Fundamentals of Data & SignalsLearning ObjectivesData and SignalsDataSignalsSlide 6Translation DevicesDSU (Data Service Unit)Analog signalsDigital signalsDigital SignalsDigital Versus Binary TransmissionStates and BitsSlide 14Slide 15Bits and BaudEquationsExerciseSummary QuestionsFundamentals of Data & SignalsSchool of BusinessEastern Illinois University © Abdou Illia, Spring 2007(Week 5, Tuesday 2/6/2007)2Learning ObjectivesDistinguish between Data and SignalsUnderstand transmission speedDistinguish between Bit Rate and Baud Rate3Data and SignalsIngredients of Computer Networks–Computers–Transmission media–Hubs/Switches–Routers, bridges–Etc.Other ingredients–Data–Signals4DataData = Entities that convey meaning within a computer systemExamples of data (captured and stored on storage devices)–Files on a hard drive–Movie on a DVD–Music on a CDFor transmission, Data (static entities) need to be converted into signals (dynamic entities)5SignalsSignal = Electric or electromagnetic encoding of data for transmission–Using a physical transmission medium–Using airwavesExamples of signals (situations)–Telephone conversation over a telephone line–Live television news interview from Europe–Web page download over your telephone line via the Internet6Data and SignalsBoth Data (sources of data) and Signals can be–either analog–or digitalFour combinations–Transmitting digital data using digital signals–Transmitting digital data using analog signals–Transmitting analog data using analog signals–Transmitting analog data using digital signalsNeed Translation devices7Translation DevicesSource of Data versus LineAnalog Line Digital LineAnalog Device (e.g. Tel)CodecDigital Device (e.g. Computer)Modem DSUTranslatorTransmission LineSource of Data8DSU (Data Service Unit)DSU translates between different digital formats–Device and line are both digital, but still might need translator becauseDifferent bit ratesDifferent number of possible statesDifferent voltage levels for the statesDifferent ways to represent ones and zeros9Analog signalsRepresented as continuous waveformsIn analog transmission, the state of the signal (voltage level, etc.) varies continuously and smoothly among an infinite number of states–States could be signal strength, voltage level, or other measurable conditions10Digital signalsRepresented as discrete (non-continuous) waveformIn digital transmission, time is divided into periods of fixed length called clock cyclesThe state of the signal (voltage level, etc.) remain constant during each clock cycle.–Typically, there are between two and 64 possible states.–Here, only two states are shownClock CycleTimeVoltage11Digital SignalsAt the end of each clock cycle, the state may change abruptly to another of the few possible states–Can also stay the sameClock CycleTimeAbruptChangeStays SameVoltage12Digital Versus Binary TransmissionDigital transmission: a few statesBinary transmission: exactly two states (1 and 0)–Binary is a special case of digitalDigital BinaryTwo StatesFew States0113States and Bits2Bits per clock cycle=Number of states–For 1 bit per clock cycle,–2 states are required (One for 1, one for 0)–21=2–Binary100 0 01Clock CycleStates14States and Bits2Bits/clock cycle=States–For 2 bits per clock cycle, 4 states are required (22=4)–For 3 bits per clock cycle, 8 states are needed (23=8)–For 4 bits per clock cycle, 16 states are needed (24=16)3 (11)2 (10)1 (01)0 (00)00011011Clock CycleStates15States and Bits2Bits per clock cycle=States–With 4 states, send two bits per clock cycle (22=4)–With 8 states, send 3 bits per clock cycle (23=8)–With 16 states, send 4 bits per clock cycle (24=16)3 (11)2 (10)1 (01)0 (00)00011011Clock CycleStates16Bits and BaudBaud Rate = Number of clock cycles/sec–In this example, 4 baud (not 4 bauds/second)–Note: Number of clock cycles, not actual line changesBit Rate = Number of bits/second–In this example, 8 bits/secondBit Rate = Baud Rate * Bits per clock cycle000110011 SecondPossible Change Not Made17Equations# of states–2Bits per clock cycle = Number of possible states (Eq. 1)Bit rate–Bit rate = Baud Rate * Bits per clock cycle (Eq. 2)Exercise(See next slide)18ExerciseA) If a transmission line has a Baud rate of 10 000 baud, and if there are eight possible line states, what is the Bit rate? B) If you wish to send two bits per clock cycle, how many possible states must you have?19Summary Questions1. Distinguish between digital and analog signals2. Distinguish between digital and binary transmission3. What is the difference between the bit rate and the baud rate?
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