Kiến trúc và giao thức HSPA & HSDPA

8/2/2019 Kin trc v giao thc HSPA & HSDPA

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Kin trc v giao thc HSPAHSPA (High Speed Packet Access) truy nhp gi tc cao l cng ngh c trin khaitrn nn WCDMA. HSPA bao gm :

HSDPA (High Speed Downlink Packet Access) truy nhp gi hng xung tc

cao. HSUPA (High Speed Uplink Packet Access) truy nhp gi hng ln tc cao. Vit Nam, sau khi 3G c php trin khai th cng ngh HSPA cng c nhanh chngpht trin. Mt sn phm in hnh s dng HSPA l cc USB MODEM giao tip vi mytnh qua cng usb, c kh nng kt ni internet qua sng in thoi, h tr download vupload d liu vi tc cao.

KIN TRC V GIAO THC HSPA

Ni dung chnh ca phn ny l nhng tc ng ca [[HSDPA]] v HSUPA ti mng vtuyn v kin trc giao thc cng nh nhng chc nng phn t mng v cc giao tip.

1.Kin trc qun l ti nguyn v tuynChc nng qun l ti nguyn v tuyn (RRM : Radio Resource Management) vi HSDPAv HSUPA c nhiu s thay i so vi phin bn R99. Trong phin bn R99, iu khinlp lch biu hon ton da trn b iu khin mng v tuyn (RNC : Radio NetworkController) khi trong trm gc (BTS hoc trong thut ng 3GPP l Node B) phn ln cmt chc nng lin quan n iu khin cng sut. SNRC (Serving RNC ) l b phn ckt ni ti mng li s iu khin lp lch biu cho knh ring (DCH: Dedicated Channel) vb phn ang c kt ni ti trm BTS s iu khin knh chung (FACH: Forward AccessChannel).V chc nng lp lch biu c chuyn ti BTS nn c mt s thay i trong ton b kintrc RRM. SNRC vn s iu khin vng chuyn giao v s l ni quyt nh thng s chtlng dch v (QoS : Quality of Service) ph hp. i vi HSDPA cc trng thi c n

gin ha v khng c chuyn giao mm cho d liu HSDPA, khng cn chy d liu ngidng trn nhiu giao tip Iur v Iub.

Kin trc qun l ti nguyn v tuyn trong phin bn R99.png2.Kin trc giao thc ngi dng HSDPA v HSUPAKin trc c th c xc nh bao gm phn ngi dng, x l d liu ngi dng vphn iu khin. Lp iu khin ti nguyn v tuyn (RRC : Radio Resource Control) trongphn iu khin x l tt c bo hiu lin quan n cu hnh cc knh, qun l tnh ding...m ngi dng khng thy c.

Kin trc giao thc giao tip v tuyn phin bn R99Giao thc hi t d liu gi (PDCP : Packet Data Convergence Protocol) c chc nngchnh l nn header v khng lin quan n dch v chuyn mch knh. Nn header l cnthit v header khng nn trong giao thc IP c kch thc ln gp 2 ti 3 ln so vi kchthc header nn.

iu khin kt ni v tuyn (RLC: Radio Link Control) iu khin phn mnh v truyn licho c d liu ngi dng v d liu iu khin. RLC c th hot ng 3 ch khc
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nhau l :

Ch trong sut : khng c overhead c thm vo. Ch ny khng thch hpkhi knh truyn ti ca HSDPA v HSUPA c s dng. Ch khng c bo nhn : khng truyn li lp RLC. Ch ny c dng vinhng ng dng cho php s mt gi nh VoIP nhng khng cho php tr . Ch bo nhn : c truyn li lp RLC. Ch ny ph hp vi nhng ng dngyu cu tt c gi tin truyn i m khng c s tht thot.Lp iu khin truy nhp mi trng (MAC : Medium Access Control) trong phin bn R99tp trung vo phn b knh lun l v iu khin u tin cng nh s la chn tc dliu, s la chn nh dng truyn ti. Chuyn mch knh truyn ti cng l mt chc nnglp MAC.

