Tong Hop Mang Thong Tin

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    Phn I: Tng quan v k thut chuyn mch

    M u1.nh ngha: Telecom switching

    CM l thit lp,duy tr, v gii fng lien kt c tnh chn la xung quanh cc g truyn dnvin thng.(hv)Trong h thg CM gm 3 qtrnh: thit lp, duy tr, gii fng.Kt ni ny c tnh chn la:- Ti 1 thi im thu bao A v B c nhu cu lin lc, hthng Cm thit lp 1 lin lc vlgia A v B. Lin kt ny c duy tr trong sut tgian trao i thng tin.- Khi A v B kt thc qtrnh trao i thng tin th lin kt c gii fng.2.Cc hthng CM:Mng vin thng: cung cp dv vin thng(h.nh, ting ni, ch vit)

    Cu trc mng VT: Cc thit b u cui, Cc trung tm CM v tng i(Exchange), Cch thng truyn dn.nh ngha: Cc hthg CM l cc hthng cng ngh c s dng trong mng VT CM cccuc gi t cc u cui ca n.CM c 2 loi: CM ni ht (thu bao) Local; CM chuyn tip (trung k) Trunk.(hv)* Phn bit theo cu trc:- Vi CM ni ht c cc g thu bao v cc g trung k:+g thu bao ni t thu bao n hthg CM.+g trung k ni gia cc hthg CM.- CM chuyn tip: Ch c cc g trung k (nu c thu bao th ch l thu bao nghip v, kfc v khch hang)- i vi CM ni ht th lu lng cuc gi thp, ng ta xem cc CM ni ht nh cc trungtm tp trung v phn b ti.- CM chuyn tip l CM l lng tp trung t cc g trung k.Ch : Cc hthg CM fc v cc thu bao. Thu bao c tnh fn b ton cu. k th c 1 hthgCM fc v cho tt c cc thu bao, gii fp y l fi fn ti s c nhiu cc hthg CMv mi hthg CM th fc v 1 s lng nht nh cc thu bao nm trong vng a l of n.Cc hthg CM c ni vi nhau.S tng qut mng CM:(hv)

    LSS Local Switching System: CM ni ht.TSS Trunk Switching System: CM trung k.RSS Remote Switching System: CM v tinh.STP Signalling Transfer Point: im chuyn tip bo hiu.IN Intelligent Network: Mng thng tin.T s ta thy:- C 4 CM ni ht, mi CM kt ni vi thu bao 2 cch trc tip.

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    - C 4 CM LSS c ni vi nhau qua 1 CM trung gian TSS.- RSS c gi l CM v tinh hay CM thu bao xa.

    Thng tin thit lp hay gii fng cuc gi c truyn qua mng bo hiu, mng qun lvin thng, tng hiu qu v tin cy ca mng. Mng thc hin 5 chc nng chnh:

    - Qun l li Fault Management.- Tnh cc Accouting Management.- An ninh Security Management.- Hot ng Performance Management.- Cu hnh Confirgurator Management.Mi thnh fn of mng c cc CSDL quyt nh hng, cu hnh ca thnh fn .Cnmng qun l VT th qun l s bin thin CSDL of cc i tng.

    Mng v dch v vin thng1.Mng vin thng

    nh ngha: L tp hp cc trang thit b k thut cung cp dch v vin thng chongi s dng. xy dng mng vin thng cn quan tm n:- S i tng l bao nhiu- Mt phn b- Tc pht trin thu bao tng vngHai i lng chnh ny bin thin theo thi gian , thoe tnh cht ca x hi .Ngoif ta sdng d bo khoa hc xc nh 2 i tng ny bng cch xc sut thng k.* Thnh phn ca mng vin thng:a.Thit b u cui (Terminal equipment): pha ngi s dng phi c thit b a thng

    tin ng s dng vo mng v a thng tin t mng v pha ngi s dng .b.Cc trung tm : thu nhp , x l thng tin tha mn yu cu ca ngi s dng .Trung tm thc hin hai chc nng c bn : chuyn mch, x l thng tinTy vo chc nng ca mi trung tm m mt tng hai l chnh hoc l h tr.c.Mng ( h thng) truyn dn:Dng lkt cc thit b u cui vi cc trung tm. ng ni t cc TE n cc trungtm c goi l cc dng dy thu bao . kt ni ny c th n gin c cu trc l mtdy i , hay c cu trc phc tp ( mng truy nhp AN _ Access Network ) cn lien ktgia cc trung tm vi nhau c gi la ng trc ( hay ng trung k)d.Phn mm ca mng:

    Cho bit cc thit b trong mng c ni vi nhau nh th no hay cho bit TOPO mng .Phn mm cng nh ngha giao thc mng ,gip cho cc thit b trong mng c th traoi thng tin vi nhau .T a c phi c phn mm ca mng mi hot dng c , mng h thng mi honchnh .

