Chng 1

Tm hiu v ADSL

Mc lc

Li ni uChng 1. c im tnh hnh ca huyn v tnh hnh pht trin ADSL ti Chi Lng.1.1 c im tnh hnh1.2 Tm hiu lnh vc hot ng ca n v thc tp1.3 Tnh hnh pht trin ADSL ti Chi Lng

1.3.1 S ra i ca k thut ADSL

1.3.2 Cng ngh ADSL ti Chi Lng

1.3.3 Cc nh cung cp ng truyn ADSL ti Chi Lng

1.3.4 Tm hiu cch thanh ton cc ph thu bao ADSL

1.3.5 DLAM mt s cng DLAM ti Chi Lng

Chng 2. Tng quan v ADSL2.1. Gii thiu tng quan k thut xDSL 2.2. Tng quan v cng ngh xDSL 2.2.1. c im ca cng ngh xDSL

2.2.2. u im ca cng ngh xDSL 2.2.3. Nhng thch thc chnh ca cng ngh xDSL

2.3. K thut ADSL

2.3.1. Khi nim v ADSL2.3.2. ng dng ca ADSL

2.3.3. C ch hot ng v di tn ca ADSL

2.3.3.1. C ch hot ng

2.3.3.2. Di ph tn ca ADSL

2.3.4. u im ca ADSL so vi PSTN & ISDN

2.3.5. Cc thnh phn ca ADSL

2.3.5.1. Khi nim v Modem ADSL 2.3.5.2. Modem ADSL lm vic nh th no

2.3.5.3. Mch vng/Local Loop l g

2.3.6. Cc thnh phn ADSL t pha nh cung cp dch v

2.3.6.1. Khi nhim v DLAM2.3.6.2. Khi nim v BAS2.3.6.3. Khi nim ISP2.3.7. Cc thnh phn khc ca h thng ADSL

2.3.8. Kt ni mng

2.3.8.1. Cc giao thc c s dng gia modem v BAS

2.3.8.2. Vai tr ca ATM

2.3.9. Vai tr ca PPP

2.3.10. Modem ADSL trn thc t

2.3.11. Mi tng quan gia thoi v ADSL

2.3.11.1. Thoi v ADSL chung sng ra sao

2.3.11.2. Tc a dng

2.4. ADSL mang li g cho ngi dng, doanh nghip 2.4.1. i vi ngi dng

2.4.2. i vi doanh nghip v cc t chc x hi

Chng 3: Kt lun

LI NI U

Nhng nm u ca th k XXI, c coi l k nguyn ca cng ngh thng tin, thng tin hc c ngha n s thnh cng v pht trin ca mt quc gia.

Trong giai on cng nghip ho - hin i ho, nhu cu tm kim v trao i thng tin lm cho mng Internet ra i. Cc c quan, t chc u nhn thc c tnh u vit ca x l thng tin qua mng. Kt ni mng khng th thiu cho cc hot ng x hi ni chung v cng ngh thng tin ni ring.

Cng vi s pht trin ca cng ngh thng tin, cng ngh ADSL ra i p ng cho vic x l thng tin mt cch thun tin nhanh chng, chnh xc v t hiu qu trong cng vic. Chng I. c im tnh hnh ca huyn v tnh hnh pht trin ADSL ti Chi Lng . 1.1. c im tnh hnh: Chi Lng l huyn nm pha Nam ca tnh Lng Sn, pha ng gip huyn Lc Bnh, pha Ty gip huyn Vn Quan, pha Bc gip huyn Cao Lc, pha Nam gip huyn Hu Lng, v huyn Lc Ngn ca tnh Bc Giang. huyn Chi Lng c chia thnh 21 n v hnh chnh, trong c 02 th trn v 19 x.

Huyn Chi Lng nm trn trong vng nhit i gi ma, c din tch t nhin 704, 81 km2 , trong ni v i chim 3/4 din tch; c nhit trung bnh l 21,50C, vi lng ma bnh qun gn 1.500 mm.

Kinh t x hi: Nhp tng trng kinh t bnh qun hng nm 12,92%, vt 0,92% so vi mc tiu; GDP bnh qun u ngi n nay l 15,22 triu ng, tng 10,32 triu ng so vi nm 2005, t 184,48% so vi mc tiu ra; t trng cc ngnh trong c cu kinh t ngnh nng, lm nghip v thy sn chim 61,76%, cng nghip v xy dng chim 11,75%, cc ngnh thng mi - dch v chim 26,49%. Gi tr sn xut nm 2005 ngnh nng nghip chim 78,17%, lm nghip chim 28,4%, thu sn 0,43% n nm 2010 ngnh nng nghip chim 79,70%, lm nghip chim 20,01%, thu sn 0,29%.

