ABSTRACT Vehicular ad hoc networks (VANETs) are very changeable networks due to the highly dynamic movement of their nodes, resulting in frequent link disconnection and variable node density. One of the most challenging issues in VANETs is to propose a suitable routing scheme that is adapted to the characteristics of such a dynamic topology. Position‐based routing schemes that are effective in handling dynamic changes in the topology of VANETs are proposed. This article proposes an efficient routing protocol based on a greedy forwarding approach called ERGF. The proposed protocol is a position‐based routing protocol that uses fresh vehicular traffic information in the routing process. ERGF consists of two main algorithms: the vehicle traffic freshness dissemination algorithm and the greedy forwarding algorithm. The both algorithms work together to provide fresh, up‐to‐date information about vehicle traffic, enabling the proposed routing protocol to effectively withstand dynamic changes in VANET network topology. The proposed protocol has been developed over OMNET++ simulator, evaluated and compared with some other protocols. The simulation results showed that the proposed protocol provided better performance in terms of packet delivery rate and end‐to‐end delay than the EGyTAR and PBRP protocols. The packet delivery ratio of our proposal is approximately 75% and 6% higher than EGyTAR and PBRP, respectively, and the end‐to‐end delay of our protocol is reduced by 37% and 7%, respectively, compared with EGyTAR and PBRP for most scenarios.

Summary Road congestion and traffic jams are serious problems for drivers, causing them more delay in reaching their destinations. Motivated by these considerations, this article proposes an intelligent scheduling algorithm based on vehicular ad hoc networks (VANETs) and Cloud computing to schedule traffic lights to smooth road traffic and reduce waiting time on the road, called CCITL (cloud computing based intelligent traffic light protocol). In CCITL, we involve cloud computing by using conventional and vehicular clouds to have a global view of the road network and take advantage of the cloud computing capabilities to calculate the most appropriate traffic signal formulas and combinations with their phase durations in a dynamic way. This allows to ensure the fluidity of the traffic and the arrival at the destination in a short time while minimizing the waiting time on the different segments of the road network. Our proposed protocol has been developed and evaluated over OMNET++ simulator with the simulator of urban mobility (SUMO). The simulation results showed that CCITL greatly contributed to the alleviation of traffic congestion as well as to the reduction of the dwell time of vehicles in the different segments, thus reducing delays and waiting in intersections.

Summary A critical node is a sensor whose failure causes loss of connectivity and network fragmentation. In wireless sensor networks, the failure of a critical node, like the failure of all sensor nodes, can be caused by energy depletion or physical failure. To overcome the problem of failure of such nodes, this article proposes a fault‐tolerant strategy that allows a routing protocol to tolerate the failure of a critical node. The proposed strategy is carried out in two phases. In the first phase, a hybrid genetic algorithm with a local search heuristic called genetic algorithm‐critical node problem (GA‐CNP) is used to select the critical nodes and in the second phase, an algorithm called Aug‐CNP is involved to deal with the augmentation problem by deploying additional wireless edges to preserve network connectivity in case of critical node failure. Our proposal has been developed using the OMNET++ simulator, evaluated, and compared to the AODV protocol. The simulation results showed that the GA‐CNP algorithm selects the critical nodes whose failure can degrade the network lifetime with a rate of 40%. Moreover, the Aug‐CNP algorithm applied to the AODV protocol brings improvements in terms of network lifetime which reaches 22% compared to the traditional AODV protocol.

Summary Several geographic routing protocols have been proposed for data transmission in wireless multimedia sensor networks (WMSNs), in which forwarding decisions are made locally based on one‐hop neighborhood information of each sensor node. These routing protocols involve one of two routing strategies: distance‐based strategy (greedy) which selects the closest neighbor from the base station as next‐hop or direction‐based strategy (compass) that chooses the neighbor with the smallest angle deviation toward the base station as next‐hop. This article proposes a multipath geographic routing protocol for WMSNs that combines the two routing strategies while taking advantage of their benefits, called greedy‐compass geographic multipath routing (GCGM) protocol. In GCGM, for the selection of a neighbor as next‐hop, a weighting coefficient is associated to each of the two strategies. We performed extensive simulations using OMNeT++ simulator with different scenarios to illustrate the performance of our proposal with our proposed weight values and with various weight values. Simulation results showed that our proposal with the proposed weight values provides better performance compared to GCGM with fixed weight values in terms of several performance criteria. We also compared GCGM with other routing protocols. Simulation results showed that GCGM provides better performance compared to TIGMR, LQEAR, and AGEM.

