82760277 Datn Trien Khai Iptv Tren Wimax 2281

7/29/2019 82760277 Datn Trien Khai Iptv Tren Wimax 2281

1/145

Trang 1

N TT NGHIP

TRIN KHAI DCH V

IPTV TRN CNG NGH

WIMAX

TRIN KHAI DCH V IPTV TRN CNG NGH WIMAX


2/145

Trang 2

MC LC

2.4 Chun MPEG-4..............................................................................................................................................................21

1. H tr cht lng dch v (QoS).......................................................................................................................................53

2. Dch v lp lch MAC....................................................................................................................................................... 54

3. Qun l tnh di ng..........................................................................................................................................................56

4. An ninh.............................................................................................................................................................................57

I.Cc nhn t thnh cng chnh khi trin khai IPTV trn WiMAX...............................59

II.Cc dch v IPTV.....................................................................................................62

III.Cu trc h thng trin khai IPTV trn WiMAX.....................................................62

Hnh 3.2: Phn b dch v IPTV trn WiMAX cho ......................................................63

thu bao c nh v di ng.........................................................................................63

Hnh 3.3: M hnh h thng ngh cho cc ng dng IPTV trn WiMAX.................64

Hnh 3.4: Ngn xp truyn dch v IPTV trn WiMAX............................................65

Hnh 3.5: Lp MAC h tr QoS...................................................................................66

Hnh 3.6: Cu trc lp vt l....................................................................................... 67

Hnh 3.7: S thu pht v tuyn................................................................................67

Hnh 3.8: Tn hiu video iu ch 16QAM nhn c mt s knh c trng thi tt(SS1, SS2, SS4, SS7, SS9) v khng thu c cc SS khc (SS3, SS5, SS8, SS10).....70



3/145

Trang 3

Chng 1: GII THIU IPTV

I. Gii thiu v IPTV1. IPTV l g?

IPTV l tn vit tt ca cm t Internet Protocol Television -truyn hnh quagiao thc Internet.

ITPV theo nh ngha chnh thc nh sau: IPTV c nh ngha l cc dch v aphng tin nh truyn hnh nh, ting ni, vn bn, d liu c phn phi qua ccmng da trn IP m c qun l cung cp cc cp cht lng dch v, bo mt,tnh tng tc, tnh tin cy theo yu cu.

Nh vy IPTV ng vai tr phn phi cc d liu, k c hnh nh, m thanh,vn bn qua mng s dng giao thc Internet. iu ny nhn mnh vo vic Internetkhng ng vai tr chnh trong vic truyn ti thng tin truyn hnh hay bt k loi nidung truyn hnh no khc. Thay vo , IPTV s dng IP l c ch phn phi m theo c th s dng Internet, i din cho mng cng cng da trn IP, hay c th sdng mng ring da trn IP.

C th thy, IPTV l mt dch v s m c kh nng cung cp nhng tnh nngvt tri hn kh nng ca bt k c ch phn phi truyn hnh no khc. V d, set top box IPTV c th thng qua phn mm cho php xem ng thi 4 chng trnhtruyn hnh trn mn hin th, hay c th nhn tin nhn sms, e mail

2. Mt s c tnh ca IPTV H tr truyn hnh tng tc

Kh nng hai chiu ca h thng IPTV cho php nh cung cp dch v phnphi ton b cc ng dng TV tng tc. Cc loi hnh dch v c truyn ti thngqua mt dch v IPTV c th bao gm truyn hnh trc tip chun, truyn hnh chtlng HDTV, tr chi tng tc va 2internet tc cao.

S dch thi gianIPTV kt hp vi mt my ghi video k thut s cho php dch thi gian ni

dung chng trnh mt c ch cho vic ghi v lu tr ni dung IPTV xem sau. C nhn ha

Mt th thng IPTV u cui h tr truyn thng tin hai chiu v cho phpngi dng cui c nhn ha nhng thi quen xem TV ca h bng cch cho php hquyt nh nhng g h mun xem v khi no h mun xem

Yu cu bng thng thp



4/145

Trang 4

Thay v phn phi trn mi knh ti mi ngi dng, cng ngh IPTV chophp nh cung cp dch v ch truyn trn mt knh m ngi dng yu cu. c imhp dn ny cho php nh iu hnh mng c th tit kim bng thng ca mng.

C th truy xut qua nhiu thit bVic xem ni dung IPTV by gi khng ch gii hn vic s dng TV. Ngi

dng c th s dng my PC hay thit b di ng truy xut vo cc dch v IPTV.

3. S khc bit gia IPTV v truyn hnh IntrenetDo u c truyn trn mng da trn giao thc IP, ngi ta i lc hay nhm

IPTV l truyn hnh Internet. Tuy nhin, 2 dch v ny c nhiu im khc nhau:Truyn hnh Internet s dng mng Internet cng cng phn pht cc ni

dung video ti ngi s dng cui. IPTV s dng mng ring truyn cc ni dungvideo n khch hng. Cc mng ring ny thng c t chc v vn hnh bi nh

cung cp dch v IPTV. V mt a l

Cc mng do nh cung cp dch v vin thng s hu v iu khin khng chophp ngi s dng Internet truy cp. Cc mng ny ch gii hn trong cc khu vc al c nh.Trong khi mng Internet khng c gii hn v mt a l, ngi dngInternet no cng c th xem truyn hnh Internet bt k u trn th gii.

V quyn s hu h tng mngKhi ni dung video c gi qua mng Internet cng cng, cc gi s dng giao

thc Internet mng ni dung video c th b tr hoc mt khi n di chuyn trong ccmng khc nhau to nn mng Internet cng cng. Do , nh cung cp cc dch v

truyn hnh nh qua mng Internet khng m bo cht lng truyn hnh nh vitruyn hnh mt t, truyn hnh cp hay truyn hnh v tinh. Thc t l cc ni dungvideo truyn qua mng Internet khi hin th trn mn hnh TV c th b git v chtlng hnh nh thp.

Trong khi, IPTV ch c phn phi qua mt h tng mng ca nh cung cpdch v. Do ngi vn hnh mng c th iu chnh cung cp hnh nh vi chtlng cao.

V c ch truy cpMt set-top box s thng c s dng truy cp v gii m ni dung video

c phn pht qua h thng IPTV , trong khi PC thng c s dng truy cp

cc dch v Internet. Cc loi phn mm c s dng trong PC thng ph thuc voloi ni dung truyn hnh Internet. V d nh, download cc chng trnh truynhnh t trn mng Internet, i khi cn phi ci t cc phn mm media cn thit xem c ni dung . Hay h thng qun l bn quyn cng cn h tr c ch truycp.

V gi thnhPhn trm ni dung chng trnh c phn pht qua mng Internet cng cng

t do thay i. iu ny khin cc cng ty truyn thng a ra cc loi dch v datrn mc gi thnh. Gi thnh cc loi dch v IPTV cng gn ging vi mc ph hng



5/145

Trang 5

thng ca truyn hnh truyn thng. Cc nh phn tch mong rng truyn hnh Internetv IPTV c th hp li thnh 1 loi hnh dch v gii tr.

4. C s h tng mng IPTV

Hnh 1.1 m hnh h thng IPTV Trung tm d liu

Cng c bit n nh l u cui - headend. Trung tm d liu IPTV nhnni dung t nhiu ngun khc nhau, bao gm truyn hnh a phng, cc nh tp hp

ni dung, nh sn xut, qua ng cp, trm s mt t hay v tinh. Ngay khi nhnc ni dung, mt s cc thnh phn phn cng khc nhau t thit b m ha v ccmy ch video ti b nh tuyn IP v thit b bo mt ginh ring c s dng chun b ni dung video cho vic phn phi qua mng da trn IP. Thm vo , hthng qun l thu bao c yu cu qun l h s v ph thu bao ca nhngngi s dng. Ch rng, a im thc ca trung tm d liu IPTV c yu cubi h tng c s mng c s dng bi nh cung cp dch v.

Mng truyn dn bng thng rngVic truyn dn dch v IPTV yu cu kt ni im im. Trong trng hp

trin khai IPTV trn din rng, s lng cc kt ni im im tng ng k v yu

cu rng bng thng ca c s h tng kh rng. S tin b trong cng ngh mngtrong nhng nm qua cho php nhng nh cung cp vin thng tha mn mt lngln yu cu rng bng thng mng. H tng truyn hnh cp da trn cp ng trclai cp quang v cc mng vin thng da trn cp quang rt ph hp truyn ti nidung IPTV.

Thit b ngi dng IPTVThit b ngi dng IPTV (IPTVCD) l thnh phn quan trng trong vic cho

php mi ngi c th truy xut vo cc dch v IPTV. Thit b ny kt ni vo mng



6/145

Trang 6

bng rng v c nhim v gii m v x l d liu video da trn IP gi n. Thit bngi dng h tr cng ngh tin tin c th ti thiu ha hay loi b hon ton nhhng ca li, s c mng khi ang x l ni dung IPTV

Mng gia nhMng gia nh kt ni vi mt s thit b k thut s bn trong mt din tch

nh. N ci tin vic truyn thng v cho php chia s ti nguyn (cc thit b) k thuts t tin gia cc thnh vin trong gia nh. Mc ch ca mng gia nh l cungcp vic truy cp thng tin, nh l ting ni, m thanh, d liu, gii tr, gia nhngthit b khc nhau trong nh. Vi mng gia nh, ngi dng c th tit kim tin vthi gian bi v cc thit b ngoi vi nh l my in v my scan, cng nh kt niInternet bng rng, c th c chia s mt cch d dng

II. L thuyt c bn v h thng mng IP1. L thuyt c bn h tr trong mng IPTV

Vic ng gi cc chng trnh video bao gm vic chn v t chc cc d liu

video thnh cc gi ring bit.1.1 Tng quan v m hnh truyn thng IPTV (IPTVCD)M hnh truyn thng trong IPTV c 7 lp (v mt lp ty chn) c xp

chng ln nhau.Cc d liu video pha thit b gi c truyn t lp cao xung lp thp

trong m hnh IPTV, v c truyn i trong mng bng rng bng cc giao thc calp vt l. thit b nhn, d liu nhn c chuyn t lp thp nht n lp trn cngtrong m hnh IPTV.

Hnh 1.2: M hnh truyn thng IPTV



7/145

Trang 7

Do , nu mt b m ha gi chng trnh video n mt thit b IPTV cakhch hng, th phi chuyn qua cc lp trong m hnh IPTV c pha thit b nhn vthit b gi. Mi lp trong m hnh IPTV c lp vi nhau v c chc nng ring. Khichc nng ny c thc hin, d liu video c chuyn n lp tip theo trong mhnh IPTV. Mi lp s thm vo hoc b i phn thng tin iu khin ca cc gi

video trong qu trnh x l. Thng tin iu khin cha cc thng tin gip thit b c ths dng gi d liu ng chc nng ca n, v thng c nh dng nh cc headerhoc trailer. Bn cnh vic truyn thng gia cc lp, cn c cc lin kt o gia cctng cng mc. 7 lp v 1 lp b sung trong m hnh IPTV c th c chia lm 2loi: cc lp cao v lp thp. cc tng cao hn th quan tm nhiu hn ti cc ng dngca IPTV v cc nh dng file, trong khi cc tng thp hn th quan tm ti victruyn ti cc ni dung.

M hnh IPTV v truyn ti cc ni dung MPEG: Lp m ha video

Qu trnh truyn thng bt u lp m ha, cc tn hiu tng t hoc s c

nn. Tn hiu li ra ca b nn l cc dng MPEG c bn. Cc dng MPEG c bnc nh ngha l cc tn hiu s lin tc thi gian thc. C nhiu loi dng c bn.VD, m thanh c m ha s dng MPEG c gi l dng m thanh c bn. Mtdng c bn thc ra ch l tn hiu th ra t b m ha. Cc dng d liu c t chcthnh cc khung ti lp ny. Cc thng tin cha trong mt dng c bn c th baogm:

+Loi khung v tc .+V tr ca nhng block d liu trn mn hnh.+T s cnh.+Cc dng c bn l nn tng to nn cc dng MPEG.

Lp ng gi video truyn cc dng m thanh, d liu v hnh nh c bn qua mng s, midng c bn ny phi c chuyn i sang mt dng c chn ca gi PES cnh du thi gian (PES- parketized Element Stream ). Mt dng PES ch bao gmmt loi d liu t mt ngun. Mt gi PES c th c kch thc khi c nh hocthay i, c th ln ti 65536 byte/gi. Bao gm 6 byte header, v s byte cn li chani dung chng trnh.

Do bn cht ca mng, th t hay chui cc khung video t li ra ca trung tmd liu IPTV c th khc th t cc khung do cc thit b ca ngi dng nhn c.Do , gip qu trnh ng b, cc h thng da trn MPEG thng dn nhncc gi PES khc nhau trong chui video.

C 2 loi nhn thi gian c s dng i vi mi gi PES: nhn thi gian trnhdin (PTS), v nhn thi gian gii m (DTS):

+ PTS--- nhn thi gian trnh din c gi tr thi gian 33 bit, c t trongtrng PES header. Mc ch ca vic s dng PTS cho mi gi l xc nh xemkhi no v theo trt t no th gi c xem (bi ngi xem).

+DTS--- nhn gii m s dng gip b gii m thit b ca ngi s dngbit khi no x l gi .



8/145

Trang 8

Nh ch ra trn, th t cc gi c truyn i qua mng khc vi th tcc gi nhn c thit b ca ngi s dng. Thit b ngi s dng IPTV s dngcc nhn PTS v DTS ti to li ni dung video gc. Bn cnh vic gi i cc nidung nn MPEG-2, PES cn c kh nng truyn ti cc khi H.264/AVC qua mngIPTV.