Kin trc giao tip v tuyn HSDPA v HSUPA cho d liu ngi dngC HSDPA v HSUPA u a ra nhng yu t mi trong kin trc. Hnh 2.3 minh ha choton b kin trc giao tip v tuyn cho d liu ngi dng HSDPA v HSUPA, phn tm l nhng phn t giao thc mi c lin quan n d liu ngi dng. Phn iu khinbo hiu (khng c trong hnh 2.3) c th kt ni d dng ti RLC v mang bo hiu i ctrn DCH v trn HSDPA/HSUPA. i vi d liu ngi dng, PDCD iu khin nnheader IP. Phn t PDCD v RLC trong hnh v ch ra kh nng nhng dch v c th chysong song.Chc nng lp lch biu BTS l mt chc nng lp MAC v c mt phn t giao thc mil MAC-hs (high speed) trong BTS. Hnh 2.4 minh ha mt phn ca kin trc giao thcphn ngi dng da theo nhng tnh nng b sung ca HSDPA v v tr ca chng trongphn t mng. RNC iu khin MAC-d (delicate) nhng chc nng duy nht cn li lchuyn mch knh truyn ti v tt c nhng chc nng khc nh lp lch biu v x l utin c chuyn ti MAC-hs. Cn ch rng lp trn lp MAC (c th l lp RLC)

phn ln vn khng thay i ngoi tr mt vi s ti u ha cho cc dch v thi gian thcnh VoIP. Ngay c nu HSDPA c truyn li lp vt l th lp RLC vn c th iu khintruyn li khi hot ng ca lp vt l c s c hay trng hp c bit l kt ni c nhngs bin i nh cell HS-DSCH thay i. y l ch hot ng c bo nhn ca RLC.

Kin trc giao thc ngi dng HSDPA
http://vi.wikipedia.org/wiki/T%E1%BA%ADp_tin:Ki%E1%BA%BFn_tr%C3%BAc_giao_th%E1%BB%A9c_ng%C6%B0%E1%BB%9Di_d%C3%B9ng_HSDPA.jpghttp://vi.wikipedia.org/wiki/T%E1%BA%ADp_tin:Ki%E1%BA%BFn_tr%C3%BAc_giao_th%E1%BB%A9c_ng%C6%B0%E1%BB%9Di_d%C3%B9ng_HSDPA.jpghttp://vi.wikipedia.org/wiki/T%E1%BA%ADp_tin:Ki%E1%BA%BFn_tr%C3%BAc_giao_ti%E1%BA%BFp_v%C3%B4_tuy%E1%BA%BFn_HSDPA_v%C3%A0_HSUPA_cho_d%E1%BB%AF_li%E1%BB%87u_ng%C6%B0%E1%BB%9Di_d%C3%B9ng.jpg


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i vi HSUPA, c mt phn t lp MAC mi c thm vo BTS nh trong hnh 2.5. ucui cng c phn t lp MAC mi l MAC-es/s thay th phn chc nng lp lch biu chuyn ti node B v n da trn s iu khin thng tin t RNC v mt yu cu dunglng trc tip t thit b ngi dng ti node B. Cng c mt giao thc mi cho RNC dochuyn giao mm HSUPA v vic truyn li lp vt l c nh hng n vic lm cc gisai th t. Khi d liu nhn c t mt vi v tr BTS, c mt kh nng l thit b hot

ng trong khu vc chuyn giao mm nn cc gi n t nhng BTS khc nhau v c tht khng chnh xc. sp xp li th chc nng sp xp li cn c kt hp vi phntp macro trong MAC-es. V th, chc nng mi l hng i truyn i MAC-es c chcnng chnh l m bo cho cc lp trn gi tin c phn phi ng th t truyn t ucui. Chc nng sp xp c x l trong BTS nn s c tr v BTS phi ch nhng gi bthiu cho ti khi chng c xc nh l nhn c t mt BTS khc trong nhm BTSang hot ng. Tng t i vi HSDPA, lp RLC trong HSUPA cng c chc nngtruyn li cc gi nu lp vt l khng th truyn cc gi i sau khi vt qu s lntruyn li ti a hoc trong kt ni c nhng bin c.