Nng nghip pht trin kh theo hng y mnh thm canh cy lng thc, duy tr, u t pht trin cc vng sn xut tp trung v cy n qu, cy ly g, cy cng nghip. Tch cc u t thm canh tng v, nng h s s dng rung t tng ln 1,92 ln nm 2010. Tng sn lng lng thc c ht tng qua cc nm, n nay l 32.750 tn, tng 3.681 tn so vi nm 2005, t 101,15% so vi mc tiu. Lng thc bnh qun u ngi l 441 kg/ngi/nm, t 112,98% so vi mc tiu ra. hnh thnh cc vng sn xut tp trung nh vng Na dai th trn Chi Lng, x Chi Lng, x Quang Lang, th trn ng M; vng Vi thiu cc x: Quan Sn; vng Hi Gia Lc, Thng Cng; cc cy Nhn, Hng, Khoai ty, Da hu khu vc dc quc l; vng trng Thuc l cc x khu vc ni nh: x Y Tch, Ho Bnh, Gia Lc, Vn Linh, Thng Cng...tng din tch cy n qu cc loi ton huyn l 3.100 ha, t 51,67% so vi mc tiu. Ring cy Na c xc nh l th mnh ca Huyn nn trong nhng nm qua c cc cp, cc ngnh quan tm u t, hin nay tng din tch vng Na c khong 1.450 ha, sn lng hng nm t 7.800 tn, tng thu nhp t cy Na ca nhn dn t trn 14 t ng. Gio dc - o to: Nm hc va qua c nhiu chuyn bin tin b, quy m ngy cng m rng, cht lng dy v hc c nng ln. T l hc sinh kh, gii cc bc hc hng nm u tng. T l gio vin t chun tr ln v trnh o to ca cc cp hc t MN n THPT l 90%, cht lng i ng cn b qun l gio dc tng bc c nng ln c v nng lc qun l v trnh l lun chnh tr. Hot ng Vn ho Thng tin - Th thao v Truyn thanh - truyn hnh: nhiu lin hoan, hi din, giao lu v thi u c t chc mang li kt qu tt. Cuc vn ng phong tro Ton dn on kt xy dng i sng vn ho, c ng o nhn dn hng ng thc hin em li hiu qu thit thc, nh cc phong tro xy dng Gia nh vn ho, Lng vn ho, c quan, n v, trng hc vn ho. Lnh vc Y t, Dn s k hoch ho gia nh: c quan tm c nhiu c gng trong phng chng dch bnh v khm cha bnh cho nhn dn, nht l nhn dn cc x vng 3, cc h ngho. Trnh chuyn mn v y c ca i ng y, bc s tng bc c nng ln1.2 Tm hiu lnh vc hot ng ca n v thc tp.

Trung tm Vin thng Chi Lng trc thuc Vin Thng Lng Sn chuyn kinh doanh cc sn phm dch v vin thng cng ngh thng tin trn a bn huyn Chi Lng, m bo thng tin lin lc thng sut cho cc ban ngnh on th, cc doanh nghip, v ngi dn trn a bn huyn. 1.3 Tnh hnh pht trin ADSL ti Chi Lng

1.3.1 S ra i ca k thut ADSL

Trc khi Vit Nam chnh thc ha vo mng ton cu t cui nm 1997 th c lc c mt s dch v Internet t nhn xut hin ti cc thnh ph ln nh: H Ni, t/p H Ch Minh,...Tuy nhin lc ny do h tng mng nc ta cha c nn tc cn rt chm, gi thnh truy cp mng li cao. Trc nhu cu pht trin ca cng ngh thng tin trong nc, i hi cn phi nng cp ng truyn dn Internet theo ng c (cng ngh Analog) do gi thnh cao hay tc chm. Thng 7/2003, b bu chnh vin thng cp php cho cc doanh nghip vin thng cung cp dch v truy cp Internet tc cao ADSL. Hi phng l thnh ph u tin trong c nc c s dng cng ngh ADSL. T thng 2/2002, tp on KT (Hn Quc) phi hp vi VNPT trin khai th nghim cng ngh ADSL ti Hi Phng. T n nay tc pht trin ca truy cp Internet tc cao ADSL pht trin nhanh chng ti nc ta cng nh cc nc trn th gii.

1.3.2. Cng ngh ADSL ti Chi Lng

Ti Chi Lng, cng ngh ADSL c a vo khai thc v s dng t nm 2005, vi thit b ban u l thit b IPAM dung lng 16 port. n nay tt c cc thit b ban u l thit b IPAM dung lng t c thay bng cc thit b IPDSLAM s dng cng ngh Man_E kt ni cp quang, dung lng ln p ng c cc dch v bng rng truyn thng l ADSL v hin i hn l dch v truyn hnh theo yu cu MyTV. Vi 15 trm thit IPDSLAM dung lng lp t hn 3.000 port p ng nhu cu s dng trn a bn.

Vin thng Chi Lng s dng cng ngh ng dy bt i xng qua cp ng, c cung cp t nhiu thit b nh: DSLAM (IP hoc ATM). T thit b IP DSLAM c th cung cp c nhiu dch v nh: ADSL, Megawan, MyTV, ng truyn s liu.

1.3.3 Cc nh cung cp ng truyn ADSL ti Chi Lng

Hin nay trn a bn huyn Chi Lng c 02 nh cung cp dch v bng rng l Trung tm Vin thng Chi Lng thuc VNPT v Chi nhnh Viettel. Trong th phn ca VNPT chim n 98% trn a bn, do mng li c u t ng b t huyn n x nn dch v ADSL ca VNPT p ng c nhu cu s dng ca khch hng trn a bn, c bit l phc v nhim v chnh tr trong vic cung cp ng truyn s liu Megawan cho Huyn y, UBND huyn cc c quan, doanh nghip trn a bn huyn v ng y 21 x th trn trn a bn huyn Chi Lng v x Ha Lc thuc huyn Hu Lng.

- VNPT hin ang l nh cung cp ng truyn ln nht ti Lng sn ni chung v huyn Chi Lng ni ring.- VNPT a ra nhiu loi hnh dch v kt ni bng thng rng. Khi s dng dch v ny ca VNPT, bn s c cung cp min ph a ch Email, h tr k thut 24/24h. Hin nay s thu bao ADSL ca VNPT ti Vin thng huyn Chi Lng t trn 900 thu bao.DCH VNI DUNG

ADSL

(Internet MegaVNN)- Khch hng ng k mi: Tng 50% ph lp t dch v

+ Tng 30.000/thng cc cc s dng

- Khch hng ng k trn ng dy c sn:+ Min ph ho mng dch v

+ Tng 30.000/thng cc s dng- Hnh thc 1: Khch hng mn modem

+ Tng 30.000/thng/2 thng

- Hnh thc 2: Khch hng khng mn modem

+ Tng 30.000/thng/4 thng

Goi cuoc ADSL VNPTMega BasicMega EasyMega FamilyMega MaxiMega Pro

2.560Kbps/512Kbps4,096Kbps/640Kbps5.120Kbps/640Kbps8.192Kbps/640Kbps10.240Kbps/

640Kbps

KhngKhng256Kbps/

256Kbps512Kbps/

512Kbps512Kbps/

512Kbps

Khng p dng24.000 /thng35.000 /thng100.000 /thng200.000 /thng

-Cho 400Mbyte u tin: 18.181 ng.

