EEE 330Introduction to Communication Systems

Lecture #1

Course Overview

Anouncements

� Course Notes for futures classes will be posted on the class web site

http://www1.gantep.edu.tr/~ogucu/eee330

� What will be available:� Lecture Notes (.pdf)

� Access password: int330

Lecture Overview

� The objectives of today’s lecture are� Explain the course mechanics

� Provide an overview of the course

� Describe the major components of the course

Course

� Instructor� Dr Gölge Öğücü

� Contact Information:� Office: 203, Elektrik-Elektronik Müh. Böl.

A blok

� e-mail: ogucu@gantep.edu.tr

� phone#: 3172113

Required Course Materials

� Textbook:

� No reference textbook is offered. � References:

� B.P. Lathi, Modern Digital and AnalogCommunication Systems, 3rd Ed., Oxford University Press, 1998.

� Mischa Schwartz, Information Transmission, Modulation and Noise, 4th Ed., McGraw-Hill,1990.

� A.B. Carlson, P.B. Crilly, J. C. Rutledge,Communication Systems, 4th Ed., McGraw-Hill, 2002.

Course Components

� The course has two main components:� Lectures – These are meant to introduce the key

concepts in the course and provide you with fundamental understanding. This is the primary source of information in the class. I will provide you with lecture notes on the website typically the weekend before class (no guarantees though). Attending the lectures is absolutely crucial to successfully completing this course!

� Exams – These are meant to show me how well you have grasped the material .

Grading

� Midterm I 30%

� Midterm II 30%

� Final Exam 40%

Course Objectives

� After successfully completing this course the student should� have information about the

telecommunications, types of telecommunication systems,

� be able to explain the operation of the system components, modulation, multiplexing, analog and digital communications, satellite communicaitons

What is Communication?

� Definition: Communication is the transfer of information at one time or location to another time or location.

� Generic Communication System:

Channel

ReceiverTransmitter

Received signal

Transmitted signal

Communication System

Estimate of message signal

User of information

Source of information Message

signal

Fundamental Steps in Communication

1. Generation of message signal: image, voice, music, video

2. Description of the message signal by a set of symbols : electrical, aural, visual

3. Encoding of the symbols in a form suitable for transmission

4. Transmission of the encoded symbols to the desired destination

5. Decoding and reproduction of the original symbols

6. Recreation of the original signal

Primary Communication Resources

� Transmitted power� The average power of the transmitted

signal

� Channel bandwidth� The band of frequencies allocated for the

transmission of the message signal

� band-limited channels� Telephone systems: 300-3100 Hz

� Power-limited channels� Satellite channel

A Communication System� Source of Information

� Information may take many forms: computer data, image, voice, music, video.

� Information can be either analog or digital.� Analog information can also be ‘digitized’.

� Information is defined as the amount of “surprise” at the rx (reciever).

� Transmitter� Processes information and puts it into a form

suitable for transmission� This typically means transforming into an

electromagnetic signal � Can be either ‘baseband’ or ‘bandpass’

A Communication System (Contd.)

� Channel� Relays information between locations (without

perfect fidelity)� Guided propagation and free propagation are

possible.� telephone channels, coaxial cables, optical

fibres� Wireless broadcast channels, mobile radio

channels, satellite channels.

� Receiver� Must reconstruct transmitted information from

the corrupted/received waveform as accurately as possible

A Communication System (Contd.)

� Modulation � Modification of the

message signal by the transmitter in a form suitable for transmission.

� Demodulation� Recreation of the

message signal from received signal (a degraded version of the transmitted signal)

Modulated signal

Message signal

Carrier

Modulation

� Continuous-wave (CW) modulation� A sinusoidal wave is used as the carrier

� Amplitude modulation (AM)� Frequency modulation (FM)� Phase modulation (PM)

� Pulse modulation� Carrier consists of periodic sequence of rectangular

pulses� Analog pulse modulation

� Pulse-amplitude modulation (PAM)� Pulse-duration modulation (PDM)� Pulse-position modulatiob (PPM)

� Digital pulse modulation � Pulse-code modulation (PCM)

Bandpass vs. Baseband

� The information signal or message signal m(t) is a baseband signal, that is it contains energy about D.C. (f = 0)

� The transmitted signal may be at baseband or may be a bandpass signal, that is it contains energy about f = fc where fc >> 0.

