Politecnico di Milano Facoltà di Ingegneria dell Informazione. MRN 6 GSM part 2. Mobile Radio Networks Prof. Antonio Capone

Transcription

1 Politecnico di Milano Facoltà di Ingegneria dell Informazione MRN 6 GSM part 2 Mobile Radio Networks Prof. Antonio Capone

2 Signaling A. Capone: Mobile Radio Network 2

3 Telephone signaling o In classic telephone service, signaling is in charge of routing and setting up circuits for the service o In IP telephony, signaling is used for setting up media sessions o The basic service provided by signaling is the: Basic call o There are two main components of signaling: n User signaling: for the communication between user terminals and the network n Network signaling: for the communication among network elements A. Capone: Mobile Radio Network 3

4 Signaling o User signaling n It allows user: o To ask for a specific service o To indicate the called party n And the network to provide information to user on the call status o Network available o Call in progress o Destination reached o etc. Telephone Network A. Capone: Mobile Radio Network 4

5 Signaling o Network signaling n It allows the exchange of information among switching stations for o Routing calls along available paths in the network n It is also used for providing supplementary services in addition to the basis one like: o Special numbers (800, 900, etc.) o Calling party notification o Mobility management o Call deviation o Etc. A. Capone: Mobile Radio Network 5

6 User signaling o The interface between user and network can be analogic or digital (ISDN) o The type of user signaling depends on the interface o In case of analog interface the signaling is also analogic A. Capone: Mobile Radio Network 6

7 User signaling: analog interface user telephone network destination Phone pick up Line in use signal Busy tone sound Busy tone Number selection Echo of number tones Multi-frequency tones Ringing tone Ringing signal Ringing current Hello? Hi, this is Antonio Hello? Hi, this is Antonio Hello? Hi, this is Antonio A. Capone: Mobile Radio Network 7

8 User signaling: ISDN o The case of digital interface is rather different o In this case all signaling is based on digital messages transmitted on layer 2 frames of the D channel of the ISDN interface n Out band signaling o The set of protocols for user signaling defines the DSS1 signaling system (ITU-T Q.930, Q.931 e Q.932) o DSS1 messages are transported directly into LAPD frames DSS1 LAPD DSS1 LAPD L1 L1 L1 TE NT1 LE A. Capone: Mobile Radio Network 8

9 User signaling: ISDN U Plane C Plane Supplementary services I I.257 Q.932 Q.931 Q.920 LAPD Information Elements for Supplementary services Messages for Supplementary services Messages for Basic call Packet connection on D channel Multiplexing error control 1 I.430/I.431 I.430/I.431 Digital interface (physical layer) Non symmetric protocol A. Capone: Mobile Radio Network 9

10 User signaling: ISDN o Messages for the basic call (Q.931) includes a header common to all message types and a sequence of information elements depending on the type byte Protocol discriminator 1 Protocol discriminator CRV Length 2 CRV: Call Referece Values CRF: Call Reference Flag CRF CRV 3 CRV (only for PRI) 4 0 Message type Other information elements 5... A. Capone: Mobile Radio Network 10

11 User signaling: ISDN Message type Description ALERTING terminal ringing CALL PROCEDING CONNECT CONNECT ACKNOWLEDGE PROGRESS SETUP SETUP ACKNOWLEDGE DISCONNECT RELEASE RELEASE COMPLETE RESTART RESTART ACKNOWLEDGE INFORMATION call in progress set up completed acknowledgment of CONNECT message call in progress call setup request acknowledgment of SETUP message call disconnect request call release acknowledgment of RELEASE message restart request of signaling procedure acknowledgment of RESTART message information for call setup A. Capone: Mobile Radio Network 11

12 Basic call user telephone network destination Phone pickup Busy tone sound SETUP SETUP ACKNOWLEDGE Number selection Echo of number tones INFORMATION CALL PROCEEDING SETUP Channel D CALL PROCEEDING Ringing tone ALERTING ALERTING CONNECT CONNECT CONNECT ACKNOWLEDGE CONNECT ACKNOWLEDGE Hello? Hi, this is Antonio Hello? Hi, this is Antonio Hello? Hi, this is Antonio Channel B A. Capone: Mobile Radio Network 12

