Video and image communications can assist in highway traffic control, accident avoidance and management as well as road congestion control and coordination. This paper studies video streaming over wireless medium among a cluster of vehicles in an ad-hoc network. Through intense tradeoff study, we investigate the issues encountered in building a robust system that would allow automobiles to effectively transmit multimedia information in an ad-hoc network with constantly changing wireless environments. Based on our OPNET simulation results, we offer some design guidelines for transmitting streaming video over a vehicular adhoc network. I. INTRODUCTIONAs the number of vehicles on the road increased over the years, the need for safety on our roads cannot be over emphasized. VANET (Vehicular Ad-hoc NETwork) is a cluster of transporters equipped to communicate with each other either in an ad-hoc way (without any existing infrastructure) or with a nearby Road Side Unit (RSU) [2]. VANET has become an increasingly interesting focus of researchers and the automobile industry because it can enhance safety on the roadways by allowing vehicles to communicate with one another to prevent unwanted situations, thus enhancing comfort and safety of road users.As a part of the AUTO21 research group, our aim is to enhance safety on the road by using video and image communication to assist drivers without taking driving control from them [1]. VANET faces some difficulties to handle adhoc communication both among cars [2] and with Road Side Unit (RSU). The constantly changing vehicular environment and ad-hoc nature (governed mostly by the physical topology of the road and the proximity of nearby vehicles) of VANET poses the need for a careful study. Furthermore, information being sent in this network has to be real-time. Retransmissions may not be allowed as the delay could cause a lot of loss (which unfortunately is expected for a mobile adhoc network as route discovery time is inevitable. The study of tradeoffs among different routing algorithms in WiMAX Ad hoc networks is shown in [12]. To obtain reasonable performance, RSUs have to be much simpler than WiMAX or LTE base stations, and every tier in the OSI model has to be optimized for this purpose. One must also understand the traffic patterns in order to find an effective distributed transport layer protocol suite for this purpose. Therefore, we shall first focus on the video and image traffic, not only for the reasons given earlier,

This paper reports on the design of an OPNET simulation platform to test the performance of sending real-time safety video over VANET (Vehicular Adhoc NETwork) using the WiMAX technology. To provide a more realistic environment for streaming real-time video, a video model was created based on the study of video traffic traces captured from a realistic vehicular camera, and different design considerations were taken into account. A practical controller over real-time streaming protocol is implemented to control data traffic congestion for future road safety development. Our driving video model was then integrated with the WiMAX OPNET model along with a mobility model based on real road maps. Using this simulation platform, different mobility cases have been studied and the performance evaluated in terms of end-to-end delay, jitter and visual experience.

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This paper studies video streaming system over a wireless medium. The major challenge is to provide a robust link along the transmission/transport path and most importantly through noisy channels/networks that could add or drop bytes by unforeseeable factors. As a remedy for this phenomenon, we combine forward error correction, blind compensation and traffic shaping to improve the over all performance. We report on the experiments on this unique performance improvement method. The results of our study can find applications in WiMax and AVCP.

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