Vehicular Fog Computing (VFC) is a paradigm of vehicular networks that has a set of advantages such as agility, efficiency, and reduced latency. The VFC is vulnerable to a variety of attacks, and existing security measures in traditional networks are not necessarily applicable to VFC. Among these attacks, we can find the Sybil attack that allows a vehicle to create multiple identities to perform malicious operations. In this paper, we propose a blockchain-based mechanism to detect Sybil attacks in VFC networks. The detection process consists of two levels; the first one is targeted toward the verification of the vehicle’s position by the FN using the Received Signal Strength Indicator (RSSI) technique. The FN delivers a position proof, if its position is valid, and stores it in the blockchain. At this point, the set of the obtained position proofs constitutes a trajectory. The second level is projected toward a comparison between the trajectories of the vehicles reporting an event. Two trajectories that pass through the same FNs at the same time, will be considered as Sybil trajectories. The objective of these two-level detections is to identify the Sybil attack in several attack scenarios performed by a powerful adversary. Our analysis shows that existing proposals cannot deal with such an adversary. Moreover, simulation results show the efficiency of our proposal in terms of communication, computation, and detection rate. Indeed, our system can reach a detection rate of 98% when the malicious vehicle generates several aliases simultaneously and sends position requests to the FN for each generated pseudonym.

Summary Wireless sensor networks (WSNs) are an interconnection between hundreds to thousands of geographically distributed sensor nodes often called motes. WSNs are deployed in various fields for collecting data; they are used in healthcare monitoring, weather service, civil and military applications, and so on. WSNs are faced with many challenges due to their lack of computational resources, restrained storage capacities, and limited energy resources. The apparition of Cloud computing technology with its many advantages led the idea of integration between these two technologies. In this article, we will present an overview of works related to the interconnection between WSNs to the Cloud. After analyzing the contents of the published works, we established their classification according to the subjects treated. Four items are therefore selected, namely storage and computation, security, application and finally integration for Internet of Things (IoT). This brief review of the literature shows that the development of WSNs‐Cloud interconnection solves the problem of minimizing energy consumption at the sensor level, the problem of data storage, as well as the problem of access to the medium.

Currently, the majority of research in the area of wireless sensor networks (WSNs) is directed towards optimizing energy use during itinerary planning by mobile agents (MAs). The route taken by the MA when migrating can get a significant effect on energy consumption and the lifespan of the network. Conversely, finding an ideal arrangement of Source Nodes (SNs) for mobile agents to visit could be a problematic issue. It is within this framework that this work focused on solving certain problems related to itinerary planning based on a multimobile agent (MMA) strategy in networks. The objective of our research was to increase the lifespan of sensor networks and to diminish the length of the data collection task. In order to achieve our objective, we proposed a new approach in WSNs, which took into consideration the criterion of an appropriate number of MAs, the criterion of the appropriate grouping of SNs, and finally the criterion of the optimal itinerary followed by each MA to visit all its SNs. Thus, we suggested an approach that may be classified as a centralized planning model where the itinerary schedule is entirely shaped by the base station (sink) which, unlike other approaches, is no longer constrained by energy consumption. A series of simulations to measure the performance of the new planning process was also carried out.

Summary Position‐based routing, also called geographic routing, is widely recognised as an efficient routing approach for highly dynamic and mobile networks as vehicular ad hoc networks (VANETs). In this kind of networks, the high‐speed mobility of vehicles causes rapid changes on the network topology measured with vehicles density, limited‐time communication links, link failures, etc. In the meantime, the need of location service is a key issue; indeed, it will allow finding the position of a target node in order to reach it with a message. Some theoretical studies have proposed location services based on sharing nodes informations in different ways with hierarchy mechanism or with distribution mechanism or with centralization process. This paper proposes a location service deployed on RSUs (Road Side Units) for unicast routing over VANETs in urban environment. The proposed approach is able to measure the connectivity of a route. We propose then a new metric called Link Connectivity (LC) which measures this connectivity. Additionally, we have implemented our proposal using OMNET++ simulator and we have conducted extensive simulations with various scenarios to evaluate its scalability and robustness against frequent topology changes. As a conclusion, the proposed mechanism provides significant performance improvements in terms of packet delivery ratio, end‐to‐end delay, and overhead when it is compared to some other known proposals.

