hiu ca mi ngi dng c phn bit vi nhau bi cc chui m. Thng tin di ng CDMA s dng k thut tri ph cho nn nhiu ngi s dng c th chim cng knh v tuyn ng thi tin hnh cc cuc gi, m khng s gy nhiu ln nhau.

Knh v tuyn CDMA c dng li mi cell trong ton mng, v nhng knh ny cng c phn bit nhau nh m tri ph gi ngu nhin PN.

Trong h thng CDMA, tn hiu bn tin bng hp c nhn vi tn hiu bng thng rt rng, gi l tn hiu phn tn. Tn hiu phn tn l mt chui m gi ngu nhin m tc chip ca n rt ln so vi tc d liu. Tt c cc users trong mt h thng CDMA dng chung tn s sng mang v c th c pht ng thi. Mi user c mt t m gi ngu nhin ring ca n v n c xem l trc giao vi cc t m khc. Ti my thu, s c mt t m c trng c to ra tch sng tn hiu c t m gi ngu nhin tng quan vi n. Tt c cc m khc c xem nh l nhiu. khi phc li tn hiu thng tin, my thu cn phi bit t m dng my pht. Mi thu bao vn hnh mt cch c lp m khng cn bit cc thng tin ca my khc. c im ca CDMA: - Di tn tn hiu rng hng MHz.

- S dng k thut tri ph phc tp.

- K thut tri ph cho php tn hiu v tuyn s dng c cng trng rt nh v chng fading hiu qu hn FDMA, TDMA.

- Vic cc thu bao MS trong cell dng chung tn s khin cho thit b truyn dn v tuyn n gin, vic thay i k hoch tn s khng cn vn , chuyn giao tr thnh mm, iu khin dung lng cell rt linh hot.

- Cht lng thoi cao hn, dung lng h thng tng ng k (c th gp t 4 n 6 ln h thng GSM), an ton (tnh bo mt thng tin) cao hn do s dng dy m ngu nhin tri ph, khng nhiu tt hn, kh nng thu a ng tt hn, chuyn vng linh hot. Do h s ti s dng tn s l 1 nn khng cn phi quan tm n vn nhiu ng knh.

- CDMA khng c gii hn r rng v s ngi s dng nh TDMA v FDMA. Cn TDMA v FDMA th s ngi s dng l c nh, khng th tng thm khi tt c cc knh b chim.

- H thng CDMA ra i p ng nhu cu ngy cng ln dch v thng tin di ng t bo. y l h thng thng tin di ng bng hp vi tc bit thng tin ca ngi s dng l 8-13 kbps. 1.1.3 H thng thng tin di ng th h 3 (3G)

H thng thng tin di ng chuyn t th h 2 sang th h 3 qua mt giai on trung gian l th h 2, 5 s dng cng ngh TDMA trong kt hp nhiu khe hoc nhiu tn s hoc s dng cng ngh CDMA trong c th chng ln ph tn ca th h hai nu khng s dng ph tn mi, bao gm cc mng c a vo s dng nh: GPRS, EDGE v CDMA2000-1x. th h th 3 ny cc h thng thng tin di ng c xu th ho nhp thnh mt tiu chun duy nht v c kh nng phc v tc bit ln n 2 Mbit/s. phn bit vi cc h thng thng tin di ng bng hp hin nay, cc h thng thng tin di ng th h 3 gi l cc h thng thng tin di ng bng rng.

Nhiu tiu chun cho h thng thng tin di ng th h 3 IMT-2000 c xut, trong 2 h thng W-CDMA v CDMA2000 c ITU chp thun v a vo hot ng trong nhng nm u ca nhng thp k 2000. Cc h thng ny u s dng cng ngh CDMA, iu ny cho php thc hin tiu chun ton th gii cho giao din v tuyn ca h thng thng tin di ng th h 3.

W-CDMA (Wideband Code Division Multiple Access) l s nng cp ca cc h thng thng tin di ng th h 2 s dng cng ngh TDMA nh: GSM, IS-136.

CDMA2000 l s nng cp ca h thng thng tin di ng th h 2 s dng cng ngh CDMA: IS-95.

Yu cu i vi h thng thng tin di ng th h 3:Thng tin di ng th h th 3 xy dng trn c s IMT-2000 c a vo phc v t nm 2001. Mc ch ca IMT-2000 l a ra nhiu kh nng mi nhng

cng ng thi bo m s pht trin lin tc ca thng tin di ng th h 2.

Tc ca th h th ba c xc nh nh sau:

- 384 Kb/s i vi vng ph sng rng.

- 2 Mb/s i vi vng ph sng a phng. Cc tiu ch chung xy dng h thng thng tin di ng th h ba (3G):

- S dng di tn quy nh quc t 2GHz nh sau:

ng ln: 1885-2025 MHz.

ng xung: 2110-2200 MHz.

- L h thng thng tin di ng ton cu cho cc loi hnh thng tin v tuyn:

Tch hp cc mng thng tin hu tuyn v v tuyn.

Tng tc vi mi loi dch v vin thng.

- S dng cc mi trng khai thc khc nhau: trong cng s, ngoi ng, trn xe, v tinh.

- C th h tr cc dch v nh:

Mi trng thng tin nh o (VHE: Virtual Home Environment) trn c s mng thng minh, di ng c nhn v chuyn mng ton cu.

m bo chuyn mng quc t.

m bo cc dch v a phng tin ng thi cho thoi, s liu chuyn mch knh v s liu chuyn mch theo gi.

- D dng h tr cc dch v mi xut hin.

1.1.4 H thng thng tin di ng th h 4 (4G)

H thng thng tin di ng th h 3 sang th h 4 qua giai on trung gian l th h 3,5 c tn l mng truy nhp gi ng xung tc cao HSDPA. Th h 4 l cng ngh truyn thng khng dy th t, cho php truyn ti d liu vi tc ti a trong iu kin l tng ln ti 1 cho n 1.5 Gbps. Cng ngh 4G c hiu l chun tng lai ca cc thit b khng dy. Cc nghin cu u tin ca NTT DoCoMo cho bit, in thoi 4G c th nhn d liu vi tc 100 Mbps khi di chuyn v ti 1 Gbps khi ng yn, cho php ngi s dng c th ti v truyn ln hnh nh ng cht lng cao. Chun 4G cho php truyn cc ng dng phng tin truyn thng ph bin nht, gp phn to nn cc nhng ng dng mnh m cho cc mng khng dy ni b (WLAN) v cc ng dng khc.

Th h 4 dng k thut truyn ti truy cp phn chia theo tn s trc giao OFDM, l k thut nhiu tn hiu c gi i cng mt lc nhng trn nhng tn s khc nhau. Trong k thut OFDM, ch c mt thit b truyn tn hiu trn nhiu tn s c lp (t vi chc cho n vi ngn tn s). Thit b 4G s dng my thu v tuyn xc nhn bi phn mm SDR (Software - Defined Radio) cho php s dng bng thng hiu qu hn bng cch dng a knh ng thi. Tng i chuyn mch mng 4G ch dng chuyn mch gi, do , gim tr thi gian truyn v nhn d liu.

1.2 Tng quan v mng 4G

4G l h thng thng tin bng rng c xem nh IMT tin tin (IMT Advanced) c nh ngha bi ITU-R. Tc d liu ra l 100Mbps cho thu bao di chuyn cao v 1Mbps cho thu bao t di chuyn, bng thng linh ng ln n 40MHz. S dng hon ton trn nn IP, cung cp cc dch v nh in thoi IP, truy cp internet bng rng, cc dch v game v dng HDTV a phng tin

3GPP LTE c xem nh l tin 4G, nhng phin bn u tin ca LTE cha cc tnh nng theo yu cu ca IMT Advanced. LTE c tc l thuyt ln n 100Mbps ng xung v 50Mbps ng ln i vi bng thng 20MHz.

V s hn na nu s dng ng ten MIMO, cc anten mng c s dng. LTE c pht trin u tin hai th Stockholm v Olso vo ngy 14/12/2009. Giao din v tuyn vt l u tin c t tn l HSOPA (High Speed OFDM Packet Access), by gi c tn l E-UTRA (Evolved UMTS Terrestrial Radio Access). Thc t cho thy, hu ht cc hng sn xut thit b vin thng hng u th gii: Alcatel-Lucent, Ericsson, Motorola, Nokia, Nokia Siemens Networks, Huawei, LG Electronics, Samsung, NEC, Fujitsu... bt tay vi cc nh mng ln trn th gii (Verizon Wireless, AT&T, France Telecom-Orange, NTT DoCoMo, T-Mobile, China Mobile, ZTE. . .) thc hin cc cuc th nghim quan trng trn cng ngh LTE v t nhng thnh cng ng k. LTE Advanced l ng vin cho chun IMT-Advanced, mc tiu ca n l hng n p ng c yu cu ca ITU. LTE Advanced c kh nng tng thch vi thit b v chia s bng tn vi LTE phin bn u tin.

Di ng WiMAX (IEEE 802.16e-2005) l chun truy cp di ng khng dy bng rng (MWBA) cng c xem l 4G, tc bt nh ng xung l 128 Mbps v 56 Mbps cho ng xung vi rng bng thng hn 20 MHz.

UMB (Ultra Mobile Broadband): UMB c cc t chc vin thng ca Nht Bn, Trung Quc, Bc M v Hn Quc cng vi cc hng nh Alcatel-Lucent, Apple, Motorola, NEC v Verizon Wireless pht trin t nn tng CDMA. UMB c th hot ng bng tn c rng t 1,25 MHz n 20 MHz v lm vic nhiu di tn s, vi tc truyn d liu ln ti 288 Mbps cho lung xung v 75 Mbps cho lung ln vi rng bng tn s dng l 20 MHz. Qualcomm l hng i u trong n lc pht trin UMB, mc d hng ny cng ng thi pht trin c cng ngh LTE.

Mc tiu v cch tip cn:

4G cung cp QoS v tc pht trin hn nhiu so vi 3G ang tn ti, khng ch l truy cp bng rng, dch v tin nhn a phng tin (MMS), chat video, TV di ng m cn cc dch v HDTV, cc dch v ti thiu nh thoi, d liu v cc dch v khc. N cho php chuyn giao gia cc mng v tuyn trong khu vc cc b v c th kt ni vi h thng qung b video s.

Cc mc tiu m 4G hng n:

Bng thng linh hot gia 5 MHz n 20 MHz, c th ln n 40 MHz.

Tc c quy nh bi ITU l 100 Mbps khi di chuyn tc cao v 1 Gbps i vi thu bao ng yn so vi trm.

Tc d liu t nht l 100 Mbps gia bt k hai im no trn th gii.

Hiu sut ph ng truyn l 15bit/s/Hz ng xung v 6.75 bit/s/Hz ng ln (c ngha l 1000 Mbps ng xung v c th nh hn bng thng 67 MHz) Hiu sut s dng ph h thng ln n 3 bit/s/Hz/cell ng xung v 2.25 bit/s/Hz/cell cho vic s dng trong nh.

Chuyn giao lin (Smooth handoff) qua cc mng hn hp.

Kt ni lin v chuyn giao ton cu qua a mng.

Cht lng cao cho cc dch v a phng tin nh m thanh thi gian thc, tc d liu cao, video HDTV, TV di ng

Tng thch vi cc chun khng dy ang tn ti. Tt c l IP, mng chuyn mch gi khng cn chuyn mch knh na.

Cc im cn xt n:

Vng bao ph, mi trng v tuyn, ph, dch v, m hnh thng mi v s ngi s dng.

Cc k thut c s dng: K thut s dng lp vt l: Khng s dng CDMA MIMO: t c hiu sut ph tn cao bng cch s dng phn tp theo khng gian, a anten a ngi dng. S dng lng t ha trong min tn s, chng hn nh OFDM hoc SC-FDE (single carrier frequency domain equalization) ng xung: tn dng thuc tnh chn lc tn s ca knh m khng phi lng t phc tp. Ghp knh trong min tn s chng hn nh OFDMA hoc SC-FDMA ng xung: tc bit thay i bng vic gn cho ngi dng cc knh con khc nhau da trn iu kin knh. M ha sa li Turbo: ti thiu yu cu v t s SNR bn thu. Lp biu knh c lp: s dng cc knh thay i theo thi gian.

Thch nghi ng truyn: iu ch thch nghi v cc m sa li.

1.3 S khc nhau gia 3G v 4G

Hin nay, cng ngh 3G cho php truy cp Internet khng dy v cc cuc gi c hnh nh. 4G c pht trin trn cc thuc tnh k tha t cng ngh 3G. V mt l thuyt, mng khng dy s dng cng ngh 4G s c tc nhanh hn mng 3G t 4 n 10 ln. Tc ti a ca 3G l tc ti xung 14Mbps v 5.8Mbps ti ln. Vi cng ngh 4G, tc c th t ti 100Mbps i vi ngi dng di ng v 1Gbps i vi ngi dng c nh. 3G s dng cc di tn quy nh quc t cho UL: 1885 - 2025 MHz; DL: 2110 - 2200 MHz; vi tc t 144kbps - 2Mbps, rng BW: 5 MHz. i vi 4G LTE th Hot ng bng tn: 700 MHz - 2,6 GHz vi mc tiu tc d liu cao, tr thp, cng ngh truy cp sng v tuyn gi d liu ti u. Tc DL: 100Mbps ( BW 20MHz), UL: 50Mbps vi 2 aten thu mt anten pht. tr nh hn 5ms vi rng BW linh hot l u im ca LTE so vi WCDMA, BW t 1.25 MHz, 2.5 MHz, 5 MHz, 10 MHz, 15 MHz, 20 MHz. Hiu qu tri ph tng 4 ln v tng 10 ln s ngi dng/cell so vi WCDMA.

