time division multiplexing - nouvelle page 1
TRANSCRIPT
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Claude Rigault, ENST 04/10/2004
Communication networks 03 1
Time Division Multiplexing
Claude RigaultENST
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Claude Rigault, ENST 04/10/2004
Communication networks 03 2
Time division multiplexing
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Claude Rigault, ENST 04/10/2004
Communication networks 03 3
Time Division multiplexing (1)
Time division multiplexing
• Time Slot 1
Multiplexer De-multiplexer
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Claude Rigault, ENST 04/10/2004
Communication networks 03 4
Time Division multiplexing (2)
Time division multiplexing
• Time Slot 2
Multiplexer De-multiplexer
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Claude Rigault, ENST 04/10/2004
Communication networks 03 5
Time Division multiplexing (3)
Time division multiplexing
• Time Slot 3
Multiplexer De-multiplexer
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Claude Rigault, ENST 04/10/2004
Communication networks 03 6
Time Division multiplexing (4)
Time division multiplexing
• Time Slot 4
Multiplexer De-multiplexer
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Claude Rigault, ENST 04/10/2004
Communication networks 03 7
Frames
Time division multiplexing
• Each rotation corresponds to a frame on the multiplex
TS0TS1TS2TS3Multiplexer De-multiplexer
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Claude Rigault, ENST 04/10/2004
Communication networks 03 8
• Time division multiplexing is based on peak rate• TDM is adapted to constant rate sources (like voice)
maxdCnt =
Time Division multiplexing
trunks
Switchingnetwork Trunk circuits
J
J
J
J
J
J
J
J
SwitchingnetworkTrunk circuits
Time division multiplexing
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Claude Rigault, ENST 04/10/2004
Communication networks 03 9
Sampling an analog signal
• Time division multiplexing requires that only samples of the signal are transmitted. If we have fs rotations /second, the sampling frequency is fs
Time division multiplexing
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Claude Rigault, ENST 04/10/2004
Communication networks 03 10
Effect of sampling
Fs 2Fs
Energy
FrequencyFs-FmaxFmax
To recover the original signal, there should be no overlapping :
fs- fmax> fmaxor : fs> 2fmax
Time division multiplexing
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Claude Rigault, ENST 04/10/2004
Communication networks 03 11
PAM modulation
Time division multiplexing
Fmax
Fs > 2 Fmax
Fs
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Claude Rigault, ENST 04/10/2004
Communication networks 03 12
Voice spectrum
Frequency (Hz)
Energy
Cut off frequency of filter is at 4000 Hz ⇒ fs = 8000 Hz
Time division multiplexing
300 3400
4000filter
800
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Claude Rigault, ENST 04/10/2004
Communication networks 03 13
PAM and Time division multiplexing
Time division multiplexing
• 8000 rotations / second• Advantage of TDM : the filter is the same everywhere• Disadvantage of PAM : analog system ⇒ noise sensitivity
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Claude Rigault, ENST 04/10/2004
Communication networks 03 14
PCM and Time division multiplexing
Time division multiplexing
CODERPAM PAM
DECODER
PCM link
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Claude Rigault, ENST 04/10/2004
Communication networks 03 15
Voice signal dynamics
• The dynamics of the voice signal is very large ⇒ quantization noise gets very large on small signals
Time division multiplexing
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Claude Rigault, ENST 04/10/2004
Communication networks 03 16
Quantization noise
