MM-3GPP 1 Mobile Communications Mobility Management in 3GPP Networks Mobility Management in 3GPP Networks Manuel P. Ricardo Faculdade de Engenharia da Universidade do Porto
MM-3GPP 2 ♦ How is the terminal mobility managed in GSM? ♦ How is the terminal mobility managed in GPRS? ♦ How is the terminal mobility managed in UMTS?
MM-3GPP 3 GSM GSM
MM-3GPP 4 4 types of handover 1 2 3 4 MS MS MS MS BTS BTS BTS BTS BTS BTS BTS BTS BSC BSC BSC MSC MSC 1 - between different sectors of the same cell 2 - between different cells within the same BSC domain 3 - between different BSC domains within the same MSC domain 4 - between different MSC domains
MM-3GPP 5 Handover decision receive level receive level BTS old BTS new handover margin HO_MARGIN MS MS BTS old BTS new
MM-3GPP 6 Mobile-Assisted Handover (MAHO) MS scans, measures and reports power received from several RF carrier based on BCCH information OLD NEW MS BTS BSC MSC BSC BTS measurement measurement report result HO decision HO decision HO required HO request resource allocation ch. activation ch. activation ack HO request ack HO command HO command HO command HO access link establishment HO complete HO complete clear command clear command clear complete clear complete
MM-3GPP 7 Location update ♦ MS is aware of location » BTS broadcasts Location Area Identification (LAI) on BCCH » SIM stores current LAI and TMSI ♦ Events which determine a current location update ♦ Events which determine a current location update » MS is switched on and current LAI equals the stored LAI » a timer set by the network expires and MS reports position TMSI may be updated and stored in SIM ♦ Events which determine a new location update » MS is switched on and current LAI differs from stored LAI » MS enters a new location area TMSI and LAI are updated and stored in SIM
MM-3GPP 8 Location update – new location NEW OLD MS MSC VLR HLR VLR old MSC old location update location update request request (old LAI/TMSI sent) request IMSI send IMSI send IMSI send IMSI update location update location request update update cancel location confirmed update confirmed request cancel location confirmed cancellation cancellation confirmed confirmed
MM-3GPP 9 Location update Channel activity at radio interface BTS MS BCCH System parameters and other overhead idle updated RACH Channel request successful access AGCH Assign stand alone dedicated control channel SDCCH SDCCH Location updating request Location updating request old LAI/TMSI sent old LAI/TMSI sent SDCCH Authentication request calculate SRES / K c send RAND calculate SRES / K c SDCCH Authentication response send SRES SRES confirmed SDCCH Request to transmit in cipher mode switch to cipher mode SDCCH Acknowledge cipher mode request SDCCH Location update confirmed store LAI/TMSI in SIM new TMSI sent (optional) SDCCH Acknowledge new location SDCCH Release stand alone dedicated control channel idle updated
MM-3GPP 10 GPRS, 2G (3GPP TS 23.060) (3GPP TS 23.060)
MM-3GPP 11 Terminal Mobility Management ♦ Packet forwarding in downlink � demands knowledge of terminal location » If terminal informs frequently the network about its location network is aware of the terminal’s cell � fast packet forwarding, but high consumption of batery and radio resources » If terminal does not inform frequently the network about its location network needs to “page” the terminal before each packet transmission � slow forwarding ♦ Solution - divided the space in more areas than in GSM » Routeing Areas (RA), in GPRS – 1 Location Area (LA) of GSM � n Routeing Areas (RA) – 1 RA � n cells
MM-3GPP 12 Terminal Mobility Management - updating states • Frequency of actualization in terminal 3 states • IDLE Terminal does not inform SGSN about its position • READY • READY Terminal informs SGSN when it enters a new cell élula • Precise location • No paging required • STANDBY Terminal inform SGSN when it enters in a new RA • Cell changes are not communicated • Packet transmission in downlink � paging of the cells of the RA
MM-3GPP 13 Mobility Management ♦ Micro Mobility – Terminal moves between cells under control of the same SGSN 1 SGSN � n RAs; 1 RA � n cells – Mobility is managed by the SGSN – New terminal position is not communicated to other network elements (GGSN, HLR) – New terminal position is not communicated to other network elements (GGSN, HLR) ♦ Macro Mobility – Terminal moves between cells under control of different SGSNs – New SGSN requests PDP Contexts (session descriptors) to old SGSN – New SGSN requests GGSN to update the forwarding tables (L2 tunnels) – SGSN updates HLR
MM-3GPP 14 Micromobility - Routing Area Actualization (Intra SGSN) MS BSS SGSN 1. Routeing Area Update Request 2. Security Functions 3. Routeing Area Update Accept C1 C1 4. Routeing Area Update Complete 1. Routeing Area Update Request (P-TMSI, old RAI, P-TMSI Signature, Update Type) Update Type indicates RA update or periodic RA update. 2. Security functions may be executed 3. The SGSN validates the MS's presence in the new RA. If all checks are successful, the SGSN can reallocate a new P-TMSI. A Routeing Area Update Accept (P-TMSI, P-TMSI Signature) is returned to the MS 4. If P-TMSI was reallocated, the MS acknowledges the new P-TMSI by returning a Routeing Area Update Complete message to the SGSN.
