6

In the earlier chapters, we saw how computer systems have become an important tool for our day–to–day functions. Online applications as ATMs, automatic complaint registration, railway reservation, etc. have improved our productivity and made our job faster and easier. In the next chapter on ‘the Internet’, we will see that most of the current applications are Internet based and depend heavily upon the communication systems. In this chapter we shall see that the communication systems have undergone gradual changes from the telephone system to video–conferencing. Communication systems are converging to provide next generation applications (Figure 6.1).

Even before computers were invented, there were various modes of communication like postal services, telegraphs and telephones. In the twentieth century, considerable efforts were made to develop reliable and affordable telecommunication systems. Telecommunication systems were developed to effectively use multiple services such as television, radio news broadcasting, etc. along with the telephone.

Telecommunication systems were also used for long distance communication between computers.

A revolution in the computer technology started in the middle of the twentieth century. Today the computer is not just a data processing device, if has become a multipurpose utility tool. The computer is being used, among many other things, for documentation, entertainment and communication.

Communication system is a very general term which means a combination of computers, communication devices, associated networks and required software.

Let’s consider a simple example of sending a picture to a friend using e-mail.

Traditionally the picture could be sent through the postal service. The sender would put the picture in an envelope and post it at the nearest post office. The postal service would then deliver the envelope to the receiver. The receiver could get the picture in two days or in a month or never, and it could even get lost.

Using modern communication system the picture can be sent instantly in the following way.

To send the picture, the sender would use a scanner (Figure 6.2 ) to get its copy on the computer. Then the computer has to be connected to the Internet. The sender would use an Internet application such as e-mail to attach the picture and send it to the receiver’s e-mail address.

The receiver could be located in any part of the world, s/he can receive the copy of the photograph within minutes. S/he would connect to the Internet and login to her/his e-mail account, download the picture into her/his computer system. If needed, a printer can be used to get a copy of the picture.

Similarly any information such as a document, an image or music can be instantly transferred to any part of the world using modern communication systems.

6.1 Components of Communication Systems

In a communication system there are various components which are interconnected through communication devices, networks and communication software. All communication systems have the following five essential components which interact with each other to provide seamless connectivity (Figure 6.3).

6.1.1 Message

The content that has to be such communicated as document, picture, song, etc. It can be in any form such as text, number, image, audio or video.

6.1.2 Sender

The sender can be any device such as a computer, mobile, telephone, video camera, etc. which is used to send the information.

6.1.3 Receiver

The receiver can be any device such as a computer, mobile, telephone, video camera, etc. A device that receives the information.

6.1.4 Transmission medium

It is the connectivity between the sender and receiver, through any medium such as twisted pair cable, fibre optic cable, coaxial cables or radio waves.

6.1.5 Protocol

Protocols are a set of rules that control the communication between the receiver and the sender. The communication software interfaces two connecting devices and controls the flow of data. For successful communication, both the devices must follow a common communication protocol.

6.2 Applications

These are the software or programs designed to fulfill the specific requirement of the user. Eg., Mozilla Browser, Outlook Express, etc.

Internet Service Provider (ISP) : Company that provides Internet services

6.3 Evolution of Communication Systems

The modern communication systems started developing only after the nineteenth century with the development of the electromagnetic telegraph system.

In the telephone system (Figure 6.4), a microphone is used to convert voice signals into electrical signals and transmit the same through a pair of copper wires over a long distance. At the remote end a speaker/earphone is used to convert electric signals back to voice. All the local exchanges are interconnected through Public Switched checked Telephone Network (PSTN) backbone. Over the years, the telecommunication system has also undergone tremendous up gradation. Today, they provide multi-functionality like FAX, SMS, television, Internet, data communication, etc.

Modern PSTN uses high speed backbones with various types of transmission media such as fibre optics and wireless. The major break through in telecommunication system came after the development of following technologies.

1. Pulse Code Modulation: Technology for digitisation of voice/analogue signal into digital signals (Figure 6.5).

2. Multiplexing of multiple low speed signals into a high speed signal.

3. Invention of various transmission media such as wireless, fibre optic cables, etc.

Earlier computers were directly connected to devices such as terminals, printers, monitors, etc. The distance between two devices was also limited within a room or a building. The data transfer was also restricted to sending small text messages and commands.

Long distance data communication was done through low speed point to point connections (Figure 6.7) such as leased lines and dial-up.

With telecom technologies such as ISDN and Broadband, the telephone connection can now be used simultaneously for voice communication as well as data connection (Figure 6.8).

6.4 Convergence of Communication Technologies

Earlier, there were separate networks for voice, video and data communication. These networks did not meet the requirement of next generation integrated multimedia applications such as video conferencing, Net-meeting, etc. which require simultaneous transmission of voice, data and video. Efforts are made to develop integrated solution to support multimedia applications through a single communication system. As more and more tasks are becoming computer dependent, convergence of the technologies has become a necessity.

