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Chng I: Tng quan v cng ngh LTEI.1: Gii thiuI.2: Tng quan v cng ngh LTEI.3: Cc tnh nng v yu cu thit kI.4: a truy nhp

I.5: Kh nng ng dngChng II: Cu trc h thngII.1 Truy nhp v tuyn mt t E-UTRANII.3 H thng mng liChng III : Truy nhp v tuynIII.1 TRuy nhp ng xungIII.2: Truy nhp ng lnIII.3: ARQ kim sot li v k hp mmIII.4: a truy nhp MIMO

III.5: Cu trc khungTDD v FDD

Chng I: Tng quan v cng ngh LTE

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I.1 Gii thiu+Cng vi s pht trin cng nh i hi ca x hi ngnh khoa hc trong lnh vctruyn dn vin thng cng lun pht trin p ng nhng yu cu .+ c bit l trong x hi ngy nay nhu cu v trao i thng tin , truyn d liu,cc dch v trn cc thit b di ng liu ngy cng cao. Cc h thng thng tin di

ng 2g, 2,5g v c bit la 3g vn ang hot ng kh trn chu v ngy cng phttrin vi nhng th mnh ca mnh tuy nhin chng vn phn no cha p ngc mong i ca nhng khch hng c nhu cu s dng truyn d liu tc cao. H thng thng tin di ng s dng cng ngh LTE c pht trin s giiquyt c nhng kh khn trn.

I.2 Tng quan v cng ngh LTE

+ LTE l t vit tt ca Long term evolution miu t cng vic chun ha ca

3GPP xc nh phng thc truy nhp v tuyn tc cao mi cho h thngtruyn thng di ng.+ LTE l bc tip theo dn n h thng thng tin di ng th 4 hay cn gi l4g. h thng ny c k vng c nhng tin b vt bc v cng ngh cng nhnhng tnh nng so vi th h 3g trc .

Hnh 1 : Cu trc mng LTE

I.3 : Tnh nng v yu cu ca LTEI.3.1 Tnh nng

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Tc nh tc thi vi bng thng 20 MHz:Ti xung: 100 Mbps; Ti ln: 50 Mbps

- Dung lng d liu truyn ti trung bnh ca mt ngi dng trn 1 MHz sovi mng HSDPA Rel. 6:

- Ti xung: gp 3 n 4 ln; Ti ln: gp 2 n 3 ln.- Hot ng ti u vi tc di chuyn ca thu bao l 0 15 km/h. Vn hot

ng tt vi tc t 15 120 km/h. Vn duy tr c hot ng khi thu baodi chuyn vi tc t 120 350 km/h (thm ch 500 km/h ty bng tn)

- Bng tn s dung: Lte c th c trin khai nhiu bng tn khc nhau nh tn s 700Mhz, 900Mhz, 1800Mhz, 1900Mhz, 2300Mhz

di bng thng linh hot: c th hot ng vi cc bng 1.4Hz, 3MHz, 5 MHz,10 MHz, 15 MHz v 20 MHz c chiu ln v xung. H tr c 2 trng hp di

bng ln v bng xung bng nhau hoc khng+ LTE cung cp cc tc d liu cao hn cho c ng ln v ng xung.+ Ngoi lm tng tc s liu thc LTE cn lm gim tr gi.+ Tng cng giao din khng gian cho php tng tc s liu. LTE c xcnh trn mng truy nhp v tuyn hon ton mi da trn cng ngh OFDM chong xung v SC-FDMA cho ng ln.+ Hiu qu s dng ph tn cu OFDM c nng cao nh s dng k thut iuch bc cao 64QAM. M ha turbo, m ha xon cng vi cc k thut v tuyn

b xung nh k thut MIMO kt qu l thng lng trung bnh tng ln 5 ln so

vi HSPA.+ Mi trng ton IP. LTE l s chuyn dch ti mng li ton IP vi giao din mv kin trc n gin ha. y l bc chuyn i ca 3GPP t h thng mng liang tn ti kt hp song song trc la chuyn mch knh v chuyn mch gisang mng li chi s dng chuyn mch gi.

I.3.2 Yu cu thit k v bng tn s dng+ Cht lng dch v: H tr tnh nng m bo cht lng dch v QoS cho ccthit b. VoIP m bo cht lng m thanh tt, tr mc ti thiu (thi gian

ch gn nh khng c) thng qua cc mng chuyn mch UMTSLin kt mng: Kh nng lin kt vi cc h thng UTRAN/GERAN hin c vcc h thng khng thuc 3GPP (non-3GPP) cng s c m bo. Thi gian trtrong vic truyn ti gia E-UTRAN v UTRAN/GERAN s nh hn 300ms chodch v thi gian thc v khng qu 500ms cho cc dch v cn liHiu qu s dng ph tn caoTr c gim xung cn

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- Trn th gii c nhiu hng vin thng ln trin khai hot ng mng LTEMng NTT DoCoMo ca Nht s i tin phong khi t mc tiu khai trng dchv vo nm 2009.