13 Basic call Terminal 1 network Terminal 2 DISCONNECT RELEASE RELEASE COMPLETE DISCONNECT RELEASE RELEASE COMPLETE A. Capone: Mobile Radio Network 13

14 Supplementary services Supplementary services with number identification DDI: Direct Dial In MSN: Multiple Subscriber Number CLIP: Calling Line Identification Presentation CLIR: Calling Line Identification Restriction COLP: Connected Line Identification Presentation COLR: Connected Line Identification Restriction MCI: Malicious Call Identification Subaddressing A. Capone: Mobile Radio Network 14

15 Supplementary services Supplementary services with call offer and completion CT: Call Transfer CFB: Call Forwarding on Busy CFNR: Call Forwarding on No Replay CFU: Call Forwarding on Unconditional CD: Call deflection CW: Call Waiting CH: Call Hold Call Park and Pickup CCBS: Completion of Calls to Busy Subscribers A. Capone: Mobile Radio Network 15

16 Supplementary services Other supplementary services CONF: Conference Calling 3PTY: Three Party Service CUG: Closed User Group (Reti Private Virtuali) PNP: Private Numbering Plan OCB: Outgoing Call Barring CRED: Credit Card Calling AOC: Advice of Charge RC: Reverse Charging A. Capone: Mobile Radio Network 16

17 Supplementary services o Supplementary serives are accessible through specific user procedures and a functional protocol o The functional protocol makes use of Q.932 Facility messages that includes the Facility and User-to-User information elements, used in command-response mode: o request o reply o error o reject Q.932 Messages Facility Hold Hold Acknowledge Hold Reject Retrieve Retrieve Acknowledge Retrieve Reject A. Capone: Mobile Radio Network 17

18 Network signaling o Modern network signaling is called out of band signaling, because it makes use of separate communication channels o It is also called Common Channel Signaling (CCS) since it is based on a packet switching network o CCS is n A datagram network n With network nodes separate from those of the circuit switching network o SS7 (signaling system no. 7) is the protocol stack widely used for telephony A. Capone: Mobile Radio Network 18

19 SS7 Service Control Point SCP SCP Signaling Transfer Point STP STP STP STP Service Switching Point SSP SSP A. Capone: Mobile Radio Network 19

20 SS7 Signaling Transfer Point SS7 Protocols Signaling Transfer Point /Signaling End Point Service Switching Point STP Physical channel STP SEP SSP SSP Transport trunk A. Capone: Mobile Radio Network 20

21 SS7 o The lower part of the SS7 protocol stack includes the physical, link and network layers for the datagram packet switched network o This part of the stack is called MTP (Message Tranfer Part) o It is rather similar to IP stack MTP-3 MTP-3 MTP-2 MTP-1 SP MTP-2 MTP-1 SP MTP-3 MTP-2 MTP-1 SP A. Capone: Mobile Radio Network 21

22 SS7 7 OMAP ASE TCAP ISDN-UP (ISUP) Basic call and Supplementary services 3 SCCP MTP - 3 Transport and connection Datagram routing 2 MTP MTP - 1 ISUP: ISDN User part TCAP: Transaction Capabilities Application Part SCCP: Signaling Connection Control Part MTP: Message Transfer Part OMAP: Operation, Maintenance and Administration Part ASE: Application Service Element A. Capone: Mobile Radio Network 22

23 ISUP In ISUP messages map one to one DSS1 messages SETUP ALERTING CONNECT DISCONNECT.. Initial Address Message (IAM) Address Complete Message (ACM) Answer Message (ANM) Release (REL). A. Capone: Mobile Radio Network 23

24 Basic call in SS7 TE LE Transit station LE TE SETUP INFORMATION IAM IAM SETUP CALL PROCEEDING ALERTING CONNECT ACM ANM ACM ANM ALERTING CONNECT CONNECT ACKNOWLEDGE CONNECT ACKNOWLEDGE Channel B End to end circuit Channel B DISCONNECT RELEASE RELEASE COMPL REL RLC REL RLC DISCONNECT RELEASE RELEASE COMPL A. Capone: Mobile Radio Network 24