1.3.1 u im ni bt

Tc d liu cao hn rt nhiu ln so vi 3G. Tng hiu qu s dng ph v gim thi gian tr. Cu trc mng s n gin hn, v s khng cn chuyn mch knh. Hiu qu tri ph tng 4 ln v tng 10 ln user/cell so vi WCDMA.

rng bng tn linh hot cng l mt u im quan trng ca LTE i vi WCDMA.1.3.2 Cc ng dng to nn u im ca 4G LTE so vi 3G

Hiu sut ph cao:- OFDM DL

Chng nhiu a ng

Hu ht d liu ngi dng th t hn di ng

- SC-FDMA UL

PAPR thp

Ngi dng trc giao trong min tn s

- MIMO

Tc d liu cao:- Pht nhiu dng d liu c lp song song qua cc anten ring l => tng tc d liu (s dng MIMO). tr thp:- Thi gian ci t v thi gian tr hon chuyn tip ngn

- Tr HO v thi gian ngt ngn: TTI ngn, trng thi RRC n gin

Gi thnh r:- Cu trc mng n gin, gim cc thnh phn ca mng

Cht lng dch v cao:

- S dng cc tn s cp php m bo cht lng dch v: LTE s dng cc di tn s khc nhau : 2100 MHz, 1900 MHz, 1700 MHz, 2600 MHz, 900 MHz, 800 MHz.

- Lun lun th nghim (gim thi gian tr trong iu khin nh tuyn)

- Gim tr kh hi (round trip delay)

Tn s ti s dng linh hot:Gim nhiu lin cell vi tn s ti s dng ln hn 1.

- S dng hai di tn s:

Di 1: h s ti s dng ln hn 1 => cng sut pht cao hn

Di 2: ph cn li

- Cc user cnh cell: s dng di 1 => SIR tt

- Cc user trung tm cell: s dng ton b bng => tc d liu cao

Dung lng v vng bao ph ca WCDMA UL b gii hn bi can nhiu: can nhiu bn trong cell v can nhiu lin cell. Nhng i vi LTE th: do tnh trc giao nn can nhiu trong cng mt cell c th khng xt n v gim can nhiu inter-cell bng ti s dng cc b, thm cc anten c th trit can nhiu.

1.4 Kt lun chng

Chng 1 khi qut c nhng nt c trng, u nhc im v s pht trin ca cc h thng thng tin di ng th h 1, 2 v 3, 4 ng thi s lt tng quan ca h thng thng tin di ng th h 4. Hai thng s quan trng c trng cho cc h thng thng tin di ng s l tc bit thng tin ca ngi s dng v tnh di ng, cc th h tip theo cc thng s ny cng c ci thin. Nu c u im ca 4G so vi 3G v cc c s hnh thnh u im . tm hiu thm v 4G ta qua chng tip theo.CHNG 2 CU TRC MNG 4G LTE V CC VN LIN QUAN2.1 Gii thiu v cng ngh LTE

H thng 3GPP LTE, l bc tip theo cn hng ti ca h thng mng khng dy 3G da trn cng ngh di ng GSM/UMTS, v l mt trong nhng cng ngh tim nng nht cho truyn thng 4G. Lin minh Vin thng Quc t (ITU) nh ngha truyn thng di ng th h th 4 l IMT Advanced v chia thnh hai h thng dng cho di ng tc cao v di ng tc thp. 3GPP LTE l h thng dng cho di ng tc cao. Ngoi ra, y cn l cng ngh h thng tch hp u tin trn th gii ng dng c chun 3GPP LTE v cc chun dch v ng dng khc, do ngi s dng c th d dng thc hin cuc gi hoc truyn d liu gia cc mng LTE v cc mng GSM/GPRS hoc UMTS da trn WCDMA. Kin trc mng mi c thit k vi mc tiu cung cp lu lng chuyn mch gi vi dch v cht lng, tr ti thiu. H thng s dng bng thng linh hot nh vo m hnh a truy cp OFDMA v SC-FDMA. Thm vo , FDD v TDD, bn song cng FDD cho php cc UE c gi thnh thp. Khng ging nh FDD, bn song cng FDD khng yu cu pht v thu ti cng thi im. iu ny lm gim gi thnh cho b song cng trong UE. Truy cp tuyn ln da vo a truy cp phn chia theo tn s n sng mang (Single Carrier Frequency Division multiple Access SC-FDMA) cho php tng vng ph tuyn ln lm t s cng sut nh trn cng sut trung bnh thp (PAPR) so vi OFDMA. Thm vo , ci thin tc d liu nh, h thng LTE s dng hai n bn ln h s ph cell so vi h thng HSPA Release 6. ng c thc y: Cn th h tip theo ci thin cc nhc im ca 3G v p ng nhu cu ca ngi s dng Ngi dng i hi tc d liu v cht lng dch v cao hn Ti u h thng chuyn mch gi Tip tc nhu cu i hi ca ngi dng v gim gi thnh Gim phc tp Trnh s phn on khng cn thit cho hot ng ca mt cp hoc khng phi mt cp di thng Cc giai on pht trin ca LTE: Bt u nm 2004, d n LTE tp trung vo pht trin thm UTRAN v ti u cu trc truy cp v tuyn ca 3GPP.

Mc tiu hng n l 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 (100Mbps). Ti ln: gp 2 n 3 ln (50Mbps).

Nm 2007, LTE ca k thut truy cp v tuyn th h th 3 EUTRA- pht trin t nhng bc kh thi a ra cc c tnh k thut c chp nhn. Cui nm 2008 cc k thut ny c s dng trong thng mi.

Cc k thut OFDMA c s dng cho ng xung v SC-FDMA c s dng cho ng ln.

Mc tiu ca LTE: Tc d liu cao

tr thp

Cng ngh truy cp sng v tuyn gi d liu ti u

Cc c tnh c bn ca LTE: Hot ng bng tn: 700 MHz - 2,6 GHz.

Tc :

DL: 100Mbps ( BW 20MHz)

UL: 50 Mbps vi 2 aten thu mt anten pht.

tr: nh hn 5ms

rng BW linh hot: 1,4 MHz; 3 MHz; 5 MHz; 10 MHz; 15 MHz; 20 MHz. H tr c 2 trng hp di bng ln v bng xung bng nhau hoc khng.

Tnh di ng: Tc di chuyn ti u l 0-15 km/h nhng vn hot ng tt vi tc di chuyn t 15-120 km/h, c th ln n 500 km/h ty bng tn.

Ph tn s:

Hot ng ch FDD hoc TDD

ph sng t 5-100 km

Dung lng 200 user/cell bng tn 5Mhz.

Cht lng dch v:

H tr tnh nng m bo cht lng dch v QoS.

VoIP m bo cht lng m thanh tt, tr ti thiu thng qua mng UMTS.

Lin kt mng:

Kh nng lin kt vi cc h thng UTRAN/GERAN hin c v cc h thng khng thuc 3GPP cng s c m bo.

Thi gian tr trong vic truyn ti gia E-UTRAN v UTRAN/GERAN s nh hn 300ms cho cc dch v thi gian thc v 500ms cho cc dch v cn li.

Chi ph: chi ph trin khai v vn hnh gim

Bng thng linh hot trong vng t 1.4 MHz n 20 MHz, iu ny c ngha l n c th hot ng trong cc di bng tn ca 3GPP. Trong thc t, hiu sut thc s ca LTE ty thuc vo bng thng ch nh cho cc dch v v khng c s la chn cho ph tn ca chnh n. iu ny gip ng k cho cc nh khai thc trong chin lc v kinh t v k thut. Trin khai ti cc tn s cao, LTE l chin lc hp dn tp trung vo dung lng mng, trong khi ti cc tn s thp n c th cung cp vng bao ph khp ni. Mng LTE c th hot ng trong bt c di tn c s dng no ca 3GPP. N bao gm bng tn li ca IMT-2000 (1.9-2 GHz) v di m rng (2.5 GHz), cng nh ti 850-900 MHz, 1800 MHz, ph AWS (1.7-2.1 GHz)Bng tn ch nh di 5MHz c nh ngha bi IUT th ph hp vi dch v IMT trong khi cc bng tn ln hn 5MHz th s dng cho cc dch v c tc cc cao. Tnh linh hot v bng tn ca LTE c th cho php cc nh sn xut pht trin LTE trong nhng bng tn tn ti ca h.

Cc thng s lp vt l ca LTE:Bng 2.1 Cc thng s lp vt l LTE

K thut truy cpULDTFS-OFDM (SC-FDMA)

DLOFDMA

Bng thng1.4MHz, 3 MHz , 5 MHz, 10 MHz, 15 MHz, 20 MHz

TTI ti thiu1ms

Khong cch sng mang con15KHz

Chiu di CPNgn4.7s

Di16.7 s

iu chQPSK, 16QAM, 64QAM

Ghp knh khng gian1 lp cho UL/UE

Ln n 4 lp cho DL/UE

S dng MU-MIMO cho UL v DL

Bng 2.2 Tc nh ca LTE theo lp

Lp12345

Tc nh MbpsDL1050100150300

UL525505075

Dung lng cho cc chc nng lp vt l

Bng thng RF20MHz

iu chDLQPSK, 16QAM, 64QAM

ULQPSK, 16QAM, 64QAM

Dch v ca LTE:Qua vic kt ni ca ng truyn tc rt cao, bng thng linh hot, hiu sut s dng ph cao v gim thi gian tr gi, LTE ha hn s cung cp nhiu dch v a dng hn. i vi khch hng, s c thm nhiu ng dng v dng d liu ln, ti v v chia s video, nhc v ni dung a phng tin. Tt c cc dch v s cn lu lng ln hn p ng cht lng dch v, c bit l vi mong i ca ngi dng v ng truyn TV r nt cao. i vi khch hng l doanh nghip, truyn cc tp tin ln vi tc cao, cht lng video hi ngh ttLTE s mang c tnh ca Web 2.0 ngy nay vo khng gian di ng ln u tin. Dc theo s bo m v thng mi, n s bng qua nhng ng dng thi gian thc nh game a ngi chi v chia s tp tin.Bng 2.3 So snh cc dch v ca 3G so vi 4G LTE

Dch vMi trng (3G)Mi trng 4G

Thoai (rich voice)m thanh thi gian thcVoIP, video hi ngh cht lng cao

Tin nhn P2F(P2F messaging)SMS, MMS, cc email u tin thp Cc tin nhn photo, IM, email di ng, tin nhn video

Lt web(browsing)Truy cp n cc dch v online trc tuyn, Trnh duyt WAP thng qua GPRS v mng 3G. Duyt siu nhanh, ti cc ni dung ln cc mng x hi.

Thng tin cc ph(paid information)Ngi dng tr qua hoc trn mng tnh cc chun. Chnh yu l da trn thng tin vn bn.Tp ch trc tuyn, dng m thanh cht lng cao.

Ring t(personalization)Ch yu l m thanh chung, cng bao gm mn hnh ch v nhc ch.m thanh thc (thu m gc t ngi ngh s), cc trang web c nhn.

GamesTi v v chi game trc tuyn.Kinh nghim game trc tuyn vng chc qua c mng c nh v di ng.

Video/TV theo yu cu (video/TV on demand)Chy v c th ti video.Cc dch v qung b tivi, Tivi theo ng yu cu dng video cht lng cao.

NhcTi y cc track v cc dch v m thanh.Lu tr v ti nhc cht lng cao

Ni dung tin nhnTin nhn ng cp s dng ba thnh phn cng nh tng tc vi cc media khc.Phn phi t l rng ca cc video clip, dch v karaoke, video c bn qung co di ng.

M-comerce (thng mi qua in thoi)Thc hin cc giao dch v thanh ton qua mng di ng.in thoi cm tay nh thit b thanh ton, vi cc chi tit thanh ton qua mng tc cao cho php cc giao dch thc hin nhanh chng.

Mng d liu di ng(mobile data netwoking)Truy cp n cc mng ni b v c s d liu cng nh cch s dng ca cc ng dng nh CRM.Chuyn i file P2P, cc ng dng kinh doanh, ng dng chia s, thng tin M2M, di ng intranet/extranet.

So snh LTE vi HSPA v WiMAXBng 2.4 So snh gia HSPA, WiMAX v LTE

Cc tiu chHSUPAWiMAXLTE

Phin bn3GPP release 6802.16e (2005)3GPP release 8 (3/2009)

C s h tng v cc thit b c gi trBt u nm 2007Bt u nm 2007Bt u nm 2010

Di tn hot ng700MHz, 850 MHz,1.5GHz, 1.8 GHz, 1.7/2.1 GHz2.5GHz, 2.6GHz, 3.5GHz, 3.65 GHz, 5.8 GHz,700MHz, 850 MHz, 1.5 GHz, 1.8 GHz, 1.7/2.1 GHz, 2.1GHz, 2.3GHz, 2.6GHz

Cc thng s hng nTc d liu ln 5.6 Mbps i vi knh 5MHz, bn knh cell l 680mTc d liu ln 75Mbps/25 Mbps i vi knh 10MHz vi 2x2 MIMO, bn knh cell ln n 2-7Km, 100-200 ngi dngTc d liu ln 100Mbps/50 Mbps i vi knh 10MHz vi 2x2 MIMO, bn knh cell ln n 5Km, ln hn 400 ngi dng

Kh nng tng thch liTng thch li vi Release 99Khng tng thch li vi 3GPP hoc 3GPP2

K tha chun 3GPP, nhng khc k thut nn i hi thit b mi RAN nu di tn khc nhau c s dng

V cng ngh, LTE v WiMax c mt s khc bit nhng cng c nhiu im tng ng. C hai cng ngh u da trn nn tng IP. C hai u dng k thut MIMO ci thin cht lng truyn/nhn tn hiu, ng xung t trm thu pht n thit b u cui u c tng tc bng k thut OFDM h tr truyn ti d liu a phng tin v video.

ng ln t thit b u cui n trm thu pht c s khc nhau gia 2 cng ngh. WiMax dng OFDMA (Orthogonal Frequency Division Multiple Access mt bin th ca OFDM), cn LTE dng k thut SC-FDMA (Single Carrier - Frequency Division Multiple Access). V l thuyt, SC-FDMA c thit k lm vic hiu qu hn v cc thit b u cui tiu th nng lng thp hn OFDMA.

