Arian Durresi1Wireless MobileWireless MobileTelephonyTelephonyArian DurresiArian DurresiThe Ohio State UniversityThe Ohio State UniversityColumbus, OH 43210Columbus, OH [email protected]@cis.ohio-state.edu http://www.cis.ohio-state.edu/~durresi/Arian Durresi2q Why wireless mobile telephony ?q First Generation, Analog technologiesq Second Generation, Digital :m D-AMPS, GSM, IS-95q Third Generation: IUT IMT-2000OverviewOverviewArian Durresi3Why Wireless MobileWhy Wireless MobileTelephony ?Telephony ?q Negroponte Switch : Personal mobile communicationon Ether.q Frequency Spectrum the most probably valuablenatural resourceq Progress in microelectronic - very smart mobileterminalsq Mobile phone the only technology with a growth ratehigher than Internet. By the year 2001 there will bemore than 500 million Internet users and 600 millionsmobile phone usersArian Durresi4Mobile PhoneMobile PhoneGenerationsGenerationsq First Generation: Analog, 70’-80’, Access FDMAm Advanced Mobile Phone System (AMPS) 800MHz, North Americam Total Access Communication System (TACS) 900MHz, Europem Nordic Mobile Telephone (NMT) 450 and 900MHz, Sweden, Norway, Denmark, Finland etc.m Good basic service, good territorial coverage.m Continue to operate profitably. Will survive forsome timeArian Durresi5Generations (Cont)Generations (Cont)q The need for second generation:m Capacity. The old systems were almost saturatedm More services, specially value addedm Analog system more vulnerable to physicalinfluences and disturbancesArian Durresi6Generations (Cont)Generations (Cont)q Second Generation. Digital Technologym Global System for Mobile Communication (GSM),Europe +, in 120 countries (US too) , 82 millionsubscriber, 33% of the world market.m Digital Advanced Mobile Phone System (D-AMPS): International Standard (IS-136), US +m Interim Standard 95 (IS-95): US, Asia, SouthAmerica.m Personal Digital Cellular (PDC): Japan, 27 millionsubscribersq Third Generation in developmentArian Durresi7Multiple Access SchemesMultiple Access SchemesFrequency FrequencyTimeTimeFrequencyTimech1 ch2 ch 3ch1ch2ch3ch1ch2ch3FDMA TDMA CDMAq Multiple access = Supporting more than onecommunication channel on a radio resourceq Big debate: Who will win TDMA or CDMA?Arian Durresi8TDMA TDMA vsvs. CDMA. CDMAq Spectrum Efficiency: Which multiple access schemehas better bps/Hz.cellq Flexibility: Which access scheme offers betterflexibility to handle multi-rate, -cell, -load, and -servicesq TDMA: Has some flexibility advantages, but has aspectrum efficiency disadvantageq CDMA: Less flexibility but has better spectrumefficiencyq Actual results depend on standards detailsArian Durresi9TDMATDMA vs vs. CDMA . CDMA contcont..q Answer unclearm IS-95 is probably superior to IS-54/136m IS-95 vs. GSM is unclearm IS-95 is clearly more complexq IS-54/136 is a grossly sub-optimum TDMA systemq GSM is a sub-optimum TDMA system (but prettygood)q IS-95 is a sub-optimum CDMA systemArian Durresi10Cellular SystemCellular SystemLarge cells for lowdensity traffic areasSmall cells for high densitytraffic areasq Cellular structure permits to reuse the frequencies and to distribute the resources depending on the trafficArian Durresi11Radio Resource ManagementRadio Resource Managementq Cell planning and management quasi online :m 1. Simulation of radio propagation using data fromsatellite about the territory, building, vegetation etc.m 2. Optimization of step 1: radio parameters, power.m 3. The dimensions of the cells and number ofchannels are calculated from the traffic foreseen inthat area.m 4. Frequency distribution among the cells, trying toreduce the interference.Arian Durresi12IS-136IS-136q Telecommunication Industry Association TIAstandard IS-136, November 1994q IS-136 or D-AMPS is a superset of IS-54, which is adevelopment of AMPS (analog)q AMPS: Advanced Mobile Phone Systemq Access scheme: TDMAq Frequencies 800MHz, 1.9GHz, Channel bandwidth300KHzq D-AMPS worldwide network with over 12 millionsubscribers, analog + digital 72 millionq Voice is digitized at 8kbpsArian Durresi13IS-136 IS-136 contcont..q It is possible to upgrade easily from an analog AMPSnetwork to a digital D-AMPS networkq Digital and analog AMPS channels can co-exist in thesame networkq A dual handset can operate in both analog and digitalAMPS, in both 800 and 1900 MHz.q Asynchronous data service, fax, Short MessageService, Sleep Mode capabilityq Allow hierarchical cell structures to be implementedq D-AMPS offers CDPD serviceArian Durresi14GSMGSMq Global System for Mobile Communicationq 1982 CEPT, 1989 ETSI, standard 8000 pagesq GSM 900 MHz, DCS 1800 MHz, DCS 1900 MHz inUS and Canadaq Access scheme: TDMA /FDMAq Services: Telephony - digitized voice 13kbs, dataservices up to 9.6bps soon 38.4kbps, group 3facsimile, Short Message Service (SMS), ISDN, X.25q International roaming: Subscribers can use the same phone terminal around the world and bill to home.This is a very attractive feature for the users.Arian Durresi15Architecture of the GSM networkArchitecture of the GSM networkMESIMBTSBTSBSCBSCMSCHLR VLREIR AuCPSTNUmAbisAq All the interfaces are standard - this permits a fierce competition among the vendors and a multi vendor networkArian Durresi16Elements of GSM ArchitectureElements of GSM Architectureq SIM: Subscriber Identity Module contains the International Mobile Subscriber Identity (IMSI) usedto identify the subscriber to the system, a secret keyfor authenticationq ME: Mobile Equipmentq BTS: Base Transceiver Station handles the radio-linkprotocols with the Mobile Station.q BSC: Base Station Controller handles radio-channelsetup, frequency hopping, and handoversq HLR: Home Location Register - all the administrativeinformation of each subscriber, and the currentlocation of the mobileArian Durresi17Architecture of the GSM networkArchitecture of the GSM networkq VLR: Visitor Location Register contains selectedinformation, for call control and services for mobiles located in its that geographic area.q MSC: Mobile services Switching Center - normalswitching node of the PSTN (Public SwitchedTelephone Network), plus functionality forregistration, authentication, location updating,handovers, and call routing to a roaming subscriber.q EIR: Equipment Identity Registerq AuC: Authentication Center stores a copy of the secretkey stored in each subscriber's SIM card, used forauthentication and encryptionArian Durresi18GSM Signaling ProtocolsGSM Signaling