Chapter 1. IntroductionHusheng LiThe University of Tennessee

Course Contents1. Basics of communications2. Signals and noise3. Amplitude modulation4. Phase and frequency modulations5. Pulse modulation6. Analog communication system

TextbookCommunication

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

LogisticsHomework: 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 TA2:15 --- 3:15pm, MWF, MK644TA: Jingchao Bao, jbao2@utk.eduCourse website: go to my personal website http://web.eecs.utk.edu/~husheng/

ExperimentsExperiment 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 LimitationsCommunications 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.

Modulatingsignal

AmplitudeModulation

Pulse trainWith AM

CodingCoding 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 DevelopmentsCircuit / packet switchingMultiple access: TDMA, CDMA, OFDMA.Ultra-wideband (UWB)Computer Networks: WiFi (IEEE 802.11) and

WiMAX (IEEE 802.16)Software defined radio

Some History (1)

Some History (2)

Some History (3)

Some History (4)

Some History (5)

Some History (6)

AssignmentRead chapter 1