Multiplexing techniques Surasak Sanguanpong nguan@ku.ac.th - - PDF document

Applied Network Research Group Department of Computer Engineering, Kasetsart University 1/6

Multiplexing techniques

Surasak Sanguanpong nguan@ku.ac.th http://www.cpe.ku.ac.th/~nguan

Last updated: 9 Feb 2001 Applied Network Research Group Department of Computer Engineering, Kasetsart University 2/6

Why multiplexing?

share a use of common path

Multiplexer Demultiplexer 3 channels on a single physical path

M U X No multiplexing

D E M U X

Multiplexing

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Synchronous Synchronous Asynchronous Asynchronous

Type of Multiplexing

Time Division Multiplex (TDM) Time Division Multiplex (TDM)

Multiplexing

Frequency Division Multiplex (FDM) Frequency Division Multiplex (FDM) Wavelength Division Multiplex (WDM) Wavelength Division Multiplex (WDM)

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Channel 1 Channel 2 Channel 3

Frequency Division Multiplex

M U X

D E M U X

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FDM MUX/DEMUX

CH2 CH1 CH3

+

CH1 CH2 CH3

CH2 CH1 CH3

• riginal

signal decompose the multiplexed signal with filters Each signal is modulated to a different carrier frequency

• uput

signal

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1

Time Division Multiplex

M U X

D E M U X

2 3

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TDM MUX/DEMUX

CH2 CH1 CH3

1 2 3

CH2 CH1 CH3

• Multiple digital signals interleaved in time
• May be at bit level of blocks
• Time slots pre-assigned to sources and fixed

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Asynchronous TDM

A B C D

Data to be sent

t1 t2 t3

A1 B1 C1 D1 C2 D2 A2 B2

1st cycle 2nd cycle

Synchronous TDM

waste bandwidth A1 B1 C2 B2

1st cycle 2nd cycle

Asynchronous TDM

extra bandwidth available

Also called Statistical TDM

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TDM in the Telephone System

• Most common application of TDM is in the telephone

system

• Analog voice signals are digitized using PCM

1

M U X

D E M U X

2 3 . . N

How much bandwidth is required for 32 voice channels?

Data rate = 8 bits * 8000 KHz = 64 Kbps Bandwidth = 64 Kbps * 32 = 2.048 Mbps

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Wavelength Division Multiplexing

M U X

D E M U X

λ1 λ2 λ3 λ4 λ5 λ6 λ1 λ2 λ3 λ4 λ5 λ6 λx λy

Wave which has wavelength between λx andλy

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1

Inverse Multiplexing

M U X

D E M U X

2 3

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Analog Carrier System

F D M

4 KHz 12 voice channels

F D M F D M F D M

Group Supergroup 2.52 MHz 600 Voice Channels 240 KHz 60 Voice Channels 48 KHz 12 Voice Channels Mastergroup Jumbogroup 16.984 MHz 3600 Voice Channels 5 Groups 10 Supergroups 6 Mastergroups

North American FDM Carrier Standard F D M

3 Jumbogroup 57.442 MHz 10800 Voice Channels

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Digital Carrier System

T D M DS0 T D M T D M T D M DS1

24 voice channels 4 DS1 7 DS2 6 DS3 64 Kbps 1.544 Mbps 24 Voice Channels

DS2

6.312 Mbps 96 Voice Channels

DS3

44.376 Mbps 672 Voice Channels

DS4

274.176 Mbps 4032 Voice Channels

North American TDM Carrier Standard