WIRELESS NETWORKS AND MOBILE COMPUTING

1 DEPARTMENT OF INFORMATION TECHNOLOGYWIRELESS NETWORKS AND MOBILE COMPUTINGB Tech IV Year I Semester (JNTUH-R15)PreparedbyMr. E. Sunil ReddyAssistant Professor, ITINSTITUTE OF AERONAUTICAL ENGINEERING(Autonomous)Dundigal, Hyderabad -500 0431 UNIT I Introduction to network Technologies and Cellular Communications HIPERLAN: Protocol Architecture, Physical Layer, Channel-Access Control sub-layer, MAC sub layer, Information Bases and Networking WLAN: Infrared vs. Radio Transmission, Infrastructure and Ad Hoc NETWORKS , IEEE Bluetooth; User Scenarios, Physical Layer, MAC Layer, Networking, Security, Link Management. GSM: MOBILE Services, System Architecture, Radio Interfaces, Protocols, Localization, Calling, Handover, Security, New Data Services. MOBILE COMPUTING (MC): Introduction to MC, Novel Applications, Limitations and MOBILE Communication MOBILE COMPUTING Navel Applications Location dependent services Effects of device portability WIRELESS n/w s in comparison with fixed n/w s Limitations Architecture (simple reference model)Syllabus 3 Goal of MOBILE COMPUTING Peopleandtheirmachinesshouldbeabletoacce ssinformationandcommunicatewitheachother easilyandsecurely,inanymediumorcombinati onofmedia voice,data,image,video,ormultimedia anytime,anywhere,inatimely, COMPUTING Mobilecomputingreferstocomputinginadistr ibutedsysteminwhichsomeprocessesorproces sorscanmove.

2 Movingprocesses logicalmobility,realizedbyagents. Movingprocessors physicalmobility,realizedbymovingdevices . Mobilecomputingextendsadistributedcomput ingenvironmentwithanewdimensionofmobilit y. Mostexistingmobilecomputingsystemsarebas edonclient-servercomputingsystems. Recentmobilecomputingsolutionsconsiderge neraldistributedcomputing,namely,peer-to -peercomputingenvironments. system Definition: Adistributedsystemconsistsofacollectiono fautonomouscomputers,connectedthroughane tworkanddistributionmiddleware,whichenab lescomputerstocoordinatetheiractivitiesa ndtosharetheresourcesofthesystem,sothatu sersperceivethesystemasasingle,integrate dcomputingfacility. Multipleautonomouscomponents Componentsarenotsharedbyallusers Resourcesmaynotbeaccessible Softwarerunsinconcurrentprocessesondiffe rentprocessors6 Theprocessofcomputationonamobiledevice Inmobilecomputing,asetofdistributedcompu tingsystemsorserviceproviderserversparti cipate,connect,andsynchronizethroughmobi lecommunicationprotocols Mobilecomputingasagenerictermdescribinga bilitytousethetechnologytowirelesslyconn ecttoandusecentrallylocatedinformationan d/orapplicationsoftwarethroughtheapplica tionofsmall,portable,andwirelesscomputin gandcommunicationdevices7 Providesdecentralized(distributed)comput ationsondiversifieddevices,systems,andne tworks,whicharemobile,synchronized,andin terconnectedviamobilecommunicationstanda rdsandprotocols.

3 Mobiledevicedoesnotrestrictitselftojusto neapplication,suchas,voicecommunication Offersmobilitywithcomputingpower Facilitatesalargenumberofapplicationsona singledevice8 MOBILE Communication UserMobility: Referstoauserwhohasaccesstothesameorsimi lartelecommunicationservicesatdifferentp laces. usermobility:userscommunicate( WIRELESS ) anytime,anywhere,withanyone DevicePortability: Thecommunicationdevicemoveswithorwithout theuser deviceportability:devicescanbeconnecteda nytime,anywheretothenetwork Acommunicationdevicecantheexhibitoneofth efollowingcharacteristics: Issues Bandwidthrestrictionsandvariability Location-awarenetworkoperation Usermaywakeupinanewenvironment Dynamicreplicationofdata Queryingwirelessdata&location-basedrespo nses Bustynetworkactivityduringconnections&ha ndlingdisconnections Disconnection OSandFileSystemIssues-allowfordisconnect edoperation DatabaseSystemIssues-whendisconnected,ba sedonlocaldata10 Portability Issues Batterypowerrestrictions Riskstodata-Physicaldamage,loss,theft-Un authorizedaccess-encryptdatastoredonmobi les-Backupcriticaldatatofixed(reliable)h osts Smalluserinterface-Smalldisplaysduetobat terypowerandaspectratioconstraints-Canno topentoomanywindows-Difficulttoclickonmi niatureicons-Input-Graffiti,(Dictionary- based)