-Mi Mbyte tip theo: 60 ng

45 /MB48 /MB50 /MB50 /MB

200.000 /thng300.000 /thng450.000 /thng1.100.000 /thng1.600.000 /thng

180.000 /thng250.000 /thngKhng p dng900.000 /thng1.400.000 /thng

IP ngIP ngIP ngIP ngMin ph 01 IP tnh

1.3.4 Tm hiu cch thanh ton cc ph thu bao ADSL

Hin nay cc nh cung cp dch v ADSL cung cp hai hnh thc thanh ton cc ph chnh l:

Hnh thc tnh ph trn gi.

Hnh thc tnh ph theo lu lng s dng.

Tuy nhin vic la chn hnh thc thanh ton cc ph nhu th no hon ton ph thuc vo nhu cu s dng Internet ca khch hng bi v mi hnh thc tnh cc u c nhng u nhc im ring: Tnh ph trn gi (Flat Charge)Tnh ph theo lu lng s dng (Volume Charge)

u im - D dng qun l cc ph s dng hng thng - Khng phi lo lng cc ph s tng khi s dng nhiu - Dng nhiu nhng li phi tr t tinu im - S dng bao nhiu tr tin by nhiu

Nhc im i khi khng s dng Internet nhng vn phi tr tinNhc im - Kh qun l khi c nhiu ngi cng s dng Internet - kh nng mc cc tng rt cao khi s dng nhiu

Ph hp vi nhng khch hng c nhn c nhu cu s dng nhiu, cc doanh nghip cc t chc, cc vn phngPh hp vi cc c nhn

Khch hng c 2 cch thanh ton l :

* Tin mt

+ Thu ti nh thu bao

+ Thu ti quy giao dch

* Chuyn khon qua ngn hng

1.3.5 DLAM - mt s cng DLAM ti Chi Lng

DSLAM (Digital Subscriber Line Access Multiplexer) - B dn knh truy nhp ng thu bao s - l mt thit b u cui DSL c t ti a im ca nh cung cp dch v mng. DSLAM tp trung lung d liu t cc mch vng DSL v t hp thnh tc cao hn nh tc T1, E1 hoc tc ATM ca OC-3 (155 Mbps)....ri a ti Internet hay mng d liu

Mt s cng DSLAM

- DSLAM Chi Lng

- DSLAM M

- DSLAM Than Mui

- DSLAM Ni

- DSLAM Ha Bnh

- DSLAM X Nhn L

- DSLAM X Mai Sao

- DSLAM ng Bnh

- DSLAM Sng Ho

Chng II Tng quan v ADSL.2.1. Gii thiu tng quan k thut xDSLMng vin thng ph bin trn th gii hay nc ta hin nay l mng s lin kt (IDN - Integrated Digital Network). Mng IDN l mng vin thng truyn dn s, lin kt cc tng i s v cung cp cho khch hng cc ng truyn dn thu bao tng t. Trong xu hng s ho mng vin thng trn ton th gii, mng lin kt s a dch v ISDN ( Intergated Services Digital Network) v ng dy thu bao s DSL ( Digital Subcriber Line) p ng c nhim v s ho mng vin thng n tn pha khch hng. C th ni rng dch v ISDN l dch v DSL u tin cung cp cho khu dn c giao din tc c s BRI (Basic Rate Interface): 44 Kbit/s, c cu thnh t hai knh B 64 Kbit/s v mt knh D 16 Kbit/s.

Ngy nay i i vi mng ISDN mt cng ngh mi c nhiu trin vng vi tn gi chung l xDSL, x biu th cho cc k thut khc nhau. Mc ch ca k thut ny l cung cp cho khch hng cc loi hnh dch v cht lng cao v bng tn rng.

Cc k thut c phn bit da vo tc v ch truyn dn. K thut ny c th cung cp nhiu dch v c th truyn khng i xng qua modem, in hnh loi ny l ADSL v VDSL v truyn i xng c tc truyn hai hng nh nhau nh HDSL v SDSL. Ring vi k thut VDSL (Very High Speed DSL) c th truyn i xng vi tc rt cao.

Cc c trng chnh ca h cng ngh xDSL hin ti c m t trong bng 2.1

K thutTc d liuS i dy s dngGii hn khong cchng dng

56 Kbit/s56Kbit/s downlinkKhng gii hnEmail, truy nhp LAN t xa.

Analog modem28,8 hoc 33,6 Kbit/s uplinkTruy nhp Internet, intranet

ISDN128 Kbit/s (Khng nn)i xng5 Km (thm thit b c th m rng khong cch)Hi ngh truyn hnh, D phng leased line.Cc hot ng thung mi truy cp Internet/ intranet

Cable modem10 - 30Mbit/s Downstream0,128 - 10 Mbit/s Upstream50Km trn cp ng trc (thm thit b ph tr c th ti 300 Km)Truy cp Internet

ADSL Lite1Mbit/s Downstream512 Kbit/s UpstreamS dng 1 i dy5 KmTruy cp Internet/ Intranet, duyt Web, thoi IP, thoi video.

Full rate ADSL1,5 Mbit/s Downstream1,544 Mbit/s UpstreamS dng 1 i dy5Km (khongcch cng ngn tc cng cao )Truy nhp Internet/ intranet,video theo yu cu, truy cp mng LAN t xa, VoIP.

ISDL144 Kbit/s

i xng5 Km (C th m rng ti 300 km)Truy nhp Internet/ intranet, video theo yu cu, truy cp mng LAN t xa, VoIP.

