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DATA COMMUNICATION AND NETWORKING
Sub Topic 11.1: Introduction to Data Communication
Sub-topic Objectives:
a. defining data communication.
b. explaining the elements of data communication (sender, receiver, messages, transmission media and protocol).
c. defining data communication tools
d. describing types of electronic data communication tools like computers, mobile phones, the Internet, among others.
e. comparing electronic and manual data communication tools (manual drums, bells and messengers).
f. defining data transmission media.
g. differentiating between physical transmission media and wireless transmission media.
h. describing services offered by data communication tools like E-mail, Skype, News groups, and instant messaging.
i. explaining the implications of using data communication services.
Definition of terminologies
A computer Network is a collection of two or more computers and devices connected by channels so that they can communicate with each other and share resources: Examples of resources
Encoding: This is the process through which Information (e.g. data, text, voice or video) from the sending device is converted into signals which the communication medium can carry.
Transmission: This is the process through which the signals are broad cast/ sent out through the medium to the receiving device.
Decoding: This is the process through which the signals are converted back into the information in its original form in the receiving device.
Telecommunication refers to transmission of data and information over a long-distance, eg television
Teleprocessing: This refers to access and modification of computer files located elsewhere.
Downloading: To Download is to transfer a file to your computer from another.
Uploading means to transfer a file from your computer to another.
Throughput refers to the rate of how much data is moved during a certain amount of time. The amount of signals that can travel over a communications channel sometimes is called the Bandwidth. The higher the bandwidth, the more data and information the channel can transmit.
Data Encryption: This is Process of converting data into coded form (cypher text) to prevent it from being read or understood by unauthorized people. Encrypted data is difficult to decode without a secret key
Communications Software: This refers to a set of instructions (software) needed by a computer before it starts sending and receiving data from other computers.
Importance of computer communication
Limitations of computer communication
Transmission media (Channels)
Transmission media refers to the physical materials that are used to transmit data between computers. For communications between computers that are linked by cable, there are three choices:
Twisted wire
Twisted pair cable comes in two varieties: Shielded and Unshielded Twisted Pair (UTP). UTP is the most popular
Advantages:
Disadvantage:
Coaxial cable
Advantages
Disadvantages
Fiber Optic Cable
Each strand, called an optical fiber, is as thin as a human hair. Each optical fiber is surrounded by an insulating glass cladding and a protective coating. Fiber-optic cables are used by many local and long-distance telephone companies, cable TV, and in high-traffic networks or as the main cable in a network.
Advantages:
Disadvantages:
Wireless telecommunications technologies transport digital communications without cables between communications devices. Wireless transmission media used in communications include broadcast radio, cellular radio, microwaves, communications satellites, and infrared & bluetooth.
Wireless transmission is more convenient than installing cables but it has Slower data transfer than hard-wired methods and it is also Subject to interference.
Microwave
Advantage:
Disadvantage:
A satellite is basically a microwave station placed in outer space. The satellite receives a signal from the earth, amplifies it, and then rebroadcasts it at a different frequency to any number of earth-based stations.
Satellite In The Rays Of Light. 3D Scene.
Infrared and Bluetooth IrDA (Infrared Data Association) ports transmit data via infrared light waves. As long as the devices are within a few feet and nothing obstructs the path of the infrared light wave, data can be transferred without the use of cables.
Physical transmission media and wireless transmission media
Advantages of physical over wireless transmission media
Disadvantages of physical transmission media
Services offered by data communication tools
Data communication tools offer services like Telephone, SMS, E-mail, Skype, Newsgroups and instant messaging.
Positive Implications
Negative Implications
DATA TRANSMISSION
Telecommunications involves the transmission of data, information, and instructions among computers. Any transmissions sent during these communications can be categorized by a number of characteristics including the signal type, transmission mode, transmission direction, and transmission rate.
Signal Type: Recall that computers produce digital signals yet telephone equipment originally was designed to carry only voice transmission in the form of an analog signal.
Analog Signals
An analog signal uses variations which are represented by a continuous waveform to convey information. It is particularly useful for wave data like sound waves. Analog signals are what normal phone line and sound speakers use.
Digital Signals
A digital signal is a series of discrete (discontinuous) bits which are simply the presence or absence of an electric pulse. The state of being on or off represents the binary digit of 1 or 0, respectively.
Advantages of digital signals include:
Transmission Modes
When two devices exchange data, the data flows between the devices as a continuous stream of bits.
There are two basic transmission techniques for separating the groups of bits: asynchronous transmission and synchronous transmission
Asynchronous transmission
Asynchronous transmission transmits one byte at a time over a line at random intervals. Each byte is framed by controls—a start bit for marking the beginning of the byte, a stop bit for marking the end of the byte, and a parity bit for error checking. Asynchronous transmission is relatively slow and used for low-speed transmission.
Synchronous transmission
Synchronous transmission transmits groups of bytes simultaneously at regular intervals. The beginning and ending of a block of bytes is determined by the timing of the sending device and receiving devices.
Although synchronous transmission requires more complicated and expensive communications devices, it provides much higher speeds and greater accuracy than asynchronous transmission.
Transmission Direction
The direction in which data flows along transmission media is characterized as
Simplex transmission
Simplex transmission sends data in one direction only. Simplex transmission is used only when the sending device does not require a response from the receiving device. One example of simplex transmission is television broadcasting.
Half-duplex transmission
Full-duplex transmission
In full-duplex transmission, data can flow in both directions at the same time. A regular telephone line, for example, supports full-duplex transmission, allowing both parties to talk at same time.
Multiplex transmission
In multiplex transmission, several different types of signals can be carried at once through the same line. E.g. During Video calls where Images
Assignment
ASSIGNMENT : CS6: Assignment on Data Communication and Networking MARKS : 25 DURATION : 45 minutes