Hnh 1.3: ng dng nhn thi gian vi cc gi MPEG PES

Lp cu trc dng truyn tiLp ty chn ny c s dng rng ri trong nhiu ng dng khc nhau. Lp

ny hot ng nh mt lp trung gian gia cc ni dung c nn MPEG-2,H.264/AVC lp cao hn v cc lp thp hn trong m hnh IPTV. Giao thc RTPchnh l li ca lp ny v thng l block c s h tr truyn dng ni dung theo thigian thc qua mng IP.

Ch rng, k thut RTP thng c trin khai trong cc mng khng mbo cht lng dch v QoS truyn cc dch v IPTV. Mc d RTP gip lm tngkh nng cc dng ti ch trong trt t ng, nhng khng c thit k m bocc mc cht lng dch v. Do , trch nhim ca nh cung cp dch v l m bovideo lun c u tin khi chng c truyn i trong h tng mng.

Lp giao thc truyn ti thi gian thcLp ty chn ny c s dng rng ri trong nhiu ng dng khc nhau. Lp

ny hot ng nh mt lp trung gian gia cc ni dung c nn MPEG-2,H.264/AVC lp cao hn v cc lp thp hn trong m hnh IPTV. Giao thc RTPchnh l li ca lp ny v thng l block c s h tr truyn dng ni dung theo thi

gian thc qua mng IP.Ch rng, k thut RTP thng c trin khai trong cc mng khng mbo cht lng dch v QoS truyn cc dch v IPTV. Mc d RTP gip lm tngkh nng cc dng ti ch trong trt t ng, nhng khng c thit k m bocc mc cht lng dch v. Do , trch nhim ca nh cung cp dch v l m bovideo lun c u tin khi chng c truyn i trong h tng mng.

Lp truyn tiThng thng cc gi RTP l dng u vo ca lp truyn ti. iu ng ch

l c th nh x trc tip cc gi MPEG-TS sang payload giao thc ca lp truyn ti.



9/145

Trang 9

Lp truyn ti IPTV c thit k m bo cc kt ni u cui l tin cy.Nu d liu ti thit b ngi nhn khng ng. Lp truyn ti s truyn li. Lptruyn ti thng bo vi lp trn c cc thng tin chnh xc hn.

TCP v UDP l 2 giao thc quan trng nht c s dng lp ny.a) S dng TCP nh tuyn cc gi IPTV TCP l giao thc ct li ca b giao thc internet v c xp vo loi nhhng kt ni. iu ny c bn c ngha l kt ni c thit lp gia u cui nhcung cp v thit b IPTV ca ngi s dng truyn cc chng trnh qua mng.

TCP c kh nng iu khin li xy ra trong qu trnh truyn cc chng trnhqua mng. Cc li nh mt gi, mt trt t gi,hoc lp gi thng gp trong mitrng truyn IPTV. x l cc tnh hung ny, TCP s dng h thng cc s lintc cho php thit b gi c th gi li cc d liu hnh nh b mt hoc hng. Hthng s lin tc ny l trng c di 32 bit trong cu trc gi. Trng u tin

cha chui s bt u ca d liu trong gi v trng th hai cha gi tr ca chuis tip theo m video server ang i (mong) nhn tr li t IPTVCD.

Hnh 1.4: C ch iu khin lung ca TCP

Bn cnh vic sa cc li c th xy ra trong qu trnh truyn ni dung videoqua mng IP bng rng, TCP cn c iu khin lung d liu. iu ny c th tc bng cch s dng trng kch thc ca s, vi thut ton c gi l ca strt. Gi tr trong trng ny xc nh s cc byte c th truyn i qua mng trc khinhn c xc nhn t pha thit b nhn.



10/145

Trang 10

Trong mi trng IPTV, gi tr trng kch thc ca s chnh l kch thcvng m trong IPTVCD tr i lng ni dung c trong vng m ti mt thiim. D liu ny s c gi cho ti khi bn tin thng bo nhn c gi v tIPTVCD.

Khi gi tr ca trng ny bng 0, IPTVCD pha u thu s khng kh

nng x l cc d liu IPTV tc ln. Khi , TCP s ch th cho video serverdng hoc lm chm li tc gi cc gi d liu ti IPTVCD. iu ny s m borng IPTVCD s khng b trn cc gi d liu ti. Khi IPTVCD x l xong cc ccgi d liu trong vng m v video server bit c iu th gi tr ti vngm s tng ln, v video server s bt u truyn tip cc ni dung. Trong mi trngIPTV l tng, s ca ca s c bo v t IPTVCD s bo cho server bit khnggian vng m cn trng chnh l tc m ti cc ni dung video c gi i tvideo server.

Cc cng TCP v Socket: Mi im cui ca mt lin kt IPTV th c mt ach IP v mt gi tr cng lin quan. V th mi lin kt c 4 thnh phn khc nhau:

+ a ch IP ca video server.+ S ca cng ca video server.+ a ch IP ca IPTVCD.+ S ca cng ca IPTVCD.Vic kt hp a ch IP v s ca cng cho php mt tin trnh trn IPTVCD c

th lin lc trc tip vi tin trnh ang chy trn mt trong cc my server c t trung tm d liu IPTV.

Socket cng l mt thnh phn quan trng khc trong m hnh truyn thng IP.Mt socket v c bn l mt giao din ng dng chng trnh (API), c s dng lm vic lin lc gia cc tin trnh ang chy trn mt thit b IP. Mt socket c

thit lp bng cch kt hp a ch IP vi s ca cng.

Hnh 1.5: Qu trnh truyn thng trong mng IPTV

hiu hn v mi lin h gia a ch IP v socket xt cc bc thit lpmt knh truyn thng gia mt tin trnh chy trn IPTVCD v mt tin trnh chytrn trung tm cung cp d liu IPTV. Bc c m t nh sau:

(1) Chun b d liu: Tin trnh gi chy trn h thng server dng IPTV chunb ni dung v gi module truyn thng TCP/IP truyn cc d liu ti mt tin trnh



11/145

Trang 11

ang chy trn mt IPTVCD. Cc tin trnh truyn thng bt u v thng tin headerc thm vo ni dung khi truyn qua cc lp trong IPTVCD.

(2) Thit lp kt ni logic TCP: C 2 u kt ni u c nh ngha bi mta ch IP v mt s cng, kt hp gia a ch IP v s cng gi l socket. H thnga ch i vi lin kt truyn thng bao gm cc thnh phn sau:

+ Giao thc.+ a ch IP ca my ch IPTV.+ ID ca tin trnh chy trn my ch IPTV .+a ch IP ca IPTVCD.+ ID ca tin trnh chy trn IPTVCD.(3) Truyn d liu: Truyn thng bt u thng qua socket gia 2 tin trnh t

pha IPTV server n IPTVCD.(4) Qun l cc dng ni dung IPTV:Giao thc TCP qun l cc dng IPTV

trong khi kt ni c thit lp.(5) Hy b kt ni: Khi hon thnh vic truyn cc ni dung IPTV, IPTVCD

hoc trung tm d liu s hy b socket v kt ni mng.

b) S dng UDP nh hng cc gi IPTV:UDP l giao thc thuc v b giao thc Internet. UDP cho php my ch kt

ni vi mng bng rng gi ti cc IPTVCD dch v truyn hnh qung b c chtlng hi lng ngi dng. UDP ging vi TCP nhng l phin bn s lc hn, ara cho s lng ti thiu cc dch v truyn ti. UDP l giao thc khng lin kt, iu c ngha l kt ni gia video server v IPTVCD khng cn phi thit lp trc khid liu c truyn i. Video server n gin ch thm vo a ch IP ch v s cngvo datagram v gi ti c s mng phn pht ti a ch IP ch. Khi trn mng,UDP s dng cch tt nht c gng thu c d liu v im ch ca n. Ch rng UDP s dng cc khi d liu c gi l cc datagram truyn ni dung quamng.

u im v nhc im ca UDP:+ u im ca UDP:Khng c ngt trong qu trnh truyn ni dung video: khng c tr trong qu

trnh phn phi ngay c khi trong mng c cc gi b tr hoc b hng. Ngc li, khis dng TCP, c th xy ra s ngt qung khi phi ch cc gi b tr v cc khung hnhti hoc phi ch cc gi b hng c thay th.

Dung lng thp: Kch thc header ca UDP ch bao gm c 8 byte trong khiTCP header chim ti 20 byte.

Tc thit lp kt ni: thi gian thit lp v hy b kt ni gia IPTVCD vcc thit b trung tm d liu IPTV ngn. Do , vic phn phi cc gi s dng giaothc UDP thng nhanh hn so vi s dng giao thc TCP.

H tr truyn mt chiu: UDP khng yu cu ng v, do cho php cccng ty s dng v tinh c th truyn ni dung IPTV truyn a im ti khch hngca mnh.

+Nhc im ca UDP:



12/145

Trang 12

Mc d UDP l nhanh chng v hiu qu i vi cc ng dng cn thi gian,v s l khng hiu qu trong trng hp:

Tnh ton vn ca d liu: Tnh ton vn ca d liu khi s dng UDP l khngc bo m khi UDP ch cung cp mt dch v duy nht l kim tra tng vmultiplexing thng qua s cng. Bt k vn no cng c th xy ra trong qu trnh

truyn thng ti u cui no cn c iu khin c lp vi cc ng dng. Ccvn thng gp nh l pht li, ng gi v lp rp li, truyn li cc gi b mt,s tc nghn, v iu khin lung nm ngoi kh nng sa li ca UDP.Kh khn trong vic vt qua cc tng la: Nhiu loi tng la trn mng chn ccthng tin UDP gy ra cc li trong qu trnh truyn thng. y khng phi l vn ln i vi cc nh cung cp dch v IPTV, tuy nhin n cng nh hng ti cc cngty cung cp dch v Internet TV.

i vi IPTV, UDP t ra hu ch khi trung tm d liu cn gi cc ni dungvideo IP ti nhiu IPTVCD v l giao thc mc truyn ti ph bin nht m cc nhcung cp dch v IPTV.

c) S khc bit gia TCP v UDPKhi cc nh cung cp dch v pht cc ni dung IPTV ti cc thu bao, iuquan trng l cc ni dung ny phi n thit b ca ngi dng ng lc v trong dngng. Ni cch khc, cc gi video phi khng b ngt qung. Do , cc nh cung cpdch v cn chc chn s dng giao thc h tr kh nng phn phi qua h tng mng.

Mc d TCP cung cp cc ng dng vi nhiu c trng v mng so vi UDP,nhng cc nh cung cp dch v IPTV khng thng chn TCP l giao thc truyn ti.iu ny ch ra mt thc t rng IPTV l ng dng thi gian thc v khng c tr. TCPc th a ngm vo s phn phi ni dung video IP do thc t rng giao thc s dngc ch iu khin dng.

c im v hn ch cu TCP i vi phn phi chng trnh thi gian thc:o Cn bng gia nhy v tr---- IPTV t nhy vi mt hoc ngt gi hn lvi tr. Vic truyn li cc gi nng cao tin cy ca kt ni gia my chv thit b truy cp IPTV. Tuy nhin, khi vic truyn li din ra nhiu th s lm tr tng ln.

o TCP l giao thc kt ni lin kt---- Nh trnh by trn TCP yu cu thitlp kt ni logic gia my ch v IPTVCD trc khi truyn cc ni dung IPTV.Khi ngi xem chuyn t knh ny sang knh khc cng s gy ra tr i vimi trng truyn hnh trc tip ca IPTV.

o H tr sa li---- TCP cung cp nhiu tnh nng, ng ch l kh nng sa li

v iu khin lung. Tuy nhin, vic sa li trong mng IP video c th lmgim cht lng dch v ti khch hng.o c im ca truyn video: video bao gm mt chui cc nh lin tip, bt c

khi no xy ra ngt vi tc m ti cc hnh nh ny c x l v hin thtrn IPTVCD cng lm gim cht lng hnh nh hin th v nh hng tingi s dng. Thi gian x l mi nh ring bit ch mt khong mt phn cagiy.

o Nu s dng TCP sa li do ngt, c ch sa li nh sau: IPTVCD s bo gi d liu b li bng vic t c.



13/145

Trang 13

Mt bn tin s c gi ti my ch IPTV thng bo cho ng dngbit mt trong cc gi nhn c b ngt.

Di s qun l ca TCP, my ch cn phi tm ra v gi li gi b ngt. IPTVCD nhn c gi mi trong vng m v hin th ni dung video

trong gi . Trong khi TCP thc hin cc bc trn, IPTVCD phi ch gi b li

c truyn li v phi trng lung video hoc b qua gi truyn likhi nhn c, Do k thut sa li ca TCP l khng cn thit.

o Mt gi IP----- qu trnh x l mt cc gi IPTV nhiu hay t cng ging nhqu trnh sa ngt gi IPTV. Cc gi b mt cng cn c truyn li, gy ranh hng bt li ti dch v phn phi IPTV.

o H tr iu khin lung---- Bn cnh vn sa li v thit lp kt ni logic,giao thc TCP cn h tr iu khin tc bit lung d liu gi i, c th gyra nhiu tr ngi trong vic truyn v nhn ni dung IPTV. Tr ngi ny xy ra

khi vng m IPTV bt u trn cc gi IPTV hoc mng b nghn. Khi xy ratrng hp ny, my ch nhn c yu cu gim tc gi cc gi tin lnmng. Nu my ch thc hin yu cu gim tc , c mt kh nng l: khitc gim xung hnh nh s khng th hin th c. Nu bn tin dng cthc hin, dch v IPTV s b tt hon ton.

o Khng h tr a truyn thng---- TCP khng hot ng hiu qu trong mitrng a truyn thng, Do , UDP l la chn tt hn TCP i vi cc dchv truyn thng nh cc ng dng a truyn thng IPTV v truyn qung b.

y l nhng nguyn nhn chnh TCP t c s dng trong IPTV trc tip.

