1 8 장 다중화 (multiplexing) 8.1 many to one/one to many 8.2 type of multiplexing 8.3...

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8 장 다중화 (Multiplexing)

8.1 Many to One/One to Many

8.2 Type of Multiplexing

8.3 Multiplexing Application : Telephone

system

8.4 요약

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다중화 (Multiplexing)


~ is the set of techniques that allows the simultaneous transmission of multiple signals across a single data link.

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Multiplexing vs. No Multiplexing

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8.1 Many to One/One to Many

다중화기 (Multiplexer)

~ transmission streams combine into a single stream(many to one)

다중 복구기 (Demultiplexer)

~ stream separates into its component transmission(one to many) and directs them to their intended receiving devices

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8.2 Types of Multiplexing

Categories of Multiplexing

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Types of Multiplexing(cont’d)FDM(Frequency-Division Multiplexing)

~ is an analog technique that can be applied when the bandwidth of a link is greater them the combined bandwidths of the signals to be transmitted

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Types of Multiplexing(cont’d)

FDM process each telephone generates a signal of a similar

frequency range these signal are modulated onto different carrier

frequencies(f1, f2, f3)

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FDM multiplexing process, time-domain

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FDM multiplexing process, frequency-domain

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Demultiplexing

~ separates the individual signals twin their carries and passes them to the waiting receivers.

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FDM demultiplexing process, time-domain

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FDM demultiplexing, frequency-domain

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Example : Cable Television coaxial cable has a bandwidth of approximately

500Mhz individual television channel require about 6Mhz

of bandwidth for transmission can carry 83 channels theoretically

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TDM(Time-Division Multiplexing)

~ is a digital process that can be applied when the data rate capacity of the transmission medium is greater that the data rate required by the sending and receiving device

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TDM

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TDM can be implemented in two ways

Synchronous TDM

Asynchronous TDM

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Synchronous TDM

~ the multiplex allocates exactly the same time slot to each device at all times, whether or not a device has anything to transmit.

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Frame Time slots are grouped into frame A frame consists of one complete cycle of time

slots, including one or more slots dedicated to each sending device, plus framing bits.

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Synchronous TDM

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Types of Multiplexing(cont’d)Interleaving

~ switch moves from device to device at a constant rate and in a fixed order

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Demultiplexer decomposes each frame by discarding the framing bits and extracting each character in turn

Synchronous TDM, demultiplexing process

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Framing bits~ allows the demultiplexer to synchronize with the i

ncoming stream so that it can separate the time slots accurately

(ex: 01010101 ….)

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Synchronous TDM Example

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Asynchronous TDM

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Examples of asynchronous TDM frames

a. Case 1: Only three lines sending data

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b. Case 2: Only four lines sending data

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2

3

4

5

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c. Case 3: All five lines sending data

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Inverse Multiplexing

~ takes the data stream from one high-speed line and breaks it into portion that can be sent across several lower speed lines simultaneously, with no loss in the collective data rate

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Multiplexing and inverse multiplexing

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Why do we need inverse multiplexing?

~ wants to send data, voice, and video each of which requires a different data rate.

[example] voice - 64 Kbps link data - 128 Kbps link video - 1,544 Mbps link

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8.3 Multiplexing application : Telephone system

Telephone Network

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Multiplexing application(cont’d)

Common Carrier Services

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Analog Service

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Multiplexing application(cont’d)Analog Switched Service

~ is the familiar dial-up service most often encountered when using a home telephone

(PSTN : Public Switched Telephone Network)

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Multiplexing application(cont’d)Analog Leased Service

~ offers customers the opportunity to lease line(dedicated line), that is permanently connected to another customer.

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Analog Hierarchy

~ To maximize the efficiency of their infrastructure, telephone companies have traditionally multiplexed signals from lower bandwidth lines onto higher bandwidth lines.

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Analog hierarchy

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Digital Services advantage

- less sensitive than analog service to noise

- lower cost

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Categories of digital service

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Switched/56 service

~ is the digital version of an analog switched line

~ allows data rates of up to 56Kbps

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DDS(Digital Data Service)

~ is the digital version of an analog leased line (maximum speed : 56Kbps)

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DS(Digital Signal) Service

~ is a hierarchy of digital signal

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Multiplexing application(cont’d)DS Service

DS-0 : single digital channel of 64Kbps

DS-1 : 1,544Mbps,

24 개의 64Kbps + 8Kbps 의 overhead

DS-2 : 6,312Mbps,

96 개의 64Kbps+168Kbps 의 overhead

DS-3 : 44,376Mbps,

672 개의 64Kbps+1,368Mbps 의 overhead

DS-4 : 274,176Mbps,

4032 개의 64Kbps+16,128Mbps 의 overhead

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T LinesService Line Rate(Mbps) Voice Channels

DS-A

DS-2

DS-3

DS-4

T-1

T-2

T-3

T-4

1,544

6,312

44,736

274,176

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96

672

4032

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T line for Analog Transmission

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T-1 frame structure

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Fractional T Lines

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E Lines Europeans use a version of T lines called E lines

Service Rate(Mbps) Voice Channels

E-1

E-2

E-3

E-4

2,048

8,448

34,368

139,264

30

120

480

1920

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Other Multiplexing Service

ISDN(Integrated Service Digital Network)

SONET(Synchronous Optical Network)

ATM(Asynchronous Transfer Mode)

1 8 장 다중화 (multiplexing) 8.1 many to one/one to many 8.2 type of multiplexing 8.3...

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