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  • 1. 第 5 組 8717805 陳元凱 8717801 愛君逄 8817530 張哲航 8517011 鄭旭詠 8517019 鄭雅馨 June 19 2000 GSM 系統簡介及其發展趨勢 期末專題 Introduction to GPRS Mobility Management 1NCTU/CSIE/PCS Lab. 2000/6/19
  • 2. 2NCTU/CSIE/PCS Lab. 2000/6/19 OUTLINE  GPRS Brief  Mobility management  GPRS attach  Location management functions  Cell update  Routing area update  Combined RA/LA update  Conclusion & Discussion
  • 3. 3NCTU/CSIE/PCS Lab. 2000/6/19 GPRS Brief - Logical Architecture Gf D Gi Gn Gb Gc CE Gp Gs Signalling and Data Transfer Interface Signalling Interface MSC/VLR TE MT BSC TEPDN R Um Gr A HLR Other PLMN SGSN GGSN Gd SM-SC SMS-GMSC SMS-IWMSC GGSN EIR SGSN Gn CGF Ga Ga Billing System BTS Abis
  • 4. 4NCTU/CSIE/PCS Lab. 2000/6/19 GPRS Signalling Plane  Logical Link Control(LLC)  provides a highly reliable ciphered logical link  GPRS Mobility Management and Session Management(GMM/SM)  This protocol supports mobility management functionality such as GPRS attach, GPRS detach, security, routing area(RA) update, location update, PDP context activation, and PDP context deactivation.  MM contexts are established in the MS and SGSN  MM contexts -The mobility information that held at MS and SGSN BSSGP Relay GMM/SM LLC RLC MAC GSM RF GMM/SM LLC BSSGP L1bis Um Gb MS BSS SGSN Network Service RLC MAC GSM RF L1bis Network Service
  • 5. 5NCTU/CSIE/PCS Lab. 2000/6/19 GPRS MM Contexts  Partial information of SGSN MM contexts  Partial information of MS MM contexts IMSI IMSI is the main reference key. MM State Mobility management state, IDLE, STANDBY, or READY. P-TMSI Packet Temporary Mobile Subscriber Identity. P-TMSI Signature A signature used for identification checking purposes. IMEI International Mobile Equipment Identity MSISDN The basic MSISDN of the MS. Routeing Area Current routeing area. Cell Identity Current cell in READY state, last known cell in STANDBY or IDLE state. Cell Identity Age Time elapsed since the last LLC PDU was received from the MS at the SGSN. VLR Number The VLR number of the MSC/VLR currently serving this MS. New SGSN Address The IP address of the new SGSN where buffered and not sent N-PDUs should be forwarded to. Authentication Triplets Authentication and ciphering parameters. … … Each MM context contains zero or more of the following PDP contexts: Field SIM Description IMSI X International Mobile Subscriber Identity. MM State Mobility management state, IDLE, STANDBY, or READY. P-TMSI X Packet Temporary Mobile Subscriber Identity. P-TMSI Signature X A signature used for identification checking purposes. Routeing Area X Current routeing area. Cell Identity Current cell. Kc X Currently used ciphering key. CKSN X Ciphering key sequence number of Kc. Ciphering algorithm Selected ciphering algorithm. Classmark MS classmark. DRX Parameters Discontinuous reception parameters. … … Each MM context contains zero or more of the following PDP contexts: … …
  • 6. 6NCTU/CSIE/PCS Lab. 2000/6/19 GPRS MM: Basic Concepts  The definition of Routing Area(RA)  subset of GSM LA, 1 cell ≤ RA ≤ LA  MS updates its location when it changes the “big area” (RA update)  When MS is in STANDBY state (there is no call established) + save battery, less MS originated updates + UL radio resource is not wasted so much for MM messages - Paging load increase  MS updates its location to network in every cell range(Cell update)  MS is in READY state (a call is established) + MS’s location is always known in accuracy of cell - MS’s battery is draining due to frequently cell updates - UL radio resource is wasted with frequently cell updates
