Communication Is The Activity

Published Date: 02 Nov 2017

Computer Communication

As we simply know that communication is the activity of conveying information through the exchange of thoughts, messages, or information, as by speech, visuals, signals, writing, or behavior. It is same in the term of computers also. When we go some decades back we can see there is no technology for easy communication, like today we have. On that time people uses many different communication method like letters or face-to-face communication, it can be verbal or non-verbal. Now days, computer technology is very popular, efficient and effective technology for communication. As per that time or we can say that communication without using latest technology computer communication also requires a sender, a message and a recipient for a successful computer communication.

Computer uses transmission of data from one computer to another computer or one device to another device for communication. Computer always communicate with the help of some different types of communication devices. And communication device is any machine that assists data transmission. Some examples of communication devices are modems, cables and ports. These devices also need communication software to operate communication devices and this communication software refers to programs that make it possible to transmit data or information to other devices and also can able to receive it. Computer communication can be possible through online and off-line.

Online communication refers to reading, writing and communication via networked computers. Now days it is very essential for both personal and professional uses and we can also say that home and office uses. Online communication technology gives us many ways to contact to the other person only on a mouse click. Because of this technology we can communicate to any person from any corner of the world. We can attend any business meeting from anywhere with the help of video conferencing, which is also a part of online communication. Now day’s video conferencing is very popular in the online communication world and this technology has a very important place in online communication. With the help of video conferencing user not only talk to other person but they can also watch each other face-to-face clearly.

For online communication the most important thing is ‘internet’, this is the core thing which we need to proceed to the way of online communication. These days we can’t think our personal and professional life both without internet. For a successful online communication internet gives us many online services or programs and some of these are: e-mail services, instant messaging, web services, chat groups, newsgroups, internet telephony, file transfer protocol (FTP), web folders, video conferencing, fax machine or computer fax modem etc.

Online communication dates back to late 1960s, when U.S. researchers first developed protocols that allowed the sending and receiving of messages via computer (Hafner & Lyon, 1996). The ARPANET, launched in 1969 by a handful of research scientists, eventually evolved into the Internet, bringing together some 200 million people around the world at the turn of the millennium.

Online communication first became possible in educational realms in the 1980s, following the development and spread of personal computers. The background on online communication in language teaching and research can be divided into two distinct periods, marked by the introduction of computer-mediated communication in education in the mid-1980s and the emergence of the World Wide Web in the mid-1990s.

Computer-mediated communication (CMC) is defined as any communicative transaction that occurs through the use of two or more networked computers. While the term has traditionally referred to those communications that occur via computer-mediated formats (e.g., instant messaging, email, chat rooms), it has also been applied to other forms of text-based interaction such as text messaging. Research on CMC focuses largely on the social effects of different computer-supported communication technologies. Many recent studies involve Internet-based social networking supported by social software.

Off-Line communication is a computer network, or simply a network, which is a collection of computers and other hardware interconnected by communication channels that allow sharing of resources and information. Where at least one process in one device is able to send/receive data to/from at least one process residing in a remote device, then the two devices are said to be in a network. A network is a group of devices connected to each other. Networks may be classified into a wide variety of characteristics: the medium used to transport the data, communication protocol used, scale, topology, benefit, and organizational scope.

Communication protocols define the rules and data formats for exchanging information in a computer network, and provide the basis for network programming. Well-known communications protocols include two Ethernet, hardware and link layer standard that is ubiquitous in local area networks, and the Internet protocol suite, which defines a set of protocols for internetworking, i.e. for data communication between multiple networks, as well as host-to-host data transfer, and application-specific data transmission formats.

Computer networking is sometimes considered a sub-discipline of electrical engineering, telecommunications, computer science, information technology or computer engineering, since it relies upon the theoretical and practical application of these disciplines.

Computer Communication Uses: Wireless Messaging Services

Wireless messaging services is a set of specifications for mobile instant messaging and presence services. It is intended to be a standard for cellphones and mobile devices to use these services across platforms.

