Data Communication and Network - Module 1

Table of Contents

1.1 - Basic Data Communication System – Data, Signaling, and Transmission System :-

1.1.1 Introduction to Data Communications

Data Communication means the process of sending and receiving data (like text, images, video, etc.) from one place to another using some medium (like wire, air, fiber optics).

Definition: Data Communication is the exchange of Communication is the exchange of data between two or more devices through some transmission medium such as a wire cable or wireless signal.

1.1.2 Basic Data Communication System

A Basic Data Communication System consists of the following components:

Component Description:

  • Message: The data or information to be communicated (text, image, video, etc.)
  • Sender: The device that sends the message (e.g., computer, phone)
  • Receiver: The device that receives the message (e.g., another computer)
  • Transmission Medium: The channel through which the data travels (e.g., cables, air)
  • Protocol: Set of rules that both sender and receiver follow for communication

Real Life Example :-

💡Imagine you send a photo from your phone to your friend's phone using WhatsApp:

  • Sender: Your phone
  • Message: The photo
  • Receiver: Friend's phone
  • Medium: Internet (via mobile network or Wi-Fi)
  • Protocol: WhatsApp uses TCP/IP for communication

1.1.3 Signaling

Definition:

Signaling is the process of converting data into signals so that it can be transmitted over a communication medium such as wires, optical fibers, or air
(in case of wireless communication).

In simple terms, signaling determines how information is represented and sent from one device to another.

When data needs to travel between devices, it cannot move as raw binary or text. Instead, it must be converted into electrical, optical, or electromagnetic signals that can move through the transmission medium.

Types of Signals :-

There are mainly two types of signals used in communication systems:

(i) Analog Signal

(ii) Digital Signal

(i) Analog Signal

Definition: An analog signal is a continuous wave that changes smoothly over time and represents variations in some physical quantity such as voltage, current, or frequency.

Nature: Continuous in both time and amplitude.

Used In: Traditional communication systems like radios, telephones, and TV transmissions.

Example : When you speak on a traditional (landline) phone, your voice produces sound waves that are continuous. These sound waves are converted into an analog electrical signal that varies smoothly according to the pressure and tone of your voice.

Graph Representation : The waveform of a digital signal looks like a square wave with clear transitions between two levels (high and low).

(ii) Digital Signal

Definition: A digital signal consists of discrete values, usually represented by binary digits (0 and 1). Each bit represents a distinct voltage level.

Nature: Discrete in both time and amplitude (not continuous).

Used In: Computers, digital communication systems, and modern devices like smartphones, routers, and digital televisions.

Example : When you speak on a mobile phone, your analog voice is first converted into a digital signal (a sequence of 0s and 1s). This digital data is then transmitted through the network. At the receiver's end, it is again converted back into an analog form so that the person can hear your voice naturally.

Graph Representation : The waveform of a digital signal looks like a square wave with clear transitions between two levels (high and low).

Key Differences Between Analog and Digital Signals :

Feature Analog Signal Digital Signal
Nature Continuous signal Discrete signal
Representation Varies continuously (waveform) Represented by 0s and 1s
Accuracy More prone to noise and distortion Less affected by noise
Transmission Used in old communication systems Used in modern digital systems
Example Voice in landline phones, radio Data in computers, mobile communication