  • 7. 7NCTU/CSIE/PCS Lab. 2000/6/19 GPRS MM: Basic Concepts  GPRS Mobility Management(MM) Functionality  GPRS attach function – To know who is the MS and what it can or is allowed to do  GPRS detach function – Leave the system  Purge function – Allow an SGSN to inform HLR that is has deleted the MM and PDP contexts of a detached MS  Security function – Authentication of subscriber – User identity confidentiality – User data and GMM/SM signalling confidentiality (MS – SGSN) – Identity check procedures  Location Management function (Routing Area update & Location update) – to know the location of the MS ∗ Route the MT packets to the MS ∗ MO packet has no routing problem (MS -> SGSN, SGSN -> GGSN)  Subscriber management function
  • 8. 8NCTU/CSIE/PCS Lab. 2000/6/19  Non-anonymous access case  The MM state relates only to GPRS MM activities of a subscriber  The MM state is independent of the number and state of PDP contexts for that subscriber  The movement from one state to the next is dependent on the current state(IDEL, STANDY, or READY) and the event occurred(e.g., GPRS Attach)  Anonymous access case  The MM state relates to GPRS MM activities of an MS represented only by an Auxiliary TLLI  The AA MM state machine is independently handled by the MS and network, and may coexist with an IMSI-based MM state machine.  Several AA MM states machines may coexist in the same MS and SGSN simultaneously GPRS MM – Two Access Cases
  • 9. 9NCTU/CSIE/PCS Lab. 2000/6/19 GPRS Mobility Management States  IDLE State  GPRS MS is unreachable  MS may receive PTM-M message  MS shall perform GPRS Attach procedure to establish MM contexts in the MS and SGSN  STANDBY State  MS is attached to GPRS MM. MS and SGSN have established MM contexts.  MS can receive PTM-M and PTM-G data(i.e. can receive paging message)  PTP data reception and transmission, and PTM-G data transmission are not possible  MS execute MM procedure to inform SGSN when MS enter a new RA  MS does not inform SGSN when a change of cell in the same RA  READY state  MS can send and receive PDP PDU, and receive PTM-P and PTM-G data
  • 10. 10NCTU/CSIE/PCS Lab. 2000/6/19 Non-Anonymous Access MM States PDU transmission Implicit Detach or Cancel Location GPRS Attach GPRS Detach GPRS Attach PDU reception GPRS Detach or Cancel Location MM State Model of MS MM State Model of SGSN IDLE READY STANDBY IDLE READY STANDBY READYtimer expiry or Force to STANDBY or Abnormal RLC condition GPRS Detach (by MS or Network) READYtimer expiry or Force to STANDBY MS request access and logical link to SGSN is initiated MS sends an LLC PDU to the SGSN SGSN receive an LLC PDU from the MS
  • 11. 11NCTU/CSIE/PCS Lab. 2000/6/19 GPRS Attach and Detach Functions  Two types of attach function  GPRS attach  Combined GPRS/IMSI attach  Operations of Attach procedure  Inform the network for the MS’s request to be active  Network should check the MS’s identify  Download MS’s subscription information from HLR to SGSN  Update MSC/VLR, if IMSI Attach is also performed  Two types of detach function  MS-initiated Detach procedure  Network-Initiated Detach procedure – SGSN-initiated detach procedure – HLR-initiated detach procedure
  • 12. 12NCTU/CSIE/PCS Lab. 2000/6/19 Combined GPRS/IMSI Attach Procedure 7d. Cancel Location Ack 7c. Cancel Location 7b. Update Location 7g. Update Location Ack 7e. Insert Subscriber Data 7f. Insert Subscriber Data Ack 6d. Insert Subscriber Data 6c. Cancel Location Ack 6b. Cancel Location 3. Identity Response 2. Identification Response 2. Identification Request 1. Attach Request 5. IMEI Check 3. Identity Request 4. Authentication 6a. Update Location 7a. Location Update Request 7h. Location Update Accept 6f. Update Location Ack 6e. Insert Subscriber Data Ack MS BSS new SGSN old SGSN GGSN HLREIR old MSC/VLR new MSC/VLR 9. Attach Complete 8. Attach Accept 10. TMSI Reallocation Complete (P-TMSI, old RAI, Attach type, …) (IMSI)