Wireless messaging (sometimes called "text messaging" or "texting") is sending short text messages between cell phones, pagers or other handheld devices. Messages are sent through SMS (short message service). Users can also send text messages from a computer to a handheld device. Web texting, as it's called, is made possible by Web sites called SMS gateways.

Many wireless phones now include mobile instant messaging capabilities designed to hook into messaging services using IMPS on a carrier's network, formerly known as the Wireless Village protocol. Those phones implement it as an IM icon on the phone, which is typically renamed and customized by the cellphone carrier or removed completely if not supported at the network level.

As we all know wireless messaging is the transmission of text or data from one device to another, via a wireless network. There are four main forms of wireless messaging:

Short Messaging Services (SMS):

SMS, short for short messaging service, is the dominant form of wireless messaging. SMS messaging is available on most 2G networks and all 3G networks. With SMS, subscribers can send short text messages (usually no more than 160 characters) that are immediately delivered to and from wireless handsets. SMS messaging is particularly popular in Europe and Asia.

Multimedia Messaging Services (MMS):

One of the most recent developments in wireless messaging is known as multimedia messaging service (MMS). MMS is an advanced version of SMS that allows users to enhance their messages by incorporating sound, images, and other rich content, transforming it into a personalized audio and visual message. With MMS, it is not only possible to send your multimedia messages from one phone to another, but also from phone to email, and vice versa. This feature dramatically increases the possibilities of mobile communication, both for private and corporate use. Multimedia Messaging Service has already become a hit in Japan, where J-Phone’s popular sha-mail service claims more than six million subscribers to its picture messaging service.

Mobile Instant Messaging (Mobile IM):

Mobile instant messaging promises to extend desktop instant messaging to wireless devices. The current generation of mobile IM technology is not very sophisticated, due mostly to interoperability issues. But this should change soon. Ericsson, Nokia, Motorola and other companies are the prime movers behind the "Wireless Village" group and its parent, the "Open Mobile Alliance", which are working to establish a set of specifications for interoperability of mobile Instant Messaging services.

Wireless E-mail:

Wireless email is the ability to send and receive email over wireless devices. As 2.5G and 3G networks give users "always on" access to their email (similar to Blackberry devices today), we expect wireless email to become increasingly popular.

Computer Communication Uses: Wireless Internet Access Point

In computer networking and communication, a wireless internet access point (AP) is a device that allows wireless connection to internet in public location and we can also say that these access points allows wireless devices to connect to a wired network using Wi-Fi, or related standards. The access point usually connects to a router (via a wired network) if it’s a standalone device, or is part of a router itself.

Access points usually used in home or small business networks are generally small, dedicated hardware devices featuring a built-in network adapter, antenna, and radio transmitter. Access points support Wi-Fi wireless communication standards.

Although very small WLANs can function without access points in so-called "ad hoc" or peer-to-peer mode, access points support "infrastructure" mode. This mode bridges WLANs with a wired Ethernet LAN and also scales the network to support more clients. Older and base model access points allowed a maximum of only 10 or 20 clients; many newer access points support up to 255 clients.

There are two types of wireless access point and these are as follows:

Hot Spots:

A hotspot, also commonly called a Wi-Fi hotspot, is a small area in which one can get connection to the Internet or a LAN without wires, through Wi-Fi. Wi-Fi is a wireless technology that allows LANs to be set up without wires between devices. So to have a hotspot, you only need to have a wireless router connected to a broadband Internet line. The router will generate the Wi-Fi signals in a sphere and any Wi-Fi-enabled computer or device in that sphere, which is finally the region of the hotspot, can connect while being inside it.

Hotspots can be found in offices, campuses, cafes, public areas, and even at home. Once you have a wireless router connected to your broadband Internet line, you have a hotspot. The closer you are to the source (router), the better the connection is. Once you are out of the hotspot, delimited by the Wi-Fi network reach, you are disconnected. This is one limitation of Wi-Fi – it has a limited range or about 100 feet at most. This range also depends on the strength of the router signals. Wi-Fi can penetrate concrete walls and other structures, but the signal strength definitely decreases.

