# CRCSI: A Generic Block Interleaver for the Next Generation Terrestrial Broadcast Systems
## 4 Simulation Results
### Link-Level Simulation Results  
In this section, the link-level performance of the designed block interleaver is evaluated for fixed and mobility scenarios using Block Error Rate (BLER). Here, the BLER represents the ability of the resource block to resist continuous errors. The BLER performance of the proposed block interleaver for fixed reception under the MPMT scenario is evaluated in the following, where the occupied bandwidth is 10 MHz, and the used channel model is TDL-B with 35 \(\upmu\)s delay spread. Figure 5 shows the performance comparison among the schemes of CRCSI, RCI, TBI and the scheme without interleaving. It is observed that for the 45352 TBS, compared to the no-interleaving scheme, RCI can obtain a performance gain of 1 dB \(\@BLER=10^{-2}\), while for CRCSI, this gain is 1.2 dB; when the TBS is 76208, the gain of RCI can exceed 1.5 dB, while the performance gain of CRCSI is increased to 1.7 dB, which demonstrates the effectiveness of the cross-line interleaving effect. Moreover, the gain of TBI for the two TBS sizes is slightly larger than RCI. Notice that the BLER simulation results match the analysis of the minimum interleaving distance shown in Table 2, where the ascending order of \(d_{min}\) is RCI, TBI and CRCSI. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Method** & **TIL = 3** & **TIL = 13** & **TIL = 39** \\ \hline CRCSI & 14,970 & 2704 & 4056 \\ TBI & 16,164 & 69,524 & 204,500 \\ RCI & 16,194 & 70,174 & 210,500 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Multiplicity \(D_{tot}\) for different depths in mobile reception. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Method**} & \multicolumn{2}{c}{**TBS 76208**} & \multicolumn{2}{c}{**TBS 45352**} \\  & \(d_{min}\) & \(D_{tot}\) & \(d_{min}\) & \(D_{tot}\) \\ \hline CRCSI & 40 & 420 & 104 & 256 \\ TBI & 30 & 22,050 & 18 & 22,194 \\ RCI & 16 & 22,260 & 10 & 22,266 \\ NO & 2 & 22,260 & 2 & 22,266 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Comparison of minimum distance and multiplicity for fixed reception. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Method** & **TIL = 3** & **TIL = 13** & **TIL = 39** \\ \hline CRCSI & 106 & 53 & 204 \\ TBI & 12 & 52 & 156 \\ RCI & 7 & 27 & 79 \\ NO & 2 & 2 & 2 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Comparison of \(d_{min}\) for mobile reception. Since the wireless channel in the fixed reception scenario has a longer delay spread, the signal is more susceptible to frequency selective fading. Therefore, in the designed scheme, the method of changing the transmission sequence of the subcarriers can effectively combat continuous bit errors. It is worth noting that for the case of TBS equal to 45352, CRCSI only has a smaller gain over TBI and RCI. This is because burst errors are sufficiently dispersed in a relatively small TBS, which makes room for further improvement in randomization more limited. The simulation results illustrate a tendency of the gain being larger for large TBS. The performance of the proposed block interleaver in the LPLT scenario is also evaluated. In the simulation, the TDL-B channel model with a delay extension of 20 \(\upmu\)s is used, with a bandwidth of 10 MHz, and TBS equal to 9912. Figure 6 shows the BLER performance of different TILs at a middle moving speed of 60 km/h, while Figure 7 compares the system performance of the maximum TIL with the speed varying from 30 km/h to 120 km/h. It can be seen from Figure 6 that the performance difference of the three interleavers is not obvious when TIL equals 3. This is because the Doppler spread is small at this time  
Figure 5: Comparison for fixed reception. Figure 6: Comparison for mobile reception. and the channel coherence time is large, and the time selective fading experienced by the channel within 3 ms is still not obvious. When TIL equals 13, the gain of CRCSI compared to RCI and TBI reaches 0.5 dB and 0.1 dB\(@BLER=10^{-2}\), respectively.