� Wireless signals are (almost) always bandpass due to physical antenna limitations whereas wireline signals could be either bandpass or baseband .

� Each wireless application is assigned a specific frequency band in which it can radiate energy. This is one reason why Fourier Transforms (spectral information) are so important in communications.

Examples of Communication Systems

� Broadcast Radio� Music and voice are transmitted from a broadcast station to

large number of receivers (i.e., radios) over the air� Broadcast Television

� Images are transmitted from a broadcast station to a large number of receivers (i.e., TVs) over the air

� Telephone system� Voice (digital data also possible) transmitted from one point to

another point (i.e., one phone to another) through wires (both copper and optical fiber)

� Cellular telephone� Voice (digital data also possible) transmitted from one point to

another point through both wires and over the air� Internet (computer networks)

� Digital data transmitted from one point to another point through wires

� Satellite communication systems� Digital data or voice transmitted from one point to another

point using satellite as an intermediate transmitter/receiver

What Makes a GoodCommunication System

� Good Received Signal Fidelity� Analog System: high Signal-to-Noise Ratio

(SNR)� Digital System: low Bit Error Rate (BER)

� Low Transmit Signal Power� A large amount of information is

transmitted� Signal occupies a small bandwidth� System has a low cost (complexity?)

� Complex digital operations have steadily grown cheaper

� Communications engineers must trade off all of these

Examples of Tradeoffs inCommunications Designs

� Satellite and Deep Space Communications� Power is expensive to generate in space and

transmission distances are enormous – Must be very energy efficient

� Microwave Relay Towers� Power is cheap, but available bandwidth is

restricted by regulation - Must be very bandwidth efficient

� Cellular Phones� Power is costly (impacts battery life and size)

but bandwidth is also limited - Must be both bandwidth and power efficient

Digital vs. Analog Communications

� Digital Communication System� transmit a finite number of signals� text and data are naturally digital information

sources� Analog Communication

� transmit a continuous (uncountably infinite) range of signals

� voice and video are natural analog information sources

� An analog information source can be converted into a digital source by� Sampling the signal in time� Quantizing the signal amplitude to a finite

number of levels

Key Inventions in the History� 1844 Telegraph (Morse)

� Morce code of variable-length ternary code

� 1864 Maxwell’s equations (Maxwell)� Formulation of the electromagnetic

wave propagation� 1875 telegraph code of fixed-length

(Baudot)� Words consists of 5 equal length code

elements� Elements are assigned to two possible

states: a mark or a space (0 or 1 in difital systems)

� 1875 Telephone (Bell)� Real-time transmission of speech by

electrical encoding and replication of sound

� 1894 Wireless Communication (Lodge)� Short distance (150 yards)

� 1897 Automatic Switch (Strowger)� Electromechanical switch

� 1901 Wireless Communication (Marconi)� 1700 miles over Atlantic ocean

� 1918 Practical AM receiver (Armstrong)� Superheterodyne radio receiver

� 1920 First Radio Broadcasts

� 1928 Television (Farnsworth)� 1928 Nyquist criteria (Nyquist)� 1933 FM Radio (Armstrong)� 1936 BBC begins first TV broadcasts� 1937 Pulse-code Modulation (Reeves)� 1948 Information Theory (Shannon)� 1948 Transistor (Brattain, Bardeen,

Shockley)� Electronic switching and digital

communications� 1950 Digital Long Distance Telephone

Lines (Bell Labs)� 1962 Telstar I communication satellite

(Bell Labs)� 1979 First commercial cellular

telephone (Motorola/AT&T)� 1990 Second Generation (Digital)

cellular systems (TDMA)� 1993 CDMA Cellular systems� 2002 - Third Generation� Cellular Systems

Electromagnetic Spectrum

To Study Communication Systemsyou must understand…

� Signals and Systems� Fourier Analysis� Modulation Theory� Detection Theory

� Given that this signal is corrupt at the receiver, how do we determine the original signal?

� Probability Theory� Since the transmit signal and noise are both

unknown to the receiver, we can use probability theory to study communications systems