HDSL1.544 Mbit/s (T1) i xng2.048 Mbit/s (E1) i xngS dng 1-3 i dyS dng 2 i dy.3,6 Km - 4,5 KmNi ht, thay th trung k T1/E1 c dng b lp. Kt ni cc PBX vi nhau.Tp trung lu lung Frame Relay, kt ni cc mng LAN

SDSL10544 Mbit/s full duplex (T1)2.048 Mbit/s full duplex (E1)S dng 1 i dy3 KmNi ht, thay th trung k T1/E1 c dng b lp, kt ni cc PBX vi nhau, kt ni cc mng LAN.

VDSL13-52 Mbit/s Downstream1.5-2.3 Mbit/s Upstream(i xng t ti 34 Mbit/s )S dng 1 i dy300- 1.5 Km(ph thuc vo tc )Truy cp Multimedia Internet, qung b cc chng trnh TV.

Ni chung k thut xDSL l k thut truyn dn dy cp ng, n gii quyt nhng vn tc nghn gia nhng nh cung cp cc dch v mng v nhng khch hng s dng dch v mng .

K thut xDSL t c nhng tc bng tn rng trn mi trng mng ph bin nht trn th gii l ng dy cp in thoi thng thng.

2.2. Tng quan v cng ngh xDSL

2.2.1. c im ca cng ngh xDSL

- Tc truyn d liu thay i tu theo tng phin bn ca cng ngh xDSL v di ca mch vng thu bao.

- i vi ADSL, chun ADSL ca ITU-T xc nh tc hng truyn xung l 6.1 Mbit/s v 640 Kbit/s hng ln.

- Trong thc t tc ti a 6.1 Mbit/s ch c th t c nu khong cch di 2,7 Km v gim ti 1,5 Mbit/s hoc thp hn na khong cch 4,5 Km.

- Phin bn c tc cao nht l VDSL, h tr ti a ng xung l 55 Mbit/s khong cch 300 m v 13 Mbit/s nu khong cch l 1,4 Km. Tc hng ln nm trong khong 1,6 2,3 Mbit/s.

- Mi ngi s dng c mt ng ring kt ni vi DSLAM t ti tng i hoc RT (trm thit b tp trung thu bao).

- Cc dch v h tr: Truyn s liu v VoDSL (vi voice gateway).

ADSL chia s cng ng cp ng vi thoi tng t.

VDSL c th h tr cho chuyn mch truyn hnh.

- Yu cu k thut

ng cp ng sch, khng c cun cm ko di (loading

coil), khng r nhnh (bridge tap).

Hn ch khong cch ng truyn khong di 4,5 Km.

Khng s dng cc thit b DLC trong mch thu bao, nu c DLC th DSLAM phi t ti cc RT.

- Thit b khch hng ngoi XDSL modem.

Voice gateway nu dng VoDSL.

2.2.2. u im ca cng ngh xDSL.- Cng ngh c kim nghim vi nhiu triu line hot ng trn khp th gii. Chu Hn Quc l nc c mt thu bao ADSL cao nht.

- Chun ho bi ITU-T.

- S dng h thng cp ng c trin khai rng khp cc nh khai thc.

- Trong iu kin thun li, u t cho mng DSL khng ln i vi nh khai thc.

2.2.3. Nhng thch thc chnh ca cng ngh xDSL

- Kh khn khi trin khai mng li, do mng truy nhp khng ng b.

- Chm sc khch hng, tnh cc.

- Trin khai cc dch v gia tng.

- Hn ch bi khong cch v nhng h thng tp trung thu bao cng ngh c trin khai.

- Trin vng doanh thu tng i tt i vi cc nh khai thc ch o, c c s h tng vin thng rng khp, nhng s rt kh khn cho cc nh khai thc cnh tranh. iu ny c kim nghim trn th trng vin thng M. Trong nhng nm qua nhiu nh khai thc nh lin tc b thua l v phi ng ca.

Cng ngh xDSL hng ti th trng chnh l t nhn v cc doanh nghip va v nh. Dch v ny c th khng tng thch vi nhiu doanh nghip ln, do cht lng phc v khng thng xuyn c m bo. D kin trong mt vi nm ti, Vit Nam, con s thu bao ADSL s ln ti hng nghn. Ti Vit Nam, nhng vn v cht lng cp, cht lng u ni trong mng truy nhp cng nh mt s thit b tp trung thu bao gm nhiu chng loi khc nhau, s dng cc cng ngh khc nhau trong nhng yu t k thut quan trng cn lu khi pht trin thu bao xDSL.

2.3. K thut ADSL

2.3.1. Khi nim v ADSL ?

ADSL (Asymmetric Digital Subscriber Line) - l ng thu bao s khng i xng, k thut truyn c s dng trn ng dy t modem ca thu bao ti Nh cung cp dch v.

Hiu mt cch n gin nht, ADSL l s thay th vi tc cao cho thit b modem hoc ISDN gip truy nhp Internet vi tc cao v nhanh hn. Cc biu sau ch ra cc tc cao nht c th t c gia cc dch v cung cp.

Asymmetric: Tc truyn khng ging nhau hai chiu. Tc ca chiu xung (t mng ti thu bao) c th nhanh gp hn 10 ln so vi tc ca chiu ln (t thu bao ti mng). iu ny ph hp mt cch tuyt vi cho vic khai thc dch v Internet khi m ch cn nhn chut (tng ng vi lu lng nh thng tin m thu bao gi i ) l c th nhn c mt lu lng ln d liu ti v t Internet.

Digital: Cc modem ADSL hot ng mc bit (0 v 1) v dng chuyn thng tin s ho gia cc thit b s nh cc my tnh PC. Chnh kha cnh ny th ADSL khng c g khc vi cc Modem thng thng.

Subscriber Line: ADSL t n ch hot ng trn ng dy thu bao bnh thng ni ti tng i ni ht. ng dy thu bao ny vn c th c tip tc s dng cho cc cuc gi i hoc nghe in thoi cng mt thi im thng qua thit b gi l splitters c chc nng tch thoi v d liu trn ng dy.

