1 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

2 다중화 (Multiplexing) z 다중화 (Multiplexing) ~ is the set of techniques that allows the simultaneous transmission of multiple signals across a single data link.

3 다중화 (Multiplexing) zMultiplexing vs. No Multiplexing

4 8.1 Many to One/One to Many z 다중화기 (Multiplexer) ~ transmission streams combine into a single stream(many to one) z 다중 복구기 (Demultiplexer) ~ stream separates into its component transmission(one to many) and directs them to their intended receiving devices

5 8.2 Types of Multiplexing zCategories of Multiplexing

6 Types of Multiplexing(cont’d) zFDM(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

7 Types of Multiplexing(cont’d) zFDM process yeach telephone generates a signal of a similar frequency range ythese signal are modulated onto different carrier frequencies(f1, f2, f3)

8 Types of Multiplexing(cont’d) zFDM multiplexing process, time-domain

9 Types of Multiplexing(cont’d) zFDM multiplexing process, frequency-domain

10 Types of Multiplexing(cont’d) zDemultiplexing ~ separates the individual signals twin their carries and passes them to the waiting receivers.

11 Types of Multiplexing(cont’d) zFDM demultiplexing process, time-domain

12 Types of Multiplexing(cont’d) zFDM demultiplexing, frequency-domain

13 Types of Multiplexing(cont’d) zExample : Cable Television ycoaxial cable has a bandwidth of approximately 500Mhz yindividual television channel require about 6Mhz of bandwidth for transmission ycan carry 83 channels theoretically

14 Types of Multiplexing(cont’d) zTDM(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

15 Types of Multiplexing(cont’d) zTDM

16 Types of Multiplexing(cont’d) zTDM can be implemented in two ways ySynchronous TDM yAsynchronous TDM

17 Types of Multiplexing(cont’d) zSynchronous TDM ~ the multiplex allocates exactly the same time slot to each device at all times, whether or not a device has anything to transmit.

18 Types of Multiplexing(cont’d) zFrame yTime slots are grouped into frame yA frame consists of one complete cycle of time slots, including one or more slots dedicated to each sending device, plus framing bits.

19 Types of Multiplexing(cont’d) zSynchronous TDM

20 Types of Multiplexing(cont’d) zInterleaving ~ switch moves from device to device at a constant rate and in a fixed order

21 Types of Multiplexing(cont’d) zDemultiplexer decomposes each frame by discarding the framing bits and extracting each character in turn zSynchronous TDM, demultiplexing process

22 Types of Multiplexing(cont’d) zFraming bits ~ allows the demultiplexer to synchronize with the incoming stream so that it can separate the time slots accurately (ex: ….)

23 Types of Multiplexing(cont’d) zSynchronous TDM Example

24 Types of Multiplexing(cont’d) zAsynchronous TDM

25 Types of Multiplexing(cont’d) zExamples of asynchronous TDM frames a. Case 1: Only three lines sending data

26 Types of Multiplexing(cont’d) b. Case 2: Only four lines sending data

27 Types of Multiplexing(cont’d) c. Case 3: All five lines sending data

28 Types of Multiplexing(cont’d) zInverse 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

29 Types of Multiplexing(cont’d) zMultiplexing and inverse multiplexing

30 Types of Multiplexing(cont’d) zWhy do we need inverse multiplexing? ~ wants to send data, voice, and video each of which requires a different data rate. [example] yvoice - 64 Kbps link ydata Kbps link yvideo - 1,544 Mbps link

Multiplexing application : Telephone system zTelephone Network

32 Multiplexing application(cont’d) zCommon Carrier Services

33 Multiplexing application(cont’d) zAnalog Service

34 Multiplexing application(cont’d) zAnalog Switched Service ~ is the familiar dial-up service most often encountered when using a home telephone (PSTN : Public Switched Telephone Network)

35 Multiplexing application(cont’d) zAnalog Leased Service ~ offers customers the opportunity to lease line(dedicated line), that is permanently connected to another customer.

36 Multiplexing application(cont’d) zAnalog Hierarchy ~ To maximize the efficiency of their infrastructure, telephone companies have traditionally multiplexed signals from lower bandwidth lines onto higher bandwidth lines.

37 Multiplexing application(cont’d) zAnalog hierarchy

38 Multiplexing application(cont’d) zDigital Services yadvantage - less sensitive than analog service to noise - lower cost

39 Multiplexing application(cont’d) zCategories of digital service

40 Multiplexing application(cont’d) zSwitched/56 service ~ is the digital version of an analog switched line ~ allows data rates of up to 56Kbps

41 Multiplexing application(cont’d) zDDS(Digital Data Service) ~ is the digital version of an analog leased line (maximum speed : 56Kbps)

42 Multiplexing application(cont’d) zDS(Digital Signal) Service ~ is a hierarchy of digital signal

43 Multiplexing application(cont’d) zDS Service yDS-0 : single digital channel of 64Kbps yDS-1 : 1,544Mbps, y24 개의 64Kbps + 8Kbps 의 overhead yDS-2 : 6,312Mbps, y96 개의 64Kbps+168Kbps 의 overhead yDS-3 : 44,376Mbps, y672 개의 64Kbps+1,368Mbps 의 overhead yDS-4 : 274,176Mbps, y4032 개의 64Kbps+16,128Mbps 의 overhead

44 Multiplexing application(cont’d) zT Lines ServiceLineRate(Mbps)Voice Channels DS-A DS-2 DS-3 DS-4 T-1 T-2 T-3 T-4 1,544 6,312 44, ,

45 Multiplexing application(cont’d) zT line for Analog Transmission

46 Multiplexing application(cont’d) zT-1 frame structure

47 Multiplexing application(cont’d) zFractional T Lines

48 Multiplexing application(cont’d) zE Lines yEuropeans 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, ,

49 Multiplexing application(cont’d) zOther Multiplexing Service yISDN(Integrated Service Digital Network) ySONET(Synchronous Optical Network) yATM(Asynchronous Transfer Mode)