25 Intelligent Network (IN) application services It processes supplementary service requests from users and application messages from other IN nodes Intelligent Peripheral IP SSP STP SS7 Network STP SCP Service Control Point It provides IN services (mapping of 800 numbers, call screening, private numbering plan, televoting, ) A. Capone: Mobile Radio Network 25

26 Intelligent Network (IN) application services IN provides information services that are then used for enriching the basic call service SSP IP SCP STP STP STP STP A. Capone: Mobile Radio Network 26

27 TCAP Messages for a service execution are grouped into transactions ASE Application Service Element transaction ASE Application Service Element Begin Continue End Abort Unidirectional Originating TID Destination TID P-abort-cause U-abort-cause Component Portion A. Capone: Mobile Radio Network 27

28 TCAP Messages are used for remote function calls according to a client-server paradigm, however the protocol is symmetric Invoke Return Result Return Error Reject Invoke Return-Result-Last Return-Result-Not-Last Return-Error Reject Invoke-ID Linked-ID Operation-Code Error-Code General-problem Return-Result-Problem Return-Error-Problem Parameter A. Capone: Mobile Radio Network 28

29 IN service example: 800 mapping IP (access station) BEGIN - invoke ID # 1 (request for number xxxxx) SCP (network database) CONTINUE - invoke ID # 2 (automatic responder: ask additional digits) CONTINUE - RR ID # 2 (additional digits) END - RR ID # 1 (number mapping) A. Capone: Mobile Radio Network 29

30 GSM signaling A. Capone: Mobile Radio Network 30

31 GSM signaling o SS7 signaling used in PSTN is not sufficient for GSM o Additional functionalities are added for mobile radio networks o For the network part the SS7 network is extended with additional application layer services (IN services) o For the access part new protocols are added for allowing: n The signaling exchange between MS and MSC n The communication between BTS, BSC and MSC A. Capone: Mobile Radio Network 31

32 GSM SS7 MAP BSSAP TCAP ISUP SCCP MTP level 3 MTP level 2 MTP level 1 MTP=Message Transfer Part ISUP=ISDN User Part MAP=Mobile Application Part SCCP=Signalling Connection and Control Part BSSAP=Base Station Sub-system Application Part TCAP=Transaction Capabilities Application Part A. Capone: Mobile Radio Network 32

33 Access network signaling CM MM MS BTS BSC MSC CM MM RR RR BTSM RR BTSM BSSAP DTAP BSSMAP BSSMAP SCCP SCCP LAPDm fisico LAPDm fisico LAPD fisico LAPD fisico MTP MTP BTSM=BTS Management BSSMAP=BSS Mobile Appl. Part DTAP=Direct Transfer Appl. Part RR=Radio Resource management MM=Mobility Management CM=Connection Management A. Capone: Mobile Radio Network 33

34 BSSMAP o BSSMAP is the protocol for the exchange of signaling between BSC and MSC n all BSSMAP messages sent from MSC requires an interpretation by the BSC n For example: o Messages for starting paging procedure for a new incoming call o Messages for the authentication procedure o Etc. A. Capone: Mobile Radio Network 34

35 DTAP o DTAP is in charge of creating a direct communication channel between MSC and MS o It is a kind of tunnel of signaling messages o DTAP is actually used only between MSC and BSC, since then at the other interfaces signaling messages are simply forwarded by lower layer protocols o DTAP are BSSMAP are part of the BSSAP A. Capone: Mobile Radio Network 35

36 BTSM o BTSM is the protocol for signaling exchange between BSC and BTS n all BTSM messages sent by the BSC require an interpretation by the BTS n It is mainly used by the BSC for configuration commands n And by the BTS for sending radio measurements A. Capone: Mobile Radio Network 36

