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Mobile Computing and Wireless Networking Lec 01

ECOM 6320. Mobile Computing and Wireless Networking Lec 01. 01 /03/2010. Outline. Introduction to wireless networks and mobile computing Challenges facing wireless networks and mobile computing Introduction to wireless physical layer. Goal of Wireless Networking and Mobile Computing.

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Mobile Computing and Wireless Networking Lec 01

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  1. ECOM 6320 Mobile Computing and Wireless Networking Lec 01 01/03/2010

  2. Outline • Introduction to wireless networks and mobile computing • Challenges facing wireless networks and mobile computing • Introduction to wireless physical layer

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

  4. Enabling Technologies • Development and deployment of wireless/mobile technology and infrastructure • in-room, in-building, on-campus, in-the-field, MAN, WAN • Miniaturization of computing machinery . . . -> PCs -> laptop -> PDAs/smart phones -> embeddedcomputers/sensors • Improving device capabilities/software development environments, e.g., • andriod: http://code.google.com/android/ • iphone: http://developer.apple.com/iphone/ • windows mobile

  5. Pervasive Use of Mobile Wireless Devices • There are ~4 billion mobile phones • Over 50 countries have mobile phone subscription penetration rates higher than that of the population (Infoma 2007) • http://en.wikipedia.org/wiki/Mobile_phone_penetration_rate • 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, Dec. 2008

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

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

  8. At Home: Last-Mile • Many users still don’t have broadband • reasons: out of service area; some consider expensive • Broadband speed is still limited • DSL: 1-6 Mbps download, and 100-768Kbps upload • Cable modem: depends on your neighbors • Insufficient for several applications (e.g., high-quality video streaming)

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

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

  11. On the Road GSM/UMTS, cdmaOne/cdma2000,WLAN, GPS DAB, TETRA, ... ad hoc road condition, weather, location-based services, emergency

  12. Example: IntelliDrive (Vehicle Infrastructure Integration) • Traffic crashes resulted in more than 41,000 lives lost in 2007 • Establishing vehicle-to-vehicle (V2V), vehicle-to-infrastructure (V2I) and vehicle-to-hand-held-devices (V2D) communications • safety: e.g., intersection collision avoidance/violation warning/turn conflict warning, curve warning • 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

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

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

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

  16. Challenge 1: Unreliable and Unpredictable Wireless Coverage • Wireless links are not reliable: they may vary over time and space • Challenge 2: Open Wireless Medium • Wireless interference • Hidden terminals • Wireless security • eavesdropping, denial of service, … Why is the Field Challenging?

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

  18. PDA phone • data • simpler graphical displays • 802.11/3G Sensors, embedded controllers Challenge 4: Portability • Limited battery power • Limited processing, display and storage • Laptop • fully functional • standard applications • battery; 802.11 • Mobile phones • voice, data • simple graphical displays • GSM/3G Performance/Weight/Power Consumption

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

  20. 3G Networks http://en.wikipedia.org/wiki/List_of_mobile_network_operators_of_the_Americas#United_States

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

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

  23. 1 1 ideal digital signal 0 0 t t a special type of signal, sine waves, also called harmonics: s(t) = At sin(2  ft t + t) with frequency f, period T=1/f, amplitude A, phase shift  Signal t • Signal are generated as physical representations of data • A signal is a function of time and location

  24. 1 ideal digital signal 0 t Fundamental Question: Why Not Send Digital Signal in Wireless Communications?

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

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

  27. Frequencies for Communications twisted pair coax cable optical transmission 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 VLF LF MF HF VHF UHF SHF EHF infrared UV VLF = Very Low Frequency UHF = 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  3x108m/s, frequency f

  28. Europe USA Japan Cellular GSM AMPS TDMA CDMA PDC 450 - 457, 479 - , , Phones 486/460 - 467,489 - 824 - 849, 810 - 826, 496, 890 - 915/935 - 869 - 894 940 - 956, TDMA CDMA GSM 960, , , 1429 - 1465, 1710 - 1785/1805 - 1850 - 1910, 1477 - 1513 1880 1930 - 1990 UMTS (FDD) 1920 - 1980, 2110 - 2190 UMTS (TDD) 1900 - 1920, 2020 - 2025 Cordless CT1+ PACS PHS 885 - 887, 930 - 1850 - 1910, 1930 - Phones 932 1990 1895 - 1918 CT2 PACS - UB JCT 1910 - 1930 864 - 868 254 - 380 DECT 1880 - 1900 Wireless IEEE 802.11 IEEE 802.11 902 - 928 LANs I EEE 802.11 2400 - 2483 2471 - 2497 HIPERLAN 2 2400 - 2483 5150 - 5250 5150 - 5350, 5470 - 5150 - 5350, 5725 - 5825 5725 Others RF - Control RF - Control RF - Control 27, 128, 418, 433, 315, 915 426, 868 868 Frequencies and Regulations • ITU-R holds auctions for new frequencies, manages frequency bands worldwide (WRC, World Radio Conferences)

  29. Spectrum and Bandwidth: Shannon Channel Capacity • 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

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

  31. 1 0 1 t 1 0 1 t 1 0 1 t Modulation • Modulation of digital signals known as Shift Keying • Amplitude Shift Keying (ASK): • Frequency Shift Keying (FSK): • Phase Shift Keying (PSK):

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