Chapter 6 Wireless And Mobile Networks - Cse.ust.hk
Chapter 6Wireless and MobileNetworksChapter 6: Wireless and Mobile NetworksBackground: # wireless (mobile) phone subscribers nowexceeds # wired phone subscribers! Computer nets: laptops, palmtops, PDAs,A note on the use of these ppt slides:The notes used in this course are substantially based onpowerpoint slides developed and copyrighted by J.F. Kurose andK.W. Ross, 2007Computer Networking:A Top Down Approach4th edition.Jim Kurose, Keith RossAddison-Wesley, July2007.6: Wireless and Mobile NetworksWireless 6.2 Wireless links,characteristics 6.3 IEEE 802.11wireless LANs (“wi-fi”) 6.4 Cellular InternetAccess ArchitectureStandards (e.g., GSM) Wireless: communication over wireless linkMobility: handling the mobile user who changes pointof attachment to network6: Wireless and Mobile Networks6-1Chapter 6 Outline6.1 IntroductionInternet-enabled phone promise anytimeuntethered Internet access Two important (but different) challenges6-2Elements of a Wireless NetworkMobility 6.5 Principles:addressing and routingto mobile users 6.6 Mobile IP 6.7 Handling mobility incellular networks 6.8 End-to-end mobility 6.9 Mobility and higherlayer protocolsNetworkInfrastructureWireless Hosts Laptop, PDA, IP phone Run applications May be stationary(non-mobile) or mobile Wireless does notalways mean mobility6.10 Summary6: Wireless and Mobile Networks6-36: Wireless and Mobile Networks6-41
Elements of a Wireless NetworkElements of a Wireless NetworkBase StationWireless Link Typically connected Typically used toto wired network Relay - responsiblefor sending packetsbetween wirednetwork and wirelesshost(s) in its “area” E.g., cell towers,802.11 accesspointsNetworkInfrastructure6: Wireless and Mobile NetworksNetworkInfrastructure6: Wireless and Mobile Networks6-5Characteristics of Selected Wireless LinkStandardsconnect mobile(s) tobase station Also used asbackbone link Multiple accessprotocol coordinateslink access Various data rates,transmission distance6-6Elements of a Wireless NetworkInfrastructure Mode Base station connectsData rate (Mbps)200545-11802.11n802.11a,g802.11b41802.11a,g point-to-pointdata802.16 (WiMAX)UMTS/WCDMA-HSPDA, CDMA2000-1xEVDO3G cellularenhancedNetworkInfrastructuremobiles into wirednetwork Handoff: mobilechanges base stationproviding connectioninto wired network802.15.384UMTS/WCDMA, CDMA2000.0563G2GIS-95, CDMA, rangeoutdoor200m – 4 Km5Km – 20 Km6: Wireless and Mobile Networks6-76: Wireless and Mobile Networks6-82
Wireless Network TaxonomyElements of a Wireless NetworkAd hoc Mode No base stations Nodes can onlytransmit to othernodes within linkcoverage Nodes organizethemselves into anetwork: route amongthemselvesinfrastructure(e.g., APs)noinfrastructure6: Wireless and Mobile Networksmultiple hopssingle hophost may have torelay through severalwireless nodes toconnect to largerInternet: mesh nethost connects tobase station (WiFi,WiMAX, cellular)which connects tolarger Internetno base station, noconnection to largerInternet. May have torelay to reach othera given wireless nodeMANET, VANETno base station, noconnection to largerInternet (Bluetooth,ad hoc nets)6: Wireless and Mobile Networks6-9Wireless Link Characteristics (1)Wireless Link Characteristics (2)Differences from wired link . SNR: signal-to-noise ratioDecreased signal strength: radio signalattenuates as it propagates through matter(path loss) Interference from other sources: standardizedwireless network frequencies (e.g., 2.4 GHz)shared by other devices (e.g., phone); devices(motors) interfere as well Multipath propagation: radio signal reflects offobjects ground, arriving ad destination atslightly different times . make communication across (even a point to point)wireless link much more “difficult”6: Wireless and Mobile NetworksSNR versus BER tradeoffs Given physical layer: 6-1110-1Larger SNR – easier toextract signal from noise (a“good thing”)increase power - increaseSNR- decrease BERGiven SNR: choose physicallayer that meets BERrequirement, giving highestthruput SNR may change withmobility: dynamically adaptphysical layer (modulationtechnique, rate)10-210-3BER 6-1010-410-510-610-710203040SNR(dB)QAM256 (8 Mbps)QAM16 (4 Mbps)BPSK (1 Mbps)6: Wireless and Mobile Networks6-123
