Chapter One Power Management in Body Area Networks for Healthcare Applications

For an increasing number of people living with chronic medical conditions, wearable wire-less sensor devices can provide non-intrusive yet continuous physiological monitoring al-lowing effective clinical management without compromising quality of life. Truly non-intrusive sensor devices will have light weight and small form factor, placing fundamen-tal constraints on the available energy, which necessitates very careful energy management at all layers. This chapter investigates the opportunities and challenges in the use of dy-namic radio transmit power control for prolonging the lifetime of such energy constrained body-wearable sensor devices. We first present extensive empirical evidence that the wireless link quality can change rapidly in body area networks, and a fixed transmit power results in either wasted energy (when the link is good) or low reliability (when the link is bad). We quantify the potential gains of dynamic power control in body-worn devices by benchmarking off-line the energy savings achievable for a given level of reliability. We then propose a class of schemes feasi-ble for practical implementation that adapt transmit power in real-time based on feedback information from the receiver. We profile their performance against the off-line benchmark, and provide guidelines on how the parameters can be tuned to achieve the desired trade-off between energy savings and reliability within the chosen operating environment. Finally, we implement and profile our scheme on aMicaZmote based platform, and also report pre-liminary results from the ultra-low-power integrated healthcare monitoring platformwe are developing at Toumaz Technology. Our work sets the stage for a holistic approach to power management, incorporating innovations across all layers of body area network design. 1.1