SymPhone: design and implementation of a VoIP peer for Symbian mobile phones using Bluetooth and SIP

VoIP is born from the growing Internet infrastructure, which has over the years seen significant improvements in both bandwidth and end-to-end latency. In this paper, we explore making VoIP available on a mobile phone. For that purpose, we propose an architecture and describe the various components involved. Data entering and leaving the mobile phone is encapsulated in a wireless Bluetooth connection. The bridge to the Internet is provided by a linux Bluetooth access point. The system is compatible with current VoIP standards using RTP and SIP for data and signaling transmission, respectively. It has been tested to work in combination with several known softphones. Both RTP and SIP stack are built on top of a special IP emulation layer on the mobile phone, which has been developed to facilitate the migration of the application onto devices having a direct IP binding available for Bluetooth such as BNEP (Bluetooth Network Encapsulation Protocol). Apart from presenting design and implementation details, the paper also provides measurement results with regard to delay and session setup time and discusses certain limitations of the application evolving from restrictions imposed by the mobile phone's programming platform.