37 Radio Resource management (RR) o It s the level that manages radio resources which involves MS, BTS e BSC o The RR: n Manages initial access messages on RACH and AGCH n Handles measurements on the SACCH n Manages exchange of messages for resource reassignment during handover n Manages timing advance and power control n etc. A. Capone: Mobile Radio Network 37

38 Connection Management (CM) o CM manages the exchange of messages for call setup o It is mainly based on the same user signaling of PSTN o CM messages trigger other actions (like RR or BTS configuration) performed through other protocols A. Capone: Mobile Radio Network 38

39 Mobility Management (MM) o MM manages the signaling exchange for mobility management (location update, paging) and authentication o Examples of MM procedures n Location updating n Authentication n IMSI attach and detach A. Capone: Mobile Radio Network 39

40 Protocol Stack in HLR MAP TCAP SCCP MTP level 3 MTP level 2 MTP level 1 A. Capone: Mobile Radio Network 40

41 Signaling Protocols MSC BSSAP SCCP MAP TCAP TUP / ISUP PSTN Exchange SCCP TUP / ISUP MTP MTP BSC BSSAP SCCP MTP HLR MAP TCAP SCCP MTP A. Capone: Mobile Radio Network 41

42 Numbers and identities o Telephone numbers: n MSISDN (Mobile Station ISDN Number) n MSRN (Mobile Station Roaming Number) n Handover Number o User and terminal identities: n IMSI (International Mobile Subscriber Identity) n TMSI (Temporary Mobile Subscriber Identity) n IMEI (International Mobile Equipment Identity) A. Capone: Mobile Radio Network 42

43 Numbers and identities o Network IDs: n LAI (Location Area Identity) n CGI (Cell Global Identity) n RSZI (Regional Subscription Zone Identity) n BSIC (Base Station Identity Code) A. Capone: Mobile Radio Network 43

44 Communication services in GSM o Basic Services n Teleservices: are application services (from source coding/decoding to information delivery) to like telephone service, SMS, etc. n Bearer Services: provides end-to-end transport of information flows (like data services) o Supplementary services: n Same as in PSTN A. Capone: Mobile Radio Network 44

45 Teleservices Service Description GSM Specification Code Features Speech (Telephony) T11 The most important service for mobile systems, normal speech service, including emergency calls Speech (Emergency Calls) T12 Emergency calls are possible automatically Short Message Service (Mobile terminated) Short Message Service (Mobile originated) Short Message Service (cell broadcast) T21 T22 T23 For the reception of Short messages For sending a short message to another GSM subscriber For sending short messages to more than one receiver simultaneously within a given cell A. Capone: Mobile Radio Network 45

46 Short Message Service Air A MSC BTS BSC TC VLR Mobile Originate SMS Mobile Terminated SMS SMS Alfaskopm346 Alfaskopm346 Alfaskopm346 6 A. Capone: Mobile Radio Network 46

47 Short Message Service (Cell Broadcast) Alfa s k op m3 46 Alfa sk opm34 6 Alfas k op m34 6 Air A B TS B TS B TS B SC B TS B TS SMS, Cell Broadcast O & M A. Capone: Mobile Radio Network 47

48 Signaling procedures A. Capone: Mobile Radio Network 48

49 Examples of signaling procedures o Network access o Mobility o Originated Call Setup o Handover o Terminated Call Setup A. Capone: Mobile Radio Network 49

50 Registrations and Location Update A. Capone: Mobile Radio Network 50

51 Turning on a MS o When a MS is turned on the following procedures are performed: n Cell Selection: the MS selects the BTS for the connection n Registration: the MS informs the MSC that it is active and updates information on the Location Area A. Capone: Mobile Radio Network 51

52 Cell Selection o The MS scans the radio carriers n The carriers on which the BCCH is transmitted are called c0 n These carries are at constant power (dummy bursts are used) and frequency hopping is disabled o Through the FCCH the MS synchronizes with the BTS carrier o Through the SCH the MS synchronizes slot and frame and receives the BSIC o The MS can now decode the BCCH that includes o LAC (Location Area Code) o CGI (Cell Glocal Identity) o MCC (Mobile Country Code) o MNC (Mobile Network Code) o The MS selects the BTS with the strongest c0 carrier A. Capone: Mobile Radio Network 52

