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EE 179: Introduction to Communications

EE 179: Introduction to Communications. Professor Andrea Goldsmith. Outline. Course Information and Policies Course Syllabus Communication Systems Today Future Systems Design Challenges. Course Information (see web or handout for more details).

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EE 179: Introduction to Communications

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  1. EE 179: Introduction to Communications Professor Andrea Goldsmith

  2. Outline • Course Information and Policies • Course Syllabus • Communication Systems Today • Future Systems • Design Challenges

  3. Course Information(see web or handout for more details) • Instructor: Andrea Goldsmith, Packard 371, andrea@ee, Ext: 56932, OHs: MW 12-1pm and by appt. • Class Homepage: www.stanford.edu/class/ee179 • TA: Nathan Klejwa, nklejwa@stanford.edu, Ohs: T 7-8 pm, W 6-7 pm, Th 10-11 am,Packard 100. Email OHs: W 8-9 pm. • Class mailing list: ee179-students (automatic for registered students), ee179-staff for instructor/TAs, guest list available • Discussion Section: T 6-7pm, room TBD. • Book: An Introduction to Analog and Digital Communications • Grading: HWs 30%, Midterm 30%, Final 40% • Prerequisites: EE102a or equivalent

  4. Class Policies • Exam policy: • Exams must be taken at their scheduled times. • Exceptions only in very rare circumstances. • Midterm: 2/17 from 11 am -12:30 pm • Final: 3/20 from 8:30-11:30am. • HW policy: • Assigned Wednesday, due following Thursday. Lose 25% credit per day late. • Up to 3 students can collaborate on 1 writeup. All collaborators must work out all problems.

  5. Course Syllabus • Communication Systems Today (1) • Key Concepts in Communications (2) • Fourier Review and Examples (2) • Energy/Power Spectral Density/Autocorrelation (2) • Probability (4) • Random Processes and Signals (3) • Amplitude Modulation (4) • Frequency Modulation (2) • Digital Modulation (3) • Course Summary and Hot Topics (1)

  6. Communication Systems • Provide for electronic exchange of multimedia data • Voice, data, video, music, email, web pages, etc. • Communication Systems Today • Radio and TV broadcasting (covered later in the course) • Public Switched Telephone Network (voice,fax,modem) • Cellular Phones • Computer networks (LANs, WANs, and the Internet) • Satellite systems (pagers, voice/data, movie broadcasts) • Bluetooth

  7. Local Switching Office (Exchange) Local Switching Office (Exchange) PSTN Design • Local exchange • Handles local calls • Routes long distance calls over high-speed lines • Circuit switched network tailored for voice • Faxes and modems modulate data for voice channel • DSL uses advanced modulation to get 1.5 Mbps Long Distance Lines (Fiber) Fax Modem Local Line (Twisted Pair)

  8. BASE STATION Cellular System Basics • Geographic region divided into cells • Frequencies/timeslots/codes reused at spatially-separated locations (analog systems use FD, digital use TD or CD) • Co-channel interference between same color cells. • Handoff and control coordinated through cell base stations

  9. BS BS BS MTSO MTSO Cell Phone Backbone Network San Francisco New York PSTN Internet

  10. 0101 0101 1011 1011 Local Area Networks (LANs) • LANs connect “local” computers • Breaks data into packets • Packet switching (no dedicated channels) • Proprietary protocols (access,routing, etc.) 01011011 01011011

  11. Wireless Local Area Networks (WLANs) 1011 0101 01011011 Internet Access Point • WLANs connect “local” computers (100m range) • Breaks data into packets • Channel access is shared (random access) • Backbone Internet provides best-effort service

  12. Many WLAN cards have all 3 standards Wireless LAN Standards • 802.11b (Old Generation) • Standard for 2.4GHz ISM band (80 MHz) • Direct sequence spread spectrum • Speeds of 1.6-10 Mbps, approx. 500 ft range • 802.11a (Somewhat New Generation) • Standard for 5GHz NII band (300 MHz) • OFDM with time division • Speeds up to 54 Mbps, approx. 100 ft range • Similar to HiperLAN in Europe • 802.11g (New Generation) • Standard in 2.4 GHz band • OFDM • Speeds up to 54 Mbps, approx. 200 ft range

  13. 1011 0101 Wide Area Networks: The Internet Internet 01011011 Bridge LAN MAN Bridge LAN Satellite and Fiber Lines • Many LANs and MANs bridged together • Universal protocol: TCP/IP (packet based). • Guaranteed rates or delays cannot be provided. • Hard to support user mobility. • Highly scalable and flexible topology

  14. Satellite Systems • Cover very large areas • Different orbit heights • GEOs (39000 Km) versus LEOs (2000 Km) • Optimized for one-way transmission • Radio (XM, DAB) and movie (SatTV) broadcasting • Most two-way systems struggling or bankrupt • Expensive alternative to terrestrial system

  15. Paging Systems • Broad coverage for short messaging • Message broadcast from all base stations • Simple terminals • Optimized for 1-way transmission • Answer-back hard • Overtaken by cellular

  16. Bluetooth • Cable replacement for electronic devices • Cell phones, laptops, PDAs, etc. • Short range connection (10-100 m) • 1 data (721 Kbps) and 3 voice (56 Kbps) channels • Rudimentary networking capabilities

  17. ZigBee Radios • Low-Rate WPAN • Data rates of 20, 40, 250 Kbps • Star clusters or peer-to-peer operation • Support for low latency devices • Very low power consumption • Frequency of operation in ISM bands Focus is primarily on radio and access techniques

  18. Ultrawideband Radio (UWB) • UWB is an impulse radio: sends pulses of tens of picoseconds(10-12) to nanoseconds (10-9) • Low probability of detection • Duty cycle of only a fraction of a percent • Uses a lot of bandwidth (GHz) • Very high data rates, up to 100 Mbps • Low range, 10m or less, due to power restriction.

  19. Future Systems Ubiquitous Communication Among People and Devices Nth Generation Cellular Nth Generation WLANs Nth Generation Internet Wireless Entertainment Sensor Networks Smart Homes/Appliances Automated Cars/Factories Telemedicine/Learning All this and more…

  20. Ad-Hoc Networks • Peer-to-peer communications. • No backbone infrastructure. • Routing can be multihop. • Network topology is dynamic.

  21. Nodes powered by nonrechargeable batteries Data flows to centralized location. Low per-node rates but up to 100,000 nodes. Data highly correlated in time and space. Nodes can cooperate in transmission, reception, compression, and signal processing. Sensor NetworksEnergy is the driving constraint

  22. Distributed Control over Wireless Links Automated Vehicles - Cars - UAVs - Insect flyers • Packet loss and/or delays impacts controller performance. • Controller design should be robust to network faults. • Joint application and communication network design.

  23. Design Challenges • Hardware Design • Precise components • Small, lightweight, low power • Cheap • High frequency operation • System Design • Converting and transferring information • High data rates • Robust to noise and interference • Supports many users • Network Design • Connectivity and high speed • Energy and delay constraints

  24. Main Points • Communication systems send information electronically over communication channels • Many different types of systems which convey many different types of information • Design challenges include hardware, system, and network issues • Communication systems recreate transmitted information at receiver with high fidelity • Focus of this class is design and performance of analog and digital communication systems

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