3G Network:

3G, short for third Generation, is the 3rd generation of mobile telecommunications technology. Also called Tri-Band 3G. 3G telecommunication networks support services that provide an information transfer rate of at least 200 kbit/s. However, many services advertised as 3G provide higher speed than the minimum technical requirements for a 3G service. Recent 3G releases often denoted 3.5G and 3.75G also provide mobile broadband access of several Mbit/s to smartphones and mobile modems in laptop computers.

This is a set of standards used for mobile devices and mobile telecommunication services and networks that comply with the International Mobile Telecommunications-2000 (IMT-2000) specifications by the International Telecommunication Union. 3G finds application in wireless voice telephony, mobile Internet access, fixed wireless Internet access, video calls and mobile TV.

Computer Communication Uses: Collaboration

In general term collaboration is working together to achieve a goal. It is a recursive process where two or more people or organizations work together to realized shared goals. It provides a mean to collaborate or work online with other users connected to a server. With Microsoft office, users can conduct online meetings, which allow users to share documents. Companies use document management system to make collaboration possible among employees.

It is also a document management system to make collaboration possible among employees. It provides for storage and management of a company’s documents such as spreadsheets and presentations.

Computer Communication Uses: Groupware

Groupware is software that helps groups of people work together on projects and share information over a network. It includes network hardware and software that enable group members to communicate, manage projects, schedule meetings and make group meetings.

Groupware group scheduling in which a group calendar tracks the schedule of multiple users and helps coordinate appointments and meeting times. It can allow both geographically dispersed team members and a company's on-site workers to collaborate with each other through the use of computer networking technologies (i.e., via the Internet or over an internal network/intranet). As such, groupware is especially important for remote workers and professionals on the go, since they can collaborate with other team members virtually.

Some common features provided in groupware solutions include:

A centralized repository for documents and files that users can access and save to.

Document version management and change management.

Shared calendars and task management.

Web conferencing, instant messaging, message boards, and/or whiteboards.

Computer Communication Uses: Voice Mail

Voice-mail (also known as voicemail, voice message or voice bank) is a computer based system that allows users and subscribers to exchange personal voice messages; to select and deliver voice information; and to process transactions relating to individuals, organizations, products and services, using an ordinary telephone. The term is also used more broadly to denote any system of conveying a stored telecommunications voice messages, including using an answering machine. Most cell phone services offer voice-mail as a basic feature, many corporate PBXs include versatile internal voice-messaging services and *98 Vertical service code subscription is available to most individual and small business land line subscribers.

Voice mail works much like an answering machine; a computer in a voice mail system converts an analog voice message into digital form. Once digitized the message is stored in voice mailbox. A voice mailbox is a storage location on a hard disk in voice mail system.

Networks

A network is a collection of computer and devices connected via communications devices and transmission media. It is also a series of points or nodes interconnected by communication paths. Networks can interconnect with other networks and contain sub-networks. A network allows sharing of resources and information, where at least one process in one device is able to send/receive data to/from at least one process residing in a remote device, then the two devices are said to be in a network. It may be classified into a wide variety of characteristics: the medium used to transport the data, communication protocol used, scale, topology and organizational scope.

Communication protocols define the rules and data formats for exchanging information in a computer network, and provide the basis for network programming. Well-known communications protocols include two "Ethernet", hardware and link layer standard that is ubiquitous in "local area networks" and the "Internet protocol suite", which defines a set of protocols for internetworking, i.e. for data communication between multiple networks, as well as host-to-host data transfer, and application-specific data transmission formats.

