# Error Resilient Coding Techniques for Video Delivery over Vehicular Networks
## 5 Real Scenarios Evaluation
### Test Framework
This vehicle travels along the avenue, receiving the video stream from the RSUs through the specified service channel. Another vehicle drives nearby the video client which can act as a background traffic source (labeled as T in Figure 10b) by sending packets through the service channel at the specified Packets Per Second (PPS) rate. It is used to reproduce different network load conditions. The video client experiences isolated packet losses (mainly due to background traffic) and bursty packet losses (around the limits of RSUs coverage). In the experiments, the combination of the bit streams from previous sections has been used. For the tests, we have selected the BasketballDrill sequence (832 \(\times\) 480 pixels, 25 fps, bbd_25),  
Figure 10: (**a**) Partial view of the city of Kiev. The square indicates the area selected for the simulations; (**b**) Vehicular network scenario in OMNeT++/MiXiM/Veins. (red circles [A,B,C] = RSUs; blue circle [*] = video client; yellow square [T] = background traffic source; small circles = other vehicles; red polygons = buildings). encoded with 9 different encoding modes (AI, IPIP, IPPP, IPx, IPx25 pctCTU, IPx25 pctTIL, IPxpattern, LP, and LPI4) and with 6 different tile layouts (1, 2, 4, 6, 8 and 10 til/rm). For each selected bit stream, 4 different versions have been generated. One of these versions has been encoded without any FEC protection. The other three versions have been FEC protected with RaptorQ codes at different protection levels, 10%, 20% and 30%. Each bit stream (with or without protection) has been delivered by the three RSUs and received by the video client under 3 different \"network conditions\". The first group of tests has been conducted without injecting any background traffic. This group of tests is referred to as \"ideal conditions\" and permits the characterization of each one of the three zones mentioned before. After that, experiments have been performed under 2 further network conditions: one with moderate background traffic (62 packets per second of 512 bytes), and another with a high background traffic (125 packets per second of 512 bytes), both for protected bit streams and non-protected bit streams. The tests with the non-protected bit streams serve to evaluate the performance of the encoding modes and the frame layouts, regarding error resilience. The tests with the FEC protected bit streams serve to evaluate the specific level of protection added by RaptorQ codes. With these experiments, the real issues of vehicular networks are modeled. The main consequence of all these issues is the appearance of network packet losses to some extent. As well as the vehicles' mobility and the wireless channel, which cause problems to the transmission of any kind of data, the specific characteristics of the protocols involved in the communication have also influence in the reliability of the data delivery. For example, multichannel operation forces nodes to commute alternately between the control channel and the service channel, so the data which is being transmitted through the service channel (e.g., video streaming and background traffic, in our tests), has to wait in the sending buffers of the senders until the next service channel time slot is available. When the control channel time slot ends, all the nodes resume the transmission in the service channel so they have to contend for the wireless channel to transmit all the data accumulated in their buffers. In addition, the guard interval that has to be respected when the wireless network cards commute between the control channel and the service channel and vice versa, makes the real availability of the bandwidth for the service channel (in which the video is streamed) to be only 40% of the total. These issues are not taken into consideration by works which use, for example, standard WiFi protocols in real experiments or in simulations.