Bai Giang Chuong 1 Tong Quan He Thongtruyen Dan

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  • 1Bi ging

    K thuttruyn dn 1

    Ging vin: ThS. Phan Thanh Hin

  • 2Vai tr - V tr mn hc1. Vai tr:

    1. Cung cp kin thc tng quan v h thng truyn dns

    2. Cc thng s c bn trong knh truyn dn s.3. Cc k thut truyn dn s in hnh ( PDH, SDH,)4. Cc m hnh qun l mng truyn dn.

    2. V tr mn hc:1. Cc mn hc tin quyt: C s thng tin s; L thuyt

    thng tin; K thut mch in t2. Cc mn hc song hnh: Thng tin vi ba s, Mng my

    tnh; K thut truyn hnh

  • 3Hnh thc hc nh gi1. Yu cu: i hc y ( khng ngh qu s tit quy nh) Chun b bi trc khi n lp. Chun b gio trnh v ti liu tham kho

    2. nh gi:1. Kim tra gia k: Thi vit2. Thi kt thc hc phn: Thi vit3. im chuyn cn: Sinh vin c th ng k lm tiu

    lun,

  • 4Ti liu hc tpSch, gio trnh chnh: [1]; Nguyn Quc Bnh; K thut truyn dn s; NXB

    Qun i nhn dn; 2001. [2]; Chu Cng Cn; K thut truyn dn SDH; NXB Giao

    thng vn ti; 2003. [3]; Nguyn Hng Sn; K thut truyn s liu; NXB Lao

    ng - X hi; 2002. Sile bi ging, ti liu km theo. - Sch tham kho: [4]; Nguyn Thc Hi; Mng my tnh v cc h thng

    m; NXB Gio dc; 1997.

  • 5Ni dung mn hc Chng 1: Tng quan v h thng truyn dn Chng 2: S ho tn hiu lin tc trong cc h thng

    truyn dn s.

    Chng 3: Ghp knh trong truyn dn tn hiu s Chng 4: X l tn hiu bng gc Chng 5: K thut truyn dn PDH Chng 6: K thut truyn dn SDH Chng 7: ng b trong truyn dn s

  • 6CHNG 1

    TNG QUAN V H THNG TRUYN DN

  • 7Ni dung chnh

    1. Cc c im ca h thng thng tin s

    2. Trnh by mt s khi nim v thut ng

    3. S khi h thng thng tin s c bn

    4. Cc tham s cht lng c bn ca h thng thng tin s

    5. H thng truyn dn s

    6. Dch v mng vin thng v mi trng truyn

  • 81. Cc c im h thng thng tin s

    Cc h thng thng tin s c dng truyn tin tc tni ny n ni khc.

    Bn tin l dng hnh thc cha ng thng tin ( C thlin tc hay ri rc)

    Biu din vt l ca mt bn tin c gi l tn hiu. Tn hiu truyn dn c th l: Tn hiu Analog Tn hiu s

  • 92. MT S KHI NIM V THUT NG

    Tm lc mt s kin thc c bn :Khi nim v thut ngTn hiu v nhiu

  • 10

    Tn hiu

  • 11

    Tn hiu

  • 12

    T

    A

    Tn s ca tn hiuMin thi gian Min tn s

    A

    T

    T

    A

    1 giy (s)

    f

    A

    A

    A

    0

    f

    2f

    F

    F

    F

  • 13

    Ph ca tn hiu

    f = 300 Hz 300F (Hz)

    600 Hz 600F (Hz)

    700 Hz 700F (Hz)

    F (Hz)

    Ph: Tm tn s cha trong tn hiu

  • 14

    Bng thngA

    F500 2500

    Bng thng tuyt i rng ph (c o bng s chnh lch tn s cao nht v thp nht

    m knh h tr) Bng thng cng ln, tc truyn cng cao

    Bng thng hiu dng Bng thng Di tm tn s hp cha hu ht nng lng ca t/h

    Bandwidth = 2500 500 = 2000 Hz

  • 15

    Ph m ca thoi

  • 16

    Nhiu Tn hiu thm vo gia thit b pht v thit b thu Cc loi nhiu Nhiu nhit Nhiu iu ch Nhiu xuyn knh (cross talk) Nhiu xung

  • 17

    Nhiu

  • 18

    Nhiu nhit Do dao ng nhit ca cc in t trong cht dn Hm ca nhit

    Phn tn ng nht trn ph tn s Nhiu trng Khng th loi b gii hn hiu sut ca h thng Nhiu trong bng thng 1Hz ca bt k cht dn no

