TCS - Module 5

INTRODUCTION TO TELECOMMUNICATION I

History of telecommunications, basic components of telecommunications, benefits of telecommunications, Impact on individual and global society, Effect on personal, educational and professional growth, introduction to analog and digital transmissions, concepts of multiple access techniques, concepts and brief history of cellular systems (what are MS, BTS, MSC, HLR, VLR and etc), introduction to networking and the internet, intro to OSI Network Model and TCP/IP protocol suits, some benefits of networking, LAN topologies and basic components and functions of LAN connection devices (router, switches, Hub etc).

INTRODUCTION

The purpose of this course is to provide an introduction to telecommunication. This module is the first core course for telecommunications science students in the department, and it’s compulsory for all students in the faculty.

PLANNING A CAREER IN TELECOMMUNICATION

Telecommunication is a promising and marketable field, those who choose this field will require some software and hardware skills and these may includes at least two of the following:

• Unix/Linux with C or C++
• Windows XP/Vista/Windows 7 Operating systems
• Programming languages such as VB, C++ or Java

Communication is a vast field and therefore, it would be difficult to gain expertise in the entire field. However, one needs to have very good understanding of the basic of telecommunication systems and communication protocols and then focus on specialization. Some of the specialization areas include:

• Wireless Communications
• TCP/IP Protocol
• Multiservice networks
• Multimedia communication over IP
• Telecommunication Network Management
• Optical Communication
• Terrestrial radio communication
• Satellite communication

History of Telecommunication

'Telecommunication' is a Greek word meaning 'communication at distance' through signals of varied nature coming from a transmitter to a receiver. In order to achieve effective communication, the choice of a proper mean of transport for the signal has played (and still plays) a fundamental role .

In ancient times, the most common way of producing a signal would be through light (fires) and sound (drums and horns). However, those kinds of communications were insecure and certainly left room to improvement as they did not permit message encryption nor a fast transmission of information on a large scale.

The true 'jump' in terms of quality came with the advent of electricity. Electromagnetic energy, in fact, is able to transport information in an extremely fast way (ideally to the speed of light), in a way that previously had no equals in terms of costs reliability. Therefore, we may say that the starting point of all modern telecommunications was the invention of the electric cell by Alessandro Volta (1800).

It was shortly thereafter that the first experiments on more advanced communication system begun . In 1809, Thomas S. Sommering proposed a telegraphic system composed of a battery, 35 wires (one for each letter and number) and a group of sensors made of gold, which were submerged in a water tank: when a signal was passing from one of those wires, electrical current would split water molecules, and small oxygen bubbles would be visible near that sensor . Many other experiments were soon to follow: Wheatstone, Weber and Karl Friedrich Gauss tried to further develop Sommering's idea in a product that could be mass-distributed, but their efforts were without success.

For the next step we would have to wait until 1843, the year in which Samuel Morse proposed a way to assign each letter and number to a ternary code (point, line, and space). This way turned out to be extremely convenient and more affordable than Sommering's idea, especially in terms of reduced circuitry (you wouldn't need anymore a wire for each symbol). Meanwhile, technology became advanced enough to find a way to convert those signals in audible (or sometimes graphic) signals. The combination of these two factors quickly determined the success of Morse's symbol code, which we can still find used today.

The system was further developed and improved in the following years by Hughes, Baudot, and Gray (1879), who theorized other possible codes (Gray's code has still applications today in the ICT industry and in barcodes technology).

However, the telegraph could still be used just by trained personal and in certain buildings like offices, so it could only be used by a limited amount of people. Research of the time therefore took another direction and aimed at producing a machine that could transmit sounds, rather than just signals. The first big step in this direction was the invention of transducers which could transform an acoustic signal into an electric one and vice versa (microphone and receiver) with acceptable information loss, in 1850.

Seven years later, Antonio Meucci and Graham Bell independently managed to build a prototype of an early telephone ('sound at distance') machine. Since Meucci didn't have the money to patent his invention (the cost was $250 at the time), Bell managed to register it first.

Both with telegraphs and telephones, the need for a distributed and reliable communication network soon became evident. Routing issues were first solved by means of human operators and circuit commutation: the PSTN (Public Switched Telephone Network) was born. However, this system didn't guarantee the privacy and secrecy of conversations, and efforts towards the development of an automatic circuit commutation were made.

In 1899, Almon Strowger invented an electro-mechanic device simply known as 'selector', which was directed by the electrical signals coming from the calling telephone device, achieved through selection based on geographical prefixes.

Many other innovations were soon to come:

• In 1985, Guglielmo Marconi invented the 'wireless telegraph' (radio);
• In 1920, valve amplifiers made their first appearance;
• In 1923, the television was invented;
• In 1947, the invention of transistors gave birth to the field of electronics;
• In 1958, the first integrated circuit was built;
• In 1969, the first microprocessor was invented.

