communication systems imwickert/ece5625/lecture_notes/n5625_1.pdf · 1.1. introduction 1.1...

Chapter 1Course Introduction/Overview

Contents

1.1 Introduction . . . . . . . . . . . . . . . . . . . . . . 1-31.2 Where are we in the Curriculum? . . . . . . . . . . . 1-41.3 Where are we (cont.)? . . . . . . . . . . . . . . . . . 1-51.4 Instructor Policies . . . . . . . . . . . . . . . . . . . 1-81.5 Communications Lab Connection . . . . . . . . . . 1-91.6 Software Tools . . . . . . . . . . . . . . . . . . . . 1-101.7 Comm I/Comm II Course Sequence . . . . . . . . . 1-111.8 Course Introduction and Overview . . . . . . . . . . 1-121.9 A Block Diagram . . . . . . . . . . . . . . . . . . . 1-131.10 Channel Types . . . . . . . . . . . . . . . . . . . . . 1-14

1.10.1 Electromagnetic-wave (EM-wave) propaga-tion . . . . . . . . . . . . . . . . . . . . . . 1-14

1.10.2 Guided EM-wave propagation . . . . . . . . 1-181.10.3 Magnetic recording channel . . . . . . . . . 1-181.10.4 Optical channel . . . . . . . . . . . . . . . . 1-18

1-1

CONTENTS

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1-2 ECE 5625 Communication Systems I

1.1. INTRODUCTION

1.1 Introduction

� Where are we in the ugrad and grad curriculum?

� Course Syllabus

� Instructor policies

� Relationship to the communications lab, ECE 4670

� Software tools

� The Comm I/Comm II course sequence

� Communication systems overview

ECE 5625 Communication Systems I 1-3

CONTENTS

1.2 Where are we in the Curriculum?

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1.3. WHERE ARE WE (CONT.)?

1.3 Where are we (cont.)?

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<1 of 2>

ECE 5625/4625Communication Systems I

Spring Semester 2020

Instructor: Dr. Mark Wickert Office: EN292 Phone: [email protected] Fax: 255-3589http://www.eas.uccs.edu/~mwickert/ece5625

Office Hrs: Tue/Thurs 2:15–3:00 PM + 4:20–5:00 PM + other times by appointment

Required Text:

R. Ziemer and W. Tranter, Principles of Communications, seventh edition,Wiley, 2014 (ISBN-13: 978-1118078914). I recommend the e-book version tosave money. I have full course notes available on the course Web Site.

Optional Text:

M.A. Wickert, Signals and Systems for Dummies, Wiley, 2013. Useful for Fou-rier theory review and worked examples, including the use of Python (PyLab).

Optional Software:

Scientific Python via the Jupyter Notebook (installed with https://ana-conda.org/anaconda/python). The ECE PC Lab also has Anaconda installedand Pandoc and MikTeX for PDF output from the notebook. See the secondpage of the syllabus. Mathematica, available to UCCS students (see courseWeb Site), is also very useful.

Grading: 1.) Graded short quizzes and/or homework assignments total 20%.2.) Computer project(s) worth 20%.3.) Two “Hour” exams at 15% each, 30% total.4.) Final exam worth 30%.

Drop Date The last day to drop is April 3, the Friday after Spring break week.

Topics Text Sections

1. Introduction and Course Overview Notes

2. Signal and linear system review and introduction to new top-ics including generalized Fourier series, autocorrelation func-tion, power spectrum, Hilbert transform and sampling theory

