Báo cáo chuyển mạch

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<p>Phn I : t Vn </p> <p>Li m u</p> <p> Ngy nay, trong ngnh cng nghip vin thng ang din ra s hi t ca vin thng vi cng ngh thng tin, hi t ca cc dch v thoi truyn thng v cc dch v d liu mi. iu ny c nh hng ln n mng vin thng, i hi mng vin thng phi c cu trc m, linh hot, cung cp nhiu loi dch v khc nhau cho ngi s dng, hiu qu khai thc cao, d pht trin... p ng cc yu cu ny, mt s nh sn xut thit b vin thng v mt s t chc nghin cu v vin thng a ra cc tng v m hnh v cu trc mng th h sau NGN. Trong xu th , ngnh vin thng Vit Nam cng ang c nhng bc chuyn bin v pht trin mi. Mng vin thng ca Tng Cng ty Bu chnh vin thng c s ho vi cc thit b hin i v cc loi hnh dch v ngy cng gia tng c v s lng v cht lng. Bn cnh VNPT, mt s cng ty khc cng v ang tng bc tham gia vo vic khai thc th trng cung cp cc dch v vin thng.</p> <p> Trong phn bo co ca mnh chng em xin trnh by s hiu bit ca mnh v nhng vn sau: Phn 1 t Vn : + Chng I : Tng quan h thng thng tin di ng GSM + Chng II : Khi nim chung v bo hiu Phn 2 Gii Quyt Vn : + Chng I : Bo hiu knh ring ( CAS ) + Chng II : Bo hi knh chung ( CCS )</p> <p>Phn 3 - Kt lun</p> <p>Phn I : t Vn </p> <p>Chng I : Tng quan mng di ng GSMI .1. Tng quan mng GMSCu hnh mng GSM :</p> <p> Trong : SS : Switching System - H thng chuyn mch AUC : Trung tm nhn thc VLR : B ghi nh v tm tr HLR : B ghi nh v thng tr EIR : Equipment Identified Reader - B ghi nhn dng thit b MSC : Mobile Switching Central - Trung tm chuyn mch cc nghip v di ng BSS : Base Station System - H thng trm gc BTS : Base Television Station - i v tuyn gc BSC : Base Station Control - i iu khin trm gc MS : My di ng OSS :Operating and Surveilance System - H thng khai thc v gim st. OMC : Operating and Maintaining Central - Trung tm khai thc v bo dng ISDN : Mng s lin kt a dch v PSTN : Mng in thoi mt t cng cng CSPDN : Mng chuyn mch s cng cng theo mch PLMN : Mng di ng mt t cng cng</p> <p> I.2 . Cu trc a l ca mng Mi mng in thoi u cn mt cu trc nht nh nh tuyn cc cuc gi vo n tng i cn thit v cui cng n thu bao b gi. Trong mng di ng cu trc ny rt quan trng do tnh lu thng ca cc thu bao trong mng. V mt a l mt mng di ng gm : Vng mng. Vng phc v. Vng nh v. (Cell).</p> <p> I.3. H thng trm gc BSS C th ni BSS l mt h thng cc thit b c th ring cho cc tnh cht t ong v tuyn ca GSM. BSS giao din trc tip vi cc trm di ng ( MS ) thng qua giao din v tuyn. V th n bao gm cc thit b pht v thu ng truyn v tuyn v qun l cc chc nng ny. Mt khc BSS thc hin giao din vi cc tng i SS. Tm li BSS thc hin u ni cc MS vi tng i v nh vy u ni nhng ngi s dng cc trm di ng vi cc ngi s dng vin thng khc. BSS cng phi c iu khin v v vy n c u ni vi OSS. BSS bao gm hai loi thit b : BTS giao din vi MS v BSC giao din vi MSC.</p> <p> I.4. Trm di ng MS Trm di ng l thit b duy nht m ngi s dng c th thng xuyn nhn thy ca h thng. MS c th l thit b t trong t hay thit b xch tay hoc cm tay. Loi thit b nh cm tay s l thit b trm di ng ph bin nht. Ngoi vic cha cc chc nng v tuyn chung v x l giao din v tuyn, MS cn phi cung cp giao din vi ngi s dng ( nh micro, loa, mn hin th, bn phm qun l cuc gi ) hoc giao din vi mt s cc thit b khc nh giao din vi my tnh c nhn, Fax ... Hin nay ngi ta ang c gng sn xut cc thit b u cui gn nh u ni vi trm di ngChng II: Khi qut chung v bo hiu</p> <p>II.1. Gii thiu chung</p> <p>II.2.Cc loi bo hiuII.2.1.Bo hiu ng dy thu bao bt u mt cuc gi, mt thu bao nhc my, hnh ng ny to ra mt tn hiu gi n tng i bo cho tng i bit rng thu bao mun to mt cuc gi.