Ch. 6: Wireless And Mobile Networks
Ch. 6: Wireless and Mobile NetworksBackground: # wireless (mobile) phone subscribers now exceeds #wired phone subscribers!# wireless Internet-connected devices soon to exceed# wireline Internet-connected devices laptops, Internet-enabled phones promise anytime untetheredInternet access two important (but different) challenges wireless: communication over wireless link mobility: handling the mobile user who changes point ofattachment to networkWireless, Mobile Networks6-1Chapter 6 outline6.1 IntroductionMobilityWireless6.5 Principles: addressing androuting to mobile users6.6 Mobile IP6.7 Handling mobility incellular networks6.8 Mobility and higher-layerprotocols6.2 Wireless links,characteristics CDMA6.3 IEEE 802.11 wirelessLANs (“Wi-Fi”)6.4 Cellular Internet Access architecture standards (e.g., GSM)6.9 SummaryWireless, Mobile Networks6-21
Elements of a wireless networknetworkinfrastructureWireless, Mobile Networks6-3Elements of a wireless networkwireless hosts networkinfrastructurelaptop, smartphonerun applicationsmay be stationary (non-mobile) or mobile wireless does not alwaysmean mobilityWireless, Mobile Networks6-42
Elements of a wireless networkbase station networkinfrastructuretypically connected towired networkrelay - responsible forsending packets betweenwired network andwireless host(s) in its“area” e.g., cell towers,802.11 access pointsWireless, Mobile Networks6-5Elements of a wireless networkwireless link networkinfrastructure typically used to connectmobile(s) to base stationalso used as backbonelinkmultiple access protocolcoordinates link accessvarious data rates,transmission distanceWireless, Mobile Networks6-63
Characteristics of selected wireless linksData rate (Mbps)200545-11802.11n802.11a,g41802.11a,g point-to-point802.11b4G: LTWE WIMAX3G: UMTS/WCDMA-HSPDA, CDMA2000-1xEVDO802.15.3842.5G: UMTS/WCDMA, CDMA2000.0562G: IS-95, CDMA, rangeoutdoor200m – 4 Km5Km – 20 KmWireless, Mobile Networks6-7Elements of a wireless networkinfrastructure mode networkinfrastructurebase station connectsmobiles into wirednetworkhandoff: mobile changesbase station providingconnection into wirednetworkWireless, Mobile Networks6-84
Elements of a wireless networkad hoc mode no base stations nodes can onlytransmit to othernodes within linkcoverage nodes organizethemselves into anetwork: routeamong themselvesWireless, Mobile Networks6-9Wireless network taxonomysingle hopinfrastructure(e.g., APs)noinfrastructurehost connects tobase station (WiFi,WiMAX, cellular)which connects tolarger Internetno base station, noconnection to largerInternet (Bluetooth,ad hoc nets)multiple hopshost may have torelay through severalwireless nodes toconnect to largerInternet: mesh netno base station, noconnection to largerInternet. May have torelay to reach othera given wireless nodeMANET,VANETWireless, Mobile Networks 6-105
Chapter 6 outline6.1 IntroductionMobilityWireless6.5 Principles: addressing androuting to mobile users6.6 Mobile IP6.7 Handling mobility incellular networks6.8 Mobility and higher-layerprotocols6.2 Wireless links,characteristics CDMA6.3 IEEE 802.11 wirelessLANs (“Wi-Fi”)6.4 Cellular Internet Access architecture standards (e.g., GSM)6.9 SummaryWireless, Mobile Networks 6-11Wireless Link Characteristics (1)important differences from wired link . decreased signal strength: radio signal attenuates as itpropagates through matter (path loss) interference from other sources: standardized wirelessnetwork frequencies (e.g., 2.4 GHz) shared by otherdevices (e.g., phone); devices (motors) interfere aswell multipath propagation: radio signal reflects off objectsground, arriving ad destination at slightly differenttimes . make communication across (even a point to point)wireless link much more “difficult”Wireless, Mobile Networks 6-126