    2. Dch v vin thng.a.Chun ha cc loi dch v.

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    (hv)UNI - User Network Interface ( giao din gia ngoif s dng v mng)

    NNI - Network Node Interface( giao din gia cc nt mng)*Dch v mng thng tin:-Vn chuyn thng tin cho ngi s dng mng vin thng

    -Cung cp phng tin cho ngi s dng, cho ngi vn chuyn thng tin ca h-c im :- Khng can thip vo thng tin vn chuyn qua mng. Cht lng dich j v ch ch ticht lng truyn t thng tin .- nh ngha c cc knh vn chuyn- Kh nng truy cp vo dch vDch v xa: Tng t nh dch v mng nhng phc v n tn u cui ( phc v chotng loi thng tin ) v du : dch v in thoi , truyn s liu (hv)b.nh gi cht lng phc v(QoS):

    (hv)c.S pht trin ca cc loi dch v vin thng:*c im ca cc loi dch v :- Cc loi dich v u c th hin bng m thanh, hnh nh ch vit (vn bn)- Tt c cc loi dch v thng c gi quyt bng thng tin in.- Mi i tng s dng cn c nhiu loi dch v- Cc loi dch v thng gii quyt c lp vi nhau.- Vi mi loi dch v s c tng phng tin ring

    Vi cch xy dng mng vin thng truyn thng th hiu qu kinh t thp v gp nhiu

    kh khn khi thau i dch v. V vy hng pht trin l xy dng mt mng a dch v cung cp c nhiu loi dch v cho ngi s dng.Mng a dch v khng phi l tp hp ca cc mng khc nhau m l mt mng k thutthng nht c kh nng cung cp nhiu loi dch v , trong mng mi loi dch v cn nmt m ha (pha u dng thng tin- nh ngha thng tin truyn trn mng cung cpcho ngi s dng ). V vy mng c th cung cp nhiu loi dch v cho mt ngi sdng ( bng cch ghp knh thi gian )

    Dch v truynthng

    Phng tin

    in thoi Mng in thoi

    in bo Mng in boTruyn s liu Mng truyn s liu

    a dch v Phng tinNhiu Mt

    Cc dch ting ni , ch vit v hinh nh c nhiu c trng khc nhau:- Thng tin c a ch hay khng c a ch

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    - Thng tin mt chiu hay hai chiu- Thng tin c nhy cm tr hay khngd.S pht trin ca cng ngh vin thng:(hv)Cng ngh truyn dn bao gm: Gia cng tn hiu; Phng tin truyn dn

    *Gia cng tn hiu:Gia cng tn hiu truyn dn hay tng t hay tn hiu truyn dn s c phng phpti u.- Vi tn hiu tng t c bng thng rng v cht lng km nn ch dung trong mt slnh vc nht nh .- Hin nay la chn phng thc truyn dn s v c nhiu u im l kh nng chngnhiu cao , tuy nhin do trong truyn dn s, s mc tin hiu l hu hn , c mt s t hp

    b cm khng c dung vi i vi tn hiu s. nhiu khng b tch ly cui knh thta phi dung cc trm lc lc.

    Ngoi ra trong tin hieu s cn gp mt hin tng thng thy la jitter . l hin tng c

    th lp li mt xung khi pht nhng thi im xut hin xung li khc nhau pha u thu.(s)Phng php ghp knh:(s)Phng php ghp knh theo tn s: cc knh khc nhau, ng ta s dng sng mang khcnhau nn cht lng mi knh l khc nhau vi tng loi thng tin . Ngy nay ngi ta sdng phng php ghp knh theo thi gian l chnh (TDM)

