Архитектура Аудит Военная наука Иностранные языки Медицина Металлургия Метрология
Образование Политология Производство Психология Стандартизация Технологии


Unit 1. Telecommunications. Basic Concepts



Introduction

These methodical and practical guidelines intended for 2-3-year students are prepared in compliance with the Course syllabus and designed to help the learners develop professional language skills and competences. There will be no attempt to replace the content of themes and topics of the major specialties, but make it easier for future specialists to deal with foreign sources and partners, thus, use the English language in order to enhance their professional growth, to boost career development and always enjoy unlimited worldwide information resources and opportunities.

Much will depend on the students’ ability to work independently. Undoubtedly, there will be numerous textbooks, special teaching aids and recommendations, but real-life up-to-date information will always remain indispensable.

Unfortunately, we have to admit the fact, that the subject material of the present guide is rather limited, narrowed to quite a few topics, related, however, to the basic concepts of telecommunication systems, networks and convergence in telecoms and IT.

 

 

Unit 1. Telecommunications. Basic Concepts

Start-up

1.1 In pairs or small groups, discuss and suggest suitable answers to the following questions:

- What general problems can be solved with the help of computer networks?

- What types of computer networks do you know?

- What are communication protocols designed for?

Text A. Telecommunications (1)

The term “telecommunications” refers to the transmission of information over long distances using the telephone system, radio, TV satellite or computer links. Examples are two people speaking on the phone, a sales department sending a fax to a client or someone reading the teletext pages on TV. But in the modern world, telecommunications mainly means transferring information from one PC to another via modem and phone lines (or fiber-optic cables).

The global telecommunications network is the largest and most complex technical system that man has created. It makes up a substantial part of a country's infrastructure and is vital to the development of the country. Development in the field of telecommunications has been very rapid in recent years. By telecommunications we mean here all processes that render it possible to transfer voice, data and video with the help of some form of electromagnetic system, including optical transfer methods.

This rapid development points to new demands on knowledge and competence for everyone who takes an active part in modern telecommunications. Today the rate of change and innovation in the telecommunications industry is accelerating at a breakneck pace. New telecommunications technology enables companies to interface directly with their customers wherever on the globe they happen to be. The coming convergence of voice, data, and video technologies means that the media, entertainment, computer, and telecommunications organisations are all going to be merging and interoperating their activities. Even something so small as an individual strand of optical fiber today has the capacity to carry million television channels simultaneously. How will telecommunications technology evolve and with what impact in the coming years?

1.2 In text A find synonyms or equivalents for the following words and expressions.

Computer connections; transmission; make it possible; excessive speed; clients; coming closer (about services); occurring at the same time.

 

1.3 Find equivalents for the following Russian words and expressions.

Слияние (организаций); передача информации; стремительное развитие; взаимодействовать с клиентами напрямую.

 

1.4 Due to the new telecommunications technology companies do not need to cooperate with their clients directly (True or False?).

1.5 Find and present to the group information supporting the idea that “The global telecommunication network is vital to the development of the country”.

A two-three minute presentation will be welcomed and result in additional assessment points.

1.6 Read text B and give headings to the paragraphs.

Text D. Что такое телекоммуникация (электросвязь)

Телекоммуникацией принято считать прием и передачу звука, сигнала, текста, знака, письменного изображения по кабельной, проводной, магнитной, оптической, радио- и другим электромагнитным системам.

Система технических средств, с помощью которой осуществляется телекоммуникация, называется сетью телекоммуникаций. Сами же технические средства телекоммуникаций это оборудование и машины, которые используются для обработки, передачи и приема сообщений телекоммуникаций.

Каналы связи. Выделяют три основных разновидности каналов связи:

1) симплексные — то есть допускающие передачу данных только в

одном направлении, (например, в телевизионной и радиовещательной сетях);

2) полудуплексные — то есть когда два узла связи соединены одним

каналом, по которому информация передается попеременно то в одном направлении, то в противоположном (в информационно-справочных и запросно-ответных системах);

3) дуплексные — позволяют передавать данные одновременно в двух

направлениях за счет использования четырехпроводной линии связи (два провода для передачи, два других – для приема данных), или двух полос частот.

По реализации каналы связи делятся на:

беспроводные (радиосвязь);

оптоволоконные;

проводные.

Спутниковые, естественно, относятся к беспроводным, т.е. к радиоканалам.

1.16 Answer these questions:

1) What are the basic parts of a telecommunication system?

2) What are the main types of data transmission media?

3) What are channels of communication and their main functions?

4) Why is the analog telecommunication system being replaced by the digital system?

 

1.17 Match the following words with their Russian equivalents:

1) стационарная (связь) a) fiber-optic

2) цифровая (связь) b) wireless

3) подвижная (связь) c) fixed

4) беспроводная (связь) d) discrete

5) наземный (ретранслятор) e) mobile

6) преобразовывать (сигналы) f) process

7) дискретные (сообщения) g) digital

8) ретранслятор h) convert

9) волоконно-оптическая (связь) i) ground-based

10) обрабатывать (сигнал) j) relay

1.18 Make up a list of terms you can find in the text. Translate them into English and write definitions.

1.19 Prepare a 2-3-minute presentation reflecting the history of modern-day communication technology in Kazakhstan.

Unit 2. Transmission Media

Start-up

What does the efficiency of the transmission medium depend on (discuss with your partner)?

