Introduction 3G Wireless Network: – Core Network Architecture is changing. Drivers: – Demand for data and multimedia services in mobile environment. – Popularity of IP networks. Goal: – An all IP core network supporting data and multimedia services in 3G wireless network.
Packet Switched Core Network GPRS –Introduced Packet Switching Network entities: Serving GPRS support node (SGSN) Gateway GPRS support node (GGSN) – Mobile Station needs to perform Attach and Detach procedure Context Activation procedure
Packet Switched Core Network A simple block diagram of a packet switched network. (Solid lines: Data transfer and Signaling interface. Dotted lines: Signaling Interface)
Session Initiation Protocol (SIP) Signalling Protocol to handle the multimedia call control. An application layer protocol to create and terminate multimedia sessions. Supports –User Location –User Capability –User Availability Messages: INVITE, ACK, BYE, REGISTER.
Evolved Core Network Include architectural entities that support the signalling messages to set up multimedia calls: –Call State Control Function (CSCF) User communicates with CSCF at application layer, using SIP messages. CSCF is equivalent to a SIP server. Signalling path is different from media flow path.
Evolved Core Network A simple block diagram of a evolved packet switched network. (Solid lines: Data transfer and Signaling interface. Dotted lines: Signaling Interface)
Call Flow Entities in Signalling Path –User ( User Agent Client, User Agent Server) –Network Serving CSCF –Acts as a registrar. –Routes incoming and outgoing requests. Proxy CSCF – Immediate contact point of mobile station. HSS – Location Database.
GPRS Service Node Proxy CSCF Serving CSCF Radio Network Controller Serving CSCF Proxy CSCFRadio Network Controller Complete Signalling Path Mobile Station Base Station
Proxy CSCF Serving CSCF Proxy CSCF SIP Signalling Path Mobile Station Entities actually involved in session set up/termination. Message exchange at the application layer, intermediate entities are not aware of these messages.
Design & Implementation Project simulates all the entities in the SIP signalling path and shows the end-to-end call set up. User and network entities interact at the application layer: –Use socket services –UDP transport protocol
Design & Implementation Platform: UNIX, Language: C++ Object Oriented Methodology: –All the entities are objects. Main Objects: –User –ProxyCSCF –ServingCSCF –HSS
Design & Implementation User –Two Process: User Agent Client –Handles User Interface and initiates a call. User Agent Server –Listens for incoming calls. – Synchronization: Semaphore Locking.
Design & Implementation Network (Proxy and Serving CSCF) –Concurrent Server Fork a process to service incoming request. Main process loops infinitely to listen to incoming request. –Synchronized access to database, HSS. Semaphore locking.
Simulation Example Two Network Domains –ernie.ece.uic.edu –bert.ece.uic.edu Mobile Users –User1@ernie.ece.uic.eduUser1@ernie.ece.uic.edu –User2@bert.ece.uic.eduUser2@bert.ece.uic.edu Definitions –Call Origination (Initiating user to ServingCSCF) –Call Termination (ServingCSCF to destination user)
Example Scenarios Scenario 1: –User1@ernie: Current Location: ernie, HOME –User2@bert: Current Location: ernie, ROAMING Scenario 2: –User1@ernie: Current Location: bert, ROAMING –User2@bert: Current Location: ernie, ROAMING
Simulation Example Features implemented –If User2@bert not registered, error returned. –If User2@bert busy, Destination busy returned. –On receiving call, User2@bert may accept the call or reject the call. User1@ernie can hang up to terminate the session.
Proposed Change in the Signalling Path For Session Initiation, the signalling path may not include the ServingCSCF of the origination part. User profile can be downloaded to ProxyCSCF at the time of registration. ProxyCSCF performs the service control functionality instead of the ServingCSCF.
Results Proposed change results in decrease in Call Setup Delay. Caveat: Different Network Operators may not delegate service control to ProxyCSCF. Simulation demonstrates the signalling path for end-to-end call set up in “All IP” network.