1. CS434/534: Mobile Computing and Wireless Networks http://zoo.cs.yale.edu/classes/cs434/ Y. Richard Yang 01/10/2011

2. 2 Outline r Introduction to wireless networks and mobile computing r Challenges facing wireless networks and mobile computing r Course information r Introduction to wireless physical layer

3. 3 Goal of Wireless Networking and Mobile Computing “People and their machines should be able to access information and communicate with each other easily and securely, in any medium or combination of media – voice, data, image, video, or multimedia – any time, anywhere, in a timely, cost-effective way.” Dr. G. H. Heilmeier, Oct 1992

4. 4 Enabling Technologies r Development and deployment of wireless/mobile technology and infrastructure m in-room, in-building, on-campus, in-the-field, MAN, WAN r Improving device capabilities/mobile applications, e.g., m andriod: http://code.google.com/android/ m iphone/ipad: http://developer.apple.com/iphone/

5. Pervasive of Mobile Wireless Devices r Many industrial countries reach at least 90% mobile phone subscription penetration rate m http://en.wikipedia.org/wiki/Mobile_phone_penetration_ rate m “The mobile device will be the primary connection tool to the Internet for most people in the world in 2020. “ PEW Internet and American Life Project r Wireless coverage: m http://www.verizonwireless.com/wireless-coverage-area- map.shtml m http://www.wireless.att.com/coverageviewer/ 5

6. Internet Traffic Growth 6

7. 7 At Home WiFi cellular bluetooth UWB satellite WiFi 802.11g/n

8. 8 At Home Source: http://teacher.scholastic.com/activities/science/wireless_interactives.htm

9. 9 At Home: Last-Mile r Many users still don’t have broadband m reasons: out of service area; some consider expensive

10. 10 On the Move Source: http://www.ece.uah.edu/~jovanov/whrms/

11. 11 On the Move: Context-Aware Source: http://www.cs.cmu.edu/~aura/docdir/sensay_iswc.pdf

12. 12 ad hoc road condition, weather, location-based services, emergency On the Road

13. 13 UMTS, DECT 2 Mbit/s UMTS Rel. 6 400 kbit/s LAN 100 Mbit/s, WLAN 54 Mbit/s UMTS Rel. 5 400 kbit/s GSM 115 kbit/s, WLAN 11 Mbit/s GSM 53 kbit/s Bluetooth 500 kbit/s GSM/EDGE 135 kbit/s, WLAN 780 kbit/s LAN, WLAN 780 kbit/s Mobile and Wireless Services – Always Best Connected

14. 14 Example: IntelliDrive (Vehicle Infrastructure Integration) r Traffic crashes resulted in more than 41,000 lives lost/year r Establishing vehicle-to- vehicle (V2V), vehicle-to- infrastructure (V2I) and vehicle-to-hand-held- devices (V2D) communications m safety: e.g., intersection collision avoidance/violation warning/turn conflict warning, curve warning m mobility: e.g., crash data, weather/road surface data, construction zones, emergency vehicle signal pre-emption More info: http://www.its.dot.gov/intellidrive/index.htm

15. 15 Collision Avoidance : V2V Networks r stalled vehicle warning http://www.gm.com/company/gmability/safety/news_issues/releases/sixthsense_102405.html r bland spots

16. 16 Collision Avoidance at Intersections r Two million accidents at intersections per year in US Source: http://www.fhwa.dot.gov/tfhrc/safety/pubs/its/ruralitsandrd/tb-intercollision.pdf

17. 17 Disaster Recovery/Military r 9/11, Tsunami, Hurricane Katrina, South Asian earthquake … r Wireless communication and mobile computing capability can make a difference between life and death ! m rapid deployment m efficient resource and energy usage m flexible: unicast, broadcast, multicast, anycast m resilient: survive in unfavorable and untrusted environments http://www.att.com/ndr/

18. 18 Habitat Monitoring: Example on Great Duck Island Patch Network Transit Network Basestation Gateway A 15-minute human visit leads to 20% offspring mortality

19. 19 Wireless and Mobile Computing r Driven by technology and vision m wireless communication technology m global infrastructure m device miniaturization m mobile computing platforms r The field is moving fast

20. Why is the Field Challenging?

21. 21 Challenge 1: Unreliable and Unpredictable Wireless Coverage * Cerpa, Busek et. al What Robert Poor (Ember) calls “The good, the bad and the ugly” r Wireless links are not reliable: they may vary over time and space Reception v. DistanceReception vs. Power