53 Registration o Two possible cases: n The LAI received is the same stored in the SIM (phone turned off and then turned on in the same LA). An IMSI attach procedure is initiated and the IMSI is marked as active in the VLR. n No LAI stored or LAI received different from the stored one (phone turned off and then on in a different LA). A Location Update procedure is initiated A. Capone: Mobile Radio Network 53

54 Location Update o Two types of Location Update: n Two LAs of the same MSC/VLR LA 1 LA 2 BTS 1 BTS 2 BSC BSC MSC VLR A. Capone: Mobile Radio Network 54

55 Location Update o Two LAs of different MSC/VLR LA 2 LA 1 BTS 2 BTS 1 BSC BSC MSC VLR 1 MSC VLR 2 A. Capone: Mobile Radio Network 55

56 Location Update - Intra MSC Location Update Req +TMSI old + LAI old Location Update Req BSC MSC VLR Location Update Ack + new TMSI BTS Location Update Ack + new TMSI IMSI New TMSI New LAC A. Capone: Mobile Radio Network 56

57 Location Update - Intra MSC Messages Channels MS CHAN REQ IMMEDIATE ASSIGNMENT LOC UPD REQ AUTH REQ AUTH RES CIPH MOD CMD CIPH MOD COM LOC UPD ACK + TMSI new RACH AGCH SDCCH SDCCH SDCCH SDCCH SDCCH SDCCH Network TMSI REALL CMD SDCCH CHAN REL SDCCH A. Capone: Mobile Radio Network 57

58 Location Update - Inter MSC HLR MSC (old) MSC (new) VLR VLR BTS (new) A. Capone: Mobile Radio Network 58

59 Location Update - Inter MSC MS BSS MSC VLR new VLR old HLR 1. channel assignment 2. location update request (TMSI+LAI) 3. request subscriber identity (TMSI) 4. provide subscriber identity (IMSI) 5. request subscriber data 6. provide subscriber data 7. security procedures 8. Location update 9. HLR update 10. acknowledgement update 11. cancel old location 12. location cancelling accepted A. Capone: Mobile Radio Network 59

60 Call Setup A. Capone: Mobile Radio Network 60

61 Mobile terminated call (originated from PSTN) PSTN Cellular Network o For setting up a call terminated on a mobile user some additional steps w.r.t. the case of fixed lines are required A. Capone: Mobile Radio Network 61

62 Mobile terminated call 1) The PSTN/ISDN user digits the Mobile Subscriber International ISDN Number (MSISDN) of the called user PSTN MSISDN MSISDN: = Country Code (Italy) 347 = National Destination code = Subscriber Number A. Capone: Mobile Radio Network 62

63 Mobile terminated call 2) The PSTN/ISDN network analyzes the number and routes the call (ISUP signaling) to the GMSC of the PLMN making use of the National Destination Code (NDC) 3) The GMSC receive the call setup request through the SS7 network with the MSISDN called GSM Network HLR PSTN MSISDN VLR GMSC A. Capone: Mobile Radio Network 63

64 Mobile terminated call 4) The GMSC identifies the HLR of the called user through the MSISDN (the GMSC does not know the MS position!) 5) The GMSC send a HLR Enquiry message to the HLR (MAP message) 6) The HLR analyzes the message, identifies in its record the IMSI corresponding to the MSISDN and the VLR currently visited by the MS PSTN MSISDN GSM Network GMSC A. Capone: Mobile Radio Network 64 VLR MSC HLR VLR

65 Mobile terminated call 7) The HLR sends a Routing information request to the MSC/VLR (MAP message) 8) The MSC/VLR allocates temporarily a Mobile Station Roaming Number (MSRN) for the call o The MSRN is similar to the MSISDN, and it can be used for routing the call using ISUP o MSRN = CC + NDC + SN n n n CC = Country Code NDC = National Destination Code SN = Subscriber Number GSM Network GMSC VLR MSC HLR Routing Information Request VLR A. Capone: Mobile Radio Network 65

