DORDT COLLEGE ENGINEERING DEPARTMENT
INTRODUCTION TO COMMUNICATION SYSTEMS—EGR 363
(Fall 2017)

PROBLEM SETS

(Last update: 12/18/2017 9:09 am)
PS #   Assigned Due Returned Problems Assigned
(In Proakis & Salehi unless otherwise noted)
14

12/07
12/14
12/18
  Topics: Random varables, CDF, PDF, Q-function,
              Functions of RVs, Rand.processes, EX(x)
  Read Section 5.2, review Section 5.1
 
  Do 5.9, 5.10, 5.11, 5.12
  Also, please complete the course evaluation.
  and also this course evaluation.
 
  Hints on 5.11
  Part 3) You can't use Eq. 5.1.11 (Why?) Use
              techniques discussed in class on 12/07
  Part 4) The integral you encounter is not too
              hard. What is (d/dy)(exp(–y2/2σ2))?
  Part 5) You can use Eq. 5.1.11.
 
  Note:
  Problem 5.12 continues in the textbook on p. 239.
13

11/30
12/07
12/12
  Topics: Review FM,
  New topic: Intro to Probability
  Read Section 5.1
 
  Do 4.5, 4.20, 5.1, 5.2, 5.3, 5.5
 
  Note textbook errata on page 163.
  Note textbook errata on page 187, Prob. 4.20.
12

11/21
11/30
12/05
  Topics: Homework on FM, reading and class time
  on probability.
 
  Do 4.1, 4.2, 4.4
 
  Note textbook errata on page 163.
11

11/14
11/16
11/21
  Topics: Review of AM modulation including
  the Hilbert transform. Text Section 2.6 and
  Chapter 3
 
  Do 2.62, 2.65, 3.14, 3.16.
10

11/02
11/09
11/15
  Topics: SSB, QAM, VSB, Superheterodyne
  Read Sections 3.2.4 to end of Chapter 3
 
  Do 3.24 and 3-A (not in textbook)
 
  Note textbook errata on page 163.
9

10/31
11/02
11/15
  Topics: SSB, Hilbert Transform
  Read Sections 3.2.3 and 2.6 (pages 95–98)
 
  Do 3.17
8

10/17
10/26
11/01
  Topics: DSB-LC, Envelope Detection
  Read Section 3.2.2 and pages 141–143 on
  Envelope Detector.
 
  Do 3.11
7

10/04
10/12
10/18
  Topics: Review
 
  Do 2.39, 2.43 part b only
 
  For solutions, see PS#5 and PS#6
6

9/26
10/04
10/10
  Topics: AM defined, DSB-SC, DSB-LC, Spectra of
              and demodulation of the above
  Read Ch 3 Introduction through 3.2.2
 
  Do 2.43 part (b) only, 2.44 using only part (b)
  of 2.43, 3.1, 3.3, 3.5, and note errata on
  pages 151 and 152, also. . .
  Use a computer to plot Eq. 3.2.6 (page 127).
  Let mn(t) = cos(2πfmt) and let a = 0.75, Ac = 10,
  fm = 440 Hz, and fc = 20 kHz. Turn that case
  in for a grade, but use your computer code to
  explore. What happens if a > 1? (try a = 1.2)
  What happens as fc is lowered toward fm?
  Be sure your plots have enough samples. You
  should have at least 10 samples per cycle of
  of cos(2πfct) and you should plot at least one
  cycle of mn(t).
  Use a computer for the plots for Problem 3.3.
  Octave or Matlab are recommended.
 