Objectives of convergence of communication technologies are –

(i) to provide cost effective communication system.

(ii) to make deployment easier and convenient.

(iii) to make optimum use of existing infrastructure to support multimedia applications.

(iv) to develop high availability and high speed network to support online interactive application such as telemedicine, video-conferencing.

(v) to provide inexpensive unified services.

The emergence of global competition is also driving the ISPs to provide unified services like email, talk, chat, web search, etc. from a single platform, using the existing infrastructure.The tele-communication service providers started giving additional services like Internet access, broadcast services like video-on-demand, IPTV, etc. Customers are also opting for such ISPs who can provide single point solution for all required services.

Data networks are now extensively used for telecommunication services such as Voice over Internet Protocol (VoIP) and broadcasting services like IPTV. Even the cable TV operators are providing Internet connection along with cable connection. Today mobile phones are equipped with Internet and FM radio services.

The equipment manufacturers are developing plug and play devices that can be connected with multiple networks and can be controlled from remote locations.

6.4.1 Developing Uniform Data Representation and Digitisation Technologies

Digitisation of data is the first step in the process of convergence. All types of data whether text, number, image, voice or video, can be represented in the binary form. Digitisation is the process to convert any type of data into binary digits that can be processed by any computing device.

The motivation behind this digitisation is the fact that the computer works on the principle of manipulation of numbers. If any data is in binary form, it can easily be manipulated by the computer. Therefore, efforts are on to develop technologies to digitise various types of data for better storage and transmission. Once digitised, irrespective of the type of data, the same communication system can be used for transmitting.

6.4.2 Convergence of Standards and Protocols

During communication, the message is processed at various stages by several intermediate hardware and software components. It is cost effective and easy to integrate if all the components follow uniform protocols and standards. There are some standards and protocols which have become very popular and have emerged as standards. These standards are followed by industries and manufacturers. Some such protocols are –

1. Internet Protocol (IP) is the most popular protocol to interconnect different networks.

2. Ethernet is most popular standard for Local Area Network.

3. HTTP is most popular protocol to connect web applications.

4. MPEG is compression technology for transmission of video.

The function of Internet Protocol is similar to our postal delivery system but is electronically processed and is very fast.

In the traditional postal system, the message, written in the form of a letter containing receiver’s and sender’s addresses, is dropped in the nearest letter box. Letters collected from all the letter boxes are segregated as per the state/city in the post office. All letters to the same city are bundled and sent through air/train depending upon the distance and availability. At the remote city, the letters are unbundled and sent to the respective local post offices. Finally the letter is delivered to its destination through the local postman.

Similarly in the Internet (Figure 6.9), all messages are sent in the form of packets called IP packets. Each packet is marked with source address and destination address. Like every person is identified with a name and address, each computer connected to the Internet is also identified with a unique address/name termed as IP address/domain name respectively. The computer sends the IP packet directly to the connected IP network. In the Internet the packets are forwarded from one network to other as per the destination address till it reaches the receiver.

Internet Protocol has become very popular as it can withstand and overcome the frequent breakdown of communication links. It was designed to automatically find an alternative path and continue the communication without any break.

Ethernet (Figure 6.10) is another communication protocol which has become very popular for connecting communication devices through various types of transmission media such as copper, wireless and optical fibre. It can support various data transfer rate as 10 Mbps/100 Mbps/1 Gbps/10 Gbps and is very simple to implement. Today all computer peripherals such as printer, scanner, etc. are equipped with Ethernet interface instead of serial/parallel interfaces.

6.4.3 Convergence of Network

Broadband is one simple example of convergence of voice, video and data. Broadband is the latest communication technology using which a user can have simultaneous voice calls, Internet access and cable television over the same telephone line (Figure 6.11). Effort is being made to provide more high bandwidth services through various types of transmission media.

6.4.4 Convergence In Voice Communication

In this age of convergence, voice communication can be done from multiple networks with multiple connecting devices and from multiple locations (Figure 6.12). The mobile phone connected to wireless network can communicate with landline telephone connected to PSTN network as well as with multimedia computer connected with the Internet. Instant messages can be sent from a computer to a mobile phone.

6.4.5 Convergence of Video Communication

Video–conferencing and video–streaming (Figure 6.13 ) are some of the multimedia applications gaining popularity. Video-conferencing was primarily done through point-to-point connection like ISDN, leased line, etc. and required specialised equipment.

Today, thanks to convergence, video-conferencing is done through IP networks and does not require costly video conferencing systems; all that is required is a multimedia system with a camera and associated software.