Wireless Link Characteristics (2) SNR: signal-to-noise ratio10-1 larger SNR – easier toextract signal from noise (a“good thing”)SNR versus BER tradeoffs given physical layer: increasepower - increase SNR- decrease BER given SNR: choose physical layerthat meets BER requirement,giving highest thruput SNR may change withmobility: dynamically adaptphysical layer (modulationtechnique, rate)10-3BER 10-210-410-510-610-710203040SNR(dB)QAM256 (8 Mbps)QAM16 (4 Mbps)BPSK (1 Mbps)Wireless, Mobile Networks 6-13Wireless network characteristicsMultiple wireless senders and receivers create additionalproblems (beyond multiple access):BACCABHidden terminal problem B, A hear each otherB, C hear each otherA, C can not hear each othermeans A, C unaware of theirinterference at BC’s signalstrengthA’s signalstrengthspaceSignal attenuation: B, A hear each otherB, C hear each otherA, C can not hear each otherinterfering at BWireless, Mobile Networks 6-147
Code Division Multiple Access (CDMA) unique “code” assigned to each user; i.e., code setpartitioning all users share same frequency, but each user has own“chipping” sequence (i.e., code) to encode data allows multiple users to “coexist” and transmitsimultaneously with minimal interference (if codes are“orthogonal”)encoded signal (original data) X (chippingsequence) decoding: inner-product of encoded signal andchipping sequence Wireless, Mobile Networks 6-15CDMA encode/decodesenderdatabitscodeZi,m di.cmd0 1-1 -1 -11-11 1 1-1 -1 -1slot 1-1slot 1channeloutput1-11 1 1 1 1 11d1 -11 1 1channel output Zi,m-1 -1 -1slot 01-1-1 -1 -1slot 0channeloutputMDi Σ Zi,m.cmm 1receivedinput-1 -1 -1codereceiver1 1 1 1 1 11-11 1 1-1 -1 -1-11-11 1 1-1 -1 -1slot 1M11-1-1 -1 -1slot 0d0 1d1 -1slot 1channeloutputslot 0channeloutputWireless, Mobile Networks 6-168
CDMA: two-sender interferenceWireless, Mobile Networks 6-17Chapter 6 outline6.1 IntroductionMobilityWireless6.5 Principles: addressing androuting to mobile users6.6 Mobile IP6.7 Handling mobility incellular networks6.8 Mobility and higher-layerprotocols6.2 Wireless links,characteristics CDMA6.3 IEEE 802.11 wirelessLANs (“Wi-Fi”)6.4 Cellular Internet Access architecture standards (e.g., GSM)6.9 SummaryWireless, Mobile Networks 6-189
IEEE 802.11 Wireless LAN802.11b 2.4-5 GHz unlicensed spectrum up to 11 Mbps direct sequence spread spectrum(DSSS) in physical layer all hosts use same chippingcode 802.11a 5-6 GHz range up to 54 Mbps802.11g 2.4-5 GHz range up to 54 Mbps802.11n: multiple antennae 2.4-5 GHz range up to 200 Mbpsall use CSMA/CA for multiple accessall have base-station and ad-hoc network versionsWireless, Mobile Networks 6-19802.11 LAN architecture Internetwireless hostcommunicates with basestation base station access point(AP)hub, switchor router Basic Service Set (BSS) (aka“cell”) in infrastructuremode contains: wireless hosts access point (AP): basestation ad hoc mode: hosts onlyBSS 1BSS 2Wireless, Mobile Networks 6-2010
802.11: Channels, association 802.11b: 2.4GHz-2.485GHz spectrum divided into 11channels at different frequencies AP admin chooses frequency for AP interference possible: channel can be same as thatchosen by neighboring AP! host: must associate with an AP scans channels, listening for beacon frames containingAP’s name (SSID) and MAC address selects AP to associate with may perform authentication [Chapter 8] will typically run DHCP to get IP address in AP’ssubnetWireless, Mobile Networks 6-21802.11: passive/active scanningBBS 1AP 1BBS 1BBS 2112BBS 21AP 2AP 12323AP 24H1H1passive scanning:active scanning:(1) beacon frames sent from APs(2) association Request frame sent: H1 toselected AP(3) association Response frame sent fromselected AP to H1(1) Probe Request frame broadcastfrom H1(2) Probe Response frames sentfrom APs(3) Association Request frame sent:H1 to selected AP(4) Association Response frame sentfrom selected AP to H1Wireless, Mobile Networks 6-2211