Do you believe that fiber optic is more efficient than copper cable?

Is the word “media” singular or plural? Write the following words in

singular: data, media, criteria, syllabi, phenomena, crises, analyses, theses.

Text A. Transmission Media

Transmission media are the highways and arteries that provide a path for telecommunications devices. There is a general tendency to say that one transmission medium is better than another. In fact, each transmission medium has its place in the design of any communication system. Each has characteristics which will make it the ideal medium to use based on the particular set of circumstances. It is important to recognize the advantages of each and develop a system accordingly. Factors to consider when choosing the transmission media include: cost, ease of installation and maintenance, availability, and most important, efficiency of transmission. It is important to recognize the advantages of each and develop a system accordingly.

Transmission efficiency is generally viewed as the amount of signal degradation created by the use of a particular transmission medium. The transmission medium presents a "barrier" to the communication signal. The "barrier" can be measured by many different factors. However, one common question is asked about all communication media. How far will the communication signal energy travel before it becomes too weak (or distorted) to be considered unstable? There is equipment available to extend the distance for transmitting a signal, but that adds to the overall cost and complexity of deployment.

 

2.1 Match the words in column A with their synonyms in column B:

A B

Circumstances difficulty

Degradation conditions

Barrier placement

Distorted attenuation

Deployment obstacle

Complexity weakened

2.2 Translate this sentence into Russian:

Transmission efficiency is generally viewed as the amount of signal degradation created by the use of a particular transmission medium.

2.3 Answer the following questions:

1) What factors should be considered when choosing the transmission media?

2) Why is a transmission medium called a “barrier” to the communication signal?

3) What common question is usually asked about all communication media?

4) How can you explain the term “transmission efficiency”?

Text B. Transmission lines

The most common types of transmission media used today are: Copper Wire; Fiber Optics; Radio Frequency (Wireless); Free Space Optics.

Many engineers will argue that one transmission medium is the best, or better than some of the others. The reader should keep in mind that each medium has advantages and disadvantages. Which medium is best depends upon the purpose of the communications system and the desired end results. In fact, most systems are a hybrid. That is, two or more media are combined to effect the most efficient communication network infrastructure. There are many traffic signal systems that combine a twisted copper pair infrastructure with wireless links to serve part of the system. The decision to create this type of system may have been based on economics, but that is certainly one of the reasons to choose one medium over another, or to combine the use of several.

Coaxial cable (coax):

Flexible coax has a copper wire core surrounded by copper braid. The core and braid are insulated from each other by a dielectric material such as polyethylene and covered by a PVC sheath.

inner conductor

copper braid dielectric PVC sheath (outer conductor)

 

The braid helps to screen the signals from interference. Coax can carry a large number of signals over long distances up to 1000 Hz. It is used to connect telephone exchanges and for cable television.

Advantages of coaxial cable:

- low cost;

- easy to install, easy to expand;

- up to 10Mbps capacity;

- moderate level of EMI immunity.

Disadvantage:

- single cable failure can take down the entire network.

 

Twisted pair.

Two insulated copper wires are twisted together to reduce interference effects and are enclosed in an insulating polyethylene sheath. Because the wires are twisted, unwanted stray signals picked up by one tend to be cancelled by similar signals picked up by the other. They are used for communications over longer distances, for example to connect telephones to their local exchange.

insulator (e.g. polyethylene) sheath

copper wire conductors

insulator (e.g. polyethylene)

covering wire

 

There are two types of twisted pairs cabling:

1) Unshielded twisted pair (UTP).

2) Shielded twisted pair (STP).

1. Unshielded twisted pair is more common. It can be either voice grade or data grade depending on the condition.

Advantages of UTP:

- easy installation;

- high speed capacity;

- low cost.

Disadvantage of UTP: short distance due to attenuation.

2. Shielded twisted pair is similar to UTP but has a mesh shielding that protects it from EMI which allows for higher transmission rate.

Characteristics of STP:

- medium cost;

- easy to install;

- higher capacity than UTP;

- higher attenuation, but same as UTP;

- medium immunity from EMI;

- 100 meter limit;

Advantages of STP: shielded; faster than UTP and coaxial.

Disadvantages of STP:

- more expensive than UTP and coaxial;

- more difficult to install;

- high attenuation rate.

 

Optical fibers.

An inner core made from very pure silica fiber is surrounded by a similar glass sheath, known as cladding. This is covered by a protective plastic sheath. Non-visible light from lasers or LEDs can travel along the fiber by reflection from the surface where the core and cladding meet.

Although the optical fiber has a smaller diameter than a human hair, it can be used to transmit tens of thousands of signals at high speed with very low loss and no interference from other signals. Optical fiber cable can be used in corrosive environments and is light, flexible and cheap. This type of cable is gradually replacing conventional copper wire for connecting telephones and computer networks.

Advantages of Fiber Optic Cable: fast; low attenuation; no EMI interference.

Disadvantages: very costly; hard to install.

Wireless Media.

Since the invention of the Wireless Telegraph in 1896 communication system designers have sought to use wireless because of the reduced infrastructure cost and complexity, when compared to wireline communication systems. There is no need to construct miles of telephone line poles or cable trenches. Simply put in a few strategically positioned radio towers and transmit around the world. Today, wireless systems are significantly more complex because we want to allow millions of users to make telephone calls or receive feature length movies via wireless systems. There are four general types of wireless (radio) communication systems:

- Cellular Telephone.

