Chapter 2 : Data Transmission

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Data Transmission
  1 Data Transmission & Transmission Media  Chapter Two Outline  Signal  Analog  Digital  Transmission Mode  Parallel Transmission  Serial Transmission  Digital Transmission  Digital to digital Modulation  Analog to digital Modulation  Analog Transmission  Digital to analog transmission  Analog to analog transmission  Transmission Media  Guided  Unguided -wireless NetworkingNetworking .  Transmission of data across network connections  To be transmitted, data must be transformed to electromagneticsignals  2 Position of the Physical LayerPosition of the Physical Layer  Service –send stream data from sender to receiver   Node-to-node delivery  Transmission medium control on the direction of data flow ServicesServices  convert data (bit pattern) to  signal  Determines maximum limit of data  rate transmission depend on the design of physical hardware and  software  providing clocking mechanism to control  sender and  receiver   timing of the transfer    set of techniques that allows the  simultaneou s transmission of multiple  signals across a  single data link  Create direct connection two devices  such as phones or computers Analog Signal  3 Analog and Digital Data Analog data –human voicecaptured by a microphone and converted to an analog signalDigital data –form 0s and 1sconverted to a digital signal when transferred from one position to another  Analog Signal Analog and Digital SignalsAnalog and Digital Signals Analog signals can have an infinite number of values in a rangeDigital signals can have only a limited number of values. Analog Signal Analog and Digital Signals Means by which data are propagatedAnalog  Continuously variable  Various media  wire, fiber optic, space  Speech bandwidth 100Hz to 7kHz  Telephone bandwidth 300Hz to 3400Hz  Video bandwidth 4MHz Digital  Use two DC components  4 Comparison of Analog and Digital Signals Analog Signal Periodic and Periodic and AperiodicAperiodicSignalsSignals In data communication, we commonly use periodic analog signals and aperiodic(non-periodic) digital signals.  Periodic signal –completes a pattern within a measurable time frame, called a period and repeats that pattern over subsequent identical periods.  Pattern repeated over time  Completion of one full pattern – cycle  Aperiodicsignal –changes without exhibiting a pattern or cycle that repeats over time  Pattern not repeated over time Analog Signal Analog Signals  Classified as:  Simple (Sine Wave) –  cannot be decomposed into smaller signals  Composite –  composed of multiple sine waves Analog Signal
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