Experiments in Adaptive Power Control for Truly Wearable Biomedical Sensor Devices

Emerging body-wearable devices for continuous health monitoring are severely energy constrained and yet re-quired to offer high communication reliability under fluctu-ating channel conditions. Such devices require very careful management of their energy resources in order to prolong their lifetime. In our earlier work we had proposed dynamic power control as a means of saving precious energy in off-the-shelf sensor devices. In this work we experiment with a real body-wearable device to assess the power savings pos-sible in a realistic setting. We quantify the power consump-tion against the packet loss and establish the feasibility of dynamic power control for saving energy in a truly-body-wearable setting. 1

Algorithms for Transmission Power Control in Biomedical Wireless Sensor Networks

Abstract—Wireless sensor networks are increasingly being used for continuous monitoring of patients with chronic health conditions such as diabetes and heart problems. As biomedical sensor nodes become more wearable, their battery sizes dimin-ish, necessitating very careful energy management. This paper proposes feedback-based closed-loop algorithms for dynamically adjusting radio transmit power in body-worn devices, and evalu-ates their performance in terms of energy savings and reliability as the data periodicity and feedback time-scales vary. Using experimental trace data from body worn devices, we first show that the performance of dynamic power control is adversely affected at long data periods. Next for a given data period we show that modifying the transmit power at too long time-scales (around a minute) reduces the efficacy of dynamic power control, while too short a time-scale (few seconds or less) incurs a high feedback signaling overhead. We therefore advocate an intermediate range of time-scales (when permitted by the data periodicity), typically in the few tens of seconds, at which the control algorithms should adapt transmit power in order to achieve maximal energy savings in body-worn sensor devices used for medical monitoring. I