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In this paper we investigate the problem of voice communications across heterogeneous telephony systems on dual-mode (WiFi and GSM) mobile devices. Since GSM is a circuit-switched telephony system, existing solutions that are based on packet-switched network protocols cannot be used. We show in this paper that an enabling technology for seamless voice(More)
As the popularity of multi-functional communication devices grows, traditional audio conferencing now may involve heterogeneous teleconferencing devices, including POTS phone, VoIP phones, dual-mode smart phones, and so on. During a multi-party audio conference involving heterogeneous devices, it is possible that a video conference is held concurrently(More)
In this paper, we consider a university campus that has an established infrastructure for supporting SIP-based VoIP service through the campus wireless data network. The campus WIAN, however, does not have 100% full coverage , and hence users cannot make untethered VoIP calls anywhere on campus. The goal of this paper is to overcome the limitations of such(More)
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