TCP c dng trong cc ng dng khc nh e-mail, download cc chng trnhInternet TV.Mc d, tin cy v kh nng sa li ca UDP khng bng TCP nhngUDP l giao thc c la chn phn pht cc dch v IPTV.

UDP c cc nhc im sau: khng c kh nng tm v sa li. Vn nyc khc phc bng cch gn cc hm sa li vo cc ng dng IPTV chy trn ccmng hoc trong chnh cc dng video.

Lp IPSau lp truyn ti l lp IP (cn c gi l lp lin mng ). Nhim v chnh

ca lp ny l a cc d liu ti cc v tr mng ring bit thng qua nhiu mng clp c lin kt vi nhau c gi l lin mng. Lp ny c s dng gi cc dliu thng qua cc ng khc nhau ti ch. IP l giao thc tt nht c s dngtrong lp lin mng, giao thc ny cung cp dch v phn pht gi c bn cho tt ccc dch v IPTV. Cc loi dch v ny vi h thng truyn n im, ni cc gic truyn t ngun ti mt IPTVCD ch, khc vi h thng truyn a im ni mcc gi c truyn t my ch ti nhiu IPTVCD.

IPv4 l giao thc ph bin nht c s dng trong mng IPTV ngy nay.Nhim v chnh ca IP l phn pht cc bit d liu trong cc gi t ngun ti ch. IPs dng k thut c hiu qu cao nht phn pht d liu. Ni cch khc khng c



14/145

Trang 14

tin trnh no m bo qu trnh phn pht chnh xc thng tin qua mng. Cc khi cs ca giao thc IP l cc on bit d liu c t trong cc gi v c nh a ch.

Gi IP l n v d liu bao gm d liu video thc v cc thng tin ca vicnhn video t trung tm cung cp d liu IPTV ti ch IPTVCD.

Cch nh a ch IP: trong mi trng IPTV, a ch IPv4 thng c dng

nh ngha IPTVCD v trung tm cung cp d liu. a ch IPv4 l chui 4 s cngn cch vi nhau bng cc du chm nh ngha mt cch chnh xc v tr vt lca mt thit b, v d nh set-top box, trong mng. a ch IPv4 gm 32 bit trong hnh phn. Cc s nh phn ny c chia thnh 4 octet, mi octet 8 bit, mi octet ci din bi 1 s h thp phn nm trong khong t 0 n 255. Mi octet c ngncch bi 1 du chm trong h thp phn. a ch IP c t chc thnh 2 phn:

(1)a ch mng dng nh ngha mng bng rng m IPTVCD kt ni ti.(2)a ch host dng nh ngha cc thit b IPTV.Mt im ng ch l mt vi bit u tin ca a ch s nh ngha cc bit

cn li ca trng a ch s c phn chia th no cho host v mng. thun li

cho vic s dng v qun l, a ch IP c chia thnh cc lp khc nhau.Bn cnh vic chia thnh cc lp, mt s a ch IP c dnh ring cho ccmng t nhn. Cc a ch ny nm trong di:

10.0.0.0 to 10.255.255.255172.16.0.0 to 172.31.255.255

192.168.0.0 to 192.168.255.255

Hnh 1.6: Cc lp a ch IP



15/145

Trang 15

a) Mng con IPTVTrong cc mng ln IPTV vi hng ngn IPTVCD tri rng trn mt khu vc

a l rng, mng da trn IP ny cn c chia thnh cc mng nh hn gi l mngcon. Mng con ca mng IPTV cho php nh cung cp dch v nh ngha v gim stcc phn ring bit trong mng m khng cn a ch IPv4 mi. Ngi iu hnh mng

cng s dng a ch mng con giu i cu trc mng ni b trnh b tn cng tmng Internet cng cng. Ngi qun tr mng IPTV s dng cc s ring bit cgi l a ch subnet mask to cc mng con trong mi trng IPTV. Subnet maskl a ch IP 32 bit. Gi tr mc nh ca subnet mask ca lp A, B, C l:

Class A----- 255.0.0.0Class B----- 255.255.0.0Class C-----255.255.255.0

Cc tin trnh chy trn mng con thng c qun l bi thit b phn cnggi l router. Mt router c th ni vi nhiu mng v quyt nh thng tin s c gin u trong mng.

b) Tng lai ca a ch IPKhi cu trc a ch IP ca mng Internet mi c pht trin trong nhng nm

u ca thp k 80, ngi ta cho rng n p ng c nhu cu ca ngi dng hinti v trong tng lai. a ch IP 32 bit trong vesion IPv4 c th nh a ch cho hn 4t my trm trong khong 16,7 triu mng khc nhau.a ch IPv4 khng p ng cnhu cu tc pht trin ca mng Internet nh hin nay.Tc pht trin ca mngInternet nm ngoi d on ca nhng ngi pht trin giao thc IP v s lngmng kt ni vi mng Internet tng ln tng thng.

tm gii php cho hn ch ca a ch IPv4, Nhm K S mng Internet a ra version mi IPv6 vi 128 bit a ch. . IPv6 c th cung cp lng a ch gphng t ln s a ch IPv4. IPv6 c c cc kh nng cung cp h tr vic xc thc, tnhton vn QoS, m ha v b mt. Vic s dng IPv6 trn mng IPTV l thch hp biv c ch QoS bn trong n v c kh nng h tr s lng khng gii hn ccIPTVCD.T 5 ti 10 nm ti, IPv6 s dn thay th IPv4.

Ti sao li s dng IPv6 khi trin khai IPTV ? IPv6 c tnh nng vt trihn so vi IPv4. Cc nguyn nhn chnh khin cc nh cung cp dch v xem xt vics dng IPv6:

Quy m c tng ln: IPv4 dng a ch 32 bit trong khi IPv6 dng a ch 128bit, ln hn gp 4 ln. iu ny cho php nh cung cp dch v IPTV m rng slng thit b c th qun l .

Cu trc header n gin: IPv6 gim kch thc header xung cn 40 byte cnh v n gin cu trc ca trng header.

Tng mc bo v: IPv6 c 2 c im gip tng mc bo v:(1)Bao gm header xc thc----- bao gm cc bn tin xc nhn v kim trangi gi gi.



16/145

Trang 16

(2)Payload bo mt c ng gi----- c im ny m bo tnh ton vnca d liu IPTV v bo mt gia cc my ch trung tm d liu IPTV vcc IPTVCD khc.

Lu lng thi gian thc tt hn: kh nng dn nhn lung ca IPv6 cho phpnh cung cp dch v nh du cc gi ring, ph thuc vo tng loi dch v. Trong

mi trng triple-play, cc router c th coi cc gi IP c dn nhn vi mt nhndng video l cc gi IP c dn nhn khi mang ni dung web.

T ng cu hnh: Kh nng plug and play ca IPv6 gip gim bt phc tpkhi ci t dch v IPTV ti nh ca khch hng.

V nhng u im k trn IPv6 c xem nh gii php lu di h tr trinkhai cc thit b s quy m ln, c th s dng nhiu loi ng dng da trn IP.

Nhc im chnh khi s dng giao thc IP l khng c g m bo rng khino cc gi ti ng ch hay gi c n ng lc khng, ngay c th t cc gi cchuyn n cng khng c xc nh. Do , lp IP lm vic cng vi giao thc lptruyn ti m bo rng cc gi n IPTVCD ng lc v theo trt t ng. IP

cng lm cho qu trnh phn pht ni dung video b tr.

Lp lin kt d liuLp lin kt d liu ly cc d liu th t lp IP v nh dng chng thnh cc

gi ph hp truyn qua mng vt l. Ch , lp lin kt d liu khc vi cc giaothc mng. K thut Ethetnet l mt trong nhng k thut ph bin hn c s dngtrong h thng IPTV. Lp lin kt d liu bao gm cc chc nng dnh cho cc mngda trn Ethernet:

Encapsulation---- Lp ny thm vo cc gi IPTV mt header. Ethernet headerl loi Encapsulation ph bin nht dng trong lp lin kt d liu ca IPTVCD.

nh a ch---- Lp lin kt d liu x l cc a ch vt l ca mng ngi sdng v cc thit b ch. H thng a ch khc nhau vi cc topo mng. V d, a chMAC c s dng trong mng Ethernet. Mi thit b kt ni vi mng IPTV th c 1a ch MAC. di ca a ch MAC l 48 bit v thng c biu din bng 12 strong h 16. Trong 12 s h 16 ny, 6 s u tin dnh cho nh sn xut thit bIPTV v cc s cn li c dng nh ngha giao din mng o.

Kim tra li----- chc nng kim tra li c dng trong vi lp ca m hnhIPTV, bao gm c lp lin kt d liu. Cc gi b ngt l li thng gp trong qutrnh truyn cc ni dung video qua mng da trn IP. Phng php sa li thngdng l kim tra d tha vng (CRC) trong IPTV tm v loi b cc gi b ngt. Sdng k thut CRC thit b gi IPTV thc hin vic tnh ton trn cc gi v lu tr ktqu trong gi. Cc php tnh ton tng t cng c thc hin trn thit b nhn khinhn c cc gi. Nu kt qu tnh ton l nh nhau, th cc gi c x l bnhthng. Tuy nhin, nu kt qu ny l khc nhau, th gi b li s b loi b.Thit b gis to mt gi mi v gi li n. Thng bo vi lp trn trong m hnh IPTV khi cli xy ra l nhim v chnh ca lp lin kt d liu trong k thut kim tra li m cch thng IPTV end to end.

iu khin lung---- iu khin lung l mt trong chc nng ca lp truynti. Trong mng IPTV, iu khin lung cho thit b IPTV ca ngi s dng khng b



17/145

Trang 17

trn bi cc ni dung. Lp lin kt d liu cng vi lp truyn ti thc hin bt k yucu iu khin lung no.

Lp vt lLp vt l quy nh lut l truyn cc bit s qua mng. N cp n vic a

cc d liu qua cc mng vt l ring bit nh xDSL, v khng dy. Lp ny nh

ngha cu hnh mng vt l, thng s k thut, in trong mi trng truyn.Khi dng bit c truyn qua mng, cc gi c chuyn t lp thp n lp

cao trong m hnh truyn thng IPTV. V d lp lin kt d liu s kim tra cc gi vloi b i phn header Ethernet v trng sa li CRC. Tip s kim tra trng kium ca Ethernet header v xc nh gi cn c x l bi giao thc IP. Do gi dliu c chuyn ln lp mang. Lp mng kim tra v loi b i phn IP header vchuyn gi ln lp truyn ti. Phng php b i phn header khi qua cc lp khcnhau gi l bc gi. Qu trnh ny tip tc c thc hin cho ti khi gi d liu lnn tng trn cng trong m hnh. Hnh nh gc c th hin trn mn hnh TV cangi xem.

2. Cc chun nn thi gian thcNn cho php cc nh cung cp dch v truyn cc knh hnh v ting vi cht

lng cao qua mng IP bng rng. Do mt ngi ko th phn bit c ton b ccphn ca hnh nh. Do vic nn s lm gim ln ca tn hiu ban u bng cchb bt cc phn khng nh hng nhiu n cht lngca hnh nh.

Mt h thng nn video tiu biu (hay b m ho ngun) bao gm: b chuyni, b lng t ho, b m ho.

Hnh 1.7: S khi h thng nn nh tiu biu.

+ B chuyn i: thng dng php bin i Cosin ri rc tp trung nnglng tn hiu vo mt s lng nh cc h s khai trin thc hin php nn hiuqu hn l dng tn hiu nguyn thy.

+ B lng t ho: to ra mt lng k hiu gii hn cho nh nn vi hai kthut: lng t v hng (thc hin lng t ho cho tng phn d liu) v lng tvect (thc hin lng t ho mt ln mt khi d liu). Qu trnh ny khng thunnghch.

+ B m ho: gn mt t m, mt dng bit nh phn cho mi k hiu.

II.1Khi qut, cu trc dng bit MPEGCu trc dng MPEG gm 6 lp: lp dy nh (sequence), lp nhm nh (GOP),

lp nh (picture), lp ct lt dng bit (slice), lp macroblock, lp khi (Block).



18/145

Trang 18

a) Khi : Khi 8x8 cc im nh tn hiu chi v tn hiu mu dng chophng php nn DCT.

b) T hp cu trc khi (macroblock): mt cu trc khi l mt nhm cckhi tng ng vi lng thng tin cha ng trong kch thc 16x16 im trn bcnh. Cu trc khi ny cng xc nh lng thng tin cha trong s thay i ty

theo cu trc mu c s dng. Thng tin u tin trong cu trc khi mang dngca n (l cu trc khi Y hay Cr, Cb) v cc vector b chuyn ng tng ng.

c) Mng (Slice): mng bao gm mt vi cu trc khi k nhau. Kch thc lnnht ca mng c th bao gm ton b bc nh v kch thc nh nht ca mng lmt cu trc khi. Thng tin u ca mng cha ng v tr ca mng trong ton bnh, v h s cn bng lng t.

d) nh (Picture): lp nh cho php b gii m xc nh loi ca nh c mha l nh P, I hay nh B. Thng tin u dng ch th t truyn khung b giim c th sp xp cc nh li theo mt th t ng. Trong thng tin u ca nh cncha cc thng tin v ng b, phn gii v phm vi ca vector chuyn ng.

e) Nhm nh (GOP): nhm nh l t hp ca nhiu cc khung I, P v B. Cutrc nhm nh c xc nh bng hai tham s m v n. Mi mt nhm nh bt ubng mt khung I cho php xc nh im bt u tm kim v bin tp. Thng tinu gm 25 bit cha m nh thi v iu khin.

f) on (chng trnh) video: on video bao gm thng tin u, mt s nhmnh v thng tin kt thc on. Thng tin u ca on video cha ng kch thcmi chiu ca nh, kch thc ca im nh, tc bit ca dng video s, tn s nhv b m ti thiu cn c. on video v thng tin u to thnh mt dng bit cm ha gi l dng c bn (Elementary Stream).