- Basic 2-Way Radio.

- Point-to-point.

- Wi-Fi (Wireless Fidelity), and recently, Wi-Max.

Traffic signal and freeway management systems use three of the variants to support operations, and are considering the use of Wi-Fi. The Wi-Fi/Wi-Max systems are becoming increasingly ubiquitous in their deployment, and a part of most telecommunication deployment strategies.

 

2.4 Read text B again and find a word or phrase that means:

- the communications channel or path over which a signal propagates;

- a type of wiring in which two conductors of a single circuit are twisted together;

- the emission of light by a substance that has absorbed light or other electromagnetic radiation, a form of luminescence;

- a type of cable that has an inner conductor surrounded by a tubular insulating layer, surrounded by a tubular conducting shield;

- a form of cable that uses a single center conductor with two shields;

- anything which alters, modifies, or disrupts a message as it travels along a channel.

 

2.5 Make up a list of terms you can find in the text. Find definitions to the terms. Make up 10 questions with the terms used in the text.

2.6 Translate the following phrases or sentences using information from text B: экранированная витая пара; высокая пропускная способность; это позволяет увеличить дальность передачи с уменьшением потерь из-за воздействия внешних электрических сигналов.

 

2.7 Read the following terms and translate them into Russian:

Media, copper wire, cable, transmission, high-speed data transmission, data communications, customer premises, high frequency, coaxial cable, bandwidth, telephone channel, local loop, long-distance network, capacity, traffic, transmission medium, wireless system.

2.8 Find all the abbreviations in the texts. Give their meanings.

2.9 Discuss the text with your neighbor in the form of a dialogue.

2.10 Find English equivalents for the following:

Одномодовый кабель (одномодовое волокно); затухание сигнала; техническая характеристика; передача данных на большие расстояния; скорость передачи данных; низкочастотные радиосигналы.

2.11 Answer these questions:

1) What are the main types of fiber cables? What is the difference between them?

2) Why is fiber considered to have the best overall characteristics for transmission efficiency?

3) What factors, besides highest transmission speed, may influence the choice of transmission media?

2.12 Compare transmission characteristics of fiber, copper, radio and infrared.

Start-up

Think of the following. What are the main parts of a communication system? What is a modem used for?

What are the main types of a telecommunication channel?

Text B. Transmission modes

Communication between two devices can occur in one of three ways: simplex, half-duplex, or full-duplex.

Simplex.

In simplex mode, the communication is unidirectional, as on a one-way street. Only one of the two devices on a link can transmit; the other can only receive.

Keyboards and traditional monitors are examples of simplex devices. The keyboard

can only introduce input; the monitor can only accept output. The simplex mode

can use the entire capacity of the channel to send data in one direction.

Half-Duplex.

In half-duplex mode, each station can both transmit and receive, but not at the same time. When one device is sending, the other can only receive, and vice versa. The half-duplex mode is like a one-lane road with traffic allowed in both directions.

When cars are traveling in one direction, cars going the other way must wait. In a

half-duplex transmission, the entire capacity of a channel is taken over by whichever of the two devices is transmitting at the time. Walkie-talkies and CB (citizens band) radios are both half-duplex systems.

The half-duplex mode is used in cases where there is no need for communication in both directions at the same time; the entire capacity of the channel can be utilized for each direction.

Full-Duplex.

In full-duplex mode (also called duplex), both stations can transmit and receive simultaneously. The full-duplex mode is like a two-way street with traffic flowing in both directions at the same time. In full-duplex mode, signals going in one direction share the capacity of the link with signals going in the other direction. This sharing can occur in two ways: Either the link must contain two physically separate transmission paths, one for sending and the other for receiving; or the capacity of the channel is divided between signals traveling in both directions. One common example of full-duplex communication is the telephone network. When two people are communicating by a telephone line, both can talk and listen at the same time.

The full-duplex mode is used when communication in both directions is required all the time. The capacity of the channel, however, must be divided between the two directions.

3.4 Answer the following questions:

1) What is the difference between half-duplex and full-duplex transmission modes?

2) Can you explain the word “walkie-talkie”?

3.5 Give some examples of simplex, half-duplex, full-duplex communication.

3.6 Write out key terms and expressions, use them to retell the text.

Text C. Networks

Defining a network. A network is the interconnection of a set of devices capable of communication. In this definition, a device can be a host (or an end system as it is sometimes called) such as a large computer, desktop, laptop, workstation, cellular phone, or security system. A device in this definition can also be a connecting device such as a router, which connects the network to other networks, a switch, which connects devices together, a modem (modulator-demodulator), which changes the form of data, and so on. These devices in a network are connected using wired or wireless transmission media such as cable or air.

Networks may be classified by various characteristics, such as the media used to transmit signals, the communications protocols used to organize network traffic, network scale, network topology and organizational scope. The best-known computer network is the Internet.

Communication protocols define the rules and data formats for exchanging information in a computer network. Well-known communications protocols include Ethernet, a hardware and link layer standard that is widely used for local area networks, and the Internet protocol suite (TCP/IP), which defines a set of protocols for communication between multiple networks, for host-to-host data transfer, and for application-specific data transmission formats. Protocols provide the basis for network programming.

Network Criteria. A network must be able to meet a certain number of criteria. The most important of these are performance, reliability, and security.

