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Unformatted text preview: William Stallings Data and Computer Communications 8 th Edition Chapter 3 Data Transmission Terminology (1) • Transmitter • Receiver • Medium — Guided medium • e.g. twisted pair, optical fiber — Unguided medium • e.g. air, water, vacuum Terminology (2) • Direct link — No intermediate devices • Pointtopoint — Direct link — Only 2 devices share link • Multipoint — More than two devices share the link Terminology (3) • 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 Sine Wave • Peak Amplitude (A) — maximum strength of signal — volts • Frequency (f) — Rate of change of signal — Hertz (Hz) or cycles per second — Period = time for one repetition (T) — T = 1/f • Phase ( φ ) — Relative position in time Wavelength • Distance occupied by one cycle • Distance between two points of corresponding phase in two consecutive cycles 2200 λ • Assuming signal velocity v λ = vT λ f = v — c = 3*10 8 ms1 (speed of light in free space) Frequency Domain Concepts • Signal usually made up of many frequencies • Components are sine waves • Can be shown (Fourier analysis) that any signal is made up of component sine waves • Can plot frequency domain functions Spectrum & Bandwidth • Spectrum — range of frequencies contained in signal • Absolute bandwidth...
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This note was uploaded on 02/10/2012 for the course CSC 411 taught by Professor Simmons during the Spring '08 term at S. Alabama.
 Spring '08
 Simmons

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