Mch ADSL to nn 3 knh thng tin trn i dy thu bao:

Mt knh tc cao t tng i ti thu bao.

Mt knh tc trung bnh 2 chiu (ph thuc vo cu trc ca ADSL) Mt knh thoi hoc mt knh N-ISDN.Tc n v m ADSL c th cung cp l 1,5 hoc 2 Mbit/s trn mt knh t tng i n thu bao v 16 Kbit/s trn mt knh hai hng. Modem ADSL tng thch vi truyn dn ATM, giao thc IP, bng vic thay i tc truyn v ph hp vi cc mo u ca ATM cng nh IP. Bng 2-2 a ra khong cch ti a cho php m vn m bo cht lng truyn dn mt s tc nht nh.

Tc (Mbps)Loi dyKch thc dy(mm)khong cch truyn (m)

1,5 2,024 AWG0,55500

1,5 2,026 AWG0,44600

6,124 AWG0,53700

6,126 AWG0,42700

Bng 2.2 khong cch ti a cho php ca ADSL

2.3.2. ng dng ca ADSL

ADSL xc lp cch thc d liu c truyn gia thu bao (nh ring hoc cng s) v tng i thoi ni ht trn chnh ng dy in thoi bnh thng. Chng ta vn thng gi ng dy ny l local loop.

Thc cht ca ng dng ADSL khng phi vic truyn d liu i/n tng i in thoi ni ht m l to kh nng truy nhp Internet vi tc cao. Nh vy, vn nm vic xc lp kt ni d liu ti Nh cung cp dch v Internet.

Mc d chng ta cho rng ADSL c s dng truyn d liu bng cc giao thc Internet, nhng trn thc t vic thc hin iu nh th no li khng phi l c trng k thut ca ADSL.

Hin nay, phn ln ngi ta ng dng ADSL cho truy nhp Internet tc cao v s dng cc dch v trn Internet mt cch nhanh hn.

2.3.3. C ch hot ng v di tn ca ADSL

2.3.3.1 C ch hot ng:

ADSL tm cch khai thc phn bng thng tng t cn cha c s dng trn ng dy ni t thu bao ti tng i ni ht. ng dy ny c thit k truyn ti ni ht. ng dy ny c thit k truyn ti di ph tn s (frequency spectrum) chim bi cuc thoi bnh thng. Tuy nhin, n cng c th truyn ti cc tn s cao hn di ph tng i hn ch dnh cho thoi. l di ph m ADSL s dng.

Thoi c bn s dng di tn s t 300 Hz ti 3,400 Hz.

By gi chng ta s xem xt, thoi v d liu ADSL chia x cng mt ng dy thu bao ra sao. Trn thc t, cc splitter c s dng m bo d liu v thoi khng xm phm ln nhau trn ng truyn.

Cc tn s m mch vng c th truyn ti, hay ni cch khc l khi lng d liu c th truyn ti, s ph thuc vo cc nhn t sau:

Khong cch t tng i ni ht.

Kiu v dy ng dy.

Kiu v s lng cc mi ni trn ng dy.

Mt cc ng dy chuyn ti ADSL, ISDN v cc tn hiu phi thoi khc.

Mt cc ng dy chuyn ti tn hiu radio.

2.3.3.2 Di ph tn ca ADSL

ADSL chia di tn ca mt cp cp xon (1Mhz) thnh ba bng tn, nh trong hnh 2.1 di y. Bng tn u tin, bnh thng khong 0 v 25 Khz, c s dng cho dch v thoi thng thng (c bit n nh dch v thoi c). Dch v ny ch s dng 4 Khz ca knh d liu ny. Bng tn th hai, nm gia 25 v 200 Khz, c s dng cho dch v truyn thng Upstream (ti d liu ln mng). Bng tn th ba, nm trong khong t 250 n 1Mhz, c s dng cho dch v truyn thng Downstream (ti cc d liu trn mng xung my tnh c nhn hay mng ni b). S gi ln nhau v rng buc gia cc dch v Upstream v Downstream cung cp nhiu di tn hn bn pha Downstream.

2.3.4. u im ca ADSL so vi PSTN & ISDN

(1) PSTN v ISDN l cc cng ngh quay s (dial-up)

ADSL l lin tc/ always-on tc kt ni trc tip.

(2) PSTN v ISDN cho php chng ta s dng fax, d liu, thoi, d liu ti Internet, d liu ti cc thit b khc.

ADSL ch truyn ti d liu ti Internet.

(3) PSTN v ISDN cho php chng ta tu chn ISP no m ta mun kt niADSL kt ni chng ta ti mt ISP nh trc.

(4) ISDN chy tc c s 64kbps hoc 128kbps.

ADSL c th ti d liu v vi tc ti 8 Mbps.

(5) PSTN ngt truy nhp ti Internet khi chng ta thc hin cuc gi.

ADSL cho php va s dng Internet trong khi vn c th thc hin cuc gi ng thi.

(6) Kt ni Internet qua ng PSTN v ISDN bng phng thc quay s c tnh cc ni ht.

ADSL khng tnh cc ni ht. Ghi ch:

Mc d modem ADSL lun ch kt ni thng trc, nhng vn c th cn phi thc hin lnh kt ni Internet trn my PC.

Cc dch v nh fax v thoi c th c thc hin cng trn kt ni d liu ADSL ti internet.

Trn thc t, tc download tiu biu i vi dch v ADSL gia nh thng t ti (up to) 400 kbps

Dng bao nhiu, tr by nhiu. Cu trc cc theo lu lng s dng (hoc theo thi gian s dng)

Khng hn ch s ngi s dng khi chia s kt ni Internet trong mng ni b.

2.3.5. Cc thnh phn ca ADSL

Trong phn ny chng ta s ln lt m t chc nng ca tng thnh phn ca ADSL, bt u t Modem ADSL ti Nh cung cp dch v Internet.

