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

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## 5 장 부호화 (Encoding)

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**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**부호화(cont’d)**• Information must be encoded into signals before it can be transported across communication media. • Different encoding schemes**5.1 Digital-to-Digital 부호화**~ is the representation of digital information by a digital signal. • Digital-to-Digital encoding**Digital-to-Digital 부호화(cont’d)**• Types of digital-to-digital encoding**Digital-to-Digital 부호화(cont’d)**• Unipolar ~ uses only one level of value(1: positive value, 0: idle) • Unipolar encoding**Digital-to-Digital 부호화(cont’d)**• Unipolar encoding problems • DC(Direct Current)Component : 직류 • Synchronization(동기)**Digital-to-Digital 부호화(cont’d)**• Polar ~ uses two levels (positive and negative) of amplitude. • Types of polar encoding**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**Digital-to-Digital 부호화(cont’d)**• NRZ-L and NRZ-I encoding**Digital-to-Digital 부호화(cont’d)**• RZ(Return to Zero) ~ use three value(positive, negative, zero) 1 : positive-to-zero 0 : negative-to-zero**Digital-to-Digital 부호화(cont’d)**• RZ encoding**Digital-to-Digital 부호화(cont’d)**• Biphase ~ is implemented in two different ways. • Manchester • Differential Manchester**Digital-to-Digital 부호화(cont’d)**• Manchester and Differential Manchester encoding**Digital-to-Digital 부호화(cont’d)**• Bipolar ~ uses three voltage levels(positive, negative,zero) • zero level : binary 0 • positive and negative voltage : 1(alternate)**Digital-to-Digital 부호화(cont’d)**• Types of bipolar encoding**Digital-to-Digital 부호화(cont’d)**• Bipolar AMI(Alternate Mark Inversion) ~ is the simplest type of bipolar encoding • Bipolar AMI encoding**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.**Digital-to-Digital 부호화(cont’d)**• B8ZS encoding**Digital-to-Digital 부호화(cont’d)**• HDB3(High-Density Bipolar 3) ~ is the convention adopted in Europe and Japan.**Digital-to-Digital 부호화(cont’d)**• HDB3 encoding**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.**Digital-to-Digital 부호화(cont’d)**• Solution to Example 5.1**Digital-to-Digital 부호화(cont’d)**• Example 5.2 • compare the bandwidth needed for Manchester and Differential Manchester encoding. • Solution ~ are the same.**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**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**5.2 Analog-to-Digital 부호화**~ is the representation of analog analog information by a digital signal. • Analog-to-Digital Encoding**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.**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.**Analog-to-Digital 부호화(cont’d)**• Quantized PAM signal**Analog-to-Digital 부호화(cont’d)**Assign sign and magnitude value (seven-bit binary equivalent) • Quantized sample • Quantizing using and magnitude**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**Analog-to-Digital 부호화(cont’d)**• From analog signal to PCM digital code**5.3 Digital-to-Analog 부호화**• ASK(Amplitude Shift Keying) • FSK(Frequency Shift Keying) • PSK(Phase Shift Keying) • QAM(Quadrature Amplitude Modulation)**Digital-to-Analog 부호화(cont’d)**• Types of Digital-to-Analog encoding**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**Digital-to-Analog 부호화(cont’d)**• ASK(Amplitude Shift Keying) ~ Both frequency and phase remain constant while the amplitude changes.**Digital-to-Analog 부호화(cont’d)**• ASK encoding**Digital-to-Analog 부호화(cont’d)**• FSK(Frequency Shift Keying) ~ the frequency of the signal is varied to represent binary 1 or 0.**Digital-to-Analog 부호화(cont’d)**• FSK encoding**Digital-to-Analog 부호화(cont’d)**• PSK(Phase Shift Keying) ~ the phase is varied to represent binary 1 or 0.**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.**Digital-to-Analog 부호화(cont’d)**• Time domain for on 8-QAM signal**5.4 Analog-to-Analog 부호화**~ is the representation of analog information by an analog signal. • Analog-to-Analog encoding**Analog-to-Analog 부호화(cont’d)**• Type of analog-to-analog encoding**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.**Analog-to-Analog 부호화(cont’d)**• Amplitude modulation**Analog-to-Analog 부호화(cont’d)**• AM bandwidth ~ The total bandwidth required for AM can be determined from the bandwidth of the audio signal.**Analog-to-Analog 부호화(cont’d)**• AM bandwidth

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