## 5 Conclusions  
In this paper, we have proposed two efficient multiple access techniques namely LDS-F-OFDM and LDS-UFMC in which the LDS structure is combined with the new 5G waveforms. First of all, we have presented the state-of-art of the previous work done on LDS and we have detailed the transmitters and receivers of these new schemes. Then, we have highlighted our contribution that consists in evaluating these new schemes over different types of channels, specifically, a vehicular channel with a high mobility. Simulation results show that LDS-F-OFDM significantly achieves higher performance improvements compared to LDS-OFDM and LDS-UFMC in all scenarios, while maintaining an affordable complexity at the transmitter and the receiver side. The improvements are directly related to the advantages that f-OFDM waveform offers by addressing the adequate filter. In future work, we propose to analyse these schemes with different types of receivers in manner to reduce the complexity and to improve the performances. Some of the receivers that can be found in the literature are the SIC-MPA where we combine SIC and MPA to reduce the overall complexity and the JSG receiver which is a very high complex receiver but provides a lot of improvements to the  
Figure 7: Schemes comparison over the EVA channel with different speed limits.  
system. Furthermore, we consider evaluating theses schemes over different vehicular channels such as a confined channel and with different channel specifications considering the other operating band of FR1 i.e., 25 GHz.  
Conceptualisation, I.K., R.E., F.E. and N.I.; methodology, I.K., R.E. and F.E.; software, I.K.; validation, R.E., F.E. and N.I.; formal analysis, R.E. and F.E.; investigation, I.K., R.E. and F.E.; resources, R.E. and F.E.; writing--original draft preparation, I.K.; writing--review and editing, I.K.; supervision, R.E., F.E. and N.I.; project administration, R.E. and F.E.; funding acquisition, R.E. and F.E. All authors have read and agreed to the published version of the manuscript.  
The present research work has been supported by the European project SECREDAS funded ECSEL. The preliminary results were partly supported by ELSAT project. ELSAT 2020 project is co-financed by the European Union with the European Regional Development Fund, the French state and the Hauts de France Region Council.  
The authors declare no conflict of interest.  
The following abbreviations are used in this manuscript:  
\begin{tabular}{l l} OFDM & Orthogonal Frequency Division Multiplexing \\ FBMC & Filter-Bank Multi-Carrier \\ UFMC & Universal Filtered Multi-Carrier \\ BER & Bit Error Rate \\ LTE & Long Term Evolution \\
3 GPP & 3 rd Generation Partnership Project \\ SC-FDMA & Single Carrier Frequency Division Multiple Access \\ ETSI & European Telecommunications Standards Institute \\ NR-V2X & New-Radio V2X \\ CP & Cyclic Prefix \\ UL & Uplink \\ DL & Downlink \\ QPSK & Quadrature Phase Shift Keying \\ QAM & Quadrature Amplitude Modulation \\ IDMA & Interleaver Division Multiple Access \\ PDMA & Pattern Division Multiple Access \\ SCMA & Sparse Code Multiple Access \\ CDMA & Code Division Multiple Access \\ JSG-IOTA & Joint Sparse Graph-Isotropic Orthogonal Transfer Algorithm \\ MPA & Message Passing Algorithm \\ FEC & Forward Error Correction \\ EPA & Expectation Propagation Algorithm \\ IFFT & Inverse Fast Fourier Transform \\ LS & Least Square \\ FFT & Fast Fourier Transform \\ ISI & Inter Symbol Interference \\ OOB & Out Of Band \\ PDP & Power Delay Profile \\ EVA & Extended Vehicular A \\ \end{tabular}