Cc mng Verizon Wireless, Vodafone, v China Mobile tuyn b hp tcth nghim LTE vo nm nay. Vic trin khai c s hng tng cho LTE s bt uvo na sau ca nm 2009 v k hoch cung cp dch v s bt u vo nm 2010.-u thng ngy 8 thng 10 nm 2010 va ri, hng vin thng Ericsson Vit Nam phi hp vi Cc Tn s V tuyn in ca B Thng tin v Truyn thng trnhdin cng ngh LTE cng ngh tin 4G trc s chng kin ca i din ca Bcng cc mng di ng Vit Nam.

Chuyn gia ca Ericsson cho bit, nu nh tc ca dch v ADSL c cungcp ti Vit Nam trung bnh t 1,5Mbps 6Mbps l bng rng th vi LTE, thvn cha l g. Cng ngh TD-LTE c tc l tng ln n 110 Mbps vi cuhnh tng t .t th nghim va ri din ra bng tn 2300-2400Mhz . Kt thc cuc th

nghim tc o c tc ti xung t 80Mbps ti ln t 20Mbps. Vt xatc truy nhp ca ADSL hin nay.

1.5 qun l ti nguyn v tuyn

Nhng yu cu v qun l ti nguyn v tuyn c chia ra nh sau: h trnng cao cho cht lng dch v u cui ti u cui, h tr hiu qu cho truyndn lp cao hn, v h tr cho vic chia s ti cng nh l qun l chnh schthng qua cc cng ngh truy cp v tuyn khc nhau.

Vic h tr nng cao cht lng dch v du cui ti u yu cu ci thin sgia thch ng gia dch v, ng dng v cc iu kin v giao thc (bao gm bohiu lp cao hn) vi ti nguyn RAN v cc c tnh v tuyn.

Vic h tr hiu qu cho truyn dn lp cao hn i hi LTE RAN phi ckh nng cung cp c cu h tr truyn dn hiu sut cao v hot ng ca ccgiao thc lp cao hn qua giao tip v tuyn, chng hn nh qu trnh nn tiu IP (IP header).

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Vic h tr chia s ti v qun l chnh sch thng qua cc cng ngh truy cpv tuyn khc nhau i hi phi xem xt n vic la chn li cc c cu nhhng cc thit b u cui di ng theo cc dng cng ngh truy cp v tuyn

thch hp c ni r cng nh l h tr QoS end to end trong qu trnh chuyngiao gia cc cng ngh truy cp v tuyn.

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Chng II: Cu trc h thng

Hnh 2.1 cu trc ca mng

H thng LTE c chia lm hai phnLTE c phat trin thnh 2 phn kt hp liPhn truy nhp v tuyn mt t v h thng mng li

II.1 Truy nhp v tuyn mt t E-UTRANE-UTRAN bao gm cc eNB, cung cp cc mt phng s dng E-UTRA v giaothc iu khin mt phng giao tip i vi UE Hon ton phn phi kin trc mng truy nhp v tuyneNB c th c kt ni vi nhau bng cc phng tin ca giao din X2 X2 h tr di ng tng cng, qun l nhiu gia cc t bo, v cc chc nngSONeNB c kt ni bng phng tin ca giao din S1 cho Evolved Packet Core(EPCII.1.1 E NodBENodB ( Evoled NodeB)

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L trm gc c tng cng mi, c tn l Evolved NodeB da trn chun 3GPP.N l mt BTS c tng cng cung cp giao din khng gian LTE v thc hinqun l ti nguyn v tuyn cho h thng truy nhp tin tin. chc nng caENodB : Chc nng qun l ti nguyn v tuyn

Nn IP header v m ho dng d liu ngi s dng

Qun l d liu truyn ti mt cch t lpBo m cht lng dch vThc hin cc cuc chuyn giao vi cc UEII.2 H thng mng li EPC (evoled packet core)c imH thng mng li ca LTe ci tin v pht trin ch s dng duy nht mt

phng thc l chuyn mch gi. V truyn d liu ,xc nh v tr thu bao bngphng thc nh tuyn IP trong ton b h thngKin trc mng c rt gn hn so vi mng 3G gp phn lm gim gi thnhkhi trin khai mng.Chc nng ca cc khiII.2.1 PDN GatewayPDN GW cung cp kt ni cho UE ti cc mng d liu gi bn ngoi ti cc imvo ra ca lu lng cho UE. Mt UE c th ng thi kt ni vi nhiu hn mtPDN GW truy nhp nhiu PDN. Chc nng ca PDN GW gm c:Qun l mt qu a ch IP v cp pht cc a ch IP cho cc UE+ Thc hin s cng bc chnh sch (Policy enforcement).

