1. GSM ARCHITECTURE, GSMNETWORK IDENTITIES, NETWORKCASES, CELL PLANNING, ANDCOMPOUND CHARGINGPrepared by:Zorays Khalid (Internee)

2. ERICSSONS GSM SYSTEMARCHITECTURE Cellular Matara Ericsson 20 (GSM 900 andGSM 1800) Cellular Mobile System 40 (GSM 1900) TableSystem P-GSM E-GSM GSM 1800 GSM 1900BW 25 MHz 35 MHz 75 MHz 60 MHZRadio125 175 375 300ChannelsWavelength~33 cm ~33cm ~17cm ~16 cm 3. CAPACITY AND FREQUENCY RE-USE Limited frequencies Capacity: Number of frequencies in the cell Interference is avoided by allocatingdifferent frequencies in adjacent cells andreallocating these frequencies in ahoneycomb pattern The lower frequency re-use distance, themore capacity is available. 4. GSM TRANSMISSION PROCESS1.ADC2.Segmentation3.Speech Coding4.Channel Coding5. Interleaving6.Ciphering/Encryption7.Burst Formatting 5. LOGICAL CHANNELS Each time slot on the TDMA frame is aphysical channel. 8 physical channels per carrier. Control Channels1.Broadcast (connects)2.Common (request access)3.Dedicated (set-up) Traffic Channels 6. AXE STRUCTURE Non- Application Modularity based AXE 105e.g. BSC node Application Modularity based AXE 106(discussed) 7. SWITCHING SYSTEM Mobile services Switching Center/ VisitorLocation Register Gateway Mobile services Switching Center Home Location Register Interworking Location Register* Authentication Center and EquipmentIdentity Register 8. MSC Switching and call routing Charging and Service provisioning Communication with HLR Communication with VLR Communication with MSC Control of connected BSCs Direct Access to Internet Services 9. VLR Temporary storage location for MobileSubscription within particular MSC servicearea. On entering new MSC service area, It1. Checks data base that MS is listed or not usingIMSI2. If not listed, it requests HLR to send a copy of MSsubscription3. HLR does so and updates itself and instructs oldVLR to delete it.4. VLR stores this information. 10. GMSC It enables MSC to interrogate HLR in orderto route a mobile terminating call*. Find and interrogate HLR for roamingnumber. Routes the call according to theinterrogation. 11. HLR It is a permanent store for persons subscriptioninformation e.g. IMSI, MSISDN, subscribersupplementary services, subscriber location information(i.e. MSC service area), subscriber authenticationinformation. Subscription database management Communication with the MSCs Communication with GMSCs Communication with AUCs Communication with VLRs/ILRs 12. CALL SETUP Marking the MS as active in the VLR The authentication procedure Start Ciphering Equipment Identification Sending the B-subscribers number to thenetwork Checking if the subscriber has the serviceBarring of outgoing calls activated 13. MOBILE INTELLIGENT NETWORK Ericssons MIN nodes are SSF: SSP acts as an interface between the callcontrol functions of the mobile network and theservice control functions of a Service Controlpoint. SCF: SCP contains the intelligence of the MINservices. SDP Manages data which is used by MIN. 14. GSM NETWORK IDENTITIES These are the unique numbers used to locatea mobile subscriber e.g., E.164 numberingplan is used in PSTN/ISDN network Three main types of GSM Network Identities1.Subscriber Related Identities2.Equipment Related Identities3.Location Related Identities 15. SUBSCRIBER RELATED IDENTITIES MSISDN IMSI TMSI 16. TMSIMSC/VLR allocateTMSI to IMSI (SIM) attime of registration.It helps protectsubscriber identitySignificant withMSC/VLRIt is changed onlocation update8 digitsSubscriber Identityconfidentiality isenforced whensubscriber is usingPLMN preventstracing of the mobileIMSIFor identification overradio path andthrough the network.Network relatedsubscriber info. for allsignaling in a PLMN.Ki, A3, A8VLR,SIM,HLRMCC+MNC+MSINMSISDN0313 5171 327CME 20CC+NDC (PLMNcodes) +SN = 15dig. MaxCMS 40NDC -> NPA 17. EQUIPMENT RELATED IDENTITIES IMEI IMEISV 18. IMEISVSoftware versionhelps determineservices of MSand speechcodingcapabilitiesIMEI356384 00 6106486TAC + FAC + SNR + sparebitUniquely identifiesMS equipment tonetworkFor securityproceduresstolen/unauthorized access to thenetworkEIR functions 19. LOCATION RELATED IDENTITIES MSRN LAI CGI BSIC LN RSZI 20. MSRN It is assignedduringestablishment of acall to a roamingsubscriber CC + NDC + SN*LAI Required for routing Paging: MSC knowscurrent LA of MS Location updating MCC + MNC + LAC*CGI For Identifyingindividual cellswithin a LocationArea 65536 X 65536 = 4.3billion max. no. ofcell identities in oneoperators network 21. BSIC To distinguishb/w differentbase stationsending onsamefrequency NCC* + BCC*LN Geographical Forlocal/regionalsubscription CC + NDC +LSP*RSZI For regionalsubscription CC + NDC +ZC 22. TRAFFIC CASES MS in Idle mode MS in Active mode1.Mobile Originated2.Mobile Terminated 23. ATTACHING TO THE NETWORKA. IMSI attachOn switching MS1. It scans all RF channels tuning to the strongestcarrier and checks If it is a BCCH and triesotherwise 