600.427 Wireless NetworksOutlineCourse InformationCourse SyllabusIs there a future for wireless? Some historyGlimmers of HopeFuture Wireless NetworksDesign ChallengesMultimedia RequirementsWireless Performance GapEvolution of Current SystemsFuture GenerationsCrosslayer DesignCurrent Wireless SystemsCellular Systems: Reuse channels to maximize capacityCellular Phone Networks3G Cellular Design: Voice and DataWireless Local Area Networks (WLANs)Wireless LAN StandardsSatellite SystemsPaging SystemsBluetoothEmerging SystemsAd-Hoc NetworksDesign IssuesSensor Networks Energy is the driving constraintEnergy-Constrained NodesDistributed Control over Wireless LinksJoint Design ChallengesSpectrum RegulationStandardsMain Points600.427 Wireless NetworksInstructor: Baruch Awerbuch, [email protected]TA: Herb Rubens, [email protected]Class Homepage: www.cs.jhu.edu/~baruchAll handouts, announcements, homeworks, etc. posted to website“Lectures” link continuously updates topics, handouts, and readingOutlineCourse BasicsCourse SyllabusThe Wireless VisionTechnical ChallengesCurrent Wireless SystemsEmerging Wireless SystemsSpectrum RegulationStandardsTerm project on anything related to wirelessLiterature survey, analysis, or simulationMust set up website for your project (for proposal and reportCourse InformationCourse SyllabusOverview of Wireless Communications Security Review of Physical Media issues Power issue routing AlgorithmsIs there a future for wireless?Some historyRadio invented in the 1880s by MarconiMany sophisticated military radio systems were developed during and after WW2Cellular has enjoyed exponential growth since 1988, with almost 1 billion users worldwide todayIgnited the recent wireless revolutionGrowth rate tapering of3G (voice+data) roll-out disappointingMany spectacular failures recently1G Wireless LANs/Iridium/MetricomRIPWirelessRevolution1980-2003Ancient Systems: Smoke Signals, Carrier Pigeons, …Glimmers of HopeInternet and laptop use exploding2G/3G wireless LANs growing rapidlyLow rate data demand is highMilitary and security needs require wirelessEmerging interdisciplinary applicationsFuture Wireless NetworksWireless Internet accessNth generation CellularWireless Ad Hoc NetworksSensor Networks Wireless EntertainmentSmart Homes/SpacesAutomated HighwaysAll this and more…Ubiquitous Communication Among People and Devices•Hard Delay Constraints•Hard Energy ConstraintsDesign ChallengesWireless channels are a dificult and capacity-limited broadcast communications mediumTrafic patterns, user locations, and network conditions are constantly changingApplications are heterogeneous with hard constraints that must be met by the networkEnergy and delay constraints change design principles across all layers of the protocol stackMultimedia RequirementsVoice VideoDataDelayPacket LossBERData RateTraffic<100ms - <100ms<1% 0 <1%10-310-610-68-32 Kbps 1-100 Mbps 1-20 MbpsContinuous Bursty ContinuousOne-size-fits-all protocols and design do not work wellWired networks use this approach, with poor resultsWireless Performance GapWIDE AREA CIRCUIT SWITCHINGUser Bit-Rate (kbps)14.4digitalcellular28.8 modemISDNATM9.6 modem2.4 modem2.4 cellular32 kbps PCS9.6 cellularwired- wireless bit-rate "gap"1970 200019901980YEARLOCAL AREA PACKET SWITCHINGUser Bit-Rate (kbps)EthernetFDDIATM100 M EthernetPollingPacket Radio1st genWLAN2nd genWLANwired- wirelessbit-rate "gap" 1970 200019901980.01.1110100100010,000100,000YEAR.01.1110100100010,000100,000Evolution of Current SystemsWireless systems today2G Cellular: ~30-70 Kbps.WLANs: ~10 Mbps.Next Generation3G Cellular: ~300 Kbps.WLANs: ~70 Mbps.Technology Enhancements Hardware: Better batteries. Better circuits/processors.Link: Antennas, modulation, coding, adaptivity, DSP, BW.Network: Dynamic resource allocation. Mobility support.Application: Soft and adaptive QoS.“Current Systems on Steroids”Future GenerationsRateMobility2G3G4G802.11b WLAN2G CellularOther Tradeoffs: Rate vs. Coverage Rate vs. Delay Rate vs. Cost Rate vs. EnergyFundamental Design Breakthroughs NeededCrosslayer DesignHardwareLinkAccessNetworkApplicationDelay ConstraintsRate ConstraintsEnergy ConstraintsAdapt across design layersReduce uncertainty through schedulingProvide robustness via diversityCurrent Wireless SystemsCellular SystemsWireless LANsSatellite SystemsPaging SystemsBluetoothCellular Systems:Reuse channels to maximize capacityGeographic region divided into cellsFrequencies/timeslots/codes reused at spatially-separated locations.Co-channel interference between same color cells.Base stations/MTSOs coordinate handof and control functionsShrinking cell size increases capacity, as well as networking burdenBASESTATIONMTSOCellular Phone NetworksBSBSMTSOPSTNMTSOBSSan FranciscoNew YorkInternet3G Cellular Design: Voice and DataData is bursty, whereas voice is continuousTypically require diferent access and routing strategies 3G “widens the data pipe”:384 Kbps.Standard based on wideband CDMAPacket-based switching for both voice and data3G cellular struggling in Europe and AsiaEvolution of existing systems (2.5G,2.6798G):GSM+EDGEIS-95(CDMA)+HDR100 Kbps may be enoughWhat is beyond 3G?The trillion dollar questionWLANs connect “local” computers (100m range)Breaks data into packetsChannel access is shared (random access)Backbone Internet provides best-efort servicePoor performance in some apps (e.g. video)01011011InternetAccessPoint01011011Wireless Local Area Networks (WLANs)Wireless LAN Standards802.11b (Current Generation)Standard for 2.4GHz ISM band (80 MHz)Frequency hopped spread spectrum1.6-10 Mbps, 500 ft range802.11a (Emerging Generation)Standard for 5GHz NII band (300 MHz)OFDM with time division20-70 Mbps, variable rangeSimilar to HiperLAN in Europe802.11g (New Standard)Standard in 2.4 GHz and 5 GHz bandsOFDM Speeds up to 54 MbpsIn 200?,all WLAN cards will have all 3 standardsSatellite SystemsCover very large areasDiferent orbit heightsGEOs (39000 Km) versus LEOs (2000 Km)Optimized for one-way transmissionRadio (XM, DAB) and movie (SatTV) broadcastingMost two-way systems struggling or bankruptExpensive alternative to terrestrial systemA few ambitious systems on
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