Kin trc giao thc ngi dng HSUPA3.Tc ng ca HSDPA v HSUPA n cc giao tip mng truy nhp vtuyn mt t UMTS (UTRAN : UMTS Terrestrial Radio Access Network)Trong khi nhng tc ng ca HSDPA v HSUPA di dng tc d liu trong giao tipkhng gian c quan tm v thng l trng tm ca cc bui tho lun th tc ng caHSDPA v HSUPA ln s hot ng ca nhng giao din khc cng cn c ch .Trong phin bn R99, tc d liu u cui trn nhng giao tip khc nhau hu ht l384kbps bao gm c giao tip Iu-ps ti mng li gi node h tr dch v GPRS (SGSN :Serving GPRS Support Node), tc ny bng vi tc s dng trong v tuyn. Tuynhin i vi HSDPA th khc, trong giao tip khng gian tc d liu c th ln ti

14.4Mbps trong khong thi gian truyn (TTI : Transmission Time Interval) ngn (2ms). Tuynhin iu ny khng c ngha l tc ang c s dng trn giao tip Iub v Iu-pscho ngi dng. T gc nhn ca ngi dng, ti nguyn v tuyn l thi gian v m cchia s vi nhng ngi dng khc trong mt cell nn tc d liu trung bnh cho mtngi dng trong mt cell r rng l thp hn. Hn na tc nh 10Mbps yu cunhng iu kin sng v tuyn cc k thun li v khng th xy ra trng hp tt cngi dng trong mt cell u c nhu cu s dng tc d liu cao. V th lu lngtrung bnh trn giao tip Iub cng thp hn tc nh cho sng v tuyn.
http://vi.wikipedia.org/wiki/HSDPAhttp://vi.wikipedia.org/wiki/T%E1%BA%ADp_tin:Ki%E1%BA%BFn_tr%C3%BAc_giao_th%E1%BB%A9c_ng%C6%B0%E1%BB%9Di_d%C3%B9ng_HSUPA.jpghttp://vi.wikipedia.org/wiki/T%E1%BA%ADp_tin:Ki%E1%BA%BFn_tr%C3%BAc_giao_th%E1%BB%A9c_ng%C6%B0%E1%BB%9Di_d%C3%B9ng_HSUPA.jpghttp://vi.wikipedia.org/wiki/HSDPA


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B m trong BTS cho php c mt tc nh cho sng v tuyn cao hn trong mt TTInh so vi tc trung bnh trn Iub/Iu-ps. V c b m truyn trong BTS nn iu khinlung cn c tch hp trnh trn b m. Trong phng php ny ngi dng diiu kin sng tt hn c th c tc d liu cao hn so vi ngi dng c iu kinsng v tuyn xu hn. Ngi dng c iu kin sng v tuyn tt hn s c nhiu sphn phi Iub v d liu c truyn nhanh hn nhn di gc sng v tuyn. Mt khc,

khi b m bt u y do iu kin sng v tuyn khng tt (kt qu l tc d liuthp) iu khin lung s lm chm lung d liu li cho ph hp vi nhng ngi dngny.

i vi BTS v u cui, nhn t thay i trong HSDPA c lin quan n s b sung cachc nng lp lch biu v truyn li ti BTS cng nh chc nng kt hp gi cn thit tiu cui. Trong HSUPA, lp lch biu c iu khin bi BTS v c nhng yu cu cholung d liu trong hng ln cng nh nhng knh bo hiu mi cho HSUPA. Hin naychc nng kt hp c t trm gc v chc nng sp xp li c thm vo RNC.