MM-3GPP 15 RA Actualization (Inter SGSN) MS BSS new SGSN old SGSN GGSN HLR 1. Routeing Area Update Request 2. SGSN Context Request 2. SGSN Context Response 3. Security Functions S G 4. SGSN Context Acknowledge S M C1 5. Forward Packets S M G 6. Update PDP Context Request S 6. Update PDP Context Response 7. Update Location S – SGSN, G – GGSN, M - MS 8. Cancel Location 8. Cancel Location Ack 9. Insert Subscriber Data S M G 9. Insert Subscriber Data Ack S 10. Update Location Ack C2 S M 11. Routeing Area Update Accept G S C3 12. Routeing Area Update Complete
MM-3GPP 16 UMTS, 3G, Packet Domain (3GPP TS 23.060) (3GPP TS 23.060)
MM-3GPP 17 Macrodiversity and Handover » Softer handover � between 2 sectors of same cell » Soft handover � between 2 cells of same RNC » Hard handover � between different systems Soft Handover
MM-3GPP 18 Softer Handover – between 2 sectors of same cell • Internal to Node B • No extra transmissions in networks networks • Rake receiver • Additional diversity gain
MM-3GPP 19 Soft Handover – between 2 cells of same RNC
MM-3GPP 20 UMTS, Handover, Interface Iur ♦ Handover – uses Interface Iur; between RNC UMTS GSM UMSC UMSC UMSC MSC MSC Iur Iur Iur BSC BSC BSC BSC RNC RNC RNC RNC RNC RNC
MM-3GPP 21 Mobility Management – 3G, Iu mode (UMTS) PM M - PM M - D ETAC H ED D ETAC H ED D etach, D etach, PS D etach PS D etach PS Attach R eject, PS Attach R eject, PS Attach PS Attach RAU R eject RAU R eject PS Signalling PS S ignalling PM M - C onnection R elease C onnection R elease PM M - PM M -ID LE PM M -ID LE C ONNECTED C ONNE CTED SM-ACTIVE or SM-ACTIVE or SM-ACTIVE or SM -ACTIV E or PS S ignalling PS Signalling INACTIVE INACTIVE INACTIVE INA CTIVE C onnection Establish C onnection Establish S erving RNC relocation MS MM States 3G -SG SN MM States
MM-3GPP 22 Mobility Management States ♦ PMM-DETACHED state » no communication between the MS and 3G-SGSN » MS location un-known » If MS performs the GPRS Attach procedure � MM contexts in the MS and the SGSN ♦ PMM-IDLE state » The MS location known; accuracy of a Routeing Area » Paging needed » MS performs Routeing Area update if RA changes ♦ PMM-CONNECTED state » MS location known with an accuracy of a serving RNC » MS location tracked by serving RNC
MM-3GPP 23 Location Management Function, in 3G ♦ In 2G, MS tracked in 2 levels: cell, RA ♦ In 3G, MS tracked in 3 levels: cell, RAN-area, RA RAN – Radio Access Network RA – Routeing Area ♦ Mechanisms required for – network to know about the Routeing Area of MS – RAN to know about the RAN-area or cell of MS
new old new old MM-3GPP 24 new old MSC/VLR MSC/VLR MS GGSN HLR 3G-SGSN 3G-SGSN SRNS SRNS 1. Routeing Area Update Request 2. SGSN Context Request 2a. SRNS Context Request 2a. SRNS Context Response RA Update 3. SGSN Context Response 4. Security Functions 5. SGSN Context Ack C1 3 6. SRNS Data Forward Command 7. Forward Packets 8. Forward Packets 9. Update PDP Context Request 9. Update PDP Context Response 10. Update Location 11. Cancel Location 11a. Iu Release Command 11a. Iu Release Complete 11. Cancel Location Ack 12. Insert Subscriber Data 12. Insert Subscriber Data Ack 13. Update Location Ack 14. Location Update Request 15a. Update Location 15b. Cancel Location 15c. Cancel Location Ack 15d. Insert Subscriber Data 15e. Insert Subscriber Data Ack 15f. Update Location Ack 16. Location Update Accept C2 17. Routeing Area Update Accept C3 18. Routeing Area Update Complete 19. TMSI Reallocation Complete
MM-3GPP 25 Serving RNS Relocation Procedures ♦ Supports movement from serving-RNS to target-RNC ♦ Lossless Relocation ♦ MS and RNS have to support lossless PDCP » s-RNS forwards GTP-PDUs to t-RNS (received-but-not-yet-transferred)
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