4 Expectation-Gestureorhandwritingrecognit ionwithStylusPenVoicematchingorvoicereco gnition11 Evolutions of the MOBILE Systems1G Analog systems2G systems voice communication Circuit systems Circuit switching for voice Packet switching for data3G systems Packet switching for voice and data High speed Compatible with different access systems Evolved Radio Interface IP based core network Compatible with different access technologies4G systems New Air Interface Very High bit rate services Convergence of Wireline, WIRELESS , and IP worldsEvolutions of the MOBILE Systems13 2G ( 2 0 0 0 ) E A R L Y 3 G ( 2 0 0 1 ) L A T E 3 G ( 2 0 0 3 ) 4G ( 2 0 0 5 ) A I R I N T E R F A C E V O I C E C I R C U I T C I R C U I T C I R C U I T D A T A C I R C U I T P A C K E T P A C K E T P A C K E T A C C E S S N E T W K V O I C E C I R C U I T C I R C U I T D A T A C I R C U I T C I R C U I T P A C K E T P A C K E T C O R E N E T W K VO I C E C I R C U I T D A T A O V E R L A Y P A C K E T P A C K E T P A C K E T P A C K E T Evolutions of the MOBILE Systems1415 Music,news,roadconditions,weatherreports ,andotherbroadcastinformationarereceived viadigitalaudiobroadcasting(DAB) ,auniversalmobiletelecommunicationssyste m(UMTS)phonemightbeavailableofferingvoic eanddataconnectivitywith384 (GPS).

5 Incaseofanaccident,notonlywilltheairbagb etriggered, ,trucks,andtrainsarealreadytransmittingm aintenanceandlogisticinformationtotheirh omebase,whichhelpstoimproveorganization( fleetmanagement), OF MOBILE COMPUTING16 ,onlydecentralized, :Managerscanusemobilecomputerssay, , sdatabase:toensurethatfilesonhisorherlap topreflectthecurrentsituation,toenableth ecompanytokeeptrackofallactivitiesofthei rtravellingemployees, Subscriber (Sept-2008)17 Limitations of the MOBILE Environment Limitations of the WIRELESS network heterogeneity of fragmented NETWORKS frequent disconnections limited communication bandwidth Interference: the quality of service (QoS) Bandwidth: connection latency Limitations Imposed by Mobility lack of mobility awareness by system/applications route breakages Dynamic changes in communication environment: variations in signal power within a region, thus link delays and connection losses Limitations of the MOBILE Computer short battery lifetime limited capacities18 Simple Reference Model19 Layer functionality20 Introduction to GSM GlobalSystemforMobile(GSM)isasecondgener ationcellularstandarddevelopedtocatervoi ceservicesanddatadeliveryusingdigitalmod ulation21 Developed by Group Sp ciale MOBILE (founded 1982) which was an initiative of CEPT ( Conference of European Post and Telecom ) Aim: to replace the incompatible analog system Presently the responsibility of GSM standardization resides with special MOBILE group under ETSI (European telecom Standards Institute ) GSM have 124 duplex channels, each 200 Khz wide, are used for FDMA.

6 GSM offer data rates of up to and up to a speed of 250Km/hr Under ETSI, GSM is named as Global System for MOBILE communication Today many providers all over the world use GSM (more than 190countries in Asia, Africa, Europe, Australia, America) More than 1300 million subscribers in world & 45 million subscriber in DevelopmentsGSM900 MobiletoBTS(uplink):890-915 MhzBTStoMobile(downlink):935-960 MhzGSM1800(DCS DigitalCellularSystem)MobiletoBTS(uplink ):1710-1785 MhzBTStoMobile(downlink)1805-1880 MhzGSM1900(PCS PersonalCommunicationService)MobiletoBTS (uplink):1850-1910 MhzBTStoMobile(downlink)1930-1990 Mhz23 GSM in WorldFigures: March, 200537%1%4%43%4%3%3%3% (INDIA)3%Arab WorldAsia PacificAfricaEast Central AsiaEuropeRussiaIndiaNorth AmericaSouth America24 GSM in IndiaFigures: March 2005 Bharti27%BSNL22%Spice 4%IDEA13%Hutch19%BPL6%Aircel4%Reliance3% MTNL2%BhartiBSNLH utchIDEABPLA ircelSpice RelianceMTNL25 MOBILE Services Tele-services BearerorDataServices Supplementaryservices26 Tele Services Telecommunication services that enable voice communicationvia MOBILE phones Offered services- MOBILE telephony-Emergency calling 27 Bearer Services Include various data services for information transfer between GSM and other NETWORKS like PSTN, ISDN etc at rates from 300 to 9600 bps Short Message Service (SMS) up to 160 character alphanumeric data transmission to/from the MOBILE terminal Unified Messaging Services(UMS) Group 3 fax Voice mailbox Electronic mail28 Supplementary ServicesCall related services.