2.1–2.8, 2.10

3. Basic modulation techniques: DSB, AM, SSB, and digital-pulse modulation and multiplexing

Chapter 3 + Notes

4. Basic modulation techniques: FM, PM, analog pulse modula-tion, and more multiplexing techniques

Chapter 4 + Notes

5. Baseband digital data transmission and an overview of digital modulation techniques

Chapter 5+ Notes

6. Noise sources and calculations Appendix A

CONTENTS


<2 of 2>

Installing Python & scikit-dsp-comm

Download and Install the Anaconda Python 3.7+ Distribution: https://ana-conda.org/anaconda/python. I recommend you have Anaconda configurepaths to the tools. This is not the default. Jupyter Notebook, QT Console, andJupyter Lab will be installed with the Anaconda distribution. Finish installa-tion on Windows in Powershell by typing: conda init powershell. Follow theJupyter Lab link for more steps on getting this up. Finally, a very good alterna-tive to the full Anaconda is miniconda and the use virtual environments. Wewill talk about this in class, as it can save disk space and make reconfigurationeasier.Download and Install the distributed version control application git: https://git-scm.com/ on Windows systems (included on macOS and Linux). Optionally Download and Install a code development environment that alsointegrates git version control such as Visual Studio Code (VS Code): https://code.visualstudio.com/ or PyCharm Community Edition IDE for Python:https://www.jetbrains.com/pycharm/. Clone and Install the package scikit-dsp-comm by following the GitHubREADME page at: https://github.com/mwickert/scikit-dsp-comm. Maintain scikit-dsp-comm using git pull origin master (see the informa-tion in the GitHub link).

Optional Jupyter Notebook to PDF Conversion

The Jupyter notebook is the perfect place to write code, document code, writetext using markdown, import figures, and typeset math equations usingLaTeX syntax. To render a Jupyter notebook as a PDF document a few moreopen source software components are needed:

• Install Pandoc for file conversion to LaTeX and other formats: https://pandoc.org/index.html

• Install MikTeX for converting LaTeX documents to PDF on Windows:https://miktex.org/

• When installing MikTeX be sure to choose the option to automaticallydownload needed LaTeX packages on-the-fly

• Install TeXLive for converting LaTeX documents to PDF on macOS andLinux: https://www.tug.org/texlive/

• Install Inkscape for converting embedded SVG graphics in Jupyter note-books via Pandoc to LaTeX and then PDF: https://inkscape.org/en/release/0.92.2/. This gives you the ability to have nice looking graphics inthe notebook and easily convert to a PDF, using just the File: DownloadNotebook menu item. On macOS you just install Inkscape. On Windowsyou may have to manually tweak the registry to get Inkscape to properlyconvert SVG graphics to PDF in the notebook conversion process. Whenthis is finally set up it is great.

• Install Typora: As an alternative to installing LaTeX (MikTeX or TeX-Live), install the markdown editor Typora: https://typora.io/. Now youcan export as *.md and then open the file in Typora and save to PDFdirectly. You can also do some nice file editing if need be.

1.3. WHERE ARE WE (CONT.)?


CONTENTS

1.4 Instructor Policies

� Homework papers are due at the start of class

� If business travel or similar activities prevent you from attend-ing class and turning in your homework, please inform me be-forehand

� Grading is done on a straight 90, 80, 70, ... scale with curvingbelow these thresholds if needed

� Homework solutions will be placed on the course Web site inPDF format with security password required; hints pages mayalso be provided


1.5. COMMUNICATIONS LAB CONNECTION

1.5 Communications Lab Connection

� The labs are fairly tightly coupled with the lecture topics

� The communications hardware experience should enhance yourunderstanding of communications theory and analysis

� Lab topics:

– RF spectrum analyzer and network analyzers

– Spectrum Analysis

– Mixers and Amplitude Modulation

– FM Radio Receivers for Analog and Digital Modulation

– Software defined radio and the RTL-SDR

– FieldFox measurement campaign with a log-periodic an-tenna

� Both circuit and subsystem level designs are dealt with, as wellas pre-built radio circuits

� The spectrum analyzer and vector network analyzer are intro-duced to extend measurement capabilities into the frequencydomain


CONTENTS

1.6 Software Tools

� The Jupyter Notebook with PDF export via LaTeX is verygood for writing up solutions to homework and computer projects(HTML and screenshots OK too)

� Analysis aids:

– Python/PyLab (Jupyter Notebook or QT console commandline interface) with NumPy and matplotlib (PyLab), andSciPy very powerful, and free

– Calculator (good practice for exams)

– Additional tools include Mathematica and MATLAB bothfreely available to UCCS students

� Block Level System simulation

– Keysight ADS (used in ECE 4670), MATLAB/Simulink

� Circuit simulation (for lab only?):