22. 22 Challenge 2: Open Wireless Medium r Wireless interference S1 S2 R1

23. 23 Challenge 2: Open Wireless Medium r Wireless interference r Hidden terminals S1 S2 R1 S1R1 S2

24. 24 Challenge 2: Open Wireless Medium r Wireless interference r Hidden terminals r Exposed terminal S1 S2 R1 S1R1 S2 R1S1S2R2

25. 25 Challenge 2: Open Wireless Medium r Wireless interference r Hidden terminals and r Exposed terminal r Wireless security m eavesdropping, denial of service, … S1 S2 R1 S1R1 R2 R1S1S2R2

26. 26 Challenge 3: Mobility r Mobility causes poor-quality wireless links r Mobility causes intermittent connection m under intermittent connected networks, traditional routing, TCP, applications all break r Mobility changes context, e.g., location

27. 27 Challenge 4: Portability r Limited battery power r Limited processing, display and storage Sensors, embedded controllers Mobile phones voice, data simple graphical displays GSM/3G Smart phone data smaller graphical displays 802.11/3G Tablet/Laptop Performance/Weight/Power Consumption

28. 28 Challenge 5: Changing Regulation and Multiple Communication Standards

29. 29 Challenge 5: Changing Regulation and Multiple Communication Standards cellular phonessatellites wireless LAN cordless phones 1992: GSM 1994: DCS 1800 2001: IMT-2000 1987: CT1+ 1982: Inmarsat- A 1992: Inmarsat-B Inmarsat-M 1998: Iridium 1989: CT 2 1991: DECT 199x: proprietary 1997: IEEE 802.11 1999: 802.11b, Bluetooth 1988: Inmarsat- C analogue digital 1991: D-AMPS 1991: CDMA 1981: NMT 450 1986: NMT 900 1980: CT0 1984: CT1 1983: AMPS 1993: PDC 2000: GPRS 2000: IEEE 802.11a Fourth Generation (Internet based)

30. Wireless Communication Standards 30

31. IMT Advanced Requirements r All-IP communications. r Peak data rates m 100 Mbit/s for high mobility m 1 Gbit/s for low mobility r Scalable channel bandwidth, between 5 and 20 MHz, optionally up to 40 MHz r Peak link spectral efficiency m 15 bit/s/Hz (downlink); 6.75 bit/s/Hz (uplink) r System spectral efficiency m 3 bit/s/Hz/cell (downlink) m 2.25 bit/s/Hz/cell (indoor) 31

32. Wireless Bit Rates 32 1.2 kbps9.6 kbps NMT 1981 GSM 1992 IMT-2000 2001 (WCDMA; CDMA) 384 kbps 2 Mbps 100 Mbps 1 Gbps IMT-Advanced ~2012

33. What Will We Cover?

34. 34 r Instructor Y. Richard Yang, yry@cs.yale.edu, AKW 308A office hours: to be posted r Teaching fellow Jiewen Huang, jiewen.huang@yale.edu, AKW office hours: to be posted on class page r Course home page m http://zoo.cs.yale.edu/classes/cs434/ Class Info: Personnel

35. 35 Class Goals r Learn both fundamentals and applications of wireless networking and mobile computing r Obtain hands-on experience on developing on wireless, mobile devices m wireless: GNU radio m mobile computing: Android r Discuss challenges and opportunities in wireless networking and mobile computing

36. 36 Application Transport Network Data Link Physical Medium Data Link Physical Application Transport Network Data Link Physical Data Link Physical Network Radio Often we need to implement a function across multiple layers. The Layered Reference Model

37. 37 Course Topic: Communications r Three topics, with ~ 4 classes each m Physical layer: channel and diversity m Link layer: channel sharing m Network and transport: routing, reliability

38. Course Topic: Basic Services r Two topics with ~2 classes each m Localization m Service and naming 38

39. Course Topic: Mobile App and OS r Mobile OS/application framework [2-3 classes] m TinyOS/Android r Storage/file system for mobile devices r Resource-driven dynamic adaptation r Diverse mobile hardware platforms r Mobile app design methodology and case studies 39

40. 40 Course Topics Transport Network Data Link Physical CommunicationsLocations Location Management Localization Security OS/Application Platform

41. 41 Class Materials r Chapters of reference books r Selected conference and journal papers r Other resources m MOBICOM, SIGCOMM, INFOCOM Proceedings m IEEE Network, Communications, Pervasive magazines

42. 42 Suggested Reference Books r "Mobile Communications, Second Edition," by Jochen Schiller, Addison Wesley. 2nd Ed. August 2003. r “802.11 Wireless Networks: the Definitive Guide” by Matthew Gast, O’Reilly, 2005 (available online)

43. 43 Suggested Reference Books (2) r “Fundamentals of Wireless Communication”, by David Tse and Pramod Viswanath, Cambridge University Press, 2005. (available online) r "Mobile Computing Handbook," by Mohammad Ilyas and Imad Mahgoub, CRC Press, 2005.

