Integrating Presence and Location Services using SIP

In semi-nomadic professions such as medicine, practitioners move through office buildings carrying personal computing and communication devices. These practitioners make use of fixed computing and communication resources in the rooms they visit. Organizations have strong financial incentives to help their mobile professionals find each other, communicate effectively, and make efficient use of the infrastructure. The challenge is to provide the desired functionality in a cost-effective manner without requiring special hardware on the mobile devices. Our solution consists of a standards-based voice, video, and instant messaging communication system integrated with a location tracking system. Our location tracking system is a low-cost scanning network that monitors the wireless network transmissions from the mobile devices and uses that information to identify and track the mobile clients. This paper describes (1) the architecture, implementation, and performance tradeoffs for a low-cost sensor network for live tracking of 802.11 wireless clients in an office building, and (2) the integration of the location tracking data with a standards-based SIP voice/video/presence communication infrastructure. This architecture requires no special client hardware or software. This system has been deployed and tested both in the laboratory and at two conferences.