8 장 다중화 (Multiplexing)

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

3. 다중화(Multiplexing) • Multiplexing vs. No Multiplexing

4. 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

5. 8.2 Types of Multiplexing • Categories of Multiplexing

6. 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

7. 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)

8. Types of Multiplexing(cont’d) • FDM multiplexing process, time-domain

9. Types of Multiplexing(cont’d) • FDM multiplexing process, frequency-domain

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

11. Types of Multiplexing(cont’d) • FDM demultiplexing process, time-domain

12. Types of Multiplexing(cont’d) • FDM demultiplexing, frequency-domain

13. Types of Multiplexing(cont’d) • 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

14. Types of Multiplexing(cont’d) • 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. Types of Multiplexing(cont’d) • TDM

16. Types of Multiplexing(cont’d) • TDM can be implemented in two ways • Synchronous TDM • Asynchronous TDM

17. Types of Multiplexing(cont’d) • 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. Types of Multiplexing(cont’d) • 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.

19. Types of Multiplexing(cont’d) • Synchronous TDM

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

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

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

23. Types of Multiplexing(cont’d) • Synchronous TDM Example

24. Types of Multiplexing(cont’d) • Asynchronous TDM

25. Types of Multiplexing(cont’d) • Examples 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 1 2 3 4 5

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

28. Types of Multiplexing(cont’d) • 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. Types of Multiplexing(cont’d) • Multiplexing and inverse multiplexing

30. Types of Multiplexing(cont’d) • 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

31. 8.3 Multiplexing application : Telephone system • Telephone Network

32. Multiplexing application(cont’d) • Common Carrier Services

33. Multiplexing application(cont’d) • Analog Service

34. 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)

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

36. Multiplexing application(cont’d) • Analog 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) • Analog hierarchy

38. Multiplexing application(cont’d) • Digital Services • advantage - less sensitive than analog service to noise - lower cost

39. Multiplexing application(cont’d) • Categories of digital service

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

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

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

43. Multiplexing application(cont’d) • DS Service • DS-0 : single digital channel of 64Kbps • DS-1 : 1,544Mbps, • 24개의 64Kbps + 8Kbps의 overhead • DS-2 : 6,312Mbps, • 96개의 64Kbps+168Kbps의 overhead • DS-3 : 44,376Mbps, • 672개의 64Kbps+1,368Mbps의 overhead • DS-4 : 274,176Mbps, • 4032개의64Kbps+16,128Mbps의 overhead

44. Multiplexing application(cont’d) • T Lines Service 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 24 96 672 4032

45. Multiplexing application(cont’d) • T line for Analog Transmission

46. Multiplexing application(cont’d) • T-1 frame structure

47. Multiplexing application(cont’d) • Fractional T Lines

48. Multiplexing application(cont’d) • E Lines • Europeans use a version of T lines called E lines Voice Channels Rate(Mbps) Service 2,048 8,448 34,368 139,264 30 120 480 1920 E-1 E-2 E-3 E-4

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