44. 44 What You Need to Do r Your prerequisite m motivated, critical m basic programming skill r Your workload m class participation actively participate in class discussions one presentation at Mobile app [4-5 such classes] m 3-4 assignments m One project m One midterm

45. 45 Class Project r Goal: obtain hands-on experience r I’ll suggest potential topics r You may also choose your own topic r Initial proposal + midterm progress report + final report + [presentation] r We provide Android Phone/iPod touch

46. 46 Grading r More important is what you realize/learn than the grades Project35% Assignments35% Exam20% Class Participation 10%

47. 47 Class Survey r Please take the class survey m help me to determine your background m help me to determine the depth and topics m suggest topics that you want to be covered

48. Questions?

49. 49 Overview of Wireless Transmissions source decoding bit stream channel decoding receiver demodulation source coding bit stream channel coding analog signal sender modulation

50. 50 Signal r Signal are generated as physical representations of data r A signal is a function of time and location 1 0 t a special type of signal, sine waves, also called harmonics: s(t) = A t sin(2  f t t +  t ) with frequency f, period T=1/f, amplitude A, phase shift  1 0 ideal digital signal t

51. 51 Fundamental Question: Why Not Send Digital Signal in Wireless Communications? 1 0 ideal digital signal t

52. 52 1 0 1 0 tt ideal periodical digital signal decomposition Fourier Transform: Every Signal Can be Decomposed as a Collection of Harmonics The more harmonics used, the smaller the approximation error.

53. Example 53 - Two representations: time domain; frequency domain - Knowing one can recover the other

54. 54

55. 55 Fundamental Question: Why Not Send Digital Signal in Wireless Communications? r May cause interference m suppose digital frame length T, then signal decomposes into frequencies at 1/T, 2/T, 3/T, … m let T = 1 ms, generates radio waves at frequencies of 1 KHz, 2 KHz, 3 KHz, … 1 0 digital signal t

56. 56 Frequencies for Communications VLF = Very Low FrequencyUHF = Ultra High Frequency LF = Low Frequency SHF = Super High Frequency MF = Medium Frequency EHF = Extra High Frequency HF = High Frequency UV = Ultraviolet Light VHF = Very High Frequency Frequency and wave length:  = c/f wave length, speed of light c  3x10 8 m/s, frequency f 1 Mm 300 Hz 10 km 30 kHz 100 m 3 MHz 1 m 300 MHz 10 mm 30 GHz 100  m 3 THz 1  m 300 THz visible light VLFLFMFHFVHFUHFSHFEHFinfraredUV optical transmission coax cabletwisted pair

57. 57 r ITU-R holds auctions for new frequencies, manages frequency bands worldwide (WRC, World Radio Conferences) Frequencies and Regulations

58. 58 Spectrum and Bandwidth: Shannon Channel Capacity r The maximum number of bits that can be transmitted per second by a physical channel is: where W is the frequency range of the channel, and S/N is the signal noise ratio, assuming Gaussian noise

59. 59 r Objective m encode digital data into analog signals at the right frequency range with limited usage of spectrum Modulation r Basic schemes m Amplitude Modulation (AM) m Frequency Modulation (FM) m Phase Modulation (PM)

60. 60 r Modulation of digital signals known as Shift Keying r Amplitude Shift Keying (ASK): r Frequency Shift Keying (FSK): r Phase Shift Keying (PSK): 101 t 101 t 101 t Modulation

61. Example r Suppose fc = 1 GHz (fc1 = 1 GHz, fc0 = 900 GHz for FSK) r Bit rate is 1 Mbps r Encode one bit at a time r Bit seq: 1 0 0 1 0 r Q: How does the wave look like for each scheme? 61 t 101 t 101 t 101 t

62. Backup 62

63. Evolution of Mobile Systems to 3G 63

64. 64 3G Networks http://en.wikipedia.org/wiki/List_of_mobile_network_operators_of_the_Americas#United_States