МУ РЭТ. Unit Telecommunications. Basic Concepts
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Grammar notes. Relative clauses with a participle. Relative clauses with a participle are often used in technical descriptions. They allow you to provide a lot of information about a noun using as few words as possible. Study these examples: 1) Computers equipped with wireless NICs. 2) A network printer connected to a wireless print server. 3) A modem providing access to the Internet. 4) A fixed LAN linking computers with cables. We can use the passive participle as in examples 1 and 2. 1) Computers equipped with wireless NICs. = computers which are equipped… 2) A network printer connected to a wireless print server = a network printer which is connected… We can use an active participle as in examples 3 and 4. 3) A modem providing access to the Internet. = modem which provides access to the Internet. 4) A fixed LAN linking computers with cables. = A fixed LAN which links computers with cables. 3.17 Define which type of network topology the following statements refer to (star or bus) 1. Every networked device has its own physical link with the hub or switch. 2. Any break in the ... causes serious problems. 3. If one network device crashes, or there is a fault in the network cable, all the other stations are still able to function correctly. 4. This type of network is fast, reliable and inexpensive and is the most common. 5. The performance of the entire network is directly dependent on the performance of the hub. If the server is slow, it will cause the entire network to slow down. 6. Cable length required for this topology is the least compared to other networks. 7. Security is very low because all the computers receive the sent signal from the source. 8. … is mostly used in small networks. Good for LAN. 9. …the data packets don't have to make their way through various nodes which makes sure that the data transfer is fast. 10. …is the simplest of network topologies. In this type of topology, all the nodes (computers as well as servers) are connected to the single cable… 3.18 Describe the main features of a LAN in a paragraph or two: 3.19 Think of possible dangers from the Internet and what measures can be taken to prevent the negative impacts. Write a short (1-page) essay: 3.20 Read the following texts (G-A,B) and write definitions (in English) of the basic terms (italicized). 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 связи данные всегда могут передаваться только в одном направлении. Полудуплексная связь позволяет 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:
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. Text A. The Global Positioning System (GPS) 1._______________________________ The Global Positioning System (GPS) is a U.S.-owned utility that provides users with positioning, navigation, and timing (PNT) services. This system consists of three segments: 1) The space segment constellation consists of 24 satellites, that transmit one-way signals that give the current GPS satellite position and time. 24 Space Vehicles (SVs) are distributed equally among six circular orbital planes. The orbital planes are centered on the Earth, not rotating with respect to the distant stars. Orbiting at an altitude of approximately 20,200 kilometers; orbital radius of 26,600 km, each SV makes two complete orbits each sidereal day. 2) The control segment consists of worldwide monitor and control stations that maintain the satellites in their proper orbits through occasional command maneuvers, and adjust the satellite clocks. It tracks the GPS satellites, uploads updated navigational data, and maintains health and status of the satellite constellation. 3) The user segment consists of the GPS receiver equipment, which receives the signals from the GPS satellites and calculates the user's three-dimensional position and time. In general, GPS receivers are composed of an antenna, tuned to the frequencies transmitted by the satellites, receiver-processors, and a highly-stable clock. Receivers typically have between twelve and twenty channels. 2.______________________________ GPS has become a widely used aid to navigation worldwide, and a useful tool for map- making, land surveying, commerce, and scientific uses. To meet the specific user requirements for PNT, a number of augmentations to the GPS are available. An augmentation is any system that aids GPS by providing accuracy, integrity, reliability, availability, or any other improvement that is not inherently part of GPS itself. Nationwide Differential GPS System provides increased accuracy and integrity of the GPS to users on land and water. Modernization efforts include enhancing the performance and providing 10 to 15 centimeter accuracy throughout the coverage area. Over 50 countries around the world have implemented similar systems. Wide Area Augmentation System provides aircraft navigation for all phases of flight. Continuously Operating Reference Station archives and distributes GPS data for precision positioning and atmospheric modeling applications mainly through post-processing1. Global Differential GPS supports the real-time positioning, timing, and orbit determination requirements of the U.S. National Aeronautics and Space Administration (NASA) science missions. The U.S. Policy underscores the importance that all global navigation satellite systems and their augmentations be compatible with the GPS. 3.__________________________________________ In addition to longitude, latitude, and altitude, the Global Positioning System (GPS) provides a critical fourth dimension - time. Each GPS satellite contains multiple atomic clocks that contribute very precise time data to the GPS signals. GPS receivers decode these signals, effectively synchronizing each receiver to the atomic clocks. This enables users to determine the time to within 100 billionths of a second. Precise time is crucial to a variety of economic activities around the world. Communication systems, electrical power grids, scientific study of earthquakes and financial networks all rely on precision timing for synchronization and operational efficiency. Wireless telephone and data networks use GPS time to keep all of their base stations in perfect synchronization. Similarly, digital broadcast radio services use GPS time to ensure that the bits from all radio stations arrive at receivers in lockstep2 . Companies worldwide use GPS to time-stamp3 business transactions. Major investment banks use GPS to synchronize their network computers located around the world. Hollywood studios are incorporating GPS in their movie slates4, allowing for unparalleled control of audio and video data, as well as multi-camera sequencing. 4.______________________________________ It is estimated that delays from congestion5 on highways and streets throughout the world result in productivity losses in the hundreds of billions of dollars annually. GPS enables automatic vehicle location and in-vehicle navigation systems that are widely used throughout the world today. By combining GPS position technology with systems that can display geographic information a new dimension in surface transportation is realized. A geographic information system (GIS) stores, analyzes, and displays geographically referenced information. Today GIS enables effective strategies that can keep transit vehicles on schedule and inform passengers of precise arrival times. GPS is an essential element in the future of Intelligent Transportation Systems (ITS). Research is being conducted in the area of advanced driver assistance systems, which include road departure and lane change collision avoidance systems. These systems need to estimate the position of a vehicle relative to lane and road edge with an accuracy of 10 centimeters. With the continuous modernization of GPS, one can expect even more effective systems for crash prevention, distress alerts and position notification, electronic mapping, and in- vehicle navigation with audible instructions. GPS receivers come in a variety of formats, from devices integrated into cars, phones, and watches, and many other devices. Notes: 1) 1post-processing - обработка данных (to perform mathematical and logical operations on data according to programmed instructions in order to obtain the required information). 2) 2inlockstep - зд. строго одновременно, букв. «шаг в ногу» (progressing at exactly the same speed and in the same direction as other people or things). 3) 3time-stamp - временная отметка (to assign an accurate time to a message, transaction, etc.) The database entry consists of the MAC address, the port that address was seen on, and a time- stamp to indicate when it was see. 4) 4slates - доска, которой хлопают перед очередным дублем (a pair of boards clapped together during film shooting in order to aid sound synchronization). 5)5congestion - скопление (the state of being overcrowded, esp. with traffic or people). 4.8 Write out of text A phrases describing general uses of GPS. |