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5 장 부호화 (Encoding)

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  1. 5 장 부호화(Encoding) 5.1 Digital-to-Digital 5.2 Analog-to-Digital 5.3 Digital-to-Analog 5.4 Analog-to-Analog 5.5 요약

  2. 부호화(cont’d) • Information must be encoded into signals before it can be transported across communication media. • Different encoding schemes

  3. 5.1 Digital-to-Digital 부호화 ~ is the representation of digital information by a digital signal. • Digital-to-Digital encoding

  4. Digital-to-Digital 부호화(cont’d) • Types of digital-to-digital encoding

  5. Digital-to-Digital 부호화(cont’d) • Unipolar ~ uses only one level of value(1: positive value, 0: idle) • Unipolar encoding

  6. Digital-to-Digital 부호화(cont’d) • Unipolar encoding problems • DC(Direct Current)Component : 직류 • Synchronization(동기)

  7. Digital-to-Digital 부호화(cont’d) • Polar ~ uses two levels (positive and negative) of amplitude. • Types of polar encoding

  8. Digital-to-Digital 부호화(cont’d) • NRZ(Non-Return to Zero) • NRZ-L : the level of the signal is dependent upon the state of the bit • NRZ-I : the signal is inverted if a 1 is encountered

  9. Digital-to-Digital 부호화(cont’d) • NRZ-L and NRZ-I encoding

  10. Digital-to-Digital 부호화(cont’d) • RZ(Return to Zero) ~ use three value(positive, negative, zero) 1 : positive-to-zero 0 : negative-to-zero

  11. Digital-to-Digital 부호화(cont’d) • RZ encoding

  12. Digital-to-Digital 부호화(cont’d) • Biphase ~ is implemented in two different ways. • Manchester • Differential Manchester

  13. Digital-to-Digital 부호화(cont’d) • Manchester and Differential Manchester encoding

  14. Digital-to-Digital 부호화(cont’d) • Bipolar ~ uses three voltage levels(positive, negative,zero) • zero level : binary 0 • positive and negative voltage : 1(alternate)

  15. Digital-to-Digital 부호화(cont’d) • Types of bipolar encoding

  16. Digital-to-Digital 부호화(cont’d) • Bipolar AMI(Alternate Mark Inversion) ~ is the simplest type of bipolar encoding • Bipolar AMI encoding

  17. Digital-to-Digital 부호화(cont’d) • B8ZS(Bipolar 8-Zero Substitution) ~ is the convention adopted in North America to provide synchronization of long strings of 0s.

  18. Digital-to-Digital 부호화(cont’d) • B8ZS encoding

  19. Digital-to-Digital 부호화(cont’d) • HDB3(High-Density Bipolar 3) ~ is the convention adopted in Europe and Japan.

  20. Digital-to-Digital 부호화(cont’d) • HDB3 encoding

  21. Digital-to-Digital 부호화(cont’d) • Example 5.1 • compare the bandwidth needed for unipolar encoding and RZ encoding. • Solution • RZ need twice the bandwidth of unipolar encoding.

  22. Digital-to-Digital 부호화(cont’d) • Solution to Example 5.1

  23. Digital-to-Digital 부호화(cont’d) • Example 5.2 • compare the bandwidth needed for Manchester and Differential Manchester encoding. • Solution ~ are the same.

  24. Digital-to-Digital 부호화(cont’d) • Example 5.3 • using B8ZS, encode the bit stream 10000000000100. Assume that polarity of the first 1 is positive. • Solution

  25. Digital-to-Digital 부호화(cont’d) • Example 5.4 • using HDB3, encoded the bit stream 10000000000100. Assume that the number of 1s so far is odd and the first 1 is positive. • Solution

  26. 5.2 Analog-to-Digital 부호화 ~ is the representation of analog analog information by a digital signal. • Analog-to-Digital Encoding

  27. Analog-to-Digital 부호화(cont’d) • PAM(Pulse Amplitude Modulation) ~ This technique takes analog information, samples it, and generates a series of pulses based on the results of the sampling.

  28. Analog-to-Digital 부호화(cont’d) • PAM

  29. Analog-to-Digital 부호화(cont’d) • PCM(Pulse Code Modulation) ~ Quantization is a method of assigning interal values in a specific range to sampled instances.

  30. Analog-to-Digital 부호화(cont’d) • Quantized PAM signal

  31. Analog-to-Digital 부호화(cont’d) Assign sign and magnitude value (seven-bit binary equivalent) • Quantized sample  • Quantizing using and magnitude

  32. Analog-to-Digital 부호화(cont’d) • The binary digits are then transformed into a digital signal using one of the digital-to-digital encoding techniques(예 : unipolar) • PCM

  33. Analog-to-Digital 부호화(cont’d) • From analog signal to PCM digital code

  34. 5.3 Digital-to-Analog 부호화 • ASK(Amplitude Shift Keying) • FSK(Frequency Shift Keying) • PSK(Phase Shift Keying) • QAM(Quadrature Amplitude Modulation)

  35. Digital-to-Analog 부호화(cont’d) • Types of Digital-to-Analog encoding

  36. Digital-to-Analog 부호화(cont’d) • Bit rate : the number of bits per second. • Baud rate : the number of signal units per second.  Baud rate is less than or equal to the bit rate. • 반송신호(Carrier Signal) • base signal for the information signal

  37. Digital-to-Analog 부호화(cont’d) • ASK(Amplitude Shift Keying) ~ Both frequency and phase remain constant while the amplitude changes.

  38. Digital-to-Analog 부호화(cont’d) • ASK encoding

  39. Digital-to-Analog 부호화(cont’d) • FSK(Frequency Shift Keying) ~ the frequency of the signal is varied to represent binary 1 or 0.

  40. Digital-to-Analog 부호화(cont’d) • FSK encoding

  41. Digital-to-Analog 부호화(cont’d) • PSK(Phase Shift Keying) ~ the phase is varied to represent binary 1 or 0.

  42. Digital-to-Analog 부호화(cont’d) • PSK

  43. Digital-to-Analog 부호화(cont’d) • QAM(Quadrature Amplitude Modulation) ~ means combining ASK and PSK in such a way that we have contrast between each bit, dibit, tribit, quadbit, and so on.

  44. Digital-to-Analog 부호화(cont’d) • Time domain for on 8-QAM signal

  45. 5.4 Analog-to-Analog 부호화 ~ is the representation of analog information by an analog signal. • Analog-to-Analog encoding

  46. Analog-to-Analog 부호화(cont’d) • Type of analog-to-analog encoding

  47. Analog-to-Analog 부호화(cont’d) • AM(Amplitude Modulation) ~ The frequency and phase of the carrier remain the same; only the amplitude changes to follow variations in the information.

  48. Analog-to-Analog 부호화(cont’d) • Amplitude modulation

  49. Analog-to-Analog 부호화(cont’d) • AM bandwidth ~ The total bandwidth required for AM can be determined from the bandwidth of the audio signal.

  50. Analog-to-Analog 부호화(cont’d) • AM bandwidth