19/145

Trang 19

Hnh 1.8: Kin trc dng d liu MPEG2.2 Nguyn l nn MPEGC s ca cng ngh nn video MPEG l s kt hp gia nn trong nh (Intra

-Frame Compression) v cng ngh nn lin nh ( Inter-Frame Compression). Trong:



20/145

Trang 20

Hnh 1.9: Nn MPEGNn trong nh (Intra -Frame Compression): l loi nn nhm gim bt thng tin

d tha trong min khng gian. Nn trong nh s dng c hai qu trnh c tn hao vkhng c tn hao gim bt d liu trong nh. Qu trnh ny khng s dng thng tinca cc nh trc v sau nh ang xt.

Nn lin nh (Intra -Frame Compression): Trong tn hiu video c cha thngtin d tha trong min thi gian. Ngha l vi mt chui lin tc cc nh, lng thng

tin cha ng trong mi nh thay i rt t t nh ny sang nh khc. Tnh ton s dchchuyn v tr ca ni dung nh l mt phn rt quan trng trong k thut nn lin nh.Trong thut nn MPEG, qu trnh xc nh Vector chuyn ng c thc hin bngcch chia hnh nh thnh cc Macro-Block, mi Macro-Block c 16 x 16 phn t nh(tng ng vi 4 Block, mi Block c 8 x 8 phn t nh). xc nh chiu chuynng, ngi ta tm kim v tr ca Macro-Block trong nh tip theo, kt qu ca s tmkim s cho ta Vector chuyn ng ca Macro-Block .

Nguyn l nn MPEG:Dng thc u vo l Rec- 601 4:2:2 hoc 4:2:0. nh hin ti c so snh vi

nh trc to ra nh khc bit. nh ny sau li c nn trong nh qua cc bc :

bin i DCT, lng t ha, m ho. D liu ca nh khc bit v vector chuyn ng(c xc nh nh trn ) mang thng tin v nh sau nn lin nh c a n b m u ra.

Tc bt ca tn hiu video c nn khng c nh, ph thuc vo ni dungnh ang xt (v d mt phn nn t hn hoc nhiu hn), nhng ti u ra b m hodng bt phi c nh xc nh tc cho dung lng knh truyn.

2.3 Nguyn l gii nn MPEG



21/145

Trang 21

Hnh 1.10: Gii nn MPEGNguyn l gii nn MPEG:- u tin l gii m Entropy, sau tch d liu nh (h s bin i DCT) ra

khi cc vector chuyn ng. D liu nh s c gii lng t ho v bin i DCT

ngc.- Nu nh l nh loi I bt u mi nhm nh trong chui, u ra s nhn

c nh hon chnh bng cch trn ( v nh loi I ch l nn trong nh, khng c bchuyn ng, khng dng d liu ca nh khc). N c lu tr trong b nh nh vc v c dng gii m cc nh tip theo.

- Nu nh l nh loi P th cng thc hin gii lng t ha v bin i DCTngc kt hp vi vic s dng vector chuyn ng v lu vo b nh nh sm hn.Trn c s xc nh c d on nh ang xt. Ta nhn c nh ra sau khi cngd on nh (nh d on) v kt qu bin i DCT ngc. nh ny cng c luvo b nh c th s dng nh l chun khi gii m cc nh tip theo.

2.4 Chun MPEG-4

Chun MPEC-4 l mt chun ng d thay i. Vi MPEG-4, cc i tngkhc nhau trong mt khung hnh c th c m t, m ho v truyn i mt cchring bit n b gii m trong cc dng c bn ES (Elementary Stream) khc nhau.Cng nh xc nh, tch v x l ring cc i tng (nh nhc nn, m thanh xa gn, vt, i tng nh video nh con ngi hay ng vt, nn khung hnh ), nh vyngi s dng c th thc hin cc hot ng tng tc ring vi tng i tng (thayi t l, di chuyn, kt ni, loi b, b xung cc i tng ) ngay ti v tr gii mhay m ho. S t hp li thnh khung hnh ch c thc hin sau khi gii m cc i

tng ny.



22/145

Trang 22

Hnh 4.2: Cu trc ca b m ho v gii m video MPEG-4

Hnh 4.3 l mt v d v m ho v tng hp khung hnh video s dng trongMPEG-4. Nhiu i tng, nh ngi, xe t, nh ca, c tch ra khi video uvo. Mi i tng video sau c m ho bi b m ho i tng video VO

(video object) v sau c truyn i trn mng. Ti v tr thu, nhng i tng nyc gii m ring r nh b gii m VO v gi n b t hp compositor. Ngi sdng c th tng tc vi thit b cu trc li khung hnh gc (a), hay x l cci tng to ra mt khung hnh khc (b). Ngoi ra, ngi s dng c th downloadcc i tng khc t cc th vin c s d liu (c sn trn thit b hay t xa thngqua mng LAN, WAN hay Internet) chn thm vo hay thay th cc i tng ctrong khun hnh gc (c).

c th thc hin vic t hp khung hnh, MPEG-4 s dng mt ngn ng m tkhung hnh ring, c gi l nh dng nh phn cho cc khung hnh BiFS (BinaryFormat for Scenes). BiFS khng ch m t u v khi no cc i tng xut hin trong

khung hnh, n cng m t cch thc hot ng ca i tng (lm cho mt i tng xoaytrn hay chng m hai i tng ln nhau) v c iu kin hot ng i tng v to choMPEG-4 c kh nng tng tc. Trong MPEG-4, tt c cc i tng c th c m hovi s m ho ti u ring ca n video c m ho theo kiu video, text c mho theo kiu text, cc ho c m ho theo kiu ho - thay v vic x l tt c ccphn t nh pixels nh l m ho video nh ng. Do cc qu trnh m ho c ti uho cho tng loi d liu thch hp, nn chun MPEG-4 s cho php m ho vi hiu qucao tn hiu nh video, audio v c cc ni dung tng hp nh cc b mt v c th hothnh.



23/145

Trang 23

Hnh 4.3: M ha v tng hp khung hnh trong MPEG-4

2.5 MPEG-4 Part10Vi i tng truyn dn video l mng Internet th ng c vin hng u l

chun nn MPEG-4AVC hay cn gi l H.264/MPEG-4 Part 10. Mc tiu chnh ca chunnn H.264 ang pht trin nhm cung cp Video c cht lng tt hn nhiu so vi nhngchun nn Video trc y. iu ny c th t c nh s k tha cc u im ca cc

chun nn video trc v mt s u im nh sau:- Phn chia mi hnh nh thnh cc Block bao gm nhiu im nh, do vy qutrnh x l tng nh c th c tip cn ti mc Block.

- Khai thc trit s d tha v mt khng tn ti gia cc hnh nh lin tip bimt vi m ca nhng Block gc thng qua d on v khng gian, php bin i, qutrnh lng t v m ho Entropy.

- Khai thc s ph thuc tm thi cc Block ca hnh nh lin tip, do ch cn mho nhng chi tit thay i gia cc nh lin tip. Vic ny c thc hin thng qua don v b chuyn ng. Vi bt k Block no cng c th c thc hin t mt hoc vinh m ho trc hay nh c m ho sau quyt nh Vector chuyn ng, cc

Vector c s dng trong b m ho v gii m d on cc loi Block.- Khai thc tt c s d tha v khng gian cn li trong nh bng vic gii mcc Block d tha. V d nh s khc bit gia cc Block gc v Block d on sc m ho thng qua qu trnh bin i, lng t ho v m ho Entropy.



24/145

Trang 24

u im ca MPEG-4 part 10+ Cht lng hnh nh tt: H.264 l chun nn s dng cng ngh m thanh,

hnh nh mi kh nng nn tt hn so vi cc chun nn trc . Do , chun nncung cp dch v phn pht hnh nh cht lng cao qua mng bng thng gii hn.

+Yu cu bng thng thp: Cht lng hnh nh ca H.264 gn ging vi

MPEG-2 nhng H.264 cn t bng thng truyn ti tn hiu vi cng cht lng.c im ny rt ph hp s dng trong h thng IPTV.

+ C kh nng kt hp vi cc thit b x l video c sn nh MPEG-2 v htng mng da trn IP c sn.

+ H tr truyn hnh phn gii cao: Khi s dng ti u chun nn c th lmtng kh nng truyn d liu ca mng. Do cc nh cung cp dch v truyn thngc th s dng chun nn ny cung cp chng trnh video phn gii cao quamng sn c.

+ H tr nhiu ng dng:Chun nn H.264 c s dng trong nhiu ng dng,vi nn khc nhau th c nhng yu cu ring. V d, ng dng truyn a im trong

IPTV yu cu phi hin th hnh nh dng chun truyn hnh, trong khi, i vi ccng dng gii tr di ng, hnh nh phi hin th c trn cc thit b di ng. phhp vi mi ng dng, chun nn H.264 c rt nhiu profile v level. c im caprofile v level l tc bit v kch thc nh.

+ C th truyn c lp: Chun nn H.264 c th truyn qua nhiu giao thcnh ATM, RTP, UDP, TCP.

+ D dng thch nghi vi cc mng cht lng km nh c ch sa li .

Kt lunMPEG -4 vi nhim v l nhm pht trin cc chun x l, m ho v hin th

nh ng, audio v cc t hp ca chng. MPEG -4 khc so vi MPEG -2 l trong mtkhung hnh th n khng m ho ton b khung hnh m n miu t tng i tngring r v sau mi m ho tng i tng . MPEG -4 chia cc Macro-Blockthnh cc Block nh hn. Trong khi b chuyn ng trong MPEG-2 Part 2 c hnch n ni suy hai chiu pixel th H264/MPEG Part 10 cho php cc Vector chuynng chnh xc n pixel v sau dng ni suy nhiu chiu(Bi-cubic). V cnnhiu im u vit khc na. Do hiu qu nn ca chun nn MPEG -4 tt hn sovi MPEG -2.

Qua qu trnh thc nghim cho rng s tit kim tc bt trung bnh caH264/MPEG Part 10 so vi MPEG-2 l khong 65%. Nh vy hiu qu ca nnH264/MPEG Part 10 tng ln ng k so vi cc chun nn khc. Hiu qu nn tngca H264/MPEG Part 10 to ra cc phm vi ng dng v cc c hi kinh doanh minh: ng dng H264/MPEG Part 10 cho truyn hnh s v di ng hay c th ci tocht lng truyn hnh qua giao thc Internet t c cht lng hnh nh tt nhtruyn hnh s hin nay.

T nhng c im v u im ca MPEG-4 AVC nh du mt bc ngottrong lnh vc nn video, p dng cc k thut tin tin nhm mc ch s dng bngthng hiu qu hn v em li cht lng nh cao hn. Vi cc k thut ny, MPEG-4



25/145

Trang 25

AVC c th gim tc bit xung hn 50% so vi chun MPEG-2. Do , MPEG-4Part 10 c la chn ng dng trong IPTV.

III. Kin trc v chc nng cc thnh phn ca h thng IPTV

Hnh 1.16: Cu trc h thng IPTV

1. Cc thit b tch hp IRDNhng thit b ny c s dng nhn cc ti sn video t mt s mng khc

nhau nh: cc v tinh n cc ng video ring v cc nten viba.

2. Cc b m ha thi gian thcy l mt h thng nn nm ti trung tm d liu IPTV, c dng ti thiuho kh nng lu tr thng tin m vn duy tr cht lng ca cc lung video v audio truyn ti n cc ngi dng, do bng thng mng yu cu truyn cc lungvideo ny c gim bt. H thng nn ny c to ra t mt s b m ho thi gianthc c dng s ho v nn cc knh video, audio v data. Ni dung video shoc tng t cha c nn c a vo thit b m ho nn v sau c nggi vo trong cc gi video c a ra ngoi n cc b nh tuyn IPTV, hu ht ccb m ha hin i u c cng ng ra l cng Ethernet.

3. Cc my ch truyn TV qung bNhng my ch ny c cu hnh vo trong cc cm my ch cho mc ch

lm vic lin tc v chiu trch nhim truyn ni dung IPTV s dng cc giao thc c chn ti cc ngi dng u cui.

4. H thng chuyn m IPTVH thng chuyn m ti trung tm d liu IPTV ph thuc vo hai nhn t sau:(1) nh dng ca ni dung video ngun(2) Chun nn c s dng trin khai trn mng phn phi IP



26/145

Trang 26

H thng chuyn m bao gm cc thit b phn cng c bit c s dng chuyn i lung video MPEG-2, thm ch l nhng nguyn liu tng t thnh nhdng nn khc nh: H.264/AVC hay VC-1.

5. H thng qun l v vn hnh OBSSH thng OBSS cn c bit nh h thng qun l thu bao SMS, c s

dng kt ni vi cc thnh phn trong mng IPTV khc kch hot, thc thi vcung cp cc dch v IPTV trong thi gian thc ph hp vi cc yu cu ca khchhng. Cc thng tin c x l bi OBSS sut qu trnh cung cp mt dch v mi baogm:

+ a ch v tn cc thu bao.+ Chi tit v tnh cc ph.+ Cc chng trnh IPTV multicast c yu cu.+ Cc ti sn VoD-IP c yu cu.

