Feasibility study of VoIP in 3GPP UMTS release 5 interworking with fixed networks

Abstract

The Universal Mobile Telecommunications System (UMTS) is denoted as a 3rd generation cellular system and has been designed with the objective to be a system with global coverage. With improvement of bandwidth capabilities, the UMTS system has the ability to support real time multimedia services. The focus in this thesis is Voice over IP (VoIP) which enables a user to make phone calls in the packet switched network in UMTS. This thesis starts with a presentation of VoIP with the quality requirements related to a voice session. A voice conversation needs a guaranteed quality to satisfy the participants. This thesis focuses on three main aspects; Quality of Service mechanisms (Best Effort, IntServ and DiffServ), VoIP in UMTS with a certain quality and last but not least implementation of Quality of Service (QoS) in a voice call interworking with external networks. Best Effort cannot be used when dealing with real time traffic such as VoIP. IntServ reserves resources from the application itself, and gives opportunity for each application in the terminal to request a certain quality. DiffServ works on a higher level and classifies traffic based on type of traffic, not for a particular request. For UMTS interworking with IP networks, the theoretical results suggest that IntServ over DiffServ should be used in the UMTS gateway node. An evaluation of the UMTS network is done by checking the voice quality attained by the network during a VoIP session in comparison of a traditional circuit switched call setup. Moreover, tests from the Norwegian UMTS network operator NetCom became useful when evaluating how well the VoIP could work when implementing UMTS release 5. The tests were set up with the focus on delay and voice quality in the network, and were meant for disclosing the differences with and without quality parameters during a transmission. Due to network restrictions the test results are limited.