Gsm call routing

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This will give some information about how a GSM call flow works.

This will give some information about how a GSM call flow works.

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  • The following is intended to help illustrate the four types (levels) of handover. Illustrated is a system consisting of two Mobile Switching Centres (MSCs) with three Base Station Systems (BSSs). Also depicted are cell coverage areas with example global cell identification codes for each base transceiver station. From the mobile station's reference point, it is unaware of the four levels of handover. The mobile station has two handover-related responsibilities: to provide signal measurements to its serving base station and to retune to a new radio channel when ordered to do so. Assume that the mobile and land stations are active in a call, the call is being controlled by MSC A, and the mobile is currently in cell area 234-01-100-54 . Intra-BSS/Intra Base Transceiver Station For this type of handover, the mobile station is handed off to a different radio channel within the same cell area: 234-01-100-54 . This is actually an unusual type of handover, since it is not triggered by poor signal strength – if it was, the candidate base station would be different from the serving BTS. A probable cause of this type of handover would be poor signal quality (not strength), possibly due to co-channel interference. For this type of handover, BSC 3 would allocate a new radio channel and instruct the mobile station to retune.

Transcript

  • 1. GSM Call Routing RK
  • 2. AgendaGSM-Introduction Mobile Station (ME+SIM) HLR, VLRLocation UpdateCall Routing Scenarios Mobile Originated Sequence Mobile Terminated Sequence Mobile-to-Mobile Long distance Mobile in Roaming (Domestic, International)Call HandoverQuestions
  • 3. Mobile Station(MS)
  • 4. HLR / VLR Home Location Registers (HLR) o permanent database about mobile subscribers in a large service area(generally one per GSM network operator) o database contains IMSI, MSISDN, prepaid/postpaid, roaming restrictions, MSC/VLR, supplementary services. Visitor Location Registers (VLR) o Temporary database which updates whenever new MS enters its area, by HLR database o Controls those mobiles roaming in its area o Reduces number of queries to HLR o Database contains IMSI, TMSI, MSISDN, MSRN, Location Area, authentication key
  • 5. GSM Architecture EIR AuC
  • 6. Brief Introdution to Location Update Three types of Location Update : IMSI Attach/ Detach Normal Location Update Periodic Location Update
  • 7. QuestionsPlease give the sequence:1.The called MS is powered off.2.The called MS activates the CFU to aPSTN No.3.The called MS has been barred allincoming call.4.The Called MS are not known at HLR
  • 8. 1. The called MS is powered off AP Vodafone AP Airtel MS BSS MSC VLR HLR GMSC GMSC Initial and Final MSISDN 1 Address Message ( +91 9885 xxxxxx MSISDN 2 Send Routing Info ( +91 9885 xxxxxx 3 Routing Info Ack Subscriber Absent The Calling Mobile hears the announcement of mobile is powered off
  • 9. 2. The called MS activates the CFU to a PSTN No. MS BSS MSC VLR HLR GMSC PSTN MSISDN Initial and Final +91 9885 xxxxxx 1 Address Message MSISDN 2 Send Routing Info +91 9885 xxxxxx 3 Routing Info Ack CFN +91 40 662353074 IFAM
  • 10. 3. The called MS has been barred all incoming call. MS BSS MSC VLR HLR GMSC GMSC Initial and Final MSISDN 1 Address Message +91 9885 xxxxxx MSISDN 2 Send Routing Info +91 9885 xxxxxx 3 Routing Info Ack Call Barred
  • 11. 4. The Called MS are not known at HLR MS BSS MSC VLR HLR GMSC GMSC Initial and Final MSISDN 1 Address Message +91 9885 xxxxxx MSISDN 2 Send Routing Info +91 9885 xxxxxx 3 Routing Info Ack Unknown Subscriber
  • 12. GSM Architecture Cntd…
  • 13. Call Routing Scenarios
  • 14. Mobile Originated Sequence MS BSS MSC VLR HLR PSTN1 CHANNEL REQUEST Signaling Link request DCCH ASSIGN Signaling Link Granted SIGNALING LINK ESTABLISHED Channel request 2 REQ. FOR SERVICE 3 AUTHENTICATION SET Cipher MODE Setup Voice Call 4 SET-UP Dailed digits …+91 40 66235307 5 EQUIP. ID REQ. 6 COMPLETE CALL CALL PROCEEDING Call setup is in Process
  • 15. Mobile Originated Sequence MS BSS MSC VLR HLR PSTN 7 ASSIG. COMMAND Switch from Signaling ASSIG. COMPLETE Mode to Voice +91 40 66235307 8.Initial and Final Address Switch routes the call to PSTN Message (IFAM) PSTN indicates to Switch Address Complete(ACM) < Called Subscriber Informed Via Ring Alerting Ring Alert MS hears ring tone from land Passed to Mobile phone Called Subscriber Answered 9 Answer (ANS)Connect Switch Informs Ring tone Call Answered stops10 Connect Acknowldge Acknowledge Call Hi RK Answered received Speech Started BILLING STARTS
  • 16. Mobile Terminated Sequence AP Vodafone AP Airtel MS BSS MSC VLR HLR GMSC GMSC Initial and Final MSISDN1 Address Message +91 9885 xxxxxx MSISDN IMSI +91 9885 xxxxxx2 Send Routing Info 404 13 xxxxxxxxxx 3 Routing Info Ack Initial and Final MSRN MSRN Address Message 091 9885 xxxxxx (roaming number) MSRN 091 9885 xxxxxx (roaming number) 4 Send Info For I/C Call Setup MSRN 5 Page <PCH> Paging Request TMSI) TMSI) LAI & TMSI) LAI – 404 13 location Area Code
  • 17. Mobile Terminated Sequence AP Vodafone AP Airtel MS BSS MSC VLR HLR GMSC GMSC 6 Assignment Call Setup Request Command Assignment Call Setup Confirmed Complete Ring Tone at Ringtone Alert Acknowledge the Other Alert MobileAddress Complete 7 Connect Mobile Subscriber Answered Ringing stops Subscriber at Other picks up MobileConnect ACK ANS Billing starts Speech Started Hello...
  • 18. Mobile-to-Mobile Long Distance 2. Towers are serviced by 1. Cell phone transmits to a local base station local towers Radio tower 3. Basestations are services by Mobil Switching Station Radio tower Base Station Mobile Switching Station 5. Destination switch office 4. Regional Switch Office receives call, and forwards forwards calls to Mobil Switching Station Trunk Regional Switch Office Regional Switch Office Radio tower Mobile Switching Station Base Station 5. Mobile SwitchingStation forwards to Base 6. Base Station forwards Station to local towers. Radio tower 7. Local towers complete the loop
  • 19. Mobile is in Roaming 2.Receiving Mobile on Roaming3. Both Mobiles are on Roaming
  • 20. International Roamer terminated call
  • 21. Handover MSC B MSC ALocation Area-089 Location Area-100 20 50 53 49 089 100 100 404 404 49 40 4 49 BSC1 089 21 BSC2 100 51 BSC3 54 49 100 404 49 404 49 404 089 22 100 52 0 55 9 10 404 49 404 49 404 4 Global Cell Identification Country Network Location Cell INDIA-AP-Airtel Code Code Area Identity MCC-MNC 404 49 Code 404 -49(INA49)
  • 22. Questions ?