A VoIP System On Symbian OS

A mobile phone VoIP client solution based on Symbian OS is presented in this paper. Considering the specialty of Symbian OS and mobile phone platform, this solution is based on SIP and access internet by WLAN to make phone calls via IP. Using this client in mobile phone, phone calls can get through without mobile operator's network.In this paper, the multi-layer design of this VoIP client is presented. MVC design pattern is used in the framework of this VoIP client. The main components of this VoIP client are described which include UI, Phone Engine, SIP Engine, Talk Engine, etc. The main functions of these components are introduced and the design patterns of the components are discussed, e.g. Phone Engine and SIP Engine uses State Pattern to implement their State Machine, components at different layers use Observer Pattern to communicate. Some details of the Implementation and technologies are presented, e.g. SIP Resolver Framework in SIP Engine, actions within Transactions, SDP within SIP messages, recording and playing in Talk Engine and the receiving buffer.The experimental result is given based on a test network and Nokia phones. The result is good for practical uses.