Implementation and Evaluation of a Mobile Tetherless VoIP/PSTN Gateway
Source: Stony Brook University
This paper talks about the implementation and evaluation of a mobile tether-less VoIP/PSTN gateway. The internet, which is the IP-based packet-switched network, and Public-circuit Switched Telephone Networks (PSTN) are brought together by a voice-over-IP (VoIP) gateway. A telephony card, which happens to be the key building block of a VoIP gateway, interfaces with the PSTN and converts signals from the PSTN to bits that can be manipulated by a computer and vice versa. Most of the commercially available telephony cards are designed to work only with wired PSTN lines. This means that almost all existing VoIP gateways are tethered. This limits their ability to support the kind of mobility enabled by modern wireless communications technology. This paper presents a mobile VoIP gateway called WGate that is designed specifically to bridge wireless VoIP clients and cellular phones. This makes it possible to easily deploy WGate on demand in particular geographical locations. The paper describes its implementation and also evaluates its functioning in detail. This useful VoIP gateway called WGate can turn a set of commodity blue tooth capable cell phones into a multi-port telephony card. This is done by using a Bluetooth link as a wireless backplane by exploiting the Hands-Free profile of the Bluetooth protocol stack.