DATA COMMUNICATION Lecture-14

Recap of Lecture 13 Signals Analog and Digital Data & Signals Periodic & Aperiodic Signals Sine Waves and its Characteristics Time and Frequency Domain Frequency Spectrum and Bandwidth Other Definitions of Bandwidth Digital Signals

Overview of Lecture 14 Introduction to the Encoding Techniques Digital-To-Digital Encoding Types of Digital-To-Digital Encoding

Introduction Information must be transformed into signals before it can be transformed across the communication media How this information is transformed depends upon its original format and on the format of the communication hardware

Conversion Methods One by one the boxes will be formed take care of the sequence (start from left) (digital/digital)

Digital-to-Digital Conversion Digital-to-Digital conversion/encoding is the representation of digital information by digital signal For Example: When you transmit data from Computer to the Printer, both original and transmitted data have to be digital

Digital-to-Digital Conversion First of all the the first block the middle blue box and the third box without signal will be shown and there will be no arrows then 1) first block that contains 01011101 will blink(this box should be colored) and the first arrow will be shown (arrow in red color)……….Second the middle box which is in the figure in blue color will blink four times (You can change the color of the box as u like)and then the second arrow tht is after the blue box in the figure will be shown (remember this is only one arrow that is animated so as the second arrow is shown the first arrow will vanish ……………then at the most right hand side the signal will be shown animated……………when the second arrow will vanish as soon as the signal starts coming(we will show the formation of the signal)……………the speed of the animations should be slow in this case

Types of Digital-to-Digital Encoding Digital/Digital Encoding Unipolar Polar Bipolar One by one the boxes will be formed (take care of the sequence)

Unipolar Encoding Simple and Primitive Almost Obsolete Today Study provides introduction to concepts and problems involved with more complex encoding systems

Unipolar Encoding The first scene will show all the things except the red signal ……………..the red signal will be animated ( we will show its formation) ……….the animation should be slow

Pros and Cons of Unipolar Encoding Straight Forward and Simple Inexpensive to Implement CONS DC Component Synchronization

Synchronization Example Bit Rate = 1000 bps 1000 bits ---------- 1 second 1 bit ---------- = 0.001 sec Positive voltage of 0.005 sec means five 1’s Sometimes it stretches to 0.006 seconds and an extra 1 bit is read by the Receiver

Polar Encoding Polar encoding uses two voltage levels One positive and one negative Average voltage level on the line is reduced DC Component problem of Unipolar encoding is alleviated

Types of Polar Encoding One by one the boxes will be formed( take care of the sequence)

Non Return to Zero (NRZ) The level of signal is either positive or negative NRZ NRZ-L NRZ-I

Non Return to Zero-Level (NRZ-L) Now the first scene will show all the figure without the signals tht are in red color…………..second the first signal (above signal) will be animated (we will show its formation) ………..then when the first signal completes its formation then the second signal will come(we will show its animation)………….the most impotant is that the text (NRZ-L) and (NRZ-I) should be in Box with prominent color

Non Return to Zero-Invert (NRZ-I)

Summary Introduction to the Encoding Techniques Digital-To-Digital Encoding Types of Digital-To-Digital Encoding UniPolar Encoding Polar Encoding NRZ

Suggested Reading Section 5.1, “Data Communications and Networking” 2nd Edition by Behrouz A. Forouzan

DATA COMMUNICATION Lecture-14