DATA COMMUNICATION Lecture14 Recap of Lecture 13 w

Recap of Lecture 13 w Signals w Analog and Digital Data & Signals w

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

Introduction w Information must be transformed into signals before it can be transformed across

Digital-to-Digital Conversion w Digital-to-Digital conversion/encoding is the representation of digital information by digital signal

Types of Digital-to-Digital Encoding Digital/Digital Encoding Unipolar Polar Bipolar

Unipolar Encoding w Simple and Primitive w Almost Obsolete Today w Study provides introduction

Pros and Cons of Unipolar Encoding w PROS – Straight Forward and Simple –

Synchronization Example w Bit Rate = 1000 bps w 1000 bits ----- 1 second

Polar Encoding w Polar encoding uses two voltage levels – One positive and one

Non Return to Zero (NRZ) w The level of signal is either positive or

Summary w Introduction to the Encoding Techniques w Digital-To-Digital Encoding w Types of Digital-To-Digital

Suggested Reading w Section 5. 1, “Data Communications and Networking” 2 nd Edition by

Slides: 20

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DATA COMMUNICATION Lecture-14

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

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

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

Conversion Methods

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

Digital-to-Digital Conversion

Types of Digital-to-Digital Encoding Digital/Digital Encoding Unipolar Polar Bipolar

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

Unipolar Encoding

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

Synchronization Example w Bit Rate = 1000 bps w 1000 bits ----- 1 second w 1 bit -----= 0. 001 sec w Positive voltage of 0. 005 sec means five 1’s w Sometimes it stretches to 0. 006 seconds and an extra 1 bit is read by the Receiver

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

Types of Polar Encoding

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

Non Return to Zero-Level (NRZ-L)

Non Return to Zero-Invert (NRZ-I)

Summary w Introduction to the Encoding Techniques w Digital-To-Digital Encoding w Types of Digital-To-Digital Encoding w Uni. Polar Encoding w Polar Encoding – NRZ

Suggested Reading w Section 5. 1, “Data Communications and Networking” 2 nd Edition by Behrouz A. Forouzan

DATA COMMUNICATION Lecture-14