Related Work

The closest effort related to our work is PSTN to Internet Interworking (PINT) [PET00]. PINT describes an architecture and protocol that is a mirror image of our work. Whereas our work aims to transport discrete events from the PSTN to the Internet for service execution on the Internet, PINT transports service requests from the Internet to the PSTN for service execution in the PSTN. Thus, clicking a link on a Web page (Internet) would cause a service request to travel to the PSTN, which would set up a call between two parties. This allowed such services as the following:

Click-to-Dial: While browsing through a company's Web site, clicking on a Web link causes the PSTN to make a call between the Web user and a customer service representative of the company. Request-to-Fax: Clicking on a Web link causes the PSTN to send a fax to a certain destination. As an example, a restaurant's Web site may contain a link that, when pressed, transmits a facsimile of the menu.

Request-to-Hear-Content: Clicking on a Web link causes the PSTN to call a certain number and arrange for some content to be spoken out.

Berkeley's ICEBERG project [WAN00] integrates telephony and data services spanning diverse access networks. Their approach is expansive because their architecture maintains an overlay network consisting of different geographic ICEBERG points of presence (iPOP) and many ICEBERG access points to isolate the access network from the overlay network. The iPOPs are coordinated by a centralized clearinghouse that serves as a bandwidth broker and accountant (loosely akin to our EM, although unlike ICEBERG, the EM does not perform bandwidth brokering). Our approach, by contrast, is extremely lightweight and follows the service mantra of the Internet, whereby the core network is used simply as transport and services are provided at the edges. In a sense, the entire PSTN is abstracted as a UA generating and sending events to another UA that then executes the services.

Weinstein [WEI02] and Buddhikot et al. [BUD03] outline how wireless local area networks (W-LANs) complement rather than compete with cellular mobile systems. However, they view this work from a data perspective, i.e., providing data connections in the cellular mobile system with a guaranteed quality of service. Buddhikot et al.'s work clusters around allowing an IEEE 802.11 hotspot operator to access the profiles and policies of a 3G user when the latter roams into the former's network. They do not discuss the architecture we have proposed here to transport discrete events from one network to the other for service execution.

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