+ Bng thng mng s dng c yu cu cung cp dch v mi.+ Cp a ch IP cho mt dch v mi. kch hot cc dch v mi v h tr qun l vn hnh h thng IPTV, OBSS

c th bao gm mt s hoc l tt c cc chc nng sau:+ Thu thp cc thng tin s dng lin quan n cc loi dch v IPTV.+ Theo di vic yu cu ni dung v cp nht ni dung ph hp.+ Theo di v qun l cc kt ni RG qua mng bng thng rng n cc trung

tm d liu IPTV.+ Qun l v h tr cung cp ni dung.+ Qun l cc ti khon, ho n, thng tin v khch hng.

+ Cung cp mt Web site, cho php cc thu bao yu cu ni dung video.+ Cung cp mt Web portal, cho php cc ngi s dng IPTV truy cp thngtin gip h gii quyt cc li k thut thng thng.OBSS giao tip vi cc hthng con bn ngoi ti trung tm d liu, bao gm h thng qun l quan hkhch hng CRM.

6. H thng qun l quan h khch hng CRM IPTVS dng mt h thng CRM cung cp cho cc nh iu hnh vin thng tnh r

rng trong kinh doanh cc gi dch v c bit. Mt CRM c th bao gm mt s ctrng v c th sp xp thnh 3 module khc nhau:

CRMmodule

M t chc nng

Giao dinvi cc thubao.

Module ny bo m rng cc thng tin chi tit ca chin ti v qu kh u sn sng gip ci thin hiuqu tng tc vi cc thu bao. Qun l lin lc v chmsc khch hng l hai c trng chnh trong module ny.

Tip th ccsn phm IPTVv cc dch v.

Module ny qun l cc chin dch qung co v tipth. Cc chc nng in hnh trong module ny l t chcvic phn phi tip th km theo.



27/145

Trang 27

Bn cc snphm IPTV vcc dch v.

Dng tr gip cc nh cung cp dch v IPTV bnsn phm, kt hp vi module tip th xc nh ccknh bn hng thch hp v theo di kt qu t cc chindch tip th. Phn up-selling cho php cc nh cung cpdch v bn cc dch v IP km theo n cc thu bao.

7. H thng bo mt IPTVu ra t h thng m ho c dn n mt h thng bo mt bo v ni

dung. Mc ch ca h thng bo mt IPTV l gii hn truy cp ca cc thu bao vbo v chng li vic n cp ni dung IPTV. H thng bo mt bao gm hai phn l:CA v DRM.

8. Cc my ch IP-VODCc my ch video lu tr v m cc file video. Cc my ch video thng

thng c kt ni vo mt cm my ch, cung cp cc kt ni d tha trong trnghp mt my ch b li. Cc my ch VoD chy mt phn mm ng dng yu cu

h tr vic qun l d liu VoD v cc loi a phng tin khc9. Cc my ch ng dng v Middleware Headend IPTVMiddleware IPTV c hai loi l: phn mm my ch v my khch. Phn mm

my ch middleware c thc thi trn cc my ch ti trung tm d liu IPTV.Middleware Headend v cc my ch ng dng th hin cc chc nng sau:+ Tng tc vi h thng OBSS v CA+ H tr qun l cung cp thng tin tnh cc, cc thu bao mi v qun ltng quan cc ti sn video.+ T chc cc ng dng phn mm giao tip vi cc middleware my khchc nhng vo trong cc thit b truy cp IP.

+ H tr ngi dng tng tc vi cc dch v VoD v IPTV multicast.Middleaware my khch nm ti IPTVCD v c s dng gi cc chngtrnh ng dng IPTV cch bit khi mng bng thng rng.

10. My ch thi gian mngCc trung tm d liu IPTV thng thng s dng my ch thi gian mng

cho php ng b ho thi gian gia cc thnh phn trong mng. Vic kt ni vi mych ny c d dng thng qua giao thc thi gian mng NTP.

11. H thng chuyn mch IPTVTrung tm d liu IPTV s dng cc thit b chuyn mch bng thng rng

nh tuyn cc tn hiu video gia cc thit b ngun ni dung khc nhau. Cc nh cungcp dch v thng s dng cc thit b mng IP chun nh: cc router, cc switch thc hin vic nh tuyn cc tn hiu. S dng cc thit b mng chun cho php ccnh cung cp dch v IPTV hp nht cc tn hiu data, video, audio trn mt mng.iu ny cho php gim chi ph bo dng, qun l mng n gin v tng tnh linhhot ca h thng chuyn mch.

12. Router phn phiKin trc h thng IPTV cn bao gm b nh tuyn phn phi tc cao, thit

b ny nm ti cc headend ca cc nh cung cp dch v v chiu trch nhim truyn



28/145

Trang 28

ti ni dung IPTV tng tc n mng phn phi. B nh tuyn ny kt ni trc tipti mng trc IPTV.

13. Mng phn phi IP

Mng phn phi IP bao gm hai phn nh: mng trc v mng truy cp(1) Mng trc IP chiu trch nhim cho vic tp hp tt c ni dung video IP thm cc loi lu lng khc trong mt mi trng triple-play.(2) Mng truy cp s dng mt k thut ghp knh nh DSL... truyn ccdch v c yu cu n ngi s dng IPTV.

14. Cc thit b ngi dng IPTVCDIPTVCD l mt thit b phn cng m gii hn mt kt ni IPTV. Trong h

thng IPTV th cc IPTVCD chnh l cc RG v cc IP set-top-box.Trong mt mngIPTV tt c nhng thnh phn ny c kt hp cht ch truyn cc ti sn VoD vmt s lng ln cc knh SD v HD.

IV. C ch phn phi tn hiu IPTVC ba phng php truyn ni dung IPTV l: truyn broadcast, truyn

unicast v truyn multicast1. Broadcast

Truyn broadcast s truyn n tt c cc thit b trong mng k c nhng thitb khng c yu cu, do lm tng kh nng x l ca cc thit b v lng ph bngthng m khng cn thit, ngoi ra phng php ny khng c h tr nh tuyn.

2. Unicasti vi truyn unicast mi thu bao c thit lp mt lung ring ti my ch

video, do nu c nhiu thu bao cng mun xem mt knh truyn hnh th cc ktni unicast c thit lp do lm tn bng thng mng rt nhiu, phng php nych c s dng khi thu bao c nhu cu ring nh trong dch v video theo yu cuVoD.



29/145

Trang 29

Hnh 1.17: Truyn unicast

3. Multicast tit kim bng thng trong qu trnh truyn mt lung video n ng thi

mt nhm cc thu bao, cc nh cung cp dch v s dng phng php truynmulticast.

Hnh 1.18: Truyn multicast

Trong i vi mng bng thng rng ADSL th cc thit b Last mile accessequipment v thit b RG chnh l cc DSLAM v modem ADSL. Cn i vimng truyn hnh cp hai chiu HFC th chnh l h thng CMTS v modem cp.



30/145

Trang 30

Cc nhm v thnh vin hnh thnh hot ng c bn ca k thut multicast, khitrin khai IPTV mi nhm multicast l mt knh TV qung b v cc thnh vin trongmt nhm th c quyn ngang bng nhau khi xem knh . Vi k thut truyn ny thmi knh IPTV ch c truyn n cc IP set-top-box m c yu cu xem knh .iu ny gi cho vic tiu th bng thng tng i thp v gim gnh nng x l trn

cc my ch. Hnh 2.3 miu t tc ng ca vic s dng cng ngh multicast trn vd ca nm thu bao IPTV truy cp ng thi knh 10.

Ch mt bn sao c gi t my ch ni dung n b nh tuyn phn phi.Nhng b nh tuyn ny to ra hai bn sao v gi chng n cc b nh tuyn ti cctng i khu vc qua kt ni IP ring l. Mi b nh tuyn s to thnh cc bn sao truyn ti cho cc ngi nh s c kt ni ti cc cng giao tip ca n m c yu cuxem knh . Do phng php ny s ct gim s lng kt ni IP v cc dngvideo i ngang qua mng v c cc nh cung cp dch v s dng qung bchng trnh IPTV trc tuyn v l mt k thut hiu qu cho vic tn dng ho mth tng IP hin ti. Vic truyn multicast ni dung IPTV th phc tp hn so vi vic

s dng m hnh truyn thng unicast v broadcast.Truyn multicast qua mt mng IPTVTruyn multicast l k thut truyn mt tn hiu video ng thi ti nhiu ngi

s dng, tt c ngi xem u nhn cng mt tn hiu ti cng mt thi im nhngkhng c phn cc lung cho mi ngi nhn. N cung cp mt cch hiu qu htr bng thng cao, mt n nhiu ng dng trn mt mng. IP multicast cn c sdng rng ri trong cc dch v truyn hnh qung b qua mng IP bi v n gim ngk lng bng thng yu cu truyn ni dung IPTV cht lng cao qua mt mng.Multicast khng ch gim bng thng yu cu ca mng m cn gi cho vic x l cacc my ch ni dung mc tng i thp bi v n ch truyn mt bn sao ca mt

lung IPTV ti cng thi im.Tuy nhin truyn multicast c vi bt li sau:+ Cc loi iu khin VCR khng c h tr: multicast khng cho php ccthu bao tua li, dng, tua nhanh ni dung video theo mong mun ca h.

+ Tnh linh hot b gii hn: khi cc thu bao IPTV m cc TV ca h, h chc th xem khi m knh c bit c tip din.

+ Tng yu cc yu cu x l v lm vic ca cc b nh tuyn: chuyn nng cc cng u ra, cc b nh tuyn cn gii quyt thm cc vic nh sao chp cclung video v theo di cc bn sao ca cc gi video do lm tng thm gnh nngng k ln kh nng lm vic ca cc b nh tuyn.

+ H tr t ngun n ch: tt c cc thnh phn gia ngun ni dung IPTV vIPTVCD phi c yu cu h tr cng ngh multicast.

+ Ngn chn lu thng ca IP multicast: cc thit b bo mt nh tng lathng c cu hnh bi cc nh qun tr mng ngn chn cc ng dng IPmulticast. iu ny cn c quan tm khi trin khai cc dch v IPTV qua mngInternet cng cng.

ng dng multicast LoiHi ngh truyn hnh Thi gian thcHc trc tuyn Thi gian thc v khng thi



31/145

Trang 31

gian thcCp nht chng khon Thi gian thcBn tin thi tit trc tuyn Thi gian thcSao chp c s d liu Khng thi gian thcCp nht giao thng Thi gian thc

V. Dch v VOD1. Tng quan VODVoD l k thut m lm thay i cch xem v tng tc ca con ngi vi TV.

VoD cho php ngi dng dut n mt th vin s lu tr cc b phim, cc chngtrnh truyn hnh la chn v xem ngay cc ta . VoD cho php ngi s dngxem TV theo lch trnh ca h hn l ph thuc vo lch trnh ca cc nh cung cpdch v (Xem bt c ci g v bt c khi no h mun). Ngoi ra, VoD cho php ngixem: dng hnh, pht hnh, tua ti, tua lui v xem li ni dung video.

Trong h thng VoD, th vin ni dung video c lu tr trn my ch VoD

v c truy cp t IPTVCD c h tr VoD. Qu trnh yu cu v xem mt ti snVoD c thc hin qua cc bc sau y:

(1) Mt thu bao chn mt ta VoD t ng dng truyn hnh tng tc.(2) IPTVCD nhn lnh ny v gi nhng lnh ny n trung tm d liu.(3) Ti y h thng truy cp c iu kin CA kim tra chng thc thu bao.(4) Khi chng thc hon thnh, mt lung video unicast c chuyn n

tng i khu vc v chuyn tip n IPTVCD c yu cu xem VoD.(5) Sau , lung IP ny c iu khin bi thu bao .Vi cc c im ca VoD th ch c th dng phng php truyn unicast

truyn ni dung VoD n thu bao . Trong truyn n im, mi lung video IPTV

unicast c gi n mt IPTVCD c yu cu, mi IPTVCD s cn mt lung unicastring l, mi lung ny s theo a ch ch qua mng IP n ch.Vic cu hnh kthut ny th kh d thc hin, tuy nhin phng php ny chim lng bng thngmng rt ln.



32/145

Trang 32

2. Kin trc mng VOD

Trong mng bng thng rng hai chiu cng sut cao, vic trin khai dch v IP-VoD cn yu cu mt s khi k thut:

+ Cc my ch IP-VoD+ Cc giao thc truyn ti IP-VoD+ Mt ng dng tng tc IP-VoD client

3. Tnh ton bng thng mngTng s knh IPTV xc nh tng bng thng mng cn cung cp dch v.Thng thng truyn hnh trc tuyn s chim mt lng bng thng c nh trnmng, v tt c cc knh u c cc thu bao s dng. Vi dch v xem phim theoyu cu (VoD), vic truyn ti lung (stream) d liu video n ngi xem dngunicast, mi ngi xem s chim bng thng trn mng tng mt knh IPTV. Do ,dch v VoD s chim ti nguyn mng nhiu hn: Thng thng tnh ton bngthng cho dch v VoD, ngi ta a ra con s d bo s khch hng xem VoD bng10% tng s thu bao IPTV.

Nh vy cng thc tnh bng thng cn cung cp dch v vi cc knh

truyn hnh c m ha H.264 nh sau:BW = {[Tng knh trc tuyn] + [Tng s thu bao] x 10%} x 2MbpsV d: Nu h thng c 100 knh IPTV c m ha bng H.264 (2Mbps/STV)

v c 10.000 thu bao IPTV th bng thng cn cung cp dch v l: (100 + 10.000x 10%) x 2Mbps = 2.2Gbps.

