Wednesday, 26 October 2011

DATA COMMUNICATION Terminology

Simplex

One direction
• e.g. Television

Half duplex
— Either direction, but only one way at a time
• e.g. police radio
• Full duplex
— Both directions at the same time
• e.g. telephone

Frequency, Spectrum and
Bandwidth
Time domain concepts

Analog signal
• Varies in a smooth way over time
— Digital signal
• Maintains a constant level then changes to another constant
level
— Periodic signal
• Pattern repeated over time
— Aperiodic signal
• Pattern not repeated over time
Analogue & Digital Signals



Periodic
Signals

Frequency Domain Concepts


Signal is usually made up of many frequencies
• Components are sine waves
• It can be shown (Fourier analysis) that any
signal is made up of component sine waves
• One can plot frequency domain functions
Data Rate and Bandwidth

• Any transmission system has a limited band of
frequencies
• This limits the data rate that can be carried


Reference :-

Data Communication











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