– Agilent ADS for circuits, baseband, radio frequency (RF)and systems

– LTspice


1.7. COMM I/COMM II COURSE SEQUENCE

1.7 Comm I/Comm II Course Sequence

� Communication systems I, this course, continues into a sec-ond semester when ECE 4630/5630 is offered alternate fallsemesters

� The second semester course focuses on digital communica-tions

– An introduction to random signals is provided

– Amplitude, Phase, and frequency shift-keyed modulationschemes are studied in considerable detail

– Coherent versus non-coherent modulation

– The Mobile radio channel is introduced

– Satellite communications is introduced

– Coding theory is introduced


CONTENTS

1.8 Course Introduction and Overview

� The theory of systems for the conveyance of information

� Communication systems must deal with uncertainty (noise andinterference)

– The uncertainty aspects of noise require the use of proba-bility, random variables, and random processes

– In this first course deterministic modeling is used for themost part

� Some important dates:

1915 Transcontinental telephone line completed1918 Armstrong superheterodyne radio receiver per-

fected1938 Television broadcasting beginsWW II Radar and microwave systems developed1948 Transistor invented1956 First transoceanic telephone line completed1960 Laser demonstrated1962 First communications satellite, Telstar I1970’s Commercial relay satellites for voice and data1977 Fiber optic communication systems1980 Satellite switchboards in the sky1990’s Global positioning system (GPS) completed1990’s Cellular telephones widely used1998 Global satellite-based cellular telephone system2000s Smart phones2011/2 Long Term Evolution (LTE) 4th-gen. cellular


1.9. A BLOCK DIAGRAM

1.9 A Block Diagram

� A a high level communication systems are typically describedusing a block diagram

Transmitter

Receiver

ChannelInput

Transducer

OutputTransducer

InputMessage

MessageSignal

TransmittedSignal

OutputSignalOutput

Message

ReceivedSignal

Noise and distortion enters the system here

� There is an information source as the input and an informationsink to receive the output

� The block diagram shown above is very general

– The source may be digital or analog

– The transmission may be at baseband or on a radio fre-quency (RF) carrier

– The channel can take on may possible forms


CONTENTS

1.10 Channel Types

1.10.1 Electromagnetic-wave (EM-wave) prop-agation

Skip-wavepropagation

Ground wavepropagation

Line-of-sightpropagation

Earth

Ionosphere

Comm Satellite

Transiosphere (LOS)

� When you think wireless communications this is the channeltype most utilized

� The electromagnetic spectrum is a natural resource

� The above figure depicts several propagation modes

– Lower frequencies/long wavelengths tend to follow theearths surface

– Higher frequencies/short wavelengths tend to propagatein straight lines

� Reflection of radio waves by the ionosphere occurs for fre-quencies below about 100 MHz (more so at night)


1.10. CHANNEL TYPES


CONTENTS

� Examples of public (commercial) and government (militaryapplications and the frequency bands they operate in

� There is a hierarchy of organizations that regulate how theavailable spectrum is allocated

– Worldwide there is the International TelecommunicationsUnion (ITU), which convenes regional and worldwide Ad-ministrative Radio Conferences (RARC & WARC)

– Within the United States we have the Federal Communi-cations Commission (FCC)

� Cellular telephony, wireless LAN (WLAN), and HDTV broad-casting, are examples where the FCC continues to make allo-cation changes


1.10. CHANNEL TYPES

� At frequencies above 1–2 GHz oxygen and water vapor absorband scatter radio waves

� Satellite communications, which use the microwave frequencybands, must account for this in what is known as the link powerbudget

Water vapor

and oxygen

attenuation

Rainfall rate

attenuation

6223 120


CONTENTS

1.10.2 Guided EM-wave propagation

� Communication using transmission lines such as twisted-pairand coax cable

1.10.3 Magnetic recording channel

� Disk drives, fixed (at one time flexible too)

� Video and audio

1.10.4 Optical channel

� Free-space

� Fiber-optic

� CD, DVD, HD-DVD, etc.