u cui hin nay s c th cho php truyn dn a m nhng cha hon thin trong mitrng thng mi.4.Nhng trng thi giao thc HSDPA v HSUPA

Cc trng thi ca RRC trong HSDPA-HSUPACell_DCH l trng thi c s dng khi bt u truyn d liu t (hoc n) u cui trn

DCH hay HSDPA/HSUPA. T trng thi Cell_DCH u cui s c chuyn qua trng thiCell_FACH hay nhng trng thi cao hn bng hai cch, hoc l chuyn trc tip t trngthi Cell_DCH ln trng thi cao hn, hoc l thng qua Cell_FACH nu khng c d liutrong b m. Cn c mt s ng b gia thi gian p ng ca mng cho vic gi utin c truyn sau mt thi gian ri v b m bt u hot ng. Thi gian chuyn tipgia cc trng thi ph thuc vo yu cu ca vic cu hnh li hay nhng qu trnh cit. Lu gi li ti nguyn HSDPA/HSUPA d tr ca ngi dng khi khng c d liutruyn l khng hiu qu i vi dung lng h thng hay ti nguyn BTS. Tui th pin cathit b u cui cng gim do mt u cui hot ng m khng c d liu truyn qua
http://vi.wikipedia.org/wiki/T%E1%BA%ADp_tin:C%C3%A1c_tr%E1%BA%A1ng_th%C3%A1i_c%E1%BB%A7a_RRC_trong_HSDPA-HSUPA.jpghttp://vi.wikipedia.org/wiki/T%E1%BA%ADp_tin:C%C3%A1c_tr%E1%BA%A1ng_th%C3%A1i_c%E1%BB%A7a_RRC_trong_HSDPA-HSUPA.jpg


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cng s lm pin ht nhanh chng.D liu c th c truyn trong trng thi Cell_FACH nhng ch cho knh truy nhpchuyn tip (FACH) cho ng xung v knh truy nhp ngu nhin (RACH : RandomAccess Channel) cho ng ln. Mt u cui trong trng thi Cell_FACH s gii m knhFACH v bt u p ng d liu hng xung (hoc bt u truyn d liu trong b mhng ln) trn RACH. Ph thuc vo lng d liu u cui c th c chuyn tr li

trng thi Cell_DCH.Nu thi gian ri ko di s tc ng n vic chuyn trng thi u cui sang Cell_PCHhay URA_PCH. Nhng trng thi ny l nhn t tc ng ln nht ti mc tiu th nnglng u cui. Hin nhin, vic s dng chu k nhn gin on (DRX : DiscontinuousReception) vi hot ng nh s s gy tr v ni tip vic truyn d liu th u cuicn c nh s trc. iu ny xy ra trong mt cell (trng thi Cell_PCH) v c trongkhu vc u tin (trng thi URA_PCH). Thu bao di chuyn nhanh trong mt mng dy cs cn nhiu s cp nht cell nn lm tng ti trn RACH.

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Tc d liu ti a hin ti mng WCDMA t c trong iu kin l tng bgii hn mc 2Mbit/s. Nhu cu to ln v d liu tc cao ca ngi s dng thc y tm ra mt con ng mi t c tc vt qua ngng 2 Mbit/s.Cng ngh truy nhp gi ng xung HSDPA (High Speed Downlink PacketAccess) l bc i u tin trong qu trnh pht trin mng WCDMA (UMTS), k tips l nng cao tc d liu trn ng ln (uplink).