+ Lc gi cho mi user.(Per-user based packet filtering (by e.g. deep packetinspection)+ H tr tnh cc.+ Ngn chn hp php (Lawful Interception)+ Packet screening+ nh v a ch UE IP+ Chc nng DHCP (Dynamic Host Configuration Protocol)+ Transport level packet marking in the uplink and downlink, e.g. setting theDiffServ Code Point, based on the QCI of the associated EPS bearer

II.2.2 Cng phc v :Serving Gateway(S GW)L mt node kt thc trong giao din hng ti EUTRAN. Chc nng ca SGW

bao gm:Truyn ti d liu ngi dng gia mng v tuyn v mng li thong qua giao thcGTP+ SGW nh tuyn v hng cc gi d liu d liu ngi s dng.+ EUTRAN ngng b m gi ng xung v bt u mng thc y th tc yu

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cu dch v.+ Khi cc UE trng thi ri, SGW kt thc ng d liu Downlink v kch hottm gi khi d liu downlink chuyn ti UE.+ Qun l v lu tr cc vn cnh ca UE,+ Thc hin sao chp ca lu lng s dng trong trng hp ngn chn hp

php.II.2.3 Thc th qun l di ng MME (Mobility Management Entity)MME l node iu khin quan trng ca mng truy nhp LTE. MME qun l tnhlu ng, xc nhn UE v nhng tham s bo mt. Chc nng ca MME bao gm:+ Bo hiu NAS (Non Access Stratum) hon thnh ti MME, v n cng chutrch nhim v s pht sinh v s nh v ca s nhn dng tm thi cc UE.+ MME cung cp chc nng iu khin phng cho tnh lu ng gia LTE vmng truy nhp 2G/3G.+ Trng thi UE ri Idle theo di v kh nng lin lc (bao gm iu kin v thc

hin cc chuyn tip tm gi).+ Theo di qun l danh sch vng.+ Kim tra tnh xc thc ca UE n trm trn dch v ca nh cung cp PLMN vgim st vic thi hnh s gii hn Roaming cho UE.+ La chn GW (s la chn Serving GW v PDN GW).+ La chn MME cho chuyn giao khi thay i MME.+ La chn SGSN chuyn giao ti cc mng truy nhp 2G, 3G, 3GPP..+ N chu trch nhim chng thc cc user (bng cch tng tc vi HSS HomeSubscriber Service).+ MME l im cui cng trong mng thc hin vic dch mt m, bo v ton

din cho bo hiu NAS v vn hnh qun l kho bo mt.

II.3Cc giao din lin ktGiao din : S1Giao din S1 l giao din phn cch gia E-UTRAN v EPC. N c chia thnh

hai phn: S1-U, c th mang theo d liu giao thng gia cc-eNode B v cc GWphc v, v cc S1-MME, m l mt giao din bo hiu ch gia cc-eNode B vcc MMEGiao din X2 : Giao din X2 l giao din gia cc eNode-B, gm hai phn:-X2 Cl cc mt phng iu khin giao din gia eNode-B, trong khi U-X2 l giao dinngi dng my bay gia eNode-B. Ngi ta cho rng lun lun tn ti mt giaodin X2 gia eNode-B rng cn phi giao tip vi nhau, v d, h tr bn giao

Giao dn S3: - l giao din gia S GW v cng SGSN ca mng 2G,3G .N chophp ngi s dng v trao i thng tin ghi tn cho lin mng di ng 3GPP truycp trng thi nhn ri v / hoc hot ng

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Hnh 2.2:chc nng phn chia gia E-UTRAN v li tin ha gi

II.4Giao thc giao din v tuynD liu c truyn trn ng xung di dng cc gi IP trn mt trong

nhng ti tin SAE (SAE bearers). Trc khi truyn i qua giao din v tuyn,nhng gi IP n (incoming IP packets) s i qua nhiu phn t, c tng ktdi y v c m t chi tit hn trong nhng phn sau:

iu khin ti nguyn v tuyn Radio Resource Control (RRC): Cc lp RRCthc hin chc nng kim sot bao gm duy tr mt phng, nhn tin v pht hnhx l kt ni di ng, bo mt, v qun l QoS.

Giao thc hi t s liu gi (Packet Data Convergence Protocol -PDCP): thchin vic nn tiu IP (IP header) lm gim s lng bit cn thit cho victruyn dn thng qua giao din v tuyn.

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iu khin lin kt v tuyn (Radio Link Control - RLC): m nhim vic phnon / ghp ni, iu khin vic truyn li, v phn pht ln cc lp cao hn theoth t. Khng ging nh WCDMA, giao thc RLC c nh v trong eNodeB vch c mt loi node n trong kin trc mng truy nhp v tuyn LTE (LTE radio

access network architecture). RLC cung cp cc dch v cho PDCP di dng ccti tin v tuyn. Ch c mt phn t RLC trn mt ti tin v tuyn c cu hnhcho mt thit b u cui di ng.iu khin truy cp mi trng (Medium Access Control - MAC): iu khinvic truyn li hybrid-ARQ v hoch nh ng ln, ng xung. Chc nnghoch nh c nh v trong eNodeB, v n ch c mt phn t MAC cho mt t

bo, cho c ng ln v ng xung. Phn giao thc hybrid ARQ c mt trongc u cui pht v thu ca giao thc MAC. Khi MAC cung cp cc dch v cho

RLC di dng cc knh logic.Lp vt l (Physical layer PHY): iu khin vic m ha / gii m, iu ch /gii iu ch, nh x a anten (multi antenna mapping), v cc chc nng lp vtl tiu biu khc. Lp vt l cung cp dch v cho lp MAC di dng cc knhchuyn ti (transport channels).