1.10. CHANNEL TYPES

Example 1.1: Open Systems Interconnect (OSI) Model

� When dealing with data communications (as in bits/s) the OSImodel of interest

� Both ECE and CS majors have an interest in this

� In this course we are focused on the physical layer


CONTENTS

Example 1.2: Lowcost Software Defined Radio

� Software defined radio (SDR) is an exciting merger of digitalsignal processing and wideband radio hardware 1

� The basic elements of a practical SDR transceiver are shownbelow:

RF/IF A/DD/A

DigitalFront End

Base BandProcessing

SmartAntenna

FlexibleRF

Hardware

ADC

DAC

IF

Channelizationand

Sample RateConversion

Processing

Hardware• FPGAs• DSPs• ASICs

Software• Algorithms• Middleware• CORBA• Virtual Radio Machine

Output

Input

Control

The SDR transceiver concept in block diagram form

� A very popular platform at $20, with a very active user com-munity, is the RTL-SDR2

� The RTL-SDR dongle contains two primary chips: (1) theRaphael Micro R820T radio tuner and the Realtek RTL2832Uwhich contains an 8-bit ADC and USB data pump

R820TTuner

24 MHz – 1850 MHz

ADCUSBDataPump

Obtaining Data SheetRequires NDA

RTL2832UFromAnt.

Noise

USBInterfaceto PC

Figure~3.5 dB

http://rtlsdr.org/

http://www.realtek.com.tw/products/productsView.aspx?Langid=1&PNid=22&PFid=35&Level=4&Conn=3&ProdID=257

http://www.realtek.com.tw/products/productsView.aspx?Langid=1&PNid=22&PFid=35&Level=4&Conn=3&ProdID=257

Interleaved8-bit I&Qsamples

(advertised range)

1http://en.wikipedia.org/wiki/Software-defined_radio2http://rtlsdr.org/


1.10. CHANNEL TYPES

� To better understand the functionality of the RTL-SDR con-sider the behavioral level model shown below:

Q [ ]VGALNA

LPF

Gain Control(maybe automatic

or AGC)

fs 2⁄f– s 2⁄

B 0.8fs≈

0

8-BitADC

ej2πfct–

ctrl

r t( ) s t( )=+ n t( )

FromAnt. fs

Osm

ocom

Driv

ers

r n[ ] rI n[ ] jrQ n[ ]+=

ToPC

2 2 2 2

RTL-SDR USB Dongle

2 = complex signal path

G

A behavioral level model of the RTL-SDR.

� Using your signals and systems background, with an emphasison Fourier theory, even now you can make some sense of howthe receiver works

� The complex multiply by e�j 2�fct and the lowpass filter are thetwo most important system blocks

� In picture form consider:

S f( )Bs

fcf

f– c

Signal of interest spectrumS f( ) F s t( ){ }=

0

shift leftshift left

fcf

f– c0 fs

2---fs2---–

Effective RTL-SDRLowpass Filtering Usable bandwidth ~80% of fs

Frequency translate to ~0 Hz using s t( )ej2πfct–

Spectrum of discrete signal r[n]

= a complex signalFilteringremovesthis

A frequency domain view of the RTL-SDR


CONTENTS

� A fun way to exercise the RTL-SDR is using the free appSDR#:

88.7 MHz (KCME in Colorado Springs)

Standard FM broadcasting

Upper and lower sidebands from an HD radio portion also broadcast over the same carrier

Waterfall plot

Spectrum plot

The SDR# GUI (older version)


1.10. CHANNEL TYPES

Example 1.3: Wireless in the Eye

� A recent publication3 describes a wireless sensor for intra-ocularpressure monitoring in the eye

The wireless sensor

� The device is powered using ambient energy (light in this case)via a rechargeable thin film Li state battery

The system block diagram3“Millimeter Scale Energy Harvesting,” EEPulse, Issue 27, http://www.eeweb.com/


CONTENTS

� The space constraint is 1.5 mm3

� The energy chip stores 1 �Ah, but the device needs 10nW onaverage and 3.65nW when in standby

� Pressure is measured every 15 minutes (needed for Glaucomapatients)

� Energy autonomy is achieved with 10 hours of indoor lightingor 1.5 hours of sunlight per day

The chip layers and the 1�Ah battery


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