Approximation of message inter-arrival and inter-departure time distributions in IMS/NGN architecture using phase-type distributions

Currently it is assumed that requirements of the information society for delivering multimedia services will be satisfied by the Next Generation Network (NGN) architecture, which includes elements of the IP Multimedia Subsystem (IMS) solution. In order to guarantee Quality of Service (QoS), NGN has to be appropriately designed and dimensioned. Therefore, proper traffic models should be proposed and applied. This requires determination of queuing models adequate to message inter-arrival and interdeparture time distributions in the network. In the paper the above mentioned distributions in different points of a single domain of NGN are investigated, using a simulation model developed according to the latest standards and research. Relations between network parameters and obtained message inter-arrival as well as interdeparture time distributions are indicated. Moreover, possibility of approximating the above mentioned distributions using phase-type distributions is investigated, which can be helpful in identifying proper queuing models and constructing an analytical model suitable for NGN.