Design And Implementation Of Communication Agent Client Based On VoIP

With the rapid development of economic globalization, more and more business men choose to go abroad for their business extension. However, when they are on business, they are faced with the high cost of international roaming charges. This paper presents a new solution which can effectively reduce the roaming charges and is also legal in China. This solution can be realized easily and conveniently with a low cost.The communication proxy device is implemented based on PJSIP and BlueZ which are open-source protocols under Linux operating system. The device includes GSM module, Bluetooth communication module, control module and VoIP client module. The GSM module connects the PSTN network and transfer voice data to Bluetooth module. At the same time it receives AT commands sent by the Bluetooth communication module. The Bluetooth communication module needs to transfer the voice data between GSM module and VoIP client module. In the meantime, it should send AT commands to control the call. The control module is the core part of the communication proxy device which plays an important role in the communication proxy device. The control module takes command of the GSM phone module and the VoIP client module to accomplish the establishment, maintenance and release of communication link. It also transfers control information between the GSM phone module and the VoIP client module. The VoIP client module controlled by the control module needs to transfer voice data with the Bluetooth communication module. It also needs to invite and receive a phone call.This solution has an advantage over others because it allows subscriber who uses this device to not only answer a call but also make a call. Meanwhile, when someone uses this device to make or answer a call in other place, the voice data is transmitted through Internet, so the cost is greatly reduced since the data transmission isn’t completed by the roaming communication. On the other side, the cost of the device is very low, and the design is legal so it can be used in business.According to a serious of test under the Ubuntu Linux system, we draw a conclusion that the basic function of the communication proxy device is stably, it can control the phone call perfectly and handle calls in different states. In a word, the proxy device achieves the communication function and completes the intended goal of reducing roaming charges.