Abstract
With the advancement of the Internet services and widespread of smart devices, there are many people starting to replace public switch telephone with VoIP software. Nowadays, voice over the Internet apparently becomes a highly discussed topic. However, in order to maintain a good conversation quality, it must cost a lot of bandwidth to use VoIP. Although Internet service providers provide billing plan with unlimited network access, not all people choose this kind of payments. How to improve the quality and stability of Internet conversation without costing a large amount of bandwidth has become an important issue. To deal with the bandwidth problem, we introduce Cloud Bridging Switch, CBS. Cloud Bridging Switch which bases on cloud architecture is loading balanced dynamically according to demands. Moreover, CBS can bridge VoIP and PSTN, and it only costs very little bandwidth when initializing the call. All the audio packets in the call are delivered through PSTN, therefore users need not to pay the extra fee to the service provider. In addition, since the packets do not rely on the mobile network, the quality and steadiness of call are much better than of traditional VoIP software. In this thesis, we build a series of cloud servers to provide SIP based voice services. The servers feature the high flexibility of cloud architecture. We also developed three Android application programs which can access to the cloud service and make one-to-one or many-to-many calls at low cost.