Adapting Radio Transmit Power in Wireless Body Area Sensor Networks

Abstract

Emerging body-wearable devices for continuous health monitoring are severely energy constrained and yet required to offer high communication reliability under fluctuating channel conditions. This paper investigates the dynamic adaptation of radio transmit power as a means of addressing this challenge. Our contributions are three-fold: we present empirical evidence that wireless link quality in body area networks changes rapidly when patients move; fixed radio transmit power therefore leads to either high loss (when link quality is bad), or wasted energy (when link quality is good). This motivates dynamic transmit power control, and our second contribution characterises the off-line optimal transmit power control that minimises energy usage subject to lower-bounds on reliability. Though not suited to practical implementation, the optimal gives insight into the feasibility of adaptive power control for body area networks, and provides a benchmark against which practical strategies can be compared. Our third contribution is to develop simple and practical on-line schemes that trade-off reliability for energy savings by changing transmit power based on feedback information from the receiver. Our schemes offer on average 9-25% savings in energy compared to using maximum transmit power, with little sacrifice in reliability, and demonstrate adaptive transmission power control as an effective technique for extending the lifetime of wireless body area sensor networks.

Energy consumption bounds analysis and its applications for grid based wireless sensor networks

“…A complete overview about the modeling, tools, and their applications of wireless networks was provided in Haenggi et al (2009). And a number of schemes (Akan et al, 2009;Bulut and Korpeoglu, 2011;Xiao et al, 2008;Quwaider et al, 2010) have been proposed to minimize energy consumption in wireless sensor networks. The feasibility of passive sensor networks was studied in Akan et al (2009) to provide an environment free of energy constraints; however, such a network would require an external RF resource.…”

Experiments in Adaptive Power Control for Truly Wearable Biomedical Sensor Devices

“…There is thus an inherent delay between sampling the channel and adjusting the transmit power, which limits the performance of practical schemes. In our earlier work [14] we had proposed practical power control schemes for body area devices. In this section we analyze and evaluate the performance of the "aggressive" scheme in the three scenarios under consideration.…”

“…In our earlier work [14] we had proposed dynamic power control as a means of improving the energy performance of body area sensor devices, and validated our proposed algorithms using MicaZ motes. In this work we experiment with the Toumaz Sensium platform and establish the efficacy of dynamic power control for truly-wearable devices which are specifically designed for health monitoring.…”

Algorithms for Transmission Power Control in Biomedical Wireless Sensor Networks

“…Our earlier paper [8] showed that transmit power control can help body-worn devices save energy with minimal impact on reliability. Our algorithm embedded power control information in acknowledgment packets sent in response to each transmission.…”

“…Our earlier work [8] motivated the need for dynamic power control by recording extensive trace data, and proposed a power control algorithm for the sensor node. The traces record the RSSI at the base station when packets are sent by the target at 16 different power levels every second.…”