  Hint for Problem 2.43(b): Follow the style of the
  example on textbook page 53 and note that
  xn can be expressed without any trigonometric
  or complex exponential functions.
  Hint for Problem 2.44. Use Eq. 2.3.57
  on textbook page 79. Also see pages 81 - 82.
  Express each answer as a synthesis of basis
  signals. (A finite summation in each case.)
  Hint for Problem 3.3
 
  Note: On Tuesday, 9/26, we decided in class that future
  homework assignments will be due on Thursdays. The
  due date for this assignment was also changed to the
  Wednesday before Heartland break.
5

9/19
9/26
10/03
  Topics: Fourier Transform, Review Fourier Series
  Read Ch. 2, Sec 2.3, Review Sec. 2.2
 
  Do 2.37 part 2, 2.39, 2.42, and
  also evaluate this integral:
  Integral from minus inf.
        to inf. of {[2exp(-5t) +sin(10(pi)t)]delta(t)}dt
  Also evaluate the convolution x(t)*h(t)
  where x(t)=2exp(-10t)u(t)
  and h(t)=rect(t/2)
4

9/12
9/19
9/26
  Topics: Signals as vectors, Fourier Series
  Read Ch. 2 Section 2.2
 
  Do 2.31, 2.37 part 1 (other parts will be
  assigned later), find [Λ(t)sgn(t)u(t)] ★ u(t)
  where sgn is the signum function and u is the
  unit step function. The open-delta represents
  the unit triangle function and the star
  represents convolution.
 
  Hint on Problem 2.37.1:
  In geometric terms, let αi represent an
  i-dimensional vector. Let βi represent another
  i-dimensional vector. Then the left-hand side
  of the inequality is the dot-product of the two
  vectors. On the right-hand side of the inequality
  one finds the product of the lengths of the
  two vectors. The inequality essentially states
  that the dot-product of two vectors (having
  non-negative elements) is less than or equal to
  the product of the lenghts of the vectors.
  In communucation systems the vectors
  represent discrete-time signals. The "lengths"
  of each signal represent the square-roots of
  the power of each signal.
 
  Optional: For a nice review and a few more
  details, see how Prof. Oppenheim covers
  Convolution in a 50 min. lecture at MIT.
  Lecture 4, Convolution | MIT
  Hint: You can watch it in 25 min. at 2x speed!
3

9/05
9/12
9/14
  Topics: Linearity, convolution
  Review Ch 2 Sec. 2.1; Read Ch 2 Sec. 2.2.
 
  Do 2.7, 2.16, 2.24, 2.34
2

8/29
9/05
9/06
  Topics: Types of signals & systems
  Read: Ch 1 Sec. 1.4, Ch.2 through Sec. 2.1
 
  Do (p. 101) 2.1 (all parts), 2.5, 2.6.
  Use a computer to make the plots for 2.1.
  Octave or Matlab are recommended.
  Here is a m-file to get you started.
  DDB's "Toolbox" files including u.m, rect.m,
  sinc.m and triangle.m can be downloaded as a
  zip archive DDB_TBX.ZIP.
  Hint: At the command line in Octave or Matlab
  type, "help sign" [enter]. Also try
  "help addpath", "help help" and "help exit".
  After file rect.m is on the path-list, note
  what happens when you type "help rect" in the
  command window. Compare to the comments in
  the source file, rect.m.
 
  Note errata on pages 29 and 42, and 101, 102.

  (On 8/31 at 2:27 PM Prof. De Boer moved Problem 2.16
  to the next assignment.)
1

8/29 8/30 ---   Topics: History of and overview of Comm Systems
  Read Chapter 1.
  (There is nothing to turn in.)

Note 1) Homework solutions are usually available one or two class periods after the due date. Click the "returned date" on this page to access the solutions. If the "Returned" date is not a link (is black, not gold) then the solution is not yet posted. Check back later. If you click the link and get a login screen instead of the solutions, log in using your usual courses@dordt username and password. Then use the back icon (or alt-left-arrow on the keyboard) twice to get back to the link on this page and click the link again. The link only works when you are logged in to courses@dordt.

Note 2) Problems sets shown above with no "assigned" date are tentative. More problems might be added, expected due dates might change, but problems shown will eventually be assigned.

Note 3) If you are having difficulty reading the latest version of this page it may have to do with your browser's cached memory. Read this note on cached pages to solve the problem.