## 3 Results
### Power Consumption Measurement Strategy  
We have established an experimental test bench comprising a Keysight(r) MSOX3054A Mixed Signal oscilloscope, a Rigol(r) DM3058E multimeter, and a GW Instek(r) GPS4303 power supply unit (PSU). This setup enables us to precisely measure the power consumption of the three sensor nodes. We provide the sensor nodes with a constant DC voltage supply within the recommended range of 2-3.5 V from the PSU. To calculate power consumption accurately, we monitor the RMS value of the variable DC current that characterizes the sensor node's activity. Our multimeter boasts five-and-a-half digits of resolution, making it capable of measuring currents in the nA range. Additionally, we employ the oscilloscope to visually analyze the current signal during broadcasting. To ensure precision and repeatability, we run the system for an extended period, collecting a sufficient number of samples for accurate measurements. Given the ultra-low-power nature of our electronics, and for enhanced accuracy and repeatability, we propose conducting these tests inside a shielded brass-based enclosure, as shown in Figure 7. This enclosure helps eliminate the influence of external RF disturbances on our measurements. Our systems exhibit a current consumption profile comprising both AC and DC components. To accurately capture this, we employ a two-fold approach for each measurement. First, we record readings in AC mode to isolate and exclude all DC components. Then, conversely, we record readings in DC mode. By applying the formulas detailed in Equation (1), we can calculate the total I  
Figure 7: Overview of the test board used to connect different MCU platforms where only the tested MCU is connected during the characterization (**a**), and the designed shielding box used during the experimental test to omit RF disturbance from external environment (**b**). the combined electrical current consumption of the system. This approach allows us to accurately account for both AC and DC components in our measurements [46]:  
\[I_{RMS}=\sqrt{I_{AC}^{2}+I_{DC}^{2}}. \tag{1}\]  
To address potential inaccuracies arising from the variable duration of our nodes' cyclic operation, ranging from 5 s to 10 min, we have divided the measurement into two procedures. The first part focuses on the active region, while the second part concentrates on the sleep mode. These two segments are then combined to yield final calculations. Given that each of our sensing platforms maintains an active broadcast duration of around 2 s, we programmed each node to perform real-time readings, equating to one broadcast every 2 s (1 Broadcast/2 s). We acquired RMS current values over a two-minute interval, encompassing 60 broadcast packets. Averaging these RMS current samples allows us to determine the actual steady-state current consumption during the active phase. We then executed the same measurement procedure to ascertain the sleep current. By applying the formula in Equation (2), we can subsequently compute the system's power consumption. This approach helps us address variations in operation duration and ensures accurate power consumption calculations [46]. \[P_{RMS}=\frac{\left(2\times I_{RMS}^{active}\right)+\left[I_{RMS}^{sleep} \times\left(t_{cycle}-2\right)\right]}{t_{cycle}}\times V_{DC}\, \tag{2}\]  
where \(P_{RMS}\) is the total RMS power consumption, \(I_{RMS}^{active}\) is the RMS current value measured in the active broadcast region, \(I_{RMS}^{sleep}\) is the RMS current value measured during the inactive sleep region, \(t_{cycle}\) is the total broadcast time interval or system cycle time, and \(V_{DC}\) is the DC voltage supply. Table 3 provides a summary of power consumption data for our sensor nodes, utilizing different MCU platforms. These measurements were conducted at 2.5 V and 3.0 V DC voltage supplies, and various broadcast intervals of 5, 15, 30, 60, 120, 300, and 600 s. Additionally, we determined the equivalent resistances exhibited by the nodes at different power consumptions.