Analysis of SIP in UMTS IP Multimedia Subsystem

Abstract

As a key member of the 3G mobile technologies identified by the ITU (international Telecommunication Union), UMTS (Universal Mobile Telecommunications System) represents an evolution in terms of services and data speeds from today's 2G mobile networks. Third Generation Partnership Project (3GPP) was formed to work on the technical specification of UMTS.

A UMTS network consists of three interacting domains: Core Network (CN), UMTS Terrestrial Radio Access Network (UTRAN) and User Equipment (UE). The IP multimedia subsystem comprises all CN elements for provision of multimedia services. The Session Initiation Protocol has been chosen by the 3GPP for establishing multimedia sessions in UMTS Release 5 networks.

The purpose of the research has been to analyze the SIP operation in IP Multimedia Subsystem of UMTS network from two aspects: bottleneck and delay.

The bottleneck analysis was based on the investigation of the detailed call set up and release procedures. The signaling flows hit each functional entities (CSCF or HSS) along the routing chains of signaling traffic several times. Once hit, the functional entity provides some service and then forwards the traffic on. We counted the hit times of each functional entity and identified the bottlenecks in different scenarios. We concluded that which one node would be the bottleneck depends on how the traffic is distributed in the networks.

We did the delay analysis firstly by describing the SIP signaling traffic with M/M/1 notation. We calculated the delay in each node and gave the waiting time distribution. Then we assumed the traffic to be M/D/1 and gave the delay in each node. The total delay in a call set up/release procedure is the summation of the delay of the nodes along the signaling path. We got that the M/M/1 analysis provides us the upper bound of the average waiting time of each node, as well as the average delay in the call set up/release procedure.