Integration of Bluetooth HandsFree Sensors into a Wireless Body Area Network Based on Smartphone

Abstract

Generally speaking, invasive methods (such as chest belts) are used to collect data on people physical conditions, limiting the real-time monitoring, useful for example during sport trainings. To overcome the limitations of existent solutions, the external biometric sensors can be placed in a Bluetooth headset and the stream of biometric data transmitted to the smartphone when there is no call. In order to interface the sensors to iOS as well as Android based devices, Bluetooth HandsFree profile, the only widely supported, has been used to transmit the stream of data. The bandwidth available for the data stream is between 20 Hz and 4 kHz, but a Signal to Noise Ratio on the order of 30 dB can be obtained only in the bandwidth between 100 Hz and 1 kHz, as experimentally evaluated. Typically, the biometric sensors have a bandwidth below the 100 Hz, thus they requires a careful signal conditioning. A prototype, using a Photoplethysmographic sensor, has been developed to demonstrate the feasibility of this approach. The stream of real-time data obtained from the sensor are collected and then visualized to the final user, using dedicated applications, for iOs as well as for Android.