8/22/17 COMP 635: WIRELESS & MOBILE COMMUNICATIONS COURSE INTRODUCTION http://wireless.web.unc.edu Jasleen Kaur Fall 2017 1 Introductions q Names q BS/MS, First-year Grad, Senior Grad? q If you’re new, where have you come from? q Your CS interests? q Why this course? q What are you expecting to learn from this course? 2 1
8/22/17 “Wireless” vs. “Mobile” q Two aspects of mobility: Ø User mobility: § Users can communicate “anytime, anywhere, with anyone” Ø Device portability: § Devices can connect anytime, anywhere to the “network” q Wireless vs. mobile Examples û û Stationary computer û ü Notebook on a hotel Ethernet ü û Wireless LANs in historic buildings ü ü Personal Digital Assistant (PDA) Our focus: wireless (including non-mobile) 3 THE IMPORTANCE OF WIRELESS COMMUNICATION Why Should We Care? 4 2
8/22/17 Explosion of User Base 100.0 Mobile cellular telephone subscriptions 90.0 Fixed-telephone subscriptions Active Mobile-broadband subscriptions 80.0 Fixed broadband subscriptions 70.0 Internet Users 60.0 50.0 40.0 30.0 20.0 10.0 - 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015* ~ 7 billion current mobile phone service subscriptions è more than 96% of world population ! Explosive growth in developing countries 5 Benefits of Wireless q Unrestricted mobility Ø Unplugged from power outlet q Significantly lower cost Ø No cable, low labor cost, low maintenance q Ease Ø Minimum infrastructure - scatter and play q Ubiquity Ø Available everywhere like water/air - holy grail 90% of world’s populated areas (in 2011) covered by a mobile cellular network ! 6 3
8/22/17 Example Application Environments q Personal communication q Replacement of fixed networks Ø Access to remote areas Ø Sensors in difficult terrains (weather, earth activities) Ø Flexibility for trade shows Ø LANs in historic buildings 7 Location-based Services: Opportunities q Location aware services Ø Resource-discovery, e.g., printer, fax, phone, server etc. q Follow-me services Ø Call-forwarding, mobile desktop q Information services Ø “push”: e.g., current special offers in the supermarket Ø “pull”: e.g., where is the Black Forrest Cheese Cake? q Privacy services Ø Who should gain knowledge about the location? Ø What information should environment gain about you? 8 4
8/22/17 Example Application Environments q Vehicular Traffic: Ø Personal communication using GSM/UMTS Ø News, road condition, weather, music via DAB/DVB-T Ø Position via GPS Ø Local ad-hoc network with vehicles close-by § To prevent accidents, guidance system, redundancy Ø Transport networks (buses, trains) q Emergencies Ø Early transmission of patient data to the hospital § Current status, first diagnosis Ø Quick replacement of a fixed infrastructure in case of earthquakes, hurricanes, fire etc. Ø Crisis, war, ... § Only wireless ad-hoc networks survive 9 Example Application Environments q Traveling salesmen/employee Ø Access to central (consistent) customer database Ø Mobile office Ø Location-aware services (call-forwarding, hotel printer) q Entertainment, education, ... Ø Outdoor Internet access Ø Intelligent travel guide with up-to-date location- dependent information Ø Ad-hoc networks for multi user games 10 5
8/22/17 Example Application Environments q Wireless sensing Ø Using RF signals for geolocation Ø Using RF signals to sense physical objects § Even behind walls Ø “Piggy-back” RF signals for no-power communication Ø … 11 Explosion of Mobile Devices Laptop/Notebook PDA Pager • fully functional • graphical displays • receive only • standard applications • character recognition • tiny displays • simplified WWW • simple text messages Sensors, embedded controllers Smartphone • tiny keyboard Mobile phones • simple versions • voice, data of standard applications • simple graphical displays www.scatterweb.net performance No clear separation between device types possible (e.g. smart phones, embedded PCs, …) 12 Prof. Dr .-Ing. JochenH. Schiller www.jochenschiller .de MC - 2009 6
8/22/17 Explosion of Technologies q Wide-area communications (cellular, satellite-based): Ø GSM, AMPS, UMTS, cdma2000, DAB, DVB-T q Wireless LANs: Ø 802.11x series Ø Small-to-medium range, higher bit-rates q Short-range: Ø Bluetooth Ø Low bit-rates ITU efforts for standardization/convergence Mobile communications greatly influenced by merging of telecommunications and computer networks 13 The Future Internet QuickTime™ and a are needed to see this picture. decompressor 14 Courtesy: Romit Roy Choudhary, Duke University 7