    N0 = kT N0: mt cng sut nhiu (watt/Hz) k: hng s Boltzmann (= 1.38 x 10-23 J/0K) T: nhit (0K)

    Nhiu trong bng thng W Hz: N = N0W = kTW

  • 19

    Nhiu Nhiu iu ch

    T/h nhiu c tn s l tng hoc hiu tn s ca cc t/h dng chungmi trng truyn

    Do tnh phi tuyn ca thit b thu/pht Nhiu xuyn knh (crosstalk)

    T/h t ng truyn ny nh hng sang cc ng truyn khc Cng ln (hoc nh hn) nhiu nhit

    Nhiu xung Xung bt thng (spike)

    e.g. nh hng in t bn ngoi Thi khong ngn Cng cao nh hng nhiu n qu trnh trao i d liu s

    Xung 0.01s lm mt 50 bit d liu nu truyn tc 4800bps

  • 20

    Tc knh truyn (kh nng knh) c im C th truyn nhiu hn mt bit ng vi mi thay i ca

    tn hiu trn ng truyn. Tc truyn thng tin cc i b gii hn bi bng thng

    ca knh truyn Cng thc Nyquist Nu tc truyn tn hiu l 2W th tn hiu vi tn s nh

    hn (hoc bng) W l ; ngc li nu bng thng l W th tc tn hiu cao nht l 2W

    C = 2W x log2M C : tc truyn t/h cc i (bps) khi knh truyn khng c

    nhiu W : bng thng ca knh truyn (Hz) M : s mc thay i tn hiu trn ng truyn

    hu hiu bng thng: B = R/W (bps HZ-1)

  • 21

    Tc knh truyn

  • 22

    Tc knh truyn

  • 23

    Tc d liu Baud rate (baud/s)

    Nghch o ca phn t d liu ngn nht (s ln thay i tn hiung truyn mi giy)

    Tn hiu nh phn tc 20Hz: 20 baud (20 thay i mi giy) Bit rate (bps hoc bit/s)

    c trng cho kh nng ca knh truyn Tc truyn d liu cc i trong trng hp khng c nhiu Bng baud rate trong trng hp tn hiu nh phn Khi mi thay i ng truyn c biu din bng 2 hay nhiu bit,

    tc bit khc vi tc baud Quan h gia Baud rate v Bit rate

    R = Rs x log2M = Rs x m R : tc bit (bit/s) Rs : tc baud (baud/s) M : s mc thay i tn hiu trn ng truyn m : s bit m ha cho mt tn hiu

  • 24

    Bit rate

  • 25

    T l tn hiu so vi nhiu Signal to Noise ratio

    SNR = 10 x log10 (S/N) (dB) S : cng sut tn hiu nhn N : cng sut nhiu

    Cng thc Shannon-HartleyC = W x log2 (1 + S/N) (bps)

    C: tc truyn t/h cc i khi knh truyn khng c nhiu

  • 26

    Chiu di sng Khong cch chim bi mt chu k Khong cch gia 2 im pha tng ng trong 2 chu k

    lin tip K hiu Gi s vn tc t/h l v = vT f = v c = 3*108 ms-1 (tc nh sng)

  • 27

    3. S khi h thng thng tin s

    To khun

    To khun

    M ho ngun

    Gii m ngun

    M ho mt

    Gii m mt

    M ho khnh

    Gii m khnh

    iu ch

    Phn khnh

    Ghp khnh

    Gii iu ch

    Tri ph

    Gii tri ph

    a truy nhp

    a truy nhp

    My pht

    My thu

    Knh truyn

    ng b

    T cc ngun khc

    Ti cc ch khc

    T ngun tin

    Ti b nhn tin

    * * * * *

    * * * * *

    * : Chui bt

    # # #

    ###

    #: Chui dng sng

    y l s h thng thng tin s in hnh song khng phi nht thit hthng no cng phi thc hin y cc thut ton c bn ny.

  • 28

    Chc nng cc khi trong s

    To khun dng tn hiu: thc hin bin i tn tc cntruyn th hin dng tn hiu lin tc hay s thnh ccchui bit nh phn.

    M ho v gii m ngun tn hiu: thc hin nn v giinn tn hiu nhm gim tc bit gim ph tn hiu.

    M mt: thc hin m chui bit theo 1 kho xc nhnhm bo mt tin tc.

    M knh: chng nhiu v cc tc ng xu khc trnng truyn.

