1. Introduction to Data communication
Unit 1
Lecture 1
Introduction to Data communication

2. Syllabus of Unit 1 Data Communication: Introduction Components
Data representation
Data flow and basic model
Serial & Parallel transmission
Modes of data transmission
Encoding: Unipolar, Polar, Bipolar
Line & Block codes
Data compression
Lossy & Lossless techniques
Review of analog & digital
Transmission methods.

3. A Foreword What is Data? What is Communication?
What is Data Communication?
What is the need of Data Communication?

4. What is Data?

5. Data
Data is defined as the entities that convey meaning or information. Signals are electric or electromagnetic representation of data.
Data can be two types :
Analog data
Digital data

6. Analog data :
Analog data is the type of data that varies continuously (smoothly) with respect to time. Voice and Video are the best examples of analog data. The other examples are temperature, pressure etc.
Digital data :
Digital data is the type of data that can take on discrete(clearly fixed) values. The examples of digital data are text and integers.

7. What is data communication?
The aim of data communication and networking is to facilitate the exchange of data such as audio, text, video between any points in the world
The word Data refers to the information which is presented in a form that is agreed by the users and creators of data.
Data communication is the exchange of data between two devices via some form of transmission medium, e.g. Computer to Computer, Computer to printer, sending , browsing internet sites such as Facebook, Instagram, twitter & LinkedIn etc.

8. Components of Data communication?
It has the following five components
Message
Sender
Medium
Receiver
Protocol

9. Figure 1.1 Five components of data communication

10. 1 Message
Message is nothing but information or data which is to be sent from one point to the other
A message can be in the form of sound, text, number, picture, video or combination of them.
2 Sender
Sender is the device which sends the message.
3 Medium
It is the physical path over which the message travels from the sender to the receiver, it can be wired or wireless.

11. 4 Receiver
It is the device which receives the message.
5 Protocol
Protocol is defined as the set of rules which govern data communication.
The connection of two devices takes place via the communication medium, but the actual communication between them will take place with the help of protocol.

12. Fundamentals characteristics of Data communication?
The fundamental characteristics of a Data communication system are:
Delivery
Accuracy
Timeliness
1. Delivery
The data should be delivered to the correct destination. It should reach only to the intended user and not to any other.

13. 2. Accuracy
There is a possibility of data alternation or corruption when it is travelling over a communication medium. This will affect the accuracy of the received data.
The data communication system should be such that it should deliver data accurately.
3. Timelines
For the audio and video data, the system should deliver the data in a timely manner i.e. deliver as it is produced without any time delay.
Such a data delivery is called as real-time transmission of data.

14. Definition of communication channel
It is also called as communication medium.
The communication channel is the medium used for transmission of electronic signal from one place to other.
The communication medium can be conducting wires, cables, optical fiber or free space atmosphere.
Depending on the type of communication medium we define , two types of communication systems.
Wired communication or line communication.
Wireless communication or radio communication

15. Model of Communication System
Figure

16. Description of model of data communication
Suppose that the input device and transmitter are the components of a personal computer. The user of this PC wants to send a message to another m PC.
Then the message m will be in the form of a digital bit stream and labeled as input data as shown in figure.
The sender PC is connected to some transmission medium such as a local network or a telephone line, by an input/output device such as a local network transceiver or a modem.

17. The input data are transferred to an transmitter as a sequence of voltage shifts that represent bits on a transmission cable or communication bus.
The transmitter is connected directly to the medium and converts the incoming digital bit stream into an analog single suitable for transmission over the communication cable.
The analog transmitter signals travels on the transmission medium and is subjected to a number of impairments, before reaching the receiver.
Due to this impairments, the receiver signal may be different from the transmitted signal.

18. The receiver tries to estimate the original signal based on the distorted received signal, and the knowledge of transmission medium.
A sequence of digital bits is produced at the output of the receiver.
These bits are then sent to the destination which is another PC. The signal m represent the output information which is represented to the user and can be seen on the computer screen or printed using a printer.