Performance. Performance can be measured in many ways, including transit time and response time. Transit time is the amount of time required for a message to travel from one device to another. Response time is the elapsed time between an inquiry and a response. The performance of a network depends on a number of factors, including the number of users, the type of transmission medium, the capabilities of the connected hardware, and the efficiency of the software.

Performance is often evaluated by two networking metrics: throughput and delay. We often need more throughput and less delay. However, these two criteria are often contradictory. If we try to send more data to the network, we may increase throughput but we increase the delay because of traffic congestion in the network.

Reliability. In addition to accuracy of delivery, network reliability is measured by the frequency of failure, the time it takes a link to recover from a failure, and the network's robustness in a catastrophe.

Security. Network security issues include protecting data from unauthorized access, protectingdata from damage and development, and implementing policies and procedures for recovery from breaches and data losses.

 

3.7 Answer the questions.

1. What devices are connected in the network?

2. By what characteristics can networks be classified?

3. Why are protocols needed?

4. What are the most important network criteria?

5. Why are throughput and delay called contradictory criteria?

6. What do you understand by the terms “security” and “reliability”?

 

3.8 Match the terms in column A and their definitions (descriptions) in column B:

A B

1. Router a) software used to find and look at information on

the web. Each web page has its own unique address

known as a Universal Resource Locator (URL).

2. Browser b) allows two different types of network to

communicate with each other.

3. Bridge c) hardware used to change analogue signals from the

phone line into digital signals needed by the

computer, also used to change the signals from

digital to analogue.

4. Modem d) define the rules and data formats

specifying the individual address.

5. Hub e) sends the signal to all the devices on the network

and only one individual PC will accept the signal.

6. Switch f) Hardware allowing computer to access the Internet

using a phone line.

 

Text D. Types of networks

There are different types and sizes of networks.

A Local Area Network (LAN) is used to connect computers spread over a relatively small area. LANs are usually placed in the same building. They can be built with two main types of architecture:peer-to-peer,where the two computers have the same capabilities, or client-server,where one computer acts as the server containing the main hard disk and controlling the other workstations ornodes,all the devices linked in the network (e.g. printers, computers, etc.).

Computers in a LAN need to use the same protocol,or standard of communication. Ethernet is one of the most common protocols for LANs.

A router,a device that forwards data packets, is needed to link a LAN to another network, e.g. to the Net.

If your personal computer is connected to a network, it is called a network workstation. If your PC is not connected to a network, it is referred to as a standalone computer.

In order to connect to a network, your computer will need a network adapter. This circuitry and port could be built into the motherboard or it could be on a network interface card (NIC) in one of the computer’s expansion slots.

Typically in a LAN, hardware is connected by a cable but new Wi-Fi, wireless fidelity technologies allow the creation of WLANs,where cables or wires are replaced by radio waves.

A LAN which uses radio waves rather than cables to transmit the data from machine to machine is called a wireless local area network (WLAN).

To build a WLAN you need access points,radio-based receiver-transmitters that are connected to the wired LAN, and wireless adapters installed in your computer to link it to the network.

Hotspotsare WLANs available for public use in places like airports and hotels, but sometimes the service is also available outdoors (e.g. university campuses, squares, etc.).

Awide area network (WAN) is a network which is spread over a large geographical area. WANs have no geographical limit and may connect computers or LANs on opposite sides of the world. They are usually linked through telephone lines, fiber-optic cables or satellites. The main transmission paths within a WAN are high-speed links called backbones.

Wireless WANsuse mobile telephone networks. The largest WAN in existence is the Internet.

The ideas associated with LANs and WLANs of sharing data and making communications easier are still true with WANs. The difference is that because of the greater distances involved it is not possible to link the computers with cables or by radio.

A WAN normally uses communication media provided by a third party. An

example would be a telephone company providing links via telephone cables or via broadband facilities.

Often, several LANs are linked up by a WAN. For example, a firm that has offices in London, Lahore and Colombo would probably use LANs in each of the offices. The company would then use telecommunication media to link the individual LANs together as a WAN.

1) Define the terms LAN, WLAN and WAN.

2) What is the difference between a LAN and a WAN?

3) Is the Internet a LAN or a WAN?

 

3.9 Now read and memorize these definitions:

A bridge is a hardware and software combination used to connect the same type of networks. Bridges can also partition a large network into two smaller ones and connect two LANs that are nearby each other.

A router is a special computer that directs communicating messages when several networks are connected together. High-speed routers can serve as part of the Internet backbone.

A gateway is an interface that enables dissimilar networks to communicate, such as two LANs based on different topologies or network operating systems.

A backbone is the main transmission path, handling the major data traffic, connecting different LANs together.

A LAN is a network contained within a small area, for example a company department.

A modem is a device for converting digital signals to analogue signals and vice versa to enable a computer to transmit and receive data using an ordinary telephone line.