Hnh 2.3 mi lien h gia cc knh theo dng xung

Hnh 2.4 ng ln

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II.5 Knh chuyn tiKnh chuyn ti gim phc tp ca kin trc giao thc LTE, s lng cc knh chuyn ti gim. iu ny ch yu l do tp trung vo chia s knh hot ng, tc l khng c

knh chuyn dng c s dng na.II.5.1 ng xung knh chuyn ti gm:Knh qung b Broadcast Channel (BCH): c mt nh dng truyn ti cnh, c cung cp bi cc c tnh k thut. N c dng cho vic truyn dnnhng thng tin trn knh logic BCCHKnh Paging Paging channel (PCH): c dng cho vic paging thng tin trnknh logic PCCH. Knh PCH h tr vic thu nhn khng lin tc (discontinousreception DRX) nhm cho php thit b u cui di ng tit kim nng lng

pin bng cch ng (sleeping) v ch thc (wake up) khi nhn PCH ti nhng thiim xc nh trc

Knh multicast Multicast Channel (MCH): c dng h tr MBMS vc c trng bi nh dng truyn ti bn tnh v hoch nh bn tnh (semi-static transport format and semi-static scheduling). Trong trng hp truyn dnnhiu t bo (multi-cell transmission) s dng MBSFN, cu hnh nh dng truynti v hoch nh c iu phi gia nhng t bo lin quan trong truyn dnMBSFNKnh chia s ng xung Downlink Shared Channel (DL-SCH): l knh

truyn ti c dng cho truyn dn d liu ng xung trong LTE.II.6.2Knh chuyn ti ng ln.

Knh chia s ng ln Uplink shared channel (UL-SCH):Knh truy cp ngu nhin.Random Access Channel (RACH)Cc th tc RACH c s dng trong bn trng hp:+ u tin truy cp t trng thi b ngt kt ni (RRC_IDLE) hay li v tuyn+ Chuyn giao i hi th tc truy cp ngu nhin+ DL hoc UL n d liu trong qu trnh RRC_CONNECTED sau khi UL PHY mt ng b ha (c th do tit kim in nng hot ng)

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+UL d liu n khi khng chuyn yu cu lp k hoch (PUCCH) cc knh csn

II.6 Knh logicChc nng ca knh logic l cung cp cc dch v cho MAC

Knh logic c phn ra lm hai loi l knh iu khin v knh lu lngII.6.1 Knh logic iu khin bao gmKnh iu khin qung b (Broadcast Control Channel - BCCH): c s dngcho vic truyn dn thng tin iu khin h thng t mng ti tt c cc thit bu cui di ng trong mt t bo. Trc khi truy nhp vo h thng, mt thit bu cui di ng cn phi c nhng thng tin c truyn trn knh BCCH tm ra cch thc h thng c cu hnh, v d nh bng thng ca h thng.+ Knh tm gi (Paging Control Channel PCCH): c s dng cho vic tmgi ca cc thit b u cui di ng m mng khng bit c v tr ca n vmc t bo (cell level) v v vy tin nhn tm gi cn c truyn trong nhiu t

bo+ Knh iu khin dnh ring (Dedicated Control Channel DCCH): c dngcho vic truyn dn thng tin iu khin ti hoc t thit b u cui di ng. Knhny c s dng cho vic cu hnh ring l tng thit b u cui di ng v dnh nhng tin nhn chuyn giao khc nhau.

+Knh iu khin multicast (Multicast Control Channel - MCCH): c dng chovic truyn dn thng tin iu khin c yu cu cho vic tip nhn ca MTCH

II.6.2 knh logic lu lngKnh lu lng bao gm.+Knh lu lng dnh ring (Dedicated Traffic Channel - DTCH): c dng chovic truyn d liu ngi dng n hoc t mt thit b u cui di ng. y l 1loi knh logic c dng truyn d liu ngi dng ng ln v ng xung

phi-MBMS (non-MBMS).+Knh lu lng multicast (Multicast Traffic Channel MTCH): c dng chotruyn dn ng xung nhng dch v MBMSII.7 knh vt l

Chc nng ca knh vt lII.7.1 ng xung bao gm+ Knh pht vt l :Physical Broadcast Channel (PBCH) y knh vt l mang hthng thng tin cho cc UE yu cu truy cp mng+ Knh ch tiu iu khin vt l Physical Control Format Indicator Channel(PCFICH)

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+ Knh iu khin vt l ng xung Physical Downlink Control Channel(PDCCH). Knh ny c nhim v l lp lch thong tin.+ Knh ch nh Hybrid ARQ Physical Hybrid ARQ Indicator Channel (PHICH)knh ny c s dng bo co tnh trng Hybrid ARQ.+ Knh chia s ng xung Physical Downlink Shared Channel (PDSCH) Knh

ny c s dng cho cc chc nng unicast v phn trang.+ Physical Multicast Channel (PMCH) knh ny mang thng tin cho cc mc chmulticast+ Physical Control Format Indicator Channel (PCFICH) : knh ny cung cp thngtin cho php cc UE gii m cc PDSCH.II 7.2 ng xung ca knh vt l+ Knh iu khin ng ln Physical Uplink Control Channel (PUCCH) n cchc nng l gi v nhn Hybrid ARQ+ Knh chia s ng ln Physical Uplink Shared Channel (PUSCH) y knh vt

l c tm thy trn cc ng ln LTE l bn sao ng ln ca PDSCH+ Knh truy nhp ngu nhin Physical Random Access Channel (PRACH) knhny c s dng cho chc nng truy cp ngu nhin

Chng III : Truy nhp v tuyn

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Chng ny s gip chng ta hiu c cc phng thc truy nhp v tuyn camng.

