Data Communication

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

Elements of Data Communication System Transmitter Medium Receiver

Characteristics of Communication System Delivery Accuracy Timeliness

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

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

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

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

Elements of Protocol Syntax Semantics Timing

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

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

Types of Data Transmission Modes Parallel Transmission Serial Transmission

Methods of Data Transmission Asynchronous Transmission Synchronous Transmission

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

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

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

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

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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

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