High quality and reliable video-communication is possible with the development of features like Quality of Service (QoS) and video compression techniques such as MPEG.

Since video traffic requires high bandwidth, it becomes difficult to get acceptable quality when transmitted through low speed PSTN or satellite links. These video signals are therefore compressed and formatted before transmission. Video compression techniques such as MPEG4 can compress video data upto 100 times which can then be transmitted through low speed networks.

Earlier news and movies were telecast through broadcast media using satellite, wireless and cable. The signal quality was noisy and non interactive. Now with technologies like IPTV and video-on-demand, high quality video can be received. IPTV is a broadcast service provided by telecom operators through their PSTN networks. The user can view the video telecast through their traditional TV sets as well as computer systems.

Video-on-demand is another video streaming service where the user has the option to select what s/he wants to watch from among those stored in the media server.

6.4.6 Convergence of Wireless Network

Wireless is one of the fastest growing networks. The demand is growing as more and more users require access to Internet from multiple locations. It is becoming as essential as mobile phones.

Wireless LAN, WiFi and WiMax are few such technologies which provide high speed data communication over wireless networks. Computer systems are designed with built-in wireless interface cards which can connect to any type of wireless networks. In wireless network, computers are connected to the nearest available access point.

The access points are connected to other networks through wired Ethernet connection or broadband connection.

With third generation mobile technology such as GPRS, one can use mobile devices to access multi-service applications like voice communication, Internet and video conferencing.

6.4.7 Convergence of Applications

Web browsers like Internet Explorer, Firefox, etc. are the accepted client applications for Internet access. Most equipment manufacturers are providing web interfaces for management and control of their systems instead of product specific client application.

Most of the applications are developed with web interface so that the application can be accessed from a standard client application supplied as part of the operating system.

Another example of convergence of application is unified messaging system. There are many popular web service providers, for instance Yahoo, MSN and Google, who started with either e-mail or search engines, but are now providing a banquet of messaging services like email, chat, instant messenger, conferencing, file sharing and VoIP.

There are several applications that can replace multiple communication devices such as telephone, fax, answering machine, books, etc, with one multimedia computer. The number of such services and applications are increasing day-by-day. Broadband and Direct-to-Home (DTH) are some communication technologies which allow interactive TV services such as movie-on-demand, Internet access, video conferencing and e-mail, all through a single connection.

In a nutshell, any data that can be digitised can also be communicated through a converged communication system. The distinct division between telecommunication and data communication has faded into one converged communication system. Efforts are on to make more and more services IP enabled and networked.

In the next chapter, we shall discuss various Internet applications used for communication.

6.5 Importance of Standardisation

Standardisation plays an important role in every sphere of our day-to- day life. Standardisation is the process of agreeing on technical specifics of any process or product.

The goals of standardisation are to have compatibility, interoperability, safety, repeatability and quality. In a competitive market, it is very important for industries to maintain the standards to flourish in their trade. There are predefined standards set for the IT industry too. This is to guarantee the interoperability and compatibility between products from different vendors. There are various standardisation organisations worldwide which are primarily engaged in the documentation, research, development, and testing in the field of computer hardware, software and communications to formulate standards. Once a standard is accepted, the vendors can design and develop the product as per the standards.

Some important standardisation organisations in the field of Information Technology are as follows –

• ANSI (American National Standards Institute)
  
• ITU (International Telecommunication Union)
  
• IETF (The Internet Engineering Task Force)
  
• IEEE (Institute of Electrical and Electronic Engineers)
  
• EIA/TIA (Electronic Industry Association/Telecommunication Association)
  
• ISO (International Standards Organisation)
  
• VESA (Video Electronics Standards Association).
  

The Internet Engineering Task Force (IETF) is a large open international community of network designers, operators, vendors, and researchers concerned with the evolution of the Internet architecture and the smooth operation of the Internet. While IEEE is generally concerned with hardware, ANSI has been primarily concerned with software. ANSI has defined standards for a number of programming languages including C, C++, COBOL and FORTRAN. All these organisations collectively provide the framework of the standards which bind IT across the world. They let us work easily across regions, without being bogged down with compatibility issues. For example, IEEE developed a set of network standards to facilitate interoperability among various make and models of network devices.

ITU defines international standards, particularly for communication protocols. It has defined a number of standards, including V.22, V.32, V.34 and V.42 that specify protocols for transmitting data over telephone lines.

EIA/TIA specifies generic telecommunication cabling system which supports multiproduct, multivendor environment. For example, EIA/TIA 568A and 568B standard is for the pin configuration of LAN cable.

Apart from these standardisation organisations, there are region specific associations of manufacturers who also contribute to the development of standards to meet the needs of that particular region.

In India there are few standardisation organisations like BIS (Bureau of Indian Standards), which actively participate in the development of standards in various fields.