2nd strongest carrier to lock with.2. If BCCH belongs to other network onlyEmergency calls allowed3.List stored in a memory to directly find specificcarriers 24. ATTACHING TO THE NETWORKMS sends IMSI attach message signifyingthat it turned from detached to idle.VLR determines if subscriber already presentIf not, it asks for a copy of subscriber infofrom HLRVLR updates MS to idleMS is informed in an acknowledgementmessage 25. ATTACHING TO THE NETWORK(CONT.)B. Location Updating, type IMSI attachIn case Location Area has changed while MSwas detachedVLR is updated of this new location duringIMSI attach 26. ROAMING IN THE NETWORKA. Changing cell within a Location AreaNo update b/c MS knows that the new cellbelongs to the same Location Area by listeningto BCCHB. Location Updating, same MSC/VLR areaIn case MS detects a change in LAI bylistening to BCCH* and comparing with the onestored on the SIM. It requests the network forupdate via Location Updating Message 27. ROAMING IN THE NETWORK (CONT.)MS connects via SDCCH and authenticationis performedMSC/VLR authenticates that MS belongs tothe network or not and requests the RBS andMS to release the signaling channelaccordingly 28. ROAMING IN THE NETWORK (CONT.)C. Location Update, New MSC/VLRNow if MSC/VLR do not find the MSregisteredHLR is requested to provide a copy of MSsubscriptionNew VLR is informed of location and status,meanwhile HLR updates itselfOld VLR is told to remove MS subscriptionVLR acknowledges to MS 29. ROAMING IN THE NETWORK (CONT.)D. Location Updating, type PeriodicBCCH lets know the refreshing rateIf MS misses such a registration, networkmarks it detached preventing needlesspagingMS tries to register until it getsacknowledgement 30. DETACHING FROM THE NETWORKA. IMSI detachOn Switching off, VLR marks thecorresponding IMSI detachHLR not informed, no acknowledgement sentto MSB. Implicit detachIn case of periodic registration failure 31. TRAFFIC CASES: CALL FROM AN MSMS uses RACH to ask for Signaling channelBTS assigns a signaling channel(SDCCH) using AGCHMS sends a call set-uprequest to MSC/VLR viaSDCCH*MSC/VLR forwards B-number to anexchange in the PSTN. If answered,connection is established.The MSC/VLR instructsthe BTS to allocate an idleTCH. The RBS and MStunes to the TCH 32. CALL SET-UP1. MSC/VLR knows that the MS is in which LA, it sends apaging message to the BSC.2. The BSC distributes the paging message to different BTS inthe desired Location Area using PCH.3. When MS detects its MSIN it sends a request for signalingchannel using RACH4. The BSC uses AGCH to inform MS about SDCCH andSACCH5. SDCCH and SACCH are used for call set-up. A TCH isallocated and SDCCH is released.6. The MS and BTS switches to the TCH frequency and timeslot. During call, SACCH is used to keep call status.7. FACCH checks for handover*. 33. CALL TO AN MS The exact location of the MS called isunknown Paging is done MSISDN is analyzed in PSTN (a call toMS) GMSC finds out which HLR does itbelong to. Checks if C-number call forwarding isactivated HLR requests MSRN fromMSC/VLR..sent to GMSC 34. CALL TO AN MS GMSC analyzes MSRN and routes the call tothe MSC/VLR MSC/VLR knows about LA the MS is situatedin and a paging message is sent BSC uses PCH to page IMSI or TMSI* The rest is the same. 35. CELLS Cell planning: Site, equipment and itsconfiguration A cell may be defined as an area of radiocoverage from one BTS*/hexagon(graphically). Two main Types:1. Omni directional Cell (360degrees/coverage)2. Sector Cell (in a given direction only e.g.120 or 180 degrees/ capacity) 36. CELL PLANNING PROCESSStart (go C.W.)Traffic andCoverageAnalysisNominal CellPlanSurveysSystem DesignImplementation 37. OVERLAID/UNDERLAID SUBCELLS A way to increase traffic capacity withoutbuilding new sites Overlaid at lower power level (smallercoverage area) Underlaid at a bit higher power level (largercoverage area comparatively) and thus twodifferent frequency re-use patterns. 38. CHARGED CALLS CS1+ Ericssons IN protocol supporting allcapabilities of Ericsson INAP 2.1 and ETSICore INAP CS1 Applies to Originating, Terminating, andForwarded Calls in the HPLMN andTerminating Calls in the VPLMN 39. ORIGINATING CHARGED CALL I am a Charging System Subscriber* I initiate a call My Originating IN Category Key in the VLR routes the call to SSF SSF collects call data and triggers CCN CCN selects SDP and sends call data (MNP/LBC are performedoptionally) SDP reserves money from the account and sends the calculated time toCCN + announc. CCN tells SSF to play announcements if requested CCN directs SSF to setup the call and monitors it based on calculated calltime. Call lasts longer than the time sent to SSF .. CCN is notified CCN requests another reservation from SDP 40. ORIGINATING CALL SDP makes new charging analysis and deducts the amount previouslyreserved from the account* SDP reserves money for next period and forwards a new call time to CCN CCN