# 5G V2X Performance Comparison for Different Channel Coding Schemes and Propagation Models
## 5 Conclusions and Future Work  
V2X systems have been very popular in the research community in the last few years. It would be desirable to build a dynamic changing 5G V2X system with emphasis on channel coding and QoS. This article considers the three channel coding schemes used in LTE-V2X and 5G-NR V2X communication systems, i.e., turbo, polar and LDPC coding. Subsequently, a realistic, but with considerably reduced complexity, V2X system modelling methodology is proposed considering different propagation models. The novelty of this work is the combined approach and analysis of these propagation models and the different channel coding schemes. Finally, the incorporated stochastic model is analysed based on the recent 5G-V2X standard. We investigate five different propagation models, i.e., highway-LOS, highway-NLOSv, urban-LOS, urban-NLOS and urban-NLOSv, for three different data frame lengths, i.e., 128-, 256- and 512-bit frames. Therefore, in total, we examined 15 simulation scenarios. Our analysis shows the dominance of turbo codes in small-length data-frame cases. Turbo codes proved to have superior performance in low and middle SNR regions, which are better than polar coding by approximately 1.5 dB in the LOS cases and 2 dB in NLOS and NLOSv cases. This gap is larger in LDPC, where turbo codes are superior by approximately 2 dB in LOS and 2.5 dB in NLOS and NLOSv cases. This difference seems to be typically independent of the frame length and the traffic model and depends only on the channel state condition. Of course, this phenomenon starts to vary at high SNR, where error floor occurs. These error floors are present only in turbo and LDPC coding and are absent from polar coding [72]. The performance of turbo codes is affected mainly in the 128-bit scenarios by the presence of error floors. These scenarios show that polar coding acquires superior performance above 7 dB in scenarios 1 and 3, i.e., LOS cases, above 8 dB in scenarios 2 and \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline \multirow{2}{*}{
\begin{tabular}{c} **Related** \\ **References** \\ \end{tabular} } & \multicolumn{4}{c}{**Channel Coding**} & \multicolumn{4}{c}{**Performance**} \\  & & & & & & **V2X rel. 16** & \multicolumn{2}{c}{**Parameter**} & \multirow{2}{*}{**Short Frame**} \\  & **Log** & **X\(\!\!\)** & **X\(\!\!\)** & **X\(\!\!\)** & & & **Channel** & & **Length** \\  & **BCJR** & **X\(\!\!\)** & **X\(\!\!\)** & **X\(\!\!\)** & **X\(\!\!\)** & **X\(\!\!\)** & **X\(\!\!\)** & **X\(\!\!\)** & **X\(\!\!\)** & **X\(\!\!\)** \\ \hline
[33] & & ✓ & & & & & ✓ & ✓ & ✓ \\ \hline
[34] & ✓ & ✓ & & & & ✓ & ✓ & ✓ & ✓ \\ \hline
[35] & ✓ & ✓ & ✓ & & & ✓ & ✓ & & ✓ \\ \hline
[36] & & & ✓ & ✓ & ✓ & & & ✓ & \\ \hline
[37] & & & ✓ & ✓ & & & ✓ & & \\ \hline
[38] & & & ✓ & ✓ & & & ✓ & & \\ \hline
[39] & & & ✓ & ✓ & ✓ & & & ✓ & \\ \hline
[40] & & & ✓ & ✓ & & & ✓ & & \\ \hline
[41] & & & ✓ & ✓ & ✓ & & ✓ & ✓ & ✓ \\ \hline
[42] & & & & ✓ & ✓ & & ✓ & & \\ \hline Proposed approach & ✓ & ✓ & ✓ & ✓ & ✓ & ✓ & ✓ & ✓ & ✓ \\ \hline \hline \end{tabular}
\end{table} 
Table 13: Comparison of our proposed approach with published literature. The symbol \(\blacktriangledown\) defines that the field has been implemented and examined in the corresponding references. 5, i.e., NLOSv cases, and above 9 dB in scenario 4, namely the NLOS case. The simulation results for the 256-bit frame show that polar and LDPC diminish the gap at 1 to 1.5 dB, but they never reach the performance of turbo coding, as BER in the latter zeroes rapidly. Finally, the 512-bit frame simulation results show that turbo codes retain their superiority, unchanged at the high SNR region. Polar coding has a very a fast rate of convergence, especially in 128- and 256-bit scenarios, but it has a severe drawback. Polar coding in all simulations has BER equal to 0.4 at 0 dB. This rate is 0.1 dB far from been totally random, i.e., having the same efficiency as flipping a coin.