Exposed Terminal ProblemWireless Network CharacteristicsMultiple wireless senders and receivers createadditional problems (beyond multiple access):ABACBHidden terminal problemCACnot possibleBC’s signalstrengthA’s signalstrength B talks to Aspace B, A hear each otherSignal attenuation: A, C can not hear each other B, C hear each other C wants to talk to D C senses channel and finds it to be busy (as B, C hear each other B, A hear each othermeans A, C unaware of theirinterference at B A, C can not hear each otherB is transmitting to A)interfering at B6: Wireless and Mobile NetworksD C stays quiet (when it could have ideallytransmitted)6: Wireless and Mobile Networks6-13Hidden and Exposed TerminalProblems6-14Chapter 6 outline6.1 Introduction Hidden Terminal More collisions Wastage of resourcesCarrier sense at sender may not prevent collision at receiver Exposed Terminal Underutilization of channel Lower effective throughputWireless 6.2 Wireless links,characteristics 6.3 IEEE 802.11wireless LANs (“wi-fi”) 6.4 cellular Internetaccess ArchitectureStandards (e.g., GSM)Mobility 6.5 Principles:addressing and routingto mobile users 6.6 Mobile IP 6.7 Handling mobility incellular networks 6.8 End-to-end mobility 6.9 Mobility and higherlayer protocols6.10 Summary6: Wireless and Mobile Networks6-156: Wireless and Mobile Networks6-164
802.11 LAN ArchitectureIEEE 802.11 Wireless LAN 802.11a 802.11b 5-6 GHz range 2.4-5 GHz unlicensed spectrum Up to 54 Mbps Up to 11 Mbps 802.11g Direct sequence spreadspectrum (DSSS) in physical 2.4-5 GHz rangelayer Up to 54 Mbps All hosts use same chipping 802.11n: multiple antennaecode 2.4-5 GHz range Up to 200 Mbps Wireless host communicatesInternethub, switchor routerAPBSS 1APwith base station Base station accesspoint (AP) Basic Service Set (BSS)(aka “cell”) in infrastructuremode contains: Wireless hosts Access point (AP): basestation Ad hoc mode: hosts only All use CSMA/CA for multiple access All have base-station and ad-hoc network versions6: Wireless and Mobile Networks802.11: Channels, Association6: Wireless and Mobile Networks6-18802.11: Passive/Active ScanningBBS 1 802.11b: 2.4GHz-2.485GHz spectrum divided into11 channels at different frequencies AP admin chooses frequency for AP Interference possible: channel can be same asthat chosen by neighboring AP!AP 1BBS 2112AP 2BBS 1BBS 2AP 16-19AP 2123234H1H1 Host: must associate with an AP Scans channels, listening for beacon framescontaining AP’s name (SSID) and MAC address Selects AP to associate with May perform authentication [Chapter 8] Will typically run DHCP to get IP address inAP’s subnet6: Wireless and Mobile NetworksBSS 26-17Passive Scanning:Active Scanning:(1) beacon frames sent from APs(2) association Request frame sent:H1 to selected AP(3) association Response frame sent:H1 to selected AP(1) Probe Request frame broadcastfrom H1(2) Probes response frame sent fromAPs(3) Association Request frame sent:H1 to selected AP(4) Association Response framesent: H1 to selected AP6: Wireless and Mobile Networks6-205
IEEE 802.11: Multiple Access Avoid collisions:2 IEEE 802.11 MAC Protocol: CSMA/CAnodes transmitting at same time802.11 sender1 If sense channel idle for DIFS then 802.11: CSMA - sense before transmitting Don’t collide with ongoing transmission by other node 802.11: no collision detection! Difficult to receive (sense collisions) when transmitting dueto weak received signals (fading) Can’t sense all collisions in any case: hidden terminal, fading Goal: avoid collisions: CSMA/C(ollision)A(voidance)CABABCSIFSACK6: Wireless and Mobile Networks6-216-22Collision Avoidance: RTS-CTS ExchangeAvoiding Collisions (more)AIdea:allow sender to “reserve” channel rather than randomaccess of data frames: avoid collisions of long data frames Sender first transmits small request-to-send (RTS) packetsto BS using CSMA RTSs may still collide with each other (but they’re short) BS broadcasts clear-to-send CTS in response to RTS RTS heard by all nodes Sender transmits data frame Other stations defer transmissionsBAPRTS(B)RTS(A)reservation collisionRTS(A)CTS(A)CTS(A)DATA (A)avoid data frame collisions completelyusing small reservation packets!6: Wireless and Mobile Networksdatareturn ACK after SIFS (ACK needed dueto hidden terminal problem)space6: Wireless and Mobile NetworksreceiverDIFS802.11 receiver- If frame received OKC’s signalstrengthA’s signalstrengthsendertransmit entire frame (no CD)2 If sense channel busy thenstart random backoff timetimer counts down while channel idletransmit when timer expiresif no ACK, increase random backoffinterval, repeat 2time6-23ACK(A)deferACK(A)6: Wireless and Mobile Networks6-246
