Gks Tinchi Ch2 Pcm Va Pdh

8/14/2019 Gks Tinchi Ch2 Pcm Va Pdh

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TS.V Trng Sn Bi ging K thut ghp knh s 1

CHNG 2

K thut ghp knh s

PCM v PDH


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Ni dung chng 2

6Ghp knh PDH2.2

2Ghp knh PCM2.1


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Nguyn l TDM


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Nguyn l TDM


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Nguyn l TDM


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Nguyn l TDM


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H thng PCM & TDM Vi cc knh 64 kbit/s t cc tng i s, c 3 phng php

ghp knh: PDH(plesiochronous digital hierarchy) (50-60,G.702)

SONET (synchronous optical network) (85)

SDH (synchronous digital hierarchy) (CCITT 88)

European PCM frame

32 time slots x 8 bits x 8000 Hz = 32 x 64 kbit/s = 2048 kbit/sframe synchronization slot

signaling or traffic

traffic

125 s

PDH E-1 frame


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S khi PCM:u ghp (u pht)


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S khi PCM:u tch (u thu)


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Cu trc khung lung E1


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ITU-T Rec. G.704

E1 CAS Transmission Format

Fr. Ch. Ch.

1 1 16

2 2 173 3 18: : :

15 15 30

10 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Multiframe (16 frames)

Frame 0 (32 Time Slots)

10 2 3 4 5 6 7 8 9101112131415 1716 1819202122232425262728293031

Frame 1 (32 Time Slots)

10 2 3 4 5 6 7 8 9101112131415 1716 1819202122232425262728293031

Time Slot 0(8 bits)

0X 0 1 1 0 1 110

10

10

10

10

10

10

10

Time Slot 1Speech (Ch. 1)

Time Slot 16(8 bits)

00 0 0 X 0 X X

Time Slot 0(8 bits)

1X 0 X X X X X

Time Slot 16Signalling Bits

10

10

10

10

10

10

10

10

SpeechCh. 1-15

SpeechCh. 16-30

SpeechCh. 1-15

SpeechCh. 16-30

Frame

Time Slot

FrameAlignment

Word

Multi-

FrameAlignmentWord

Changes to 1 on

loss of distantmultiframe

Changes to 1 on

loss of distant frame(remote alarm)

Not-Framealignment word

A B CD A B CD

LSB

Khi truyn tn hiu s liu 64 Kbit/s, v khng c tn hiu bo hiu i

km nn TS16 c dng cho knh s liu th 31


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.

.

.

3

21

0

TS16 bit s1 2 3 4 5 6 7 8

TS0 bit s1 2 3 4 5 6 7 8

KhungS

Cc khe thi gian 0 v 16 tronga khung


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SIG - Ch7 SIG - Ch22Y 1 Z X X X X X7

SIG - Ch6 SIG - Ch21Y 0 0 1 1 0 1 16


SIG - Ch4 SIG - Ch19Y 0 0 1 1 0 1 14


SIG - Ch2 SIG - Ch17Y 0 0 1 1 0 1 12


0 0 0 0 X Z X XY 0 0 1 1 0 1 10

TS16 bit s

1 2 3 4 5 6 7 8

TS0 bit s

1 2 3 4 5 6 7 8

Khung

S

Cc khe thi gian 0 v 16


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ng b trong ghp knh c s

C 3 cp ng b trong ghp knh c s: ng b bit (ng b ng h)

ng b khung, v

ng b a khung.

ng b bit c thc hin nh vo m ng truyn

v khi phc ng h ti u thu.


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Qu trnh ng b khung

CC TRNG THI NG B KHUNGFAC : ng b khung ng

FAE : ng b khung sai

N : trng thi bnh thng

FA : trng thi cnh bo

F1,F2,F3: trng thi tin cnh boA1,A2 : trng thi tin ng b


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Cnh bo mt ng b


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ng b a khung

ng b a khung thc hin sau khi t c ng bkhung: Tm khe thi gian 16

Kim tra 4 bit u xem c gi tr l 0000

Nu ng, khung ang c l khung 0 v t c ng b a khung Nu sai, nhy mt khung v tip tc xem xt khe thi gian 16.

