## 4 Performance Evaluation
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Parameters** & **Symbol** & **Value** \\ \hline \multicolumn{3}{c}{Pilots Parameters} \\ \hline Pilots Arrangement & - & Comb type \\ \hline Pilots Spacing & \(N_{ps}\) & 4 \\ \hline Number of Pilots per symbol & \(N_{P}\) & 156 \\  & & 72 \\ \hline \multicolumn{3}{c}{UFMC} \\ \hline Filter Length & \(L_{U}\) & 65 \\  & 33 \\ \hline Filter Type & - & Dolph-Chebyshev \\ \hline Side Lobe Attenuation & - & 50 dB \\ \hline Number of Subbands & \(S\) & 52 \\  & 24 \\ \hline Subband size & \(Q\) & 12 \\ \hline \multicolumn{3}{c}{F-OFDM} \\ \hline Filter Length & \(L_{F}\) & 513 \\  & 257 \\ \hline Window function & \multicolumn{3}{c}{Hann} \\  & - & Hamming \\  & \multicolumn{3}{c}{Blackman} \\ \hline \multicolumn{3}{c}{LDS Scheme Parameters} \\ \hline Effective Processing gain & \(d_{v}\) & 3 \\ \hline Interference Pattern & \(d_{c}\) & 3 \\ \hline Number of Users & \(N_{u}\) & 468 \\  & 216 \\ \hline Modulation & - & BPSK \\ \hline \hline \end{tabular}
\end{table} 
Table 2: _Cont._subcarriers concentrates the energy in one main lobe. This results in less ISI, and thanks to the LDS structure, the MUI are eliminated, thus, reducing the overall interference. Hence, it is expected that the f-OFDM with the LDS structure achieve a better BER performance. Meanwhile, LDS-UFMC shows a slight performance degradation compared to LDS-OFDM. However, UFMC offers lower OOB and the main advantage of UFMC is the increased spectral efficiency. Consequently, a trade-off must be taken in consideration depending on the requirements of the application. The second and main channel used to simulate these schemes is the Extended Vehicular A (EVA) model channel, its power delay profile is provided in [25]. Similarly to the TDL-A model, the EVA model is characterised by a Jake's Doppler spectrum and the maximum speed simulated is 300 km/h, hence the maximum Doppler shift \(f_{d}=556\) Hz and specifically modelled to simulate a vehicular channel. Figure 4(a) shows the BER performance of the LDS-F-OFDM and LDS-UFMC compared to LDS-OFDM over an EVA channel with a computed speed of 100 km/h which means that the maximum Doppler shift is \(f_{d}=185\) Hz with a subcarrier spacing of \(\Delta_{f}=15\) kHz and an FFT size of 1024, hence only 468 subcarriers left for data transmissions. For simplicity, we consider 468 users each sending one BPSK modulated symbol with a power of 1 Watt. In fact, this is the worst loading scenario where we have the number of users equal to the number of subcarriers allocated to data transmission which  
Figure 4: Performance of the proposed schemes over a Tapped Delay Line (TDL)-A channel. means that each user will be able to send only one symbol. It can be noticed that the LDS-F-OFDM slightly outperforms once more both LDS-OFDM and LDS-UFMC with its all different types of filters deployed. While Hann, Hamming and Blackman windows achieve almost the same BER performance, Hann window function is the filter susceptible to give better OOB performance. In terms of spectral efficiency, LDS-UFMC compared to LDS-F-OFDM and LDS-OFDM comes first due to the removal of the CP. However, observing the used subcarriers for data transmission due to the use of the pilot with only 4 subcarrier spacing, we notice the overall degraded spectral efficiency. This is completely justified by the need of an efficient channel estimation because of the high changing nature of the channel. The BER performance of the proposed schemes with a computed speed of 100 km/h and a subcarrier spacing of \(\Delta_{f}=30\) kHz and 512 subcarriers is presented in Figure 4(b). It is worth noting that LDS-F-OFDM shows again better performance at low SNR, while at higher SNR, all the proposed schemes face slight performance degradation. In fact, while employing higher subcarrier spacing to combat the Doppler shift, the spectral efficiency is reduced and also the number of subcarriers allocated to pilots is reduced (156 subcarriers in the first system vs. 72 in the second).