EACg Research Summary - Todd William Polk

Wireless sensor networks (WSNs) are a rapidly growing research and commercial development area. The potential applications for WSNs are limitless; however there are several issues to overcome in order to make them truly pervasive. One area where WSNs will be of extraordinary benefit is in the medical industry in general and in telemedicine in particular. Telemedicine involves the use of telecommunications technology to provide increased access to medical information for both patients and health care providers. Townsend, et al. discuss several of recent developments in this area in [1]. The primary issues facing WSN usage in telemedicine are infrastructure installation, power generation, security concerns, device mobility and most importantly, acceptance by medical professionals. The ability to overcome these issues would lead to widespread adoption of WSNs in the medical arena. This would have several benefits to both healthcare practitioners and their patients. The increase in connectivity and information flow will allow practitioners to more closely monitor their patients in real time. Automated collection, correlation and display of this information will allow doctors to cover more patients without a corresponding reduction in the level of care. With the overall aging of the population, the ability to effectively handle more patients will become paramount to the medical profession. Additionally, allowing information access to patients and their family will greatly improve their knowledge and comfort levels. Reducing the initial costs associated with the installation of a WSN infrastructure will lower the entry barriers and allow rapid deployment on a wider scale. Developing alternative power sources for these wireless nodes will substantially reduce the recurring costs associated with the operation of a WSN, and allow near permanent operation. Security is also a major concern, as wireless signals can be easily intercepted by any nearby party. It is critical to insure that the transmitted data is secure. Device mobility must be assumed to be an inherent feature of any WSN. The freedom from wires while still maintaining the ability to track and monitor patients is most desirable. And finally, all of the above issues, once solved or eliminated, will increase acceptance among medical practitioners as they come to realize the benefits that WSNs can provide. Lorincz, et al. in [2] show an excellent conceptual system for use in emergency response situations.

Figure 1: Remote Monitoring Concept

I am currently involved in research on 3 of the above listed issues – infrastructure installation, power generation and device mobility. Our research team is focusing on WSNs as they relate to telemedicine applications. Figure 1 shows an idealized view of wireless patient monitoring. All 3 of our research areas are incorporated into this figure. The patient is wearing a mobile device, routing signals through a fixed router infrastructure. The routers must be powered in an energy and cost efficient manner. We have developed a method to allow these nodes to be self powered. Presently, they scavenge energy from fluorescent lights (via solar panels) and use ultracapacitors for energy storage. An intelligent routing algorithm has been written to manage and utilize the scavenged energy and provide 100% on-time for the routers. Later, additional energy scavenging methodologies such as piezoelectric vibration generators, and energy from thermal and acoustic noise will be explored. A prototype of the present router node hardware is shown in Figure below.

Figure 2: Self powered node.

Additionally, we are working to interface various medical instruments to our sensor nodes. Initially, we have connected a commercial blood pressure monitor to one of our Crossbow MICAz nodes. We use the node to initialize and take a blood pressure reading and then forward that reading through a WSN to the base station, thereby completing the system shown in Figure 1.

EACg Publications

1. A. Hande, T. Polk, W. Walker, and D. Bhatia, “Indoor Solar Energy Harvesting for Sensor Network Router Nodes”, submitted to the Journal of Microprocessors and Microsystems -Special Issue on Sensor Systems, Dec. 2006.
2. T. Polk, A. Hande, W. Walker, and D. Bhatia, “A Wireless Sensor Network Protocol for Self-Powered, Energy Scavenged Nodes”, in preparation, to be submitted to the Journal of Computer Communications – Special Issue on Network Coverage and Routing Schemes for Wireless Sensor Networks, Spring 2007.
3. W. Walker, T. Polk, A. Hande, and D. Bhatia, “Remote Blood Pressure Monitoring Using A Wireless Sensor Network”, in preparation, to be submitted to the Sixth Annual Emerging Information Technology Conference, August 2006.

References

[1] K.A. Townsend, J.W. Haslett, T.K.K. Tsang, M.N. El-Gamal and K. Iniewski, "Recent advances and future trends in low power wireless systems for medical applications," Fifth International Workshop on System-on-Chip for Real-Time Applications, pp. 476-481, 2005.

[2] K. Lorincz, D.J. Malan, T.R.F. Fulford-Jones, A. Nawoj, A. Clavel, V. Shnayder, G. Mainland, M. Welsh and S. Moulton, "Sensor networks for emergency response: challenges and opportunities," Pervasive Computing, IEEE, vol. 3, pp. 16-23, 2004.