## 5 Simulation and Results
### Simulation Results and Analysis for Urban Traffic Scenarios  
This section will simulate the user demand- and scenario-adaptive OFDM-IM method in urban traffic scenarios, providing system performance graphs for various values of the index modulation parameters (N, K, M) in these scenarios. The simulation parameters are shown in Table 5. The simulations are conducted following the specifications outlined in the 802.11 p standard [35]. The corresponding subcarrier spacing meets the requirements of vehicular communication scenarios, providing good robustness against Doppler shift and multipath effects. The fuzzy logic simulation input dataset includes the spectral efficiency, bit error rate, and energy consumption values for different combinations of (N, K, M) under this channel state scenario. The output is the energy efficiency evaluation Y value. The SNR selection is primarily based on the minimum SNR chosen in Section 3. All possible points represent results from arbitrary combinations of different \((N,K,M)\), \(N\leq K\), totaling \((A_{4}^{4}A_{4}^{4}+A_{8}^{8}A_{4}^{4}+A_{12}^{12}A_{4}^{4}+A_{16}^{16}A_{4}^{4})\) groups. To reduce the computational complexity, combinations with similar results are filtered out, and only one group is analyzed and plotted if it does not significantly affect the overall trend or conclusion. Additionally, for N values of 12 and 16, the discontinuous sampling of the K values can be performed to select the best-performing combinations (N, K, M). Considering the values of the three decisive factors in maximizing the energy efficiency as fuzzy logic inputs, the spectral efficiency, bit error rate, and energy consumption at a 20 dB SNR are entered into the system with predefined membership functions and fuzzy rules. Finally, based on the defuzzified logical output with the maximum value, the condition of energy efficiency maximization is determined, identifying the optimal index parameter point with high spectral efficiency, a low system bit error rate, and low energy consumption. Figure 14 illustrates the system performance for different (N, K, M) values under urban traffic scenarios based on the simulation results. \begin{table}
\begin{tabular}{c c} \hline \hline
**Simulation Parameter** & **Configured Value** \\ \hline Rician Factor R & 10 dB \\ \hline Reflection Coefficient \(\mu\) & 0.5 \\ \hline Number of Subcarriers per Subblock N & 4/8/12/16 \\ \hline Number of Active Subcarriers K & 1-N \\ \hline Modulation Order of Constellation M & 2/4/8/16 \\ \hline SNR Value & 20 dB \\ \hline Total OFDM Subcarriers U & 64 \\ \hline Number of Subblocks G & U/N \\ \hline Bandwidth & 10 MHz \\ \hline Length of the CP \(N_{\text{CP}}\) & 16 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Simulation parameters for urban traffic scenarios. Figure 14a shows that, under the condition of N = 4 subcarriers, the energy efficiency Y value is maximized at (N, K, M) = (4, 2, 4). Compared to the conventional OFDM point (N, K, M) = (4, 4, 4), the OFDM-IM system at this optimal point achieves 75% of the spectral efficiency of traditional OFDM but has a lower bit error rate and consumes only 50% of the energy, offering superior overall performance. Additionally, compared to the second-best point (N, K, M) = (4, 3, 4), although the spectral efficiency is slightly lower, both the bit error rate and energy consumption improve significantly. The figure also indicates that, as the modulation order M increases, the spectral efficiency gradually improves, but the bit error rate also rises because a higher constellation modulation order M leads to a larger mapping sequence, reducing the minimum Euclidean distance between the symbols on the constellation diagram. Figure 14b illustrates that, with N = 8 subcarriers, the highest energy efficiency Y value is achieved at (N, K, M) = (8, 4, 4).