Computer networking is sometimes considered a sub-discipline of electrical engineering, telecommunications, computer science, information technology or computer engineering, since it relies upon the theoretical and practical application of these disciplines. There are some important terms which define computer networks and networking, and these are as follows:

Local Area Network (LAN):

A local area network (LAN) supplies networking capability to a group of computers in close proximity to each other such as in an office building, a school, or a home. It is useful for sharing resources like files, printers, games or other applications. A LAN in turn often connects to other LANs, and to the Internet or other WAN.

Most local area networks are built with relatively inexpensive hardware such as Ethernet cables, network adapters, and hubs. Wireless LAN and other more advanced LAN hardware options also exist.

Specialized operating system software may be used to configure a local area network. For example, most flavors of Microsoft Windows provide a software package called "Internet Connection Sharing (ICS) that supports controlled access to LAN resources.

Wireless Local Area Network (WLAN):

A wireless local area network (WLAN) links two or more devices using some wireless distribution method (typically spread-spectrum or OFDM radio), and usually providing a connection through an access point to the wider Internet. This gives users the mobility to move around within a local coverage area and still be connected to the network. Most modern WLANs are based on "IEEE 802.11" standards, marketed under the Wi-Fi brand name.

Wireless LANs have become popular in the home due to ease of installation, and in commercial complexes offering wireless access to their customers; often for free. Large wireless network projects are being put up in many major cities: New York City, for instance, has begun a pilot program to provide city workers in all five boroughs of the city with wireless Internet access.

Metropolitan Area Network (MAN):

A metropolitan area network (MAN) is a network that interconnects users with computer resources in a geographic area or region larger than that covered by even a large local area network (LAN) but smaller than the area covered by a wide area network (WAN). The term is applied to the interconnection of networks in a city into a single larger network (which may then also offer efficient connection to a wide area network). It is also used to mean the interconnection of several local area networks by bridging them with backbone lines. The latter usage is also sometimes referred to as a campus network.

Examples of metropolitan area networks of various sizes can be found in the metropolitan areas of London, England; Lodz, Poland; and Geneva, Switzerland. Large universities also sometimes use the term to describe their networks. A recent trend is the installation of wireless MANs.

Wide Area Network (WAN):

A wide area network (WAN) is a geographically dispersed telecommunications network. The term distinguishes a broader telecommunication structure from a local area network (LAN). A wide area network may be privately owned or rented, but the term usually connotes the inclusion of public (shared user) networks. An intermediate form of network in terms of geography is a metropolitan area network (MAN).

When networks connect to form a bigger network (a bigger WAN), the resulting network is called an internetwork, which is generically abbreviated to ‘an internet’. Now when all WANs in the world connect forming a global internet, we call it The Internet, which everyone knows! That’s why the Internet is always written with a capital I. It is the biggest WAN we have.

Bus Network:

A bus network is an arrangement in a local area network (LAN) in which each node (workstation or other device) is connected to a main cable or link called the bus. The illustration shows a bus network with five nodes. Each node is shown as a sphere, the bus appears as a heavy horizontal line, and connections to the bus appear as vertical lines.

Bus Network

A bus network is simple and reliable. If one node fails to operate, all the rest can still communicate with each other. For a major disruption to take place, the bus itself must be broken somewhere. Bus networks are easy to expand. Additional nodes can be added anywhere along the bus.

There are several limitations to the bus network topology. The length of the bus is limited by cable loss. A bus network may not work well if the nodes are located at scattered points that do not lie near a common line. In situations like this, a ring network, mesh network, or star network may prove more flexible and more cost effective.

Ring Network:

A ring network is a local area network (LAN) in which the nodes (workstations or other devices) are connected in a closed loop configuration. Adjacent pairs of nodes are directly connected. Other pairs of nodes are indirectly connected, the data passing through one or more intermediate nodes.

The illustration shows a ring network with five nodes. Each node is shown as a sphere, and connections are shown as straight lines. The connections can consist of wired or wireless links.

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The ring topology may prove optimum when system requirements are modest and workstations are at scattered points. If the workstations are reasonably close to the vertices of a convex polygon (such as the pentagon shown in the illustration), the cost can be lower than that of any other topology when cable routes are chosen to minimize the total length of cable needed.