    Nn tin hiu: tit kim knh dn ngi f ta c th dung rt nhiu cc phng php nnkhc nhau cho tng loi s liu.+Vi tn hiu m thanh : Trong qu trnh bin thin th lng khc nhau gia hai mc lin

    lin k ly mu l rt thp. Do ngi ta ch li dng iu ny m ha lng khcnhau ny ri chuyn i.Vi cht luong cng cao , mc lng t ha cng hp , dn n sbit cn m ha cho s bin ng cng ln , song vn nh hn mc m ha bin .+Tn hiu video: Trong cc hnh nh xut hin lien tip th mc thay i im sang lrt nh. Do ngi ta c mt m ring ch ra rng mc thay i sang trc v sau la

    bao nhiu. Ngoi ra vi cc im nh lin k thng c mc sang l ging nhau cao.Vi tn hiu video c tn s 6,5 Mhz: fN= 2.6,5=13 MHzVi tiu chun nn MPEG 2 xung cn 8 Mbps cn truyn tn hiu video

    *Tm kim phng tin truyn dn tc cao:V tuyn; Hu tuyn- Hu tuyn :+ u tin s dng cp ng trn 4 ly c tn s fmax =150KHz . Khng s dng tn scao hn v cp ng trn ging nh dy anten bc x lm suy hao tn hiu v lm nhhng, lm nhiu nhng h thng khc, truyn dn ti a 16 knh thoi.+ S dng cp i xng : xon li thnh tng i mt , tng nhm mi i 4 dy , c tn sti a fmax =200KHz. Khai thc trn mt i dy 60 knh thoi , tuy nhin li c nhcim xuyn nhim tn s cao , gii php cho vn ny l ng i v v phi ring bit.+ S dng cp ng trc : t c n fmax=60MHz, vi mt s loi f c bit

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    c im : Chiu ca in t trng t ngoi vo trong nn tn cao khng gy nhiu choh thng khc , nu ta chon c t l ung knh ngoi v ng knh trong thch hp thc th gim suy hao trn cp ng trc ti mc ti thiu .Trn cp ng trc c th truyn 10800 knh thoi , tuy nhin li c nhc im l suyhao ln , 152km phi khuyech i mt ln th mi m bo chat lng . t tin

    + S dng cp quang : l phng tin truyn dn l tng di tn ln ti Ghz , suy hoanh 70,80 km mi cn lp trm khuch i, khng b can nhiu t ngoi vo hay t trongra, r tin.Tuy nhin c nhc im l : cng lp t tn km do phi xy dng h thng ngm , sc

    bn c hc km.- V tuyn : c th truyn sng di , cc di , ngn v cc ngn .+ Sng di cn nng lng ln mi truyn c i xa, cng sut hang trm kw mi truynvi km+ Sng ngn: cng sut nh, vi w l tuyn c i xa hang chc km. Tuy nhin nhcim Fadinh, nn t s dng trong vin thng .

    + Song cc ngn: di tn rng nhng ch truyn c theo uong thng, gi l thng tintm nhn thng.Nhc im: suy gim ln. 50km li khuyech i mt ln. gi sng ny l v tuynchuyn tip, c th thu phat bng cc v tinh, gi l v tinh a tnh .

    Cng ngh chuyn mch1.Chuyn mch thu thp x l thong tin tho mn yu cu ngi s dnga, Phng thc chuyn mch knh/N: Theo y/c of ng s dng thit lp 1 knh dn cc tg trao i tt vi nhau trn kenh

    dn .Qu trnh :+ Thit lp knh dn+ Duy tr knh dn+ Gphng knh dnc im+Ng s dng lm ch knh dn trg sut qtr trao i tt ca h.+ Knh dn thun tin cho vic trao i tt 2 chiu. Thi gian thc v ko c tr.+ Hiu sut s dng knh l trg khong tgian duy tr knh. V ti 1 thi im knh dn sdng cho lin lc l 1 chiuhiu sut ti a t 50%.

    + CM knh ch f hp vi cc trg hp khi tgian khi fc v thit lp cuc gi l rt nh sovi tgian duy tr cuc gi.Trong thc t we thng trang b s knh trong 1 cm bao gi cng nh hn nhu cu sdng. Vi tnh ton xc sut cc thu bao cng hng ti 1 thi im l thp.+ Tuy nhin cng c th xy ra hin tg k /ng c nhu cu ng dngcuc gi b tchitn tht.

