# Link and System-Level NOMA Simulator: The Reproducibility of Research
## 5 Verification of the NOMA Simulator
### Exemplary Simulated Results
#### 5.1.5 Inter-Cell Interference  
Intercell interference is the interference between different cells. It is considered an important challenge that users face in multi-cell scenarios. For our system-level simulations, we considered 7-cell and 19-cell scenarios with the wrap-around effect; therefore, concerning the center cell, interference comes from other neighboring cells either in the first or second tier. The strategy adopted to calculate the intercell interference is based on the distance. As a result, in our simulations, the distance between the adjacent BS and the users connected to the cell center BS was used to assess interference. The relation between the average received power and distance from the BS of neighboring cells to the center cell can be expressed as  
\[P_{r}\propto d^{-\gamma} \tag{13}\]  
where \(Y\) is the path loss exponent whose value is taken as 3.5 for the urban cellular area. Intercell interference affects both NEU and FEU. However, FEU is close to the boundary of the cell and at a small distance from the neighboring BSs, it receives more interference than the NEU, which is closer to the center BS and further away from the neighboring BSs. However, \(P_{r}\) is the path loss exponent, which depends on the transmission environment, and d corresponds to the distance between the users and the BS. Thus, by calculating the distances between the BS and the users, the received power acting a source of interference from other cells can be calculated. This concept is illustrated in Figure 14. A small circle in each hexagon represents the location of BS in each cell, whereas the black dots depict the location of users in each cell. Each BS transmits power, which acts as a source of inter-cell interference for the users in the neighboring cells. The system parameters for this particular scenario, represented in Figure 14, are given in Tables 2 and 3. The BER performance of the system in the presence of inter-cell interference for 7-cell scenarios with two and three  
Figure 13: Capacity performance of the NOMA system for more than 2 EU (3 EU).  
users is presented in Figures 15 and 16, respectively. In Figure 15, it can be seen that in the presence of inter-cell interference, BER is getting worse for both NEU and FEU with \(E_{b}/N_{o}\) decreases by 2 dB and 2.5 dB for a BER of \(10^{-3}\). Similarly, Figure 16 shows that the presence of inter-cell interference affecting the BER for all users with \(E_{b}/N_{o}\) lowering by 2.1 dB, 2.4 dB and 2.2 dB for a BER of \(10^{-3}\). The level of interference can be calculated using Equation (14). Thus, the overall sum-rate of MC-NOMA is affected by interference and is given as:  
\[R_{sum}=\log_{2}\Biggl{(}1+\frac{P_{NEU}|h_{NEU}|^{2}}{\eta_{1}+I_{n}}\Biggr{)} +\log_{2}\Biggl{(}1+\frac{P_{FEU}|h_{FEU}|^{2}}{P_{NEU}|h_{FEU}|^{2}+\eta_{2}+ I_{n}}\Biggr{)} \tag{14}\]  
\[R_{sum_{3}}=\log_{2}\Biggl{(}1+\frac{P_{NEU}|h_{NEU}|^{2}}{\eta_{1}+I_{n}} \Biggr{)}+\log_{2}\Biggl{(}1+\frac{P_{IEU}|h_{IEU}|^{2}}{P_{NEU}|h_{IEU}|^{2}+ \eta_{2}+I_{n}}\Biggr{)}+\log_{2}\Biggl{(}1+\frac{P_{FEU}|h_{FEU}|^{2}}{P_{ NEU}|h_{FEU}|^{2}+\eta_{2}+I_{n}}\Biggr{)} \tag{15}\]  
where, \(I_{n}\) is the intercell interference.  
Figure 15: BER performance comparison of perfect SIC for NEU and FEU in the presence of intercell interference.  
\begin{table}
\begin{tabular}{c c c} \hline
**Cell No.** & \
\begin{tabular}{c} **Distance between Users from Their** \\ **Corresponding BS in Each Cell** \\ \end{tabular} &
\begin{tabular}{c} **Distance between Neighboring** \\ **Cell Users and Center Cell BS** \\ \end{tabular} \\ \hline
1 & FEU: 450 m, NEU: 50 m & NEU: 1050 m, FEU: 950 m \\
2 & FEU: 400 m, NEU: 100 m & NEU: 1000 m, FEU: 700 m \\
3 & FEU: 350 m, NEU: 150 m & NEU: 950 m, FEU: 750 m \\
4 & FEU: 450 m, NEU: 50 m & NEU: 950 m, FEU: 1100 m \\
5 & FEU: 400 m, NEU: 100 m & NEU: 950 m, FEU: 1300 m \\
6 & FEU: 350 m, NEU: 50 m & NEU: 1050 m, FEU: 1250 m \\ \hline \end{tabular}
\end{table}
Table 3: System Parameters for 7-cell Scenario.