Tom Janiszewski

Seamless SIP-based VoIP in disparate wireless systems and networks

In the emerging data networks, session initiation protocol (SIP)-based voice over IP (VoIP) is gaining wide-scale acceptance as a means of transporting voice over the packet data networks. With the emergence of interoperability between various third-generation (3G) cellular technologies such as 1xEV, 1xEV-DO, 1xEV-DV, and the Universal Mobile Telecommunications System (UMTS) on one hand and wireless LAN (WLAN) technologies such as 802.11a/b/g, HiperLAN/2, and Bluetooth∗ on the other, multimedia applications would have to interoperate seamlessly among several air interfaces. Mobile IP, a layer 3 protocol, maintains the data session across heterogeneous air interfaces but does not guarantee minimal or no packet loss when handing over a mobile node from one air interface to another. This paper first discusses a network architecture that supports seamless interoperability between 3G and WLAN and proposes autonomous layer 2 enhancements at the client side to support SIP-based multimedia applications in general and voice applications in particular. Finally, it discusses some other network issues that pose a challenge to providing VoIP in commercial networks in general, such as using SIP with network address translation (NAT) over mobile IP, and it specifically addresses the problem of performing VoIP in CDMA2000∗ 1XRTT.