  • 29

    Chc nng cc khi trong s Ghp, tch knh: thc hin truyn tin t nhiu ngun tin

    khc nhau ti cc ch nhn tin khc nhau trn 1 h thngtruyn dn.

    iu ch (MODEM) l bin i tn hiu t bng tn c ssang tn hiu thch hp vi ng truyn dn.

    Tri ph: nhm mc ch chng nhiu v bo mt tin tc. a truy nhp: cho php nhiu i tng c th truy nhp

    mng thng tin s dng h thng truyn dn theo yucu.

    ng b mng: bao gm ng b nhp v dng b sngmang

  • 30

    4. Cc tham s c trng trong truyn dn

    1. Cng sut pht.

    2. Di tn knh.

    3. T s S/N.

    4. Suy hao.

    5. Mo tr nhm.

    6. BER.

  • 31

    4.1 Cng sut pht

    Cng sut pht: Ph thuc hon ton vo my pht. Cng sut pht ln th khong cch truyn dn tt hn, xa

    hn. Tu thuc vo knh truyn dn m cng sut pht ca

    my pht c th thay i m bo vic truyn dn vkhng tc ng ln cc h thng xung quanh.

  • 32

    4.2. Di tn hay Bng thngA

    F

    Bng thng tuyt i rng ph (c o bng s chnh lch tn s cao nht v thp nht

    m knh h tr) Bng thng cng ln, tc truyn cng cao

    Bng thng hiu dng Bng thng Di tm tn s hp cha hu ht nng lng ca t/h

    500 2500

    Bandwidth = 2500 500 = 2000 Hz

  • 33

    4.3. T s tn hiu/ nhiu (S/N)

    T s tn hiu/nhiu (S/N): c trng cho mi trngtruyn dn.

    T s S/N cao tng ng vi knh truyn tt, nnh cao, khng b tc ng nhiu ca nhiu. Ngc linu t s S/N thp th knh truyn ny b tc ng rtnhiu ca nhiu.

    i vi knh truyn c t s S/N thp th bt buc phi sdng m ho, tri ph nhm chng nhiu.

  • 34

    4.4. Suy hao hay Suy gim tn hiu

    T/h nhn c khc vi t/h truyn i Analog suy gim cht lng t/h Digital li trn bit

    Nguyn nhn Suy yu v mo do suy yu trn ng truyn Mo do tr truyn Nhiu

  • 35

    suy gim tn hiu nh ngha (signal attenuation)

    Khi mt tn hiu lan truyn qua mt mi trng truyn, cng (bin ) ca tn hiu b suy gim (theo khong cch)

    Ty thuc vo mi trng truyn dn i vi mi trng v tuyn, suy gim cng t/h l mt hm phc

    tp theo khong cch v thnh phn kh quyn Cng t/h nhn phi

    mnh thit b nhn nhn bit c cao so vi nhiu t/h khng b li Suy yu l mt hm tng theo tn s K thut cn bng suy yu trn di tn s Dng b khuych ai (khuych i tn s cao nhiu hn)

    o bng n v decibel (dB) Cng t/h suy gim theo hm logarit li/ hao ht ca cc tng ni tip c th c tnh bng php

    ton n gin (+/-)

  • 36

    suy gim tn hiu o bng n v decibel (dB) Cng t/h suy gim theo hm logarit li/ hao ht ca cc tng ni tip c th c tnh

    bng php ton n gin (+/-) Cng thc Attenuation = 10log10(P1/P2) (dB)

    P1: cng sut ca tn hiu nhn (W) P2: cng sut ca tn hiu truyn (W)

    Decibel (dB) l gi tr sai bit tng i Cng sut suy gim hao ht l 3dB Cng sut tng gp i li l 3dB

  • 37

    4.5. Tr lan truyn tn hiu Mo tr truyn

    Ch xy ra trong mi trng truyn dn hu tuyn Vn tc lan truyn thay i theo tn s

    Vn tc cao nht gn tn s trung tm Cc thnh phn tn s khc nhau s n ch cc thi im khc

    nhau Cng thc

    Transmission propagation delayTp = S/V

    S : khong cch vt l (meter) V : vn tc lan truyn tn hiu trn mi trng truyn, vd: vi

    sng in t: v = 2 x 106 (m/s)

    Round trip delay Tx = N/R

    N : khi lng d liu truyn (bit) R : tc truyn bit trn ng truyn.

  • 38

    Tham s cht lng c bn ca HTTTS

    Yu cu ca h thng thng tin s: tin cy cao v tc truyn nhanh.

    i vi thng tin: Tham s chnh nh gi cht lng hthng nh gi qua t l li bit (BER: Bit Error Ratio).

    BER: L t l gia s bit nhn b li v tng s