Lecture3.docx - Lecture 3 Transmission Transmit issue signals along the network medium Transmission process of transmitting signal progress after

Lecture3.docx - Lecture 3 Transmission Transmit issue...

  • Ryerson University
  • ITM 301
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Lecture 3Transmission-Transmit: issue signals along the network medium-Transmission: process of transmitting; signal progress after transmitting-Transceiver: transmits and receives signals; such as NICs-Volts: pressure of electrical current-Voltage: directly proportionate to strength of a signal; signal’s voltage-Signals: travel as electrical current, light pulses, or electromagnetic waves-Important characteristic of data transmission: signaling typeoAnalog signals: voltage varies continuouslyAppears as a wavy line when graphed over timeFundamental properties:Amplitude: measure of strength at a given point in timeFrequency: number of times amplitude cycles over a fixed time; cycles per second; HertzWavelength: distance between one peak and the next; inversely proportional to frequency; higher the frequency, shorter the wavelengthPhase: progress of wave over time compared to a fixed pointBenefit: more variable; convey greater subtleties with less energyDrawback: varied and imprecise voltage; susceptible to transmission flawsoDigital signals: pulses of voltagesPositive voltage represents 1, zero voltage represents 0Binary system (1s and 0s); every pulse in the digital signal is called a binary digit, or bit8 bits = 1 byteConvert byte to decimal number; convert decimal number to byte; convert between binary and decimalBenefit: more reliable; less severe noise interferenceDrawback: many pulses required to transmit same information-Overhead: non data information required for proper signal routing and interpretation; such as network layer addressing information-Data modulation: technology modifying analog signals; make data suitable for carrying over communication pathoData relies on digital transmission; network connection may only handle analog signalsoModem: accomplishes this translation; functions as a modulator/demodulatorModulates digital signals into analog signals at the transmitting end, then demodulates analog signals into digital signals at the receiving endoCarrier wave combined with another analog signal to produce a unique signal that gets transmitted from one node to another; purpose is to convey information; only a messengerCarrier wave has preset properties: frequency, amplitude, and phaseInformation wave/data wave: added to carrier wave and modifies one property of the carrier waveThis results in a new blended signal that contains properties of both carrier wave and added data; when the signal reaches its destination, the receiver separates the data from the carrier waveoModulation can be used to make a signal conform to a specific pathway
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Frequency modulation (FM): carrier frequency modified by application of data signalAmplitude modulation (AM): carrier amplitude modified by application of data signaloDigital subscriber line (DSL) also makes use of modulation-Simplex: data transmission where signals can only travel in one direction-
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