1. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Physical Layer Summary Data-to-Signal Digital-to-Analog (Modem) Analog-to-Analog (Modem) Digital-to-Digital (line Coding) Analog-Digital (Codec) 1

2. 5.2 DIGITAL-TO-ANALOG CONVERSION DIGITAL-TO-ANALOG CONVERSION Digital-to-analog conversion is the process of changing one of the characteristics of an analog signal based on the information in digital data. Amplitude Shift Keying Frequency Shift Keying Phase Shift Keying Quadrature Amplitude Modulation

3. 5.3 Figure 5.1 Digital-to-analog conversion

4. 5.4 Figure 5.2 Types of digital-to-analog conversion

5. 5.5 Bit rate is the number of bits per second. Baud rate is the number of signal elements per second. In the analog transmission of digital data, the baud rate is less than or equal to the bit rate. Note

6. 5.6 Figure 5.3 Binary amplitude shift keying

7. 5.7 Figure 5.4 Implementation of binary ASK

8. 5.8 Figure 5.6 Binary frequency shift keying

9. 5.9 Figure 5.9 Binary phase shift keying

10. 5.10 Figure 5.11 QPSK and its implementation

11. 5.11 Quadrature amplitude modulation is a combination of ASK and PSK. Note

12. 5.12 ANALOG to ANALOG Conversion ANALOG to ANALOG Conversion Analog-to-analog conversion is the representation of analog information by an analog signal. One may ask why we need to modulate an analog signal; it is already analog. Modulation is needed if the medium is bandpass in nature or if only a bandpass channel is available to us. Amplitude Modulation Frequency Modulation Phase Modulation Topics discussed in this section:

13. 5.13 Figure 5.15 Types of analog-to-analog modulation

14. 5.14 Figure 5.16 Amplitude modulation

15. 5.15 Figure 5.18 Frequency modulation

16. 5.16 Figure 5.20 Phase modulation

17. 9.17 Figure 9.7 Modulation/demodulation

18. 4.18 Digital Transmission -Digital to Digital -Analog to Digital: Codec Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

19. 4.19 DIGITAL-TO-DIGITAL CONVERSION DIGITAL-TO-DIGITAL CONVERSION In this section, we see how we can represent digital data by using digital signals.

20. 4.20 Figure 4.1 Line coding and decoding

21. 4.21 Figure 4.2 Signal element versus data element

22. 4.22 Figure 4.3 Effect of lack of synchronization

23. 4.23 Figure 4.4 Line coding schemes

24. 4.24 Figure 4.5 Unipolar NRZ scheme

25. 4.25 Figure 4.6 Polar NRZ-L and NRZ-I schemes

26. 4.26 Manchester and differential Manchester schemes

27. 4.27 ANALOG-TO-DIGITAL CONVERSION ANALOG-TO-DIGITAL CONVERSION pulse code modulation and …… pulse code modulation and ……

28. 4.28 Figure 4.21 Components of PCM encoder

29. 4.29 According to the Nyquist theorem, the sampling rate must be at least 2 times the highest frequency contained in the signal. Note

30. 4.30 Figure 4.24 Recovery of a sampled sine wave for different sampling rates

31. 4.31 Figure 4.27 Components of a PCM decoder

32. 4.32 TRANSMISSION MODES TRANSMISSION MODES Parallel Transmission Serial Transmission Topics discussed in this section: Topics discussed in this section:

33. 4.33 Figure 4.31 Data transmission and modes

34. 4.34 Figure 4.32 Parallel transmission

35. 4.35 Figure 4.33 Serial transmission

36. 4.36 In asynchronous transmission, we send 1 start bit (0) at the beginning and 1 or more stop bits (1s) at the end of each byte. There may be a gap between each byte. Note

37. 4.37 Asynchronous here means “asynchronous at the byte level,” but the bits are still synchronized; their durations are the same. Note

38. 4.38 Figure 4.34 Asynchronous transmission

39. 4.39 In synchronous transmission, we send bits one after another without start or stop bits or gaps. It is the responsibility of the receiver to group the bits. Note

40. 4.40 Figure 4.35 Synchronous transmission

41. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Subscriber Access - Modem - xDSL - Cable Network 41

42. 9.42 Figure 9.1 A telephone system

43. 9.43 Figure 9.2 Switching offices in a LATA

44. 9.44 Figure 9.4 Data transfer and signaling networks

45. 9.45 DIAL-UP MODEMS DIAL-UP MODEMS Traditional telephone lines can carry frequencies between 300 and 3300 Hz, giving them a bandwidth of 3000 Hz. All this range is used for transmitting voice, where a great deal of interference and distortion can be accepted without loss of intelligibility. Modem Standards Topics discussed in this section:

46. 9.46 Modem stands for modulator/demodulator. Note

47. 9.47 DIGITAL SUBSCRIBER LINE DIGITAL SUBSCRIBER LINE After traditional modems reached their peak data rate, telephone companies developed another technology, DSL, to provide higher-speed access to the Internet. Digital subscriber line (DSL) technology is one of the most promising for supporting high-speed digital communication over the existing local loops. ADSL ADSL Lite HDSL SDSL VDSL Topics discussed in this section:

48. 9.48 Figure 9.11 Bandwidth division in ADSL

49. 9.49 Figure 9.12 ADSL modem

50. 9.50 Figure 9.13 DSLAM

51. 9.51 Table 9.2 Summary of DSL technologies

52. 9.52 Figure 9.15 Hybrid fiber-coaxial (HFC) network

53. 9.53 Figure 9.16 Division of coaxial cable band by CATV

54. 9.54 Figure 9.17 Cable modem (CM)