Johns Hopkins CS 600 647 - lecture 1 of wireless networks

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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 NetworksInstructor: Baruch Awerbuch, [email protected]TA: Herb Rubens, [email protected]Class Homepage: www.cs.jhu.edu/~baruchAll handouts, announcements, homeworks, etc. posted to website“Lectures” link continuously updates topics, handouts, and readingOutlineCourse BasicsCourse SyllabusThe Wireless VisionTechnical ChallengesCurrent Wireless SystemsEmerging Wireless SystemsSpectrum RegulationStandardsTerm project on anything related to wirelessLiterature survey, analysis, or simulationMust set up website for your project (for proposal and reportCourse InformationCourse SyllabusOverview of Wireless Communications Security Review of Physical Media issues Power issue routing AlgorithmsIs there a future for wireless?Some historyRadio invented in the 1880s by MarconiMany sophisticated military radio systems were developed during and after WW2Cellular has enjoyed exponential growth since 1988, with almost 1 billion users worldwide todayIgnited the recent wireless revolutionGrowth rate tapering of3G (voice+data) roll-out disappointingMany spectacular failures recently1G Wireless LANs/Iridium/MetricomRIPWirelessRevolution1980-2003Ancient Systems: Smoke Signals, Carrier Pigeons, …Glimmers of HopeInternet and laptop use exploding2G/3G wireless LANs growing rapidlyLow rate data demand is highMilitary and security needs require wirelessEmerging 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 ChallengesWireless channels are a dificult and capacity-limited broadcast communications mediumTrafic patterns, user locations, and network conditions are constantly changingApplications are heterogeneous with hard constraints that must be met by the networkEnergy 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 SystemsWireless systems today2G Cellular: ~30-70 Kbps.WLANs: ~10 Mbps.Next Generation3G 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 DesignHardwareLinkAccessNetworkApplicationDelay ConstraintsRate ConstraintsEnergy ConstraintsAdapt across design layersReduce uncertainty through schedulingProvide robustness via diversityCurrent Wireless SystemsCellular SystemsWireless LANsSatellite SystemsPaging SystemsBluetoothCellular Systems:Reuse channels to maximize capacityGeographic region divided into cellsFrequencies/timeslots/codes reused at spatially-separated locations.Co-channel interference between same color cells.Base stations/MTSOs coordinate handof and control functionsShrinking cell size increases capacity, as well as networking burdenBASESTATIONMTSOCellular Phone NetworksBSBSMTSOPSTNMTSOBSSan FranciscoNew YorkInternet3G Cellular Design: Voice and DataData is bursty, whereas voice is continuousTypically require diferent access and routing strategies 3G “widens the data pipe”:384 Kbps.Standard based on wideband CDMAPacket-based switching for both voice and data3G cellular struggling in Europe and AsiaEvolution of existing systems (2.5G,2.6798G):GSM+EDGEIS-95(CDMA)+HDR100 Kbps may be enoughWhat is beyond 3G?The trillion dollar questionWLANs connect “local” computers (100m range)Breaks data into packetsChannel access is shared (random access)Backbone Internet provides best-efort servicePoor performance in some apps (e.g. video)01011011InternetAccessPoint01011011Wireless Local Area Networks (WLANs)Wireless LAN Standards802.11b (Current Generation)Standard for 2.4GHz ISM band (80 MHz)Frequency hopped spread spectrum1.6-10 Mbps, 500 ft range802.11a (Emerging Generation)Standard for 5GHz NII band (300 MHz)OFDM with time division20-70 Mbps, variable rangeSimilar to HiperLAN in Europe802.11g (New Standard)Standard in 2.4 GHz and 5 GHz bandsOFDM Speeds up to 54 MbpsIn 200?,all WLAN cards will have all 3 standardsSatellite SystemsCover very large areasDiferent orbit heightsGEOs (39000 Km) versus LEOs (2000 Km)Optimized for one-way transmissionRadio (XM, DAB) and movie (SatTV) broadcastingMost two-way systems struggling or bankruptExpensive alternative to terrestrial systemA few ambitious systems on


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