With the last step, electronics becomes more than ever a fundamental part in the telecommunication world, at first in the transmission, and soon also in the field of circuit commutation.

Moreover, in 1946 the invention of ENIAC (Electronic Numerical Integrator and Computer) starts the era of informatics. Informatics and telecommunications inevitably begun to interact, as it was to be expected: the first made fast data processing possible, while thanks to second the data could then be sent to a distant location.

The development of microelectronics and informatics radically revolutionized techniques both in telecommunication networks and performance requirements for the networks. Starting from 1938, an innovative technology called PCM (Pulse Code Modulation) started to grow more and more popular. This technology could achieve the digital transmission of a voice signal by digitally encoding and decoding, rather than by means of transducers: however, PCM was first used on a large scale only in 1962 in the United States (the so-called 'T1').

During the mid Sixties Paul Baran, a RAND Corporation employee working on communication problems concerning the US Air Force, first gave birth to the concept of 'packet switching network' rather than the conventional idea of circuit commutation network. According to this model, there should be no hierarchy in the nodes of a network, but each node should rather be connected to many others and be able to decide (and, in case of need, modify) the packet routing. Each packet is a bulk of data which consist of two main parts, a 'header' containing routing information and a 'body' containing the actual data.

In this context Vincent Cerf, Bob Kahn and others developed, starting from the 70s, the TCP/IP protocol suite, which made possible communication of computers and heterogeneous machines through a series of physical and logical layers. Packet switching network and TCP/IP were later chosen by the military project ARPANET. The rest of the story is widely known: in 1983, ARPANET became available to universities and research centers, among which NSFNET (National Science Foundation + NET), which finally gave birth to the Internet.

In the latest years, the importance of the Internet has been constantly growing. The high flexibility given by the TCP/IP (Transmission Control Protocol/ Internet Protocol) suite and the ISO/OSI protocols provide a strong foundation on which communication among devices of different kind -- be it a laptop or a cell phone, an iPod or a GPS navigator -- has finally been made simple and easy to achieve

BASIC OF TELECOMMUNICATION SYSTEMS

The primary objective of any telecommunication systems is to facilitate or establish communication between any two or more end devices or points. These end points could be people, PC to PC, PC to printer or a digital camera with a printer. The information or data the devices may like to exchange can be in different forms such as text, graphics, voice or video and is agreed by the parties creating and using the data. The basic principles of all these types of communication are the same. Data communication is the exchange of data between two devices via some transmission medium such as wire cable or through air interface. For data communication to occur, the communicating devices must be part of the communication system made up of combination of hardware (physical equipments) and software (programs). The effectiveness of data communications systems depends on four fundamental characteristics:

1. Delivery. The system must deliver data to the correct destination. Data must be received by the intended device or user and only by that device or user.

2. Accuracy. The system must deliver the data accurately. Data that have been altered in transmission and left uncorrected are unusable.

3. Timeliness. The system must deliver data in a timely manner. Data delivered late are useless. In the case of video and audio, timely delivery means delivering data as they are produced, in the same order that they are produced, and without significant delay. This kind of delivery is called real-time transmission.

4. Jitter. Jitter refers to the variation in the packet arrival time. It is the uneven delay in the delivery of audio or video packets. For example, let us assume that video packets are sent every 3D ms. If some of the packets arrive with 3D-ms delay and others with 4D-ms delay, an uneven quality in the video is the result.

Telecommunication Network Components:

Telecommunication components includes: telecommunication channels, terminals, telecommunication processors, and media, computers, and telecommunication control software.

Telecommunication Channels:

Telecommunications channels are part of a telecommunications network that connects the message source with the message receiver. It includes the physical equipment used to connect one location to another for the purpose of transmitting and receiving information.

Telecommunication Media:

Telecommunications media are the physical media used by telecommunications channels. They include, twisted-pair wire, coaxial cables, fiber optic cables, terrestrial microwave, communications satellite, cellular, and infrared systems.

Coaxial Cable:

A study of copper or aluminum wire wrapped with spacers to insulate and protect it. Groups of coaxial cables may be bundled together in a bigger cable for ease of installation.

Communications Satellites:

Earth satellites placed in stationary orbits above the equator that serve as relay stations for communications signals transmitted from earth stations.

Telecommunications Processors:

Multiplexers, concentrators, communications controllers, and cluster controllers that allow a communications channel to carry simultaneous data transmissions from many terminals. They may also perform error monitoring, diagnostics and correction, modulation-demodulation, data compression, data coding and decoding, message
switching, port contention, and buffer storage.

Telecommunications Software:

Telecommunications software, including network operating systems, telecommunications monitors, web browsers, and middleware, control and support the communications activity in a telecommunications network.

.