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Abstract-Vehicular communication is characterized by a dynamic environment, high mobility, and comparatively low antenna heights on the communicating entities (vehicles and roadside units). These characteristics make the vehicular propagation and channel modeling particularly challenging. In this survey paper, we classify and describe the most relevant vehicular propagation and channel models, with a particular focus on the usability of the models for the evaluation of protocols and applications. We first classify the models based on the propagation mechanisms they employ and their implementation approach. We also classify the models based on the channel properties they implement, where we pay special attention to the usability of the models, including the complexity of implementation, scalability, and the input requirements (e.g., geographical data input). We also discuss the less-explored aspects in the vehicular channel modeling, including modeling specific environments (e.g., tunnels, overpasses, parking lots) and types of communicating vehicles (e.g., scooters, public transportation vehicles). We conclude the paper by identifying the under-researched aspects of the vehicular propagation and channel modeling that require further modeling and measurement studies.

Abstract-Several vehicular communication applications will involve multicast/broadcast communications where all vehicles in a certain region of interest are the intended recipients of particular messages. While there are several existing broadcast routing protocols for highway vehicular ad hoc networks (VANETs), very few solutions exist for urban VANETs in cities like New York City or Chicago. This paper attempts to fill this gap by proposing a new broadcast routing protocol, namely Urban Vehicular BroadCAST (UV-CAST) protocol, that addresses both the broadcast storm and disconnected network problems in urban VANETs. Key challenges imposed by urban VANETs as well as new mechanisms needed for meeting these challenges are identified and presented. Performance of the proposed UV-CAST protocol is evaluated in terms of network reachability, received distance, and network overhead in ideal Manhattan Street scenarios as well as in real cities, such as Pittsburgh. The overall performance of UV-CAST is excellent.

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Abstract-Several vehicular communication applications will involve multicast/broadcast communications where all vehicles in a certain region of interest are the intended recipients of particular messages. While there are several existing broadcast routing protocols for highway vehicular ad hoc networks (VANETs), very few solutions exist for urban VANETs in cities like New York City or Chicago. This paper attempts to fill this gap by proposing a new broadcast routing protocol, namely Urban Vehicular BroadCAST (UV-CAST) protocol, that addresses both the broadcast storm and disconnected network problems in urban VANETs. Key challenges imposed by urban VANETs as well as new mechanisms needed for meeting these challenges are identified and presented. Performance of the proposed UV-CAST protocol is evaluated in terms of network reachability, received distance, and network overhead in ideal Manhattan Street scenarios as well as in real cities, such as Pittsburgh. The overall performance of UV-CAST is excellent.

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Deploying Roadside Units (RSUs) for increasing the connectivity of vehicular ad hoc networks is deemed necessary for coping with the partial penetration of Dedicated Short Range Communications (DSRC) radios into the market at the initial stages of DSRC deployment. Several factors including cost, complexity, existing systems, and lack of cooperation between government and private sectors have impeded the deployment of RSUs. In this paper, we propose to solve this formidable problem by using a biologically inspired self-organizing network approach whereby certain vehicles serve as RSUs. The proposed solution is based on designing local rules and the corresponding algorithms that implement such local rules. Results show that the proposed approach can increase the message reachability and connectivity substantially.