IEEE 802.11: multiple access avoid collisions: 2 nodes transmitting at same time802.11: 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 due to weakreceived signals (fading) can’t sense all collisions in any case: hidden terminal, fading goal: avoid collisions: CSMA/C(ollision)A(voidance)ABACBCC’s signalstrengthA’s signalstrengthspaceWireless, Mobile Networks 6-23IEEE 802.11 MAC Protocol: CSMA/CA802.11 sender1 if sense channel idle for DIFS thensendertransmit entire frame (no CD)2 if sense channel busy thenDIFSstart random backoff timetimer counts down while channel idletransmit when timer expiresif no ACK, increase random backoff interval,repeat 2802.11 receiver- if frame received OKreceiverdataSIFSACKreturn ACK after SIFS (ACK needed due tohidden terminal problem)Wireless, Mobile Networks 6-2412
Avoiding collisions (more)idea: allow sender to “reserve” channel rather than randomaccess of data frames: avoid collisions of long dataframes 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 RTSCTS heard by all nodes sender transmits data frame other stations defer transmissionsavoid data frame collisions completelyusing small reservation packets!Wireless, Mobile Networks 6-25Collision Avoidance: RTS-CTS exchangeABAPRTS(B)RTS(A)reservation collisionRTS(A)CTS(A)CTS(A)DATA (A)defertimeACK(A)ACK(A)Wireless, Mobile Networks 6-2613
802.11 frame: addressing226662frameaddress address addressdurationcontrol123Address 1: MAC addressof wireless host or APto receive this frameAddress 2: MAC addressof wireless host or APtransmitting this frame6seq address4control0 - 23124payloadCRCAddress 4: used only inad hoc modeAddress 3: MAC addressof router interface towhich AP is attachedWireless, Mobile Networks 6-27802.11 frame: addressingR1 routerH1InternetR1 MAC addr H1 MAC addrdest. addresssource address802.3 frameAP MAC addr H1 MAC addr R1 MAC addraddress 1address 2address 3802.11 frameWireless, Mobile Networks 6-2814
802.11 frame: moreframe seq #(for RDT)duration of reservedtransmission time (RTS/CTS)226662Protocolversion2Type62frameaddress address addressdurationcontrol123seq address4control4111SubtypeToAPFromAPMorefrag110 - 23124payloadCRC1Power MoreRetrymgtdata11WEPRsvdframe type(RTS, CTS, ACK, data)Wireless, Mobile Networks 6-29802.11: mobility within same subnetH1 remains in sameIP subnet: IP addresscan remain same switch: which AP isassociated with H1? self-learning (Ch. 5):switch will see framefrom H1 and“remember” whichswitch port can beused to reach H1BBS 1H1BBS 2Wireless, Mobile Networks 6-3015
802.11: advanced capabilitiesRate adaptationbase station, mobiledynamically changetransmission rate(physical layermodulation technique) asmobile moves, SNRvariesQAM256 (8 Mbps)QAM16 (4 Mbps)BPSK (1 Mbps)operating point10-210-3BER 10-110-410-510-610-7102030SNR(dB)401. SNR decreases, BERincrease as node movesaway from base station2. When BER becomes toohigh, switch to lowertransmission rate but withlower BERWireless, Mobile Networks 6-31802.11: advanced capabilitiesPower management node-to-AP: “I am going to sleep until nextbeacon frame” AP knows not to transmit frames to this node node wakes up before next beacon frame beacon frame: contains list of mobiles with AP-to-mobile frames waiting to be sent node will stay awake if AP-to-mobile frames to besent; otherwise sleep again until next beacon frameWireless, Mobile Networks 6-3216
802.15: personal area network less than 10 m diameterreplacement for cables (mouse,keyboard, headphones)ad hoc: no infrastructuremaster/slaves: slaves request permission to send(to master) master grants requests 802.15: evolved from Bluetoothspecification 2.4-2.5 GHz radio band up to 721 kbpsPSPradius ofcoverageMSPSPM Master deviceS Slave deviceP Parked device (inactive)Wireless, Mobile Networks 6-33Chapter 6 outline6.1 IntroductionWireless6.2 Wireless links,characteristics CDMA6.3 IEEE 802.11 wirelessLANs (“Wi-Fi”)6.4 Cellular Internet Access architecture standards (e.g., GSM)Mobility6.5 Principles: addressing androuting to mobile users6.6 Mobile IP6.7 Handling mobility incellular networks6.8 Mobility and higher-layerprotocols6.9 SummaryWireless, Mobile Networks 6-3417
