# Error Resilient Coding Techniques for Video Delivery over Vehicular Networks
## 5 Real Scenarios Evaluation
### Analysis of Results
#### 5.2.2 Ideal Conditions with FEC Protection  
Now, we will analyze the performance of the FEC protection in Zone II and Zone III under ideal conditions (without any background traffic load). In order to evaluate FEC recovery efficiency, the After-Recovery Packet Loss Ratio (ARPLR) metric measures the percentage of the source video packets missing over the total source video packets of the sequence, once the FEC recovery process has been carried out. In Table 5, the PLR, ARPLR, and TLR values for three of the encoding modes (AI, IPIP and IPPP), protected with three levels (10%, 20% and 30%), averaged over all the tiles per frame layouts, are shown. The rest of the encoding modes have shown a similar behavior so, for the sake of concision, only three of them have been included in the table. \begin{table}
\begin{tabular}{l c c c c c c} \hline \hline  & \multicolumn{3}{c}{**Zone II**} & \multicolumn{3}{c}{**Zone III**} \\ \cline{2-7}  & **PLR** & **ARPLR** & **TLR** & **PLR** & **ARPLR** & **TLR** \\ \hline AI/10\% & 2.00\% & 1.94\% & 2.03\% & 23.49\% & 29.05\% & 30.25\% \\ AI/20\% & 1.99\% & 1.78\% & 1.81\% & 23.94\% & 30.95\% & 32.37\% \\ AI/30\% & 2.01\% & 1.63\% & 1.67\% & 24.32\% & 28.62\% & 29.55\% \\ \hline IPPP/10\% & 1.98\% & 1.89\% & 1.95\% & 23.08\% & 27.71\% & 28.22\% \\ IPPP/20\% & 2.00\% & 1.57\% & 1.62\% & 23.50\% & 28.05\% & 28.59\% \\ IPPP/30\% & 2.00\% & 1.42\% & 1.49\% & 24.05\% & 30.89\% & 31.61\% \\ \hline IPPP/10\% & 2.00\% & 1.93\% & 1.98\% & 23.09\% & 26.49\% & 26.95\% \\ IPPP/20\% & 2.00\% & 1.78\% & 1.86\% & 23.55\% & 26.90\% & 27.45\% \\ IPPP/30\% & 2.00\% & 1.78\% & 1.89\% & 23.99\% & 28.43\% & 29.19\% \\ \hline \hline \end{tabular}
\end{table} 
Table 5: PLR, ARPLR and TLR for FEC-protected bit streams under “ideal conditions” (0 pps) for zones II and III for AI, IPIP, and IPPP encoding modes for three levels of the protection level parameter (10%, 20% and 30%) averaged over all the til/rm layouts. In Zone II, the PLR values of the protected bit streams are very similar to the non-protected ones. The ARPLR values for this zone do not show a good efficiency of the RaptorQ packet recovery process. RaptorQ codes have good recovery properties when dealing with isolated losses, but a minimum number of packets need to be received, which is not the case when bursty losses are encountered. The recovery of missing packets from a burst of packet losses would need a very long protection window for any of the FEC techniques available (which would introduce a long delay) or else the use of other complementary techniques like interleaving, which converts bursty losses into isolated losses, but which also introduces a non-negligible delay in the transmission process. So, shaded areas (where no packet can be received) are not suitable for live video delivery and a readjustment of the RSUs location in order to eliminate these \"black zones\" may be the most appropriate action. In this zone, as happened with the non-protected bit streams, the ARPLR values do not either generate high TLR values. In Zone III, the PLR is around 23-24%. The bursty nature of losses in this zone makes FEC recovery unfeasible, as in Zone II. Furthermore, there is a striking fact in Zone III measurements: the ARPLR values are higher than the PLR values. How can this happen? The PLR metric takes into consideration the total number of packets in the FEC-encoded packet stream, which includes protected packets and repair packets. If losses are bursty and FEC recovery is not effective, only protected packets (which include video data) will be translated into source video packets (by just taking away the trailer). As repair packets may recover a few (or no) source video packets they are not useful and the proportion of missing source video packets over the original number of source video packets may produce a higher value for the ARPLR than for the PLR. As a consequence of the high TLR values in this zone, the reconstructed video sequences can be considered useless.