RTS-CTS ExchangeRTS-CTS and NAV Uses RTS-CTS exchange to avoid hidden terminalproblem Question: how long should sender “reserve” the channel?RTS Request-to-SendNetwork Allocation Vector (NAV): each message includeslength of time other nodes must wait to sendAny node receiving the RTS cannot transmit for theduration of the transferRTSAAny node overhearing a CTS cannot transmit for theduration of the transferBCDEFPretending a circular range6: Wireless and Mobile Networks6: Wireless and Mobile Networks6-25RTS-CTS and NAVRTS-CTS and NAVRTS Request-to-SendCTS Clear-to-SendRTSABC6-26CTSDEFABCDEFNAV 10NAV remaining duration to keep quiet6: Wireless and Mobile Networks6-276: Wireless and Mobile Networks6-287
RTS-CTS and NAVRTS-CTS and NAV DATA packet follows CTS Successful data reception acknowledged using ACKCTS Clear-to-SendCTSABCDATADEFABCDEFNAV 86: Wireless and Mobile Networks6: Wireless and Mobile Networks6-29RTS-CTS and NAV6-30RTS-CTS and NAVReserved areaACKABCACKDEF6: Wireless and Mobile NetworksA6-31BCDEF6: Wireless and Mobile Networks6-328
802.11 Frame: Addressing2266662frameaddress address addressdurationcontrol123seq address4control802.11 Frame: Addressing0 - 23124payloadCRCAPAddress 4: used onlyin ad hoc modeAddress 1: MAC addressof wireless host or APto receive this frameInternetR1 routerH1R1 MAC addr AP MAC addrAddress 3: MAC addressof router interface towhich AP is attacheddest. addresssource address802.3 frameAddress 2: MAC addressof wireless host or APtransmitting this frameAP MAC addr H1 MAC addr R1 MAC addraddress 1address 2address 3802.11 frame6: Wireless and Mobile Networksframe seq #(for reliable ARQ)duration of reservedtransmission time (RTS/CTS)266662frameaddress address addressdurationcontrol123seq address4control H1 remains in same IP0 - 23124payloadCRCsubnet: IP addresscan remain same Switch: which AP isassociated with H1? rom MoreAPfrag6-34802.11: Mobility within Same Subnet802.11 Frame: More26: Wireless and Mobile Networks6-331Retry11Power Moremgtdata11WEPRsvd(Ch. 5):switch will see framefrom H1 and“remember” whichswitch port can beused to reach H1routerhub orswitchBBS 1AP 1AP 2H1BBS 2frame type(RTS, CTS, ACK, data)6: Wireless and Mobile Networks6-356: Wireless and Mobile Networks6-369
802.11: Advanced CapabilitiesRate AdaptationRate Adaptation10-1 Base station, mobile Multiple rates are supported by each wireless10-2standard according to the channel quality10-3BERdynamically changetransmission rate(physical layermodulation technique)as mobile moves, SNRvaries10-4 10-5 10-6 The channel conditions vary Temporal dimension Spatial dimension (multiuser diversity) Each user has independent channel condition10-7102030SNR(dB)401. SNR decreases, BERincrease as node movesaway from base stationQAM256 (8 Mbps)QAM16 (4 Mbps)BPSK (1 Mbps)operating point Multiple rates can be exploited to improve thetransmission performance2. When BER becomes toohigh, switch to lowertransmission rate but withlower BER6: Wireless and Mobile Networks BCCDT0ADT1BPower ManagementC Mobile devices are battery poweredAÎCready to receiveT2 Idle receive state dominates LAN adapter power consumptionover time How can we power off during idle periods, yet maintainan active session?AÎB 802.11Scheme 2:AÎBAÎD6-38 Current LAN protocols assume stations are alwaysDScheme 1:AÎD6: Wireless and Mobile Networks802.11: Advanced CapabilitiesBAThroughput, latency, etc.6-37A Simple ExampleA802.11b supports 1M, 2M,5.5M and 11Mbps802.11g supports 6M,9M,12M,18M,36M,48M,54MAÎCOf course, scheme 2 is better than scheme 16: Wireless and Mobile NetworksPower Management protocol Allows transceiver to be off as much as possible Is transparent to existing protocols Is flexible to support different applications Possible to trade off throughput for battery life6-396: Wireless and Mobile Networks6-4010
