Vehicular ad hoc networks (VANETs) are no longer a futuristic promise but rather an attainable technology. The majority of services envisioned for VANETs either require the provisioning of multimedia support or have this support as an extremely beneficial feature. However, the highly dynamic topology of VANETs poses a demanding challenge for the fulfillment of the stringent requirements for video streaming. In this paper, we provide a deep understanding of the issue of unicast video streaming over VANETs and propose a novel protocol, VIRTUS. In video streaming, many packets are transmitted consecutively in a short period of time. VIRTUS takes this into consideration and extend the duration of the decision of nodes to forward packets from a single transmission to a time window. Furthermore, VIRTUS calculates the suitability of a node to relay packets based on a balance between geographic advancement and link stability. We also propose an extension, that separates the process of relay node selection from the transmission of video content and adopts a density-aware mechanism that adapts its behavior according to local density. Consequently, VIRTUS makes use of the reactive aspect of receiver-based solutions while remaining scalable to increases in transmission rates and density. We report through extensive realistic experiments the benefits of using VIRTUS towards delivering video at a higher quality, in a timely fashion, with lower overhead and fewer collisions.

A reliable solution for the task of unicast video streaming over urban VANETs is of great demand. Single path solutions which address this topic are highly prone to collision at a high data rates which are necessary for high quality videos. Multipath solution solves this problem by distributing the heavy traffic load into a set of paths. Among numbers of multipath works, only 2-path LIAITHON+takes into consideration the high dynamic topology of VANETs, route coupling effect, and path length growth. In this paper, we make several improvements on top of the 2-path LIAITHON+. We evaluate the use of more than two paths in this multipath solution. Moreover, the impact of added redundancy on the both 2-path and 3-path LIAITHON+is investigated as a solution for packet loss.

We tackle the issue of providing video streaming support over Vehicular Ad Hoc Networks (VANETs). Video streaming imposes stringent requirements in terms of delivery ratio and delay in order to provide a satisfying level of service at the user's end. In our work, we investigate the use of Erasure Coding to overcome packet loss and to fulfill video streaming requirements of delivery ratio. We have investigated two distinct coding techniques and evaluated thoroughly their peculiarities. This study has shown how Erasure Coding could improve delivery ratio without affecting end-to-end delay.

Video dissemination to a group of vehicles is one of the many fundamental services envisioned for Vehicular Ad hoc Networks. For this purpose, in this paper we describe VoV, a video dissemination protocol that operates under extreme traffic conditions. Contrary to most existing approaches that focus exclusively on always-connected networks and tackle the broadcast storm problem inherent to them, VoV is designed to operate under any kind of traffic condition. We propose a new geographic-based broadcast suppression mechanism that gives higher priority to broadcast to vehicles inside especial forwarding zones. Furthermore, vehicles store and carry received messages in a local buffer in order to forward them to vehicles that were not covered by the first dissemination process, probably as a result of collisions or intermittent disconnections. Finally, VoV employs a rate control mechanism that sets the pace at which messages must be transmitted in an attempt to avoid channel overloading and to overcome the synchronization effects introduced by the channel hopping mechanism employed by IEEE 802.11p. When compared to two well-known solutions -- UV-CAST and AID -- we show that our proposal is more efficient in terms of message delivery, delay and overhead.

Video streaming capabilities over Vehicular Ad Hoc Networks (VANETs) are crucial to the development of interesting and valuable services. However, VANETs are a challenging environment to this kind of communication due to the dispersion and movement of vehicles. In this work, we present a feasible solution to this problem. The VIdeo Reactive Tracking-based UnicaSt protocol (VIRTUS) is a receiving-based solution that uses vehicles' current and future location for a selection policy of relaying nodes. It fulfills video streaming requirements without incurring into an excessive number of transmissions. Besides that, it outperforms other baseline solutions.

Transmitting video content over Vehicular Ad Hoc Networks (VANETs) faces a great number of challenges caused by strict QoS (Quality of Service) requirements and highly dynamic network topology. In order to tackle these challenges, multipath forwarding schemes can be regarded as potential solutions. However, route coupling will severely impair the performance of multipath schemes. In this work, we present a LocatIon-Aware multIpaTH videO streamiNg (LIAITHON) scheme to address video streaming over urban VANETs. LIAITHON uses location information to discover two relatively short paths with minimum route coupling effect. The performance results have shown it outperforms the underlying single path solution as well as the node-disjoint multipath solution.

Vehicular Ad Hoc Networks (VANETs) are challenging environments for video dissemination since stringent requirements have to be satisfied. We have designed a protocol that is reactive to the dynamic topology of VANETs, adaptive to the non-uniformity of vehicles density throughout a city or a highway and that deliver packets in time for the playback of video frames. The Reactive, Density-Aware and Timely Dissemination protocol (REACT-DIS) was able to achieve low end-to-end latency with an acceptable number of transmissions. In order to meet delivery ratio requirements, we have used Network Coding to implement an additional redundancy control aimed at handling packet loss. By this manner, lower rates of frame loss were achieved which fulfill delivery ratios requirements for video-streaming while maintaining suitable levels of end-to-end latency and overhead.