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    + Phi c HT iu khin thit lp cuc gihthg ny c gi l hthg bo hiu. v n l 1c th gn lin vi mng CM knh.b. Chuyn mch tinL phng thc truyn tt n ch theo y/c ng dng.Qu trnh:

    +Nhn tin+Gi tinc im+Ng s dng k lm ch knh dn. gy kh khn cho vic trao i tt theo tgian thc.+C c im xy ra htg tr t/h+Vic nhn v gi tt do tb hon ton m nhn cn 1 hthg giao thc trao i tt vi cctb.+Cn chun ha cho vic gi v nhn tt. Ty theo cc chun ha m ta c cc gi CM tinkhc.

    Nu chun ha tt theo gi, tao c 1 CM tin in hnh l CM gi.

    +Hiu sut s dng knh trong CM tin l cao.+CM tin thch hp vi truyn tt, s liu 1 chiu.(s)c. Chuyn mch giBn tin c chia thnh nhiu gi vi chiu di xc nh, mi gi c fn header mang thongtin ch v th t giMi gi i qua cc node c tin hnh theo phng php store&forward nh CM tinTi u thu tin hnh sp xp cc gi tr liTrong cc gi lun c cc trng ktra bo gi truyn khng b lic dim

    Trao i thong tin theo tg thc nhng nhanh hn CM tini tng khng lm ch knh dnHiu sut caoThc hin truyn s liuKtra li tng chng, dm bo gi truyn khng b li nhng li lm gim vn tc truyn giBng thong thp, tc thpPh hp vi mng truyn dn tc thpd. CM a chc nng*khin trc tip: tt khin trc tip khin s hng ca c cu chp hnh.*khin gin tip: tt khin k trc tip khin c cu chp hnh m n c a n b nh,

    sau mi c a ti c cu chp hnh.*khin theo ctrnh np sn: SPC (stored Program Control) tt khin c a vo 1 b vxl.B vxl s tng tc vi b nh a rat t khin c cu chp hnh. y l nguyn lkhin c s dng n nht hin nay.

    CM theo thi gian1. S ghp knh:

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    Chuyn mch thi gian l loi chuyn mch phc v s trao i ni dung gia hai khe thigian trn cng mt tuyn PCM.(s)CODEC: bin i t analog digitalMUX v DEMUX fi ng b vi nhau.

    - Tn hiu m thanh c m ha qua b CODEC vi ts ly mu 8khz. T/h u ra 8 bit c di 125us tg ng vi tc 64Kbps. t/h sau b ghp knh n s c ghp tun t ti cct/im t1,t2,tn- Chu k chim knh trn lung ra HW gi l 1 khe thgian Ts. Trong trng hp ghp Nknh th di Ts = 125us/N.2.Ngl hng ca CM knh theo tgian T:- Ngl: CM tgian T, n fi trao i v tr tgian ca t/h.. Vic trao i c th/hin = cch sdng cc b nh. V ngl th.hin trao i tgian ny bao gm 2 bc:+nh v tr, tgian ca cc t/h.+i ch v tr tgian.

    - Ngtc trao i khi tgian:+ trao i khe tgian c thc hin = cch lu tm cc t/hiu c truyn trn lung cao vo bnh ca CM v sau th c cc t/h c lu tr ra vi th t khc so vi khi ghi vo.(hv)VD: kt ni a vi b

    b vi ac vi nn vi c(hv)* trong khong tgian TS1(t1): t/h A i n c ghi vo a ch th 1( nh th 1) ca b nh

    ca CM tgian T.Cng trong khong tgian ny t/h B c lu tr nh th 2 s c c ra(t/h B c ghi vo nh th 2 trong khung trc )(hv)* trong khong tgian TS2: t/h B i n.Ghi B vo nh th 2, ng thi c t/h A nhc a ch 1 ra.(hv)* trong khong tgian TS3: t/h C i n, ghi C vo nh c a ch th 3 ng thi c t/h

    N nh c a ch th n ra.(hv)Qu trnh ghi v c tip tc c t.hin an xen nhau cho n khi khe tgian cui cng ca 1

    khung. Qtrnh cng c lp li cho tt c cc khung khc of cuc ni.Ch : m bo hng ca CM T th vic ghi vo v c ra t b nh CM n khng cthc hin 1 cch ng thi. Khong tgian ca 1 khe tgian s c chia ra lm 1 lt, 1 nadnh ghi v 1 na dnh c. N tg ng vi chu k ghi, c tg ng.(hv)3.Mch tng ng ca CM T:Mt CM tgian ghp n knh c m t nh 1 CM k gian vi kch thc n x n v giao imgia mch vo v mch ra s c c tg ng vi cc y/c kt ni.