Power Management ApproachInfrastructure Power Management Allow idle stations to go to sleep TIM-IntervalDTIM intervalTime-axisStation’s power save mode stored in APBusy MediumTIM APs buffer packets for sleeping stations AP announces which stations have frames buffered Traffic Indication Map (TIM) sent with every Beaconpower save stations are synchronizedStations will wake up to hear a Beacon Synchronization allows extreme low power operation802.16: WiMAX Like 802.11 & cellular: Less than 10 m diameter 2.4-2.5 GHz radio bandUp to 721 kbps6-42point-to-pointbase station model Replacement for cablesBluetooth specification6: Wireless and Mobile Networks6-41802.15: Personal Area Network Broadcast If TIM indicates frame buffered Station sends PS-Poll and stays awake to receive data6: Wireless and Mobile Networks 802.15: evolved fromDTIM Stations wake up prior to an expected (D)TIM Slaves request permission tosend (to master)Master grants requestsTIM Broadcast frames are also buffered in AP Broadcasts/multicasts are only sent after DTIM DTIM interval is a multiple of TIM interval Time Synchronization Function (TSF) assures AP and TIMBroadcastPS-Poll Tx operationListen for Beacons(mouse, keyboard,headphones) Ad hoc: no infrastructure Master/slaves:DTIMPS Station Power saving stations wake up periodically TIMAP activitySPradius ofcoverageMSPSTransmissions to/frombase station by hostswith omnidirectionalantenna Base station-to-basestation backhaul withpoint-to-point antenna PPM Master deviceS Slave deviceP Parked device (inactive)6: Wireless and Mobile Networks6-43point-to-multipoint Unlike 802.11: Range 6 miles (“cityrather than coffeeshop”) 14 Mbps6: Wireless and Mobile Networks6-4411
802.16: WiMAX: Downlink, Uplink Scheduling Transmission frame6.1 IntroductionDown-link subframe: base station to node Uplink subframe: node to base station pream. DL- ULMAP MAPDLburst 1DLburst 2 Wireless 6.2 Wireless links,characteristics 6.3 IEEE 802.11wireless LANs (“wi-fi”) 6.4 Cellular InternetAccess DLburst nInitial requestSS #1 SS #2maint. conn.SS #k uplink subframedownlink subframeChapter 6 outlinebase station tells nodes who will get to receive (DL map)and who will get to send (UL map), and when WiMAX standard provide mechanism for6.10 Summaryscheduling, but not scheduling algorithm6: Wireless and Mobile NetworksMSC connects cells to wide area net manages call setup (more later!) handles mobility (more later!) covers geographicalregion base station (BS)analogous to 802.11 AP mobile users attachto network through BS MobileSwitchingCenterair-interface:physical and link layerprotocol betweenmobile and BS6: Wireless and Mobile Networks6-45Components of Cellular Network Architecturecellarchitecturestandards (e.g., GSM)Mobility 6.5 Principles:addressing and routingto mobile users 6.6 Mobile IP 6.7 Handling mobility incellular networks 6.8 End-to-end mobility 6.9 Mobility and higherlayer protocolsPublic telephonenetwork, andInternetMobileSwitchingCenter6-46Cellular Networks: the First HopTwo techniques for sharingmobile-to-BS radiospectrum Combined FDMA/TDMA:divide spectrum infrequency channels, divideeach channel into timeslotsfrequencybands CDMA: code divisionmultiple accesstime slotswired network6: Wireless and Mobile Networks6-476: Wireless and Mobile Networks6-4812
Cellular Standards: Brief SurveyCellular Standards: Brief Survey2G systems: voice channels2.5 G systems: voice and data channels IS-136 TDMA: combined FDMA/TDMA (north For those who can’t wait for 3G service: 2G extensionsamerica) GSM (global system for mobile communications):combined FDMA/TDMA General packet radio service (GPRS) Evolved from GSM Data sent on multiple channels (if available)most widely deployed Enhanced data rates for global evolution (EDGE) Also evolved from GSM, using enhanced modulation Data rates up to 384K IS-95 CDMA: code division multiple accessTDMA/FDMACDMA-2000GPRS EDGE UMTSIS-136GSM IS-95 CDMA-2000 (phase 1) Data rates up to 144K Evolved from IS-95Don’t drown in a bowlof alphabet soup: use thisfor reference only6: Wireless and Mobile Networks6: Wireless and Mobile Networks6-49Cellular Standards: Brief SurveyChapter 6 outline3G systems: voice/data6.1 Introduction Universal Mobile Telecommunications Service (UMTS) Data service: High Speed