## 4 Material and Methods
### Implemented Systems and Simulation Parameters
\begin{table}
\begin{tabular}{c c} \hline \hline
**Parameters** & **Values** \\ \hline Channel bandwidth B & 8 MHz \\ \hline Transmission frequency \(f_{0}\) & 474 MHz \\ \hline Vehicle speed \(v\) & 50 km/h (13.88 m/s) to 150 km/h (41.66 m/s) \\ \hline Normalized CFO & 0.01, 0.02, 0.03, 0.04, 0.05 \\ \hline OFDM subcarrier number \(N_{FFT}\) & 8192 \\ \hline OFDM cyclic prefix & 1/32 \\ \hline OFDM symbol duration & 896 μs \\ \hline OFDM subcarrier spacing & 1116.07 Hz \\ \hline Constellation size & 16 \\ \hline Number of bits per symbol QAM & 4 \\ \hline LDPC frame length & 64,800 \\ \hline LDPC code rate & 1/2 \\ \hline \multirow{3}{*}{LDPC Matlab function} & dvbs2 ldpc (parity check matrix) \\ \cline{1-1}  & comm.LDPCEncoder (encoding) \\ \cline{1-1}  & comm.LDPCDecoder (decoding) \\ \hline UFMC filter length & \(N_{FFT}\)/32 \\ \hline UFMC sub-band bandwidth & 42 \\ \hline UFMC sub-band number & 172 \\ \hline UFMC sub-band offset & 484 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Simulation parameters. \(f_{1}\) using Equations (9) and (10). The subcarrier spacing was then equal to 1116.07 Hz, as computed in Equation (18). \[f_{1}=\frac{\frac{64}{7}\times\frac{8}{8}}{N_{FFT}} \tag{17}\]  
\[f_{1}=\frac{\frac{64}{7}\times\frac{8\times 10^{6}}{8192}}{8192}=1116.07 Hz \tag{18}\]  
The OFDM symbol duration was equal to the inverse of the subcarrier spacing as already mentioned in Equation (8). The OFDM symbol duration was then equal to 896 us. Therefore, the normalized CFO value was computed using Equations (6) and (14). * For a vehicle speed of 50 km/h, the Doppler shift was equal to 21.94 Hz, and the normalized CFO was equal to 0.0197
* For a vehicle speed of 150 km/h, the Doppler shift was equal to 65.83 Hz, and the normalized CFO was equal to 0.0590  
These values were used for the simulation, considering an approximation to two decimal places where CFO varied from 0.01 to 0.05. 2. Justification for the choice of other parameters values  
DVB-T2 defines five channel bandwidths: 1.7 MHz, 6 MHz, 7 MHz, 8 MHz, and 10 MHz. The channel bandwidth of 8 MHz was chosen as it is the most used in DTT deployment. In particular, the DVB consortium defined a spreadsheet which contained a set of configuration parameters useful for broadcasters during deployment [39]. All of these configurations only included a channel bandwidth of 8 MHz. DVB-T2 defines six numbers of subcarriers: 1024 (1K mode), 2048 (2K mode), 4096 (4K mode), 8192 (8K mode), 16,384 (16K mode), and 32,768 (32K mode). K is equal to 1024 subcarriers. As defined in [35] (pages 846-847), the higher the number of subcarriers, the closer the subcarriers are to each other, and the more sensitive DVB-T2 is to the Doppler effect. Then, low numbers of subcarriers are recommended for mobile reception in DVB-T2. Furthermore, mobile reception was tested in some countries where the last three modes' performance was analyzed by field measurements. It was demonstrated that the 8K mode presented higher performance than the 16K mode, which in turn had higher performance than the 32K mode [35] (pages 846-847). It was noted that the 32K mode was worse for mobile reception with a mobile speed varying from 60 km/h to 100 km/h. Therefore, the choice was made to use the 8K mode (8192 subcarriers), to see the impact on the simulation of the increase in CFO and consequent increase in mobile speed to 150 km/h. DVB-T2 defines four constellation orders: 4-QAM, 16-QAM, 64-QAM, and 256-QAM. As the constellation order increases, so does the number of bits transmitted per symbol. As a result, throughput increases. But higher-order QAMs such as 64-QAM and 256-QAM are more susceptible to noise and interference because the constellation points are closer together. As the purpose of this study was to evaluate the robustness of DVB-T2 signals, the choice was made to use 16-QAM, which is more robust and reliable in difficult environmental conditions. It is relevant to note that 4-QAM is the most robust QAM. However, it is the constellation order with the lowest bit rate.