 

3.10 Complete these definitions with the correct participle given in brackets.

1. A gateway is an interface (enable) dissimilar networks to communicate.

2. A bridge is a hardware and software combination (use) to connect the same type of networks.

3. A backbone is a network transmission path (handle) major data traffic.

4. A router is a special computer (direct) messages when several networks are linked.

5. A network is a number of computers and peripherals (link) together.

6. A LAN is a network (connect) computers over a small distance such as within a company.

7. A server is a powerful computer (store) many programs (share) by all the clients in the network.

8. A client is a network computer (use) for accessing a service on a server.

9. A thin client is a simple computer (comprise) a processor and memory, display, keyboard, mouse and hard drives only.

10. A hub is an electronic device (connect) all the data cabling in a network.

 

Text E. Network topology

Topologyrefers to the shape of a network. There are three basic physical topologies:

Bus: In abus network, the computers are all connected to a main cable which is known as the bus. All the data is sent along this one cable. It needs special devices at the ends of the bus calledterminators which absorb signals so that they don't get reflected back into the network and cause data corruption. Bus networks are usually easy and cheap to install. There is little to go wrong, but if a fault occurs the whole network is likely to be affected. They have generally been superseded by star networks.

Star:In astar network, each computer and peripheral is connected to a central hub or switch by its own cable. Star networks are more difficult to install than bus networks because there is more cabling. However, if one of the cables fails, the rest of the network will continue to operate. But if a hub or switch fails, none of the devices connected to it will be able to communicate.

Ring: the workstations are connected to one another in a closed loop configuration.

There are also mixed topologies like the tree,a group of stars connected to a central bus. Two common patterns are a bus network and a star network.

 

3.11 Read the descriptions of different physical topologies of communication

networks and match them with the terms in the text “Network topology”:

1) All the devices are connected to a central station.

2) In this type of network there is a cable to which all the computers and

peripherals are connected.

3) Two or more star networks connected together; the central computers

are connected to a main bus.

4) All devices (computers, printers, etc.) are connected to one another

forming a continuous loop.

3.12 Use the words in the box to complete the sentences:

LAN nodes hub backbones WLAN peer-to peer server

 

1) All the PCs on a ______________are connected to one ___________,

which is a powerful PC with a large hard disk that can be shared by everyone.

2) The style of ___________networking permits each user to share

resources such as printers.

3) The star is a topology for a computer network in which one computer

occupies the central part and the remaining _________are linked solely to it.

4) At present Wi-Fi systems transmit data at much more than 100 times

the rate of a dial-up modem, making it an ideal technology for linking computers to one another and to the Net in a __________.

5) All of the fiber-optic ____________of the United States, Canada and

Latin America cross Panama.

6) A ____________ joins multiple computers (or other network devices)

together `to form a single network segment, where all computers can communicate directly with each other.

Text F. Wireless networks

3.13 Before you read the text try to answer these questions:

1) What is a WAN?

2) How can computers be linked up over a long distance?

3) What are the advantages of optical-fiber cables over telephone lines?

4) What is the function of communications satellites?

3.14 Now read the passage and find out if your answers were correct:

For long-distance or worldwide communications, computers and LANs are usually connected into a wide area network (WAN) to form a single, integrated network. The largest WAN in existence is the Internet.

Networks can be linked together by either telephone lines orfiber-opticcables. An optical-fiber network transmits data at great speed - 100 megabits per second. A variation called FDDT transmits data at 200 Mbps. FDDI networks are typically used as backbones for wide area networks.

Modern telecommunications use fiber-optic cables because data can be transmitted at a very high speed through the extremely wide bandwidths of glass fibers. The fiber system operates by transmitting light pulses at high frequencies along the glass fiber. This offers considerable advantages:

- the cables require little physical space;

- they are safe because they don't carry electricity;

- they avoid electromagnetic interference.

Networks on different continents can also be connected viasatellite. Computers are connected by a modem either to ordinary telephone wires or fiber-optic cables, which are linked to a dish aerial. This aerial has a large concave reflector for the reception and sending of signals. Then, when signals are received by the satellite, they are amplified and sent on to workstations in another part of the world.

Wireless (WiFi) networks are just like fixed LANs but instead of using cables, devices are linked by radio waves.

Each computer in a wireless network requires a wireless network interface card (NIC). These can be built in or you can use plug-in adapters. These allow each component in the network to communicate with a wireless access point (AP) to create a wireless local area network (WLAN). The AP operates like a router in a fixed LAN. It also provides a bridge which plugs into the hub of a fxed LAN allowing both fixed and wireless users to talk to each other. If your LAN is connected to the Internet, the WLAN can also use it. If not, you can connect the WLAN to the Internet via an ADSL or cable modem.

What are the advantages of a wireless network? You don’t need cabling. In older buildings it can be expensive to install cables and access points. With WiFi, one access point can cover an entire floor or even a building. You can work anywhere within range of the access point. On a sunny day you could work outside. You can make any room in the house your study. There are now hotspots in hotels, libraries and airports, so you can link to a network away from home or your officce.

There are disadvantages. Fixed LANs can run at 1000 Mbps. Wireless networks are much slower and the further you are from an access point, the slower the rate. Although there are savings on the cost of cabling, wireless NICs are more expensive than the wired versions. Then there is the problem of interference, if a neighbour uses the same channel, and security. Other users may be able to intercept your data. Encription programs like Wired Equivalent Privacy (WEP) can help.

3.15 Write a list of the advantages and disadvantages of using wireless networks.

 

3.16 Look through the texts above and correct the following statements.

1. In a client-server architecture, all the workstations have the same

capabilities.