Uplink/Downlink packet Access(HSDPA/HSUPA): 3 Mbps CDMA-2000: CDMA in TDMA slots Data service: 1xEvlution Data Optimized (1xEVDO) up to 14MbpsWireless 6.2 Wireless links,characteristics CDMA 6.3 IEEE 802.11wireless LANs (“wi-fi”) 6.4 Cellular Internet . more (and more interesting) cellular topics due to mobility (staytuned for details)6: Wireless and Mobile Networks6-51Access architecturestandards (e.g., GSM)6-50Mobility 6.5 Principles:addressing and routingto mobile users 6.6 Mobile IP 6.7 Handling mobility incellular networks 6.8 Homeless Mobile IP 6.9 Mobility and higherlayer protocols6.10 Summary6: Wireless and Mobile Networks6-5213
What is Mobility? Spectrum of mobility, from theMobility: Vocabularynetwork perspective:no mobilityhome network: permanent“home” of mobilehome agent: entity that willperform mobility functions onbehalf of mobile, when mobileis remote(e.g., 128.119.40/24)high mobilitymobile wireless user, mobile user,using same accessconnecting/pointdisconnectingfrom networkusing DHCP.mobile user, passingthrough multipleaccess point whilemaintaining ongoingconnections (like cellphone)6: Wireless and Mobile Networksconstant (e.g., 128.119.40.186)address in homenetwork, can always beused to reach mobilee.g., 128.119.40.186correspondent6: Wireless and Mobile Networks6-54How do You Contact a Mobile Friend:visited network: networkin which mobile currentlyresides (e.g., 79.129.13/24)Consider friend frequently changingaddresses, how do you find her?I wonder whereAlice moved to? Search all phoneCare-of-address: addressbooks?in visited network.(e.g., 79,129.13.2) Call her parents? Expect her to let youwide areanetworkcorrespondent: wantsto communicate withmobilePermanent address:6-53Mobility: more VocabularyPermanent address: remainswide areanetworkknow where he/she is?foreign agent: entityin visited networkthat performsmobility functions onbehalf of mobile.6: Wireless and Mobile Networks6-556: Wireless and Mobile Networks6-5614
Mobility: ApproachesMobility: Approaches Let routing handle it: routers advertise permanent Let routing handle it: routers advertise permanent Let end-systems handle it: Indirect routing: communication from Let end-systems handle it: Indirect routing: communication fromaddress of mobile-nodes-in-residence via usualrouting table exchange. Routing tables indicate where each mobile located No changes to end-systemscorrespondent to mobile goes through homeagent, then forwarded to remote Direct routing: correspondent gets foreignaddress of mobile, sends directly to mobile6: Wireless and Mobile Networksnotaddress of mobile-nodes-in-residencevia usualscalablerouting table exchange.to millions of routing tables indicatemobiles where each mobile located no changes to end-systemscorrespondent to mobile goes through homeagent, then forwarded to remote Direct routing: correspondent gets foreignaddress of mobile, sends directly to mobile6: Wireless and Mobile Networks6-57Mobility: Registration6-58Mobility via Indirect Routingvisited networkhome network12wide areanetworkforeign agent contacts homeagent home: “this mobile isresident in my network”mobile contactsforeign agent onentering visitednetworkEnd result: Foreign agent knows about mobile Home agent knows location of mobile6: Wireless and Mobile Networksforeign agentreceives packets,forwards to mobilehome agent interceptspackets, forwards toforeign agent6-59homenetworkvisitednetwork3wide areanetworkcorrespondentaddresses packetsusing home addressof mobile124mobile repliesdirectly tocorrespondent6: Wireless and Mobile Networks6-6015
Indirect Routing: CommentsIndirect Routing: Moving between Networks Mobile uses two addresses:permanent address: used by correspondent (hencemobile location is transparent to correspondent) care-of-address: used by home agent to forwarddatagrams to mobile Foreign agent functions may be done by mobile itself Triangle routing: correspondent-home-networkmobile Inefficient whencorrespondent, mobileare in same network 6: Wireless and Mobile Networksforeign agentreceives packets,forwards to mobilecorrespondentrequests, receivesforeign address ofmobile13 Mobility, changing foreign networkstransparent: on going connections can bemaintained!6: Wireless and Mobile Networks6-62 Overcome