LTE cn c u th hn WiMax v c thit k tng thch vi c phng thc TDD (Time Division Duplex) v FDD (Frequency Division Duplex). Ngc li, WiMax hin ch tng thch vi TDDs. TDD truyn d liu ln v xung thng qua 1 knh tn s (dng phng thc phn chia thi gian), cn FDD cho php truyn d liu ln v xung thng qua 2 knh tn s ring bit. iu ny c ngha LTE c nhiu ph tn s dng hn WiMax. Tuy nhin, s khc bit cng ngh khng c ngha quyt nh trong cuc chin gia WiMax v LTE.

Trn th gii, 4G d cha phi ph bin song cng c quc gia v cc hng vin thng trin khai. Chng hn nh Ericsson. Thng 1/2009, Ericsson v nh mng ti Thy in trin khai thng mi TeliaSonera mng LTE/4G u tin ti Thy in. Ti thng 1/2010 trin khai din rng mng TeliaSonera trn ton quc Na Uy v Thy in. Ngoi ra, Ericsson k hp ng trin khai LTE trong thi gian ti vi cc nh mng AT&T (M), MetroPCS, Verizon Wireless (M), NTT Docomo (Nht). Ericsson cng tin hnh cc th nghim LTE/4G vi cc mng Telstra, SingTel, T-Mobile Hungary, Zain Saudia Arabia.

Vi Vit Nam, thi im ny, c quan qun l nh nc cha a ra quyt nh s i ln 4G bng Wimax hay LTE m quan im s t chc mt hi tho gia B vi cc doanh nghip tm ra s la chn hp l nht. Theo phn tch ca cc chuyn gia, hin ti Wimax c li th i trc LTE. Khng ch trn th gii m ngay c VitNam, mng Wimax c trin khai cung cp th nghim t nm 2004 ti gi. Cn LTE, li c cho rng phi ti khong nm 2012-2013 mi tr nn ph bin. Xong, so vi Wimax, LTE li c mt th mnh c cho l rt quan trng. LTE nu c trin khai cho php tn dng dng h tng GSM c sn d vn phi u t thm thit b. Cn Wimax, nu mun trin khai th phi xy dng t u mt mng mi. Vi VitNam, trong bi cnh hin nay, theo nhiu chuyn gia, vn cha n thi im chn mui pht trin 4G cho d l Wimax hay LTE. thi im ny, Vit Nam vn cha c k hoch trin khai 4G. Nu c, phi t nht l nm 2014. V vi mc thi gian ny, bit u, LTE li thng th hn Wimax? Nhng d c la chn cng ngh g i chng na, iu quan trng nht m ngi dng Vit t k vng cc nh khai thc mng, cung cp dch v l lm sao p ng c ba tiu chun. Mt chuyn gia ca Ericsson chia s. Th nht, l tnh thn thin v n gin ca dch v cng ngh cung cp. a s ngi dng trc y cha bit nhiu v Internet do tnh thn thin gip h s dng ln u tin m khng b nhm ln l iu rt quan trng. Th hai chnh l nhng ni dung ting Vit m h c th hng th t dch v.Vth ba, l gi c hp l. c bit l dch v tr trc. C th ni, a s ngi s dng khng hiu v s lin quan gia Megabyte v gi c nn chnh sch gi phi d hiu.

2.2 Cu trc ca LTE

Cu trc c bn SAE ca LTE

Hnh 2.1 So snh v cu trc gia UTMS v LTE

Hnh trn cho ta thy s khc nhau v cu trc ca UTMS v LTE. Song song vi truy nhp v tuyn LTE, mng gi li cng ang ci tin ln cu trc tng SAE. Cu trc mi ny c thit k ti u hiu sut mng, ci thin hiu qu chi ph v thun tin thu ht phn ln dch v trn nn IP.

Mng truy nhp v tuyn RAN (Radio Access Network): mng truy nhp v tuyn ca LTE c gi l E-UTRAN v mt trong nhng c im chnh ca n l tt c cc dch v, bao gm dch v thi gian thc, s c h tr qua nhng knh gi c chia s. Phng php ny s tng hiu sut ph, lm cho dung lng h thng tr nn cao hn. Mt kt qu quan trng ca vic s dng truy nhp gi cho tt c cc dch v l s tch hp cao hn gia nhng dch v a phng tin v gia nhng dch v c nh v khng dy.

C nhiu loi chc nng khc nhau trong mng t bo. Da vo chng, mng c th c chia thnh hai phn: mng truy nhp v tuyn v mng li. Nhng chc nng nh iu ch, nn, chuyn giao thuc v mng truy nhp. Cn nhng chc nng khc nh tnh cc hoc qun l di ng l thnh phn ca mng li. Vi LTE, mng truy nhp l E-UTRAN v mng li l EPC.

Mc ch chnh ca LTE l ti thiu ha s node. V vy, ngi pht trin chn mt cu trc n node. Trm gc mi phc tp hn NodeB trong mng truy nhp v tuyn WCDMA/HSPA, v v vy c gi l eNodeB (Enhance Node B). Nhng eNodeB c tt c nhng chc nng cn thit cho mng truy nhp v tuyn LTE, k c nhng chc nng lin quan n qun l ti nguyn v tuyn.

Giao din v tuyn s dng trong E-UTRAN by gi ch cn l S1 v X2. Trong S1 l giao din v tuyn kt ni gia eNodeB v mng li. S1 chia lm hai loi l S1-U l giao din gia eNodeB v SAE GW v S1 -MME l giao din gia eNodeB v MME. X2 l giao din gia cc eNodeB vi nhau.

Hnh 2.2 Cu trc c bn ca LTEMng li: mng li mi l s m rng hon ton ca mng li trong h thng 3G, v n ch bao ph min chuyn mch gi. V vy, n c mt ci tn mi: Evolved Packet Core (EPC).

Cng mt mc ch nh E-UTRAN, s node trong EPC c gim. EPC chia lung d liu ngi dng thnh mt phng ngi dng v mt phng iu khin. Mt node c th c nh ngha cho mi mt phng, cng vi Gateway chung kt ni mng LTE vi internet v nhng h thng khc. EPC gm c mt vi thc th chc nng.

MME (Mobility Management Entity): chu trch nhim x l nhng chc nng mt bng iu khin, lin quan n qun l thu bao v qun l phin.

Gateway dch v (Serving Gateway): l v tr kt ni ca giao tip d liu gi vi E-UTRAN. N cn hot ng nh mt node nh tuyn n nhng k thut 3GPP khc.

P-Gateway (Packet Data Network): l im u cui cho nhng phin hng v mng d liu gi bn ngoi. N cng l Router n mng Internet.

PCRF (Policyand Charging Rules Function): iu khin vic to ra bng gi v cu hnh h thng con a phng tin IP IMS (the IP Multimedia Subsystem) cho mi ngi dng.

HSS (Home Subscriber Server): l ni lu tr d liu ca thu bao cho tt c d liu ca ngi dng. N l c s d liu ch trung tm trong trung tm ca nh khai thc.

Cc min dch v bao gm IMS (IP Multimedia Sub-system) da trn cc nh khai thc, IMS khng da trn cc nh khai thc v cc dch v khc. IMS l mt kin trc mng nhm to s thun tin cho vic pht trin v phn phi cc dch v a phng tin n ngi dng, bt k l h ang kt ni thng qua mng truy nhp no. IMS h tr nhiu phng thc truy nhp nh GSM, UMTS, CDMA2000, truy nhp hu tuyn bng rng nh cp xDSL, cp quang, cp truyn hnh, cng nh truy nhp v tuyn bng rng WLAN, WiMAX. IMS to iu kin cho cc h thng mng khc nhau c th tng thch vi nhau. IMS ha hn mang li nhiu li ch cho c ngi dng ln nh cung cp dch v. N v ang c tp trung nghin cu cng nh thu ht c s quan tm ln ca gii cng nghip. Tuy nhin IMS cng gp phi nhng kh khn nht nh v cng cha tht s chn thuyt phc cc nh cung cp mng u t trin khai n. Kin trc IMS c cho l kh phc tp vi nhiu thc th v v s cc chc nng khc nhau.

IMS da trn cc nh khai thc: L IMS c tch hp sn trong cu trc ca h thng 3GPP

IMS khng da trn cc nh khai thc: L IMS khng c nh ngha trong cc chun. Cc nh khai thc c th tch hp dch v ny trong mng ca h. Cc UE kt ni n n qua vi giao thc c chp thun v dch v video streaming l 1 v d.

Cc dch khc khng c cung cp bi 3GPP v cu trc ph thuc vo yu cu ca dch v. Cu hnh in hnh s c UE kt ni n my ch qua mng chng hn nh kt ni n trang ch cho dch v lt web.

Cu trc ca LTE lin kt vi cc mng khc:

Hnh 2.3 Cu trc h thng cho mng truy cp 3GPP

Hnh 2.4 Cu trc h thng cho mng truy cp 3GPP v khng phi 3GPP

Hnh 2.5 Cu trc h thng cho mng truy cp3GPP v lin mng vi CDMA 2000

H thng 3GPP hin ti (GSM v WCDMA/HSPA) v 3GPP2 (CDMA2000 1xRTT, EV-DO) c kt hp vo h thng mi thng qua nhng giao din chun ha, min l ti u tnh di ng vi LTE. Vi h thng 3GPP, iu ny c ngha l mt giao din bo hiu gia SGSN (Serving GPRS Support Node) v mng li mi, vi h thng 3GPP2 cng c mt giao din bo hiu gia CDMA RAN v mng li mi.

V d tn hiu iu khin cho di ng c x l bi node Mobility Management Entity (MME), tch ri vi Gateway. iu ny thun tin cho vic ti u trong trin khai mng v hon ton cho php chia t l dung lng mt cch linh ng. Home Subscriber Server (HSS) ni n Packet Core qua mt giao din IP, v khng phi SS7 nh s dng trong mng GSM v WCDMA. Mng bo hiu cho iu khin chnh sch v tnh cc c da trn giao din IP. H thng GSM v WCDMA/HSPA hin ti c tch hp vo h thng mi qua nhng giao din c chun ha gia SGSN v mng li mi. Ngi ta c gng kt hp truy nhp CDMA cng s a n tnh di ng lin tc gia LTE v CDMA, cho php s mm do trong vic chuyn ln LTE.

LTE-SAE tip nhn khi nim QoS theo tng lp. iu ny cung cp mt gii php n gin v n by gi vn hiu qu cho nhng nh khai thc c c s phn bit gia nhng dch v gi.

2.3 Cc knh s dng trong E-UTRAN

Knh vt l: cc knh vt l s dng cho d liu ngi dng bao gm: PDSCH (Physical Downlink Shared Channel): ph ti c ch (payload)

PUSCH (Physical Uplink Shared Channel): PUSCH c dng mang d liu ngi dng. Cc ti nguyn cho PUSCH c ch nh trn mt subframe c bn bi vic lp biu ng ln. Cc sng mang c ch nh l 12 khi ti nguyn (RB) v c th nhy t subframe ny n subframe khc. PUSCH c th dng cc kiu iu ch QPSK, 16QAM, 64QAM.

PUCCH (Physical Uplink Control Channel): c chc nng lp biu, ACK/NAK. PDCCH (Physical Downlink Control Channel): lp biu, ACK/NAK. PBCH (Physical Broadcast Channel): mang cc thng tin c trng ca cell.

Knh logic: c nh ngha bi thng tin n mang bao gm: Knh iu khin qung b (BCCH): c s dng truyn thng tin iu khin h thng t mng n tt c my di ng trong cell. Trc khi truy nhp h thng, u cui di ng phi c thng tin pht trn BCCH bit c h thng c lp cu hnh nh th no, chng hn bng thng h thng. Knh iu khin tm gi (PCCH): c s dng tm gi cc u cui di ng v mng khng th bit c v tr ca chng cp v v th cn pht cc bn tin tm gi trong nhiu (vng nh v). Knh iu khin ring (DCCH): c s dng truyn thng tin iu khin ti/t mt u cui di ng. Knh ny c s dng cho cu hnh ring ca cc u cui di ng chng hn cc bn tin chuyn giao khc nhau. Knh iu khin a phng (MCCH): c s dng truyn thng tin cn thit thu knh MTCH. Knh lu lng ring (DTCH): c s dng truyn s liu ca ngi s dng n/t mt u cui di ng. y l kiu logic c s dng truyn tt c s liu ng ln ca ngi dng v s liu ng xung ca ngi dng khng phi MBMS. Knh lu lng a phng (MTCH): c s dng pht cc dch v MBMS. Knh truyn ti: Bao gm cc knh sau: Knh qung b (BCH): c khun dng truyn ti c nh do chun cung cp. N c s dng pht thng tin trn knh logic. Knh tm gi (PCH): c s dng pht thng tin tm gi trn knh PCCH, PCH h tr thu khng lin tc (DRX) cho php u cui tit kim cng sut c quy bng cch ng v ch thc thu PCH ti cc thi im quy nh trc. Knh chia s ng xung (DL-SCH): l knh truyn ti pht s liu ng xung trong LTE. N h tr cc chc nng ca LTE nh thch ng tc ng v lp biu ph thuc knh trong min thi gian v min tn s. N cng h tr DRX gim tiu th cng sut ca u cui di ng m vn m bo cm gic lun kt ni ging nh c ch CPC trong HSPA. DL-DCH TTI l 1ms. Knh a phng (MCH): c s dng h tr MBMS. N c c trng bi khun dng truyn ti bn tnh v lp biu bn tnh. Trong trng hp pht a s dng MBSFN, lp biu v lp cu hnh khun dng truyn ti c iu phi gia cc tham gia pht MBSFN. 2.4 Giao thc ca LTE (LTE Protocols)

LTE chc nng ca RLC c chuyn vo eNodeB, cng nh chc nng ca PDCP vi m ha v chn tiu . V vy, cc giao thc lin quan ca lp v tuyn c chia trc y UTRAN l gia NodeB v RNC by gi chuyn thnh gia UE v eNodeB.

