1. Computer Network Lab. 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. Computer Network Lab. 2 다중화 (Multiplexing) n 다중화 (Multiplexing) ~ is the set of techniques that allows the simultaneous transmission of multiple signals across a single data link.

3. Computer Network Lab. 3 다중화 (Multiplexing) n Multiplexing vs. No Multiplexing

4. Computer Network Lab. 4 8.1 Many to One/One to Many n 다중화기 (Multiplexer) ~ transmission streams combine into a single stream(many to one) n 역다중화기 (Demultiplexer) ~ stream separates into its component transmission(one to many) and directs them to their intended receiving devices

5. Computer Network Lab. 5 8.2 Types of Multiplexing n Categories of Multiplexing

6. Computer Network Lab. 6 Types of Multiplexing(cont’d) n 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

7. Computer Network Lab. 7 Types of Multiplexing(cont’d) n FDM process l each telephone generates a signal of a similar frequency range l these signal are modulated onto different carrier frequencies(f1, f2, f3)

8. Computer Network Lab. 8 Types of Multiplexing(cont’d) n FDM multiplexing process, time-domain

9. Computer Network Lab. 9 Types of Multiplexing(cont’d) n FDM multiplexing process, frequency-domain

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

11. Computer Network Lab. 11 Types of Multiplexing(cont’d) n FDM demultiplexing process, time-domain

12. Computer Network Lab. 12 Types of Multiplexing(cont’d) n FDM demultiplexing, frequency-domain

13. Computer Network Lab. 13 Types of Multiplexing(cont’d) n Example : Cable Television l coaxial cable has a bandwidth of approximately 500Mhz l individual television channel require about 6Mhz of bandwidth for transmission l can carry 83 channels theoretically

14. Computer Network Lab. 14 Types of Multiplexing(cont’d) n 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

15. Computer Network Lab. 15 Types of Multiplexing(cont’d) n TDM

16. Computer Network Lab. 16 Types of Multiplexing(cont’d) n TDM can be implemented in two ways l Synchronous TDM l Asynchronous TDM

17. Computer Network Lab. 17 Types of Multiplexing(cont’d) n 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.

18. Computer Network Lab. 18 Types of Multiplexing(cont’d) n Frame l Time slots are grouped into frame l A frame consists of one complete cycle of time slots, including one or more slots dedicated to each sending device, plus framing bits.

19. Computer Network Lab. 19 Types of Multiplexing(cont’d) n Synchronous TDM

20. Computer Network Lab. 20 Types of Multiplexing(cont’d) n Interleaving ~ switch moves from device to device at a constant rate and in a fixed order

21. Computer Network Lab. 21 Types of Multiplexing(cont’d) n Demultiplexer decomposes each frame by discarding the framing bits and extracting each character in turn n Synchronous TDM, demultiplexing process

22. Computer Network Lab. 22 Types of Multiplexing(cont’d) n Framing bits ~ allows the demultiplexer to synchronize with the incoming stream so that it can separate the time slots accurately (ex: 01010101 ….)

23. Computer Network Lab. 23 Types of Multiplexing(cont’d) n Synchronous TDM Example

24. Computer Network Lab. 24 Types of Multiplexing(cont’d) n Asynchronous TDM

25. Computer Network Lab. 25 Types of Multiplexing(cont’d) n Examples of asynchronous TDM frames a. Case 1: Only three lines sending data

26. Computer Network Lab. 26 Types of Multiplexing(cont’d) b. Case 2: Only four lines sending data 1234512345

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

28. Computer Network Lab. 28 Types of Multiplexing(cont’d) n 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

29. Computer Network Lab. 29 Types of Multiplexing(cont’d) n Multiplexing and inverse multiplexing

30. Computer Network Lab. 30 Types of Multiplexing(cont’d) n Why do we need inverse multiplexing? ~ wants to send data, voice, and video each of which requires a different data rate. [example] l voice - 64 Kbps link l data - 128 Kbps link l video - 1,544 Mbps link

31. Computer Network Lab. 31 8.3 Multiplexing application : Telephone system n Telephone Network

32. Computer Network Lab. 32 Multiplexing application(cont’d) n Common Carrier Services

33. Computer Network Lab. 33 Multiplexing application(cont’d) n Analog Service

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

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

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

37. Computer Network Lab. 37 Multiplexing application(cont’d) n Analog hierarchy

38. Computer Network Lab. 38 Multiplexing application(cont’d) n Digital Services l advantage - less sensitive than analog service to noise - lower cost

39. Computer Network Lab. 39 Multiplexing application(cont’d) n Categories of digital service

40. Computer Network Lab. 40 Multiplexing application(cont’d) n Switched/56 service ~ is the digital version of an analog switched line ~ allows data rates of up to 56Kbps

41. Computer Network Lab. 41 Multiplexing application(cont’d) n DDS(Digital Data Service) ~ is the digital version of an analog leased line (maximum speed : 56Kbps)

42. Computer Network Lab. 42 Multiplexing application(cont’d) n DS(Digital Signal) Service ~ is a hierarchy of digital signal

43. Computer Network Lab. 43 Multiplexing application(cont’d) n DS Service l DS-0 : single digital channel of 64Kbps l DS-1 : 1,544Mbps, 24 개의 64Kbps + 8Kbps 의 overhead l DS-2 : 6,312Mbps, 96 개의 64Kbps+168Kbps 의 overhead l DS-3 : 44,376Mbps, 672 개의 64Kbps+1,368Mbps 의 overhead l DS-4 : 274,176Mbps,4032 개의 64Kbps+16,128Mbps 의 overhead

44. Computer Network Lab. 44 Multiplexing application(cont’d) n T 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 44,736 274,176 24 96 672 4032

45. Computer Network Lab. 45 Multiplexing application(cont’d) n T line for Analog Transmission

46. Computer Network Lab. 46 Multiplexing application(cont’d) n T-1 frame structure

47. Computer Network Lab. 47 Multiplexing application(cont’d) n Fractional T Lines

48. Computer Network Lab. 48 Multiplexing application(cont’d) n E Lines l 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

49. Computer Network Lab. 49 Multiplexing application(cont’d) n Other Multiplexing Service l ISDN(Integrated Service Digital Network) l SONET(Synchronous Optical Network) l ATM(Asynchronous Transfer Mode)

50. Computer Network Lab. 50 8.4 요약