triangle routing problemvisitednetwork42Registers with new foreign agentNew foreign agent registers with home agent Home agent update care-of-address for mobile Packets continue to be forwarded to mobile (butwith new care-of-address) Mobility via Direct Routing: Commentshomenetworkwide areanetworknetwork6-61Mobility via Direct Routingcorrespondent forwardsto foreign agent Suppose mobile user moves to another Non-transparent to correspondent:correspondent must get care-of-addressfrom home agent What if mobile changes visited network?4mobile repliesdirectly tocorrespondent6: Wireless and Mobile Networks6-636: Wireless and Mobile Networks6-6416
Accommodating Mobility with Direct Routing Anchor foreign agent: FA in first visited network6.1 Introduction Data always routed first to anchor FA When mobile moves: new FA arranges to have dataforwarded from old FA (chaining)Wireless 6.2 Wireless links,characteristicsforeign net visitedat session startwide rrespondent 2wireless LANs (“wi-fi”) 6.4 Cellular InternetAccess3new foreignagentCDMA 6.3 IEEE 802.1145Chapter 6 outline newforeignnetwork6: Wireless and Mobile Networks architecturestandards (e.g., GSM)Mobility 6.5 Principles:addressing and routingto mobile users 6.6 Mobile IP 6.7 Handling mobility incellular networks 6.8 End-to-end mobility 6.9 Mobility and higherlayer protocols6.10 Summary6: Wireless and Mobile Networks6-65Mobile IP6-66Mobile IP: Indirect Routing RFC 3344foreign-agent-to-mobile packetpacket sent by home agent to foreignagent: a packet within a packet Has many features we’ve seen: Home agents, foreign agents, foreign-agentregistration, care-of-addresses, encapsulation(packet-within-a-packet)dest: 79.129.13.2 Three components to standard: Indirect routing of datagrams Agent discovery Registration with home agent6: Wireless and Mobile Networksdest: 128.119.40.186dest: 128.119.40.186Permanent address:128.119.40.186dest: 128.119.40.186Care-of address:79.129.13.2packet sent bycorrespondent6-676: Wireless and Mobile Networks6-6817
Mobile IP: Agent DiscoveryMobile IP: Registration Example Agent advertisement: foreign/home agentshome agentHA: 128.119.40.7advertise service by broadcasting ICMP messages(typefield 9)visited network: 79.129.13/24ICMP agent adv.COA: 79.129.13.2 .0168type 9checksumregistration req.lengthregistration lifetimeCOA: 79.129.13.2HA: 128.119.40.7MA: 128.119.40.186Lifetime: 9999identification: 714encapsulation format .standardICMP fieldsrouter addresstype 16registration req.COA: 79.129.13.2HA: 128.119.40.7MA: 128.119.40.186Lifetime: 9999identification:714 .sequence #RBHFMGVbitsreserved0 or more care-ofaddressesregistration replytimemobility agentadvertisementextension6: Wireless and Mobile NetworksMSCMSCMSCdifferent cellular networks,operated by different providers6: Wireless and Mobile NetworksHA: 128.119.40.7MA: 128.119.40.186Lifetime: 4999Identification: 714 .6-70Home network: network of cellular provider yousubscribe to (e.g., Sprint PCS, Verizon) Home location register (HLR): database in homenetwork containing permanent cell phone #,profile information (services, preferences,billing), information about current location(could be in another network) Visited network: network in which mobile currentlyresides Visitor location register (VLR): database withentry for each user currently in network Could be home networkwired publictelephonenetworkMSCregistration replyHandling Mobility in Cellular Networks correspondentMSCHA: 128.119.40.7MA: 128.119.40.186Lifetime: 4999Identification: 714encapsulation format .6: Wireless and Mobile Networks6-69Components of Cellular Network Architecturerecall:Mobile agentMA: 128.119.40.18624code 0H,F bits: homeand/or foreign agentR bit: registrationrequiredforeign agentCOA: 79.129.13.26-716: Wireless and Mobile Networks6-7218