Hnh 2.6 Giao thc ca UTRAN

Hnh 2.7 Giao thc ca E-UTRAN

Giao thc ca E-UTRAN pht trin thm ca UTRAN bng cch thm L1 v MAC mi.

Hnh 2.8 Phn phi chc nng ca cc lp MAC, RLC, PDCP

Chc nng ca MAC (Medium Access Control) bao gm:

Lp biu

iu khin u tin (Priority handling)

Ghp nhiu knh logic khc nhau trn mt knh truyn n RLC, cng nh trong WCDMA c chc nng sau:

Truyn li trong trng hp giao nhn cc lp thp (MAC v L1) b hng, tng t trong trng hp ch ACK ca RLC UTRAN

Phn on ph hp cho cc giao thc n v d liu

Cung cp cc knh vt l cho cc lp cao hn

Chc nng ca PDCP bao gm:

M ha (ciphering)

Chn tiu

Trong sut nm 2006, PDCP vn c gi s trong mng li, nhng quyt nh hin ti l a PDCP vo eNodeB bao gm m ha. iu ny lm cho chc nng v tuyn ca LTE tng t nh ca HPSA ci tin.

Trong giao din iu khin, chc nng ca giao thc RRC th cng ging nh bn UTRAN. Giao thc RRC cu hnh cc thng s kt ni, iu khin bo co o lng thit b u cui, cc lnh chuyn giaoM ASN1 c s dng cho RRC ca LTE, n dn cch s khc bit gia cc phin bn ng tng thch li. Giao thc RRC s bao gm t trng thi hn EUTRAN. Ch c trng thi tch cc hay ri c d on bi v c tnh linh ng ca s phn b ngun ti nguyn. Cc trng thi ca RRC trong LTE l:

RRC - ri: thit b s quan st bn tin paging v s dng cell cho di ng. Khng c RRC no lu tr trong bt k eNodeB c nhn no. UE ch c duy nht mt ID nhn dng n trong vng di chuyn.

RRC - kt ni: bit v tr ca UE cell no v d liu c pht v nhn.

Kt ni RRC tn ti n mt eNodeB. iu khin chuyn giao bi mng c s dng cho di ng.

2.5 Mt s c tnh ca knh truyn

Ta tm hiu mt s c tnh ca knh truyn nh hng n vic truyn tn hiu, cc c tnh ny bao gm tri tr, fading, dch tn Doppler, nh hng ca dch tn Doppler i vi tn hiu OFDM, nhiu MAI, v cch khc phc nhiu MAI.

2.5.1 Tri tr a ng

Tn hiu nhn c ni thu gm tn hiu thu trc tip v cc thnh phn phn x. Tn hiu phn x n sau tn hiu thu trc tip v n phi truyn qua mt khong di hn, v nh vy n s lm nng lng thu c tri rng theo thi gian. Khong tri tr (delay spread) c nh ngha l khong chnh lch thi gian gia tn hiu thu trc tip v tn hiu phn x thu c cui cng. Trong thng tin v tuyn, tri tr c th gy nn nhiu xuyn k t nu nh h thng khng c cch khc phc. i vi LTE, s dng k thut OFDM trnh c nhiu xuyn k t ISI.2.5.2 Cc loi fading

Fading l s bin i cng tn hiu sng mang cao tn ti anten thu do c s thay i khng ng u v ch s khc x ca kh quyn, cc phn x ca t v nc trn ng truyn sng v tuyn i qua.

2.5.2.1 Rayleigh fading

Fadinh Rayleigh l loi Fading sinh ra do hin tng a ng (Multipath Signal) v xc sut mc tn hiu thu b suy gim so vi mc tn hiu pht i tun theo phn b Rayleigh.

2.5.2.2 Fading chn lc tn s v fading phng

Bng thng kt hp: l mt php o thng k ca di tn s m knh xem nh l phng.

Nu tri tr thi gian a ng l D(s) th bng thng kt hp Wc(Hz) xp x bng:

Trong fading phng, bng thng kt hp ca knh ln hn bng thng ca tn hiu. V vy, s lm thay i u tn hiu sng mang trong mt di tn s.

Trong fading chn lc tn s, bng thng kt hp ca knh nh hn bng thng ca tn hiu. V vy, s lm thay i tn hiu sng mang vi mc thay i ph thuc tn s.2.5.3 Dch tn Doppler

H thng truyn v tuyn chu s tc ng ca dch tn Doppler. Dch tn Doppler l hin tng m tn s thu c khng bng tn s ca ngun pht do s chuyn ng tng i gia ngun pht v ngun thu. C th l: khi ngun pht v ngun thu chuyn ng hng vo nhau th tn s thu c s ln hn tn s pht i, khi ngun pht v ngun thu chuyn ng ra xa nhau th tn s thu c s gim i. Khong tn s dch chuyn trong hin tng Doppler tnh theo cng thc sau :

(2.1)

Trong l khong tn s dch chuyn, f0 l tn s ca ngun pht, v l vn tc tng i gia ngun pht v ngun thu, c l vn tc nh sng. i vi LTE, khc phc hin tng dch tn Doppler, ngi ta chn khong cch gia cc sng mang ln (f = 15 Khz).

2.5.4 Nhiu MAI i vi LTE

i vi LTE, ng ln s dng k thut SC-FDMA, n cng nhy cm vi dch tn. Cc user khc nhau lun c dch tn s sng mang CFO (Carrier Frequency Offset). Khi tn ti nhiu CFO, tnh trc giao gia cc sng mang b mt. Nhiu lin sng mang (ICI: Inter Carrier Interference) v MAI (Multi Access Interference) to ra lm gim cht lng ca tn hiu thu c. Mt phng php trit ICI cng nh MAI, l da trn cc k hiu hoa tiu khi (block type pilots).

Cc user khc nhau giao tip vi trm gc ti cc khe thi gian khc nhau. Phng php ny ly trc tip thnh phn nhiu bng cch li dng cc k hiu hoa tiu khi, v vy n khng cn s dng c lng CFO nhiu ln. Sau , ma trn can nhiu c th c khi phc li v nh hng ca cc CFO c th c trit d dng bng cch s dng phng php o ma trn.2.6 Cc k thut s dng trong LTE

LTE s dng k thut OFDMA cho truy cp ng xung v SC-FDMA cho truy cp ng ln. Kt hp ng thi vi MIMO, cc k thut v lp biu, thch ng ng truyn v yu cu t ng pht li lai ghp.

2.6.1 K thut truy cp phn chia theo tn s trc giao OFDM [1]

Hnh 2.9 Truyn n sng mang

Hnh 2.10 Nguyn l ca FDMA

Hnh 2.11 Nguyn l a sng mang

K thut iu ch OFDM, v c bn, l mt trng hp c bit ca phng php iu ch FDM, chia lung d liu thnh nhiu ng truyn bng hp trong vng tn s s dng, trong cc sng mang con (hay sng mang ph, sub-carrier) trc giao vi nhau. Do vy, ph tn hiu ca cc sng mang ph ny c php chng ln ln nhau m pha u thu vn khi phc li c tn hiu ban u. S chng ln ph tn hiu ny lm cho h thng OFDM c hiu sut s dng ph ln hn nhiu so vi cc k thut iu ch thng thng.

Hnh 2.12 So snh ph tn ca OFDM vi FDMA

Hnh 2.13 Tn s-thi gian ca tn hiu OFDM

LTE s dng OFDM trong k thut truy cp ng xung v n c cc u im sau:

OFDM c th loi b hin tng nhiu xuyn k hiu ISI (Inter-Symbol Interference) nu di chui bo v (guard interval) ln hn tr truyn dn ln nht ca knh truyn.

Thc hin vic chuyn i chui d liu t ni tip sang song song nn thi gian symbol tng ln do s phn tn theo thi gian gy bi tri tr do truyn dn a ng gim xung.

Ti u hiu qu ph tn do cho php chng ph gia cc sng mang con. Hn ch c nh hng ca fading bng cch chia knh fading chn lc tn s thnh cc knh con phng tng ng vi cc tn s sng mang OFDM khc nhau.

OFDM ph hp cho vic thit k h thng truyn dn bng rng (h thng c tc truyn dn cao), nh hng ca s phn tp v tn s (frequency selectivity) i vi cht lng h thng c gim thiu nhiu so vi h thng truyn dn n sng mang.

Cu trc my thu n gin.

Thch ng ng truyn v lp biu trong min tn s.

Tng thch vi cc b thu v cc anten tin tin.

Hnh 2.14 Cc sng mang trc giao vi nhau

Mt vn gp phi OFDM trong cc h thng thng tin di ng l cn dch cc tn s tham kho i vi cc u cui pht ng thi. Dch tn ph hng tnh trc giao ca cc cuc truyn dn n nhiu a truy nhp. V vy n rt nhy cm vi dch tn. LTE chn khong cch gia cc sng mang l 15KHz, i vi khong cch ny l khong cch ln i vi dch tn Doppler.

iu ch tn hiu OFDM s dng bin i FFT v IFFT cho bin i gia min thi gian v min tn s.

Hnh 2.15 Bin i FFT

Chiu di bin i FFT l 2n vi n l s nguyn. Vi LTE chiu di c th l 512 hoc 1024...Ta s dng bin i IFFT khi pht i, ngun d liu sau khi iu ch c chuyn i t ni tip sang song song. Sau c a n b bin i IFFT. Mi ng vo ca IFFT tng ng vi tng sng mang con ring bit (thnh phn tn s ring bit ca tn hiu min thi gian) v mi sng mang c iu ch c lp vi cc sng mang khc. Sau khi c bin i IFFT xong, tn hiu c chn thm tin t vng (CP) v pht i. b thu ta lm ngc li.

Hnh 2.16 Thu pht OFDM

Mc ch ca vic chn thm tin t vng l c kh nng lm gim hay loi tr nhiu xuyn k hiu ISI (Inter Symbol Interference). Mt mu tn hiu c di l TS, chui bo v tng ng l mt chui tn hiu c di TG pha sau c sao chp ln phn pha trc ca mu tn hiu nh hnh v sau:

Hnh 2.17 Chui bo v GIDo , GI cn c gi l Cyclic Prefix (CP). S sao chp ny c tc dng chng li nhiu xuyn k hiu ISI do hiu ng phn tp a ng.Nguyn tc ny gii thch nh sau: Gi s my pht i mt khong tn hiu c chiu di l Ts, sau khi chn thm chui bo v c chiu di TG th tn hiu ny c chiu di l T = TS+TG. Do hiu ng a ng multipath, tn hiu ny s ti my thu theo nhiu ng khc nhau. Trong hnh v, hnh a, tn hiu theo ng th nht khng c tr, cc ng th hai v th ba u b tr mt khong thi gian so vi ng th nht. Tn hiu thu c my thu s l tng hp ca tt c cc tuyn, cho thy k hiu ng trc s chng ln vo k hiu ngay sau , y chnh l hin tng ISI. Do trong OFDM c s dng chui bo v c di TG s d dng loi b hin tng ny. Trong trng hp TG MAX nh hnh v m t th phn b chng ln ISI nm trong khong ca chui bo v, cn thnh phn tn hiu c ch vn an ton. pha my thu s loi b chui bo v trc khi gi tn hiu n b gii iu ch OFDM. Do , iu kin cn thit cho h thng OFDM khng b nh hng bi ISI l:TG MAX vi MAX l tr truyn dn ti a ca knh.

a) Khng c GI

b) C GI

Hnh 2.18 Tc dng ca chui bo v

OFDM lng t ha trong min tn s da trn c lng p ng tn s ca knh. Do n hot ng n gin hn WCDMA v n khng ph thuc vo chiu di ca knh (chiu di ca a ng trong cc chip) nh khi lng t WCDMA. Trong WCDMA cc cell khc nhau c phn bit bi cc m tri ph khc nhau nhng trong OFDM tri ph khng c gi tr, n s dng cc k hiu tham kho ring bit gia cc cell hoc gia cc anten khc nhau.

LTE s dng OFDMA (Orthogonal Frequency Division Multiple Access) cho tuyn ln. OFDMA gi l a truy nhp phn chia theo tn s trc giao l cng ngh a truy cp phn chia theo sng mang, l mt dng nng cao, l phin bn a ngi dng ca m hnh iu ch s OFDM

K thut a truy nhp ca OFDMA cho php nhiu ngi dng cng truy cp vo mt knh truyn bng cch phn chia mt nhm cc sng mang con (subcarrier) cho mt ngi dng ti mt thi im. cc thi im khc nhau, nhm sng mang con cho 1 ngi dng cng khc nhau. iu ny cho php truyn d liu tc thp t nhiu ngi s dng.

Hnh 2.19 Sng mang con OFDMA

Hnh 2.20 OFDM v OFDMA

Ti nguyn thi gian - tn s c chia nh theo cu trc sau: 1 radio frame c chiu di l 10ms, trong chia thnh nhiu subframe nh c chiu di l 1ms, v mi subframe nh li c chia thnh 2 slot vi chiu di ca mi slot l 0.5ms. Mi slot s bao gm 7 k t OFDM trong trng hp chiu di CP thng thng v 6 k t OFDM trong trng hp CP m rng.

