QoS signalling in IP multimedia subsystem of UMTS

IMS is standardised by 3GPP as a control domain inside UMTS core network, that provides support for IP based multimedia services while SIP is used as the main signalling protocol. UMTS network needs to find QoS requests of IP multimedia session through signalling protocol before it reserves resources for communication. Therefore it is necessary to enable interworking between SIP protocol and IP QoS mechanisms. DiffServ is scalable and simple mechanism for providing QoS support in UMTS core network. In this paper is presented one example of providing end-to-end QoS for audio and video session between two UMTS user equipments when DiffServ is integrated in IMS transport layer.