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TCOM 551 DIGITAL COMMUNICATIONS

TCOM 551 DIGITAL COMMUNICATIONS. FALL 2009 IN 134 Tuesdays 4:30 – 7:10 p.m. Dr. Jeremy Allnutt jallnutt@gmu.edu. General Information - 2. Course Outline

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TCOM 551 DIGITAL COMMUNICATIONS

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  1. TCOM 551DIGITAL COMMUNICATIONS FALL 2009 IN 134 Tuesdays 4:30 – 7:10 p.m. Dr. Jeremy Allnutt jallnutt@gmu.edu Lecture number 1

  2. General Information - 2 • Course Outline • Go to http://telecom.gmu.eduand click oncourse schedule or go to http://ece.gmu.edu/ and go to “courses” and “Course web pages”; select TCOM 551 • Bad weather days: call (703) 993-1000 • Textbook: no mandatory requirement. The Kolimbiris book is very useful. The Bateman book provides additional information • Mathematical Calculator – simple ones only Lecture number 1

  3. General Information - 3 • Homework Assignments • Feel free to work together on these, BUT • All submitted work must be your own work • Web and other sources of information • You may use any and all resources, BUT • You must acknowledge all sources • You must enclose in quotation marks all parts copied directly – and you must give the full source information Lecture number 1

  4. No double jeopardy General Information - 4 • Exam and Homework Answers • For problems set, most marks will be given for the solution procedure used, not the answer • So: please give as much information as you can when answering questions: partial credit cannot be given if there is nothing to go on • If something appears to be missing from the question set, make – and spell out clearly – assumptions used to find the solution Lecture number 1

  5. Double-line space, Times New Roman, 12 font size, default margins. References: must be with source information – listed either as footnotes or tabulated at the end General Information - 5 • Term Paper • Any topic in field of Digital Communications • About 10 pages long + about 4 figures • Can work alone or in small groups (length of paper grows with number in group – with permission only) • There will be no specific points given for the paper, but it can help (or ruin) your grade Possible Topics? Lecture number 1

  6. General Information – 6A • Examples of Term Paper Topics • TDMA vs. CDMA in various situations • LD-CELP: what is it and how does it help? • What is net-centric communications? • Digital Imaging and its impact on sports casting • DBS: why did digital succeed where analog failed • What is a smart antenna and how will it help? • UWB applications • Bluetooth vs. IEEE 802.11B And Lecture number 1

  7. General Information – 6B • Examples of Term Paper Topics (Contd.) • MPEG2: what is it and how does it help? • Why has MPEG-4 taken the lead in video streaming? • Where to next with DVD’s? • Consequences of combining RFID with GPS • Is free-space optical communications for real? • What are the comparative merits of different large screen displays (LCD, DLP, Plasma, etc.)? • Talking appliances? Etc.!!! Lecture number 1

  8. General Information - 7 • Class Grades • Emphasis is on overall effort and results • Balance between homework, tests, final exam; plus term paper: • Homework - 15% • Tests - 30 + 30% • Final exam - 25% • Term Paper - 0% Lecture number 1

  9. Term Paper Grade Percentage – 1 • Contribution of paper to final grade (a) • No mark will be allocated towards the paper. The paper will be graded as quintuple plus (5+), through dot (·), to quintuple minus (5–). A student with a final grade close to the borderline between two grades may be moved up across the borderline if his/her paper is ≥ +++A soft copy and a hard copy shall be submitted Lecture number 1

  10. Term Paper Grade Percentage – 2 • Contribution of paper to final grade (b) • (i) A student who does not hand in an adequate paper by the final exam without prior permission will have his/her final exam score reduced by half • (ii) A student who hands in their paper late, even with permission, will not have their paper considered for a “grade shift” Lecture number 1

  11. Term Paper Grade Percentage – 3 • PLAGIARISMI plan on using search software on the term papers, so please: • No more than 40% by content directly from the web • All quoted content should be inside quotation marks • Every source should be acknowledged in the paper at the point of usage. Lecture number 1

  12. Another alternative http://ece.gmu.edu/coursepages.htm TCOM 551 & ECE 463 Course Plan • Go to http://telecom.gmu.edu,click on course schedule, scroll down to TCOM 551 • In-Class Tests scheduled for - October 6th - November 17th • In-Class Final exam scheduled for - December 15th Lecture number 1

  13. TCOM 551 GTA Information • The TA is TBD • Email address is: TBD • Office Hours in room TBD of the new engineering building are: • TBD;TBD p.m. • Please Email the TA if you would like to meet with him/her. Lecture number 1

  14. TCOM 551 & ECE 463 Lect. 1 Outline • Sine Wave Review • Frequency, Phase, & Wavelength • Logarithms and dB (decibel) notation • Core Concepts of Digital Communications • Source info., Carrier Signal, Modulation • C/N, S/N, and BER • Performance & Availability Lecture number 1