• Quantization produces « Quantization noise »• A linear measurement scale would result in a lower SNR for small
signals than for big signals
• What we want is an amplitude independent SNR
Time division multiplexing
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Claude Rigault, ENST 04/10/2004
Communication networks 03 17
‘µ’ Law coding
, maxmax ccyv
vx ==
( )( )µµ++= 1Log
1Log xy
255=µ0
10
20
30
40
50
60
0 0,5 1 1,5
63
1,6
Code
Volts
Time division multiplexing
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Claude Rigault, ENST 04/10/2004
Communication networks 03 18
‘A’ Law coding
0
20
40
60
80
100
120
140
0 0,5 1 1,5 2
Niveau du signal Code sur 13 bits Code sur 8 bits 0 à 25 mV 0 à 63 0 à 3325 à 50 mV 64 à 127 34 à 4950 à 100 mV 128 à 255 50 à 650,1 à 0,2 V 256 à 511 66 à 810,2 à 0,4 V 512 à 1023 82 à 970,4 à 0,8 V 1024 à 2047 98 à 1130,8 à 1,6 V 2048 à 4095 114 à 128
Time division multiplexing
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Claude Rigault, ENST 04/10/2004
Communication networks 03 19
( ) par trame bits 1931824 =+×
Kbit/s 1544 trames/s8000193 =×
v0v1
IT0
IT1
IT23
v23
signalisation
Flag
Primary multiplex T1 (T1 carrier)
Time division multiplexing
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Claude Rigault, ENST 04/10/2004
Communication networks 03 20
Primary multiplex E1
IT16IT0IT1 IT31
Time division multiplexing
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Claude Rigault, ENST 04/10/2004
Communication networks 03 21
E1 frame organization
v1v2
v15v16 v30
IT16IT17
IT0IT1 IT15 IT31
IT30
v29IT0 : x001 1011 ou z1zz zzzz IT16 : supertrame de signalisation
Time division multiplexing
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Claude Rigault, ENST 04/10/2004
Communication networks 03 22
In-band
1
31
215
016
17 30
signalisation500 Hz 8000 Hz
216-216-18
16-1516-31
15
31
16
Time division multiplexing
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Claude Rigault, ENST 04/10/2004
Communication networks 03 23
PCM E1 : superframe
IT16-0IT16-1
IT16-2IT16-13 IT16-15
IT16-14
v 1-16 v 3-18 v 13-28 v 15-30v 2-17 v 14-29
Time division multiplexing
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Claude Rigault, ENST 04/10/2004
Communication networks 03 24
Clock
Data 1 0 1 0 0 01 1
Line signal
The HDB 3 line code
Time division multiplexing
• 1 ⇒ Mark, 0 ⇒ Space• Alternate Mark Inversion
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Claude Rigault, ENST 04/10/2004
Communication networks 03 25
The HDB 3 line code
1 0 1 0 0 0 00 0 0 00
• Coding of sequences of 4 zeros : alternate violations inversion
Time division multiplexing
0 0 0 0
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Claude Rigault, ENST 04/10/2004
Communication networks 03 26
Line Termination
circuit 1
circuit 30
MUX LT
circuit 1
circuit 30
DE-MUXLT
HDB 3 Line code
RepeaterGalvanic insulationRemote feedingLine code
circuit 1
circuit 30
MUXLT
circuit 1
circuit 30
DE-MUX LT
Time division multiplexing
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Claude Rigault, ENST 04/10/2004
Communication networks 03 27
Asynchronous Transmission
0 01 0 110 1
0 1 01 0 1 01
> te/2
( )re
r
er
e
ree
fff
ff
ftt
tn −=
−
=−= 2112
1
)(2
Time division multiplexing
• Slips occur after n bits
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Claude Rigault, ENST 04/10/2004
Communication networks 03 28
Asynchronous Transmission
Time division multiplexing
• Start and Stop signals required• Caracter Oriented Procedure (COP)
Te
Tr Tr Tr Tr Tr
Te Te Te TeStart Stop
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Claude Rigault, ENST 04/10/2004
Communication networks 03 29
Synchronous Transmission
0 0 01 1 1 1 0
HORLOGE
SIGNAL
Time division multiplexing
• 2 channels required : one for data, one for clock• Bit Oriented Procedure (BOP)