Chng ta cng xem xt pha ISP lc ra nhng thnh phn c bn m h s dng cung cp dich v ADSL.

2.3.5.1. Khi nim Modem ADSL?

Modem ADSL kt ni vo ng dy in thoi (cn gi l local loop) v ng dy ny ni ti thit b tng i ni ht.

Modem ADSL s dng kt hp mt lot cc k thut x l tn hiu tin tin nhm t c tc bng thng cn thit trn ng dy in thoi thng thng vi khong cch ti vi km gia thu bao v tng i ni ht.

Cc loi Modem h tr ADSL:

Modem trn card PCI: loi ny tch hp tt c trn mt card PCI. Gi thnh r nht trong ba loi, nhng rt kh ci t, kn chn h iu hnh v khng h tr chia s kt ni n nhiu my tnh. Nu bn tnh dng thm Linux hay Mac OS X, hay chia s k ni ADSL vi nhiu my khc, hay l dn Overclocker, nn trnh xa loi ny.

Modem USB: y l loi modem lp ngoi kt ni qua giao tip USB 1.1. Gi ch hn loi trc mt cht v trng c v d lp t. Nhng thc ra loi ny cng kn h iu hnh khng km loi kia, ci t tng i kh v khng h tr chia s kt ni. Hn na, tc ca USB 1.1 rt thp (ti a l 12 Mbps nhng thc t cn thp hn nhiu), khng thch hp vi ADSL tc cao, li chim nhiu ti nguyn h thng. Bn cn cn nhc k trc khi chn USB cho ADSL.

Ethernet modem lp ngoi: y l loi ph bin nht . N dng giao din ethernet vi my tnh qua card mng 10/100. u im l rt d lp t, h tr hu ht cc h iu hnh, d chai s kt ni. Nhc im ca n l gi thnh cao hn loi khc. Ethernet ADSL modem c khi c tch hp thm mt s chc nng nh tng la (hardware firewall) hay router v hub hay switch lp trong (gip bn chia s kt ni vi cc my khc d dng).

Mt s loi modem ADSL thng dng ti Vit Nam:

DrayTek Vigor318: c kch thc nh gn, c bc bng v nha mu xanh bn trong nn c th nhn thy c cc mch in bn trong. Giao tip bng cng USB. Bo hnh 1 nm, gi 65 USD.

Zoom Modem ADSL 5510: c tch hp sn Splitter v km theo 2 filter, giao tip bng cng USB. Kch thc nh gn, bo hnh 2 nm. gi 95 USB (c VAT).

Zoom ADSL X5 w/4: giao tip qua cng giao tip ngoi bng card mng. Tch hp tng la (firewall) v Splitter. Nh gn, bo hnh 2 nm. Gi 84 USD (bao gm VAT).

2.3.5.2. Modem ADSL lm vic nh th no ?

ADSL hot ng bng cch vn hnh cng lc nhiu modem, trong mi modem s dng phn bng thng ring c th.

S trn y ch m phng mt cch tng i, nhng qua ta c th nhn thy ADSL s dng rt nhiu modem ring l hot ng song song khai thc bng thng ti a v cung cp mt tc rt cao.

Mi ng k sc en trn th hin mt modem v chng hot ng ti cc tn s hon ton khc nhau. Trn thc t c th ti 255 modem hot ng trn mt ng ADSL. im c bit ch ADSL s dng di tn s t 26kHz ti 1.2 MHz trong 10MHz ca bng thng thoi. Tt c 255 modems ny c vn hnh ch trn mt con chp n.

Lng d liu m mi modem c th truyn ti ph thuc vo cc c im ca ng dy ti tn s m modem chim. Mt s modem c th khng lm vic mt cht no v s gy nhiu t ngun tn hiu bn ngoi chng hn nh bi mt ng dy (local loop) khc hoc ngun pht v tuyn no . Cc modem tn s cao hn thng thng li truyn ti c t d liu hn bi l do tn s cng cao th s suy hao cng ln, c bit l trn mt khong cch di.

2.3.5.3. Mch vng / Local Loop l g ?

'Local Loop' l thut ng dng ch cc ng dy in thoi bnh thng ni t v tr ngi s dng ti cng ty in thoi. It is only on the local loop that ADSL communications actually take place.

Nguyn nhn xut hin thut ng local- loop l ngi nghe (in thoi) c kt ni vo hai ng dy m nu nhn t tng i in thoi th chng to ra mt mch vng local loop.

2.3.6. Cc thnh phn ADSL t pha Nh cung cp dch v

By gi chng ta s tm hiu xem cc ISP thc hin cung cp ADSL nh th no.

Phm vi Nh cung cp dch v gm c ba thnh phn quan trng :

DSLAM - DSL Access Multiplexer

BAS - Broadband Access Server

ISP - Internet Service Provider

2.3.6.1. Khi nim DSLAM ?

DSLAM (Digital Subscriber Line Access Multiplexer) - B dn knh truy nhp ng thu bao s - l mt thit b u cui DSL c t ti a im ca nh cung cp dch v mng. DSLAM tp trung lung d liu t cc mch vng DSL v t hp thnh tc cao hn nh tc T1, E1 hoc tc ATM ca OC-3 (155 Mbps)....ri a ti Internet hay mng d liu.

Mt thit b DSLAM c th tp hp nhiu kt ni ADSL- c th nhiu ti hng trm thu bao - v t li trn mt kt ni cp quang. Si cp quang ny thng c ni ti thit b gi l BAS - Broadband Access Server, nhng n cng c th khng ni trc tip ti BAS v BAS c th c ci t bt c u.

DSLAM l thit b t pha tng i, l im cui ca kt ni ADSL. N cha v s cc modem ADSL b tr v mt pha hng ti cc mch vng v pha kia l kt ni cp quang.