Star Network:

A star network is a local area network (LAN) in which all nodes (workstations or other devices) are directly connected to a common central computer. Every workstation is indirectly connected to every other through the central computer. In some star networks, the central computer can also operate as a workstation.

The illustration shows a star network with five workstations (or six, if the central computer acts as a workstation). Each workstation is shown as a sphere, the central computer is shown as a larger sphere, and connections are shown as straight lines. The connections can be wired or wireless links.

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The star network topology works well when workstations are at scattered points. It is easy to add or remove workstations.

If the workstations are reasonably close to the vertices of a convex polygon and the system requirements are modest, the ring network topology may serve the intended purpose at lower cost than the star network topology. If the workstations lie nearly along a straight line, the bus network topology may be best.

In a star network, a cable failure will isolate the workstation that it links to the central computer, but only that workstation will be isolated. All the other workstations will continue to function normally, except that they will not be able to communicate with the isolated workstation. If any workstation goes down, none of the other workstations will be affected. But if the central computer goes down, the entire network will suffer degraded performance or complete failure. 

Intranet:

Intranet is the generic term for a collection of private computer networks within an organization. An intranet uses network technologies as a tool to facilitate communication between people or work groups to improve the data sharing capability and overall knowledge base of an organization's employees.

Intranets utilize standard network hardware and software technologies like Ethernet, WI-Fi, TCP/IP, Web browsers and Web servers. An organization's intranet typically includes Internet access but is firewalled so that its computers cannot be reached directly from the outside.

A common extension to intranets, called extranets, opens this firewall to provide controlled access to outsiders.

Many schools and non-profit groups have deployed them, but an intranet is still seen primarily as a corporate productivity tool. A simple intranet consists of an internal email system and perhaps a message board service. More sophisticated intranets include Web sites and databases containing company news, forms, and personnel information. Besides email and groupware applications, an intranet generally incorporates internal Web sites, documents, and/or databases.

The business value of intranet solutions is generally accepted in larger corporations, but their worth has proven very difficult to quantify in terms of time saved or return on investment.

These all networks are need some special type of architecture for establishment and work called network architecture. It is basically the design of computers, devices and media in a network. Some important and popular types of network architecture are: Client/Server Network, Peer-to-Peer Network and Internet Peer-to-Peer Network.

Client/Server Network Architecture

Client/server describes the relationship between two computer programs in which one program, the client, makes a service request from another program, the server, which fulfills the request. Although the client/server idea can be used by programs within a single computer, it is a more important idea in a network. In a network, the client/server model provides a convenient way to interconnect programs that are distributed efficiently across different locations. Computer transactions using the client/server model are very common. For example, to check your bank account from your computer, a client program in your computer forwards your request to a server program at the bank. That program may in turn forward the request to its own client program that sends a request to a database server at another bank computer to retrieve your account balance. The balance is returned back to the bank data client, which in turn serves it back to the client in your personal computer, which displays the information for you.

The client/server model has become one of the central ideas of network computing. Most business applications being written today use the client/server model. So does the Internet's main program, TCP/IP. In marketing, the term has been used to distinguish distributed computing by smaller dispersed computers from the "monolithic" centralized computing of mainframe computers. But this distinction has largely disappeared as mainframes and their applications have also turned to the client/server model and become part of network computing.

In the usual client/server model, one server, sometimes called a daemon, is activated and awaits client requests. Typically, multiple client programs share the services of a common server program. Both client programs and server programs are often part of a larger program or application. Relative to the Internet, your Web browser is a client program that requests services (the sending of Web pages or files) from a Web server (which technically is called a Hypertext Transport Protocol or HTTP server) in another computer somewhere on the Internet. Similarly, your computer with TCP/IP installed allows you to make client requests for files from File Transfer Protocol (FTP) servers in other computers on the Internet.

