# Analysis of LTE-M Adjacent Channel Interference in Rail Transit
## 4 Interference Analysis of LTE-M Ground System
### Simulation Results  
This paper uses the snapshot method to sample the system running process. After each snapshot, the positions of the terminals are changed randomly, and the same simulation algorithm is executed as the last time, and, finally, the sampling results at all snapshot moments are statistically analyzed. MATLAB software is utilized to generate simulation results, and the simulation parameters for the proposed system are as follows (Table 10). In order to explore the factors affecting system performance, the required ACIR values are obtained by changing different simulation parameters. When the number of interfering users is 50 and the power control parameter Set 1 is selected, the offset between base stations is changed, and the simulation result of throughput loss is shown in Figure 11. When the offset between base stations is D, the throughput loss changes significantly under different interfering users and different power control parameters as shown in Figure 12. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Parameter** & **Downlink** & **Uplink** \\ \hline \(\alpha\) & 0.6 & 0.4 \\ \(\text{SINR}_{min}/\text{dB}\) & \(-\)10 & \(-\)10 \\ \(\text{TP}_{max}/\text{bps}\cdot\text{Hz}^{-1}\) & 4.4 & 2.0 \\ \(\text{SINR}_{max}/\text{dB}\) & 22.05 & 14.91 \\ \hline \hline \end{tabular}
\end{table} 
Table 9: LTE link performance baseline. Figure 11: LTE-M throughput loss under different location offset between base stations and ACIR: (**a**) UE-BS, (**b**) UE-TE. \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Parameters**} & \multicolumn{2}{c}{**LTE FDD**} & \multicolumn{2}{c}{**LTE-M**} \\ \cline{2-4}  & **Uplink** & **Downlink** & **Uplink** & **Downlink** \\ \hline \multirow{2}{*}{Cell Structure} & Macrocell structure, 750 m distance between & \multirow{2}{*}{Linear topology} \\  & base stations & & \\ \hline Carrier BW & 10 MHz & 10 MHz \\ \hline RB Size & \multirow{2}{*}{180 KHz} & 180 KHz \\ \hline User distribution & Uniformly distribute at random based on area & Nearby random distribution along the track \\ \hline User/Train Number & 50,100 & 1 \\ \hline Thermal noise density & \(-174\) dBm/Hz & \(-174\) dBm/Hz \\ \hline Noise coefficient & 5 dB & 9 dB & 5 dB & 9 dB \\ \hline Antenna Height & 6 m & 1.5 m & 5 m & 2.5 m \\ \hline Receiving Antenna Gain & 15 dBi & 0 dBi & 15 dBi & 0 dBi \\ \hline Transmitting Antenna Gain & 0 dBi & 15 dBi & 0 dBi & 15 dBi \\ \hline Maximum/Minimum & \multirow{2}{*}{23 dBm/\(-\)30 dBm} & 43 dBm & 33 dBm/\(-\)30 dBm & 46 dBm \\ \hline \hline \end{tabular}
\end{table} 
Table 10: Simulation parameters of the proposed system. Figure 12: LTE-M throughput loss under different number of us ers, ACIR, and power control parameter sets: (**a**) UE-BS, (**b**) UE-TE. It can be seen from the simulation results that when the offset \(D\) between base stations is constant, the throughput loss of LTE-M BS and TE decreases with the increase in ACIR. When ACIR is fixed for UE interfering BS, the higher the offset between BS, the greater the throughput loss of BS. Due to the same power control parameters, the distance between the edge user of the LTE FDD system and the LTE-M BS decreases as the offset increases, resulting in increased interference to the LTE-M BS. The outcome is the opposite for UE interfering TE; due to the randomness of the UE distribution, there is no noticeable difference between the curves, and when the ACIR is more than 35 dB, the throughput loss of the LTE-M system is below the 5% threshold. As a result, LTE FDD UE has negligible impact on LTE-M TE. Table 11 shows the required ACIR values to keep the average relative throughput loss below 5% when the distance between the systems is 0, 0.5 \(R\), and \(R\). The simulation results show that when the number of users and ACIR are fixed, the throughput loss of Set 1 is higher than that of Set 2.