# Burst Channel Error Reduction Based on Interleaving for Efficient High-Speed Wireless Communication
## 5 Simulation Results
### BER Performance Evaluation over Different Stanford University Interim (SUI) Channel Models  
In this experiment, the BER performances of FFT-OFDM and DWT (Haar)-OFDM systems with and without helical and FRF interleavers are evaluated over different SUI channel models in the presence of AWGN. The SUI channel models considered are SUI-2, SUI-3, and SUI-6 [35]. The multipath profiles of the used SUI channels are summarized in Table 3.  
Figures 10-12 show the BER vs. \(E_{b}\)/\(N_{0}\) for the helical (FFT/DWT)-OFDM and FRF (FFT/DWT)-OFDM systems compared with the conventional (FFT/DWT)-OFDM systems over the SUI-2, SUI-3, and SUI-6 channel models. As seen in Figures 10-12, the DWT-OFDM achieves a better performance than that of the FFT-OFDM for the same reasons described above. In addition, the proposed (FFT/DWT)-OFDM systems outperform the traditional (FFT/DWT)-OFDM systems. In addition, helical and FRF interleaving achieve the best results with the DWT-OFDM system. Therefore, we can say that the proposed systems have a high immunity to burst errors. The figures also show that the proposed FFT-OFDM system with FRF interleaving provides a better BER performance than that with the helical interleaving, but the proposed DWT-OFDM systems with FRF and helical interleavers provide approximately the same BER performance for the same reasons described above. This indicates that the FRF interleaver is more suitable for the FFT-OFDM system due to its strong randomization capability that leads to a good BER. From the previous results obtained from Figures 10-12, for example, at \(E_{b}\)/\(N_{0}\) = 30 dB, the proposed FFT-OFDM system with an FRF interleaver achieves BERs of about 1.22 \(\times\) 10\({}^{-6}\), 9.78 \(\times\) 10\({}^{-7}\), and 1.25\(\times\)10\({}^{-6}\) for the SUI-2, SUI-3, and SUI-6 channel models, respectively. On the other hand, the BER values achieved by the FFT-OFDM system with the helical interleaver are 4.44 \(\times\) 10\({}^{-6}\), 2.11 \(\times\) 10\({}^{-6}\), and 4.67 \(\times\) 10\({}^{-6}\), while they are 0.1333 \(\times\) 10\({}^{-3}\), 0.2354 \(\times\) 10\({}^{-3}\), and 0.2562 \(\times\) 10\({}^{-3}\) for the conventional FFT-OFDM system over the SUI-2, SUI-3, and SUI-6 channel models, respectively. This means that the proposed FRF interleaver can improve the BER performance compared to those of the FFT-OFDM system with the helical interleaver and the conventional FFT-OFDM.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Model**} & \multicolumn{2}{c}{**Delay**} & \multicolumn{2}{c}{**\(L\) (No. of Taps) = 3**} & \multirow{2}{*}{**Units**} \\ \cline{2-3} \cline{5-6}  & **Gain** & & & & \\ \hline \multirow{2}{*}{**SUI-2**} & \multirow{2}{*}{**SUI-2**} & 0 & 0.4 & 1.1 & \(\upmu\)s \\ \cline{3-6}  & & 0 & \(-\)12 & \(-\)15 & dB \\ \hline \multirow{2}{*}{**SUI-3**} & 0 & 0.4 & 0.9 & \(\upmu\)s \\ \cline{3-6}  & 0 & \(-\)5 & \(-\)10 & dB \\ \hline \multirow{2}{*}{**SUI-6**} & 0 & 14 & 20 & \(\upmu\)s \\ \cline{3-6}  & 0 & \(-\)10 & \(-\)14 & dB \\ \hline \hline \end{tabular}
\end{table}
Table 3: The multipath profiles of the used SUI channels.