## 5 Simulation Results
### Simulation Scenario  
The simulation experiments have been done for the scenario shown in Figure 10, where the user can receive four DVB-T signals from four emitters that belong to an SFN, and no GNSS satellites are visible when the user enters the grey area indicated in the figure. The user moves along a path with an initial location outside the grey area. In our simulation, four DVB-T emitters are placed.  
In the scenario of Figure 10, four DVB-T emitters of the same SFN are placed on the four semi-axes. They transmit the same signals on the same frequency, with the parameters summarized in Table 2.  
For the signal generation, we have used the Anritsu MX3700 generator, which is a laboratory Radio Frequency (RF) generator that can be modulated by an array of complex baseband samples. As an option, a DVB-T/H sample generation software is sold. We used such software to generate DVB-T-compliant baseband signals used as simulation sources. The receiver has a constant speed equal to 100 m/s, while the direction of the velocity changes from time-to-time. The signal received along the path has been simulated by combining shifted and attenuated versions of the generated signal. The delays have been simulated by shifting the FFT window according to the corresponding ranges between the user and the emitters. The SNR is simulated according to Equation (22):  
\[C/N_{0}=\frac{E[|s(t)|^{2}]}{N_{0}L_{u}} \tag{22}\]  
where \(s(t)\) is the transmitted signal; \(N_{0}\) is the noise floor; \(L_{u}\) is the signal attenuation according to the Hata model for urban areas, which is:  
\[L_{u}=69.55+26.16\log(f)-13.82\log(h_{B})-C_{H}+[44.9-6.55\log(h_{B})]\log(d) \tag{23}\]  
where \(C_{H}\) depends on the city size. For small and medium sized cities, it is:  
\[C_{H}=0.8+(1.1\log(f)-0.7)h_{M}-1.56\log(f)\]  
while, for large cities, \(C_{H}\) is:  
\[C_{H}=\left\{\begin{array}{l}8.29(\log(1.54h_{M}))^{2}-1.1,\quad if\;150\leq f \leq 200\\ 3.2(\log(11.75(h_{M}))^{2}-4.97,\quad if\;200\leq f\leq 1500\end{array}\right.\]where \(L_{u}\) is the path loss in urban areas in dB, \(h_{B}\) is the height of emitters in meters, \(h_{M}\) is the height of the receiver antenna in meters, \(f\) is the frequency of transmission in MHz, \(C_{H}\) is the antenna height correction factor and \(d\) is the distance between the base station and receiver in kilometers.  
Here, we suppose all the DVB-T transmitters are placed on the same height at 100 m. Furthermore, since all the emitters use the same frequency, the propagation loss changes only with the distance. The SNR of the received signal has been set equal to 10 dB, where the distance between the user and the emitter is equal to 5 km. The SNR in the other points is calculated according to Equation (23).  
The position is computed in two dimensions, regardless of the altitude, every 0.2 s.  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Parameters** & **Values** \\ \hline FFT size \(N_{FFT}\) & 2,048 \\ CP length & \(\frac{1}{4}\)(56 \(\upmu\)s) \\ Signal bandwidth & 8 MHz \\ Length of simulation & 20 s, 100 s \\ Symbol duration \(T_{symb}\) & 280 \(\upmu\)s \\ Sampling period \(T_{samp}\) & 109 ns \\ SNR & 10 dB \\ \hline \hline \end{tabular}
\end{table}
Table 2: Parameters of DVB-T signals. FFT, Fast Fourier Transform; CP, Cyclic Prefix; SNR, signal-to-noise ratio.  
Figure 10: Analyzed scenario.