Encoding and Modulating
Different Conversion Schemes

Encoding
digitizing
Modulating
Modulating
Digital Signal Analog Signal
Digital to Digital Encoding
Types of Digital to Digital Encoding
Unipolar Encoding
It uses only one polarity, usually 1.
 Disadvantages

◦ DC Component
◦ Synchronization
 Problems occurs when long data stream

It is obsolete today
Polar Encoding


Uses two voltage levels
NRZ- Nonreturn to Zero
◦ Level of the signal is always positive or negative.
◦ Two types of NRZ
 NRZ-L
 +ve voltage is represents a bit 0
 NRZ-I
 Synchronization is provided


RZ- Return Zero
NRZ-L
NRZ-L and NRZ-I Encoding
RZ Encoding
Manchester and Diff. Manchester
Encoding
Types of Bipolar Encoding
Bipolar AMI Encoding
B8ZS Encoding
HDB3 Encoding
Example
Using B8ZS, encode the bit stream 10000000000100.
Assume that the polarity of the first 1 is positive.
Analog to Digital Encoding
Pulse Amplitude Modulation (PAM)
Quantized PAM Signal
PCM
From Analog to PCM
From Analog to PCM
From Analog to PCM
From Analog to PCM
Nyquist Theorem
Digital to Analog Encoding
Amplitude Shift Keying(ASK)
Bandwidth for ASK
Frequency Shift Keying(FSK)
Bandwidth for FSK
Phase Shift Keying(PSK)
PSK
Constellation
4-PSK
4-PSK
Characteristics
Bit Rate and Baud Rate
Analog to Analog Modulation
Amplitude Modulation
AM Bandwidth
AM Band Allocation
Frequency Modulation
FM Bandwidth
FM Band Allocation
Transmission of
Digital Data
Interfaces and Modems
Digital Data Transmission
 DTE-DCE Interface
 Other Interface Standards
 Modems

Parallel Transmission
Serial Transmission
Asynchronous Transmission
Synchronous Transmission
DTEs and DCEs
DTE-DCE interface
Electromagnetic Spectrum
Twisted-Pair Cable
Shielded Twisted-Pair Cable
Coaxial Cable
Refraction
Critical Angle
Reflection
Multimode Step-Index
Multimode Graded-Index
Single Mode
Fiber Construction
Transmission Impairment
Attenuation
 Distortion
 Noise

Performance
Throughput
 Propagation Speed
 Propagation Time

Wavelength