Tm li khi tnh ton bng thng mng trin khai cung cp dch v IPTV vVoD nh cung cp dch v vin thng cn quan tm n cc vn sau:


Hnh 1.30: H thng VOD


33/145

Trang 33

Chn chun m ha:- MPEG-2: 3.5-5Mbps/knh truyn hnh chun (STV)- H.264 (MPEG-4 part 10): 2Mbps/STV8-12Mbps/knh truyn hnh phn gii cao (HDTV)Nh vy, nu dng chun m ha H.264 bng thng mng s c tit kim

hn, nhng gi STP/H.264 li t hn STP/MPEG-2. Li v bng thng cho nh cungcp dch v, nhng chi ph u t ban u ca khch hng cao.

Kt lun:- Dch v IPTV: nh hng n bng thng mng kt tp v mng truy cp v

ph thuc vo s lng knh IPTV pht trn mng.- Dch v VoD: nh hng rt ln n bng thng mng trc v ph thuc vo

s lng thu bao s dng dch v VoD.Bi ton tnh lu lng dch v cho ton mng l mt bi ton phc tp, i khi

cn phi da vo thc t khai tc v thi quen s dng dch v ca tng a bn dn c,tng khu vc c th tnh ton v ty tnh hnh thc t khai thc cn c cc iu

chnh lu lng hp l. ti u bng thng mng p ng bng thng mng cung cp dch vIPTV, thit b mng cn h tr tnh nng Multicast (i vi mng trc) v IGMP (ivi mng kt tp v mng truy cp, trong tng lai s l mng thu bao).

Chng 2: TNG QUAN WIMAX



34/145

Trang 34

I. Gii thiu tng quan v Wimax1. Gii thiuTrong nhng nm gn y, nhu cu truy cp bng thng rng ang pht trin rt

nhanh chng. WiMAX (Worldwide Interoperability for Microwave Access) l mtcng ngh truy cp khng dy bng rng (WBA-Wireless Broadband Access) do Din

n WiMAX xy dng v hng n cung cp cc dch v t c nh n di ng.WiMax c th cung cp tc hng Mbit/s ti ngi s dng (end-user) v trongkhong cch hng km.

Chun IEEE 802.16 nh ngha cc c tnh k thut giao thc vin thng. Dinn Wimax to c hi tim lc cc thit b ang th nghim ca cc nh sn xutkhc nhau tng thch vi nhau, cng nh thit k mt nhm cng ngh chuyn dng khuyn khch pht trin v thng mi ha cng ngh. Chng bao lu na, Wimaxs c chp nhn tr thnh cng ngh truy cp Internet v tuyn mi ni trn thgii.

2. Chun IEEE 802.16 v WIMAXChun IEEE 802.16 c hnh thnh t nm 1998 dnh cho nhng ng dng

ca wireless bng rng. Ban u n tp trung vo pht trin cho vic truyn im aim cho ng truyn theo tm nhn thng LOS (Light Of Sight) ca nhng h thngkhng dy bng rng. n nm 2004, mt phin bn sa i c ra i gi l IEEE802.16-2004 to nn tng c bn cho gii php WiMAX. Nhng gii php WiMAXu tin ny c a ra dnh cho nhng ng dng c nh, c gi l WiMAX cnh. Vo thng 12 nm 2005, nhm IEEE hon thnh v ph chun cho IEEE802.16e-2005, mt s b sung cho chun IEEE 802.16-2004 n c th h tr nhngng dng di ng, thng c gi l WiMAX di ng.

Theo m t ca IEEE 802.16, WiMAX c phm vi ph sng t ti hn 50kmv s hot ng di tn t 2GHz n 11GHz, kt hp c vi nhiu dng Anten nhParabol, Panel, Yagi, Ommi... Vi di tn s hot ng ny, WiMAX cho php kt nim khng cn tho mn iu kin tm nhn thng LOS (Line on Sight), trnh c tcng ca cc vt cn trn ng truyn nh cy ci, nh ca .... y l mt gii phpl tng cho vic truyn d liu, hnh nh, in thoi IP. Thit b WiMAX phi cthit k c th hot ng tt trong cc iu kin nhit , m ca mi trng v scgi... Vi bng tn nh trn, d liu truyn i ca WiMAX c th t ti tc 70Mbps, bo mt cao v n nh tuyt i.

Hai ch song cng c p dng cho WiMax l song cng phn chia theothi gian TDD (Time Division Duplexing) v song cng phn chia theo tn s(Frequency Division Duplexing). FDD cn c 2 knh, mt ng ln, mt ngxung. Vi TDD ch cn 1 knh tn s, lu lng ng ln v ng xung cphn chia theo cc khe thi gian.



35/145

Trang 35

Hnh 2.1: Chun IEEE 802.16

Bng 2.1: M t WiMAX c nh v WiMAX di ng

STT Bng tnBngthng

KchthcFFT

Duplexing Ghi ch

WiMAX c nh1 3.5 GHz 3.5MHz 256 FDD c chng

nhn3.5MHz 256 TDD7MHz 256 FDD



36/145

Trang 36

7MHz 256 TDD2 5.8GHz 10MHz 256 TDD

WiMAX di ng

12.3GHz

2.4GHz

5MHz 512 TDD10MHz 1,024 TDD8.75MHz 1,024 TDD

2.305GHz 3.5MHz 512 TDD

22.320GHz,2.345GHz 5MHz 512 TDD

2.360GHz 10MHz 1,024 TDD

32.496GHz2.69GHz

5MHz 512 TDD

10MHz 1,024 TDD

4 3.3GHz3.4GHz

5MHz 512 TDD7MHz 1,024 TDD10MHz 1,024 TDD

5

3.4GHz3.8GHz,3.4GHz3.6GHz,3.6GHz3.8GHz

5MHz 512 TDD7MHz 1,024 TDD

10MHz 1,024 TDD

3. Nhng c im ni bt ca WiMAX

Lp vt l da trn nn OFDM: chnh v l do ny m WiMAX c th khcphc tt nhiu a ng, v c th hot ng tt trong iu kin khng theo tm nhnthng (NLOS).

Tc d liu ti a rt cao: WiMAX c kh nng h tr truyn d liu tc rt cao. Nu s dng TDM vi t l uplink-to-downlink l 3:1 th tc c th lnn 25Mbps cho downlink v 6.7Mbps cho uplink.

H tr bng thng v tc d liu linh ng: s linh ng trong cu trclp vt l ca WiMAX cho php tc d liu d dng thay i vi bng thng snc. Tnh linh ng ny c h tr trong ch OFDMA ni b bin i FFT c th

thay i theo mun ty theo rng bng thng.AMC (Adaptive Modulation and Coding): WiMAX c th s dng nhiu loi

m ha v iu ch khc nhau, cho php thay i theo tng user hoc tng frame, datrn iu kin ca knh truyn.

Truyn li lp lin kt: vi nhng kt ni i hi tng cng tin cy,WiMAX s h tr ARQ (Automatic retransmition requsets) lp lin kt. Nhng kt



37/145

Trang 37

ni cho php ARQ s mi gi c pht i phi c xc nhn bi pha thu khi nhnc, gi no khng c xc nhn th coi nh l b mt, v pha pht s truyn li.

Cp pht ti nguyn ng v tnh cho user: vic cp pht ti nguyn chohng ln v hng xung u c iu khin bi mt b iu khin trm gc. Tinguyn c th c cp pht trong min khng gian cng nh bng vic s dng hthng AAS (advanced antena system).

H tr Quality-of-service: lp MAC ca WiMAX c mt kin trc kt ninh hng c thit k h tr nhiu loi ng dng bao gm thoi v cc dch v aphng tin. H thng c th h tr dng lu lng c tc bit c nh, tc bitthay i, theo thi gian thc v khng theo thi gian thc. WiMAX MAC c thitk nhm h tr mt s lng ln user, vi a kt ni v QoS cho mi u cui.

Robust security: WiMAX h tr m ha rt mnh, dng AES (AdvancedEncryption Standard), c mt robust ring v c giao thc qun l kha. H thng cngh tr nhn thc rt linh ng da trn giao thc EAP (Extensible Authentication

Protocol).Kin trc nn IP: WiMAX Forum nh ngha mt cu trc mng tham chiuda trn nn tng ca IP. Tt c cc dch v end-to-end u c phn phi a trngiao thc IP vi Qos, qun l session, an ninh v tnh di ng.

II. K thut OFDMK 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 vngtn s s dng, trong cc sng mang con (hay sng mang ph, sub-carrier) trc giaovi 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 tnhiu ny lm cho h thng OFDM c hiu sut s dng ph ln hn nhiu so vi cc kthut iu ch thng thng.

Hnh 2.2: So snh gia FDMA v OFDM



38/145

Trang 38

S lng cc sng mang con ph thuc vo nhiu yu t nh rng knh vmc nhiu. Con s ny tng ng vi kch thc FFT. Chun giao tip v tuyn802.16d (2004) xc nh 256 sng mang con tng ng FFT 256 im, hnh thnhchun Fixed WiMAX, vi rng knh c nh.Chun giao tip 802.16e (2005) chophp kch c FFT t 512 n 2048 ph hp vi rng knh 5MHz n 20MHz, hnh

thnh chun Mobile WiMAX (Scalable OFDMA ), duy tr tng i khong thigian khng i ca cc k hiu v khong dn cch gia cc sng mang vi rngknh.

a) Tn hiu OFDM



39/145

Trang 39

b) Ph OFDM

Hnh 2.3: Tn hiu v ph OFDM

Ngoi u im tit kim bng thng knh truyn, OFDM cn c mt s u imsau y :

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

OFDM ph hp cho vic thit k h thng truyn dn bng rng. Cu trc my thu n gin.

Tuy nhin, bn cnh , OFDM cng c mt s nhc im sau : Vic s dng chui bo v gip gim hin tng ISI do phn tp a ng

nhng chui bo v khng mang thng tin c ch, chim mt phn bng thngca ng truyn lm gim hiu sut ng truyn.

Do yu cu v tnh trc giao gia cc sng mang ph nn h thng OFDM khnhy cm vi hiu ng Dopler, dch tn (frequency offset) v dch thi( time offset) do sai s ng b.

ng bao bin ca tn hiu pha pht khng bng phng, gy ra mo phituyn cc b khuch i cng sut u pht v u thu.

1. Nguyn l iu ch OFDM

1.1 S trc giao ca hai tn hiuNu k hiu cc sng mang con c dng trong h thng OFDM l si(t) v

sj(t). m bo tnh trc giao cho OFDM, cc hm sin ca sng mang con phi thamn iu kin sau :

Trong :

f=T

1l khong cch tn s gia hai sng mang con, T l thi gian k hiu, N l

s cc sng mang con, N.fl bng thng truyn dn v ts ldch thi gian.


( ) ( )+

=Tt

t

ji

s

s

dttstsT

*1 k, i=j

0, ij

(2.1)

(2.2)

sk(t) = 0 , k khc

e(j2kft) , k=1,2,.,N


40/145

Trang 40

Du * trong cng thc (2.1) ch s lin hp phc.

1.2 S iu ch

Hnh 2.4 B iu ch OFDM

Gi s bng thng h thng l B chia thnh Nc knh con, vi ch s knh con ln, n { }LLLL ,1,...,1,0,1,...,1, + , nn NFFT=2L+1. Dng d liu u vo { }la chia

thnh NFFT dng song song vi tc d liu gim i NFFT ln thng qua b chia nitip/song song. Dng bit trn mi lung song song { }la li c iu ch thnh mu

ca tn hiu phc a mc nkd , , n l ch s song mang ph, i l ch s khe thi giantng ng vi Nc bit song song sau khi qua b S/P, k l ch s khe thi gian ng viNc mu tn hiu phc.Cc mu tn hiu pht nkd , c nhn vi xung c s gii hnph ca mi sng mang, sau c dch tn ln n knh con tng ng bng vic

nhn vi hm phc ejL s t , lm cc tn hiu trn cc sng mang trc giao nhau. Tn hiusau khi nhn vi xung c s v dch tn cng li qua b tng v cui cng c biudin nh sau

mk(t)= +

=

L

Lm

tj

nksekTtSd

)(', (2.3)

Tn hiu ny c gi l mu tn hiu OFDM th k, biu din tng qut tn hiuOFDM s l


Xung cs

Xung cs

Xung cs

X

X

X

ejL s t

ejn s t

e- jL s t

{ }la

Lia +,

nia ,

Lia ,

Lkd +,

nkd ,

Lkd ,

m,(t) m(t)


41/145

Trang 41

m(t)= )(' tmk

k

=

=

=k+

=

L

Lm

tj

nksekTtSd

)(', (2.4)

Trc khi pht i th tn hiu OFDM c chn thm chui bo v chng nhiuxuyn k hiu ISI.

Php iu ch OFDM c th thc hin c thng qua php bin i IDFT vphp gii iu ch OFDM c th thc hin c bng php bin i DFT. Thay v sdng IDFT ngi ta c th s dng php bin i nhanh IFFT cho b iu ch OFDM,s dng FFT cho b gii iu ch OFDM. iu ch OFDM bng phng php bin ingc Fourrier nhanh cho php mt s lng ln cc sng mang con vi phc tpthp.