Advancements in both on-board and wireless communication technologies provide the necessary backbone for the deployment of a network between vehicles. Most of the envisioned applications for these networks would be greatly favored by multimedia support provisioning. However, there are several issues to be handled in order to provide multimedia services with reasonable quality. In this work, we analyze a specific multimedia service that can be used by several interesting applications: video broadcasting. Particularly, we throughly discuss and evaluate the role of redundancy in improving this service. We have verified that although redundancy does increase the effectiveness in video broadcasting, coding techniques do not improve redundancy's efficiency.

The recent advances and wide availability of wireless access technologies and inter-vehicle communication systems are expected to culminate in the integration of different wireless networks such as the IEEE 802.11, 3G/4G, and WiMax, multimedia and sensor networks in the next generation vehicular networks. However, due to high mobility of vehicles, several issues remain to be resolved before real-time multimedia based applications over VANETs become a reality. In this paper, we propose to study the provision of multimedia support in VANET, and present an efficient Path Stability Protocol, which we refer to as PASTA, as an additional module to MAC layer protocols that aims at preventing path breaks between vehicles that are frequently within reach of each other but not necessarily on a continuous basis. We discuss the implementation of our protocol, and report on its performance evaluation using a wide range of realistic scenarios. Our results indicate that our PASTA protocol decreases significantly the end-to-end latency as well as the network jitter.

Vehicular Ad Hoc Networks (VANETs) have been widely studied, and the deployment of such networks is likely to happen soon as the required technology and commercial opportunities are already available. Most of applications proposed for these networks require a localization mechanism with reasonable accuracy. In addition to applications, most protocols rely on the availability of a system that determines vehicles' positions. As many vehicles are (or are in the process of being) equipped with GPS, the accurate localization of vehicles in VANETs is achievable. However, one issue that has been ignored is the localization of neighboring vehicles. In VANETs, nodes usually move at high speeds; the information about the position of a neighbour vehicle is therefore fast outdated. The naive approach for handling this issue is to increase the frequency by which periodic messages containing a node's position are exchanged. This solution might lead an unfeasible overhead significantly dropping the bandwidth available for the exchange of services' data. In this paper, we study this problem further, and propose a solution where vehicles predict the position of a neighbor for the near future. Through extensive experiments, we show that a prediction model of low complexity was able to considerably increase the accuracy of neighbor localization. Our mechanism has achieved an accuracy of 50 centimeters with a frequency of exchange of beacons 75% smaller than the naive approach.

Vehicular Ad Hoc Networks are a promising technology that provides several interesting new functionalities to drivers and passengers. These services are spread through a wide variety of applications, each with specific requirements in terms of latency, jitter and bandwidth, among other metrics. For this reason, it is crucial to provide mechanisms that can be used to offer different levels of communication quality in order to achieve reasonable performance in all services. In this paper, we demonstrate how link reliability may be used to support Quality of Service policies for any protocol based on unicast packets relay. This article is divided into two parts, the first of which describes how we estimate link reliability and evaluates how these estimations can be used to classify links into different groups with distinct quality. In the second part, this link reliability estimation model is used to group links into queues with different levels of expected transmission success ratios, which can be used to provide different quality levels depending on the requirements of each individual service. We show that the proposed mechanism adds little-to-none overhead to the overall network and provides an effective mean of supporting QoS in VANETs.

Mobile Ad Hoc Networks present several new challenges, mainly due to mobility. Publish/Subscribe is a communication paradigm that fits this network model well since the entities involved in the communication process do not need to be online at the same time or know each otherpsilas addresses. In order to develop properly a Pub/Sub based Architecture for MANETs, it is essential that designers understand how mobility impacts the performance of any solution. This work presents an analysis of the influence of mobility on a previous solution and extends it based on a different perspective on mobility in MANETs. We show that in using this new approach we have managed to achieve better match rates while sending substantially fewer messages.

In this paper, a new data dissemination algorithm for wireless sensor networks is presented. The key idea of the proposed solution is to combine concepts presented in trajectory-based forwarding with the information provided by the energy map of the network to determine routes in a dynamic fashion, according to the energy level of the sensor nodes. This is an important feature of an autonomic system, which must have the capacity of adapting its behavior according to its available resources. Simulation results revealed that the energy spent with the data dissemination activity can be concentrated on nodes with high-energy reserves, whereas low-energy nodes can use their energy only to perform sensing activity or to receive information addressed to them. In this manner, partitions of the network due to nodes that ran out of energy can be significantly delayed and the network lifetime extended.