Cng ngh LTE h tr truy nhp dng ln v ng xung theo hai phng thckhc nhau.ng ln s dng phng thc a truy nhp sng n SC-FDMA

ng xung s dng phng thc a truy nhp sng mang OFDMA

Hnh 3.1 OFDM v SC-FDMA

III.1 TRuy nhp ng xungIII.1.1 Khi qut v cng nghOFDM l t vit tt ca Orthogonal Frequency DivisionMultiplexing hay cn gi l k thut a iu ch a sng mang trc giao.OFDM l mt phng php truyn kh phc tp trn knh vt l, nguyn l c bn

ca phng php l s dng k thut a sng mang truyn mt lng ln k tti cng mt thi im. S dng k thut OFDM c rt nhiu u im, l hiuqu s dng ph rt cao, kh nng chng giao thoa a ng tt (c bit trong hthng khng dy) v rt d lc b nhiu (nu mt knh tn s b nhiu, cc tn sln cn s b b qua, khng s dng). Ngoi ra, tc truyn ti ln v ti xungc th thay i d dng bng vic thay i s lng sng mang s dng. Mt uim quan trng ca h thng s dng a sng mang l cc sng mang ring c th

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hot ng tc bit nh dn n chu k ca k t tng ng s c ko di .V d, nu mun truyn vi tc l hng triu bit trn giy bng mt knh n,chu k ca mt bit phi nh hn 1 micro giy. iu ny s gy ra kh khn chovic ng b v loi b giao thoa a ng. Nu cng lng thng tin trn ctri ra cho N sng mang, chu

k ca mi bit s c tng ln N ln, lc vic x l vn nh thi, a ngs n gin hn.III.1.2 OFDM trong LTE

H thng truyn dn ng xung ca LTE da trn cng ngh OFDM. Nh bit th OFDM l mt h thng truyn dn ng xung hp dn vi nhiu l dokhc nhau. V thi gian k t OFDM tng i di trong vic kt hp vi mt tint chu trnh, nn OFDM cung cp mnh chng li s la chn tn s knh(channel frequency selectivity). Mc d trn l thuyt th vic sai lch tn hiu do

knh truyn chn lc tn s c th c kim sot bng k thut cn bng ti phathu, s phc tp ca k thut cn bng bt u tr nn km hp dn trong vic trinkhai i vi nhng thit b u cui di ng ti bng thng trn 5 MHz. V vy mOFDM vi kh nng vn c trong vic chng li fading la chn tn s s trthnh s la chn hp dn cho ng xung, c bit khi c kt hp vi ghpknh khng gian (spatial multiplexing).

Hinh 3.2 s thi gian v tn s ca tn hiu OFDM

Mt s li ch khc ca k thut OFDM bao gm:

OFDM cung cp kh nng truy nhp vo min tn s, bng cch thit lp mt tdo b sung (degree of fredom) cho khi hoch nh ph thuc knh truyn(channel dependent scheduler) so vi HSPA.

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OFDM d dng h tr cho vic phn b bng thng mt cch linh hot, bng cchbin i bng tn c s thnh cc sng mang ph truyn i. Tuy nhin ch rng l vic h tr nhiu phn b ph i hi cn phi c b lc RF linh hot(flexible RF filtering) khi th s truyn dn chnh xc l khng thch hp.

Tuy nhin, vic duy tr cu trc x l bng tn c s ging nhau (the samebaseband processing structure), khng ph thuc bng thng s ni lng vic trinkhai u cui.

H tr d dng cho vic truyn dn broadcast/mulitcast, khi m nhng thng tinging nhau c truyn i t nhiu trm gc.

Ngoi ra OFDM c th c s dng trong c hai nh dng FDD v TDD y lmt li th trong vic trin khai mng sau ny.

Ngoi ra, OFDM c th c s dng trong c hai nh dng FDD v TDD. iuny tr thnh mt li th b sung.

