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One of the most important goals of vehicular ad hoc networks (VANETs) in smart cities is the efficient management of accidents, specially to prevent them. Our research lies on a promising smart service, which soon might be available in our cities. After the occurrence of an accident, a vehicle could make a light and short video of the situation and send it through the VANET till reaching an access point in the infrastructure of the city to alert the emergencies service (e.g., 911 or 112). With a video message, the level of seriousness of the accident could be better interpreted by the authorities (i.e., health care unit, police, ambulance drivers) than with a simple text message. In this way, vehicles could participate in reporting a situation in the city using the ad hoc network so it would be possible to have a quick reaction of the emergency units and even prevent further accidents. The deployment of an efficient routing protocol to manage video-reporting messages in VANETs has important benefits by enabling a fast warning of the incident, which potentially might save lives. To contribute with this goal, we propose a multimedia multimetric map-aware routing protocol to provide video-reporting messages over VANETs in smart cities. Furthermore, a realistic scenario is created by using real maps with SUMO including buildings that may interfere the signal between sender and receiver. Also, we use our REVsim tool that allows vehicles to avoid choosing vehicles behind buildings to be chosen as next forwarding nodes. Simulations show the benefits of our proposal, taking into account the mobility of the nodes and the presence of interfering buildings. Index Terms-Building attenuation, realistic urban scenarios, smart cities, vehicular ad hoc networks, video-streaming services. I. INTRODUCTIONA VEHICULAR ad hoc network (VANET) is an infrastructureless type of network where nodes are vehicles [3], [4]. VANETs are wireless networks that are emerging thanks to advances in wireless technologies and in the automotive industry. Vehicular networks are formed by moving vehicles equipped with wireless interfaces, as it is shown in Fig. 1. VANETs Manuscript

In recent years, the general interest in routing for vehicular ad hoc networks (VANETs) has increased notably. Many proposals have been presented to improve the behavior of the routing decisions in these very changeable networks. In this paper, we propose a new routing protocol for VANETs that uses four different metrics. which are the distance to destination, the vehicles' density, the vehicles' trajectory and the available bandwidth, making use of the information retrieved by the sensors of the vehicle, in order to make forwarding decisions, minimizing packet losses and packet delay. Through simulation, we compare our proposal to other protocols, such as AODV (Ad hoc On-Demand Distance Vector), GPSR (Greedy Perimeter Stateless Routing), I-GPSR (Improvement GPSR) and to our previous proposal, GBSR-B (Greedy Buffer Stateless Routing Building-aware). Besides, we present a performance evaluation of the individual importance of each metric to make forwarding decisions. Experimental results show that our proposed forwarding decision outperforms existing solutions in terms of packet delivery.

Video over vehicular networks continues to receive warranted attention, with envisioned applications having the potential to present entirely new opportunities and revolutionise existing services. Many video systems have been proposed, ranging from safety to advertising. We propose a novel system for VANETs, namely the TArgeted Remote Surveillance (TARS) module for the existing Greedy Perimeter Stateless Routing (GPSR) protocol which permits multiple mobile vehicles to request and receive live video feeds from vehicles within a select geographic region. The multi-hop, vehicle-to-vehicle system enables mobile units to surveil a target area in real time by leveraging the dashboard cameras of vehicles moving within the target region. We combine several proposed extensions to the core protocol to introduce a dynamic real time congestion aware clustering scheme to achieve this. Our proposed system is compared against existing routing protocols using mobility data from Nottingham. GPSR-TARS outperforms the protocols assessed in key criteria crucial for meeting the quality of service demands of live multimedia dissemination.

Road safety applications envisaged for Vehicular Ad Hoc Networks (VANETs) depend largely on the dissemination of warning messages to deliver information to concerned vehicles. The intended applications, as well as some inherent VANET characteristics, make data dissemination an essential service and a challenging task in this kind of networks. This work lays out a decentralized stochastic solution for the data dissemination problem through two game-theoretical mechanisms. Given the non-stationarity induced by a highly dynamic topology, diverse network densities, and intermittent connectivity, a solution for the formulated game requires an adaptive procedure able to exploit the environment changes. Extensive simulations reveal that our proposal excels in terms of number of transmissions, lower end-to-end delay and reduced overhead while maintaining high delivery ratio, compared to other proposals.

Obstacles in Vehicular ad hoc networks (VANETs) in urban scenarios are an important issue. Normally, in traffic simulators vehicles can send/receive packets between each other if they are in the same transmission range no matter if an obstacle is presented or not between them. For this reason, checking if there is an obstacle between sender and receiver is an important goal. In this paper, we present a program named REVsim1.0 (Realistic Environment for Vanets simulation) [1] capable to detect at each instant of time if between a sender and a receiver a communication can be established or conversely, if an obstacle is found and such a communication is not possible. Parameters such as α, β, road resolution and transmission range have been defined and used in our proposed algorithm. Finally, a validation of our algorithm is shown.Permission to make digital or hard copies of all or part of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation on the first page. Copyrights for components of this work owned by others than the author(s) must be honored. Abstracting with credit is permitted. To copy otherwise, or republish, to post on servers or to redistribute to lists, requires prior specific permission and/or a fee. Request permissions from Permissions@acm.org.

Routing in mobile ad hoc networks is based on the cooperation of the network's nodes. The presence of selfish nodes that do not cooperate in this task drastically reduces the number of delivered packets. In order to find the better paths that include nodes willing to cooperate, we propose a new routing algorithm based on the reputation of the nodes. In our proposal, each node locally assigns a reputation value to the rest of the nodes in the network and next it uses the assigned reputation values to find out the better routing paths, in order to minimize the overall packet loss ratio. We assume that nodes have a stationary routing behavior, but we also include a mechanism to detect changes in their behavior. Our approach has been evaluated in the presence of selfish nodes, in order to compare it with the dynamic source routing algorithm, obtaining a reduction in the packet loss ratio at the expenses of a small increase in the number of hops taken by the packets to reach their destinations.

A mobile ad hoc network (MANET) is a set of autonomous mobile devices connected by wireless links in a distributed manner and without a fixed infrastructure. Real-time multimedia services, such as video-streaming over MANETs, offers very promising applications, e.g., two members of a group of tourists who want to share a video transmitted through the MANET they form, a video-streaming service deployed over a MANET where users watch a film, among other examples. On the other hand, social web technologies, where people actively interact online with others through social networks, are leading to a socialization of networks. Information of interaction among users is being used to provide socially-enhanced software. To achieve this, we need to know the strength of the relationship between a given user and each user they interact with. This strength of the relationship can be measured through a concept called tie strength (TS), first introduced by Mark Granovetter in 1973. In this article, we modify our previous proposal named multipath multimedia dynamic source routing (MMDSR) protocol to include a social metric TS in the decisions taken by the forwarding algorithm. We find a trade-off between the quality of service (QoS) and the trust level between users who form the forwarding path in the MANET. Our goal is to increase the trust metric while the QoS is not affected significantly.