## 6 Simulation Results
Figures 7-9 illustrate the performance between the INR and mean percentage error (_MPE_) in the various estimation schemes. The _MPE_ is defined as follows:  
\[MPE=E\bigg{[}\frac{\alpha-\widehat{\alpha}}{\alpha}\bigg{]}, \tag{18}\]  
where \(E[\cdot]\) is the expectation operation and \(\alpha,\widehat{\alpha}\) are the estimated and true values, respectively. Figure 8: Performance between MPE of estimating the desired signal power and interference to noise power ratio (INR). Figure 7: Performance between MPE of estimating the channel occupancy rate (COR) and interference to noise power ratio (INR). In these figures, when INR is larger than 12 dB, the performance difference between the proposed estimation and the other estimates is large, and the proposed estimation achieves the best performance. To clarify the performance improvement of the proposed scheme, Figure 10 illustrates the relationship between the INR and packet error rate. Above 12 dB, the packet error rate is greater than 0.1. The impact of the packet error on the estimation increases. In the proposed scheme, even if a packet error occurs, the estimated power of the CCI over a certain threshold is considered highly accurate; therefore, the impact of the packet error can be mitigated. When the INR is larger than 18 dB, the packet error rate becomes 1.0. If CRC confirms all the packets contain errors during the tentative demodulation, the proposed estimation scheme cannot work. The operation region of the proposed estimation scheme is limited to INR 18 dB or smaller. We evaluated the performance of channel selection based on each estimation scheme. The simulation parameters are the same as those in Table 1, and their differences are as follows: There are five channels and one SC system accesses each channel; thus, there are five SC systems. The distance between the transmitter of the SC system and data center  
Figure 10: Performance between the packet error rate in the tentative demodulation of LoRa and the interference to noise power ratio (INR). Figure 9: Performance between MPE of estimating the CCI power and interference to noise power ratio (INR). is a random variable drawn from an independent uniform distribution between 500 and 900 m. Each SC system is an independent random access, where the access probability to the channel, which is equal to the COR of the channel, is modeled by a uniform distribution from 0 to 1.0. Figure 11 illustrates the cumulative distribution function (CDF) of PDR for various channel selection schemes. From this figure, the proposed scheme is better than other conventional schemes, and it is seven points worse than the \"Ideal\". In CDF = 0.1, the PDR of the proposed scheme is 10 and 20 points better than those of \"All packet use\" and \"Only CRC OK\", where the point is defined as the difference of two percentage values. The reason for the better PDR achieved by the proposed scheme is the accurate estimation of signal, noise, and interference power and the COR. From Figures 7-9, the proposed estimation achieves a better performance in terms of the estimation accuracy than \"All packet use\" and \"Only CRC OK\". As we explain in Section 5, the estimation error of power and COR cause the estimation error of the PDR. As a result, \"All packet use\" and \"Only CRC OK\" select the  
To accommodate the access from many sensors, the channel selection is not only based on the COR of the other system, but also the access traffic from the sensors of the own system is necessary. The introduction of such issues to the proposed estimation scheme will be a part of important future work. Conceptualization, O.T., K.A., M.O. and T.F. ; methodology, O.T. ; software, G.K.; validation, G.K. and O.T. ; formal analysis, G.K., O.T. and K.A. ; investigation, G.K. and O.T. ; resources, G.K. and O.T. ; data curation, G.K. and O.T. ; writing--original draft preparation, O.T. ; writing--review and editing, O.T. ; visualization, G.K. and O.T. ; supervision, K.A., M.O. and T.F. ; project administration, O.T. ; funding acquisition, O.T.