Cc tn hiu OFDM c s dng trong LTE bao gm ti a l 2048 sng mangph khc nhau c mt khong cch l 15 kHz. Mc d n l bt buc i vi ccin thoi di ng c kh nng c th nhn c tt c 2048 sng mang, khng

phi tt c cn phi c truyn qua cc trm c s m ch cn c th h trvic truyn ca 72 sng mang. Bng cch ny, tt c cc in thoi di ng s cth kt ni vi bt k trm gc.Trong thi hn tn hiu OFDM c th la chn gia ba loi iu ch:

1. 1: QPSK (= 4QAM) 2 bits per symbol2. 16QAM 4 bits per symbol3. 64QAM 6 bits per symbol

Hnh 3.2: S to tn hiu OFDM

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Cc nh dng chnh xc c chn ty thuc vo iu kin hin hnh. Cc hnhthc thp hn iu ch, (QPSK) khng yu cu nh mt tn hiu ln t l nhiunhng khng c kh nng gi d liu nhanh. Ch khi c mt tn hiu ting n

t l th t cao hn nh dng iu ch c th c s dng.Dng xung sng mang v khi ti nguyn

Trong ng xung, cc sng mang con c chia thnh khi ti nguyn. iu nycho php h thng c th compartmentalise cc d liu qua con s tiu chunca cc sng mang con.Ti nguyn khi gm 12 sng mang con, khng phn bit tn hiu bng thng tngth LTE. N cng bao gm mt khe cm trong khung thi gian. iu ny c nghal khc nhau bng thng tn hiu LTE s c cc s khc nhau ca khi ti nguyn.

Hnh 2.3 Khi ti nguyn vi 12 sng mang ph

III.2: Truy nhp ng ln

i vi cc ng ln LTE, mt khi nim khc nhau c s dng cho cc kthut truy cp. Mc d vn cn s dng mt dng ca cng ngh OFDMA, victhc hin c gi l Single Carrier Frequency Division Multiple Access (SC-FDMA). Hay cn gi l a truy nhp phn chia theo tn s n sng mang.Mt trong nhng thng s quan trng nh hng n tt c cc in thoi di ngl thi gian sng ca pin. Mc d hiu sut pin c ci thin tt c cc thi gian,n vn cn cn thit m bo rng in thoi di ng s dng nng lng pin tnht c th. Vi cc b khuch i cng sut RF truyn tn hiu tn s v tuyn

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thng qua ng-ten cc trm c s ang c cc mt hng in cao nht trongcc in thoi di ng, n l cn thit m n hot ng ch hiu qu cng tt.iu ny c th b nh hng bi cc hnh thc iu ch tn s v tuyn v nhdng tn hiu.Tn hiu c mt nh cao t l trung bnh v yu cu khuch i tuyn tnh

khng vay c vic s dng cc b khuch i cng sut hiu qu RF. Kt qu ln l cn thit s dng mt phng thc truyn ti m l gn mt mc cngsut khng i khi hot ng. Tht khng may OFDM c mt nh cao t l trung

bnh. Trong khi y khng phi l vn i vi cc trm gc ni quyn lckhng phi l mt vn c th, n l khng th chp nhn cho cc in thoi ding. Kt qu l, LTE s dng mt chng trnh iu ch c gi l SC-FDMA -Single Carrier Frequency Division Multiplex m l mt dng lai. iu ny kt hpnh cao thp t l trung bnh c cung cp bi h thng n vn chuyn vi skin cng can thip a v tn s sng mang con linh hot phn b m OFDM

cung cp.Vic s dng phng php a truy nhp phn chia theo tn s n sng mang scho PAPR nh hn so vi OFDM dn n tiu th cng sut thit b u cui thn tng tnh di ng cho thit b. do sc- fdma truyn mt lung duy nht ciu ch vo sng mang ph nn c PAPR thp hn. (t l cng sut trung bnh)Tn hiu SC-FDMA c to ra bng k thut tri ph DFT-OFDM (DFT-s-OFDM)

Hnh 3.3 s khi DFT-S- OFDM

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III.3: cu trc Hybrid ARQ vi kt hp mmHybrid automatic repeat request (HARQ ) c ch yu cu lp li t ng.

Hybird ARQ vi kt hp mm trong LTE p ng mt mc ch tng tvi c ch hybird-ARQ trong HSPA l cung cp sc chu ng chng li

cc li truyn dn. N cng l mt cng c nng cao nng sut. Khi m nhngc ch truyn li hybird-ARQ l nhanh, nhiu dch v cho php mt hoc nhiu struyn li, bng cch thit lp mt c ch iu khin tc n (vng lp kn) (animplicit (closed loop) rate-control mechanism). Tng t vi phng php trongHSPA, giao thc hybrid-ARQ l mt phn ca lp MAC, trong khi hot ng kthp mm c iu khin bi lp vt l.

R rng, hybrid ARQ khng c p dng cho tt c cc dng lu lng.

V d, truyn dn broadcast, khi m nhng thng tin ging nhau c dnh chonhiu ngi dng, thng thng khng ph thuc vo hybrid ARQ. V vy, hybridARQ ch c h tr cho DL-SCH v UL-SCH.

Giao thc hybrid ARQ trong LTE ging vi giao thc tng ng c sdng cho HSPA, l vic s dng nhiu tin trnh stop-and-wait song song.Trong lc tip nhn nhng khi truyn ti, u thu s tm cch gii m khi truynti v khai bo cho u pht v kt qu ca hot ng gii m thng qua mt bit

n ACK/NAK ch th vic gii m c thnh cng hay khng hoc truyn likhi truyn ti nu c yu cu. Nhng chi tit khc v truyn dn ACK/NAKtrong ng xung v ng ln s c tm thy trong chng 4. ti thiu hachi ph, mt bit n ACK/NAK c s dng. R rng, u thu phi bit bitACK/NAK thu c c lin kt vi tin trnh hybid-ARQ no. Hn na, iuny c gii quyt bng cch s dng cng mt phng php nh trong HSPA

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khi thi im ca ACK/NAK c s dng kt hp ACK/NAK vi mt tintrnh hybrid-ARQ no . iu ny c minh ha trong hnh 3.6. Ch rng, ivi trng hp hot ng TDD, mi quan h v thi gian gia vic tip nhn dliu trong mt tin trnh hybrid-ARQ no v vic truyn dn ACK/NAK th

khng b nh hng bi s phn b ng ln/ng xung.