(Cc nhm 4 bit bo hiu ca cc knh khng bao gi c dng0000)


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Cu trc khung PCM24


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So snh PCM24 & PCM30/32

T m ng b a khung

T m ng b khung

Tn hiu ng b a khungtrong

Tn hiu ng b khung trong

Chu k mt a khung(ms)

S khung trong mt a khung

S bit trong 1 t mChu k mt khung(s)

Tc bit(Mbps)

rng bit(s)

rng khe thi gian(s)

Tn s ly mu(kHz)

PCM30/32PCM24


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So snh PCM24 & PCM30/32

0000001110T m ng b a khung

0011011101010T m ng b khung

khung 0cc khung chnTn hiu ng b a khungtrong

cc khung chncc khung lTn hiu ng b khung trong

21,5Chu k mt a khung(ms)

1612S khung trong mt a khung

88S bit trong 1 t m125125Chu k mt khung(s)

2,0481,544Tc bit(Mbps)

0,490,65 rng bit(s)3,95,2 rng khe thi gian(s)

88Tn s ly mu(kHz)

PCM30/32PCM24


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Tng kt T1 v E1 Trong PSTN, hai h thng PCM c s dng rng ri l:

T1, Bell Laboratories pht trin, s dng USA, Nht E1, CEPT pht trin, s dng rng ri cc quc gia khc.

C hai lung E1&T1 u c tc khung 8000 frames/s

lung T1 24 Ts v 1 bit ng b phc v 24 knh

di khung: 1+ 8x24=193 bits

Tc : 193x8000 bits/second=1544 kb/s

lung E1 Khung c 32 Ts, TS0 dng cho ng b v TS 16 dng cho thng tin bo

hiu.

Mt khung E1 c 32x8=256 bits v tc l 8000x256=2048 kb/s


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Ni dung chng 2

6Ghp knh PDH2.2

2Ghp knh PCM2.1


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Phn cp ghp knh PDH


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Cc cp ghp theo chun Bc M

274,1764032DS4

Lng cc( B6ZS)44,736672DS3

Lng cc( B6ZS)6.31296DS2

Lng cc1.54424DS1

M ng truynTc bit

( Mbps)

S KnhMc


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Nguyn l ghp lung th cp


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S khng ng b ng h


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ng b ng h & trt bit Cc lung s n khng hon ton ng b vi nhau

Xut hin hin tng trt bit ti khi ghp knh


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K thut chn

C 2 k thut chn c bn: Chn dng:

Chn m:


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K thut chn

Chn dng: (S dng rng ri) chn thm xung cho lung n chm so vi ng h ghp knh.

trong tng khung cp cao dnh cho mi lung cp thp mt v tr gil bit chn.

Bnh thng, bit ny mang thng tin, nu lung cp thp n chm, mt bit trng c chn vo v tr ny.


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K thut chn dng

Chn: s ng b nhm chng li vic mt s liu do trt.

Tc ra R > R1+R2 i.e. E2, 8.448Mbps = 4x2.048Mbps + 256 Kbps

Bit chn v ch th chn Vi cc khung bc cao, mi mt lung bc thp c php chn hoc

khng chn 1 bit n vo mi khung bc cao (bit chn).

Cn ch r c chn hay khng u phn knh nhn bit.

Cn mt s bit lm cng vic ny (cc bit ch th chn).


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K thut chn dng


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Cu trc khung E2 (8Mbps)


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Chn trong lung E2

V d 1: Trong khi ghp 4 lung E1 (A, B, C, D) thnh 1 lung E2, gi strong khung th k, cc lung A v D khng chn, cc lung B v C cchn.

Xc nh trng thi cc bt S v C?