8/22/17 WHAT’S DIFFERENT ABOUT WIRELESS SYSTEMS? What Issues are Unique to These? 15 Mobile Devices: Unique Issues q Power consumption Ø Low quality displays, small disks due to limited battery Ø Limited compute power: CPU power consumption ~ CV 2 f § C: internal capacity, reduced by integration § V: supply voltage, can be reduced to a certain limit § f: clock frequency, can be reduced temporally q Limited memory Ø Limited usage of mass memories with moving parts Ø Flash-memory as alternative q Limited user interfaces Ø Compromise between size of fingers and portability Ø Integration of voice recognition, abstract symbols q Loss of data Ø E.g., errors, theft 16 8
8/22/17 Wireless Networks: Unique Issues q Providing seamless support for mobility Ø Without disrupting users or applications q Signal propagation: Ø Signal attenuation (as signal propagates) § How long should the “wireless link” be? Ø Higher loss-rates due to interference § Emissions of engines, lightning § How to ensure reliability of “wireless link”? q Frequency-usage: Ø Restrictive regulations of frequencies § Useful frequencies are almost all occupied Ø Spatial reuse (facilitated by signal attenuation) § How to reuse frequency spectrum? 17 Wireless Networks: Unique Issues q Constraints on performance: Ø Low transmission rates (few Mbps) Ø Higher delays, higher jitter § Connection setup time: GSM (seconds), others (ms) q Exploiting/dealing with diversity / dynamism: Ø Antenna selection, Time diversity, Frequency selection q Energy conservation: Ø Wireless devices often battery-powered q Security-related issues: Ø Lower security, simpler active attacking § Radio interface accessible for everyone § Base station can be simulated (attracting mobile calls) Ø Broadcast medium è easier to snoop or tamper with § How to provide integrity and privacy? 18 9
8/22/17 WHAT IS THIS COURSE ABOUT? Syllabus and Structure 19 Impact of Wireless on the Layer Model Application layer service location new/adaptive applications multimedia Transport layer congestion/flow control quality of service Network layer addressing, routing device location hand-over Data link layer authentication media access/control multiplexing encryption Physical layer modulation interference attenuation frequency 20 Prof. Dr .-Ing. JochenH. Schiller www.jochenschiller .de MC - 2009 10
8/22/17 Course Syllabus q Background: Ø Physical Layer (modulation, interference, attenuation) Ø MAC Protocols (coordinated access, random access) Ø Mobile IP Ø Ad-hoc Routing Protocols Ø TCP in Wireless q Recent proposals: Ø Enhance physical performance, make MAC more efficient, provide seamless mobility, … Focus: protocol and physical mechanisms for optimal performance 21 Course Structure q Initial set of lectures (by me): Ø Will cover all background material q Review of recent publications Ø Paper presentations (by you) Ø Critical reviews (by you) q Semester-long projects (groups of 2 welcome) Ø Topics: investigating, designing something new § Experimental study § Formal analysis § Design and evaluation of new mechanism Ø Preferably on one of the focus topics for this course § Unless motivated by strong interest in other topics 22 11
8/22/17 Example Project Types q Project topics: investigating or designing something Ø Experimental study § Characterization of traffic generated by a popular app § Simulator-based comparison of two protocols § Measurement of a WiFi deployment § Wireless trace analysis Ø Formal analysis § Expanding on the analysis of a paper you’ve read Ø Design and evaluation of new mechanisms/application § How best to use all sensors in a smartphone to best manage (communication in) a dream app § How best to use network & cloud to support a dream app § Bandwidth estimation on wireless “links” § Localization using signal strengths 23 Course Grading q Paper Presentations: 25% q Critical Reviews: 20% q Projects (groups of 2 are welcome): Ø Progress: 30% Ø Presentation + report: 10% q Final Exam (oral): 15% q Class Participation: Ø Will be used to potentially bump up (or down) half a grade q All percentage points above are flexible by 5-10% 24 12
8/22/17 References For Background Material q Several reputable texts for background material: Ø Jochen Schiller, “Mobile Communications”. Ø William Stallings, “Wireless Communications & Networks”. Ø Theodore S. Rappaport, “Wireless Communications”. Ø Pahlavan & Krishnamurthy, “Principles of Wireless Networks”. q Unfortunately, none is sufficient by itself for this course q Nearly half the course will cover recent research papers 25 QUESTIONS ? http://wireless.web.unc.edu jasleen@cs.unc.edu 26 13
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