  • 13. 13NCTU/CSIE/PCS Lab. 2000/6/19 Location Management  Location management functions  cell and PLMN selection  for network to know the RA for MSs in STANDBY and READY states  for network to know the cell identity for MSs in READY state  When to do  MS detect it has enter a new cell or a new RA  MS determine to perform periodic RA updates  Procedures  Cell update procedure  RA update procedures – Intra SGSN RA update procedure – Inter SGSN RA update procedure  Combined RA/LA update procedures – Combined intra SGSN RA/LA update procedure – Combined inter SGSN RA/LA update procedure  Periodic RA and LA update procedure
  • 14. 14NCTU/CSIE/PCS Lab. 2000/6/19 Location Management Procedures  Cell update procedure  When MS enters a new cell inside the current RA and MS is in READY state  If the RA has changed, a RA update is executed instead of a cell update  By sending an LLC frame containing P-TMSI to the SGSN  The SGSN records this MS’s change of cell  RA update procedures  When – A GPRS-attached MS detects that it has entered a new RA – When the periodic RA update timer has expired – A suspended MS is not resumed by the BSS  Intra SGSN RA update – Same SGSN, old RAI – E.g., periodic RA update  Inter SGSN RA update – New SGSN
  • 15. 15NCTU/CSIE/PCS Lab. 2000/6/19 Inter SGSN RA Update Procedure MS BSS new SGSN HLRGGSNold SGSN 2. SGSN Context Response 3. Security Functions 1. Routeing Area Update Request 2. SGSN Context Request 6. Update PDP Context Request 6. Update PDP Context Response 7. Update Location 10. Update Location Ack 11. Routeing Area Update Accept 8. Cancel Location 8. Cancel Location Ack 9. Insert Subscriber Data Ack 9. Insert Subscriber Data 12. Routeing Area Update Complete 5. Forward Packets 4. SGSN Context Acknowledge (old RAI, old P-TMSI signature, Update Type) 1. Old SGSN store New SGSN address 2. Start Timer and STOP the TX of N_PDU to MS Old SGSN duplicate the buffered N-PDUs and start tunnelling them to the new SGSN
  • 16. 16NCTU/CSIE/PCS Lab. 2000/6/19 Combined Inter SGSN RA/LA Update Procedure 12b. Cancel Location 12c. Cancel Location Ack 12d. Insert Subscriber Data 16. TMSI Reallocation Complete 12f. Update Location Ack 13. Location Update Accept 15. Routeing Area Update Complete 14. Routeing Area Update Accept 8. Cancel Location 8. Cancel Location Ack 6. Update PDP Context Response 6. Update PDP Context Request 7. Update Location 10. Update Location Ack 12a. Update Location 11. Location Update Request 2. SGSN Context Response 3. Security Functions 2. SGSN Context Request 1. Routeing Area Update Request 9. Insert Subscriber Data 9. Insert Subscriber Data Ack 12e. Insert Subscriber Data Ack MS BSS GGSNold SGSNnew SGSN HLR new MSC/VLR old MSC/VLR 5. Forward Packets 4. SGSN Context Acknowledge
  • 17. 17NCTU/CSIE/PCS Lab. 2000/6/19 Conclusions  User data transmission during attach, auth., RA update procedure may be lost and may therefore have to be retransmitted  GPRS HO - Mobile IP
  • 18. 18NCTU/CSIE/PCS Lab. 2000/6/19 References [1] GSM 02.60:”Digital cellular telecommunications system (Phase 2+); General Packet Radio Service (GPRS); Service description; Stage 1”, Nov. 1999 [2] GSM 03.60:”Digital cellular telecommunications system (Phase 2+); General Packet Radio Service (GPRS); Service description; Stage 2”, Nov. 1999 [3] GSM 03.64:”Digital cellular telecommunications system (Phase 2+); General Packet Radio Service (GPRS); Overall description of the GPRS radio interface; Stage 2”, Nov. 1999 [4] Hannu H. Kari, HUT/ITSE, the presentation of GPRS Mobility Management, Feb. 1999.

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