Research And Development Of Bluetooth Wireless VoIP Access Gateway

As voice communications is the primary media of communication for human being, it plays a very important role from public switched telephone network to the third generation mobile communications. Now the rapid development of Internet makes Voice over IP to be a new choice for communications which leads strong impact on traditional instrument of communication. We can easily believe that by looking into the Skype system. The total number of Skype subscriber is up to 6,100,000 and about 170,000 new users increased everyday. But how to get rid of the space restrict and make it to be a mobile system is the most confused problem of VoIP development. Experts of mobile communications agree to combine VoIP and IEEE 802.11 technology, and some experiments are still in progress at present. Some research results have proved that WLAN cannot support high QoS for real-time transport, because CSMA/CA technique is unfitable when users achieved a certain number in area coverage. For reasons listed above, a new solution of wireless VoIP is given in the paper.Bluetooth has its own advantages comparing with WLAN. First, it is designed for short distance data and voice communications. The most popular example is Bluetooth earphone working with mobile handset. Second, service discovery protocol profile and cordless telephony profile defined by Bluetooth Special Interest Group provided us modes of application for reference. Using Bluetooth for wireless access point and using SIP for VoIP stack is the basic idea for wireless VoIP gateway proposed in this paper. The content of this paper focuses on application model, system architecture, protocol interface, signaling switch and processing control. So a realizable wireless VoIP gateway will be designed based on Bluetooth and SIP specification with a given embody hardware and software system.The key point of combination between Bluetooth and VoIP technology are listed as follows: (1) Definition and control of interface should be confirmed in the system. As Bluetooth and main control processor both have DSP calculate unit, pulse code modulation is used for their voice communications. For signaling control, USB host control interface protocol is the best choice for signaling switch, because it's the most integrated set at the top of Bluetooth link layer. It also provides hardware environment for big block data transport in future. (2) The connecting of telephony control protocol and session initial protocol should be seamless. These two protocols are responsible for...