Peer-to-Peer Network Architecture

Peer to peer is an approach to computer networking where all computers share equivalent responsibility for processing data. Peer-to-peer networking (also known simply as peer networking) differs from client-server networking, where certain devices have responsibility for providing or "serving" data and other devices consume or otherwise act as "clients" of those servers.

Peer to peer networking is common on small local area network (LANs), particularly home networks. Both wired and wireless home networks can be configured as peer to peer environments. Computers in a peer to peer network run the same networking protocols and software. Peer networks are also often situated physically near to each other, typically in homes, small businesses or schools. Some peer networks, however, utilize the Internet and are geographically dispersed worldwide.

Home networks that utilize broadband routers are hybrid peer to peer and client-server environments. The router provides centralized Internet connection sharing, but file, printer and other resource sharing is managed directly between the local computers involved.

Internet Peer-to-Peer Network Architecture

On the Internet, peer-to-peer (referred to as P2P) is a type of transient Internet network that allows a group of computer users with the same networking program to connect with each other and directly access files from one another's hard drives. "Napster" and Gnutella are examples of this kind of peer-to-peer software. Major producers of content, including record companies, have shown their concern about what they consider illegal sharing of copyrighted content by suing some P2P users.

Meanwhile, corporations are looking at the advantages of using P2P as a way for employees to share files without the expense involved in maintaining a centralized server and as a way for businesses to exchange information with each other directly.

Communication Software

Communication software is an application or program designed to pass information from one system to another. It is some special types of programs that help users establish connection to Internet, other network, or another computer. Such software provides remote access to systems and transmits files in a multitude of formats between computers. Communication software forms a part of communication systems with software components classified according to functions within the open systems Interconnection Model (OSI Model). The best defined examples of communication software are file transfer protocol (FTP), messaging software and email.

The concept of emailing can be traced back to the early 1960s as a way of communication for multiple users of time sharing mainframe computers. In 1970, text chat functionality followed emailing and appeared on bulletin board systems and multiuser computer systems. In the 1980s, the terminal emulator, a piece of software to log into mainframes and access email, was introduced. The first decentralized chat system was the Bitnet Relay of 1985. Minitel was yet another well-known chat system introduced at the same time. The CU-SeeMe chat system was the first equipped with a video camera.

Instant messaging, with buddy list and idea an online presence, was introduced in 1996. More recently Voice over Internet Protocol (VoIP) is on the short list of popular communication software. VoIP allows users to make phone calls through the Internet at a convenient cost.

Communication Devices

A communication device is piece of equipment or hardware design to move information or data from one place to another, in other words, allowing one computer device to communicate with another. There are many examples of communication devices and we will look at a few below.

Network interface card (NIC) or Network connector

Computers on a network need to be able to communicate with the server and with the other computers. In order to do this, a network interface card (NIC) is required or a built-in network chip is included on the motherboard, such as in the opposite of the laptop.

The hardware handles all the physical network signals. The NIC allows data to be communicated to and from a networked computer. Network interface cards provide a dedicated, full-time connection to a network. Most home and portable computers connect to the Internet through as-needed dial-up connection. 

Wi-Fi Cards

When you are using your computer on a wireless network, you need to be able to send data to and receive data from the server and other computers on the networks. This may be done by a built-in Wi-Fi in your laptop or mobile device connected to a local network.

Wi-Fi is the standard way computers connect to wireless networks. Nearly all computers now have built-in Wi-Fi cards that allow users to search for and connect to wireless routers. Many mobile devices, video game systems, and other standalone devices also include Wi-Fi capability, enabling them to connect to wireless networks as well. These devices may be able to connect to the Internet using a Wi-Fi signal. However, it is important to understand that the Wi-Fi connection only exists between the device and the router. Most routers are connected to a DSL or cable modem, which provides Internet access to all connected devices.

Router

In packet-switched networks such as the Internet, a router is a device or, in some cases, software in a computer, that determines the next network point to which a packet should be forwarded toward its destination. 

