Wireless and Mobile Network Architectures

1. Wireless and Mobile Network Architectures Chapter 7 PACS Network Signaling

2. PACS Network Signaling • We describes network signaling for the Personal Access Communications System (PACS) • PACS supports basic call control, roaming, and handoff management • Does not use MSCs or HLR/VLR, but uses Advanced Intelligent Network (AIN) protocol with an Access Manager (AM), AIN switch, and AIN SCP, SSP

3. Advanced Intelligent Network (AIN) • By taking full advantage of the network intelligence generated by SS7 advancements • the Advanced Intelligent Network (AIN) can deliver new and profitable services to subscribers. • In the AIN environment, new services are not tied to the call-processing logic of individual switching systems, but are defined through the interworking of these switches and other network elements. • A switch is alerted to the need for AIN processing through various types of triggers that can accompany a call.

4. PACS Architecture

5. PACS Network Interfaces • The RPCU provides management and control functions between the RP and the local exchange network. • The access manager (AM) in the RPCU, it provides: • radio control : managing the RPs, trunk provisioning, RP to RP link transfers • non-radio service control : call control (managing the B channels), switching, routing • The RPCU has to deal with inter-RPCU handoff (similar to inter-BSC handoff) and inter-RP handoff. • Note: an AM is also located in the AIN SCP; the two interact with the ISDN/AIN Switch providing tunneling/de-tunneling (i.e., encapsulation) of the ISDN REGISTER messages over AIN.

6. The major goal of PACS network signaling • Utilize the existing AIN network entities, such as AIN SCP and SSP • there is no need to create new entities, such as MSC, using in other PCS systems. • In PACS signaling, telephony switching functions are separated from the PCS-related signaling • To achieve this goal • Noncall-associated signaling is introduced to minimize the modifications to the AIN SSP; that is, the AIN SSP does not interpret the PCS-related or IS-41-like signaling message • Many functions of the MSC have been removed from the SSP and moved to the AM and RPCU • The creation of the RPCU introduces a new kind of handoff : inter RPCU handoff

7. PACS Network Elements • AIN/ISDN Switch • The AIN switch is equipped with SS7, ISDN, and AIN capabilities. • SS7 ISUP is used in the switch to set up the trunks in call control and intersystem handoff. • The SS7 TCAP is used to support mobility management, and to transport AIN message between the switch and the SCP. • Triggering and querying • Triggering is the process of identifying calls that need AIN handling • Querying is the process of assembling an AIN message to an AIN SCP at a trigger detection point • ISDN/AIN Interworking • Noncall-associated (NCA) signaling provides a generic method for the SCP to communicate with an ISDN connected device through the switch

8. PACS Network Elements • AIN SCP • The AIN SCP provides the service logic, database, and operation capabilities to support HLR, VLR, AM and Auc. • The SCP communicates with the switch using AIN TCAP and the external PCS database using the IS-41 protocol. • The HLR contains a PCS application process, end-user service profiles, and accounting management capabilities. • Intelligent peripheral • 지능망 서비스에서 제공되는 각종 안내 멘트를 제공하고, 사용자와의 음성 인터페이스를 통해서 필요한 정보를 제공하며, 서비스를 위해 필요한 각종 정보(사용자 번호, 비밀번호, 서비스 선택 등)를 수집하는 기능을 제공합니다.

9. PACS Network Interfaces • AIN interface • During the call-processing procedure, the switch may detect the need for AIN processing at trigger detection points (TDPs) • Then process between the AIN switch and the AIN SCP • ISDN interface • The RPCU communicates with the switch via ISDN basic rate interfaces (BRIs)

10. In ISDN signaling, every message contains a common mandatory information element, referred to as the call reference. • ALERT • B channel selection • CALL-PROC • call establishment from the called party to calling party • CONN , CON-ACK • call acceptance by the called party • REL , REL-COM • SETUP • Call initiation from calling party to called party • FACILITY • To request permission for a handoff operation (AIN switch  RPCU) • REGISTER • To inform the VLR to carry out various operations

11. AIN/ISDN Interworking • With NCA signaling, the switch provides interworking functions between the SCP/VLR(AIN) and the RPCU (ISDN). • The ISDN messages exchanged between the switch and the RPCU are of type REGISTER • The AIN messages exchanged between the switch and the VLR are of type NCA_Data

12. MSG Type Invoke Component of Facility REGISTER Switch envelopNCAData RPCU VLR REGISTER (ISDN message) NCA_Data (AIN message) REL-COM MSG Type Package Type Component Type Component NCA_Data Unidirectional Invoke(Last) nCAData NCA Signaling Initiated by the RPCU • The RPCU initiates NCA signaling by sending an ISDN REGISTER message to the switch. • The switch forwards the information to the VLR using an AIN NCA_DATA message. <NCA signaling initiated by the RPCU> <NCA message format translation (ISDN to AIN)>

13. MSG Type Package Type Component Type Component NCA_Data Unidirectional Invoke(Last) VLR nCAData RPCU Switch NCA_Data REGISTER (AIN message) (ISDN message) REL-COM MSG Type Invoke Component of Facility REGISTER envelopNCAData5 NCA Signaling Initiated by the VLR • The VLR initiates NCA signaling by sending an AIN NCA_DATA message to switch. • The switch sends an ISDN REGISTER message to the RPCU. <NCA message format translation (AIN to ISDN)> <NCA signaling initiated by the VLR>

14. NCA Signaling Initiated by the VLR • The REL-COM message is to clear the invocation and the call reference of the REGISTER message. • The major goal of NCA signaling is to disassociate the AIN SSP from PCS-related signaling. • When the PCS signaling message is modified in the feature, there will be no need to change the switch. • NCA Signaling design feature • The AIN SSP only translates the NCA signaling from one format to another, the SSP does not interpret the message. • In the ISDN interface between the AIN SSP and the RPCU, the call reference is cancelled after every ISDN NCA message • In the AIN interface between the AIN SSP and the AIN SCP, the unidirectional TCAP message format is used instead of the general AIN transaction format- the query/response TCAP format

15. Registration

16. Call Origination

17. Call Termination

18. New Switch New Switch Old Switch Old Switch Old RPCU New RPCU Old RPCU New RPCU Intersystem Handoff Before the ALT After the ALT

19. Intersystem Handoff

20. Inter-RPCU hand-off approaches (b) After ALT (Switch Loopback) (c) After ALT (Direct Connect) (a) Before ALT (e) After ALT (Three-way Calling Connection) (d) During ALT (Three-way Calling Connection)

21. Inter-RPCU hand-off approaches • To minimize the impact of inter-RPCU handoff on the AIN SSP, tow anchor-RPCU handoff approaches have been proposed. • In the switch loopback, • The old RPCU dials the new RPCU to make the connection through the switch. • disadvantage : handoff consumes two more links between the switch and the RPCUs • In the Direct connection, • The RPCUs are connected with trunks • Disadvantage : extra trunks are required to connect the RPCUs and an inter-RPCUs handoff protocol is required • Three-way calling connection • Utilize the existing three-way calling facility of the AIN switch • Minor modifications to the RPCU , does not consume extra trunks