1.3 Thc hin b iu ch bng thut ton IFFT

Tn hiu sau b gii iu ch OFDM khi chuyn i tng t thnh s, lung tnhiu trn c ly mu vi tn s ly mu

ta=B

1=

FFTN

1=

FFT

S

N

T(2.5)

ti thi im ly mu t=kT+lta,, S(t-kT) =S0, do vy (2.3) vit li :

mk(kTs+lta) = S0+

=

+L

Ln

ltkTjn

nkaSsed

)(,

= S0+

=

L

Ln

ltjnkTjn

nkaSSs eed

..,(2.6)

Do SkTS = 2 k

fkf

S

S 21

=

, kt qu1=SSkTjne

Tng t nh vy, viFFTFFTS

SaS N

nlj

Nffjn

ltjn

eee

21

2

==

, (2.6) c vit

li:

mk(kTs+lta)=S0+

=

L

Ln

N

nlj

nkFFTed

2

,

(2.7)

Php biu din (2.7) trng vi php bin i IDFT. Do vy b iu ch OFDM cth thc hin mt cch d dng bng php bin i IDFT.



42/145

Trang 42

1.4 Chui bo v trong h thng OFDM

u im ca phng php iu ch OFDM khng ch th hin hiu qu sdng bng thng m cn c kh nng lm gim hay loi tr nhiu xuyn k hiu ISI(Inter Symbol Interference) nh s dng chui bo v (Guard Interval- GI ). Mt mu

tn hiu c di l TS, chui bo v tng ng l mt chui tn hiu c di T G pha sau c sao chp ln phn pha trc ca mu tn hiu nh hnh v sau:

Hnh 2.5: Chui bo v GI

Do , GI cn c gi l Cyclic Prefix (CP). S sao chp ny c tc dngchng 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 cchiu di l Ts, sau khi chn thm chui bo v c chiu di T G th tn hiu ny cchiu di l T = TS+TG. Do hiu ng a ng multipath, tn hiu ny s ti my thutheo nhiu ng khc nhau. Trong hnh v m t trang bn,hnh a,tn hiu theo ngth nht khng c tr, cc ng th hai v th ba u b tr mt khong thi gian sovi 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 hintng ISI.Do trong OFDM c s dng chui bo v c di T G s d dng loi b

hin tng ny. Trong trng hp TG MAX nh hnh v m t th phn b chng lnISI nm trong khong ca chui bo v, cn thnh phn tn hiu c ch vn an ton. pha my thu s gt b chui bo v trc khi gi tn hiu n b gii iu chOFDM.Do , iu kin cn thit cho h thng OFDM khng b nh hng bi ISIl:

TG MAX (2.8)

vi MAX l tr truyn dn ti a ca knh.


Phn tn hiu c chPhn tn hiu c chGI


43/145

Trang 43

a ) Khng c GI

b) C GI

Hnh 2.6 Tc dng ca chui bo vVic s dng chui bo v m bo tnh trc giao ca cc sng mang con, do

vy n gin ho cu trc b nh gi knh truyn, b cn bng tn hiu my thu.Tuy nhin, do chui bo v khng mang thng tin c ch nn tng ph ca tc truyn nn ph tn hiu s tng, tiu tn bng thng, lm gim hiu sut s dng bngthng mt lng l:

GS

S

TT

T

+= (2.9)

1.5 Php nhn vi xung c bn

Trong a s cc h thng v tuyn, tn hiu trc khi truyn i u c nhnvi xung c bn. Mc ch chnh l gii hn ph tn hiu pht sao cho ph hp vi rng knh truyn.Trong trng hp rng ph tn hiu ln hn rng knhtruyn th s gy nhiu xuyn knh cho h thng khc. Trong OFDM, tn hiu trckhi pht i c nhn vi xung c bn c b rng ng bng b rng ca mt mu tnhiu OFDM, xung c bn thng l xung vung hay xung ch nht. Sau khi chn thm

chui bo v th xung c bn k hiu l S(t) c rng l TS + TG.



44/145

Trang 44

Hnh 2.7 Xung c bn

Trong thc t xung c bn thng c s dng l b lc cos nng (Raise cosine

filter).

2. Nguyn l gii iu ch OFDM2.1 Truyn dn phn tp a ngKnh truyn dn phn tp a ng,v mt ton hc, c biu hin qua p

ng xung h(, t) v hm truyn t H(j , t).i vi p ng xung, bin l tr truyn dnca knh, l khong thi gian tn hiu i t my pht n my thu. Bin i Fourier cap ng xung cho ta hm truyn t ca knh

H(j,t) =

deth j),( (2.10)

Gi s khng c AWGN, mi lin h gia tn hiu thu u(t), tn hiu pht m(t) vp ng xung:

Hnh 2.8 M hnh knh truyn

Trong min thi gian l tch chp ca tn hiu pht v p ng xung ca knh:

u(t) = m(t) * h( t, )


S(t)

TS

-TG

T

0

h(,t)

H(j,t)

m(t) u(t)


45/145

Trang 45

=

dtmthmaz

0

)(),( (2.11)

2.2 Nguyn tc gii iu chS

Hnh 2.9 B thu tn hiu OFDM

Cc bc thc hin y u ngc li so vi pha my pht. Tn hiu thu sc tch chui bo v, gii iu ch khi phc bng tn gc, gii iu ch ccsng mang con, chuyn i mu tn hiu phc thnh dng bt (tn hiu s) v chuyni song song sang ni tip

Hnh 2.10 Tch chui bo v


t(k-1)T

(k-1)TS

kT

kTS

Giiiu ch

Giiiu ch

Giiiu ch

X

X

X

e- jL s t

ejn s t

ejL s t

Lkd ,^

nkd ,^

Lkd ,^

Lia ,^

nia ,^

Lia ,^

u(t)

la^


46/145

Trang 46

Sau khi tch chui bo v khi lung tn hiu u(t), lung tn hiu nhn c l:u(kTS+t)=u(kT+t) (2.12)

Thc hin gii iu ch bng thut ton FFT

Gi thit mt mu tin OFDM Ts c chia thnh NFFT mu tn hiu, tn hiuc ly mu vi chu k ly mu l ta.

Khi rng mt mu l :

ta =FFT

s

N

T(2.13)

Sau khi ly mu, tn hiu nhn c s tr thnh lung tn hiu s:

u

(t) => uk

(kTs + nta) , n=0,1,2,....,NFFT 1 (2.14)

Mu tn hiu sau khi gii iu chlkd ,

^c biu din di dng s:

lkd ,

^=

)(1

0

'

S

)( aSSFFT

ntkTjlN

n

aSka entkTu

T

t +

=

+

(2.15)

Tch s biu din thnh phn m thnh tch hai thnh phn (2.15) c vit lidi dng:

lkd ,

^= aSSS

FFT

ntjlkTjlN

n

aSk

a eentkTuT

t

=

+1

0

'

S

)( (2.16)

ViT

12S = , th 12 == jlkkTjl ee SS

Mt khc,FFT

a

S

aSN

tT

t

21

2 == nn (2.16) vit li:

lkd ,

^= FFT

FFTNnj

N

n

aSk entkTuN

/21

0

'

FFT

)(1

=

+ (2.17)

Biu thc trn chnh l php biu din DFT vi chiu di NFFT.

3. Nguyn l a truy cp OFDMA



47/145

Trang 47

OFDMA (Orthogonal Frequency Division Multiple Access - a truy nhp phntn trc giao ) l mt cng ngh a sng mang pht trin da trn nn k thut OFDM.Trong OFDMA, mt s cc sng mang con, khng nht thit phi nm k nhau, cgp li thnh mt knh con (sub-channel) v cc user khi truy cp vo ti nguyn sc cp cho mt hay nhiu knh con truyn nhn ty theo nhu cu lu lung c

th.3.1 c im

OFDMA c mt s u im nh l tng kh nng linh hot, thng lng v tnhn nh c ci thin.Vic n nh cc knh con cho cc thu bao c th, vic truynnhn t mt s thu bao c th xy ra ng thi m khng cn s can thip no, do s gim thiu nhng tc ng nh nhiu a truy xut (Multi access Interfearence-MAI)

Hnh 3.1 ODFM v OFDMA



48/145

Trang 48

Hnh 3.2 m t mt v d v bng tn s thi gian ca OFDMA, trong c 7ngi dng t a n g v mi ngi s dng mt phn xc nh ca cc sng mangph c sn,khc vi nhng ngi cn li.

F A d A D a D

A d A D a D

A c e A c E a c E

A c e A c E a c E

B e g B E g b E g

B e g B E g b E g

B F g B F g b F g

B F g B F g b F g

t

Hnh 3.2 V d ca biu tn s, thi gian vi OFDMA.

Th d c th ny thc t l s hn hp ca OFDMA v TDMA bi v mingi s dng ch pht mt trong 4 khe thi gian, cha 1 hoc vi symbol OFDM. 7ngi s dng t a n g u c t c nh (fix set) cho cc sng mang theo bnkhe thi gian.

3.2 OFDMA nhy tnTrong v d trc ca OFDMA, mi ngi s dng u c mt s sp t c

nh (fix set) cho sng mang. C th d dng cho php nhy cc sng mang ph theokhe thi gian nh c m t trong hnh.

Vic cho php nhy vi cc mu nhy khc nhau cho mi user lm bin i thcs h thng OFDM trong h thng CDMA nhy tn. iu ny c li l tnh phn tptheo tn s tng ln bi v mi user dng ton b bng thng c sn cng nh l c liv xuyn nhiu trung bnh, iu rt ph bin i vi cc bin th ca CDMA. Bngcch s dng m sa li hng i (Forward Error Correcting - FEC) trn cc bc

nhy, h thng c th sa cho cc sng mang ph khi b fading su hay cc sng mangb xuyn nhiu bi cc user khc. Do c tnh xuyn nhiu v fading thay i vi mibc nhy, h thng ph thuc vo nng lng tn hiu nhn c trung bnh hn lph thuc vo user v nng lng nhiu trong trng hp xu nht.

f A b

c



49/145

Trang 49

c B

A

B c

B a

C

A

t

Hnh 3.3 Biu tn s thi gian vi 3 ngi dng nhy tn a, b, c u c 1 bcnhy vi 4 khe thi gian.

u im c bn ca h thng OFDMA nhy tn hn hn cc h thng DS-CDMA v MC-CDMA l tng i d dng loi b c xuyn nhiu trong mt tbo bng cch s dng cc mu nhy trc giao trong mt t bo.

Mt v d ca vic nhy tn nh vy c m t trong hnh 3.4 cho N sngmang ph,n lun lun c th to ra N mu nhy trc giao.

A F e D c b

B A f E d c

C B a F e d

D C b A f e

E D c B a f

F E d C b a

Hnh 3.4 6 mu nhy tn trc giao vi 6 tn s nhy khc nhau

3.3 H thng OFDMA

Hnh 3.5: Tng quan h thng s dng OFDMA

Ngun tn hiu lm mt bt c iu ch bng tn c s thng qua ccphng php iu ch nh QPSK ,M- QAM Tn hiu dn ng (bn tin dn ng,knh hoa tiu - pilot symbol) c chn vo ngun tn hiu, sau c iu chthnh tn hiu OFDM thng qua bin i IFFT v chn chui bo v GI. Lung tn hius c chuyn thnh tn hiu tng t trc khi truyn trn knh v tuyn qua anten


iuch bng tngc

Chn k t dnng

IFFT Chn GI DAC

DACTch GIIFFT

Tch k t dnng

Cn bngknh

Khi phc knh

truyn

Gii iu ch bngtn gc

Knhtruyn


50/145

Trang 50

pht. Tn hiu ny s b nh hng bi fading v nhiu trng AWGN( Addictive WhiteGaussian Noise ).

Tn hiu dn ng l mu tn hiu c bit trc pha pht v pha thu,c pht km vi tn hiu c ch nhm khi phc knh truyn v ng b h thng.

Hnh 3.6 Mu tn hiu dn ng trong OFDMA

Pha my thu s thc hin ngc li so vi my pht. khi phc tn hiu phtth hm truyn phi c khi phc nh vo mu tin dn ng i km. Tn hiu nhnc sau khi gii iu ch OFDM c chia lm hai lung tn hiu. Lung th nht ltn hiu c ch c a n b cn bng knh. Lung th hai l mu tin dn ngc a vo b khi phc knh truyn, sau li c a n b cn bng knh khi phc li tn hiu ban u.

i vi knh hng xung :

Hnh 3.7 OFDMA downlink



51/145

Trang 51

Hnh 3.8 Cu trc cm trong OFDMA downlink

Cu trc cm bao gm 1 knh con trong min tn s v n k hiu OFDM trongmin thi gian, cha N sng mang. Mi sng mang c th c iu ch khc nhau.

i vi knh hng ln :

Hnh 3.9 OFDMA uplink

Hnh 3.10 Cu trc cm trong OFDMA uplink



52/145

Trang 52

Cu trc cm gm 1 knh con trong min tn s v 3 k hiu OFDM trong minthi gian, mi cm ch 144 sng mang d liu, s dng iu ch thch nghi trn tnguser; mi user c th yu cu t 1 n 32 knh con; 2 knh con c s dng lmranging (php o c li bng cch o thi gian truyn ca tn hiu in t) v yu cubng thng (nu c) ca user .

Khi cp sng mang cho cc user, OFDMA to ra mt dy c bn cc sng mangri thc hin dch vng dy khi cp cho cc user khc nhau.

III. Cu trc lp MAC

Hnh 2.11 minh ha m hnh tham chiu v phm vi ca chun. Trong m hnhtham chiu ny, lp PHY tng ng vi lp 1 (lp vt l) v lp MAC tng ng vilp 2 (lp lin kt d liu) trong m hnh OSI.