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Claude Rigault, ENST 04/10/2004
Communication networks 03 30
Mixing clock and data
• Line codes such as the Manchester code give a mean to recover the clock, at the expanse of bandwidth
Time division multiplexing
0 0 01 1 1 1 0
Clock
DataLine code
Line code
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Claude Rigault, ENST 04/10/2004
Communication networks 03 31
Asynchronous multiplexing
signal 1
signal 4
clock 1
clock 4
elastic store
elastic store
MUX
Clock out
Control ./. 4
1
4
f1
f4
fo
Time division multiplexing
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Claude Rigault, ENST 04/10/2004
Communication networks 03 32
Justification
signal 1
signal 4
clock 1
clock 4
elastic store
elastic store
MUX
Clock out
Control ./. 4
1
4
f1
f4
fo
io
ij
ffnTT−
==
4
1
Time division multiplexing
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Claude Rigault, ENST 04/10/2004
Communication networks 03 33
European PDH hierarchy1
30
E 1 1
464 kbit/s
2 Mbit/s
E 2 1
4
8 Mbit/s
E 3 1
4
34 Mbit/s
E 4 1
4
E 5
140 Mbit/s
565 Mbit/s
Time division multiplexing
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Claude Rigault, ENST 04/10/2004
Communication networks 03 34
American PDH hierarchy
Time division multiplexing
1
24
T 1 1
456 kbit/s
1,5 Mbit/s
T 21
7
6 Mbit/s
T 344 Mbit/s
• Caution ! One T3 multiplexes 7 T2 !
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Claude Rigault, ENST 04/10/2004
Communication networks 03 35
Point to point structure of PDH networks
64 kbit/s2 Mbit/s
2 Mbit/s
64 Kbit/s2 Mbit/s
2 Mbit/s
8 Mbit/s
E1
E2
E1
E2
Time division multiplexing
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Claude Rigault, ENST 04/10/2004
Communication networks 03 36
SDH : Adding and Dropping
order>n+1ADM
The condition : synchronous multiplexing
Time division multiplexing
order norder norder norder n
order norder norder norder n
order norder norder norder n
order norder norder norder n
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Claude Rigault, ENST 04/10/2004
Communication networks 03 37
SDH : the STM-1 frame
RegeneratorSectionoverhead
Pointers overhead Payload
9 Bytes 261 Bytes
9 rows
Time division multiplexing
STM-1 : Synchronous transfer module
MultiplexerSectionoverhead
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Claude Rigault, ENST 04/10/2004
Communication networks 03 38
Container and Virtual Container
POH
C
VC
C + POH → VC
Time division multiplexing
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Claude Rigault, ENST 04/10/2004
Communication networks 03 39
Synchronous multiplexing (high order)
• High Order Path (high order multiplex)
Time division multiplexing
pointerHigh order VC
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Claude Rigault, ENST 04/10/2004
Communication networks 03 40
Synchronous multiplexing (low order)
pointer
POH
Low order VC
• Low Order Path (low order multiplex)
Time division multiplexing
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Claude Rigault, ENST 04/10/2004
Communication networks 03 41
SDH mechanisms
• C + POH → VC• Low order VC + pointer → TU• High order VC + pointer → AU
Time division multiplexing
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Claude Rigault, ENST 04/10/2004
Communication networks 03 42
SDH tributaries
E4 140Mbit/sC4
T3 44 Mbit/sC3
7E3 34Mbit/s
T2 6 Mbit/sC2
4E1 2Mbit/sC12
T1 1,5 Mbit/sC11
USEuropeContainer
Time division multiplexing
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Claude Rigault, ENST 04/10/2004
Communication networks 03 43
Multiplexing paths
C-4
C-12
C-2
C-11
C-3
VC-12
VC-11
VC-2
VC-3
TU-2
TU-12
TU-11
TUG-2
TU-3TUG-3
VC-4
VC-3
AU-4
AU-3
AUGSTM-1
1
3
4
77
3
3
Time division multiplexing