The router is connected to at least two networks and decides which way to send each information packet based on its current understanding of the state of the networks it is connected to. A router is located at any gateway (where one network meets another), including each point-of-presence on the Internet. A router is often included as part of a network switch.

A router may create or maintain a table of the available routes and their conditions and use this information along with distance and cost algorithms to determine the best route for a given packet. Typically, a packet may travel through a number of network points with routers before arriving at its destination. Routing is a function associated with the Network layer (layer3) in the standard model of network programming, the Open Systems Interconnection (OSI) model. A layer-3 switch is a switch that can perform routing functions.

Modem

Traditional modems used on dialup networks convert data between the analog form used on telephone lines and the digital form used on computers. Standard dial-up network modems transmit data at a maximum rate of 56,000 bits per second (56 Kbps). However, inherent limitations of the public telephone network limit modem data rates to 33.6 Kbps or lower in practice.

"Broadband modems" that are part of high-speed Internet services use more advanced signaling techniques to achieve dramatically higher network speeds than traditional modems. Broadband modems are sometimes called "digital modems" and those used for traditional dial-up networking, "analog modems." Cellular modems are a type of digital modem that establishes Internet connectivity between a mobile device and a cell phone network.

Communication Channels

Communication channels are simply a medium through which a message is transmitted to its intended audience, such as prints media and broadcast (electronic) media. In telecommunication and computer networking, communication channels have an important role to transmit information and data. There are two most popular and effective types of communication channels, one is "Bandwidth" and another is "Transmission Media".

Bandwidth

In computer networks, bandwidth is often used as a synonym for data transfer rate - the amount of data that can be carried from one point to another in a given time period (usually a second). This kind of bandwidth is usually expressed in bits (of data) per second (bps). Occasionally, it's expressed as bytes per second (Bps). A modem that works at 57,600 bps hastwice the bandwidth of a modem that works at 28,800 bps. In general, a link with a high bandwidth is one that may be able to carry enough information to sustain the succession of images in a video presentation.

It should be remembered that a real communications path usually consists of a succession of links, each with its own bandwidth. If one of these is much slower than the rest, it is said to be a bandwidth bottleneck.

In electronic communication, bandwidth is the width of the range (or band) of frequencies that an electronic signal uses on a given transmission medium. In this usage, bandwidth is expressed in terms of the difference between the highest-frequency signal component and the lowest-frequency signal component. Since the frequency of a signal is measured in hertz (the number of cycles of change per second), a given bandwidth is the difference in hertz between the highest frequency the signal uses and the lowest frequency it uses. A typical voice signal has a bandwidth of approximately three kilohertz (3 kHz); an analog television (TV) broadcast video signal has a bandwidth of six megahertz (6 MHz) -- some 2,000 times as wide as the voice signal.

Transmission Media

Transmission media is a pathway through which data are transmitted in Communication Networks. We use different types of cables or waves to transmit data.

There are two types of transmission media namely: bound transmission media and unbound transmission media exist in the world of communication Networks.

Bound transmission media are the cables that are tangible or have physical existence and are limited by the physical geography. Popular bound transmission media in use are twisted pair cable, co-axial cable and fiber optical cable. These are also called "physical transmission media".

Here we are going to discuss some important and popular types of physical transmission media:

Twisted Pair Cable:

A type of cable that consists of two independently insulated wires twisted around one another. The use of two wires twisted together helps to reduce crosstalk and electromagnetic induction. While twisted-pair cable is used by older telephone networks and is the least expensive type of local-area network (LAN) cable, most networks contain some twisted-pair cabling at some point along the network. 

Twisted pair is now frequently installed with two pairs to the home, with the extra pair making it possible for you to add another line (perhaps for modem use) when you need it. Twisted pair comes with each pair uniquely color coded when it is packaged in multiple pairs. Different uses such as analog, digital, and Ethernet require different pair multiples.