2. LANs link computers and other devices that are placed far apart.

3. The word protocol refers to the shape of the network.

4. Routers are used to link two computers.

5. Access points don’t need to be connected to a wired LAN.

6. Wireless adapters are optional when you using a WLAN.

7. Hotspots can only be found inside a building.

8. The Internet is an example of a LAN.

9. Wireless WANs use fiber and cable as linking devices.

Text G. (A) Основные характеристики каналов связи

Основная характеристика канала связи – скорость передачи данных, т.е. суммарное количество информации, которое может быть передано через коммуникационный канал. Скорость передачи измеряется в битах в секунду (bits per second, BPS). Производительность канала связи зависит от диапазона частот, которые могут использоваться для передачи данных – полосы пропускания (bandwidth), которая представляет собой разность между самой высокой и самой низкой частотами, на которых канал связи может передавать данные. Еще одна важная характеристика каналов связи – режимы передачи сигналов. Существует два режима передачи – синхронный и асинхронный. Асинхронная связь медленнее синхронной, так как требует передачи стартовых и стоповых битов. Наконец, на производительность канала связи влияет направление передачи данных. В системах симплексной связиданные всегда могут передаваться только в одном направлении. Полудуплексная связьпозволяет передавать данные в двух направлениях; но в каждый момент времени устройства могут только передавать или только принимать данные. Системы полнодуплексной связи могут одновременно передавать и принимать данные. К основным типам коммуникационных каналов относятся: телефонные линии (коммутируемые и выделенные), коаксиальный кабель, кабель витая пара, волоконно-оптический кабель, а также различные беспроводные линии связи (радиорелейные, спутниковые, инфракрасные).

(B) Назначение модема. Виды модемов и области их применения

Модемы применяются для передачи данных по телефонным линиям. При передаче данных модем выполняет преобразование цифровых сигналов, посылаемых компьютером, в аналоговые сигналы, которые можно передавать по телефонной линии. При приеме данных модем выполняет обратное преобразование сигналов – из аналоговой формы в цифровую. Модемы, работающие на асинхронных линиях связи, к которым относятся обычные коммутируемые телефонные линии, называются синхронными. Модемы, осуществляющие прием и передачу данных через выделенные линии, называются асинхронными.

Unit 4. Satellite Systems

Start-up

Word study

4.1 Translate the following definitions and memorize the terms:

altitude - 1) height above sea-level Syn: height; 2) the angular distance of a celestial body from the horizon measured along the vertical circle passing through the body; Syn: azimuth.

augment - to make greater; Syn: increase, enhance.

constellation - named group of fixed stars: Many of the 88 groups of stars were named by the ancient Greeks after animals, objects, or mythological persons.

latitude - distance north or south of the equator: It is situated in the latitude of 40 degrees.

longitude - distance east or west from the Greenwich meridian: The prime meridian is at 0°

sidereal - determined with reference to stars. Syn: star, stellar.

precise - strictly correct in amount or value. Syn: exact, punctual; Ant: approximate.

vehicle - a means for transporting people or objects. Syn: conveyance.

maintain - to keep in proper or good condition Syn: support.

utility - 1) the thing of practical use; 2) a piece of computer software designed for a routine task.

adjust - to alter slightly, esp. to achieve accuracy; Syn: regulate.

sequence - the successive order of two or more things Syn: progression , series , succession.

Word building

4.2 Form the adjectives from the following nouns. Consult a dictionary if necessary:

Noun Adjective
accuracy  
integrity  
reliability  
availability  
precision  
efficiency  
application  
sequencing  
productivity  

4.3 Match up the words which are opposite in meaning:

Proper, precise, worldwide, occasional, allied, significant, transmit, incorporate, exclude, receive, constant, approximate, unimportant, rival, incorrect, local.

 

4.4 Match up the words which have similar meanings:

Assistance, azimuth, perform, inseparable, regulate, support, enhance, stellar, yearly, maintain, annual, inherent, adjust, augment, altitude, sidereal, aid, implement.

 

4.5 Match the following words with their Russian equivalents:

столкновение sequence

совместимый collision

последовательность alert

поддерживать compatible

предсказывать maintain

подчеркивать estimate

настраивать accelerate

ускорять adjust

оценивать underscore

предупреждать forecast

 

4.6 Guess the words by their definition:

1) Something useful.

2) Height above the sea-level.

3) One of several parts or sections into which an object is divided.

4) The curved path, usually elliptical, followed by a planet, satellite, comet, etc., in its motion around another celestial body under the influence of gravitation.

5) A single piece of information.

6) Any conveyance in or by which people or objects are transported.

7) The wide end of a cathode-ray tube, on which a visible image is formed.

8) The limits within which a thing can function effectively.

9) The unlimited three-dimensional expanse in which all material objects are located.

4.7 Read text A and match the headings (a-d) with the paragraphs(1-4).

b) GPS augmentations.

b) Roads & Highways.

c) What is GPS?

d) Timing.

Comprehension check

4.9 Answer the questions:

1) What are the main segments of GPS?

2) What augmentation are supposed in GPS?

3) Is the GPS system popular?

4) How many satellites does navigation system comprise?

5) What augmentation serves the US NASA science mission?

6) Why is timing so important?

7) What is the precision of atomic clock?

8) How are navigation systems used on the roads?

9) What is GIS?

10) What is ITS?

 

4.10 Read the text again and decide whether these statements are true (+) or false (—), correct the false ones:

1) The GPS provides only positioning services.

2) The system consists of four segments.

3) A number of augmentations are available in over 60 countries.

4) Precise time is crucial for military purposes only.