</p> <p> II.2.2. Bo hiu lin i Bo hiu lin i gm cc thng tin c trao i gia cc tng i, l cc tn hiu bo hiu ng v cc tn hiu bo hiu thanh ghi.</p> <p> II.3. Cc chc nng ca bo hiu Chc nng gim st Cc chc nng tm chn Cc chc nng vn hnh - qun l mng</p> <p>Phn II : Gii quyt vn </p> <p> Chng I : Bo hiu knh ring (bo hiu knh lin kt ) CAS I.1. Tng quan Bo hiu knh ring CAS ( Channel Associated Signalling) c hiu sut bo hiu khng cao do 1 cuc gi chim 2 knh (knh cho thoi v knh cho bo hiu). Khi knh bo hiu ny tn ti trong sut thi gian cuc gi d cuc gi c truyn tin hay khng (thng thng cc thng tin bo hiu li ch c truyn trc khi v sau khi kt thc cuc gi). Dn n s lng ph khng thun tin nht l cho cc cuc gi chim nhiu thi gian (nh cc cuc gi truyn d liu V s dng m bo hiu nn s lng cc thng tin bo hiu rt t do hn ch cc kh nng iu khin , thng tin bo hiu cho cc dch v gi tr gia tng qua mng Knh bo hiu c truyn kt hp cng tuyn vi knh cuc gi do vy kh nng tm kim v nh tuyn km cho cc u cui khng c nh, ng thi lm tng lu lng mng bo hiu trong qu trnh tm kim thu bao di ng do hn ch kh nng ng ngy cng cao ca cc dch v gi tr gia tng ..</p> <p>Hnh 3.1 M hnh mng bo hiu CAS i cng vi mng thng.</p> <p> I.2. H thng bo hiu R2 ca CCITT H thng bo hiu R2 l h thng bo hiu knh ring (CAS), c thit k cho chc nng trao i thng tin bo hiu gia cc tng i trong mng vin thng s hp nht hoc mng kt hp s vi tng t. Mi tn hiu trao i l t hp ca mt cp tn s (MFC). H thng bo hiu R2 gm hai loi tn hiu to thnh, l: - Tn hiu bo hiu ng. - Tn hiu bo hiu thanh ghi. a) Bo hiu ng Cc tn hiu trong bo hiu ng c phn chia theo hng i v hng v. Hng i gm cc tn hiu:- Tn hiu chim ng- Tn hiu gii phng hng i Hng v gm cc tn hiu:- Tn hiu xc nhn chim- Tn hiu tr li- Tn hiu gii phng hng v- Tn hiu kho</p> <p>b) Bo hiu thanh ghi</p> <p> Khi thc hin chuyn mch mt cuc gi c lin quan n nhiu tng i, cn phi chuyn cc thng tin v cc con s gia cc tng i kt cui cuc gi c chnh xc n thu bao mang mun. Thng tin v cc con s c chuyn theo hng i, nhng iu khin qu trnh thit lp gi, cn phi chuyn mt s cc tn hiu theo hng ngc li. Cc tn hiu hng i gm: - Thng tin con s a ch - Thuc tnh thu bao ch gi - Thng tin thng bo kt thc gi a ch b gi - Thng tin v con s ca thu bao ch gi cho tnh cc chi tit Cc tn hiu hng v gm: - Tn hiu thng bo tng i b gi sn sng nhn cc con s a ch ca thu bao ch gi. - Cc tn hiu iu khin xc nhn kiu thng tin. - Thng tin kt thc qu trnh chn, thng tin ny gii phng thanh ghi v thit lp tuyn thoi. ng thi n cn a ra cc thng tin v trng thi t hp ca thu bao b gi. - Thng tin tnh cc. Thng tin a ch mang mt lng tin ln v n c cc nguyn l c bn chuyn thng tin gia cc tng i trong mng nh sau: - Kiu tng chng (Link By Link) - Kiu thng sut ( End To End) - Kiu hn hp (Mixed)</p> <p> Ta c th m t cc kiu bo hiu ny bng v d gia thu bao ch gi A thit lp cuc gi trung k vi thu bao b gi B. Mi thu bao c m vng ring v vic lin lc c thc hin theo tng cp.</p> <p>Tu thuc vo v tr ca tng i v s phn cp qun l ca mng m ta s s dng kiu bo hiu no cho hp l Chng II : Bo hiu knh chung CCS II.1. Tng quan Bo hiu knh chung (CCS: Common Channel Signalling) khc phc c nhc im ca phng thc bo hiu knh ring v mt hiu sut s dng knh bo hiu. Vi phng thc bo hiu knh chung, knh bo hiu phn pht cho knh ting ni ch trong tng khong thi gian bo hiu. Ngi ta s dng mt tuyn thng tin s liu ring bit chuyn dng cho cng vic bo hiu.</p> <p> H thng bo hiu knh chung CCS c mt chm knh bo hiu. Chm knh ny ch c phn pht cho mt knh ting ni c nhu cu bo hiu trc nht. Nh vy cc knh ting ni cn c xp theo th t ch knh bo hiu ri. Dung lng knh bo hiu ph thuc vo ni dung bo hiu, tn sut s dng mi knh ting ni. Chnh v vy thit b bo hiu c th c tp chung ho, ch to gn gng hn. N to ra u im v mt kinh t. Tuy nhin phng thc bo hiu ny ch s dng cho cc tng i SPC trao i bo hiu lin i gia cc b vi x l.