Dynamic Packet Size Selection for 802.11 Inter-Vehicular Video Communications

This paper focuses on improving the performance of video communications in inter-vehicular environments using the 802.11 ad hoc network protocol. We present the results of transmission experiments between two cars equipped with 802.11 standard devices in two typical driving scenarios, urban and highway, showing the characteristics of each scenario in terms of link availability and SNR for different bitrates and packetization policies. Moreover, we also evaluate the video quality at the receiver by means of the PSNR distortion measure, showing that the best packetization policy depends on the scenario. On the basis of these results, we design an adaptive algorithm which dynamically varies the video packet size to improve the efficiency of the video transmission. Results show that consistent perceptual quality gains in terms of PSNR value (up to about 3 dB) can be achieved with respect to a fixed-policy transmission technique.