1. Data Communication

2. Introduction
Communication means the exchange of information or messages
The transfer of data (information) from one computer system to another system is called Data Communication
Data is transmitted electronically from one system to other systems using standard methods
Data is transmitted from one place to another in the form of signals, which may be in analog or digital form

3. Elements of Data Communication System
Transmitter
Medium
Receiver

4. Characteristics of Communication System
Delivery
Accuracy
Timeliness

5. Packets
Message/data is broken into small groups or data segments before being transmitted from one communication device to another
Includes the following information
Payload
Header

6. Signals
The data is transmitted from one place to another in the form of electromagnetic or light waves through communication medium
The electromagnetic or light waves representing data called signals

7. Types of Data Transmission
Analog Data Transmission
Transfer data in the form of analog signals or in the form of continuous waves
Digital Data Transmission
Transfer data in the form of digital signals

8. Data Communication Protocol
The software that guides or instructs computer system and devices about how data is to be transferred from one place to another
All machine based communications must follow certain set of rules for exchange of data between sender and receiver
The set of rules is called protocol
This software enables us to communicate with other systems

9. Elements of Protocol
Syntax
Semantics
Timing

10. Functions of Data Communication Protocol
Data Sequencing
Divide the long message into small packets of fixed size
Data Routing
Find the most efficient path or route between the sender and receiver
Flow Control
Control the rate of data transmission from the sender to the receiver
Error Control
Detect and recover errors for successful data communication between the sender and receiver

11. Data Transmission Modes
The manner or way in which data is transmitted from one place to another is called data transmission mode
Simple Mode
Half Duplex Mode
Full Duplex Mode

12. Types of Data Transmission Modes
Parallel Transmission
Serial Transmission

13. Methods of Data Transmission
Asynchronous Transmission
Synchronous Transmission

14. Distinguish between Asynchronous and Synchronous Transmission
Data is transmitted character by character while data is transmitted block by block or word by word

15. Communication Channel
Bandwidth measures the amount of information that can be transmitted through the media within the given period of time
For analog signals bandwidth is measured in hertz
For digital signals, it is represented in bits per second
Different transmission media have different bandwidth

16. Categories of Transmission Media
Guided Media/Physical Transmission Media
Unguided Media/Wireless Transmission Media

17. Physical Transmission Media
Communication devices are directly linked with each other via cables or other physical material for data communication
Also referred to as wired channel
Usually used in LAN
Physical transmission media used in transmission are:
Twisted Pair Cable
Coaxial Cable
Fiber-Optic Cable

18. Twisted Pair Cable

19. Coaxial Cable

20. Fiber Optic Cable

21. Wireless Transmission Media
Communication devices communicate with each other and data is communicated through the air or space using broadcast radio signals, microwave signals and infrared signals
This transmission medium is used when it is impossible to install the cables
Commonly used wireless transmission media are:
Broadcast Radio
Cellular Radio
Microwaves
Communication Satellite
Infrared

22. References
Introduction to Information Technology by Riaz Shahid, CM Aslam and Safia Iftikhar
The Concepts of Information Technology by Imran Saeed, Ahsan Raza, Tariq Mehmood and Zafar Hussain