Data Communication

Data Communication

The term communication means sending or receiving information. When we communicate, we share information or data. A communication system can be defined as the collection of hardware and software that facilitates intersystem exchange of information between different devices.

It is the exchange of data between two devices using some form of transmission media. It includes the transfer of data or information and the method of preservation of data during the transfer process. Data is transferred from one place to another in the form of signals. There are three types of signals

1. Digital Signal In this signal, data is transmitted in electronic form of data, i.e. binary digits (0 or 1).
2. Analog Signal In this signal, data is transmitted in the form of radiowaves like in telephone line.
3. Hybrid Signal These signals have properties of both analog signal and digital signal.

Communication Channel

The communication channel refers to the direction of signal flow between two linked devices.

Types of Communication Channel

There are mainly three types of communication channel

(i) Simplex Channel In this channel, the flow of data is always in one direction, with no capability to support response in other direction. This communication is unidirectional. Only one of the communicating devices transmits information and the other can only receive it. e.g. Radio, Television, Keyboard, etc.

(ii) Half Duplex Channel In this channel, the data can flow in both directions, but not at a same time. When one device transmits information, then other can only receive at that point of time. e.g. Walkie-Talkie.

(iii) Full Duplex Channel In this channel, the How of data is in both directions at a time, i.e. both stations can transmit and receive information simultaneously, e.g. Wireless handset (mobile phone).

Communication Media

Communication media of a network refer to the transmission media or the connecting media used in the network. It can be broadly defined as anything that can carry information from a source to destination. It refers to the physical media through which communication signals can be transmitted from one point to another.

Transmission media can be divided into two broad categories

Guided Media or Wired Technologies

The data signal in guided media is bound by the cabling system that guides the data signal along a specific path. It consists of a cable composed of metals like copper, tin or silver.

Basically, they are divided into three categories

(i) Ethernet Cable or Twisted Pair In this pair, wires are twisted together, which are surrounded by an insulating material and an outer layer called jacket. A twisted pair consists of two conductors (copper). One of the wires is used to carry signals to the receiver and the other is used only as a ground reference. It is used as a short distance communication, e.g. Local area networks use twisted pair cable.

(ii) Co-axial Cable It carries the signal of higher frequency data communication through the network. It consists of a solid wire core surrounded by foil shielded or conducting braid or wire mesh, each separated by some insulator. It has a single inner conductor that transmits electric signals and the outer conductor acts as a ground and is wrapped in asheath of teflon or PVC. Co-axial cable is commonly used in transporting multi-channel television signals in cities, e.g. Cable TV network.

Unguided Media or Wireless Technologies

It is the transfer of information over a distance without the use of enhanced electrical conductors or wires. When the computers in a network are interconnected and data is transmitted through waves, then they are said to be connected through unguided media. Some commonly used unguided media of transmission are

(i) Radiowave Transmission When two terminals communicate by using radio frequencies then such type of communication is known as radiowave transmission. This transmission is also known as Radio Frequency (RF) transmission. These are omnidirectional. Radiowaves, particularly those waves that propagate in the sky mode, can travel long distances. Each computer attaches to an antenna that can both send and receive radio transmission.

(ii) Microwave Transmission Microwaves are electromagnetic waves having frequencies range from 0.3 to 300 GHz. Microwaves are unidirectional. Microwaves have a higher frequency than that of radiowaves.

Microwave is one of the fastest media for data transmission over communication channel. They can be aimed at a single direction instead of broadcasting in all direction. Microwave antenna placed on the top of buildings. It consists series of stations approx. 30 miles apart. It is used in cellular network and television broadcasting.

(iii) Infrared Wave Transmission Infrared waves are the high frequency waves used for short-range communication. These waves do not pass through the solid-objects. They are mainly used in TV remote, wireless speakers.

(iv) Satellite Communication The communication across longer distances can be provided by combining radio frequency transmission with satellites. It works over a long distance and fast communication. Satellite communication amplifies signal received from one Earth station and again, retransmits to another Earth station, which can be located many thousands of miles away. It is used for communication to ships, vehicles, planes and handheld terminals.

Tit-Bits

• Bluetooth is a wireless technology used for exchanging data over short distances to create a Personal Area Network (PAN).
• Bandwidth determines the data transfer rate which is measured in Cycle per Second (CPS) or Hertz (Hz).
• Throughput is the amount of data that is actually transmitted between the two computers. It is specified in bits per second (bps). Giga bits per second (Gbps) is the fastest speed unit per data transmission.
• Baud is used to measure the speed of signaling and data transfer.

Computer Network

It is a collection of two or more computers., which are connected together to share information and resources. Computer network is a combination of hardware and software that allows communication between computers over a network.

Benefits of Networking

Some of the benefits of network are discussed below

(i) File Sharing Networking of computer helps the users to share data files.

(ii) Hardware Sharing Users can share devices such as printers, scanners, CD-ROM drives, hard drives, etc.

(iii) Application Sharing Applications can be shared over the network and this allows implementation of client/server applications.

(iv) User Communication This allows users to communicate using E-mail, newsgroups, video conferencing within the network.

Types of Computer Network

Computer network is broadly classified into various types

Local Area Network (LAN)

LAN is a small and single-site network. It connects network devices over a relatively short distance. It is a system in which computers are interconnected and the geographical area such as home, office, buildings, school may be within a building to 1 km. On most LANs, cables are used to connect the computers. LANs are typically owned, controlled and managed by a single person or organisation. They also use certain specific connectivity technologies, primarily Ethernet and Token Ring. LAN provides a sharing of peripherals in an efficient or effective way.

Wide Area Network (WAN)

A WAN is a geographically dispersed collection of LANs. A WAN like the Internet spans most of the world. A network device called a router connects LANs to a WAN. Like the Internet, most WANs are not owned by any one organisation, but rather exist under collective or distributed ownership and management. WANs use technology like ATM, Frame Relay and X.25 for connectivity.

Metropolitan Area Network (MAN)

It is a data network designed for a town or city. It connects an area larger than a LAN, but smaller than a WAN, such as a city, with dedicated or high performance hardware.

Its main purpose is to share hardware and software resources by the various users. Cable TV network is an example of metropolitan area network. The computers in a MAN are connected using co-axial cables or fibre optic cables.

Personal Area Network (PAN)

PAN refers to a small network of communication. These are used in a few limited range, which is in reachability of individual person. Few examples of PAN are Bluetooth, wireless USB, Z-wave and Zig Bee.

Virtual Private Network (VPN)

VPN is a technology that is gaining popularity among large organisations that use the global Internet for both intra-and inter-organisation communications, but require privacy in their intra-organisation communication. VPN is a network that is private but virtual.

It is private because it guarantees privacy inside the organisation. It is virtual because it does not use real private WANs; the network is physically public but virtually private.

• Server /s a system that responds to requests across a computer network to provide a network service. It can be run on a dedicated computer. It is one of the most powerful and typical computer.
• File Server is a type of computer used on network that provides access to files. It allows users to share programs and data over LAN network.
• Protocols are the set of rules used by a network for communication. It is mainly used to connect all the computers to the network.