Tng t vi HSPA, mt giao thc khng ng b l c s cho hot nghybrid-ARQ ng xung. V vy, s truyn li ng xung c th xy ra ti mithi im sau khi vic truyn dn c khi to v mt con s tin trnh hybrid-ARQ tng minh (an explicit hybrid-ARQ process number) c s dng chth tin trnh no ang c nh a ch (addressed). S truyn li ng ln, mtkhc, li da trn mt giao thc ng b v s truyn li xy ra ti mt thi gian

xc nh trc sau khi khi to qu trnh truyn dn v s tin trnh (processnumber) c th nhn c hon ton. Hai trng hp c minh ha trong hnh3.5. Trong giao thc hybrid-ARQ khng ng b, s truyn li trn l thuyt choch nh tng t vi vic khi to qu trnh truyn dn. Mt khc trong giaothc ng b, thi im truyn li c c nh mt ln khi khi u qu trnhtruyn dn c hoch nh, phi c tnh n cho hot ng hoch nh. Tuynhin, ch rng scheduler s phn bit t phn t hybrid-ARQ trong eNodeB ucui di ng no s thc hin truyn li hay khng.

Hnh 3.5 Giao thc hybrid-ARQ ng b v khng ng b.

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III.4: a truy nhp MIMO

t c tc truyn v nhn d liu t c cao nh vy th cng nghLTE cng yu cu nhng ci tin trong phn angten .

Cng ngh MIMO l mt gii php ph hp cho nhng yu cu .

Hnh 3.4 v d v cng ngh mimoIII.4.1MIMO (multi input multi output) hay cn gi l k thut s dng nhiu ng ten

pht v nhiu ng ten thu truyn v nhn d liu.MIMO l mt phn tt yu ca LTE t c cc yu cu y tham vng vthng lng v hiu qu tri ph. MIMO cho php s dng nhiu anten my phtv my thu.Vi hng DL, MIMO 2x2 (2 anten thit b pht, 2 anten thit bthu) 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 dngMIMO. 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 nghLTE.

Ghp knh khng gian (Spatial Multiplexing): Ghp knh khng gian cho phppht cc chui d liu khc nhau ng thi nhm tn dng trit ti nguyn sngca knh v tuyn. Cc chui d liu ny c th l ca mt ngi dng n l(single user MIMO hay SU-MIMO) hay nhiu ngi dng (Multi User MIMO hayMU-MIMO).

Trong v d trn mi anten pht s pht i mt chui d liu khc nhau. Mi antenthu c th nhn nhiu chui d liu t c hai anten pht.

Cckhi nimc bncaMIMOs dngvic tuyn truyntn hiua ngchin din trongtt c ccthng tin lin lctrn mt t.

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MIMO ang c s dng ngy cng nhiu cng ngh tc d liu cao bao gmc Wi-Fi v cc cng ngh khng dy v di ng khc cung cp mc cithin hiu qu. V c bn MIMO s dng nhiu anten trn my thu v my pht s dng cc hiu ng a ng dn m lun lun tn ti truyn ti d liu bsung, hn l gy nhiu.

i vi ng xung, mt cu hnh ca hai ng-ten truyn ti cc trm c s vhai ng-ten nhn c trn thit b u cui di ng c s dng lm c s, mcd cu hnh vi bn anten cng ang c xem xt.Hai nh dng chnh cho MIMO c a ra di y:

* a dng khng gian: khng gian a dng c s dng trong ngha ny hphn thng cp n truyn v nhn s a dng. Hai phng php c s dng cung cp nhng ci tin trong cc tn hiu t l nhiu v h c c trng bngcch ci thin tin cy ca h thng i vi cc hnh thc khc nhau ca m dn.

* khng gian ghp: Hnh thc MIMO c s dng cung cp thm d liudung lng bng cch s dng cc ng dn khc nhau thc hin giao thngkhc, tc l tng kh nng thng lng d liu.

