Lecture 20: CommunicationsAnnouncementsGrammiesFeedback from Group DiscussionPlan for TodayHW6/Lab6  ProjectPresentation Tips: SlidesOral Presentation TipsIntro to CommunicationsCommunication ChallengesExamples of Analog CommunicationsDigital CommunicationsLecture 20: CommunicationsThe Digital World of MultimediaProf. Mari OstendorfEE299 Lecture 2027 February 2008Announcements Exam etc. Returning graded exam, HW4, quiz3 & other stuff not picked up earlier; last page is record of grades so far Solutions posted tomorrow High = 96, Average = 78 -- GREAT JOB!!! Grade changes: HWs & Labs: show Po-Han your graded HWs Lab3: email me (I may have missed some late docs) Exam: Come to office hours this Friday, or leave me the exam with a note that explains why you deserve more points on a specific problem No office hours for me tomorrow 2/28EE299 Lecture 2027 February 2008Grammies Winner:  Phonecall Honorable mentions: Mysong2 Board_sax If you would like to be credited on the class web page, let me knowEE299 Lecture 2027 February 2008Feedback from Group Discussion Thanks much for your feedback! Things for me to do (this quarter): Add sound files online, put more Matlab demos online Look into how CSE uses MyUW for providing grades (which profs do this?) Talk about why lectures aren’t like homework Things for you to do: Send me anonymous email suggesting fundamentals that would be good to spend more time onEE299 Lecture 2027 February 2008Plan for Today HW6/Lab6 Discussion Intro to CommunicationsEE299 Lecture 2027 February 2008HW6/Lab6 Æ Project Put together a presentation on a paper of your choice from  IEEE Spectrum Signal Processing Magazine Communications Magazine Upload the presentation (ppt or pdf) to CollectIt Prof. Ostendorf will grade this Do the presentation in lab Mar 4 or 6 Your peers will grade you Write a 2-3 page summary due Mar 15EE299 Lecture 2027 February 2008Presentation Tips: Slides Each slide should take about 1.5-2min Îa 10 min talk should have about 5-7 slides Each point you want to make should be on the slides in words (briefly) Don’t have a lot of slides with only words (you must have multimedia) A little animation is good; a lot is distracting. Same with color.Note: You must do computer projection. Use either ppt or pdf.EE299 Lecture 2027 February 2008Oral Presentation Tips Speak clearly & with reasonable volume Look at the audience (not the screen) Know your material Practice with a friend Tell them to let you know if you have distracting nervous habits Have them time each slide, so you know where you are spending too little or too much timeEE299 Lecture 2027 February 2008Intro to Communications Challenges Analog vs. digital Transmission technologies Packet-based communicationEE299 Lecture 2027 February 2008Communication Challenges All communications systems are imperfect Signal is distorted due to Fading Noise (thermal, weather, ….) Interference of other signals (or of other bits in this signal) Mulitpath (echo) Goal is to minimize impact of these problems through Clever design of signals & transmission methods Error detection & correctionEE299 Lecture 2027 February 2008Examples of Analog Communications Let m(t) be the information signal (message) you want to send AM radio (amplitude modulation) Y(t) = Am(t)cos(2πfRt) Frequency shifting to fRregion for transmission, shift back at the receiver FM radio (frequency modulation) Y(t) = Acos[2πfRt + G(m(t))] Trickier frequency shifting Just as for sampling: limiting the bandwidth is important Frequency division multiplexing: combining different signals in different frequency bandsEE299 Lecture 2027 February 2008Digital Communications Sending bits: ultimately the implementation is analog, e.g. 0 vs. 1:  Cos(100t) vs. cos(200t) Pulse vs. no pulse 000, 001, 010, … cos(2πkf0t) So what is the advantage of digital? Small problems can be recovered from perfectly Intermediate detection and retransmission to avoid big