Components of cellular network architectureMSCconnects cells to wired tel. net.manages call setup (more later!) handles mobility (more later!) cellcovers geographicalregion base station (BS)analogous to 802.11AP mobile users attach tonetwork through BS air-interface: physicaland link layer protocolbetween mobile andBS MobileSwitchingCenterPublic telephonenetworkMobileSwitchingCenterwired networkWireless, Mobile Networks 6-35Cellular networks: the first hopTwo techniques for sharingmobile-to-BS radio spectrum combined FDMA/TDMA:divide spectrum in frequencychannels, divide each channelinto time slots CDMA: code division multiplefrequencyaccesstime slotsbandsWireless, Mobile Networks 6-3618
2G (voice) network architectureBase station system endBase transceiver station (BTS)Base station controller (BSC)Mobile Switching Center (MSC)Mobile subscribersWireless, Mobile Networks 6-373G (voice data) network onenetworkGatewayMSCGSGSNKey insight: new cellular datanetwork operates in parallel(except at edge) with existingcellular voice network voice network unchanged in core data network operates in parallelPublicInternetGGSNServing GPRS Support Node (SGSN)Gateway GPRS Support Node (GGSN)Wireless, Mobile Networks 6-3819
3G (voice data) network onenetworkGatewayMSCGSGSNPublicInternetGGSNradio interface(WCDMA, HSPA)radio access networkUniversal Terrestrial RadioAccess Network (UTRAN)core networkGeneral Packet Radio Service(GPRS) Core NetworkpublicInternetWireless, Mobile Networks 6-39Chapter 6 outline6.1 IntroductionWireless6.2 Wireless links,characteristics CDMA6.3 IEEE 802.11 wirelessLANs (“Wi-Fi”)6.4 Cellular Internet Access architecture standards (e.g., GSM)Mobility6.5 Principles: addressing androuting to mobile users6.6 Mobile IP6.7 Handling mobility incellular networks6.8 Mobility and higher-layerprotocols6.9 SummaryWireless, Mobile Networks 6-4020
What is mobility? spectrum of mobility, from the network perspective:no mobilitymobile wireless user,using same accesspointhigh mobilitymobile user,connecting/disconnecting fromnetwork usingDHCP.mobile user, passingthrough multipleaccess point whilemaintaining ongoingconnections (like cellphone)Wireless, Mobile Networks 6-41Mobility: vocabularyhome network: permanent“home” of mobile(e.g., 128.119.40/24)home agent: entity that willperform mobility functions onbehalf of mobile, when mobile isremotewide areanetworkpermanent address:address in homenetwork, can always beused to reach mobilee.g., 128.119.40.186Wireless, Mobile Networks 6-4221
Mobility: more vocabularypermanent address: remainsconstant (e.g., 128.119.40.186)visited network: network inwhich mobile currentlyresides (e.g., 79.129.13/24)care-of-address: addressin visited network.(e.g., 79,129.13.2)wide areanetworkcorrespondent: wantsto communicate withmobileforeign agent: entity invisited network thatperforms mobilityfunctions on behalf ofmobile.Wireless, Mobile Networks 6-43How do you contact a mobile friend:Consider friend frequently changingaddresses, how do you find her? I wonder whereAlice moved to?search all phone books?call her parents?expect her to let youknow where he/she is?Wireless, Mobile Networks 6-4422
Mobility: approaches let routing handle it: routers advertise permanent address ofmobile-nodes-in-residence via usual routing table exchange. routing tables indicate where each mobile located no changes to end-systemslet end-systems handle it: indirect routing: communication from correspondent tomobile goes through home agent, then forwarded toremote direct routing: correspondent gets foreign address ofmobile, sends directly to mobileWireless, Mobile Networks 6-45Mobility: approaches let routing handle it: routers advertise permanent address ofnot via usual routing table exchange.mobile-nodes-in-residencescalable routing tables indicatewhere each mobile locatedto millions of no changes to end-systemsmobileslet end-systems handle it: indirect routing: communication from correspondent tomobile goes through home agent, then forwarded toremote direct routing: correspondent gets foreign address ofmobile, sends directly to mobileWireless, Mobile Networks 6-4623
