# Ultra-Low-Power Wide Range Backscatter Communication Using Cellular Generated Carrier +
## 5 Results and Discussion  
This section discusses the acquired simulation results that are based on the simulation setup, network layout, and parameters presented in Section 4. The results for outdoor and indoor cases are presented separately. The first performance metric considered is the forward link received power at the backscatter device. Figure 5(a),b show the cumulative distributive functions (CDFs) of the received power at four different frequencies for the outdoor and indoor BDs. In the case of indoor results, the solid and dashed lines represent the cases with the low and high building penetration loss model, respectively. Figure 5(a) shows that, in the considered environment and a cellular network layout, the received power at the outdoor BD is significantly high, even at 900 MHz. In an outdoor environment, the mean received power levels are around -33 dBm, -42 dBm, -45.5 dBm, and -48 dBm at 200 MHz, 500 MHz, 700 MHz, and 900 MHz, respectively. It shows that there is almost 9 dB difference in the received power at the BD between the 200 MHz and 500 MHz frequency of operation, and the difference in received power becomes smaller while migrating from 500 MHz to 700 MHz. Whereas, the indoor BDs received a clearly lower power when compared with outdoor BDs due to additional building penetration loss for indoor BDs. Moreover, it can be seen from Figure 5(b) that the high BPL model offers around 6-6.5 dB higher loss value as compared with the low BPL model, and the mean received powers at the BD in indoor environment using high BPL are around -44.5 dBm, -54.5 dBm, -58.5 dBm, and -61 dBm at 200 MHz, 500 MHz, 700 MHz, and 900 MHz, respectively. In this article, we have only considered a LoRa backscatter device for energy harvesting. Furthermore, it is shown in the reference [57] that there are numerous factors that affect the energy harvesting efficiency of the BD. Therein, the energy harvesting efficiency was also shown as a function of the incident RF power. Accordingly, we have computed the required time for harvesting the energy with different energy harvesting efficiencies, starting from 40% to 80%. \begin{table}
\begin{tabular}{l c c c c} \hline \hline
**Technology** & **Sensitivity** & **Max Data Rate** & **Power Consumption** & **Reference** \\ \hline BLE 5 & -97 dBm & 2 Mbps & 20 mW & [16] \\ NB-IoT & -141 dBm & 204.8 kbps & 543 mW & [14] \\ LoRa backscatter & -149 dBm & 37.5 kbps & 9.25 uW & [55] \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Sensitivity level and maximum supported data rates for different IoT technologies. \begin{table}
\begin{tabular}{l c c} \hline \hline
**Parameters** & **Unit** & **Value** \\ \hline Frequency & MHz & 200/500/700/900 \\ Tx Power & dBm & 43 \\ Antenna height & m & 30 \\ Max Tx antenna gain & dBi & 17.7 \\ BD antenna gain & dBi & 0 \\ Rx antenna gain & dBi & 0 \\ Fast fading margin (Forward) & dB & 10 \\ Fast fading margin (Backscatter) & dB & 0 \\ Slow fading margin (Forward) & dB & 7 \\ Slow fading margin (Backscatter) & dB & variable \\ Polarization mismatch loss & dB & 3 \\ Modulation loss at BD & dB & 6 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: General simulation parameters. Figure 7 shows the CDFs for the time that is required for harvesting the energy from the incoming RF signal from the transmitter at the outdoor LoRa backscatter device, while considering different energy harvest efficiencies and frequencies. Figure 7a shows that, for the considered simulation scenario at 200 MHz frequency of operation, the mean time that is required for harvesting the energy with 40% and 80% energy harvesting efficiency is around 86 s and 43 s, respectively, which seems viable and practical for BDs that need to send periodically small amount of data. However, in Figure 7b, the time that is required for LoRa BD at 500 MHz with 40% and 80% energy harvesting efficiency is around 880 s and 440 s, respectively, which is considerably high.