ABSTRACT
Circuit switched (CS) voice used to be the only way to provide voice service in the cellular networks, but during the past few years there has been growing interest to use cellular networks for real-time (RT) packet-switched (PS) services such as Voice over Internet Protocol (VoIP) to provide voice service without circuit switched service. The main motivation for the operators to use VoIP instead of CS voice are the savings, that could be achieved when the CS related part of the network would not be needed anymore. It is also expected that VoIP can bring better capacity than CS voice due to more effi cient utilization of resources. Supporting VoIP in any radio access technology faces certain challenges due to VoIP traffi c characteristics (strict delay requirements, small packet sizes), which make the effi cient exploitation of radio interface capacity diffi cult due to control channel constraints. The solutions to these challenges vary for different technologies.