7 Call Waiting-Notification of an incoming call while on the handset Call Hold-Put a caller on hold to take another call Call Barring-All calls, outgoing calls, or incoming calls Call Forwarding-Calls can be sent to various numbers defined by the user Multi Party Call Conferencing -Link multiple calls together CLIP Caller line identification presentation CLIR Caller line identification restriction CUG Closed user group29 GSM System ArchitectureBSCBSCMSCMSMSMSBTSBTSBTSGMSC PSTNISDNPDNEIRAUCHLRVLR3031 Components MobileStation(MS)MobileEquipment(ME)Subs criberIdentityModule(SIM) BaseStationSubsystem(BSS)BaseTransceiver station (BTS)BaseStationController(BSC) NetworkSwitchingSubsystem(NSS)MobileSwit chingCenter(MSC)HomeLocationRegister(HLR )VisitorLocationRegister(VLR)Authenticat ionCenter(AUC)EquipmentIdentityRegister( EIR)32 MOBILE station (MS)The MOBILE station is made up of two Equipment (ME) Identity Module (SIM)MobileEquipment Portable,vehiclemounted,handhelddevice UniquelyidentifiedbyanIMEI(International MobileEquipmentIdentity) Voiceanddatatransmission Monitoringpowerandsignalqualityofsurroun dingcellsforoptimumhandover 20W Identity Module (SIM) Smart card contains the International MOBILE Subscriber Identity (IMSI) Allows user to send and receive calls and receive other subscribed services Encoded network identification details-Key Ki, Kc and A3,A5 and A8 algorithms Protected by a password or PIN Can be moved from phone to phone contains key information to activate the phone34 base station Subsystem (BSS) Transceiver station (BTS) station Controller (BSC)1.

8 base Transceiver station (BTS): Encodes, encrypts, multiplexes, modulates and feeds the RF signals to the antenna. Frequency hopping Communicates with MOBILE station and BSC Consists of Transceivers (TRX) units35 Manages Radio resources for BTS Assigns Frequency and time slots for all MS s in its area Handles call set up Transcoding and rate adaptation functionality Handover for each MS Radio Power control It communicates with MSC and BTS2. base station Controller (BSC)36 network Switching Subsystem(NSS) MOBILE Switching Center (MSC) Heart of the network Manages communication between GSM and other NETWORKS Call setup function and basic switching Call routing Billing information and collection Mobility management-Registration-Location Updating-Inter BSS and inter MSC call handoff MSC does gateway function while its customer roams to other network by using Location Registers (HLR)-permanent database about MOBILE subscribers in a large service area(generally one per GSM network operator) -database contains IMSI, MSISDN, prepaid/postpaid, roaming restrictions, supplementary Location Registers (VLR)

9 -Temporary database which updates whenever new MS enters its area, by HLR database-Controls those mobiles roaming in its area -Reduces number of queries to HLR -Database contains IMSI, TMSI, MSISDN, MSRN, Location Area, authentication key38 Authentication Center (AUC)-Protects against intruders in air interface-Maintains authentication keys and algorithms and provides security triplets ( RAND, SRES,Kc)-Generally associated with HLRE quipment Identity Register (EIR)-Database that is used to track handsets using the IMEI (International MOBILE Equipment Identity)-Made up of three sub-classes: The White List, The Black List and the Gray List-Only one EIR per PLMN39 Radio Interface (Um) Air Interface: MS to BTS Uplink/Downlink of 25 MHz 890 -915 MHz for Up link 935 -960 MHz for Down link Combination of frequency division and time division multiplexing FDMA -124 channels of 200 kHz TDMA -Burst Modulation Method : GMSK (Gaussian Minimum Shift Keying ) @ Kbps40 FDMA/TDMA41 Physical Channel42 GSM-Frame Structure43 Logical ChannelsTCH (traffic)CCH(control) kbpsFCCH(Frequency correction)SCH(Synchronization)PCH(Pagin g)RACH(Random Access)AGCH(Access Grant)SDCCH(Stand Alone)SACCH(Slow-associated)FACCH(Fast-a ssociated)Half rate rate 44 BCCH BTStoMS sendcellidentities,organizationinfoabout commoncontrolchannels,cellserviceavailab le,etc Radiochannelconfiguration Currentcell+Neighbouringcells Synchronizinginformation Frequencies+framenumbering RegistrationIdentifiers LA+CellIdentification(CI)

10 +BaseStationIdentityCode45 BCCH Sub-Channels Frequency Correction Channel send a frequency correction data burst containing all zeros to effect a constant frequency shift of RF carrier MOBILE station knows which frequency to use Repeated broadcast of Frequency Bursts Synchronization Channel send TDMA frame number and base station identity code to synchronize MSs MS knows which timeslot to use Repeated broadcast of Synchronization Bursts46 CCC Access Grant Channel (AGCH) BTS to MS Used to assign an SDCCH/TCH to MS Paging Channel (PCH) BTS to MS Page MS Random Access Channel (RACH) MS => BTS Slotted Aloha Request for dedicated SDCCH47 DCCH bidirectional point-to-point --main signaling channels SDCCH (stand-alone dedicated control channel): for service request, subscriber authentication, equipment validation, assignment to a traffic channel SACCH (slow associated control channel): for out-of-band signaling associated with a traffic channel, eg, signal strength measurements FACCH (fast associated control channel): for preemptive signaling on a traffic channel, eg, for handoff messages Uses timeslots which are otherwise used by the TCH48 Localization and Calling Localization means same phone number is valid worldwide Periodic location updates VLR informs the HLR about MS location changes Ch