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9781423901402_PPT_Ch08

# 9781423901402_PPT_Ch08 - Information Technology in Theory...

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Chapter 8 Fundamentals of Communications Information Technology in Theory By Pelin Aksoy and Laura DeNardis

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2 Objectives Understand how binary streams are physically generated Learn how carriers are modulated to carry the binary streams Understand important transmission concepts, including attenuation, bandwidth, channel capacity, and multiplexing Information Technology in Theory
3 Objectives (continued) Learn the properties of different types of transmission media Identify sources of transmission errors and learn about error detection and correction techniques for digital transmission systems Information Technology in Theory

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4 Electrical Signaling Electrical signals transmitted through conducting materials, such as metal wires, effectively transmit both analog and digital information Metallic conductors , such as copper wires, comprise atoms with loosely attached electrons, or negatively charged particles, around their nuclei Information Technology in Theory
5 Electrical Signaling (continued) When a voltage/potential difference from an electrical source, such as a battery, is introduced between the two ends of a conductor, the electrons are stimulated to move within the metal from one atom to another The relationship between voltage (V), current (I), and resistance (R) is defined by Ohm’s Law : V = IR Information Technology in Theory

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6 Electrical Signaling (continued) Information Technology in Theory
7 Analog and Digital Signaling When analog signals are transmitted across a conductor, a continuous voltage difference proportional to the amplitude of the analog signal is applied at the input of the communications circuit The current flowing through the circuit is proportional to the applied voltage according to Ohm’s law, as there is a resistance associated with the circuit Information Technology in Theory

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8 Analog and Digital Signaling (continued) One method for sending digital information across a communication system is called binary signaling An alternative method to sending digital information across a communication system is 4-ary signaling The 4-ary signaling may be generalized to M-ary signaling The data rate (D) in bits per second for M-ary transmission can be calculated by the following: D = R log2M Information Technology in Theory
9 Analog and Digital Signaling (continued) Information Technology in Theory

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10 Analog and Digital Signaling (continued) Information Technology in Theory
11 Analog and Digital Signaling (continued) Information Technology in Theory

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12 Analog and Digital Signaling (continued) Problem : Calculate the data rate for a communication system that employs 8-ary signaling if the signal transmission rate is 1000 signals per second R = 1000 signals per second M = 8 According to the equation: D = R log 2 M = 1000 log 2 8 = 1000 × 3 = 3000 bps = 3 Kbps The data rate is therefore 3 Kbps Information Technology in Theory
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