Physical Layer

1
Physical Layer
Computer Networks
2
Where are we?
3
Numbering Systems

• Binary
• Hexadecimal
• Decimal

4
Transmission of Information

• From Physics
• Energy
• Electromagnetic wave propogation
• From Mathematics
• Coding Theory

5
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
12
CSU/DSU
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Undesirable Effects and Limitations

• Propagation Delay
• Bandwidth
• Noise
• Interference
• Distortion
• Attenuation

14
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
19
Media Test and Measurement

• Hands-on Demo

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Repeaters

• Signal Regeneration
• Clean up
• Amplifly
• Distance Extension

21
Hubs

• Repeater functionality, plus...
• Concentration Point
• Signal Distribution Device
• Management Functions

22
Throughput versus Bandwidth

• Usable capacity
• Determined by engineering

• Electrical Property
• Determined by physics