Tc d liu ti a hin ti mng WCDMA t c trong iu kin l tng b gii hn mc 2Mbit/s. Nhu cu to ln v d liu tc cao ca ngi s dng thc y tm ramt con ng mi t c tc vt qua ngng 2 Mbit/s. Cng ngh truy nhp ging xung HSDPA (High Speed Downlink Packet Access) l bc i u tin trong qu

trnh pht trin mng WCDMA (UMTS), k tip s l nng cao tc d liu trn ng ln(uplink). Cng ngh HSDPA s c kh nng cung cp tc ln n 10Mbit/s trong khi vntng thch vi cc thit b ngi s dng ang tn ti.. Bi bo ny trnh by mt s khacnh k thut trong HSDPA.GII THIUHSDPA l mt chun cng ngh trong Phin bn 5 ca n cc i tc th h 3 WCDMAbng rng WCDMA 3GP. HSDPA s tng tc d liu truyn ti a v nng cao chtlng dch v QoS, v ni chung l ci tin hiu qu ph tn ng xung khng i xngv p ng nhu cu bng n cc dch v d liu gi. Khi HSDPA c thc hin, n c thcng tn ti trn cng h thng truyn dn nh Phin bn 99 WCDMA hin ti. iu nycho php a HSDPA vo mng WCDMA hin ti mt cch d dng v hiu qu v chiph. HSDPA c thit k cho nhng ng dng dch v d liu nh: dch v c bn : ti

tp, phn phi email; dch v tng tc : trnh duyt web, truy nhp server, truy tm v phchi c s d liu; dch v Streaming : dch v audio/video


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Hnh 1: Hiu qu ph HSDPA

Hnh 2: tr tn hiu trn ng truyn i vi cc cng ngh khc nhauCc kha cnh k thut nm sau khi nim HSDPA bao gm :- Truyn dn knh chia s- M ho v iu ch thch nghi AMC (Adaptive Modulation and Coding).- Yu cu lp li t ng hn hp nhanh H-ARQ (Fast Hybrid Automatic Repeat Request)

- Trnh t nhanh v hp l ti Node B.- La chn v tr t bo nhanh FCSS (Fast Cell Site Selection).- Khong thi gian truyn dn ngn TTI (Short Transmission Time Interval).CC KHA CNH K THUT HSDPATruyn dn knh chia sTi nguyn chung ca ngi s dng trong t bo bao gm cc b m knh v cng sutpht. Khi nim HSDPA c gii thiu bao gm mt s knh vt l thm vo: Knh vt lchia s ng xung tc cao HS-PDSCH (High Speed Physical Downlink SharedChannel) v Knh iu khin vt l HS-DPCCH (HS-Physical Control Channel).


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HS-PDSCHTrong knh ny thi gian v m ho c chia s gia nhng ngi s dng gn lin viNode-B. y l c cu truyn ti cho cc knh logic c thm vo: Knh chia s ngxung tc cao HS-DSCH (HS-Downlink Shared Channel) v Knh iu khin chia s tc cao HS-SCCH (HS-Shared Control Channel.Nhng ti nguyn m ho HS-DSCH gm c mt hoc nhiu b m nh hng vi h s

phn b c nh SF 16. Phn ln 15 b m ny c th phn b cho nhng yu cu vtruyn dn d liu v iu khin. Cc ti nguyn m ho sn sng c chia s ch yutrong min thi gian nhng n c th chia s ti nguyn m ho bng cch dng m hoa thnh phn. Khi c thi gian v b m c chia s, t hai n bn ngi s dng cth chia s ti nguyn m ho trong cng mt TTI.

Hnh 3: Thi gian v b m c chia s trong HS-DSCHHS-DPCCH:

y l knh ng ln, c s dng mang tn hiu bo nhn (ACK) n Node-B trn mi

khi (block). N cng c dng ch th Cht lng knh CQI (Channel Quality), l yut c s dng trong AMC.