Trong OFDMA, vic ch nh s sng mang con cho ngi dng khng da vo tng sng mang con ring l m da vo cc khi ti nguyn (Resource Block). Mi khi ti nguyn bao gm 12 sng mang con cho khong thi gian 1 slot v khong cch gia cc sng mang con l 15KHz dn n kt qu bng thng ti thiu ca n l 180 KHz. n v nh nht ca ti nguyn l thnh phn ti nguyn (RE), n bao gm mt sng mang con i vi khong thi gian ca mt k t OFDM. Mt RB bao gm 84 RE (tc 7 x12) trong trng hp chiu di CP thng thng v 72 RE (6x12) trong trng hp chiu di CP m rng.

Hnh 2.21 Ch nh ti nguyn ca OFDMA trong LTE

Bng 2.5 S khi ti nguyn theo bng thng knh truyn

Bng thng knh truyn (MHz)1.435101520

S khi ti nguyn615255075100

Hnh 2.22 Cu trc ca mt khi ti nguyn

Tn hiu tham kho (RS): LTE s dng cc tn hiu tham kho c bit d dng c lng dch sng mang, c lng knh truyn, ng b thi gianCc tn hiu tham kho c b tr nh hnh sau:

Hnh 2.23 Cu trc b tr tn hiu tham kho

Cc tn hiu tham kho ny c pht k t OFDM th nht v th nm ca mi slot v sng mang th su ca mi subframe. Tn hiu tham kho cng c s dng c lng tn hao ng truyn s dng cng sut thu tn hiu tham kho (RSRP).

Nhc im ca OFDM l g? Ta xt cc hnh sau:

Hnh 2.24 c tnh ng bao ca tn hiu OFDM

Hnh 2.25 PAPR cho cc tn hiu khc nhau

T cc hnh trn ta thy, dng sng OFDM th hin s thng ging ng bao rt ln dn n PAPR cao. Tn hiu vi PAPR cao i hi cc b khuch i cng sut c tnh tuyn tnh cao trnh lm mo dng tn hiu. t c mc tuyn tnh ny, b khuch i phi lm vic ch cng tc vi li (so vi im bo ha cao). iu ny dn n hiu sut s dng cng sut (t s cng sut pht vi cng sut tiu th mt chiu) thp v th c bit nh hng i vi cc thit b cm tay. khc phc nhc im ny, 3GPP nghin cu s dng phng php a truy nhp ng ln s dng DTFS-OFDM vi tn gi l SC-FDMA v p dng cho LTE.

2.6.2 K thut SC-FDMA [1]

Cc tn hiu SC-FDMA c tn hiu PAPR tt hn OFDMA. y l mt trong nhng l do chnh chn SC-FDMA cho LTE. PAPR gip mang li hiu qu cao trong vic thit k cc b khuch i cng sut UE, v vic x l tn hiu ca SC-FDMA vn c mt s im tng ng vi OFDMA, do , tham s hng DL v UL c th cn i vi nhau. Ging nh trong OFDMA, cc my pht trong h thng SC-FDMA cng s dng cc tn s trc giao khc nhau pht i cc k hiu thng tin. Tuy nhin cc k hiu ny pht i ln lt ch khng phi song song nh trong OFDMA. V th, cch sp xp ny lm gim ng k s thng ging ca ng bao tn hiu ca dng sng pht. V th cc tn hiu SC-FDMA c PAPR thp hn cc tn hiu OFDMA. Tuy nhin trong cc h thng thng tin di ng b nh hng ca truyn dn a ng, SC-FDMA c thu ti cc BTS b nhiu gia cc k t kh ln. BTS s dng b cn bng thch ng min tn s loi b nhiu ny.

Hnh 2.26 OFDMA v SC-FDMA

Hnh trn cho thy s khc nhau trong qu trnh truyn cc k hiu s liu theo thi gian. Trn hnh ny ta coi mi ngi s dng c phn thnh 4 sng mang con (P = 4) vi bng thng con bng 15KHz, trong mi k hiu OFDMA hoc SC-FDMA truyn 4 k hiu s liu c iu ch QPSK cho mi ngi s dng. i vi OFDMA 4 k hiu s liu ny c truyn dng thi vi bng tn con cho mi k hiu l 15KHz trong mi khong thi gian hiu dng TFFT ca mt k hiu OFDMA, trong khi i vi SC-FDMA, 4 k hiu s liu ny c truyn ln lt trong khong thi gian bng 1/P (P = 4) thi gian hiu dng k hiu SC-FDMA vi bng tn con bng P x 15KHz (4 x 15 KHz) cho mi k hiu.

Trong OFDM, bin i Fourier nhanh FFT dng bn thu cho mi khi k t, v o FFT bn pht. Cn SC-FDMA s dng c hai thut ton ny c bn pht v bn thu.

Hnh 2.27 Thu pht SC-FDMA trong min tn s

2.6.3 K thut MIMO [1]

MIMO l mt phn tt yu ca LTE t c cc yu cu y tham vng v thng lng v hiu qu s dng ph. MIMO cho php s dng nhiu anten my pht v my thu. Vi hng DL, MIMO 2x2 (2 anten thit b pht, 2 anten thit b thu) c xem l cu hnh c bn, v MIMO 4x4 cng c cp v a vo bng c t k thut chi tit. Hiu nng t c ty thuc vo vic s dng MIMO. Trong , k thut ghp knh khng gian (spatial multiplexing) v pht phn tp (transmit diversity) l cc c tnh ni bt ca MIMO trong cng ngh LTE.

Gii hn chnh ca knh truyn thng tin l can nhiu a ng gii hn v dung lng theo quy lut Shannon. MIMO li dng tn hiu a ng gia my pht v my thu ci thin dung lng c sn cho bi knh truyn. Bng cch s dng nhiu anten bn pht v thu vi vic x l tn hiu s, k thut MIMO c th to ra cc dng d liu trn cng mt knh truyn, t lm tng dung lng knh truyn.

Hnh 2.28 M hnh SU-MIMO v MU-MIMO

Hnh trn l v d v SU-MIMO 2x2 v MU-MIMO 2x2. SU-MIMO y hai dng d liu trn vi nhau (m ha) ph hp vi knh truyn nht. 2x2 SU-MIMO thng dng trong tuyn xung. Trong trng hp ny dung lng cell tng v tc d liu tng. MU-MIMO 2x2 y dng d liu MIMO a ngi dng n t cc UE khc nhau. Dung lng cell tng nhng tc d liu khng tng. u im chnh ca MU-MIMO so vi SU-MIMO l dung lng cell tng m khng tng gi thnh v pin ca hai my pht UE. MU-MIMO phc tp hn SU-MIMO.Trong h thng MIMO, b pht gi cc dng d liu qua cc anten pht. Cc dng d liu pht thng qua ma trn knh truyn bao gm nhiu ng truyn gia cc anten pht v cc anten thu. Sau b thu nhn cc vector tn hiu t cc anten thu, gii m thnh thng tin gc. i vi tuyn xung, cu hnh hai anten trm pht v hai anten thu thit b u cui di ng l cu hnh c bn, cu hnh s dng bn anten ang c xem xt. y chnh l cu hnh SU-MIMO, v s dng k thut ghp knh khng gian vi li th hn cc k thut khc l trong cng iu kin v bng thng s dng v k thut iu ch tn hiu, SU cho php tng tc d liu (data rate) bng s ln ca s lng anten pht.

Ghp knh khng gian cho php pht chui bit d liu khc nhau trn cng mt khi ti nguyn tuyn xung. Nhng dng d liu ny c th l mt ngi dng (SU-MIMO) hoc nhng ngi dng khc nhau (MU-MIMO). Trong khi SU-MIMO tng tc d liu cho mt ngi dng, MU-MIMO cho php tng dung lng. Da vo hnh 2.29, ghp knh khng gian li dng cc hng khng gian ca knh truyn v tuyn cho php pht cc d liu khc nhau trn hai anten.

Hnh 2.29 Ghp knh khng gian

K thut phn tp c bit n t WCDMA release 99 v cng s l mt phn ca LTE. Thng thng, tn hiu trc khi pht c m ha tng hiu ng phn tp. MIMO c s dng khai thc vic phn tp v mc tiu l lm tng tc . Vic chuyn i gia MIMO truyn phn tp v ghp knh khng gian c th ty thuc vo vic s dng knh tn s.

i vi ng ln, t thit b u cui di ng n BS, ngi ta s dng m hnh MU-MIMO (Multi-User MIMO). S dng m hnh ny BS yu cu s dng nhiu anten, cn thit b di ng ch dng mt anten gim chi ph cho thit b di ng. V hot ng, nhiu thit b u cui di ng c th pht lin tc trn cng mt knh truyn, nhiu knh truyn, nhng khng gy ra can nhiu vi nhau bi v cc tn hiu hoa tiu (pilot) trc giao ln nhau. K thut c cp n, l k thut a truy nhp min khng gian (SDMA) hay cn gi l MIMO o.

2.6.4 M ha Turbo [10]

sa nhng bit b li do s thay i knh v nhiu, m ha knh c s dng. Vi knh chia s hng xung ca LTE (DL-SCH), s dng mt b m ha Turbo vi tc 1/3, theo sau l mt b so khp tc thch ng vi tc m. Trong mi khung con chiu di 1ms, mt hoc hai t m c th c m ha v truyn i.

2.6.5 Thch ng ng truyn [10]

Thch ng ng truyn gii quyt vn lin quan n cch thit lp cc thng s truyn dn ca ng truyn v tuyn x l cc thay i cht lng ng truyn v tuyn. N s dng iu ch thch nghi (Adaptive Modulation). Phng php ny cho php h thng iu chnh nguyn l iu ch tn hiu theo t l tn hiu trn nhiu (SNR) ca ng truyn v tuyn. Khi ng truyn v tuyn c cht lng cao, nguyn l iu ch cao nht c s dng lm tng thm dung lng h thng. Trong qu trnh suy gim tn hiu, h thng LTE c th chuyn sang mt nguyn l iu ch thp hn duy tr cht lng v s n nh ca ng truyn. c im ny cho php h thng khc phc hiu ng fading la chn thi gian. c im quan trng ca iu ch thch nghi l kh nng tng di s dng ca nguyn l iu ch mc cao hn, do h thng c tnh mm do i vi tnh trng fading thc t.

Hnh 2.30 iu ch thch nghi

K thut iu ch v m ho thch nghi l mt trong nhng u vit ca OFDM v n cho php ti u ho mc iu ch trn mi knh con da trn cht lng tn hiu (t l SNR) v cht lng knh truyn dn.

2.6.6 Lp biu ph thuc knh [10]

Lp biu ph thuc knh gii quyt vn cch thc chia s cc ti nguyn v tuyn gia nhng ngi s dng (cc u cui di ng) khc nhau trong h thng t c hiu sut s dng ti nguyn tt nht. Lp biu ph thuc knh cho php gim thiu lng ti nguyn cn thit cho mt ngi s dng, v th cho php nhiu ngi s dng hn trong khi vn p ng c cc yu cu cht lng dch v. Nguyn l lp biu cng nh vic chia s cc ti nguyn gia nhng ngi s dng, t nht v mt l thuyt, ph thuc vo cc c tnh ca giao din v tuyn, vo vic ng truyn l ng truyn ln hay truyn xung v vo vic truyn dn ca nhng ngi s dng vi nhau c trc giao hay khng. Thch ng ng truyn v lp biu ph thuc knh lin quan mt thit vi nhau v thng th chng c coi nh l mt chc nng lin kt.

2.6.7 HARQ vi kt hp mm [10]

Do tnh cht ngu nhin ca cc thay i cht lng ng truyn v tuyn, khng bao gi c th t c thch ng cht lng knh v tuyn tc thi mt cch hon ho. HARQ v th rt hu ch.

HARQ vi kt ni mm c s dng trong LTE, cho php u cui di ng yu cu truyn li nhanh chng nhng khi vn chuyn b li, v cung cp mt cng c cho thch ng tc ngm nh. Giao thc bn di l nhiu x l hybrid ARQ dng v ch (stop-and-wait) song song nhau. Trong ARQ, u thu s dng mt m pht hin li kim tra gi d liu c b li hay khng. u pht c thng bo bng NAK hoc ACK. Nu gi d liu b li v c thng bo NAK, gi s c truyn li.

Mt s kt hp ca FEC (Forward Error Correction) v ARQ c bit nh l HARQ. HARQ trong thc t phn ln c xy dng xung quanh m CRC pht hin li v m Turbo sa li, nh trong trng hp ca LTE.

Trong HARQ vi kt ni mm, nhng gi nhn c b sai, c lu trong mt b m v sau c kt hp vi truyn li t c mt gi ng tin cy. Trong LTE, Incremental Redundancy (IR) c p dng, ngha l nhng gi c truyn li khng ging nhng gi truyn u tin, m n mang thng tin b sung.

2.7 Chuyn giao

Chuyn giao l phng tin cn thit thu bao c th di chuyn trong mng. Khi thu bao chuyn ng t vng ph sng ca mt cell ny sang mt cell khc th kt ni vi cell mi phi c thit lp v kt ni vi cell c phi c hy b.

2.7.1 Mc ch chuyn giao

L do c bn ca vic chuyn giao l kt ni v tuyn khng tha mn mt b tiu chun nht nh v do hoc UE hoc E-UTRAN s thc hin cc cng vic ci thin kt ni . Khi thc hin cc kt ni chuyn mch gi, chuyn giao c thc hin khi c UE v mng u thc hin truyn gi khng thnh cng. Cc iu kin chuyn giao thng gp l: iu kin cht lng tn hiu, tnh cht di chuyn ca thu bao, s phn b lu lng, bng tn

iu kin cht lng tn hiu l iu kin khi cht lng hay cng tn hiu v tuyn b suy gim di mt ngng nht nh. Chuyn giao ph thuc vo cht lng tn hiu c thc hin cho c hng ln ln hng xung ca ng truyn dn v tuyn.