  15. TCOM 551 & ECE 463 Lect. 1 Outline • Sine Wave Review • Frequency, Phase, & Wavelength • Logarithms and dB (decibel) notation • Core Concepts of Digital Communications • Source info., Carrier Signal, Modulation • C/N, S/N, and BER • Performance & Availability Lecture number 1

  16. Sine Wave Review – 1A We all know that the Sine of an angle is the side opposite to the angle divided by the hypotenuse, i.e. B Sine (a) = A/B A Angle a Point P Lecture number 1

  17. Sine Wave Review – 1B We all know that the Sine of an angle is the side opposite to the angle divided by the hypotenuse, i.e. B Sine (a) = A/B A Angle a But what happens if line B rotates about Point P? Point P Lecture number 1

  18. Sine Wave Review – 2A The end of Line B will describe a circle about Point P B a Point P Lecture number 1

  19. Sine Wave Review – 2B The end of Line B will describe a circle about Point P B a What happens if we now shine a light from the left and project the shadow of the end of line B onto a screen? Point P Lecture number 1

  20. Sine Wave Review - 3 End of “B” projected onto the screen B a Point P Light from the left Screen on the right Lecture number 1

  21. Sine Wave Review – 4A End of “B” projected onto the screen As line “B” rotates about the center point, P, the projected end of line “B” oscillates up and down on the screen. The end of line “B” moves up and down with what is called Simple Harmonic Motion, Screen on the right Lecture number 1

  22. Sine Wave Review – 4B End of “B” projected onto the screen Simple Harmonic Motion is an oscillation, or a rotational movement, about a mean value (center) that is periodic.What happens if we move the screen to the right and ‘remember’ where the projected end of “B” was? Screen on the right Lecture number 1

  23. Sine Wave Review – 5A Locus of “B” end-point We have a Sine Wave! One oscillation = One wavelength,  a.k.a. SHM ScreenPosition 1 ScreenPosition 2 Lecture number 1

  24. Sine Wave Review – 5B Remember:Sine 0 = 0; Sine 90 = 1; Sine 180 = 0; Since 270 = -1; Sine 360 = Sine 0 = 0 +1 0 90 180 270 360 Degrees -1 Lecture number 1

  25. Sine and Cosine Waves – 1 SineWave Sine Wave = Cosine Waveshifted by 90o 0o 90o 180o 270o 0 = 360o 90o 180o CosineWave Lecture number 1

  26. Sine and Cosine Waves – 2 • There is a useful java applet that will show you a sine wave derived from circular motion (simple harmonic motion) • The applet is found at:http://home.covad.net/alcoat/sinewav.htm It is very slow to load: have patience! Lecture number 1

  27. Sine and Cosine Waves – 3 • Another applet that lets you ‘play’ with two sine waves to see the combined waveform is: http://www.udel.edu/idsardi/sinewave/sinewave.html Lecture number 1

  28. For more details on Sine Waves Sine and Cosine Waves – 4 SineWave Sine Wave = Cosine Waveshifted by 90o 0o 90o 180o 270o 0 = 360o 90o 180o CosineWave Lecture number 1

  29. http://en.wikipedia.org/wiki/Image:Sine_Cosine_Graph.png Sine and Cosine Waves – 5 Lecture number 1

  30. Sine and Cosine Waves – 6 • Any wave that is periodic (i.e. it repeats itself exactly over succeeding intervals) can be resolved into a number of simple sine waves, each with its own frequency • This analysis of complex waveforms is part of the Fourier Theorem • You can build up a complex waveform with harmonics of the fundamental frequency Lecture number 1

  31. http://www.sfu.ca/sonic-studio/handbook/Harmonic_Series.html Harmonics – 1 A harmonic is a multiple of a fundamental frequency. In the figure below, a fundamental frequency of 100 Hz is shown with 31 harmonics (total of 32 “lines”). Lecture number 1

  32. http://www.sfu.ca/sonic-studio/handbook/Law_of_Superposition.htmlhttp://www.sfu.ca/sonic-studio/handbook/Law_of_Superposition.html Harmonics – 2 In this example, 20 harmonics are mixed together to form a saw-tooth waveform Lecture number 1

  33. Sine and Cosine Waves - 7 Sine and Cosine waves can therefore be considered to be at right angles, i.e. orthogonal, to each other “Cosine Wave” Sine Wave Lecture number 1

  34. Sine and Cosine Waves - 8 • A Radio Signal consists of an in-phase component and an out-of-phase (orthogonal) component • Signal, S, is often written in the generic formS = A cos  + j B sin  Where j = ( -1 ) In-phase component Orthogonal component We will only consider Real signals Real Imaginary Lecture number 1

