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) zInformation must be encoded into signals before it can be transported across communication media. zDifferent encoding schemes

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

4 Digital-to-Digital 부호화 (cont’d) zTypes of digital-to-digital encoding

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

6 Digital-to-Digital 부호화 (cont’d) zUnipolar encoding problems yDC(Direct Current)Component : 직류 ySynchronization( 동기 )

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

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

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

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

11 Digital-to-Digital 부호화 (cont’d) zRZ encoding

12 Digital-to-Digital 부호화 (cont’d) zBiphase ~ is implemented in two different ways. yManchester yDifferential Manchester

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

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

15 Digital-to-Digital 부호화 (cont’d) zTypes of bipolar encoding

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

17 Digital-to-Digital 부호화 (cont’d) zB8ZS(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) zB8ZS encoding

19 Digital-to-Digital 부호화 (cont’d) zHDB3(High-Density Bipolar 3) ~ is the convention adopted in Europe and Japan.

20 Digital-to-Digital 부호화 (cont’d) zHDB3 encoding

21 Digital-to-Digital 부호화 (cont’d) zExample 5.1 ycompare the bandwidth needed for unipolar encoding and RZ encoding. zSolution yRZ need twice the bandwidth of unipolar encoding.

22 Digital-to-Digital 부호화 (cont’d) zSolution to Example 5.1

23 Digital-to-Digital 부호화 (cont’d) zExample 5.2 ycompare the bandwidth needed for Manchester and Differential Manchester encoding. zSolution ~ are the same.

24 Digital-to-Digital 부호화 (cont’d) zExample 5.3 yusing B8ZS, encode the bit stream Assume that polarity of the first 1 is positive. zSolution

25 Digital-to-Digital 부호화 (cont’d) zExample 5.4 yusing HDB3, encoded the bit stream Assume that the number of 1s so far is odd and the first 1 is positive. zSolution

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

27 Analog-to-Digital 부호화 (cont’d) zPAM(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) zPAM

29 Analog-to-Digital 부호화 (cont’d) zPCM(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) zQuantized PAM signal

31 Analog-to-Digital 부호화 (cont’d) zQuantized sample  zQuantizing using and magnitude Assign sign and magnitude value (seven-bit binary equivalent)

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

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

Digital-to-Analog 부호화 zASK(Amplitude Shift Keying) zFSK(Frequency Shift Keying) zPSK(Phase Shift Keying) zQAM(Quadrature Amplitude Modulation)

35 Digital-to-Analog 부호화 (cont’d) zTypes of Digital-to-Analog encoding

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

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

38 Digital-to-Analog 부호화 (cont’d) zASK encoding

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

40 Digital-to-Analog 부호화 (cont’d) zFSK encoding

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

42 Digital-to-Analog 부호화 (cont’d) zPSK

43 Digital-to-Analog 부호화 (cont’d) zQAM(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 zTime domain for on 8-QAM signal Digital-to-Analog 부호화 (cont’d)

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

46 Analog-to-Analog 부호화 (cont’d) zType of analog-to-analog encoding

47 Analog-to-Analog 부호화 (cont’d) zAM(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) zAmplitude modulation

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

50 Analog-to-Analog 부호화 (cont’d) zAM bandwidth

51 Analog-to-Analog 부호화 (cont’d) zAudio signal( 음성과 음악 ) bandwidth : 5 KHz zMinimum bandwidth : 10 KHz zAM stations are allowed carrier frequencies anywhere between 530 and 1700 KHz(1.7 MHz)

52 Analog-to-Analog 부호화 (cont’d) zAM band allocation

53 Analog-to-Analog 부호화 (cont’d) zFM(Frequency Modulation) ~ as the amplitude of the information signal changes, the frequency of the carrier changes proportionately.

54 Analog-to-Analog 부호화 (cont’d) zFrequency modulation

55 Analog-to-Analog 부호화 (cont’d) zFM Bandwidth ~ is equal to 10 times the bandwidth of the modulation signal.

56 Analog-to-Analog 부호화 (cont’d) zFM bandwidth

57 Analog-to-Analog 부호화 (cont’d) zBandwidth of an audio signal( 음성과 음악 ) broadcast in stereo : 15 KHz zminimum bandwidth : 150 KHz zallows generally 200 KHz(0.2 MHz) for each station zFM station are allowed carrier frequencies anywhere 88 and 108 MHz(each 200 KHz)

58 Analog-to-Analog 부호화 (cont’d) zFM band allocation

59 Analog-to-Analog 부호화 (cont’d) zPM(Phase Modulation) ~ is used in some systems as an alternative to frequency modulation.