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Hnh 4 : C cu truyn dn HS-DSCHM ho v iu ch thch nghi AMCHin ti vic iu khin cng sut nhanh trong mng WCDMA c s dng thch ngvi cc kt ni v tuyn. iu khin cng sut c thc hin trong mi khe (slot) mngWCDMA. V c bn s thch ng vi kt ni v tuyn c yu cu bi v, trong h thngtruyn thng t bo, t s tn hiu trn tp m SNR ca tn hiu thu ti thit b ngi sdng UE (User Equipment) thay i theo thi gian t 30-40 dB v do v cc vng a l. c th loi b nh hng ca fading v ci thin kh nng h thng v tc d liu ti a,tn hiu truyn dn n UE ring bit c thay i ph hp vi s bin i tn hiu xuynsut qua qu trnh x l, gi l thch ng kt ni.

Trong HSDPA cng sut pht c gi khng i trn TTI v s dng c ch m ho viu ch thch ng AMC nh mt phng php iu khin ci thin hiu qu ph.HSDPA s dng c cu iu ch bc cao nh iu ch bin trc giao 16QAM bn cnhQPSK. S iu ch ny c thch ng theo cc iu kin knh v tuyn. QPSK c th htr 2 bit/symbol trong khi 16QAM c th h tr 4 bit/symbol, do tc ti a s gpi khi so snh vi QPSK, s dng bng thng s hiu qu hn. T l m khc nhau cdng l 1/4,1/2, 5/8, 3/4. Node-B (Trm gc) nhn bo co ch th cht lng CQI (ChannelQuality Indicator ) v kt qu cc php o cng sut trn knh kt hp. Da trn nhngthng tin ny n quyt nh tc truyn d liu s l bao nhiu (Bng 1). Trong HSDPA,nhng ngi s dng gn Node-B thng thng c gn mc iu ch cao hn vi tl m cao hn (nh l 16QAM v t l m #) , v c hai u gim khi khong cch gia UEv Node-B tng ln.

Bng 1 Thng lng ng vi cc phng thc iu ch khc nhau

iu ch T l m Thng lng vi 5 m Thng lng vi 10 m Thng lng vi 15 m


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QPSK

1/4 600 kbit/s 1,2 Mbit/s 1,8 Mbit/s

2/4 1,2 Mbit/s 2,4 Mbit/s 3,6 Mbit/s

3/4 1,8 Mbit/s 3,6 Mbit/s 5,4 Mbit/s

16 QAM

2/4 2,4 Mbit/s 4.8 Mbit/s 7,2 Mbit/s

3/4 3,6 Mbit/s 7,2 Mbit/s 10,7 Mbit/sYu cu lp li t ng hn hp nhanh H-ARQGiao thc H-ARQ dng cho HSDPA l dng v ch SAW (Stop And Wait). Trong SAW bnpht gi i mt khi TTI (3 slot) v i cho n khi UE nhn c xc nhn ACK hockhng nhn c N-ACK. c th tn dng thi gian khi phi ch thng bo xc nhnACK, qu trnh x l song song N SAW-ARQ c th c thit lp cho UE, nh th ccqu trnh khc nhau pht i trong cc TTI c lp. Gi tr N c bo hiu r rng dng 3bit, v th ti a N l 8.UE yu cu bn pht pht li d liu nhn c b li sm nht. Khi UE nhn c d liuln th hai, n kt hp vi thng tin pht i u tin vi thng tin pht ln th hai trc khic gng gii m cc thng bo.

Trnh t nhanh v hp l ti Node BTrong mng WCDMA tiu chun trnh t cc gi c thc hin ti Kt ni mng vo tuynRNC (Radio Network Connection), nhng trong HSDPA trnh t gi (medium access layer-hs) c di chuyn n Node-B. iu lm cho cc quyt nh v trnh t gi hu nhxy ra ngay lp tc. V di TTI ngn hn 2 ms, do trnh t ny c thc hin rtnhanh vi mi TTI.

c mt trnh t hp l c th s dng phng php lc quay vng (Round-Robin),ni mi ngi s dng c phc v theo kiu lin tc, tt c ngi s dng nhnc thi gian s dng nh nhau. Tuy nhin, vi yu cu tc sp xp trnh t gi cngvi kh nng ca AMC, ni knh truyn dn c b tr theo cc iu kin knh ngay lptc, mt trnh t gi ph bin khc l trnh t gi hp l cn i. y, th t ca dch vc xc nh bi mc p ng ngay lp tc cao nht cht lng knh lin quan. T

s la chn c da trn cc iu kin lin quan, mi ngi s dng nhn c xpx s lng thi gian phn phi ging nhau ph thuc vo iu kin knh truyn dn.