Chuyn giao do nguyn nhn lu lng xy ra khi lu lng ca cell t ti mt gii hn ti a cho php hoc vt qu ngng gii hn . Khi cc thu bao ngoi ra ca cell (c mt ti cao) s c chuyn giao sang cell bn cnh (c mt ti thp).

S lng chuyn giao ph thuc vo tc di chuyn ca thu bao. Khi UE di chuyn theo mt hng nht nh khng thay i, tc di chuyn ca UE cng cao th cng c nhiu chuyn giao thc hin trong E-UTRAN.

2.7.2 Trnh t chuyn giao

Trnh t chuyn giao gm c ba pha: pha o lng, pha quyt nh v pha thc hin.

o lng l nhim v quan trng trong qu trnh chuyn giao v hai l do c bn sau:

Mc tn hiu trn ng truyn dn v tuyn thay i rt ln ty thuc vo fading v tn hao ng truyn. Nhng thay i ny ph thuc vo mi trng trong cell v tc di chuyn ca thu bao.

S lng cc bo co o lng qu nhiu s lm nh hng n ti h thng.

thc hin chuyn giao, trong sut qu trnh kt ni, UE lin tc o cng tn hiu ca cc cell ln cn v thng bo kt qu ti mng, ti eNodeB.

Pha quyt nh chuyn giao bao gm nh gi tng th v QoS ca kt ni so snh n vi cc thuc tnh QoS yu cu v c lng t cc cell ln cn. Ty theo kt qu so snh m ta c th quyt nh thc hin hay khng thc hin chuyn giao. eNodeB kim tra cc gi tr ca cc bo co o c kch hot mt b cc iu kin chuyn giao. Nu cc iu kin ny b kch hot, eNodeB phc v s cho php thc hin chuyn giao.

Cn c vo quyt nh chuyn giao, c th phn chia chuyn giao ra thnh hai loi nh sau:

Chuyn giao quyt nh bi mng (NEHO).

Chuyn giao quyt nh bi thu bao di ng (MEHO).

Trong trng hp chuyn giao thc hin bi mng (NEHO), eNodeB thc hin quyt nh chuyn giao. Trong trng hp MEHO, UE thc hin quyt nh chuyn giao. Trong trng hp kt hp c hai loi chuyn giao NEHO v MEHO, quyt nh chuyn giao c thc hin bi s phi hp gia eNodeB vi UE.

Ngay c trong trng hp chuyn giao MEHO, quyt nh cui cng v vic thc hin chuyn giao l do eNodeB. ENodeB c trch nhim qun l ti nguyn v tuyn (RRM) ca ton b h thng.

Hnh 2.31 Nguyn tc chung ca cc thut ton chuyn giao

Quyt nh chuyn giao da trn cc thng tin o c ca UE v eNodeB cng nh cc iu kin thc hin thut ton chuyn giao. Nguyn tc chung thc hin thut ton chuyn giao c th hin trn hnh trn.

Cc thut ng v cc tham s sau c s dng trong thut ton chuyn giao:

Ngng gii hn trn: l mc tn hiu ca kt ni t gi tr cc i cho php tha mn mt cht lng dch v QoS yu cu.

Ngng gii hn di: l mc tn hiu ca kt ni t gi tr cc tiu cho php tha mn mt cht lng dch v QoS yu cu. Do mc tn hiu ca ni kt khng c nm di ngng .

Gii hn chuyn giao: l tham s c nh ngha trc c thit lp ti im m cng tn hiu ca cell bn cnh (cell B) vt qu cng tn hiu ca cell hin ti (cell A) mt lng nht nh.

Tp tch cc: l mt danh sch cc nhnh tn hiu (cc cell) m UE thc hin kt ni ng thi ti mng truy nhp v tuyn (E-UTRAN). Gi s thu bao UE trong cell A ang chuyn ng v pha cell B, tn hiu hoa tiu ca cell A b suy gim n mc ngng gii hn di. Khi t ti mc ny, xut hin cc bc chuyn giao theo cc bc sau y:

(1) Cng tn hiu A bng vi mc ngng gii hn di. Cn tn hiu B s c RNC nhp vo tp tch cc. Khi UE s thu tn hiu tng hp ca hai kt ni ng thi n UTRAN.

(2) Ti v tr ny, cht lng tn hiu B tt hn tn hiu A nn n c coi l im khi u khi tnh ton gii hn chuyn giao.

(3) Cng tn hiu B bng hoc tt hn ngng gii hn di. Tn hiu A b xa khi tp tch cc bi RNC.

Kch c ca tp tch cc c th thay i c v thng thng trong khong t 1 n 3 tn hiu.

Trnh t chuyn giao gia hai cell trong LTE thc hin nh sau:

UE truyn bo co o lng n eNodeB. Trong bo co ny l o lng cho mt cell ch vi mc RSRP cao hn cell ang phc v.

eNodeB ngun quyt nh chuyn giao l cn thit, khi xc nh cell ch ph hp v yu cu truy cp n eNodeB ch ang iu khin cell ch.

eNodeB ch chp nhn yu cu chuyn giao v cung cp cho eNodeB ngun cc thng s i hi cho UE truy cp n cell ch chuyn giao c th thc thi, cc thng s bao gm cell ID, tn s sng mang v ti nguyn ch nh cho ng xung v ng ln.

eNodeB ngun gi mt bn tin mobility from E-UTRA n UE

UE nhn c bn tin, ngt kt ni v tuyn vi eNodeB ngun v thit lp kt ni mi vi eNodeB ch. Trong sut thi gian ny ng truyn d liu b ngt.

2.7.3 Cc loi chuyn giao

Ty theo hnh thc s dng trong cc c ch chuyn giao, c th phn chia chuyn giao thnh cc nhm nh: chuyn giao cng, chuyn giao mm v chuyn giao mm hn.

2.7.3.1 Chuyn giao mm v mm hn

Chuyn giao mm v mm hn da nguyn tc kt ni ni trc khi ct (Make before break).

Chuyn giao mm: chuyn giao gia cc cell l chuyn giao c thc hin gia cc cell khc nhau, trong trm di ng bt u thng tin vi mt trm gc mi m vn cha ct thng tin vi trm gc c. Chuyn giao mm ch c th c thc hin khi c trm gc c ln trm gc mi u lm vic cng mt tn s. MS thng tin vi 2 sector ca 2 cell khc nhau (chuyn giao 2 ng) hoc vi 3 sector ca 3 cell khc nhau (chuyn giao 3 ng).

Chuyn giao mm hn: l chuyn giao c thc hin khi UE chuyn giao gia 2 sector ca cng mt cell hoc chuyn giao gia 2 cell do cng mt BS qun l. y l loi chuyn giao trong tn hiu mi c thm vo hoc xa khi tp tch cc, hoc thay th bi tn hiu mnh hn trong cc sector khc nhau ca cng BS.

Trong trng hp chuyn giao mm hn, BS pht trong mt sector nhng thu t nhiu sector khc nhau. Khi c chuyn giao mm v chuyn giao mm hn c thc hin ng thi, trng hp ny gi l chuyn giao mm - mm hn.

Chuyn giao mm - mm hn: MS thng tin vi hai sector ca cng mt cell v mt sector ca cell khc. Cc ti nguyn mng cn cho kiu chuyn giao ny gm ti nguyn cho chuyn giao mm hai ng gia cell A v B cng vi ti nguyn cho chuyn giao mm hn ti cell B.

Hnh 2.32 Chuyn giao mm

Hnh 2.33 Chuyn giao mm - mm hn

2.7.3.2 Chuyn giao cng

Chuyn giao cng c thc hin khi cn chuyn knh lu lng sang mt knh tn s mi. Cc h thng thng tin di ng t ong FDMA v TDMA u ch s dng phng thc chuyn giao ny.

Hnh 2.34 Chuyn giao cngChuyn giao cng da trn nguyn tc ct trc khi ni (Break Before Make) c th c chia thnh: chuyn giao cng cng tn s v chuyn giao cng khc tn s. Trong qu trnh chuyn giao cng, kt ni c c gii phng trc khi thc hin kt ni mi. Do vy, tn hiu b ngt trong khong thi gian chuyn giao. Tuy nhin, thu bao khng c kh nng nhn bit c khong ngng . Trong trng hp chuyn giao cng khc tn s, tn s sng mang ca knh truy cp v tuyn mi khc so vi tn s sng mang hin ti.

u im ca chuyn giao cng l tip tc mt cuc gi khi vt qua mng hin hnh, cung cp cc dch v m rng, gim rt cc cuc gi, bao ph v tch hp mng LTE so vi nhiu mng c sn.

Nhc im ca chuyn giao cng l c th xy ra rt cuc gi do cht lng ca knh mi chuyn n tr nn qu xu trong khi knh c b ct.

2.7.4 Chuyn giao i vi LTE [3]

H thng WCDMA s dng chuyn giao mm cho c ng ln v ng xung. H thng HSPA s dng chuyn giao mm cho ng ln nhng khng s dng cho ng xung. h thng LTE, khng s dng chuyn giao mm, ch c chuyn giao cng, do h thng tr nn n gin hn.

Trong h thng trc, mng li qun l RNC, RNC qun l cc trm BS v BS li qun l cc UE. V th khi UE chuyn qua vng RNC khc phc v, th mng li ch bit n RNC ang phc v UE. Mi chuyn giao c iu khin bi RNC Nhng i vi E-UTRAN, mng li c th thy mi chuyn giao.

Hnh 2.35 Cc loi chuyn giao

Chuyn giao cng tn s (intra-frequency) c thc hin gia cc cell trong cng mt eNodeB. Chuyn giao khc tn s (intra-frequency) c thc hin gia cc cell thuc cc eNodeB khc nhau.

UE s thc hin trn d on o lng RSRP (Reference Signal Receive Power) v RSRQ (Reference Signal Receive Quality) da trn tn hiu tham kho RS (Reference Signal) nhn c t cell ang phc v v t cell nh hng mnh nht. Gii thut chuyn giao da trn gi tr RSRP v RSRQ, chuyn giao c thit lp khi cc thng s ny t cell nh hng cao hn cell ang phc v.

WCDMA, chng ta dng CPICH RSCP quyt nh chuyn giao th LTE ta s dng RSRP. RSRP l cng sut thu tn hiu tham kho, n l trung bnh cng sut ca tt c cc thnh phn ti nguyn (mang tn hiu tham kho) qua ton b bng thng. N c th c o lng tn hiu OFDM mang tn hiu tham kho. o lng RSRP cung cp cng tn hiu c th ca cell. o lng ny c s dng lm ng vo cho chuyn giao v quyt nh chn li cell. RSSI c nh ngha nh tng cng sut bng rng nhn c quan st bi UE t tt c cc ngun, bao gm cell phc v v cell khng phc v, can nhiu knh v nhiu nhit trong bng thng o lng c th. RSSI khng c bo co khi o lng m n c xem l ng vo tnh ton RSRQ. Vic o lng RSRQ cung cp cht lng tn hiu ca cell c th. Ging nh RSRP, vic o lng ny c dng xc nh cc ng c vin cell theo cht lng tn hiu ca chng. o lng ny c s dng nh ng vo ca chuyn giao v quyt nh chn li cell, o lng RSRP khng cung cp tin cy cho quyt nh chuyn giao. RSRQ c nh ngha l t s N.RSRP/RSSI trong N l s RB ca bng thng o lng RSSI ca LTE. Vic o lng ny c t s v mu s phi c thc hin vi cng s RB. Trong khi RSRP ch ra mnh tn hiu, RSRQ b sung mc can nhiu bi v n bao gm RSSI. V vy RSRQ cho php kt hp gia cng tn hiu vi can nhiu bo co mt cch hiu qu.

Khi thc hin o lng chuyn giao th chnh lch mc RSRP v RSRQ phi mt mc chnh lch mi quyt nh chuyn giao. i vi 2 cell cng tn s, chnh lch RSRP t +/- 2 dB n +/- 3 dB, chnh lch RSRQ t +/- 2,5 n 4 dB. i vi 2 cell khc tn s th chnh lch RSRP l +/- 6 dB, chnh lch RSRQ t +/- 3 n 4 dB.2.8 iu khin cng sut

i vi LTE, iu khin cng sut l chm i vi hng ng ln. Trong hng ng xung khng c iu khin cng sut. Khi bng thng thay i do s thay i tc d liu, cng sut truyn dn tuyt i ca UE cng s thay i. iu khin cng sut hin nay cha thc s l iu khin cng sut tuyt i m l mt ph cng sut (PSD), cng sut trn mi Hz, i vi mt thit b ring bit. iu g to iu kin cho vic s dng mt tc chm hn iu khin cng sut l vic s dng cc ngun ti nguyn trc giao trong ng ln LTE, trong n trnh c cc vn gn-xa do yu cu v iu khin cng sut nhanh trong WCDMA. Cc ng lc chnh cho s iu khin cng sut l lm gim mc cng sut tiu th ca thit b u cui v cng trnh di ng qu ln trong eNodeB thu, hn l lm gim s can nhiu. Nguyn l iu khin cng sut hng ln trong LTE c minh ha nh trong hnh 2.36, ni m s thay i tc d liu m PSD s gi khng i nhng kt qu l tng cng sut truyn ti c iu chnh tng i vi s thay i tc d liu.