5) GPS is used in making modern films.

6) The delays on the roads directly affect the economy.

7) In-vehicle navigation systems are not common yet.

8) GIS is used to keep transit vehicles on schedule.

9) GPS is an essential element of ITS.

10) ITS is able to estimate the position of a vehicle with an accuracy of 1 cm.

 

Language in use

4.11 Replace the italicized words with the equivalents from the box.

sidereal annually vehicle altitude aid augmentation
precise maintain    

 

1.The planes are orbiting at aheight of approximately 20000 km.

2. Each orbital plane carries four spaceconveniences.

3. Each space vehicle makes two complete orbits eachstellar day.

4. A number ofenhancements to the GPS are available.

5. Each GPS satellite contains multiple atomic clocks that contribute veryexact time data to the GPS signals.

6. The control segmentsupports health and status of the satellite constellation.

7. GPS has become a widely used help to navigation worldwide.

8. Delays from congestion on highways result in productivity losses in the hundreds of billions of dollarsyearly.

4.12 Complete the sentences with the words as in the text.

constellation, 3-dimensional, augmentation, synchronize, maintains, efficiency, vehicle, utility, displays

1. GIS is used to monitor_________________ location.

2. GIS stores, analyses and______________ geographically referenced information.

3. An_____________ is any system that aids GPS.

4. The GPS is a___________ that provides users with PNT services.

5. The space segment_____________ consists of 24 satellites.

6. The control segment____________ the satellites in their proper orbits.

7. The user's segment calculates the user's ___________position and time.

8. Major banks use GPS to____________ their computers around the world.

9. Many economic activities rely on precision timing for operational______.

Grammar Revision:Noun attributes and Passive Voice:

4.13 Read and translate the following word combinations paying attention

to nouns as attributes.

Remote control station, light pulses, light wave communications system, transmission system, telecommunications network, glass fiber, voice signal, data signal, television signal, telecommunications transmission, construction cost, underground duct, copper cable, signal regenerator, carrier system, device reliability, laser beam wave, radio wave speed, disaster- relief team, , one-way signal, three-dimensional position, on-time performance, advanced- driver assistant system, disaster-relief team, lane-change collision avoidance system, crash prevention, position notification.

4.14 Read the following sentences and say which of them are in the Active and which are in the Passive Voice. Translate them into Russian.

1. While the experiment was being carried out nobody left the station.

2. A new type of satellite equipment is being produced at our plant.

3. At present scientific work is being done mostly by large groups of researchers.

4. The apparatus will be working when you come.

5. The scientists who are carrying out research into radio astronomy deal with the most difficult problems.

6. For twenty minutes the air in the laboratory was being purified by two ventilators.

7. The solar battery is converting the energy of sun rays directly into electric energy.

8. This experiment was being carried out in vacuum.

9. For a long time the electronic devices were being used for control.

10. An interesting research in the field of electronics is being done at our Institute.

11. Prospects of the usage of solar energy are already understood by everybody.

12. Now solar energy is being studied by a lot of research groups.

13. Siberian scientists are developing new types of geostationary devices.

14. We were looking for a more simple method of solution but could not find it.

15. The engineers will discuss the advantages of this new system.

16. Our laboratory is housed in an old building.

17. A new navigation equipment is being examined by our scientists now.

4.15 Read text B and say if it covers the following ideas:

1. What is the name of the Chinese navigation system?

2. What countries develop the Galileo system?

3. What is driving the technological battle between Russia and US?

4. How many satellites does navigation system need?

5. What is the advantage of the GLONASS-capable GPS receiver?

 

Text B. GLONASS

The days of the cold war may have passed, but Russia and the United States are in the midst of another battle - this one a technological fight over the United States monopoly on satellite navigation. Nor is Russia the only country trying to break the American monopoly on navigation technology. China has already sent up satellites to create its own system, called Baidu after the Chinese word forthe Big Dipper1. And the European Union has also begun developing a rival system, Galileo, although work has been halted because of doubts among the private contractors over its potential for profits.

GLONASS is a radio-based satellite navigation system, developed by the former Soviet Union and now operated for the Russian government by the Russian Space Forces. Development on the GLONASS began in 1976. The constellation was completed in 1995, but the system rapidly fell into disrepair with the collapse of the Russian economy. Beginning in 2001, Russia committed to restoring the system by 2011, and in recent years has diversified, introducing the Indian government as a partner, and accelerated the program with a goal of global coverage by 2009 A fully functional GLONASS constellation consists of 24 satellites, with 21 operating and three on-orbitspares[1], deployed in three orbital planes. A characteristic of the GLONASS constellation is that any given satellite only passes over the exact same spot on the Earth every eighth sidereal day. However, as each orbit plane contains eight satellites, a satellite will pass the same place every sidereal day. For comparison, each GPS satellite passes over the same spot once every sidereal day.

There were three generations of the satellites. The true first generation of Uragan satellites were all 3-axis[2] stabilized vehicles, generally weighing 1,250-kg.

These spacecraft demonstrated a 16-month average operational lifetime. The second generation of satellites, known as Uragan-M (also called GLONASS-M), possess a substantially increased lifetime of seven years and weigh slightly more - 1,480 kg. The latest designed generation of Uragan-K (GLONASS-K) spacecraft are the third generation of satellites. These satellites are designed with a lifetime of 10 to 12 years, a reduced weight of only 750 kg, and offer an additionalL-Band4 navigational signal. As with the previous satellites, these are 3-axis stabilized,nadir5 pointing with dual solar arrays.