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Hnh 5: Trnh t nhanh v hp lLa chn v tr t bo nhanh FCSSTrung bnh 20-30% ca trm di ng MS thc hin chuyn giao mm hoc kh mm.Chuyn giao mm l chuyn giao gia hai Node-B, chuyn giao mm do hn l gia ccsector ca Node-B. FCSS cho php mt UE chn Node-B vi c tnh truyn dn hin titt nht. Li th ca h thng ny l tc d liu cao hn c th t c trong phn lnthi gian.

Khong thi gian truyn dn ngn TTITrong HSDPA, HS-DSCH c thm vo s dng TTI t hn 2ms so vi TTI knh truyndn Phin bn 99. Do lm gim thi gian i vng, tng tc x l v kh nng hiuchnh bm theo thi gian tt hn vi nhng knh v tuyn thay i. Trn thc t di cakhung thay i v c chn da trn lu lng c h tr v s ngi s dng ch tr. Gi tr tiu biu l 2 ms.

Yu cu lp li t ng hn hp nhanh H-ARQAMC s dng k thut iu ch thch hp v c cu m ho theo cc iu kin ca knhtruyn dn. Thm ch sau AMC, c th bt c cc li trong cc gi thu v trong thc tcc knh c th thay i trong sut qu trnh cc gi di chuyn trong khng gian. T l likhi BLER (Block Error Rate) sau ln truyn dn u tin l 10%-20%. Mt c cu yu culp li t ng c th c s dng khi phc li cc li trong ng truyn thch ng.Khi gi pht i b thu li th bn nhn yu cu bn pht pht li cc gi b li. K thut cbn l s dng tn hiu pht i trc cng vi tn hiu c pht li sau ny gii mcc block. C hai c cu chnh trong H-ARQ, l Kt hp theo ui CC (ChaseCombining) v Gia tng d IR (Incremental Redundancy).- Kt hp theo uiC cu ny bao gm vic pht li cc gi d liu m bn thu nhn c b li. Mt khicc gi pht li nhn c, bn thu kt hp cc gi tr mm ca tn hiu gc v tn hiupht li c SNR u tin gii m gi d liu.


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u im: Vic truyn v truyn li c gii m ring l (t gii m), tng tnh a dng thigian, c th tng tnh a dng ng truyn.Nhc im: Vic pht li ton b cc gi s lng ph v bng thng.- Tng dTng d c s dng nhn c tnh nng ti a trong bng thng sn sng. Lcny block c pht li ch bao gm d liu sa cha ca tn hiu gc c truyn i ch

khng phi thng tin thc s. Lng thng tin d thm vo c gi i ngy cng tng lnkhi qu trnh pht li lp i lp li m bn thu vn nhn b li.

Hnh 6: Qu trnh truyn li block d liu IRu im: Gim bt bng thng/ lu lng hu dng ca mt ngi s dng v dng ncho nhng ngi khc.Nhc im: Cc bit h thng ch c gi i khi truyn ln u v khng th truyn li,iu lm cho qu trnh truyn li khng th t gii m. V th, nu qu trnh truyn lnu b mt th fading rt ln s tc ng v khng c c hi khi phc li d liu trong honcnh ny.- Tng d tng phnTng d tng phn l s kt hp ca CC v IR. S khng thun li ca IR b loi bbng cch thm vo cc bit h thng cng vi cc bit d gia tng trong qu trnh truyn li.

iu lm cho c tn hiu ban u v tn hiu pht li u t gii m c .

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