Hnh 2.11: M hnh tham chiu

Trn hnh ta c th thy lp MAC bao gm 3 lp con. Lp con hi t chuynbit dch v cung cp bt c bin i hay nh x d liu mng bn ngoi, m nhnc qua im truy nhp dch v CS (CS SAP), vo trong cc MAC SDU c tipnhn bi lp con phn chung MAC (CPS) qua SAP MAC. Tc l phn loi cc n vd liu dch v mng ngoi (cc SDU) v kt hp chng vi nh danh lung dch v(SFID) MAC v nh danh kt ni (CID) ring. N cng c th bao gm cc chc nngnh nn u mc ti (PHS). Nhiu c tnh CS c cung cp cho giao tip vi ccgiao thc khc nhau. nh dng bn trong ca payload CS l duy nht vi CS, v MACCPS khng c i hi phi hiu nh dng hay phn tch bt c thng tin nu tpayload CS. MAC CPS cung cp chc nng MAC ct li truy nhp h thng, nh vdi thng, thit lp kt ni, v qun l kt ni. N nhn d liu t cc CS khc nhau,



53/145

Trang 53

qua MAC SAP, m c phn loi ti cc kt ni MAC ring. MAC cng cha mtlp con bo mt ring cung cp nhn thc, trao i kha bo mt, v mt ha.

Chun 802.16 c trin khai bt u t vic truyn cc dch v bng rng gmthoi, d liu v video. Lp MAC da vo chun DOCSIS v c th h tr lu lng

d liu cm vi yu cu tc nh cao khi m h tr ng thi video lin tc v lulng thoi nhy vi tr trn cng mt knh. Ti nguyn c cp pht cho mt ucui bi b lp lch MAC c th thay i t mt khe thi gian ti ton b khung, do cung cp mt di ng ln thng lng ti ngi s dng u cui c trng ti ccthi im nht nh. Hn na, do thng tin cp pht ti nguyn c truyn trong ccbn tin MAP ti bt u mi khung, nn b lp lch c th thay i hiu qu cp phtti nguyn trn c s tng khung mt ph hp vi bn cht cm ca lu lng.

1. H tr cht lng dch v (QoS)

Vi lin kt khng gian (air) nhanh, cng sut ng xung/ng ln khngi xng, tnh cht ti nguyn nhiu v k thut cp pht ti nguyn linh hot, chun802.16e c th t c cc yu cu QoS cho mi loi dch v d liu v ng dng.

Hnh 3.17 H tr QoS trong 802.16e

Trong lp MAC 802.16e, QoS c cung cp qua cc lung dch v nh m t

trong hnh 3.17. l mt lung cc gi theo mt hng duy nht c cung cp mttp cc thng s QoS ring bit.

Trc y khi cung cp mt loi dch v d liu no , th trc tin trm gcv u cui ngi s dng thit lp mt lin kt logic theo mt hng duy nht giacc MAC ngang cp c gi l kt ni. Sau MAC ngoi cng kt hp cc gi ingang qua giao din MAC thnh mt lung dch v, ri c chuyn qua kt ni. Ccthng s QoS kt hp vi lung dch v nh ngha lp lch v th t truyn trn giao



54/145

Trang 54

din v tuyn. V vy QoS hng kt ni c th cung cp iu khin chnh xc quagiao din v tuyn. V giao din v tuyn thng b nghn c chai, nn QoS hng ktni cho php iu khin hiu qu QoS u cui-u cui.

Loi QoS ng dng c im QoSUGS

Dch v cp pht tnguyn

VoIP Tc duy tr ln nht Dung sai tr ln nht Dung sai trt

rtPS

Dch v theo di thigian thc

Dng Audio hocVideo

Tc dnh ring nh nht Tc duy tr ln nht Dung sai tr ln nht u tin lu lng

ErtPS

Dch v theo di thigian thc m rng

Thoi vi tch sngtch cc (VoIP)

Tc dnh ring nh nht Tc duy tr ln nht Dung sai tr ln nht Dung sai trt u tin lu lng

nrtPS

Dch v theo di phithi thc

Giao thc truynfile (FTP)

Tc dnh ring nh nht Tc duy tr ln nht u tin lu lng

BE

Dch v n lc tt nht

Truyn d liu,trnh duyt Web, ...

Tc duy tr ln nht u tin lu lng

Bng 3.7 Cht lng dch v v ng dng 802.16e

Cc thng s lung dch v c th c qun l t ng qua cc bn tin MAC iu chnh cc yu cu dch v ng. K thut QoS da vo lung dch v p dngcho c DL v UL cung cp QoS c ci thin trong c hai hng. Chun IEEE802.16e h tr mi loi dch v d liu v ng dng c cc yu cu QoS thay i.Tt c c tng kt trong bng 3.7.

2. Dch v lp lch MAC

Dch v lp lch MAC 802.16e c thit k truyn hiu qu cc dch vbng rng bao gm thoi, d liu v video qua knh v tuyn bng rng bin thin theothi gian. Dch v lp lch MAC c cc c im sau y:



55/145

Trang 55

a) B lp lch d liu nhanh:blp lch MAC phi cp pht hiu qu ti nguynkh dng p ng cho lu lng d liu cm v cc iu kin knh bin thin theo thigian. B lp lch c t ti mi trm gc cho php p ng nhanh cc yu cu lulng v cc iu kin knh. Cc gi d liu c kt hp thnh cc lung dch v vi

cc thng s QoS xc nh trc trong lp MAC sao cho b lp lch c th xc nhchnh xc th t truyn dn gi qua giao din v tuyn. Knh CQICH cung cp thngtin hi tip knh nhanh cho php b lp lch la chn iu ch v m ho thch hp chomi cp pht. iu ch/m ho thch ng kt hp vi HARQ cung cp truyn dn tthn qua knh bin thin theo thi gian.

b) Lp lch cho c UL v DL:dch v lp lch c cung cp cho c lu lng ULv DL. B lp lch MAC thc hin cp pht ti nguyn hiu qu v cung cp QoSmong mun trong UL, UL phi hi tip chnh xc v thng tin ng lc nh cc iu

kin lu lng v cc yu cu QoS. Nhiu k thut yu cu bng thng ng ln, nhyu cu bng thng qua knh sp xp, yu cu piggyback v thm d c thit k h tr cc yu cu bng thng UL. Lung dch v UL xc nh k thut hi tip chomi kt ni ng ln m bo d bo hot ng ca b lp lch UL. Hn na, ccknh con UL trc giao, khng c nhiu trong t bo. Lp lch UL c th cp pht tinguyn hiu qu hn v QoS tt hn.

c) Cp pht ti nguyn ng:MAC h tr cp pht ti nguyn thi gian-tn s choc UL v DL trn c s tng khung. Cp pht ti nguyn c truyn trong cc bn tinMAC ti bt u mi khung. V vy, cp pht ti nguyn c th c thay i trn tngkhung p ng vi cc iu kin knh v lu lng. Thm na, lng ti nguyn trongmi cp pht c th tri rng t mt khe n ton b khung. Cp pht ti nguyn tt vnhanh cho php QoS mong c cho lu lng d liu.

d) QoS nh hng:B lp lch MAC iu khin truyn d liu trn c s tng ktni. Mi kt ni c kt hp vi mt dch v d liu c mt tp cc thng s QoS xc nh kha cnh hot ng ca n. Vi kh nng cp pht ng ti nguyn cho cUL v DL, b lp lch c th cung cp QoS mong mun cho c lu lng UL v DL.c bit vi lp lch ng ln Ti nguyn ng ln c cp pht hiu qu hn,

hiu sut d tin on hn v QoS tt hn.

e) Lp lch la chn tn s:B lp lch c th hot ng trn cc loi knh conkhc nhau. Vi cc knh con tn s thay i khc nhau nh hon v PUSC, cc sngmang con trong cc knh con c phn b gi ngu nhin dc theo bng thng, ccknh con c cht lng nh nhau. Lp lch tn s thay i khc nhau c th h tr QoSc tnh cht tt hn v lp lch ti nguyn thi gian-tn s linh hot. Vi hon v lin



56/145

Trang 56

k nh hon v AMC, cc knh con phi chu suy hao khc nhau. Lp lch la chn tns c th cp pht cc ngi s dng di ng cho cc knh con tng ng mnh nht.Lp lch la chn tn s c th lm tng dung lng h thng vi s tng va phitrong tiu CQI UL.

3. Qun l tnh di ng

Tui th ca pin v chuyn giao l hai vn then cht ca cc ng dng ding. 802.16e h tr ch Sleep v ch Idle cho php hot ng MS hiu qu vcng sut. 802.16e cng h tr chuyn giao cho php MS chuyn mch t mt trmgc ti trm khc m khng lm ngt qung kt ni.

a) Qun l cng sut

Chun IEEE 802.16e h tr hai ch vn hnh cng sut hiu qu-ch

Sleep v ch Idle. Ch Sleep l mt trng thi trong MS kim sot cc khongthi gian vng mt giao din v tuyn trm gc phc v c m phn trc.Khong thi gian ny c c trng bi tnh khng khng kh dng ca MS, cquan st t trm gc phc v, ti lu lng DL hoc UL. Ch Sleep nhm ti thiuho s s dng cng sut MS v s dng ti nguyn giao din v tuyn trm gc phcv. Ch Sleep cng cung cp tnh linh hot cho MS qut cc trm gc khc nhmthu thp thng tin cn cho chuyn giao trong sut ch Sleep.

Ch Idle cung cp mt k thut cho MS tr nn c hiu lc mt cch nh

k cho bn tin lu lng qung b DL m khng c s ng k ti mt trm gc cbit khi MS i qua mi trng lin kt v tuyn c nhiu trm gc c tr. Ch Idlegip ch cho MS bng cch chuyn cc yu cu cho chuyn giao, cc hot ng thngthng khc; gip ch cho mng v trm gc bng cch loi tr giao din v tuyn vlu lng chuyn giao t cc MS khng tch cc khi m vn cung cp mt phngphp n gin v hp l (gi) bo cho MS v lu lng DL.

b) Chuyn giao

C ba phng php chuyn giao c h tr trong chun 802.16e- chuyn giao

cng (HHO), chuyn mch trm gc nhanh (FBSS), v chuyn giao phn tp macro(MDHO). Trong , HHO l bt buc cn FBSS v MDHO l hai ch t chn. Dinn WiMAX trin khai mt vi k thut ti u ho chuyn giao cng trongchun 802.16e. S ci thin ny c trin khai vi mc ch gi tr chuyn giao lp 2lun nh hn 50 ms.

Khi FBSS c h tr, MS v BS duy tr mt danh sch cc BS c bao hmtrong FBSS cng vi MS. Tp ny c gi l tp tch cc. Trong FBSS, MS gim st



57/145

Trang 57

lin tc cc trm gc trong tp tch cc. Trong s cc BS tp tch cc, mt BS neoc nh ngha. Khi hot ng trong FBSS, MS ch lin lc vi BS neo bng cc bntin ng xung v ng ln bao gm cc kt ni lu lng v qun l. S chuyntip t mt BS neo ny ti BS khc (tc l chuyn mch BS) c thc hin m khng

cn vin dn cc bn tin bo hiu HO r rng. Th tc cp nht neo c cho php bi di ca tn hiu thng tin ca BS phc v qua knh CQI. Mt chuyn giao FBSS btu vi quyt nh thu hoc pht d liu ca MS t BS neo m c th thay i trongtp tch cc. MS qut cc BS ln cn v la chn ci no c cho l ph hp trongmt phin thit lp tch cc. MS bo co la chn cc BS v th tc cp nht thit lp

tch cc c thc hin bi BS v MS. MS gim st lin tc di tn hiu ca cc BStrong thit lp tch cc v la chn mt BS t thit lp BS neo. MS bo co la chnBS trn CQICH hoc MS khi u bn tin yu cu HO. Mt yu cu quan trng ca

FBSS l d liu c pht cng mt lc ti tt c cc b phn ca mt thit lp tchcc ca cc BS c th phc v MS.

Vi cc MS v BS c h tr MDHO, MS v BS duy tr mt thit lp tch ccca cc BS bao gm trong MDHO vi MS. Gia cc BS trong thit lp tch cc, mtBS neo c nh ngha. Ch chun ca hot ng quy vo mt trng hp ringbit ca MDHO vi thit lp tch cc gm c mt BS n. Khi hot ng trongMDHO, MS lin lc vi tt c cc BS trong thit lp tch cc ca cc bn tin nhng ng xung v ng ln v lu lng. Mt MDHO bt u khi mt MSquyt nh thu hoc pht bn tin n hng v lu lng t nhiu BS trong khongthi gian ging nhau. Vi MDHO ng xung, hai hoc nhiu hn BS cung cptruyn dn ng b ca d liu ng xung MS nh kt hp a dng c thc hinti MS. Vi MDHO ng ln, truyn dn t MS c thu bi nhiu BS trong lachn a dng ca thng tin thu c thc hin.

4. An ninh

Chun IEEE 802.16e h tr cc c im lp an ninh bng cch cc cng nghkh dng tt nht hin nay. H tr nhn thc ngi s dng / thit b tng h, giao

thc qun l kho linh hot, mt ho lu lng, qun l v iu khin bo v bn tin vti u ho giao thc an ninh cho cc chuyn giao nhanh.

Giao thc qun l kho:giao thc qun l kho v mt m ring phin bn 2(PKMv2) l c s ca an ninh c nh ngha trong 802.16e. Giao thc ny qun lan ninh MAC s dng cc bn tin PKM-REQ/RSP. Nhn thc PKM EAP, iu khinmt ho lu lng, trao i kho chuyn giao v tt c cc bn tin an ninh ahng/qung b u da vo giao thc ny.



58/145

Trang 58

Nhn thc ngi s dng/thit b:Chun IEEE 802

Documents

82760277 Datn Trien Khai Iptv Tren Wimax 2281