Network CommunicationsChapter 6

Multiplexers and Switching Concepts

Mutiplexer Application

Host C o mp uter

M ultip le xer

A

B

C

D

DC BATermina ls

Figure 6.1

4 to 1 Mux / DeMux

A

B

C

D

Inputs Output DCBA

Select lines

4*1 MUX

Figure 6.2Multiplexer

DMUX

1*4Input DCBA

AB

C

D

Select Lines

012

3

Figure 6.3Demultiplexer

TDM Multiplexer

MUX

4*1

AAA

B-B

CCC

-DD

Inputs

Output -CBA DC-A DCBA

t0t1t2

Frame #3 #2 #1

Figure 6.4

FDM (Broadcast Analog TV)

Channel 2 Channel 3 Channel 4 Channel 5

Channel 2

Channel 3

Channel 4

0 6Mhz

0 6Mhz

FDM Coaxial Cable50 56 62 68

Figure 6.5

Statistical Multiplexer(Packets)

SPM

AAA

-BB

CC-

DDD

Output DCA DCBA DBA

Figure 6.6

Digital Telephone System

Central OfficeCentral

Office

Digital Signal

Analog SignalAnalog Signal

Figure 6.7

Sampling - PAMPulse Amplitude Modulation

Figure 6.8

Time

Voltage

Analog Signal

Time

Voltage

Pulse Amplitude Modulation (PAM)

Analog / Digital Conversion

011101100101010000110010000100001001101010111100110111101111

Figure 6.9

T1 (DS1)

Figure 6.10

TDM

PCM

PCM

Analog 1

Analog 2

PCM

Analog 24

1.544 Mbps Digital signalVoice Inputs

Digital

DS-0

DS-0

DS-0

DS-1

(8 bit/sample)*(24 ch/frame) = 192 bit/frameadd 1 synchronization bit/frame for 193 b/frame

Multiply by the sampling rate of 8 kHz= 1.544 Mbits/sec (64 kbit/sec each channel)

Digital Telephone Transmission

Figure 6.11: DS-1 Frame Format

Byte#1Byte#2Byte#24 Byte#231 bit

Table 6.1: US TDM Standards

A Fully Connected Network

Computer A Computer B

Computer C Computer D

Figure 6.12

Connecting Stations Through Switches

Switch 1

AB

Switch 3Switch 2

Switch 4

Figure 6.13

Circuit Switching

Figure 6.14

C

D

E

Switch 1 Switch 2

AB

1

2

Packet Switching(A Virtual Circuit)

Switch #1

Switch #3

Switch #2 Switch #4

Switch #5

Destination

Virtual Connection

CBA

Source

C

A

B

Figure 6.15