1. Session 2

2. Objectives: By the end of this session, the student will be able to: • Distinguish between data and signals. Cite the advantages of digital data and signals over analog data and signals • Identify the 3 basic components of a signal • Discuss the bandwidth of a signal & how it relates to data transfer speed • Identify signal strength and attenuation, and how they are related • Outline the basic characteristics of transmitting analog data with analog signals, digital data with digital signals, digital data with analog signals and analog data with digital signals • List and draw diagrams of the basic digital encoding techniques, and explain the advantages and disadvantages of each • Identify the different shift keying (modulation) techniques and describe their advantages, disadvantages, and uses • Identify the two most common digitization techniques and describe their advantages and disadvantages • Discuss the characteristics and importance of spread spectrum encoding techniques • Identify the different data codes and how they are used in communication systems

3. Analog Waveform 3

4. Analog Waveform – with Noise 4

5. Digital Waveform 5

6. Digital Waveform - Noise 6

7. Digital Waveform – More Noise 7

8. Analog Signals Frequency Amplitude Spectrum? Bandwidth? Effective bandwidth? 8

9. Analog Signals B Y X A Spectrum Human Voice Spectrum: 300Hz – 3400Hz Bandwidth: 3100Hz Bandwidth = Y – X Effective Bandwidth = B - A 9

10. Waveforms - Phase 10

11. Attenuation / Amplification dB = 10log10(P2 / P1) P1 – power level at transmitter P2 – power level at receiver A loss of 50% power is -3dB. Whether the loss is from 1000W to 500W or from 10W to 5W. 11

12. Analog Data / Analog Signals 12

13. Digital Encoding Schemes 13

14. Digital Encoding Schemes NRZ-L (Non-Return to Zero Level) Binary 0 – represented by presence of voltage Binary 1 – represented by absence (or low) voltage 14

15. Digital Encoding Schemes NRZ-I (Non-Return to Zero Inverted) Binary 0 – represented by no voltage change at the time mark Binary 1 – represented by a change in voltage at the time mark What happens to NRZ-I and NRZ-L encoding when transmitting a long series of binary zeros? 15

16. Digital Encoding Schemes Manchester Binary 0 – represented by change from high to low in the middle of the time mark Binary 1 – represented by a change from low to high in the middle of the time mark 16

17. Digital Encoding Schemes Differential Manchester Binary 0 – represented by change at the beginning of the time mark Binary 1 – represented by no change at the beginning of the time mark What happens to Manchester and Differential Manchester encoding when transmitting a long series of binary zeros? Self-clocking 17

18. Bipolar-AMI • Bipolar-AMI Digital Encoding • 3 voltage levels: • binary 0 = zero voltage • binary 1 = positive or negative voltage sent depending on last binary 1 sent (negative voltage last sent -> positive voltage sent this time) 18

19. 4B/5B Digital Encoding Scheme 19

20. Amplitude Key Shifting 20

21. Amplitude Key Shifting 21

22. Frequency Key Shifting 22

23. Phase Key Shifting 23

24. Quadrature Phase Key Shifting 24

25. Quadrature Amplitude Key Shifting 25

26. Pulse Code Modulation 26

27. Pulse Code Modulation 27

28. Pulse Code Modulation • Twice the sample rate 28

29. Delta Modulation 29

30. Frequency Hopping Spread Spectrum 30

31. Direct Sequence Spread Spectrum 31

32. EBCDIC 32

33. ASCII 33

34. Review NRZ-L NRZ-I Manchester DiffManchester Bipolar-AMI 4B/5B Encoding 0V 0V 0V 0V 0V 34 0V