Hnh 2.36 Cng sut hng ln LTE vi thay i tc d liuVic iu khin cng sut thc t c da trn s xc nh tn tht ng truyn, c tnh n cc thng s ring ca v sau p dng cc gi tr (tch ly) ca h s iu chnh nhn c t eNodeB. Ty thuc vo cc thng s thit lp lp cao hn, lnh iu khin cng sut hoc l 1dB ln hoc xung hoc sau cc thit lp ca [-1dB, 0, +1dB, +3dB] c s dng. Cc c im k thut cn bao gm iu khin cng sut da trn cc gi tr tuyt i. Tng di ng ca iu khin cng sut l nh hn so vi trong WCDMA, v cc thit b hin nay c mt mc cng sut ti thiu l -41dBm so vi -50dBm vi WCDMA.

2.9 Kt lun chng

Chng 2 khi qut c cu trc mng 4G LTE, cc c tnh k thut v cc k thut s dng trong LTE. Mng LTE c u im vt tri so vi 3G v tc , thi gian tr nh, hiu sut s dng ph cao cng vi vic s dng bng thng linh hot, cu trc n gin nn gi thnh gim. to nn cc u im , LTE phi hp nhiu k thut, trong , n s dng k thut OFDMA ng xung. Cc sng mang trc giao vi nhau, do tit kim bng thng, tng hiu sut s dng ph tn v gim nhiu ISI. Cng vi cc u im th OFDM c khuyt im l s thng ging ng bao ln dn n PAPR ln, khi PAPR ln th i hi cc b khuch i cng sut tuyn tnh cao trnh lm mo dng tn hiu, hiu sut s dng cng sut thp v th c bit nh hng i vi cc thit b cm tay. Do , LTE s dng k thut SC-FDMA cho ng ln. Cng vi cc k thut , LTE cn h tr MIMO, MIMO l mt phn tt yu ca LTE t c yu cu v thng lng v hiu qu s dng ph. Cng vi cc k thut ny, chng 2 cn trnh by v lp biu ph thuc knh, thch ng ng truyn, HARQ vi kt hp mm. Chuyn giao trong LTE, v chuyn giao gia LTE vi cc mng khc. ng thi cn bng cng sut pht i vi QoS yu cu, ti thiu can nhiu v tng tui th pin ca thit b u cui, iu khin cng sut ng ln c s dng LTE, iu khin cng sut kt hp c vng h v vng kn, nhng do tnh trc giao ng ln ca LTE nn trnh c vn gn xa (vn in hnh trong iu khin cng sut ca WCDMA) v v th LTE khng cn s dng iu khin cng sut vng kn nhanh.

CHNG 3 QUY HOCH MNG 4G LTE3.1 Gii thiu chng

Quy hoch mng LTE cng ging nh quy hoch mng 3G. h thng di ng 4G, ng ln v ng xung l bt i xng. Do vy, mt trong hai ng s thit lp gii hn v dung lng hoc vng ph sng. Vic tnh ton qu ng truyn v phn tch nhiu khng ph thuc vo loi cng ngh s dng. Mc ch ca pha nh c l c lng s lng cc trm cn s dng, cu hnh trm v s lng cc phn t mng d bo gi thnh u t cho mng. Chng ny chng ta s tm hiu v qu ng truyn ca LTE, cc m hnh truyn sng phc v cho qu trnh c lng s eNodeB ca mng theo iu kin ti u 1, v s trm eNodeB theo iu kin ti u 2 t ta quyt nh c s eNodeB cn thit cho vng cn quy hoch.3.2 Gii thiu v nh c mng v tuynnh c mng cung cp cc nh gi u tin, nhanh chng cu hnh ca mng khng dy. nh c l mt phn ca ton b qu trnh quy hoch, trong cng bao gm, quy hoch chi tit v ti u ha mng di ng khng dy. Nhn chung, quy hoch l mt qu trnh lp i lp li bao gm cc bc thit k, tng hp v vn hnh. Mc ch ca ton b bi ny l cung cp mt phng php thit k mng di ng khng dy nh vy m n p ng cc yu cu t ra bi khch hng. Qu trnh ny c th c sa i ph hp vi nhu cu ca bt k mng di ng khng dy. y l mt qu trnh rt quan trng trong vic trin khai mng.

Hnh 3.1 Tin trnh quy hoch mng v tuyn [5]Hnh 3.1 cho thy vic thc hin quy hoch mng di ng khng dy v v tr ca nh c mng trong ton b tin trnh. Pha nh c mng a ra mt c tnh m sau c s dng cho quy hoch chi tit mng. Khi mng hon thnh k hoch mng, cc thng s c ti u ha ti a h thng t hiu qu.

nh c mng da trn mt tp hp cc thng s u vo v kt qu c cung cp ch c lin quan n vic thit lp cc thng s u vo. Nhng thng s ny bao gm khu vc c xem xt, d kin lu lng v yu cu cht lng dch v (QoS). nh c mng cung cp nh gi ca cc yu cu cho c s mng li. iu ny c thc hin vi s gip ca cng c nh c cho c truy cp v mng li. nh c s dng m hnh tng i n gin cho m hnh trong cc iu kin thc t so vi quy hoch chi tit. Cc m hnh n gin v cc phng php lm gim thi gian cn thit cho nh c. Mt khc, cng c nh c phi chnh xc, cung cp kt qu chnh xc vi mt mc chp nhn c.

nh c mng di ng khng dy lin quan trc tip n cht lng v hiu qu ca mng, v c th nh hng xu n s pht trin ca n. nh c mng di ng ni chung v mng di ng LTE ni ring bao gm cc bc c bn sau y:

Phn tch d liu v lu lng

c tnh vng ph

nh gi lu lng

nh c phng tin

Mt tp hp u vo l quan trng nh c mang li kt qu chnh xc nh c mng LTE i hi phi c mt s yu t d liu c bn. Nhng thng s ny bao gm s thu bao, lu lng phn phi, khu vc a l cn c bao ph, bng tn, phn b bng thng, vng ph v dung lng yu cu. M hnh truyn sng theo khu vc v bng tn nn c la chn v sa i (nu cn thit). iu ny l cn thit cho c tnh vng ph.

Cc thng s h thng c th nh: Cng sut pht ca ng - ten, li ca n, c tnh suy hao h thng, loi h thng ng-ten c s dng, phi c bit trc khi bt u nh c mng di ng LTE. Mi mt mng LTE thit lp cc thng s ring ca n.

Phn tch lu lng a ra mt c tnh lu lng c thc hin bi h thng. Cc loi lu lng s c thc hin bi mng c m hnh ha. Loi lu lng c th bao gm cc cuc gi thoi VOIP, PS hoc lu lng truy cp CS. Cc chi ph thc hin ca tng loi hnh lu lng c tnh ton v bao gm trong m hnh. Thi gian v s lng lu lng cng c d on nh gi vic thc hin ca mng v xc nh xem mng c th thc hin y cc yu cu t ra.

c tnh vng ph c s dng xc nh vng ph sng ca mi trm gc. c tnh vng ph tnh ton khu vc ni trm gc c th nhn c bi lng nhng ngi s dng. n a ra din tch ti a c th c bao ph bi mt trm gc. Nhng khng cn thit l mt chp nhn kt ni (v d nh mt cuc gi thoi) gia cc trm gc v my thu c th c thit lp trong vng ph sng. Tuy nhin, trm gc c th c pht hin bi my thu trong vng ph sng.

Quy hoch vng ph bao gm d tr tuyn v phn tch vng ph. RLB tnh cng sut nhn c bi ngi s dng c pht bi mt cng sut c th (t cc my pht hoc trm gc). RLB bao gm li v suy hao ca tn hiu trn ng truyn t my pht n my thu. iu ny bao gm li ca my pht v my thu cng nh suy hao v nh hng ca mi trng khng dy gia chng. Suy hao trong mi trng truyn dn, fading nhanh v fading chm c a vo qu ng truyn.

Hnh 3.2 D tr tuyn ca mng di ng khng dy [5]Hnh 3.2 cho thy mt v d in hnh ca mt d tr lin kt v tuyn. ng ten pht bc x in t theo hng ca ng - ten thu. Lng cng sut n c pha thu ph thuc vo nh hng ca ng ten pht v s mt mt trong mi trng truyn sng. Trong hnh 3.2 c hai ng suy hao (ng mu xanh) v suy hao trong nh (ng mu hng) c ch ra. Tp m t cc ngun khc nhau cng gp phn tn hiu suy gim. Sau khi cng v tr i tt c li v suy hao, cng sut thu c thc t c tnh ton. ng mu xanh trong ct cui cng ca hnh 3-2 cho bit cng sut nhn c i vi mi trng khng gian ngoi tri, trong khi ng mu xanh l cy ch ra cng sut in trong nh nhn c. Gi tr ca 17dB l s khc bit gia cc tn hiu nhn c v tp m trong h thng i vi mi trng trong nh. T l tn hiu trn tp m l ch s hiu sut ca h thng khng dy. T s ny cao hn th tc d liu t c cng cao hn v ngc li.

Da trn cc tnh ton ca RLB, suy hao ti a cho php nhn c. Suy hao ti a cho php l s suy gim ca tn hiu khi n di truyn t my pht n my thu. S suy hao ny c chuyn i thnh khong cch bng cch s dng cc m hnh truyn sng thch hp. y l khong cch t cc trm gc ni pht tn hiu v c th c nhn bi my thu. Khong cch hay bn knh ca cell c s dng tnh ton s lng cc site yu cu ph ton b khu vc i vi c tnh vng ph.

Quy hoch dung lng cp n kh nng ca mng cung cp dch v cho ngi s dng vi mt mc mong mun v cht lng. Sau khi cc vng ph c tnh bng cch c tnh vng ph, cc vn dung lng lin quan c phn tch. iu ny lin quan n vic la chn cc site v cu hnh h thng, v d nh knh c s dng, thnh phn knh v cc yu t. Nhng thnh phn ny l khc nhau cho mi h thng. Cu hnh c chn nh vy m n p ng c lu lng yu cu. Trong mt s h thng di ng khng dy, vng ph v dung lng lin quan n nhau, v d nh WCDMA. Trong trng hp ny, d liu lin quan n phn phi ngi s dng v d bo tng trng thu bao l v cng quan trng. Nhm nh c phi xem xt cc gi tr ny nh n c tc ng trc tip vo vng ph sng v dung lng. nh gi cng sut a ra mt c tnh s lng cc site cn thit thc hin d on lu lng vng ph sng.

Mt khi s lng cc site theo s d on lu lng c xc nh, cc giao din ca mng c nh c. S lng cc giao din c th khc mt t trong mt s h thng n nhiu trong cc h thng khc. Mc tiu ca bc ny l thc hin vic phn b lu lng m khng to ra hin tng nghn c chai trong mng khng dy. Tt c cc yu cu cht lng dch v s c cp v gim chi ph dch v xung mc tt thiu. nh c giao din tt l rt quan trng mn hiu sut ca mng.3.3 Tin trnh nh c mng LTE

Mc tiu ca nh c mng truy cp mng LTE l c tnh mt site yu cu v cu hnh site cho cc khu vc quan tm. Ban u quy hoch mng truy nhp LTE bao gm phn tch qu nng lng trng truyn v phn tch vng ph, c tnh dung lng cell v c tnh s lng eNodeB, cng truy cp (MME/UPE) v cu hnh phn cng, v cui cng l giao din gia cc thit b khc nhau khc nhau. Phn ny tp trung vo cc vn lin quan n nh c mng LTE.

3.3.1 u vo nh c mng LTE

Mt trong nhng mc tiu c bn ca cng vic ny l phn bit r rng gia u vo v u ra ca nh c LTE. Phn ny tho lun v tt c cc yu t u vo nh c LTE c s dng trong pht trin cc phng php v m hnh cho nh c mng LTE. u vo nh c LTE c th c phn chia thnh ba loi: cht lng, vng ph v dung lng lin quan n u vo.Cht lng u vo lin quan bao gm thng lng cell trung bnh v kh nng rt. nhng tham s c khch hng yu cu cung cp mt mc nht nh ca dch v cho ngi s dng ca n. Nhng u vo ny chuyn i trc tip thnh cc thng s cht lng dch v (QoS). Bn cnh tiu ch hiu sut bin cell c s dng trong cc cng c nh c xc nh bn knh cell v do s lng cc site. Ba phng php s dng xc nh bin cell. Nhng phng php ny bao gm nh ngha thng lng ngi dng ti a ti bin cell, phm vi vng ph ti a i vi MCS thp nht v bn knh cell c xc nh trc. Vi mt bn knh t bo c xc nh trc, cc thng s c th c thay i kim tra tc d liu t c kch thc cell ny. S la chn ny cho ti u ha cng sut pht linh hot v xc nh tc d liu ph hp tng ng vi cng sut ny.u vo nh c LTE cho quy hoch vng ph tng t nh cc u vo tng ng cho mng 3G UMTS. Qu ng truyn (RLB) l c tm quan trng trung tm k hoch vng ph trong LTE. RLB u vo bao gm cng sut pht, h thng ng ten pht v ng ten thu, s lng cc ng-ten c s dng, li v suy hao h thng thng thng, ti cell v m hnh truyn sng. LTE c th hot ng trong c hai bng tn thng thng ca 900 v 1800 MHz cng nh m rng n bng tn 2600 MHz. M hnh cho tt c ba di tn s c kt hp trong cng tc ny. Ngoi ra, cc loi knh (i b, xe c) thng tin a l l cn thit bt u thc hin nh c vng ph. Thng tin a l u vo bao gm cc loi thng tin khu vc ( th, nng thn, vv) v kch thc ca tng loi khu vc u c ph. Hn na, xc sut yu cu vng ph ng mt vai tr quan trng trong xc nh bn knh cell. Ngay c mt thay i nh trong vn ph gy ra mt lng thay i ln trong bn knh cell.Cc thng s quy hoch dung lng u vo cung cp cc yu cu c p ng bng bi nh c mng LTE. u vo quy hoch dung lng cung cp s thu bao trong h thng, nhu cu dch v v mc s dng ca thu bao. Ph sn c v rng bng thng s dng h thng LTE cng rt quan trng i vi quy hoch dung lng LTE. Phn tch lu lng v tc d liu h tr cc dch v c sn (ting ni, d liu) c s dng xc nh s lng thu bao c cung cp bi mt cell duy nht v cui cng bn knh t bo trn c s nh gi dung lng. Kt qu m phng mc h thng LTE v kt qu mc m phng lin kt LTE c s dng thc hin quy hoch dung lng cng vi cc yu t u vo khc. Nhng kt qu ny thu c t ni b ngun ca Nokia. D bo tng trng thu bao c s dng trong cng vic ny d on s tng trng v chi ph ca mng trong nhng nm ti.3.3.2 u ra nh c mng LTEKt qu u ra hay mc tiu ca qu trnh nh c mng LTE c tho lun gin tip trong trc phn. Kt qu u ra ca pha nh c c s dng c tnh kh thi v chi ph ca mng. Nhng kt qu u ra tip tc c s dng trong quy hoch mng chi tit v c th c s dng cho cng vic tng lai trong quy hoch mng li LTE. Mng LTE c nh c c th gip nhm mng li LTE trong vic ln k hoch thit k mng ph hp v xc nh s lng truyn dn lin kt cn thit trong giai on khi u ca mng.