Mobility: registrationvisited networkhome network12 areawidenetworkmobile contactsforeign agent onentering visitednetworkforeign agent contacts homeagent home: “this mobile isresident in my network”end result: foreign agent knows about mobile home agent knows location of mobileWireless, Mobile Networks 6-47Mobility via indirect routinghome agent interceptspackets, forwards toforeign agentforeign agentreceives packets,forwards to mobilehomenetwork31correspondentaddresses packetsusing home addressof mobilevisitednetworkwide areanetwork24mobile repliesdirectly tocorrespondentWireless, Mobile Networks 6-4824
Indirect Routing: comments 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 mobileforeign agent functions may be done by mobile itself triangle routing: correspondent-home-network-mobile inefficient whencorrespondent, mobileare in same networkWireless, Mobile Networks 6-49Indirect routing: moving between networkssuppose mobile user moves to another network registers with new foreign agent new 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, changing foreign networks transparent: ongoing connections can be maintained! Wireless, Mobile Networks 6-5025
Mobility via direct routingforeign agentreceives packets,forwards to mobilecorrespondent forwardsto foreign agentvisitednetworkhomenetwork3214mobile repliesdirectly tocorrespondentcorrespondentrequests, receivesforeign address ofmobileWireless, Mobile Networks 6-51Mobility via direct routing: commentsovercome triangle routing problem non-transparent to correspondent: correspondentmust get care-of-address from home agent what if mobile changes visited network?1324Wireless, Mobile Networks 6-5226
Accommodating mobility with direct routinganchor foreign agent: FA in first visited network data always routed first to anchor FA when mobile moves: new FA arranges to havedata forwarded from old FA (chaining) foreign net visitedat session startwide espondentagent3new foreignagentnewforeignnetworkWireless, Mobile Networks 6-53Chapter 6 outline6.1 IntroductionWireless6.2 Wireless links,characteristics CDMA6.3 IEEE 802.11 wirelessLANs (“Wi-Fi”)6.4 Cellular Internet Access architecture standards (e.g., GSM)Mobility6.5 Principles: addressing androuting to mobile users6.6 Mobile IP6.7 Handling mobility incellular networks6.8 Mobility and higher-layerprotocols6.9 SummaryWireless, Mobile Networks 6-5427
Mobile IPRFC 3344 has many features we’ve seen: home agents, foreign agents, foreign-agent registration,care-of-addresses, encapsulation (packet-within-a-packet) three components to standard: indirect routing of datagrams agent discovery registration with home agentWireless, Mobile Networks 6-55Mobile IP: indirect routingforeign-agent-to-mobile packetpacket sent by home agent to foreignagent: a packet within a packetdest: 79.129.13.2dest: 128.119.40.186dest: 128.119.40.186Permanent address:128.119.40.186dest: 128.119.40.186Care-of address:79.129.13.2packet sent bycorrespondentWireless, Mobile Networks 6-5628
Mobile IP: agent discovery agent advertisement: foreign/home agents advertiseservice by broadcasting ICMP messages (typefield 9)H,F bits: home and/orforeign agentR bit: registrationrequiredWireless, Mobile Networks 6-57Mobile IP: registration exampleWireless, Mobile Networks 6-5829
Components of cellular network architecturerecall:correspondentwired publictelephonenetworkMSCMSCMSCMSCMSCdifferent cellular networks,operated by different providersWireless, Mobile Networks 6-59Handling mobility in cellular networks home network: network of cellular provider yousubscribe to (e.g., Sprint PCS, Verizon) home location register (HLR): database in home networkcontaining permanent cell phone #, profile information(services, preferences, billing), information aboutcurrent location (could be in another network) visited network: network in which mobile currentlyresides visitor location register (VLR): database with entry foreach user currently in network could be home networkWireless, Mobile Networks 6-6030
