Theoretical and Experimental Approach for the Design of an Optical Wireless Physical Activity Monitoring System

Abstract

We propose in this paper, an optical wireless communicating accelerometer-based system for physical activity level monitoring. Optical wireless technology presents the advantage to be secure regarding electromagnetic interference, low-cost and easy to deploy. Considering a mobile patient, we theoretically investigate the performance in terms of packet failure in a specific environment. We study in particular the impact of the optical source directivity, the emitted optical power, the position of the motion sensor device on the body, and the number of optical receivers fixed on the room ceiling. The theoretical results are compared with experimental measurements for several configurations using a custom-made wearable communicating device. This permits validating optical wireless technology efficiency for physical activity monitoring and showing that it exists an optimal value of half-power angle of the transmitter to insure the optical wireless performance whatever the coverage and the height of the device over the body are. At last, we illustrate the trade-off between emitted power and number of active receivers.