III.5 cu trc khung TDD va FDD

Trong k thut LTE, kch thc ca cc phn t trong min thi gian c th hinnh mt s n v thi gian T = 1 / (15.000 x 2048) giy. Khi khong cch giacc sng mang con l f = 15kHz, Ts c th c coi l thi gian ly mu ca mtmy pht da trn OFDM FFT / thc hin tip nhn vi NFFT kch thc FFT =

2048. Lu rng y ch cho mc ch k hiu, nh kch c FFT khc nhau ch tr ty thuc vo bng thng truyn ti. Mt tp hp cc thng s cho bngthng truyn in hnh cho LTE trong downlink c th hintrong 6,2 Bng, nim khong cch gia cc sng mang con l f = 15kHz. Cc kch thc FFT tngvi bng thng truyn ti, khc nhau, 128-2048. Vi f = 15kHz, tn s ly mu,

bng vi f x NFFT, l mt / nhiu hoc tiu nhiu ca UTRA HSPA tc chip3.84MHz. Bng cch ny, a UTRA / HSPA / thit b u cui LTE c th cthc hin vi mt mch ng h duy nht. Ngoi khong cch sng mang con15kHz, mt khong cch sng mang con gim 7.5kHz c nh ngha choMBSFN t bo, cung cp mt thi gian OFDM biu tng ln hn c kh nngchng ly lan chm ln lin quan n vic truyn ti MBSFN. Tr khi c quy nhkhc, chng ti s gi f = 15kHz trong cc cuc tho lun sau.

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Bng . Thng s tiu biu cho truyn dn ng xungBng thng[MHz]

1.4 3 5 10 15 20

Bng thng bchim [MHz]

1.08 2.7 4.5 9.0 13.5 18.0

Bng tn bo v[MHz]

0.32 0.3 0.5 1.0 1.5 2.0

Tn s ly mu[MHz]

1.921/2x3.84

3.84 7.682x3.84

15.364x3.84

23.046x3.84

30.728x3.84

Kch thc FFT 128 256 512 1024 1536 2048S song mang ph 72 180 300 600 900 1200S khi tinguyn

6 15 25 50 75 100

Trong min thi gian, cc ng xung v ng c t chc thnh cc khungthanh vi thi gian T f = 307200 Ts = 10 ms. i vi s linh hot, LTE h tr chai ch FDD v TDD. Hu ht cc thit k tham s c ph bin cho FDD v

TDD gim s phc tp thit b u cui v ti a ha vic ti s dng gia ccthit k ca cc h thng FDD v TDD. Theo , LTE h tr hai loi cu trckhung: khung cu trc loi 1 cho ch FDD v cc loi cu trc khung 2 cho ch TDD

III.5.1 Cu trc khung loi 1

Khung c cu loi 1 p dng cho c hai song song cng FDD v mt na. C baloi khc nhau ca cc n v quy nh cho cu trc khung, minh ha trong hnh6.8. Ngi nh nht c gi l mt khe, l chiu di Tslot = 15360 Ts = 0,5

ms. Hai khe cm lin tip c nh ngha nh l mt subframe chiu di 1 ms, v20 khe, s t 0 n 19, to thnh mt khung pht thanh ca 10 ms. Knh ph thucvo lch trnh v thch ng lin kt hot ng trn mt mc subframe. V vy,thi gian khung ph tng ng vi TTI ng xung ti thiu, l thi hn ms 1,so vi TTI 2 ms cho HSPA v ti thiu l 10 ms TTI cho UMTS. Mt TTI ngnhn l thch ng lin kt nhanh chng v c th lm gim s chm tr v khaithc tt hn cc knh khc nhau thi gian qua knh ph thuc vo lch trnh.

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Hnh 6.8 Khung c cu loi 1.

i vi FDD, uplink v downlink truyn c phn tch trong lnh vc tn s, mivi 10 sng mang ph. Trong hot ng bn song cng FDD, cc UE khng thtruyn v nhn cng mt lc trong khi khng c hn ch nh y song cngFDD. Tuy nhin, song cng FDD cn thit b u cui cht lng cao v t tinsong RF-b lc uplink ring v cc knh ng xung, trong khi bn song cngFDD cho php chia s phn cng gia ng ln v ng xung, trong cungcp mt chi ph tit kim ti cc chi ph ca vic gim tc d liu ca mt na.Half-duplex UE FDD cng c coi l mt gii php tt nu tch song giauplink v downlink truyn l tng i nh. Trong trng hp ny, bn song cng

FDD l phng php thch hp gim thiu s can thip cho gia truyn vnhn cc chui.

III.5.2 C cu khung Loi 2

Khung c cu loi 2 c p dng cho cc ch TDD. N c thit k cngtn ti vi cc h thng di sn nh l tiu chun TD-SCDMA da trn 3GPP.

Nh trong hnh 6,9, mi khung hnh v tuyn ca cc loi cu trc khung 2 lchiu di T f = 30720 Ts = 10 ms, trong bao gm hai khung hnh mt na

chiu di mi 5 ms. Mi na khung hnh c chia thnh nm khung ph vi di mi khung la 1 ms.C khung ph c bit bao gm ba lnh vc: ng xung khe thi gian th im(DwPTS), gia on bo v (GP), v ng ln khe thi gian th im (UpPTS).Cc lnh vc ny c quy nh ti TD-SCDMA v c duy tr ch TDDLTE cung cp bo v thi gian ln cho cc thit b chuyn i gia phtv thu.

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VIN I HC M H NIKHOA CNG NGH IN T- THNG TIN

BO CO THC TP TT NGHIP

Kha 2007-2011/ h i hc chnh quy

ti: Tm hiu v cng ngh mng LTE

Thy hng dn : Nguyn Hi ngSinh vin thc hin: Ng Vn TinLp : K 10A

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H ni thng 2/ 2011