The Two Successful DomainsGeneral Problems in Wireless NetworksData on Wireless Networks! What are the Problems?Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10Slide 11Last Hop CommunicationCellular FrameworkSlide 14Slide 15Handoff TypesSlide 17Slide 18Slide 19Slide 20The Two Successful DomainsThe Two Successful DomainsWireless networks (Cellular)Wireless networks (Cellular)–Supports voiceSupports voice–Total coverage in many countriesTotal coverage in many countries–Decreasing costDecreasing cost–The boon – user mobilityThe boon – user mobilityWireless extension to the Internet (Wi-Fi)Wireless extension to the Internet (Wi-Fi)–Information contentInformation content–Supports multimedia servicesSupports multimedia services–Global penetration – millions of nodesGlobal penetration – millions of nodes–Decreasing costDecreasing costIEEE 802.16 based WiMaxIEEE 802.16 based WiMaxLTE (Long Term Evolution)LTE (Long Term Evolution)General Problems in Wireless NetworksGeneral Problems in Wireless NetworksResource scarcityResource scarcity–Limited bandwidthLimited bandwidthUnreliable wireless link Unreliable wireless link –Error prone channels (BER 10Error prone channels (BER 10-4 -4 to 10to 10-3-3))Varying channel conditionsVarying channel conditions–Channel models fluctuates Channel models fluctuates In spite of all these problems, voice services are well supported.Can it support multimedia services?Combination of various medium – text, audio/video, graphicsCombination of various medium – text, audio/video, graphics–Audio/video conferencing, shared whiteboard, surfing, email, etc.Audio/video conferencing, shared whiteboard, surfing, email, etc.Varied requirements Varied requirements –Low bit error rateLow bit error rate–High bandwidthHigh bandwidth–Low delayLow delaySynchronization of multiple data typesSynchronization of multiple data types–Proper schedulingProper scheduling Different coding schemes for different typesDifferent coding schemes for different types–Source codingSource codingCharacteristics of Multimedia ServicesA picture is worth thousand wordsData on Wireless Networks!Data on Wireless Networks!What are the Problems?What are the Problems?True characterization of data traffic is yet unknownTrue characterization of data traffic is yet unknown–Traffic modeling needs to be doneTraffic modeling needs to be doneData services cannot tolerate bit errorsData services cannot tolerate bit errors–Corrupt packets need to be recoveredCorrupt packets need to be recoveredUnpredictable nature of wireless mediumUnpredictable nature of wireless medium–QoS provisioning becomes difficultQoS provisioning becomes difficultBottleneck due to the bandwidth limitationBottleneck due to the bandwidth limitation–Proper buffering / filtering requiredProper buffering / filtering requiredNo differentiated service plans for customersNo differentiated service plans for customers–Class based services requiredClass based services requiredWhat is QoS?What is QoS?Specified by <bandwidth, delay, reliability>Ability of a network element (e.g. an application, host or router) to have some level of assurance that its traffic and service requirements can be satisfiedPredictable service for the traffic from the networke.g., CPU time, bandwidth, buffer spaceAcceptable end-to-end delay and minimum delay jitterWhat is QoE (Quality of Experience)?Human subjectivity associated with qualityHow happy is a user with respect to the service he getsEnd-to-End QoSEnd-to-End QoSRequires cooperation of all network layers from top-to-bottom, as well as every network elementKnowledge of application at end points decides QoS functions implemented at every layer of the network protocol stackType of Services- Best-effort: the Internet (lack of QoS)- Differentiated service (soft QoS) : partial to some traffic but most effective- Guaranteed service (hard QoS) : absolute reservation of resources (RSVP), more expensiveWireless QoS ChallengesWireless QoS ChallengesA limited spectral bandwidth to be shared, causes interferenceCommunication links are time varying, frequency selective channelsUser mobility in wireless networks makes QoS provisioning complex because routes from source to destination cells are different, thus causing varying packet delays and delay jittersError rate of wireless channel is higher due to mobility, interference from other media, multi-path fading. So mobile hosts may experience different channel rates in the same or different cellsDifferent applications have different requirements for bandwidth, delay, jitter (e.g., 9.6Kbps for voice and 76.8Kbps for packetized video)Wireless QoS: Desirable FeaturesWireless QoS: Desirable FeaturesAdapt to dynamically changing network and traffic conditionsGood performance for large networks and large number of connections (like the Internet)Higher data rateModest buffer requirementHigher capacity utilizationLow overhead in header bits/packetLow processing overhead/packet within network and end systemBandwidth Requirement for Bandwidth Requirement for Multimedia TrafficMultimedia TrafficApplication bandwidth requirements on log-scale axis in bits per second (bps) Vertical dashed lines show the bandwidth capability of a few network technologiesMulti-rate Traffic ScenarioMulti-rate Traffic ScenarioMobile UsersBase StationC channels Real-time traffic (voice, video) Non real-time traffic (TCP/IP packets)Evolution of Wireless Data Networks2G wireless systems ( voice-centric, data loss unimportant)- IS-95 CDMA, TDMA, GSM2.5G systems (voice and low data rate)- CDPD, GPRS, HSCSD, IS-99 CDMA, IS-136+- Date rates: CDPD (19.2Kbps), HSCSD (76.8Kbps), GPRS (114Kbps)3G proposed standards (data-centric, high data rate)- UMTS, EDGE, W-CDMA, cdma2000, UWC 136, IMT-2000- Data rates: EDGE (384Kbps), cdma2000 (2Mbps), W-CDMA (10Mbps)Last Hop CommunicationLast Hop Communication WIRE-LINE NETWORK WIRE-LINE NETWORKBase Station (BS)CellWireless LinksWired LinksMobile Switching Center (MSC)Mobile unitISDN/PSTN/InternetCellular FrameworkCellular FrameworkMSC/VLR MSC/VLRBSCBSCBTSBTSLocal SwitchCellular NetworkPSTN NetworkMobile TerminalAir LinkHLRTerms to remember MSC: Mobile Switching Center VLR: Visiting Location Register HLR: Home Location Register BSC: Base Station Controller BTS: Base Transmitter Station Mobile Terminal