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    (s)4. khin CM:*khin tun t: l loi khin CM trong cc a ch ca b nh CM c phn nhim 1cch tun t khi ghi vo hoc khi c ra. Trong khin tun t, 1 b m khe tgian s c sdng thu nhn a ch ca nh. B nh ny s tng them 1 v vo gtr sau mi ln

    thay i khe tgian.(hv)*khin ngu nhin: l phng thc khin trong cc a ch ca CM tgian k tg ng vith t ca cc khe tgian t TS1TSn nhng chgn c fn nhim t trc theo y/cu kt ni.Trong khin ngu nhin thi fc 1 b nh khin c sdng nhn a ch cc nh.(hv)*Phng thc khin trong thc t: l kt hp ca khin tun t v khin ngu nhin;-Ghi tun t c ngu nhin (SWRR)-Ghi ngu nhin c tun t(RWSR)5.Tham s ca CM T:

    *Cu to: bao gm 2 b nh-B nh m lu thoi BM: lu tr t/h thoi.- B nh khin: CM(hv)Dung lng b nh:CBM = n.BB: s bit mang bi 1 knh( s bit trong 1 khe tgian). Nu PCM l 8 bitn: s khe tgian hoc s knh u vo.CCM = n.log2(n).

    *Thi gian ghi v c:TWR= TRD = 125/(2n) (us)6.Ghp c bit //:* trong thc t cc lung t/h thp khng c u ni trc tip vi CM tgian m c ghp lithnh cc lung cao vi bc ghp ln hn sau mi a vo CM tgian.*tgian c v ghi:TWR= TRD = 125/(2n) (us)-thc t RAM: t xp x vi chc ns => nmax = 1000~2000ti a = 512 thu bao.*Phng php lm tng hiu qu ca CM T sdng pp ghp bit //.-L sp xp c t/h s ha 8 bit thnh // a vo CM tgian v truyn trn 8 g dy ring

    bit.-Cc t/h ac bin i t ntip sang // qua 1 b bin i SP. KHi cc t/h c sp xp thnh //th 8 bit cho 1 knh c coi nh l 1 khe tgian v 8 g vt l t b bi c coi nh 1 lungtc cao. iu ny to ra khong trng 7 bit v khong trng c dng ghp t/h tlung cao khc.*Ngl hng ca CM T vi ghp cc bit //:-trao i khe tgian theo kiu // c thc hin = dng cc lung cao u vo v u ra. Miluong cao tg ng 8 g vt l v sdng 8 CM tgian ph.

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    -trong mi 1 b CM tgian f th ch c 1 bit trong 8 bit // ca mi knh th c ghi ng thi.(s)

    Chuyn mch khng gian S1.Ngl hng:CM kgian s cho fp i ch c khi tgian c cng ch s ca cc tuyn PCM khc nhau.(hv)i ch TSi-HW1 TSi-HW2

    2.Cu trc ca CM S:- CM S bgm 1 ma trn vi c h thng PCM nhp v xut. truyn bt k khe tgian notrong lung PCM ca ng nhp n khe tgian tng ng c cng ch s TS ca lung PCMca ng ra. Ta thch hp ca kgian s fi c kch hot trong khong tgian ca khetgian ny.(hv)

    truyn t/h ko c tr.Mi 1 ct trong ma trn c 1 b nh khinkhin ng m kt ni.tip im cu to gin bng pt AND.- trong CM S dng cc b nh khin khin kt ni.-Cc ta trong cng 1 ct c khin bi 1 b nh khin hay b nh kt ni.B nh ktni lu tr W nh = s khe tgian c trong 1 khung. Mt a ch di dng nh fn duynht c gn vo mi to trong 1 ct. i vi ct th nhta ch c ng trong khongtgian TS1 c lu tr trong nh s 1 ca b nh kt ni CM1. a ch c ng trongkhong tgian TS2 c lu tr trong nh th 2 ca b nh kt ni CM1 v tg t a chng trong khong tgian TSw c lu tr trong nh th w ca CM1.

    -Dung lg ca b nh CM:y/c kch thc nh ca b nh CM fi cha 1 a ch nh fn cho mi ta trong n ta v 1 ta gi cho tt c cc tip im trng thi m ( k kt ni).CCM = w.log2(n+1).w: s khe tgian khung u v...