</p> <p> II.2. H thng bo hiu s 7 ca CCITT II.2.1. im bo hiu im bo hiu (SP-Signalling Point) l nt chuyn mch hoc x l trong mng bo hiu c th thc hin cc chc nng ca h thng bo hiu s 7 ca CCITT. Tng i in thoi c chc nng nh l im bo hiu th phi l tng i loi iu khin bng chng trnh lu tr SPC v bo hiu s 7 l thng tin s liu gia cc b x l. Tt c cc im bo hiu trong mng bo hiu s 7 c nhn dng bng mt m duy nht (14 bit) c gi l m ca im bo hiu.</p> <p> II.2.2. Knh bo hiu / Chm knh bo hiu H thng bo hiu knh chung s dng cc knh bo hiu (SL) chuyn ti thng tin bo hiu gia hai im bo hiu. V mt vt l, knh bo hiu bao gm kt cui bo hiu mi u ca knh v vi loi mi trng truyn dn (thng l khe thi gian ng truyn PCM) u ni 2 kt cui bo hiu. Mt s cc knh bo hiu song song u ni trc tip hai im bo hiu vi nhau to thnh chm knh bo hiu.</p> <p> II.2.3. Cc phng thc bo hiu</p> <p> Cc im bo hiu m thng tin bo hiu i qua c gi l cc im chuyn giao bo hiu (STP).</p> <p> II.2.4. Cc loi im bo hiu im bo hiu ni m thng tin bo hiu c to ra c gi l im ngun. im bo hiu ni m thng tin bo hiu i n ch gi l im ch. im bo hiu ni m thng tin bo hiu thu c trn mt knh bo hiu v sau chuyn giao cho cc knh khc m khng x l ni dung ca tin bo th c gi l im chuyn giao bo hiu (STP). phng thc bo hiu gn kt hp, tin bo c chuyn qua mt hoc nhiu STP trn ng t im ngun ti im ch. II.2.5. Tuyn bo hiu / Chm tuyn bo hiu Tuyn bo hiu l mt ng c xc nh trc tin bo i qua mng bo hiu gia im bo hiu ngun v im bo hiu ch. Tuyn bo hiu bao gm mt chui SP/STP v c u ni vi nhau bng cc knh bo hiu. Tt c cc tuyn bo hiu m thng tin bo hiu c th s dng i qua mng bo hiu gia im bo hiu ngun v im bo hiu ch c gi l chm tuyn bo hiu cho mi quan h bo hiu .</p> <p> II.2.6. Cc bn tin bo hiu bo hiu knh chung, thng tin bo hiu c truyn ti theo cch khc so vi cc h thng bo hiu truyn thng m cc tn hiu c truyn ti dng xung, cc tone, cc m tone ... h thng bo hiu s 7 (SS7) ca CCITT, thng tin bo hiu c truyn ti cc khi tn hiu, tc l cc gi cc con s nh phn (0,1) b tr nh l bn ghi s liu vi cc trng, trong cc t hp bit c ngha khc nhau. Thc cht SS7 ca CCITT l mt dng thng tin s liu chuyn mch gi. Trong SS7 ca CCITT c 3 loi n v tn hiu : Khi tn hiu tin bo (MSU - Message Signal Unit) cha cc thng tin bo hiu. Khi tn hiu trng thi knh (LSSU - Link State Signal Unit) c s dng iu hnh cc knh bo hiu. Khi tn hiu lm y FISU c s dng nh l lm y cc tn hiu v chp nhn.</p> <p>35</p> <p> Hnh 4.5 Cc n v tn hiu trong SS7 ca CCITT hnh trn : F = c hiu CK = kim tra SF = trng trng thi SIF = trng thng tin bo hiu SIO = octet thng tin dch v LI = phn t ch th di</p> <p> II.2.7. Cc khun dng v m tin bo n v tn hiu bao gm mt s trng. Mt trng ( MSU), l trng thng tin bo hiu (SIF - Signalling Information Field) phi lm vic vi cc phn ca ngi s dng, tt c cc trng khc cha thng tin cho phn chuyn giao bo hiu (MTP). Trng thng tin bo hiu cha thng tin bo hiu phn ca ngi s dng v nhn hiu.</p> <p>`</p> <p>Phn III : Kt lun</p> <p> Bo hiu l 1 thc th khng th thiu trong cc h thng thng tin ni chung v mng di ng GSM ni ring . H thng cng hin i v phc tp th cng phi c h thng bo hiu mnh v chnh xc.Trong bi vit ny chng em trnh by Gii thiu cc phng thc bo hiu. Qua qu trnh tm hiu v c s gip ca thy gio trong qu trnh lm bi chng em hon thnh bi bo co ca mnh. Do vn kin thc cn hn ch nn khng th trnh c mt s sai st .Chng em mong c ng gp kin bi vit ca mnh c hon thin hn. Chng em xin chn thnh cm n s hng dn ca thy gio Ths. Hong Trng Minh.</p>