2.3.6.2. Khi nim v BAS ?

BAS (Broadband Access Server) l thit b t gia DSLAM v POP ca ISP. Mt thit b BAS c th phc v cho nhiu DSLAM.

Cc giao thc truyn thng c ng gi truyn d liu thng qua kt ni ADSL, v vy mc ch ca BAS l m gi hon tr li cc giao thc trc khi i vo Internet. N cng m bo cho kt ni ca bn ti ISP c chnh xc ging nh khi bn s dng modem quay s hoc ISDN.

Nh ch gii trn, ADSL khng ch r cc giao thc c s dng to thnh kt ni ti Internet. Phng php m PC v Modem s dng bt buc phi ging nh BAS s dng cho kt ni thc hin c.

Thng thng ADSL s dng hai giao thc chnh l:

PPPoE- PPP over Ethernet Protocol

PPPoA- Point to Point Protocol over ATM

2.3.6.3. Khi nim v ISP ?

ISP (Internet Service Provider): l nh cung cp dch v Internet (WWW, email, ftp, telnet...). Vit Nam hin nay c cc nh cung cp dch v Internet nh: VDC, FPT, NetNam...

2.3.7 Cc thnh phn khc ca h thng ADSL

Router/ Bridge ADSL:

Ty thuc vo v tr ca thit b trong h thng m ta la chn ch hot ng ca thit b l Router hay Bridge. Bridge ADSL phi c cu hnh mnh lm nhim v chuyn ti d liu vi tc cao (1 Mbps chiu Upload, 8 mbps chiu Download) v khong cch chp nhn c (4(5).

-Mt s loi Router ph bin Vit Nam hin nay:

Ccom EGA- 100U: tch hp tng la; tch hp my ch DHCP; h tr NAT, my ch o, DMZ; khng c cng tc m, c nt Reset; 1 cng 10/100 Mbps, 1 cng USB. Gi 79 USD, bo hnh 1 nm.

Planet ADE-3000: tch hp my ch DHCP; h tr NAT, my ch o, DMZ; khng c cng tc m, c nt Reset; 1 cng 10/100 Mbps, 1 cng USB.Loi ny c phn mm km LANGuard, mt dng phn mm tng la. Gi 65 USD, bo hnh 2 nm.

Zoom X3/X4: c tch hp sn Splitter v km theo 2 filter , tch hp my ch DHCP; h tr NAT, my ch o, DMZ; cng tc tt m, c nt Reset; 1 cng 10/100 Mbpc, 1 cng USB. C kch thc nh gn nht trong cc loi. Bo hnh 2 nm, Zoom X3 c gi 135 USD (VAT), X4 c gi 145 USD (VAT).

2.3.8. Kt ni mng

Di y s trnh by v nhng giao thc truyn thng c s dng trn kt ni ADSL.

Khi kt ni vo Internet, bn s dng cc giao thc chy tng vn chuyn TCP/IP (chng hn nh HTTP- giao thc c s dng bi cc web- browser). Qu trnh ny l ging nhau vi cc kiu truy nhp quay s qua PSTN, ISDN v ADSL.

2.3.8.1. Cc giao thc c s dng gia Modem v BAS

Khi quay s PSTN/ISDN truy nhp Internet, chng ta s dng giao thc gi l PPP vn chuyn d liu TCP/IP v kim tra cng nh xc thc tn v mt khu ngi truy nhp.

Trong ADSL, PPP cng thng c s dng kim tra tn v mt khu truy nhp v ATM th lun c s dng mc thp nht. Kt ni in hnh nh di y:

2.3.8.2. Vai tr ca ATM

ATM- Asynchrononus Transfer Mode- c s dng nh l cng c chuyn ti cho ADSL mc thp. L do v l cch thun tin v mm do i vi cc cng ty thoi mun ko di khong cch kt ni t DSLAM ti BAS gip h c th t BAS bt c u trn mng.

Cc tham s thit lp cu hnh ATM

C hai tham s cn phi thit lp cu hnh mt cch chnh xc trn Modem ADSL m bo kt ni thnh cng ti mc ATM vi DSLAM:

VPI - the Virtual Path Identifier

VCI - the Virtual Channel Identifier

2.3.9. Vai tr ca PPP

PPP l giao thc dng vn chuyn lu lng Internet ti cc ISP dc theo cc kt ni Modem v ISDN. PPP kt hp cht ch cc yu t xc thc kim tra tn/ mt khu - v l l do chnh m ngi ta dng PPP vi ADSL.

Mc d BAS thc thi giao thc PPP v tin hnh vic xc thc, nhng thc ra vic c thc hin bng cch truy nho vo cc c s d liu khch hng t ti ISP. Bng cch , ISP bit c rng cc kt ni do BAS nh chuyn ti c xc thc thng qua giao dch vi c s d liu ring ca ISP.

2.3.10. Modem ADSL trn thc t

Modem ADSL thng minh bn thn n tch hp sn cc giao thc truyn thng cn thit (nh thit b modem ADSL Router hoc modem c s dng kt ni qua cng Card Ethernet 10/100 Mb) nn ch vic la chn v khai bo VPI/VCI cho modem.

Cn modem ADSL th ng th phi hot ng da trn h iu hnh ca my tnh cung cp cc giao thc cn thit. Cc li modem ny bt buc phi ci t phn mm iu khin modem v thit lp cc giao thc PPP, VPI/VCI. Vic cu hnh nh vy phc tp v i hi thi gian nhiu hn.

Ch c Windows 98SE, Windows Me, v Windows 2000/XP l c ci sn c ch thc thi ATM, v th ngi ta t s dng cc modem th ng trn thc t. Mc d cc modem thng minh c h tr cc giao thc cn thit nhng chng vn c th c dng cho cc h iu hnh ni trn.

Cc modem th ng c th ni vi PC thng qua giao din USB, hoc c th c sn xut di dng PCI card cm thng trn bng mch ch ca PC.