66 Mobile terminated call 9) The MSC forwards the MSRN to the HLR (MAP message) 10)The HLR forwards it to the GMSC (MAP message) 11) The GMSC routes the call using MSRN to the MSC/VLR (ISUP signaling) MSRN HLR GSM Network VLR MSRN GMSC VLR MSC A. Capone: Mobile Radio Network 66

67 Mobile terminated call 12) The MSC/VLR activates the paging procedure n It identifies the currently visited LA n It sends a paging command to BSCs of the area 13)BSCs activate paging on their BTSs using the PCH (paging message contains the TMSI of the MS) 14)The MS replies to the paging message starting an access procedure on the Random Access CHannel (RACH) and get a Stand alone Dedicated Control CHannel (SDCCH) assigned A. Capone: Mobile Radio Network 67

68 Mobile terminated call 15) The MSC/VLR activates the authentication procedure 16) The MS start the call setup signaling (informing it is a reply to paging) call setup similar to ISDN 17) A TCH is assigned for the call 18) Called phone rings and the MSC/VLR inform caller that called user terminal is ringing 19)The user answer to the call. A. Capone: Mobile Radio Network 68

69 Mobile terminated call A. Capone: Mobile Radio Network 69

70 Mobile terminated call (international roaming) 70 A. Capone: Mobile Radio Network

71 Mobile terminated call (international roaming) A. Capone: Mobile Radio Network 71

72 Mobile terminated call: Recap Fixed Caller PSTN/ ISDN GMSC HLR MSC/VLR BSC+BTS Called MS Call Setup (MSISDN) Analyze Number Call Setup (MSISDN) MSISDN MSRN Call Setup (MSRN) IMSI MSRN Page Page resp. Ack. Page req. (PCH) Channel resp. (SDCCH) Channel ack. (SDCCH) Authenticat.,ciphering,TMSI reallocat. A. Capone: Mobile Radio Network 72

73 Mobile terminated call: Recap Fixed Caller PSTN/ ISDN GMSC HLR MSC/VLR BSC+BTS Connection Setup Called MS Connection Confirmation TCH Assign Req. TCH Assign Command Ringing Connection established Ringing notice Unhook notice Alert Connect Connect ack. A. Capone: Mobile Radio Network 73

74 Mobile originated call o User digits the number and the MS starts the access procedure o A call setup signaling procedure is activated on the SDCCH o If the called number is in the same PLMN, a HLR enquiry procedure is initiated n Same procedure as mobile terminated call o If the called number is of another network the call is routed to the GMSC (ISUP signaling). A. Capone: Mobile Radio Network 74

75 Mobile originated call EXC GMSC HLR MSC/VLR BSS MS 1. channel assignment 2. Authenticat., ciphering,tmsi reallocat. 8.set up the call 3. call setup 4. check services etc. 5. all ok 6. call is proceeding 7. allocate TCH 9. call set up done 10. alert 11. if B answers the call will be connected A. Capone: Mobile Radio Network 75

76 Mobile originated call RACH AGCH CHAN REQ IMM ASSIGN SDCCH assignment MS SDCCH SABM UA Service Request SDCCH SDCCH SET UP ASSIGNMENT CONNECT ACK Authentication Ciphering TCH/SACCH Assignment Network TCH SACCH DISCONNECT RELEASE RELEASE COMPLTE TCH/SACCH Release A. Capone: Mobile Radio Network 76

