## 3 Results
### Power Consumption  
Continuous healthcare monitoring is the function of total power consumption and is a critic aspect of designing wearables [67]. Currently, a lithium-ion battery of capacity \(C_{\text{bat}}=230\) mAh powers on the prototype. The total average current and the power consumption is approximately \(I_{\text{ave}}=18.35\) mA and \(P_{\text{ave}}=51.38\) mW, respectively. The main current consumers are (Table 7):  
* _Basic functionalities_ (A), which refer to all hardware and software preparation while powering on. This includes boot-loading, all interfaces and sensors' initialization, (not necessarily configuration), hardware check, and so forth. It also includes powering the BLE connection;
* _Internal memory_ (B);
* _Behavioral sensors_ (C), which are collecting data continuously and start measuring with powering on the device;
* _Physiological sensors_, that is, the skin temperature (D) and the PPG (E);
* _Environmental sensors_, gas (F), loudness (G), and UV sensors (H) that consume in average 2.23 mA, 4.013 mA, and 0.46 mA, respectively. In addition, we have the air condition sensors such as pressure, temperature, and humidity (I); and
* _Display_ (K), which dissipates slightly less than 2.7 mA.  
We measure the total power consumption and the battery operation time according to strict measurement of current consumption. To construct the power consumption profile we have identified the major sources of consumption. We have also included the current leakage and minor resources consumption in the final calculation by inserting basic functionality (A) profile. The battery is connected to the prototype via a 100 Ohm resistor, and consequently is monitored on the oscilloscope. The current consumption is measured in three specific conditions of activation, standby, and deep sleep and is applied to each sensor and component, if applicable (see Equations (1) and (2)).  
\[I_{ave}=\sum_{i=0}^{2}\frac{I_{i}\times t_{i}}{t_{total}}, \tag{1}\]  
where \(i\) indicates the status of sensor in activation, standby, and deep sleep modes.  
\[P_{ave}=\sum_{i=0}^{2}\frac{I_{i}\times V_{supply}\times t_{i}}{t_{total}}. \tag{2}\]  
The sensors and components are activated one after another via embedded code to assure the functionality of the sensors. In addition, the minor resources also which are detected are included in the  
\begin{table}
\begin{tabular}{l r r} \hline \hline
**Sensors/Components** & \(I_{\text{ave}}\) **[mA]** & \(P_{\text{ave}}\) **[mW]** \\ \hline A + C & 4.425 & 12.39 \\ I & 0.12 & 0.336 \\ B + K & 2.7 & 7.56 \\ B + F (\(NO_{2}\)) & 2.23 & 6.24 \\ B + G & 4.013 & 11.23 \\ B + H & 0.463 & 1.29 \\ B + D & 0.193 & 0.54 \\ B + E & 2.86 & 8.01 \\ \hline Total & 17.0 & 47.6 \\ Total + BLE & 18.35 & 51.38 \\ \hline \hline \end{tabular}
\end{table}
Table 7: Estimated average of current and power consumption.  
measurement. Activation of a sensor is followed with recognition of sensor status (activation, standby, and deep sleep). The period of each mode will influence the final calculation. In general, the sensors with high sampling rate (e.g., behavioral) will not be subjected to deep sleep mode. The current power consumption is subtracted from the previous recorded measurement and the consumption of the particular sensor/component is specified. \(I_{max}\) and \(I_{min}\) indicate the sampling and deep sleep/standby mode, respectively. When BLE is connected, the internal memory is excluded from the total power consumption but an additional current of 1.35 mA is imposed. This yields for the total battery runtime:  
\[T=\frac{C_{\text{bat}}}{I_{\text{ave}}}=\frac{230\text{ m}\text{Ah}}{18.35\text{ m}\text{A}}=12.53\text{ h}.\]  
Table 8 shows the minimum and maximum peaks recorded without considering the duty cycle. Comparison of maximum and average current consumption of PPG, significantly indicates the signal cycle activation (time interval: 15 s). The average current and power consumption have been calculated according to deep sleep, standby and activation modes.