Spring 2000John Kristoff1 Physical Layer Computer Networks

Spring 2000 John Kristoff 1

Physical Layer

Computer Networks

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Numbering Systems

BinaryHexadecimalDecimal

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Transmission of Information

From Physics Energy Electromagnetic wave propogation

From Mathematics Coding Theory

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Analog and Digital Signaling

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Amplitude Modulation

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Frequency Modulation

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Baseband and Broadband

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Phase Modulation

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Modems

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Digital Encoding

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CSU/DSU

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Undesirable Effects and Limitations

Propagation DelayBandwidthNoiseInterferenceDistortionAttenuation

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Sampling and Nyquist’s Theorem

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Shannon’s Limit

Corrects for SNR

Encoding more bits per cycle time helps, but you cannot overcome the fundamental physical limits of a real transmission system.

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Timing

Asynchronous bit level

Synchronous character level

Isochronous timing coordination must be successful

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Transmission Media

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Connectors

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Media Test and Measurement

Hands-on Demo

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Repeaters

Signal RegenerationClean upAmpliflyDistance Extension

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Hubs

Repeater functionality, plus...Concentration PointSignal Distribution DeviceManagement Functions

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Throughput versus Bandwidth

Usable capacityDetermined by

engineering

Electrical PropertyDetermined by

physics