Co-Axial Cable:

Coaxial cable is the kind of copper cable used by cable TV companies between the community antenna and user homes and businesses. Coaxial cable is sometimes used by telephone companies from their central office to the telephone poles near users. It is also widely installed for use in business and corporation Ethernet and other types of local area network.

Coaxial cable is called "coaxial" because it includes one physical channel that carries the signal surrounded (after a layer of insulation) by another concentric physical channel, both running along the same axis. The outer channel serves as a ground. Many of these cables or pairs of coaxial tubes can be placed in a single outer sheathing and, with repeaters, can carry information for a great distance.

Fiber Optical Cable:

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Optical fiber (or "fiber optic") refers to the medium and the technology associated with the transmission of information as light pulses along a glass or plastic strand or fiber. Optical fiber carries much more information than conventional copper wire and is in general not subject to electromagnetic interference and the need to retransmit signals. Most telephone company long-distance lines are now made of optical fiber. Transmission over an optical fiber cable requires repeaters at distance intervals. The glass fiber requires more protection within an outer cable than copper. For these reasons and because the installation of any new cabling is labor-intensive, few communities have installed optical fiber cables from the phone company's branch office to local customers (known as local loops). A type of fiber known as single mode fiber is used for longer distances; multimode fiber is used for shorter distances.

Unbound transmission media are the ways of transmitting data without using any cables. These media are not bounded by physical geography. Microwave, Radio wave, Infra red are some of popular unbound transmission media. This is also called "wireless transmission media".

Here we are going to discuss some important and popular types of wireless transmission media:

Broadcast Radio and Cellular Radio:

Radio broadcasting is a one-way wireless transmission over radio waves intended to reach a wide audience. Stations can be linked in radio networks to broadcast a common radio format, either in broadcast syndication or simulcast or both. Audio broadcasting also can be done via cable radio, local wire television networks, satellite radio, and internet radio via streaming media on the Internet. The signal types can be either analog audio or digital audio. It is usually used over long distances such as between cities. This type of radio transmission requires transmitter and receiver.

A cellular radio network or mobile network is a radio network distributed over land areas called cells, each served by at least one fixed-location transceiver, known as a cell site or base station. In a cellular network, each cell uses a different set of frequencies from neighboring cells, to avoid interference and provide guaranteed bandwidth within each cell.

Microwave Station:

Microwave transmission or station refers to the technology of transmitting information or energy by the use of radio waves whose wavelengths are conveniently measured in small numbers of centimeter; these are called microwaves. This part of the radio spectrum ranges across frequencies of roughly 1.0 gigahertz (GHz) to 30 GHz. These correspond to wavelengths from 30 centimeters down to 1.0 cm.

Microwaves are widely used for point-to-point communications because their small wavelength allows conveniently-sized antennas to direct them in narrow beams, which can be pointed directly at the receiving antenna. This allows nearby microwave equipment to use the same frequencies without interfering with each other, as lower frequency radio waves do. Another advantage is that the high frequency of microwaves gives the microwave band a very large information-carrying capacity; the microwave band has a bandwidth 30 times that of all the rest of the radio spectrum below it. A disadvantage is that microwaves are limited to line of sight propagation; they cannot pass around hills or mountains as lower frequency radio waves can.

Microwave radio transmission is commonly used in point-to-point communication systems on the surface of the Earth, in satellite communications, and in deep space radio communications. Other parts of the microwave radio band are used for radars, radio navigation systems, sensor systems, and radio astronomy.

Communications Satellite:

A communications satellite or comsat is an artificial satellite sent to space for the purpose of telecommunications. Modern communications satellites use a variety of orbits including geostationary orbits, Molniya orbits, elliptical orbits and low (polar and non-polar Earth orbits).

For fixed (point-to-point) services, communications satellites provide a microwave radio relay technology complementary to that of communication cables. They are also used for mobile applications such as communications to ships, vehicles, planes and hand-held terminals, and for TV and radio broadcasting.

Communications satellites are commonly used for mobile phone signals, weather tracking, or broadcasting television programs.