passes the new call time on to SSF If my account balance reaches account empty limit In case the call lasts longer, a notification is sent to CCN CCN requests SDP to reserve another amount SDP makes a new charging analysis and updates the account Since no enough funds the SDP calculates call time to CCN together withan indication A call cutoff warning announcement is played after a fixed time This time between call cutoff warning and call cutoff is excluded from newcall time and passed on to SSF 41. ORIGINATING CALL SSF notifies CCN that the time sent has expired CCN send remaining 30 seconds to SSF SSF tells CCN that these 30 seconds have expired CCN tells SSF to play call cutoff announcement and to disconnect SSF notifies CCN about call disconnect CCN sends a final report to SDP where final charging is done SDP also rates the total call and sends the report to CCN CCN tells a call release to SSF. 42. SMS IN TRIGGERED CHARGING An SMS is sent based on OICK and the destination address routes it tothe SSF The SSF collects data about the call and triggers CCN to check theaccount The data collected in step 2, is sent in a first interrogation to where theservice data scenario of the account is checked and a a preliminarycharging analysis takes place No reservation of money is performed in this step SDP sends the result of the interrogation to CCN CCN sends a successful result to the SSF The MSC delivers the SMS to the SMS-C The delivery of the SMS is confirmed by the SMS-C The MSC/SSF triggers CCN to deduct the fee of the SMS CCN sends a first interrogation to SDP where the service scenario of theaccount is checked 43. SMS IN CS+1 And a preliminary charging analysis takes place SDP reserves money from the account and sends a successful resulttogether with other call data to CCN CCN sends a final report to the SDP SDP rates the total cost, deducts money from the account and sends afinal report result to CCN CCN sends a release operation with a successful deduct code to theMSC/SSF 44. VOUCHER REFILL THROUGH IVR A refill call is initiated by me The call is routed to Interactive Voice Response. The IVR check if thecalling party no. is complete The IVR requests account information from AIR (Account Information andRefill System) AIR interrogates Account Finder (AF) to get the SDP IP address AF returns the SDP IP address AIR uses the SDP IP address to request account and subscriber datainformation from SDP SDP checks if any account updates are necessary and sends the result ofaccount information request back to AIR AIR sends the requested information to IVR e.g. preferred language 45. VOUCHER REFILL THROUGH IVR The IVR plays a standard welcome announcement and a menuannouncement/. The subscriber selects the menu option voucher refill andenters the voucher activation number The entered activation code and the mobile number of the subscriber issent to AIR for verification AOR requests account information from SDP SDP sends the result of account information request back to AIR. AIRverifies that the subscriber exists and is not barred from refill AIR sends the entered voucher activation code to the Voucher Server(VS) for verification When the VS has verified the voucher activation code and has reservedthe voucher, it returns a response to AIR 46. VOUCHER REFILL THROUGH IVR AIR receives a response from the VS indicating if the verification wassuccessful or not. It was successful, so AIR sends a refill request to SDP The account balance increased in SDP database for account CDR processing is used and has caused an SMS/GPRS barring.Unbarring of SMS and GPRS in the HLR is supported when a certainaccount threshold has been reached. In this case through a refill SDP sends the result of the refill back to AIR The refill was successful so AIR requests the VS to set the voucher inused state The VS responds with the result back to AIR AIR sends a response to the IVR including the account balance and anindication if the refill was successful or not 47. VOUCHER REFILL THROUGH IVR A CDR including the refill data is generated The IVR uses the voice prompt to notify the subscriber of the result The subscriber releases the call 48. USSD BALANCE ENQUIRY I originate a USSD message with the USSD service code corresponding toenquiry The MSC forwards the message to the HLR The HLR analyses the USSD service code and forwards the message to AIR AIR interrogates AF to get the SDP IP address AF returns the SDP IP address AIR uses the returned SDP IP address to request account and subscriber datainformation from SDP SDP sends the requested account information to AIR AIR reformats the response into a USSD text string and send to the HLR. Theresponse is successful, so the appropriate successful message is sent,otherwise a failure response with the reason for failure would have been sent The HLR forwards the response to the MSC and the response is displayed onthe subscribers handset