Traffic and load modelling of an IP mobile network

The IMS is being introduced by the 3GPP as part of the third generation mobile system to provide multimedia services to the wireless users. The session initiation protocol (SIP) has been chosen by 3GPP as the call control protocol within IMS. This paper describes a modelling tool developed in Fujitsu Laboratories for an IP mobile operator network (also called reference network), based on the 3GPP standard. The objectives of the tool are: to perform system dimensioning to determine the number of physical entities required to support different traffic scenarios based on the number of subscribers and number of calls/sessions and to assess the performance impacts for different service control scenarios such as home network based control as in 3GPP standard or visited network based control as a possible network evolution. The tool is implemented in Excel and incorporates a traffic model, a SIP server model, a functional model, and a system model based on the estimated user activity. The tool also provides the flexibility to allow investigations of the impact of different control scenarios and the impact of parameters on the SIP servers. In addition, the tool also has the flexibility to study the effect of moving functionalities between the different IMS entities. This paper provides an overview of the modelling tool. A brief description of the traffic model is provided. Then the SIP server model, the functional model, and the system model are introduced.. Finally, the simulation scenarios, home based control and visited based control, and their corresponding results on IMS dimensioning and performance analysis are presented.