GSM: indirect routing to mobilehomenetworkHLR2home MSC consults HLR,gets roaming number ofmobile in visited rkcall routedto home networkhome MSC sets up 2nd leg of callto MSC in visited networkmobileuservisitednetworkMSC in visited network completescall through base station to mobileWireless, Mobile Networks 6-61GSM: handoff with common MSC VLRMobileSwitchingCenteroldroutingold BSS handoff goal: route call vianew base station (withoutinterruption)reasons for handoff: stronger signal to/from new BSS(continuing connectivity, lessbattery drain) load balance: free up channel incurrent BSS GSM doesn’t mandate why toperform handoff (policy), onlyhow (mechanism)newroutingnew BSS handoff initiated by old BSSWireless, Mobile Networks 6-6231
GSM: handoff with common MSCVLRMobileSwitchingCenter 24178old BSS356new BSS1. 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 releasedWireless, Mobile Networks 6-63GSM: handoff between MSCs home networkcorrespondentHomeMSCanchor MSCMSC PSTNMSCMSC anchor MSC: first MSCvisited during call call remains routedthrough anchor MSCnew MSCs add on to end ofMSC chain as mobile movesto new MSCoptional path minimizationstep to shorten multi-MSCchain(a) before handoffWireless, Mobile Networks 6-6432
GSM: handoff between MSCs home networkcorrespondentHomeMSCanchor MSC PSTNMSCMSCMSC anchor MSC: first MSCvisited during call call remains routedthrough anchor MSCnew MSCs add on to end ofMSC chain as mobile movesto new MSCoptional path minimizationstep to shorten multi-MSCchain(b) after handoffWireless, Mobile Networks 6-65Mobility: GSM versus Mobile IPGSM elementHome systemComment on GSM elementMobile IP elementNetwork to which mobile user’s permanentphone number belongsHome networkGateway MobileHome MSC: point of contact to obtain routableSwitching Center, or address of mobile user. HLR: database in“home MSC”. Home home system containing permanent phoneLocation Registernumber, profile information, current location of(HLR)mobile 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“roaming number”Routable address for telephone call segmentbetween home MSC and visited MSC, visibleto neither the mobile nor the correspondent.Care-of-addressWireless, Mobile Networks 6-6633
Wireless, mobility: impact on higher layer protocols logically, impact should be minimal best effort service model remains unchanged TCP and UDP can (and do) run over wireless, mobile but performance-wise: packet loss/delay due to bit-errors (discarded packets,delays for link-layer retransmissions), and handoff TCP interprets loss as congestion, will decrease congestionwindow un-necessarily delay impairments for real-time traffic limited bandwidth of wireless linksWireless, Mobile Networks 6-67Chapter 6 summaryWireless wireless links:Mobility capacity, distance channel impairments CDMA home, visited networks direct, indirect routing care-of-addressesIEEE 802.11 (“Wi-Fi”) CSMA/CA reflects wirelesschannel characteristics case studies mobile IP mobility in GSMcellular access architecture standards (e.g., GSM, 3G,4G LTE)principles: addressing,routing to mobile users impact on higher-layerprotocolsWireless, Mobile Networks 6-6834
Wireless, Mobile Networks 6-7 Characteristics of selected wireless links Indoor 10-30m Outdoor 50-200m Mid-range outdoor 200m – 4 Km Long-range outdoor 5Km – 20 Km .056 .384 1 802.15 4 5-11 802.11b 54 2G: IS-95, CDMA, GSM 2.5G: UMTS/WCDMA, CDMA2000 802.11a,g 3G: UMTS/WCDMA-HSPDA, CDMA20
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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 !
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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 .
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Wireless / Mobile Networks indigoo.com Contents 1. Wireless technologies overview 2. Radio technology 3. Radio technology problems 4. 802.11 WLAN Wireless LAN 5. Overview 1G / 2G / 2.5G / 2.75G / 3G / 4G networks 6. 2G / 2.5G / 3G networks 7. 4G LTE - Long Term Evolution 8. Satellite Internet Access 9. Wireless mobility 10. Mobile IP RFC2002
