Chap 5. IS-41 Network Signaling Network Computing LAB. 홍 정 표 ( jphong@kw.ac.kr )

Signaling System No. 7 Signaling System NO. 7 PSTN signaling protocol interconnection between a PCN and the PSTN There are six types of SS7 signaling links. Two Types, A-Link (access link) and D-Link (diagonal link) STP SCP HLR MSC SSP Trunk PSTN PCN (PCS Network) (SCP) A-Link D-Link

Signaling System No. 7 SS7 protocol Layers OMAP MAP TCAP SCCP ISDN-UP MTP Level 3 MTP Level 2 MTP Level 1 OSI Layers Application Presentation Session Transport Network Data Link Physical The SS7 Layers

Signaling System No. 7 MTP (Message Transfer Part) – Transfer Signaling information MTP Level 2 provides reliable transfer of signaling message MTP Level 3 provides message routing and network management SCCP (Signaling Connection Control Part) Provides additional functions such as GTT to the MTP TCAP (Transaction Capabilities Application Part) Provides the capability to exchange information between using noncircuit-related signaling ISUP-UP (Integrated Services Digital Network User Part) Establishes circuit-switched network connections OMAP (Operations, Maintenance, and Administration part) Application of TCAP MAP (Mobile Application Part) Both IS-41 & GSM MAP are implemented at this layer

Interconnection and Message Routing STP MSC Tandem PSTN PCN Type S (A-Links) Type 2A with SS7 interface Type 2A with SS7 interface STP MSC Tandem PSTN PCN Type S (D-Links) STP MSC End Office PSTN PCN Type S (A-Links) Type 2B with SS7 interface STP STP Type S (D-Links) Type 2B with SS7 interface End Office MSC PSTN PCN

Interconnection and Message Routing SS7 message routing is preformed at the MTP and the SCCP of a node (SSP,STP or SCP) Signaling messages are delivered with the actual destination address at the MTP MTP level receives messages from TCAP, SCCP, ISUP DPC (destination point code) of the message uniquely identifies the destination node Routing to the destination node is determined by the MTP using lookup tables

Mobility Management Using TCAP TCAP operation More than 50 TCAP operation are defined For three purposes Inter-MSC handoff, automatic roaming, operations, administration, and maintenance TCAP message consists of two portions Transaction portion – define package type QueryWithPermission, Response ConversationWithPermission, Unidirectional Component portion – define number and types of components INVOKE, RETURN RESULT RETURN ERROR, REJECT

Mobility Management Using TCAP PCN1 PSTN PCN2 STP1 STP2 STP3 STP4 MSC1 VLR1 HLR VLR2 MSC2 RegistrationNotification (INVOKE) RegistrationNotification (INVOKE) T1 T2 RegistrationNotification (RETURN RESULT) RegistrationCancellation (INVOKE) RegistrationNotification (RETURN RESULT) T3 RegistrationCancellation (RETURN RESULT) RegistrationCancellation (INVOKE) T4 RegistrationCancellation (RETURN RESULT) QualificationRequest (INVOKE) T5 QualificationRequest (RETURN RESULT) ServiceProfileRequest (INVOKE) T6 ServiceProfileRequest (RETURN RESULT)

Mobility Management Using TCAP IS-41 TCAP message flow for MS registration Transaction 1 When MS is in MSC2’s service area, MSC2 sends a RegistrationNotification(INVOKE) to its VLR(VLR2) Transaction 2 If MSC1 is net served by VLR2, then VLR2 sends a RegistrationNotification(INVOKE) to the MS’s HLR Transaction 3 HLR sends a RegistrationCancellation(INVOKE) to the MS’s previously visited VLR (VLR1) Transaction 4 The cancellation propagates to MSC1 Transaction 5 After T2 is completed, VLR2 creates a registration record for MS Sends a QualificationRequest(INVOKE) to HLR to check MS’s qualification for receiving services Transaction 6 VLR2 sends a ServiceProfileRequest(INVOKE) to HLR to obtain the service profile for the roaming MS

PCN/PSTN Call Control Using ISUP STP STP 4 1 2 3 5 End Office Tandem MSC 6 7 Step 1 IAM IAM COT Step 2 COT ACM ACM Step 3 ANM Step 4 ANM Conversation using trunks (6) and (7) Signaling path from PSTN to PCN REL 1 2 3 4 5 Step 5 REL RLC Step 6 Signaling path from PCN to PSTN RLC 5 4 2 3 1

PCN/PSTN Call Control Using ISUP Typical message flow for type 2A with SS7 land-to-mobile call setup and release involving a tandem switch When MIN is dialed, end office (EO) notices that the number is for wireless service Suppose that EO has HLR query capability EO sends a query message to obtain MS’s TLDN (temporary local directory number) Messages exchanged among switches, VLR and HLR are TCAP messages

PCN/PSTN Call Control Using ISUP Step 1 After the MS’s TLDN is obtained, EO sends an Initial Address Message (IAM) to the PCN MSC to initiate signaling for trunk setup When IAM is sent, IAM timer is set at the EO EO expects to receive a response from MSC within timeout period Step 2 If IAM sent from the EO to tandem specifies a continuity check, selected trunk from tandem to EO After continuity check is successfully completed, Continuity Message (COT) is sent from EO to tandem, and trunk is set up Same procedure could be performed when MSC receives IAM from tandem

PCN/PSTN Call Control Using ISUP Step 3 When IAM arrives at MSC, MSC pages the MS One of following three events occurs MS is connected with another call This situation is referred to as call collision Call is processed with call forwarding or call waiting, or MSC returns REL message to EO with a cause indicating the busy line situation MS is idle MSC send Address Complete Message (ACM) to EO Message informs EO of MS information, charge indications, and end-to-end protocol requirements When the EO receives the ACM, the IAM timer is stopped Ms does not answer the page MSC returns REL message to EO

PCN/PSTN Call Control Using ISUP Step 4 When MS answers call, an Answer Message (ANM) is sent from MSC to EO Call is established through trunk path (6)(7) Step 5 EO sends a Release Message (REL) to indicate that specified trunk is being released from the connection Trunk is not set to idle is EO until a Release Complete Message (RLC) message is received Step 6 When MSC receives REL from EO, relies with a RLC After RLC is sent, EO and tandem waits for 0.5 to 1 sec. before it seizes the released trunk for the next call