GSM: Indirect Routing to MobilehomenetworkHLR2home MSC consults HLR,gets roaming number ofmobile in visited networkGSM: Handoff with Common MSC Handoff goal: route call viacorrespondenthomeMobileSwitchingCenterVLR ephonenetworkvisitednetworkoldroutingVLR MobileSwitchingCenter 254736 new BSSnew BSS Handoff initiated by old BSS6-74GSM: Handoff between MSCs1. old BSS informs MSC of impendinghandoff, provides list of 1 new BSSs2. MSC sets up path (allocates resources)to new BSS3. new BSS allocates radio channel foruse by mobile4. new BSS signals MSC, old BSS: ready5. old BSS tells mobile: perform handoff tonew BSS6. mobile, new BSS signal to activate newchannel7. mobile signals via new BSS to MSC:handoff complete. MSC reroutes call8 MSC-old-BSS resources released6: Wireless and Mobile Networks6: Wireless and Mobile Networks6-73GSM: Handoff with Common MSCold BSSnewroutingold BSSStronger signal to/from newBSS (continuing connectivity,less battery drain)Load balance: free up channelin current BSSGSM doesn’t mandate why toperform handoff (policy), onlyhow (mechanism)MSC in visited network completescall through base station to mobile6: Wireless and Mobile Networks8 SwitchingCentercall routedto home networkhome MSC sets up 2nd leg of callto MSC in visited networkmobileuser1new base station (withoutinterruption) Reasons for handoff:6-75 home networkcorrespondentHomeMSCAnchor MSC: first MSCvisited during cal call remains routedthrough anchor MSC New MSCs add on to endanchor MSCPSTNMSCMSCMSC(a) before handoffof MSC chain as mobilemoves to new MSC IS-41 allows optionalpath minimization stepto shorten multi-MSCchain6: Wireless and Mobile Networks6-7619
Mobility: GSM versus Mobile IPGSM: Handoff between MSCsGSM element home networkAnchor MSC: first MSCvisited during cal correspondentHomeMSCcall remains routedthrough anchor MSC New MSCs add on to endanchor MSCof MSC chain as mobilemoves to new MSC IS-41 allows optionalpath minimization stepto shorten multi-MSCchainPSTNMSCMSCMSC(b) after handoff6: Wireless and Mobile NetworksComment on GSM elementMobile IP elementHome systemNetwork to which mobile user’s permanentphone number belongsHomenetworkGateway MobileSwitching Center, or“home MSC”. HomeLocation Register(HLR)Home MSC: point of contact to obtain routableaddress of mobile user. HLR: database inhome system containing permanent phonenumber, profile information, current location ofmobile user, subscription informationHome agentVisited SystemNetwork other than home system wheremobile user is currently residingVisitednetworkVisited Mobileservices SwitchingCenter.Visitor LocationRecord (VLR)Visited MSC: responsible for setting up callsto/from mobile nodes in cells associated withMSC. VLR: temporary database entry invisited system, containing subscriptioninformation for each visiting mobile userForeign agentMobile StationRoaming Number(MSRN), or “roamingnumber”Routable address for telephone call segmentbetween home MSC and visited MSC, visibleto neither the mobile nor the correspondent.Care-ofaddress6: Wireless and Mobile Networks6-77Chapter 6 outlineEnd-to-End Mobility6.1 Introduction Re-visit Mobile IP solution Network centric Home Agent needs handle not only signaling butalso data packets Network is hard to changeWireless 6.2 Wireless links,characteristics CDMA 6.3 IEEE 802.11wireless LANs (“wi-fi”) 6.4 Cellular InternetAccess architecturestandards (e.g., GSM)Mobility 6.5 Principles:addressing and routingto mobile users 6.6 Mobile IP 6.7 Handling mobility incellular networks 6.8 End-to-end mobility 6.9 Mobility and higherlayer protocols6-78 End-to-end mobility Mobility Easysolution without Home Agent!to deploy6.10 Summary6: Wireless and Mobile Networks6-796: Wireless and Mobile Networks6-8020
Local Address TranslationTransparent to Legacy Applications Solution Issue IP2, port1 IP1, port1 A IP2, port1 IP1, port1 A IP1, port1 IP1, port1 CAA IP2, port1 IP1, port1 C IP2, port1 IP1, port2 Receives Packetwith IP1, port1 IP1, port1 ConnectionsOld Address andPort InfoNew Addressand Port InfoMapping toApplicationConn A IP1, Port1 IP2, Port1 IP1, Port1 BNew Addressand Port InfoMapping toApplicationConn A IP1, Port1 IP2, Port1 IP1, Port1 IP1, Port1 IP1, Port2 IP1, port1 216.1 IntroductionBAC36: Wireless and Mobile NetworksSubscribe/Notify serviceWireless 6.2 Wireless links,characteristics65.23.64.1403 wireless LANs (“wi-f
IS-95, CDMA, GSM 2G UMTS/WCDMA, CDMA2000 3G 802.15 802.11b 802.11a,g UMTS/WCDMA-HSPDA, CDMA2000-1xEVDO 3G cellular enhanced 802.16 (WiMAX) 802.11a,g point-to-point . Wireless and Mobile Networks 6-10 Wireless Network Taxonomy single hop multiple hops infrastructure (e.g., APs) no infrastructure host connects to base station (WiFi, WiMAX .