Vehicular Ad-hoc networks (VANETs) are a specific class of Mobile Ad-hoc Networks made by vehicles communicating among themselves in roads in urban and rural environments. The well-known unicast routing protocols implemented for MANETs (Mobile Area Networks) are not suitable for VANETs due to high mobility. Routing over VANET is a challenging task due to highly dynamic network topology. In order to avoid a frequent communication link failure and reduce the communication overhead among mobile nodes, we implemented a new routing protocol based on measuring with accuracy road densities in a distributed manner. Each computed route is a list of roads (between two successive anchors). The aim is to built the route having the highest density composed by the density of each component road. In this paper we present a distributed algorithm which measures the density in a road by exchanging CDP (Control Data Packets) between a group of vehicles on a road. Each group is represented by a leader which is in charge of measuring the density periodically and send it to the next group leader. The last group leader will have the actual density at each period. This protocol has been developed over the simulator OMNET++. We have conducted extensive simulations with different scenarios to evaluate the scalability of the approach and the robustness against frequent topology changes. The evaluation stated that our proposal has higher performance measures than the existing routing protocols as EGyTAR. We have evaluated packet delivery ratio, end-to-end delay and overhead.

The geographic routing protocols show a great routing performance compareed to topology-based routing protocols in the highly dynamic and the large scale networks such as Vehicular Ad hoc NETworks (VANETs).However, these routing protocols suffer from radio obstacles in urban environments which leads to frequent links disconnection. One alternative to bypass this specific drawback is to benefit from the urban topology and vehicular traffic information in order to find paths with higher connectivity. In this paper, we propose a new routing protocol based on a novel distributed group information, able to provide an advanced decision when choosing the intersections by which the packets must pass to reach their destination. Our proposed protocol has been implemented over OMNET++ simulator. We have conducted simulations which have shown that our proposal provides interesting performances in terms of packet delivery ratio and end-to-end delay compared with GyTAR [1] and EGyTAR [2] protocols.

Vehicular Ad Hoc Networks (VANETs) have received a great interest either form academia and from industry since a decade because of their potential for Cooperative-Intelligent Transportation Systems (C-ITS). Then many issues have been investigated in order to improve performances of such networks as packet delay, throughput,.. As a consequence, such systems could participate in the future to reduce accidents on the roads and traffic jams. Unicast forwarding over VANETs are usually geographic for one main reason: the nodes are dynamic, then their location change in a continous manner and the network topology is never stable. As a consequence, packet loss is a serious issue which has to be considered with care. Among known solutions to solve this issue, we have to find appropriate metrics to measure paths to be used in order to forward packet in the network. This paper aims to propose a new metrics called Link Connectivity (LC) in order to find the path with the highest connectivity between the source vehicle and the destination vehicle. Then this metrics is a basis for a unicast routing protocol over VANETs in city environment. The proposed approach is able to find the path with higher connectivity in urban environments which guarantees a high packet delivery. This metric has been integrated into a greedy based routing algorithm which has been developed over the simulator OMNET++ and a comparison to the eGyTAR [9] (which is an extension to GyTAR protocol [6]) is discussed We have conducted extensive simulations with different scenarios to evaluate the scalability of the approach and the robustness against frequent topology changes. As a conclusion, we have observed that this metrics has a positive impact on some performance indicators as packet delivery ratio, end-to-end delay and overhead compared to eGyTAR protocol.

Routing messages over vehicular ad hoc networks (VANETs) is usually achieved through geographic routing protocols. In such networks, the vehicle dynamics causes rapid changes on the vehicle density and the communication links. In order to be efficient to route messages from a vehicle to another, we need to locate each node (its position), this is achieved by a location service. This study works on simple location service adapted for unicast routing over VANETs in city environment. This service is able to find a route from a route from a source to the destination and this route is the one passing through the most dense path.. We have implemented our proposal on the OMNET++ simulator and we have conducted extensive simulations in different scenarios to evaluate its scalability and robustness against frequent topology changes. The results obtained have shown that our proposed protocol provides significant improvements in terms of packet delivery ratio, end-to-end delay and overhead compared to EGyTAR protocol.