Gii: S1: C11: C12: C13:

S2: C21: C22: C23:

S3: C31: C32: C33:

S4: C41: C42: C43:


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Chn trong lung E2

V d 2: Trong khi phn knh 1 lung E2 thnh 4 lung E1(A, B, C, D), gi s trong khung th k, ta nhn c ccnhm bt ch th chn tng ng theo th t nh sau: Cj1=(1100);

Cj2=(1010);

Cj3=(1100)

Xc nh trng thi cc bt S v cho bit bit S no c ly

cho lung E1, bit no b lai b?


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Vd2

Gii: C11: 1 C12: 1 C13: 1 S1: S (loi)

C21: 1 C22:0 C23: 1 S2: S (loi)

C31: 0 C32:1 C33: 0 S3: I (ly cho C)

C41: 0 C42:0 C43: 0 S4: I (ly cho D)


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637 640641 644

645 - 848

44

204

Bit ch th chnBit chn

Data

4

425 428

429 636

4

208

Bit ch th chn

Data3

213 216217 424

4208

Bit ch th chnData2

1 10

11 12

13 212

10

2

200

FAW:1111010000

Bit nghip v

Data

1

Th t ca bitS lng bitLoi tn hiuon



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CC LUNG E3, E4, E5

Cc cu hi cn tr li cho mi lung: Lung c ghp t cc lung no? My lung?

Tc bt l bao nhiu?

Tng ng bao nhiu knh thoi?

Thi gian v s lng bt / 1 khung? im khc bit c bn ca lung bc cao hn so vi cc lung bc

thp hn l g?

S lng bt ch th chn cho mi lung bc thp ghp ln?

Ti sao phi phn tn cc bt ch th chn? Ti sao mi khung phi chia thnh nhiu on?

Mi lung bc thp c bao nhiu bit trong mi khung bc cao trongtrng hp chn v khng chn?


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1153 1156

1157 1160

1161 - 1536

4

4

376

Bit ch th chn

Bit chn

Data

4

769 772

773 1152

4

380

Bit ch th chn

Data3

385 388

389 768

4

380

Bit ch th chn

Data2

1 10

11 12

13 384

10

2

372

FAW:1111010000

Bit nghip v

Data

1




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977 980

981 1464

4

484

Bit ch th chn

Data

3

1465 1468

1469 1952

4

484

Bit ch th chn

Data

4

2441 2444

2445 2448

2449 - 2928

4

4

480

Bit ch th chn

Bit chn

Data

6

1953 1956

1957 - 2440

4

484

Bit ch th chn

Data

5

489 492

493 976

4

484

Bit ch th chn

Data

2

1 12

13 16

17 488

12

4

472

FAW:111110100000

Bit nghip v

Data

1




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Khung E5 ch c trong phng th nghim, khng tn ti trong thc t.


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Xen r mc cc knh Analog Bin i D/A tt c cc knh, sau bin i A/D tr

li cc knh i thng.

K thut ny c mt s nhc im sau :- Mo ti cc b D/A & A/D c tch ly.- Chi ph cao - Tng mc tp m

Site BDrop/Insert

Site CDrop/Insert

Site DDrop/Insert

Site AChannel Bank

Site EChannel

Bank

Drop/Insert

analog channels

D/A A/D

Drop/Insert

analog channels

D/A A/D

Drop/Insert

analog channels

D/A A/D

E1 E1E1 E1

K thut xen /r (Insert/Drop)


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BDrop/Insert

CDrop/Insert

DDrop/Insert

AChannel Bank

EChannel Bank

Drop/Insertchannels

Drop/Insertchannels

Drop/Insertchannels

Drop Insert Pass through

K thut xen /r (Insert/Drop)

Ch bin i D/A cc knh xen r, cc knh i thng vn dng Digital.


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Ghp knh tng cp trong PDH Trong PDH, khi ghp knh t E1 ln E4 cn c 21 b ghp

knh: 16 x 2DME, 4 x 3DME, 1 x 4DME

Cn nhiu on cp ni gia cc DME


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Xen r lung E1 t lung E4

4DME

4DME

2DME

2DME

3DME

3DME

140Mbps 140Mbps34 Mbps 34 Mbps

34 Mbps 34 Mbps

2 Mbps

Gks Tinchi Ch2 Pcm Va Pdh

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