Part One: Heir of Ash Chapter 1 Chapter 2 Chapter 3 Chapter 4 Chapter 5 Chapter 6 Chapter 7 Chapter 8 Chapter 9 Chapter 10 Chapter 11 Chapter 12 Chapter 13 Chapter 14 Chapter 15 Chapter 16 Chapter 17 Chapter 18 Chapter 19 Chapter 20 Chapter 21 Chapter 22 Chapter 23 Chapter 24 Chapter 25 Chapter 26 Chapter 27 Chapter 28 Chapter 29 Chapter 30 .
TO KILL A MOCKINGBIRD. Contents Dedication Epigraph Part One Chapter 1 Chapter 2 Chapter 3 Chapter 4 Chapter 5 Chapter 6 Chapter 7 Chapter 8 Chapter 9 Chapter 10 Chapter 11 Part Two Chapter 12 Chapter 13 Chapter 14 Chapter 15 Chapter 16 Chapter 17 Chapter 18. Chapter 19 Chapter 20 Chapter 21 Chapter 22 Chapter 23 Chapter 24 Chapter 25 Chapter 26
DEDICATION PART ONE Chapter 1 Chapter 2 Chapter 3 Chapter 4 Chapter 5 Chapter 6 Chapter 7 Chapter 8 Chapter 9 Chapter 10 Chapter 11 PART TWO Chapter 12 Chapter 13 Chapter 14 Chapter 15 Chapter 16 Chapter 17 Chapter 18 Chapter 19 Chapter 20 Chapter 21 Chapter 22 Chapter 23 .
Mobile 3G/4G, pushing wireless boundaries to enable the best mobile experiences 2 Mobile connectivity is an amazing technical achievement, 4 critical to the mobile experience Wireless fundamentals are the foundation to mobile powered by Mobile 3G/4G technologies Appreciating the magic of mobile requires un
Wireless, Mobile Networks 6-3 Elements of a wireless network network infrastructure Wireless, Mobile Networks 6-4 . CDMA, GSM 2.5G: UMTS/WCDMA, CDMA2000 802.11a,g 3G: UMTS/WCDMA-HSPDA, CDMA2000-1xEVDO 4G: LTWE WIMAX 802.11a,g point-to-point 200 802.11n s) Wireless, Mobile Networks 6-8 infrastructure mode !
Wireless# Guide to Wireless Communications Chapter 1 Introduction to Wireless Communications . Wireless Local Area Network (WLAN) - Extension of a wired LAN Connecting to it through a device called a wireless . network Each computer on the WLAN has a wireless network interface card (NIC) - With an antenna built into it .
About the husband’s secret. Dedication Epigraph Pandora Monday Chapter One Chapter Two Chapter Three Chapter Four Chapter Five Tuesday Chapter Six Chapter Seven. Chapter Eight Chapter Nine Chapter Ten Chapter Eleven Chapter Twelve Chapter Thirteen Chapter Fourteen Chapter Fifteen Chapter Sixteen Chapter Seventeen Chapter Eighteen
18.4 35 18.5 35 I Solutions to Applying the Concepts Questions II Answers to End-of-chapter Conceptual Questions Chapter 1 37 Chapter 2 38 Chapter 3 39 Chapter 4 40 Chapter 5 43 Chapter 6 45 Chapter 7 46 Chapter 8 47 Chapter 9 50 Chapter 10 52 Chapter 11 55 Chapter 12 56 Chapter 13 57 Chapter 14 61 Chapter 15 62 Chapter 16 63 Chapter 17 65 .