Kch thc cell l u ra chnh ca bi nh c mng LTE. Hai gi tr ca bn knh cell thu c, t vic nh gi vng ph v th hai t vic nh gi dung lng. Gi tr nh hn ca hai s c thc hin nh l kt qu cui cng. Bn knh t bo sau c s dng xc nh s lng cc site. Gi s cell hnh lc gic, s lng cc site c th c tnh bng cch s dng hnh hc n gin. Dung lng ca cc eNB thu c t nh gi dung lng, cng vi s lng thu bao c h tr bi mi t bo. nh c giao din l bc cui cng trong nh c mng truy cp LTE, l ra khi phm vi ca n ny. L do l giao din LTE (S1 v X2) vn ang c tiu chun ha ti thi gian lm n ny.

3.3.3 Tin trnh nh c mng LTE

Qu trnh nh c mng LTE bt u vi vic tnh ton qu ng truyn , c s dng xc nh suy hoa ng truyn ti a. Kt qu ca bc ny ph thuc vo cc m hnh truyn sng c s dng. c tnh kch thc cell thu c trong bc ny, dn n kch thc ti a cho php ca site ca cc t bo. Thng s c s dng tnh ton s lng cell trong khu vc quan tm. Do , thu c mt c tnh s b s eNB yu cu.

Tnh ton dung lng theo sau cc qu trnh c tnh vng ph. Nu c tnh vng ph sng cho cu hnh nht nh, p ng cc yu cu dung lng, sau khng c s b xung no ti k hoch trc. Ni cch khc, s cell sites thch hp c cng vo kt qu dung lng. Nu dung lng mong i cao nht c s dng, c th dn ti s site cao khng cn thit.

nh gi dung lng eNode-B l bc tip theo, hon thnh tin trnh nh c. Trong n ny ch yu tp trung vo qu ng truyn, c tnh dung lng cell v cc cng c, cc trng hp nghin cu cho nh c mng LTE. Hnh 3.3 ch ra bi nh c mng LTE mt cch c th.

Hnh 3.3: nh c mng LTE [5]Bc 1: Phn tch lu lng v d liu

y l bc u tin trong nh c LTE. N xoay quanh s tp trung u vo yu cu v phn tch chun b cho tin trnh nh c mng LTE. D liu hot ng v yu cu c phn tch xc nh cu hnh h thng tt nht. V d, c th bao quanh vic chn 2 hay 3 bng thng khc nhau cho phn tch.

Bc 2: Phn tch lu lng

Lu lng yu cu c phn tch thu c cu hnh mng tt nht c th vi s cung cp nh nht (u vo). Lu lng gi cao nht c s dng thay gi tr trung bnh.

Bc 3: Quy hoch vng ph

Phn tch vng ph c bn gi li hu ht cc phn ca bc thit k mng nh h thng 3G. RLB l tri tim ca quy hoch vng ph, cho php kim tra m hnh suy hao ng v tc d liu nh. Kt qu l s sp xp cell tnh n s site b hn ch bi vng ph. iu ny yu cu s la chn m hnh truyn sng thch hp tnh ton suy hao ng. Vi kin thc ca c tnh kch thc cell v vng c bao ph, mt c tnh mt s site c thnh lp. c tnh ny da trn vng ph yu cu v cn thit c xc minh cho dung lng yu cu.

Bc 4: Quy hoch vng ph

Vi mt c tnh th ca kch thc cell v s site, s kim tra phn tch vng ph c tin hnh cho dung lng yu cu. N kim tra liu rng vi mt site a ra, h thng c th tin hnh ti ring bit hay s site mi phi b xung vo. Trong LTE, ch th chnh ca dung lng l phn phi SINR trong cell. Phn phi ny nhn c bi vic tin hnh cc m phng mc h thng. Phn phi SINR c th trc tip nh x ti dung lng h thng (tc d liu). Dung lng cell LTE b nh hng bi mt s yu t, v d nh b sung lp lch gi, cc MSC h tr, cu hnh anten v mc nhiu. T rt nhiu kt qu m phng ca thit lp c yu cu cho phn tch ton din. Dung lng da vo tnh s site c so snh vi kt qu vng ph v s ln hn ca hai s c chn nh l s site tnh cui cng.

Bc 5: nh c phng tin

nh c phng tin gii quyt nh c giao din gia cc phn t mng khc nhau. Trong LTE, S1(gia eNode-B v aGW) v X2 (gia hai eNode-B) l hai giao din c nh c. Nhng giao din ny ang trong qu trnh chun ha thi im lm ny.

3.4 Quy hoch vng ph

i vi mng di ng t bo, c lng vng ph c dng quyt nh vng ph ca mi trm gc, n a ra mt vng ti a c th c bao ph bi trm gc. Nhng n khng cn thit xc lp mt kt ni gia UE v trm gc. Tuy nhin, trm gc c th pht hin c UE trong vng bao ph ca n. 3.4.1 Qu ng truyn

Tnh ton qu ng truyn c lng suy hao tn hiu cho php cc i (pathloss) gia di ng v trm gc. Tn hao ln nht cho php cho ta c lng vng ph ca cell ln nht vi m hnh knh truyn ph hp. Vi vng bao ph ca cell s cho ta tnh ton c s trm gc c s dng bao ph vng a l mong mun. Tnh ton qu ng truyn cng c dng so snh quan h v vng ph ca cc h thng khc nhau. Mi quan h qu ng truyn ch ra h thng v tuyn LTE mi s thc hin tt nh th no khi n c trin khai trong cc trm gc tn ti ca h thng GSM v WCDMA. 3.4.1.1 Tnh ton qu ng ln cho LTE

Cc thng s v cng thc s dng tnh ton qu ng truyn ln cho LTE:

Cng sut my pht (PTxm): i vi ng ln cng sut my pht y l cng sut ca UE. Ty thuc vo lp cng sut pht m UE s dng s c gi tr cng sut ti a khc nhau. n v dng tnh ton cho cng sut my pht l dBm.

Khuch i anten (Gm): ph thuc vo thit b v bng tn s dng. N c gi tr t -5 n 10 dBi.

Tn hao phi v b ni (Lfm)

Tn hao c th (Lbody): l tn hao in hnh i vi qu ng truyn cho dch v thoi v di ng c gi gn vi tai nghe. C gi tr t 3 n 5 dB i vi dch v thoi. n v l dB.

Cng sut pht x ng hng tng ng (EIRPm): c n v l dBm v c tnh ton theo cng thc sau:

EIPRm = PTxm + Gm + Lfm Lbody

(3.1)

H s tp m my thu (NF): trong trng hp ny my thu l trm gc v c n v l dB.

Cng sut tp m nhit u vo my thu (Ni): c n v l dBm v c tnh ton bng cng thc sau:

Ni = 30 + 10lgk + 10log290K + 10lgB

(3.2)

Vi k l hng s Boltzman v c gi tr k = 1.3824 x 10-23 J/K. B l bng thng ph thuc vo tc bit, tng ng vi mi tc bit s c s RB khc nhau c pht i. Chng hn nh 64 kbps tng ng vi 2 RB c pht i tng ng vi B l 360 KHz.

Cng sut tp m nn my thu (Ni): c n v l dBm v c tnh ton theo cng thc sau:

N = Ni + NF

(3.3)

D tr nhiu (Mi): d tr nhiu LTE s nh hn d tr nhiu WCDMA v cc tn hiu ng ln c trc giao. N c n v l dB v n c gi tr nm trong khong t 1-10 dB.

Tng tp m nhiu + giao thoa (N + I): c n v l dBm v c tnh ton theo cng thc sau: (N + I)(dBm) = N + Mi

(3.4)

T s SNR yu cu (SNRr): c ly t m phng. C n v l dB.

nhy my thu hiu dng (Pmin): c n v l dB v c xc nh theo cng thc sau:

Pmin = (N + I) (dBm) + SNRr (dB)

(3.5)

Khuch i anten trm gc (Gb): ph thuc vo kch c anten v s sector. C gi tr t 15 n 21 dBi. n v ca n l dBi.

Tn hao phi v b ni (Lf): tn hao pha trm gc. C n v l dB.

Khuch i MHA (GMHA): MHA l b khuch i trn thp anten, n c n v l dB.

Tn hao ng truyn cc i cho php (Lmax): c n v l dB v c tnh ton theo cng thc sau:

Lmax = EIRPm Pmin + Gb Lf + GMHA

(3.6)3.4.1.2 Tnh ton qu ng xung cho LTECc thng s v cng thc s dng tnh ton qu ng truyn xung cho LTE:

Cng sut my pht (PTxb): i vi ng ln cng sut my pht y l cng sut ca trm gc. n v dng tnh ton cho cng sut my pht l dBm. Gi tr in hnh l t 43 - 48 dBm.

Khuch i anten (Gb): ph thuc vo kch c anten v s sector. C gi tr t 15 n 21 dBi. n v ca n l dBi.

Tn hao phi v b ni (Lf)

Cng sut pht x ng hng tng ng (EIRPb): c n v l dBm v c tnh ton theo cng thc sau:

EIPRb = PTxm + Gb + Lf

(3.7)

H s tp m my thu (NF): trong trng hp ny my thu l trm gc v c n v l dB.

Cng sut tp m nhit u vo my thu (Ni): c n v l dBm v c tnh ton bng cng thc sau:

Ni = 30 + 10lgk + 10log290K + 10lgB

(3.8)

Vi k l hng s Boltzman v c gi tr k = 1.3824 x 10-23 J/K. B l bng thng ph thuc vo tc bit, tng ng vi mi tc bit s c s RB khc nhau c pht i. Chng hn nh 1Mbps tng ng vi 50 RB c pht i tng ng vi B l 9 MHz.

Cng sut tp m nn my thu (Ni): c n v l dBm v c tnh ton theo cng thc sau:

N = Ni + NF

(3.9)

D tr nhiu (Mi): N c n v l dB v c gi tr t 3-8 dB.

B sung nhiu knh diu khin (Mcch)

Tng tp m nhiu + giao thoa (N + I): c n v l dBm v c tnh ton theo cng thc sau: (N + I)(dBm) = N + Mi + Mcch (3.10)

T s SNR yu cu (SNRr): c ly t m phng. C n v l dB.

nhy my thu hiu dng (Pmin): c n v l dB v c xc nh theo cng thc sau:

Pmin = (N + I) (dBm) + SNRr (dB)

(3.11)

Khuch i anten trm gc (Gm): ph thuc vo thit b v bng tn s dng. N c gi tr t -5 n 10 dBi.

Tn hao phi v b ni (Lfm): tn hao pha UE. C n v l dB.

Tn hao c th (Lbody): l tn hao in hnh i vi qu ng truyn cho dch v thoi v di ng c gi gn vi tai nghe. C gi tr t 3 n 5 dB i vi dch v thoi. n v l dB.

Tn hao ng truyn cc i cho php (Lmax): c n v l dB v c tnh ton theo cng thc sau:

Lmax = EIRPb Pmin + Gm Lfm - Lbody

(3.12)3.4.1.3 V d v qu ng truyn V d tnh qu ng ln LTE cho 64kbps vi my thu trm gc hai antenBng 3.1 V d v qu ng ln ca LTE [10]My pht (u cui di ng)

Cng sut pht (dBm) 24,0PTxm

Khuch i anten (dBi)0,0Gm

Tn hao phi + b ni (dB)0,0Lfm

Suy hao c th ca MS ng ln (dB)0,0Lbody

Cng sut pht x ng hng tng ng (dBm)24,0EIRPm = PTxm+ Gm - Lfm - Lbody

My thu (BS)

H s tp m my thu trm gc (dB)2,0NF

Cng sut tp m nhit u vo my thu (dBm)-118,4Ni

=30+10lgk+10lg290K+10lg(360KHz)

Cng sut tp m nn my thu (dBm)-116,4N = Ni + NF

D tr nhiu (dB)2,0Mi

Tng tp m + giao thoa (dBm)-114,4(N + I) (dBm) = N + Mi

T s SNR yu cu (dB)-7SNRr , t m phng

nhy my thu (dBm)-121,4Pmin= (N + I) (dBm) + SNRr

Khuch i anten (dBi)18,0Gb

Tn hao phi + b ni trm gc2,0Lf

Khuch i MHA (dB)2,0GMHA

Tn hao ng truyn cc i (dB)163,4Lmax=EIRPm-Pmin+Gb+GMHA-Lf