Slide 1Chapter 6: Wireless and Mobile NetworksChapter 6 outlineElements of a wireless networkSlide 5Slide 6Characteristics of selected wireless link standardsSlide 8Slide 9Wireless network taxonomyWireless Link Characteristics (1)Wireless Link Characteristics (2)Wireless network characteristicsCode Division Multiple Access (CDMA)CDMA Encode/DecodeCDMA: two-sender interferenceSlide 17IEEE 802.11 Wireless LAN802.11 LAN architecture802.11: Channels, association802.11: passive/active scanningIEEE 802.11: multiple accessIEEE 802.11 MAC Protocol: CSMA/CAAvoiding collisions (more)Collision Avoidance: RTS-CTS exchange802.11 frame: addressingSlide 27Slide 28Slide 29Slide 30Slide 31Slide 32Slide 33Slide 34Slide 35Slide 36Cellular networks: the first hopCellular standards: brief surveySlide 39Slide 40Slide 41What is mobility?Mobility: VocabularyMobility: more vocabularyHow do you contact a mobile friend:Mobility: approachesSlide 47Mobility: registrationMobility via Indirect RoutingIndirect Routing: commentsIndirect Routing: moving between networksMobility via Direct RoutingMobility via Direct Routing: commentsAccommodating mobility with direct routingSlide 55Mobile IPMobile IP: indirect routingMobile IP: agent discoveryMobile IP: registration exampleSlide 60Handling mobility in cellular networksSlide 62Slide 63Slide 64Slide 65Slide 66Mobility: GSM versus Mobile IPWireless, mobility: impact on higher layer protocolsChapter 6 Summary6: Wireless and Mobile Networks 6-1Chapter 6Wireless and Mobile NetworksA note on the use of these ppt slides:We’re making these slides freely available to all (faculty, students, readers). They’re in PowerPoint form so you can add, modify, and delete slides (including this one) and slide content to suit your needs. They obviously represent a lot of work on our part. In return for use, we only ask the following: If you use these slides (e.g., in a class) in substantially unaltered form, that you mention their source (after all, we’d like people to use our book!) If you post any slides in substantially unaltered form on a www site, that you note that they are adapted from (or perhaps identical to) our slides, and note our copyright of this material.Thanks and enjoy! JFK/KWRAll material copyright 1996-2007J.F Kurose and K.W. Ross, All Rights ReservedComputer Networking: A Top Down Approach 4th edition. Jim Kurose, Keith RossAddison-Wesley, July 2007.6: Wireless and Mobile Networks 6-2Chapter 6: Wireless and Mobile NetworksBackground: # wireless (mobile) phone subscribers now exceeds # wired phone subscribers!computer nets: laptops, palmtops, PDAs, Internet-enabled phone promise anytime untethered Internet accesstwo important (but different) challengeswireless: communication over wireless linkmobility: handling the mobile user who changes point of attachment to network6: Wireless and Mobile Networks 6-3Chapter 6 outline6.1 Introduction Wireless6.2 Wireless links, characteristicsCDMA6.3 IEEE 802.11 wireless LANs (“wi-fi”)6.4 Cellular Internet Accessarchitecturestandards (e.g., GSM)Mobility6.5 Principles: addressing and routing to mobile users6.6 Mobile IP6.7 Handling mobility in cellular networks6.8 Mobility and higher-layer protocols6.9 Summary6: Wireless and Mobile Networks 6-4Elements of a wireless networknetwork infrastructurewireless hostslaptop, PDA, IP phonerun applicationsmay be stationary (non-mobile) or mobilewireless does not always mean mobility6: Wireless and Mobile Networks 6-5Elements of a wireless networknetwork infrastructure base stationtypically connected to wired networkrelay - responsible for sending packets between wired network and wireless host(s) in its “area”e.g., cell towers, 802.11 access points6: Wireless and Mobile Networks 6-6Elements of a wireless networknetwork infrastructure wireless linktypically used to connect mobile(s) to base stationalso used as backbone link multiple access protocol coordinates link access various data rates, transmission distance6: Wireless and Mobile Networks 6-7Characteristics of selected wireless link standardsIndoor10-30mOutdoor50-200mMid-rangeoutdoor200m – 4 KmLong-rangeoutdoor5Km – 20 Km.056.384145-1154IS-95, CDMA, GSM2GUMTS/WCDMA, CDMA20003G802.15802.11b802.11a,gUMTS/WCDMA-HSPDA, CDMA2000-1xEVDO3G cellularenhanced802.16 (WiMAX)802.11a,g point-to-point200802.11nData rate (Mbps)data6: Wireless and Mobile Networks 6-8Elements of a wireless networknetwork infrastructure infrastructure modebase station connects mobiles into wired networkhandoff: mobile changes base station providing connection into wired network6: Wireless and Mobile Networks 6-9Elements of a wireless networkad hoc modeno base stationsnodes can only transmit to other nodes within link coveragenodes organize themselves into a network: route among themselves6: Wireless and Mobile Networks 6-10Wireless network taxonomysingle hopmultiple hopsinfrastructure(e.g., APs)noinfrastructurehost connects to base station (WiFi,WiMAX, cellular) which connects to larger Internetno base station, noconnection to larger Internet (Bluetooth, ad hoc nets)host may have torelay through severalwireless nodes to connect to larger Internet: mesh netno base station, noconnection to larger Internet. May have torelay to reach other a given wireless nodeMANET, VANET6: Wireless and Mobile Networks 6-11Wireless Link Characteristics (1)Differences from wired link ….decreased signal strength: radio signal attenuates as it propagates through matter (path loss)interference from other sources: standardized wireless network frequencies (e.g., 2.4 GHz) shared by other devices (e.g., phone); devices (motors) interfere as wellmultipath propagation: radio signal reflects off objects ground, arriving ad destination at slightly different times…. make communication across (even a point to point) wireless link much more “difficult”6: Wireless and Mobile Networks 6-12Wireless Link Characteristics (2)SNR: signal-to-noise ratiolarger SNR – easier to extract signal from noise (a “good thing”)SNR versus BER tradeoffsgiven physical layer: increase power -> increase SNR->decrease BERgiven SNR: choose physical layer that meets BER requirement, giving highest thruput•SNR may change with mobility: dynamically adapt physical layer (modulation technique, rate) 10203040QAM256 (8 Mbps)QAM16 (4 Mbps)BPSK (1