1 Physical Layer Computer Networks. 2 Where are we?

1

Physical Layer

Computer Networks

2

Where are we?

3

Numbering Systems

BinaryHexadecimalDecimal

4

Transmission of Information

From PhysicsEnergyElectromagnetic wave propogation

From MathematicsCoding Theory

5

Analog and Digital Signaling

6

Amplitude Modulation

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Frequency Modulation

8

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

Asynchronousbit level

Synchronouscharacter level

Isochronoustiming 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

21

Hubs

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

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Throughput versus Bandwidth

Usable capacityDetermined by

engineering

Electrical PropertyDetermined by

physics