By May 2007 the system remains partially operational. There were 11 satellites. In recent years, Russia has kept the satellite orbits optimized for navigating in Chechnya, increasing signal coverage there at the cost of degrading coverage in the rest of the world. GLONASS availability in Russia was 45.3% and average availability for the whole Earth was down to 30.5%, with significant areas of less than 25% availability. Meaning that, at any given time of the day in Russia, there is a 45.3% likelihood that a position fix can be calculated.

The Russian system is also calculated to send ripples through the fast-expanding industry for consumer navigation devices by promising a slight technical advantage over G.P.S. alone. Devices receiving signals from both systems would presumably be more reliable. "The network must be impeccable, better than G.P.S., and cheaper if we want clients to choose Glonass," Mr. Putin said at a Russian government meeting on the system.

Notes (B):

1) 1the Big Dipper - Большая Медведица (the US and Canadian name for

the Plough (constellation).

2) 2spare- запасной (in reserve for use when needed).

3) 3axis - ось (a real or imaginary line about which a body, such as an

aircraft, can rotate or about which an object, form, composition, or geometrical

construction is symmetrical).

4) 4 L-Band - RF range 390 - 1550 MHz

5) 5nadir - надир (the point on the celestial sphere directly below an

observer and diametrically opposite the zenith).

4.16 Make up 10 questions to the text using the following constructions:

What is the (nature, difference, process, role, importance, etc.) of…?

What is referred to as….?

What is used as…?

Where do we use. …?

What function do the ... play?

Discussion

1. Does Russia really need its own navigation system?

2. Does Kazakhstan need to have its own navigation system?

Start-up

5.1 Work with a partner. Make a list of all the things some of the latest mobile devices can replace. What can your personal mobile phone do, besides sending SMS?

Text A. State of play

To celebrate our 10th anniversary, we invited industry leaders to share their thoughts about the changing world of Telecoms and IT. To find out what they think, read on ...

Peter Wilson

The world is now plugged in, and countries are connected up using a mixture of terrestrial networks, undersea cables, satellite and micro­wave communications, Wi-Max and Wi-Fi, GSM and 3G. The move from packet-based services to the internet protocol means everyone expects to communicate voice, data and video from anywhere to anywhere, globally. The availability of wide area data services such as MPLS and Ethernet have spread all over the world, allowing companies to manage and communicate with their operations wherever they may be.

A reason for this has been the fall in bandwidth costs, and broadband is getting cheaper and cheaper. Services can now deliver tens or even hundreds of megabits of bandwidth into individual homes for much less money than a 64Kb line that a whole factory might have used to run its operation only a few years ago.

Jenny Lane

In 1965 Gordon Moore stated that the number of transistors on a chip would double about every two years. And that has more or less remained true since then. As we write, a single chip can hold about 1 billion transistors each making 3 billion binary calculations per second.

There has' been a huge increase in the volume of data and data storage capacity required for this; secondly, there has been a significant decrease in the size and power consumption of hardware and finally manufacturing costs are falling significantly. The result is that there are more and more powerful computers in our lives, and even handheld devices can store gigabytes of data holding thousands of MP3 music, files or hundreds of films.

Sanjay Ravi

The internet is changing the way we access, buy and use applications. We go online and download the software we want onto our computer, like any other digital product. Increasingly we don't even have the software on our hardware, but visit an internet site and use that application as a service. The use of this Software as a Service (SaaS) model means that we may not need such powerful computers in the future.

We have seen the impact of off- shoring and the rise of India as the world centre of software development and application management. We are also seeing some of the smartest applications and services coming out of people's bedrooms; more and more experts are producing Open source software, which is becoming more and more popular, creating a real threat to the big corporations.

 

5.5 Read the text again. Say if the following statements are TRUE (T) or FALSE (F) according to the text.

According to Peter Wilson:

1) most countries are connected up with undersea cables. T F

2) many countries have unreliable mobile phone networks. T F

3) recently bandwidth costs have risen dramatically. T F

According to Jenny Lane:

4) Moore's predictions have been fairly accurate. T F

5) a typical chip can now hold 3 billion transistors.T F

6) both data storage capacity and power consumption have gone up.T F

According to Sanjay Ravi:

7) fewer people are going to computer stores to buy software. T F

8) SaaS will require ordinary users to have more powerful computers. T F

9) software development needs the support of a big corporation to succeed. T F

5.6 Match the words on the left with the words on the right to make pairs of words that often go together. The word on the left must go with all three words in the set. See the example.

1 access a chip, wafer, valley

2 download —— b an application, a network, an account

3 go с online, offline, on holiday

4 mobile d phone, telephony, broadband

5 silicon e a file, an image, a demo version

5.7 Complete the sentences using pairs of words from exercise. Make any changes that are necessary.

_ 1 Everyone has_______ , so payphones are becoming redundant.

2 Many internet entrepreneurs from______________ in California are now turning their attention to alternative forms of energy.

3 Before you buy the program, you can__________just to see how you like it.







Читайте также:

Последнее изменение этой страницы: 2016-03-17; Просмотров: 111; Нарушение авторского права страницы


lektsia.com 2007 - 2017 год. Все права принадлежат их авторам! (0.083 с.) Главная | Обратная связь