# Error Resilient Coding Techniques for Video Delivery over Vehicular Networks
## 5 Real Scenarios Evaluation
### Analysis of Results
#### 5.2.4 Background Traffic Conditions with FEC Protection  
Regarding the FEC protected bit streams, in Table 7, the performance of RaptorQ codes in Zone I for a background traffic at 62 and 125 pps for different protection levels (10%, 20% and 30%) and different tiles per frame layouts averaged over all the encoding modes is shown. In Zone I, under moderate traffic conditions, a protection level of 30% gets almost 100% of packet recovery for all the layouts of tiles per frame (only at 1 tile per frame, a very low ARPLR value of 0.02%, which produces a residual TLR of 0.05% remains). Encoding a video sequence at 10 tiles per frame produces a bit stream around 9-12% larger than encoding it at 1 tile per frame. If we protect the bit stream with a protection level of 30%, the tile-layout overhead can be avoided in Zone I under these precise conditions. Also, a protection level of 20% nearly completely recovers all the missing source video packets, so the layouts with medium and low numbers of tiles per frame can be used, avoiding extra overhead and still obtaining the best video quality. If a protection level of 20% or 30% is used, then the most efficient encoding mode (LP) provides the best quality, and, therefore, it is the best candidate to be used under these network conditions. Please note that, for a certain til/rm layout, all FEC protection levels produce very similar PLR values (even more, when the protection level increases, the PLR value slightly decreases). In the experiments where a more dense background traffic is used (125 pps) the PLR values obviously increase. Under these conditions, a protection level of 30% can restore almost all the missing packets for every layout, and a protection level of 20% also obtains good ARPLR values, mainly for layouts with a high number of tiles per frame. If Table 7 is compared with Table 6 (125 pps; bit streams  
Figure 11: PSNR for every til/rm layout and every encoding mode. (Zone I; without FEC protection; 62 pps and 125 pps background traffic conditions). without FEC protection), it is observed that the PLR values are very similar. This means that the added FEC protection does not have an adverse effect in the PLR values obtained. Regarding the encoding modes performance, in Figure 12, the PSNR values for every encoding mode and every til/rm layout, with a protection level of 10% are shown. In Figure 12a, with moderate traffic conditions in Zone I, the plotted curves recommend the use of the IPPP and LPI4 encoding modes for the 4 and 6 til/frame layouts, and the use of the LP encoding mode for the 8 til/rm layout. By comparing Figures 11a and 12a, the benefit of using RaptorQ codes against isolated losses, even for a moderate protection level of 10%, is proven. In Figure 12b, the PSNR values for Zone I and a background traffic of 125 pps are shown. The best quality is obtained for a layout of 10 til/rm and the LPI4 and IPxpattern encoding modes. For the 62 pps traffic conditions and a protection level of 20% (Table 7), the recommendation was to use a low number of tiles per frame layout (to reduce overhead) and the LP encoding mode (which provided the best PSNR value). If the LP encoding mode and a layout with low number of tiles per frame (1, 2 or 4 til/rm) are selected and the network conditions change into 125 pps, the TLR values move away from 0% (3.54-16.34%), and PSNR values are low. Therefore, as network conditions in a vehicular environment are continuously changing, an encoding mode, such as LP, which is so sensitive to packet loss (even for low TLR), is always a risky choice (unless 0% TLR could be guaranteed by high protection levels). For Zone II, the PLR, ARPLR, and TLR values for background traffic conditions of 62 pps and 125 pps are higher than those in Zone I. By correlating TLR values and PSNR of many tests, we have observed that with the four most robust modes (IPPP, LPI4, IPIP and AI), TLR values under 15% may produce PSNR values over 29 dB.