Chapter 1. Introduction Husheng Li The University of Tennessee

Course Contents 1.Basics of communications 2.Signals and noise 3.Amplitude modulation 4.Phase and frequency modulations 5.Pulse modulation 6.Analog communication system

Textbook  Communication Systems: An Introduction to Signals and Noise in Electrical Communication, by A. B. Carlson and P. B. Crilly, McGraw Hill, 5 th edition, 2008

Logistics  Homework: 20% (4 problems every Friday; turn in your homework in two weeks)  Midterm and final exams: 40%  Quiz: 15% (will be 5 quizzes)  Experiments: 25%

Office hour and TA  2: :15pm, MWF, MK644  TA: Jingchao Bao,  Course website: go to my personal website

Experiments  Experiment 1: Matlab simulation for amplitude modulations.  Experiment 2: Matlab simulation for frequency and phase modulations.  Experiment 3: USRP hardware board experiment

Concepts  A communication system conveys information from its source to a destination some distance away.  Some concepts: Information, analog, digital, transducer

Elements of Communication Systems  The transmitter involves modulation and coding.  The transmission channel is the medium for communications, which could be wireless, optical or even sound.  The receiver carries out demodulation and decoding

Negative Factors in Communications  Distortion: Waveform perturbation caused by imperfect response of the system to the desired signal itself.  Interference: Contamination by extraneous signals  Noise: Random and unpredictable electrical signals.

Fundamental Limitations  Communications are limited by bandwidth and noise.  Bandwidth: the width of frequency band used for the communications.  Noise: The signal-to-noise ratio (SNR; S/N) is important.  When the noise is Gaussian, the channel capacity is given by

Modulation  Modulation involves two waveforms: a modulating signal and a carrier wave. Modulating signal Amplitude Modulation Pulse train With AM

Coding  Coding is a symbol processing operation for improved communication when the information is digital or can be approximated in the form of discrete symbols (actually there is also analog coding).  Source coding converts source information into a series of bits.  Channel coding: add redundancy to improve the robustness of transmission.

EM Transmission  there are several effects that enable light as well as electromagnetic (EM) waves to propagate around obstructions or beyond the earth’s horizon

Multipath and Fading  In wireless communications, the signal could be received by the receiver after reflections.  The superposition of signals from different paths could strengthen or weaken each other.

Emerging Developments  Circuit / packet switching  Multiple access: TDMA, CDMA, OFDMA.  Ultra-wideband (UWB)  Computer Networks: WiFi (IEEE ) and WiMAX (IEEE )  Software defined radio

Some History (1)

Some History (2)

Some History (3)

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Some History (5)

Some History (6)

Assignment  Read chapter 1