  35. Sine and Cosine Waves - 9 • Two concepts • The signal may be thought of as a time varying voltage, V(t) • The angle, , is made up of a time varying component,  t, and a supplementary value, , which may be fixed or varying • Thus we have a signalV(t) = A cos (t +) Lecture number 1

  36. Sine and Cosine Waves - 10 Vary these to Modulate the signal • Time varying signalV(t) = A cos (t +) Phase: PM; PSK Instantaneous value of the signal Frequency: FM; FSK Amplitude: AM; ASK Note:  = 2  f Lecture number 1

  37. Back to our Sine Wave – 1ADefining the Wavelength The wavelength is calculated between any two points on the wave where it repeats itself   Lecture number 1

  38. Back to our Sine Wave – 1BDefining the Wavelength Measuring between the peaks or the “zero crossings” is often used: However:   Lecture number 1

  39. Back to our Sine Wave – 1CDefining the Wavelength The wavelength is usually defined at the “zero crossings” since these points are more precise than anywhere else  Lecture number 1

  40. Back to our Sine Wave - 2 One revolution = 360oOne revolution also completes one cycle (or wavelength) of the wave.So the “phase” of the wave has moved from 0o to 360o (i.e. back to 0o ) in one cycle.The faster the phase changes, the shorter the time one cycle (one wavelength) takes Lecture number 1

  41. Back to our Sine Wave – 3Two useful equations The time taken to complete one cycle, or wavelength, is the period, T.Frequency is the reciprocal of the period, that isf = 1/T  Phase has changed by The rate-of-change of the phase, d/dt, is the frequency, f. Lecture number 1

  42. Before we look at d/dt, lets look at rate-of-change of phase Sine Wave – 4 • What do we mean “Rate-of-change of phase is frequency”? • One revolution = 360o = 2 radians • One revolution = 1 cycle • One revolution/s = 1 cycle/s = 1 Hz • Examples: • 720o/s = 2 revolutions/s = 2 Hz • 18,000o/s = 18,000/360 revs/s = 50 revs/s = 50 Hz  Lecture number 1

  43. http://www.sfu.ca/sonic-studio/handbook/Simple_Harmonic_Motion.htmlhttp://www.sfu.ca/sonic-studio/handbook/Simple_Harmonic_Motion.html Simple Harmonic Motion “Geometric derivation of simple harmonic motion. A point p moves at constant speed on the circumference of a circle in counter-clockwise motion. Its projection OC on the vertical axis XOY is shown at right as a function of the angle q. The function described is that of a sine wave.” From the URL above Lecture number 1

  44. d/dt Digression - 1 Person walks 16 km in 4 hours.Velocity = (distance)/(time)Therefore, Velocity = 16/4 = 4 km/hVelocity is really the rate-of-change of distance with time.What if the velocity is not constant? kilometers 1612840 0 1 2 3 4 5 6 7 8 9Time, hours Lecture number 1

  45. d/dt Digression - 2 kilometers You can compute the Average Velocity using distance/time,(i.e. 16/8 = 2 km/h), but how do you get the person’s speed at any particular point? 1612840 0 1 2 3 4 5 6 7 8 9Time, hours Answer: you differentiate, which means you find the slope of the line. Lecture number 1

  46. d/dt Digression - 3 kilometers To differentiate means to find the slope at any instant.The slope of a curve is given by the tangent at that point, i.e., A/BIn this case, A is in km and B is in hours. It could equally well be phase, , and time, t. 1612840 A B 0 1 2 3 4 5 6 7 8 9Time, hours Lecture number 1

  47. d/dt Digression - 4 • When we differentiate, we are taking the smallest increment possible of the parameter over the smallest interval of (in this case) time. • Small increments are written ‘d’(unit) • Thus: the slope, or rate-of-change, of the phase, , with time, t, is written as d/dt Lecture number 1

  48. Sine Wave Continued • Can think of a Sine Wave as a Carrier Signal,i.e. the signal onto which the information is loaded for sending to the end user • A Carrier Signal is used as the basis for sending electromagnetic signals between a transmitter and a receiver, independently of the frequency Lecture number 1

  49. Carrier signals – 1 • A Carrier Signal may be considered to travel at the speed of light, c, whether it is in free space or in a metal wire • Travels more slowly in most substances • The velocity, frequency, and wavelength of the carrier signal are uniquely connected byc = f  Wavelength Velocity of light Frequency Lecture number 1

  50. Carrier signals – 2 • Example • WAMU (National Public Radio) transmits at a carrier frequency of 88.5 MHz • What is the wavelength of the carrier signal? • Answer • c =(3×108) m/s = f ×= (88.5  106) × () • Which gives  = 3.3898 m = 3.4 m Remember: Make sure you are using the correct units Lecture number 1

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