Lu l vic khai thc giao thc ATM khng c ngha l cn phi c card mng ATM cho PC - ch l c ch h tr bng phn mm trong h iu hnh.

2.3.11. Mi tng quan gia thoi v ADSL

ADSL cho php cng lc va truy nhp Internet tc cao li va c th thc hin cuc gi cng trn ng dy .

Thit b chuyn dng Splitters c s dng tch ring cc tn s cao dng cho ADSL v cc tn s thp dng cho thoi. Nh vy, ngi ta thng t cc Splitters ti mi u ca ng dy - pha thu bao v pha DSLAM.

2.3.11.1. Thoi v ADSL chung sng ra sao?

Ti pha thu bao, cc tn s thp c chuyn n my in thoi cn cc tn s cao i n modem ADSL. Ti cc tng i, cc tn s thp c chuyn sang mng thoi PSTN cn cc tn s cao i n ISP.

2.3.11.2. Tc a dng

Tc ca kt ni gia modem ADSL v DSLAM ph thuc vo khong cch ng truyn v tc ti a c cu hnh sn trn cng ca DSLAM. Cn tc kt ni vo Internet li cn ph thuc vo nhiu yu t khc na nh di y:

S ngi dng kt ni vo cng mt DSLAM v thc t c bao nhiu ngi dng ang khai thc kt ni.

Tc kt ni gia DSLAM v BAS

Bao nhiu card DSLAM cng ni vo mt BAS v bao nhiu ngi dng ang khai thc thc t kt ni.

Tc kt ni gia BAS kt ni vo ISP v bao nhiu ngi dng thc t ang khai thc.

Tc ca kt ni t ISP ti mng Internet ton cu.

Bao nhiu thu bao ca ISP ang khai thc (qua cc giao tip khc nhau nh quay s PSTN/ ISDN v ADSL).

ISP t chc caching v proxy ra sao, liu thng tin m bn cn khai thc c lu tr trn Cache cha hay phi ti v t Internet.

2.4. ADSL mang li g cho ngi dng, doanh nghip v cc t chc:

2.4.1. i vi ngi dng

V c bn, ADSL s gip bn lm nhng vic quen thuc trn Internet nh dng th in t, duyt Web, duyt din n, ti file....nhng nhanh hn trc rt nhiu ln v bn c th lm nhng vic ng hi thay v phi lm ln lt tng th nh trc y. Bn c th thoi mi duyt internet do khng phi di c i modem quay s gi tng i hay ngi c truyn chng ch Web np xong trn trnh duyt. Mt iu ng ch l bn khng phi tr cc gi in thoi khi dng ADSL, v ng dy vn dng gi c khi ang duyt Internet, cho d cng ngh ny da trn ng dy in thoi c sn.

Ngoi vic tng tc cho nhng nhu cu Internet ph bin trn, ADSL cn gip bn s dng Internet vo nhng tc v m trc y modem quay s vn phi khc lc thm thit vy c trng u hng:

Th nht, bn c th truy cp nhng website thit k vi cht lng cao, dng flash, nhc nn, nhiu nh ng....

Th hai, bn c th nghe v xem cc bi ht, bn tin, gii thiu phim..t khp mi ni trn th gii.

Th ba, phim theo yu cu (movie- on- demand). Hin nay trn th gii c nh cung cp SingNet (Singapore) ang cung cp dch v ny vi gi 6,5 USD/ thng qua ng ADSL 512 Kbps.

Th t, hi tho video qua mng: kt hp vi webcam, ADSL s gip bn m o vi bn b, ngi thn hay i tc kinh doanh qua internet vi m thanh hnh nh cht lng cao.

Th nm, chi multiplayer game trn internet vi bn b khp th gii. ADSl cho php cc game mng chy trn chu, do thi gian ping thp.

Th su, hc qua mng, bn c th tham d cc kha hc t xa t chc bi cc trng i hc trn th gii hoc truy cp cc th vin in t trn mng nhanh hn.

2.4.2. i vi doanh nghip v cc t chc x hi

Thng mi in t v nn cng nghip thng tin l nn tng tng lai ca mi nn kinh t. ADSL ni ring v Broadband Internet ni chung khin thng mi in t tr nn kh thi. Cc ca hng trn mng c th c thit k vi tnh tng tc cao hn, cch trnh by hp dn hn vi ngi dng. Loi ca hng ny s gip cc doanh nghip nh c th cnh tranh vi cc c s ln hn trn quy m ton cu.

Nn cng ngh phn mm ca Vit Nam s t tnh cnh tranh cao hn so vi Internet bng thng dng. Vic pht trin, thm d v xm nhp th trng cng nh nhn n t hng v giao sn phm s tr nn d dng hn v kinh t hn.

Chng 3 Kt lun.

ADSL l cng ngh mang tnh t ph trong ngnh cng ngh thng tin. Nh c cng ngh ADSL m con ngi c th thc hin nhng iu cc cng ngh mng trc y tng nh khng th thc hin c nh: hi tho Vidio qua mng, phim theo yu cu, chi Game trc tuyn... Hin nay cng ngh ADSL v nhng h cng ngh xDSL khc c s dng rng ri ti cc nc pht trin.

T nhng u im vt tri ca cng ngh ADSL, chc chn cng ngh ADSL s c ng dng v pht trin rng ri ti Vit Nam.

Trong qu trnh tm hiu v ADSL, em nhn c s gip tn tnh ca Trung tm Vin thng Chi Lng v c gio Th.s Dng Thanh T gip em hon thnh tt bo co thc tp tt nghip ny. V thi gian lm v kin thc c hn nn bo co khng trnh khi nhng sai st, rt mong s gp ca c gio v cc bn.

Xin chn thnh cm!

Sinh vin Khng Vn Mnh XC NHN CA N V THC TP

POTS

UPSTREAM

DOWSTREAM

0-25

khz

25- 200

khz

250- 1000

khz

hnh 2.1 di ph tn ca ADSL

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