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Mobile Computing Introduction

Mobile Computing Introduction. Goal of Wireless and Mobile Computing.

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Mobile Computing Introduction

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  1. Mobile ComputingIntroduction

  2. Goal of Wireless 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

  3. Technology Trends • Development and deployment of wireless technology and infrastructure • in-room, in-building, on-campus, in-the-field, MAN, WAN • Miniaturization of computing machinery . . . -> PCs -> laptop -> PDAs -> embeddedcomputers/sensors

  4. WiFi WiFi 802.11g satellite WiFi UWB bluetooth WiFi cellular At Home

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

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

  7. 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

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

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

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

  11. Conventional Networks • Wired & wireless network • Infinite power source • Rapidly increasing bandwidth (Optical Networks…) • High performance workstations & servers (clusters, supercomputers, grid computing) Department of Computer Science Louisiana State University

  12. Conventional Networks Cont. • Attended nodes • Consists of Routers, Switches, Bridges and other complex components as shown in figure • Manually configurable hosts • Hosts are reparable and replaceable • Complex global routing schemes • Fixed, named nodes Department of Computer Science Louisiana State University

  13. Wireless Networks • Need: Access computing and communication services, on the move • Infrastructure-based Networks • traditional cellular systems (base station infrastructure) • Wireless LANs • Infrared (IrDA) or radio links (Wavelan) • very flexible within the reception area; ad-hoc networks possible • low bandwidth compared to wired networks (1-10 Mbit/s) • Ad hoc Networks • useful when infrastructure not available, impractical, or expensive • military applications, rescue, home networking

  14. Limitations of Mobile Environments • Limitations of the Wireless Network • heterogeneity of fragmented networks • frequent disconnections • limited communication bandwidth • Limitations Imposed by Mobility • lack of mobility awareness by system/applications • route breakages • Limitations of the Mobile Computer • short battery lifetime • limited capacities

  15. Effect of Mobility on Protocol Stack • Application • new applications and adaptations • Transport • congestion and flow control • Network • addressing and routing • Link • media access and handoff • Physical • transmission errors and interference

  16. Mobile Applications • Vehicles • transmission of news, road condition etc • ad-hoc network with near vehicles to prevent accidents • Emergencies • early transmission of patient data to the hospital • ad-hoc network in case of earthquakes, cyclones • military ... • Traveling salesmen • direct access to central customer files • consistent databases for all agents • mobile office

  17. Mobile Applications • Web access • outdoor Internet access • intelligent travel guide with up-to-datelocation dependent information • Location aware services • find services in the local environment, e.g. printer • Information services • push: e.g., stock quotes • pull: e.g., nearest cash ATM • Disconnected operations • mobile agents, e.g., shopping • Entertainment • ad-hoc networks for multi user games

  18. What is different in wireless network? • Bandwidth • Error rate • Media • Signal strength (fading) • MAC • Mobility • Security

  19. Wireless networks • Two types • Voice network • Cellular systems (GSM, CDMA etc.) • Data network • WiFi, HiperLAN • Networks are moving towards an integrated network • GPRS • Voice over WiFi

  20. Source: Matt Welsh, Harvard University

  21. WiFi Network Basic Service Set Access Point Wireline network g Access Point

  22. Bluetooth • Short range (10m),moderate data rate (720kbps) for creating an adhoc network between personal devices • One master and upto 7 slaves in a piconet • Master controls the transmission schedules of all the devices • TDMA scheduling • Frequency hopping used to avoid interference with other piconets • 79 channels in the 2.4GHz ISM band, with 1 MHz spacing • Frequency hopping at 1600 hops/s PICONET

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

  24. Why is the Field Challenging?

  25. Signal Propagation Ranges: High Level • Transmission range • communication possible • low error rate • Detection range • detection of the signal possible • no communication possible • Interference range • signal may not be detected • signal adds to the background noise sender transmission distance detection interference

  26. Challenge 1: Unreliable and Unpredictable Wireless Links • Wireless links are not reliable: they may vary over time and space Standard Deviation v. Reception rate Reception v. Distance Asymmetry vs. Power *Cerpa, Busek et. al What Robert Poor (Ember) calls “The good, the bad and the ugly”

  27. Challenge 2: Open Wireless Medium • Wireless interference • Hidden terminals and • Exposed terminal • Wireless security • eavesdropping, denial of service, … R1 S1 S2 R2 S1 R1 R2 R1 S1 S2 R2

  28. 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

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

  30. 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 200?: Fourth Generation (Internet based)

  31. Why Not Send Digital Signal in Wireless Communications? • Digital signals need • a wide range of frequencies • however, the frequencies that wireless communications can use is highly regulated to avoid interference

  32. FREQUENCY SPECTRUM Very Low Frequency 300 Hz to 30 KHz Low Frequency 30KHz to 300 KHz 30KHz- 100KHz Used in Submarines – Penetrate through Waters 148.5KHz – 283.5 KHz – Radio Stations in Germany Medium Frequency 300KHz – 3MHz Amplitude Modulation (AM) – 520KHz – 1605KHz High Frequency 3MHz – 150MHz Short Wave (SW) – 5.9 MHz – 26.1 MHz Frequency Modulation – 87.5 MHz – 108 MHz

  33. FREQUENCY SPECTRUM Very High Frequency 150 MHz to 300 MHz Analog TV – 174 MHz to 220 MHz Digital Audio Broadcasting (DAB) – 223 MHz – 230 MHz Ultra High Frequency 300MHz – 2GHz Analog TV – 470 – 790 MHz Digital TV – 470 – 862 MHz Digital Audio Broadcasting – 1452 – 1472 MHz Analog Telephone – 450 MHz – 465 MHz Global System for Mobile Communication 890 – 915 MHz , 935 MHz – 960 MHz 1710 – 1785 MHz, 1805 – 1880 MHz Digital Enhanced Cordless Telecommunications (DECT) 1880 – 1900 MHz

  34. FREQUENCY SPECTRUM Super High Frequency 2 GHz to 30 GHz 2.4 GHz License Free Band Satellites 4 and 6 GHz – C-Band 11 and 14 GHz – Ku Band 19 and 29 GHz – Ka Band Extremely High Frequency 30 GHz to 300 GHz Infrared Data Association (IrDA) 1 THz to 300 THz

  35. Antennas • Directional Antennas • Transmission in One Direction • Omni Directional Antennas • Data is transmitted in All the Directions • Sectorized Antennas • Data can be transmitted in any direction but in a sector • Smart Antenna • Data can be transmitted in any direction accurately

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