Matakuliah
Tahun
Versi
: M0284/Teknologi & Infrastruktur E-Business
: 2005
: <<versi/revisi>>
Pertemuan 3
Networking Fundamentals
1
Learning Objectives
• Differentiate between Analog and Digital
Signals
• Understand Modulation and Multiplexing
2
Overview
• Digital and Analog
• Modulation AM and FM
• Multiplexing FDM and TDM
3
Analog and Digital
4
Digital and Analog
• Digital technologies are a fundamental building
block of the platform that makes E-Business
possible. Computers are digital. Most
transmission systems are becoming digital.
• Digital: Discrete
• Analog: Continuously changing
• Advantages of Digital:
– Easier to recover signals after distortion.
– Digital signals can be converted to numbers
– Existing technologies are largely digital
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Digital: Signal Regeneration
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Analog to Digital Conversion
• Signals in nature, sound and light, are
analog
• Technology is increasingly digital
• Need to change analog to digital.. Music
CDs, Digital telephony, digital cellular phone
• Analog wave described as a set of
discrete points
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Digital Signals: Pulse Code Modulation
8
Pulse Code Modulation PCM
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Used in digital telephone transmission
Music CD-ROMs
DVDs for movies and music
Sound Cards in PCs. Multimedia applications
In telephony: sampling done 8000 times
per second, each time 8 bits are
transmitted. That is, 64Kilobits/second to
represent voice
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Modulation: AM and FM
• Most transmission media accept only
continuous signals
• Information from computers in 1s and 0s
• Need to use continuous signals to transmit
digital values
• Use a wave’s amplitude, frequency and
phase and modulate them
• Used in Modem (modulator +
demodulator)
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Modulation: A smooth wave
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Amplitude Modulation
Change amplitude, keep frequency constant
12
Frequency Modulation
Change frequency, keep amplitude constant
13
Multiplexing
• To send multiple signals over the same
media simultaneously.
• Enhance media capacity
• FDM: Frequency division multiplexing
• TDM: Time division multiplexing
• Digital cellular phones use TDM and FDM
to transfer signals
• Digital telephone systems use multiplexing
14
Frequency Division Multiplexing
Multiple channels on different frequencies
15
Time Division Multiplexing
Splitting time into different channels
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