77 Number portability Fixed network: a) Call forwarding A. Capone: Mobile Radio Network 77

78 Number portability Fixed Network b) Query and Release A. Capone: Mobile Radio Network 78

79 Number portability Fixed Network c) All call query A. Capone: Mobile Radio Network 79

80 Number portability Mobile radio network a) Call forwarding A. Capone: Mobile Radio Network 80

81 Number portability Mobile radio network b) All-call query (ver. 1) IRN MSISDN A. Capone: Mobile Radio Network 81

82 Number portability Mobile radio network c) All-call query (ver. 2) MSISDN A. Capone: Mobile Radio Network 82

83 Handover A. Capone: Mobile Radio Network 83

84 Handover in GSM o In GSM (like in all other cellular technologies) the handover procedure is initiated by the network, even it is based also on measurements provided by the MS o Using adjacent BTS list, the MS scans c0 carriers and makes received power measurements o The measurements are sent to the BSC using the SACCH (a complete set every 480 ms) o The BSC analizes measurements from MS and BTS and if necessary (algorithms may be different) initiates a handover procedure A. Capone: Mobile Radio Network 84

85 Handover parameters o MS: n Signal strength on the BCCH carrier of the adjacent cells (RXLEVNCELLn) n Signal strength of the TCH (RXLEV) n Quality (BLER) of the TCH (RXQUAL) o BTS n Signal strength from MS on the TCH (RXLEV) n Quality of the TCH (RXQUAL) n Timing Advance A. Capone: Mobile Radio Network 85

86 Handover activation o Low quality (RXLEV and/or RXQUAL below threshold) o Distance MS/BTS above a threshold (timing advance) o Better adjacent cell o Traffic (cell too loaded) o Control and maintenance A. Capone: Mobile Radio Network 86

87 Types of Handover 4 types Intra Cell - Intra BSC Inter Cell - Intra BSC Inter Cell - Inter BSC Inter MSC A. Capone: Mobile Radio Network 87

88 Intra Cell - Intra BSC Handover Air A BTS B SC TC Old radio channel New radio channel A. Capone: Mobile Radio Network 88

89 Inter Cell - Intra BSC Handover A ir A BTS BSC TC BTS Old cell / BTS New cell / BTS A. Capone: Mobile Radio Network 89

90 Inter Cell - Intra BSC Handover The procedure is completely controlled by the BSC the BSC identifies the best BTS and the best TCH the BSC activate the TCH in the new BTS the BSC command the MS to switch to the new carrier and time slot in the new BTS The MS switches the call The old channel is released The BSC informs the MSC/VLR than an handover has been executed and if necessary performs a location upddate The MS start collecting measurements in the new cell A. Capone: Mobile Radio Network 90

91 Inter Cell - Inter BSC Handover A i r New cell / BTS A BTS B SC TC M S C VLR B TS B SC TC Old cell / BTS A. Capone: Mobile Radio Network 91

92 Inter Cell - Inter BSC Handover The handover procedure is initiated by the BSC the BSC identifies the best BTS the BSC sends a message to the MSC/VLR with the new BTS identity The MSC commands the new BSC to prepare for handover The new BSC assigns a TCH for the MS and informs the MSC The MSC forward TCH information to the previous BSC The previous BSC command the MS to switch to the new TCH The MS switches The old channels are released A. Capone: Mobile Radio Network 92

93 Inter MSC Handover Air New cell / BTS A B TS B SC TC M S C VLR BTS B SC TC M S C VLR Old cell / BTS A. Capone: Mobile Radio Network 93

94 Inter MSC Handover The procedure is initiated by the BSC The BSC starts the handover and selects the BTS The BSC informs the MSC/VLR sending a handover request to the anchor MSC/VLR The anchor MSC/VLR sends a request to new MSC/VLR The new MSC/VLR allocates a HandOver Number (HON) and transmits it to the anchor MSC/VLR The anchor MSC/VLR used the HON for setting up a circuit with the new MSC/VLR (ISUP) A. Capone: Mobile Radio Network 94

95 Inter MSC Handover (2) The new MSC/VLR creates a connection with the new BSC The new BSC reserves a TCH in the new BTS and informs the new MSC The new MSC informs the anchor MSC The anchor MSC informs the BSC that commands the MS to switch to the new TCH the MS switches and activates the new channel The old channels are released A. Capone: Mobile Radio Network 95

96 HandOver Number o Same format of MSRN and MSISDN o HON = CC + NDC + SN n CC = Country Code n NDC = National Destination Code n SN = Subscriber Number A. Capone: Mobile Radio Network 96