Hybrid-Vehfog: A Robust Approach for Reliable Dissemination of Critical Messages in Connected Vehicles

Vehicular Ad-hoc Networks (VANET) enable efficient communication between vehicles with the aim of improving road safety. However, the growing number of vehicles in dense regions and obstacle shadowing regions like Manhattan and other downtown areas leads to frequent disconnection problems resulting in disrupted radio wave propagation between vehicles. To address this issue and to transmit critical messages between vehicles and drones deployed from service vehicles to overcome road incidents and obstacles, we proposed a hybrid technique based on fog computing called Hybrid-Vehfog to disseminate messages in obstacle shadowing regions, and multi-hop technique to disseminate messages in non-obstacle shadowing regions. Our proposed algorithm dynamically adapts to changes in an environment and benefits in efficiency with robust drone deployment capability as needed. Performance of Hybrid-Vehfog is carried out in Network Simulator (NS-2) and Simulation of Urban Mobility (SUMO) simulators. The results showed that Hybrid-Vehfog outperformed Cloud-assisted Message Downlink Dissemination Scheme (CMDS), Cross-Layer Broadcast Protocol (CLBP), PEer-to-Peer protocol for Allocated REsource (PrEPARE), Fog-Named Data Networking (NDN) with mobility, and flooding schemes at all vehicle densities and simulation times

Models and Performance of VANET based Emergency Braking

The network research community is working in the field of automotive to provide VANET based safety applications to reduce the number of accidents, deaths, injuries and loss of money. Several approaches are proposed and investigated in VANET literature, but in a completely network-oriented fashion. Most of them do not take into account application requirements and no one considers the dynamics of the vehicles. Moreover, message repropagation schemes are widely proposed without investigating their benefits and using very complicated approaches. This technical report, which is derived from the Master Thesis of Michele Segata, focuses on the Emergency Electronic Brake Lights (EEBL) safety application, meant to send warning messages in the case of an emergency brake, in particular performing a joint analysis of network requirements and provided application level benefits. The EEBL application is integrated within a Collaborative Adaptive Cruise Control (CACC) which uses network-provided information to automatically brake the car if the driver does not react to the warning. Moreover, an information aggregation scheme is proposed to analyze the benefits of repropagation together with the consequent increase of network load. This protocol is compared to a protocol without repropagation and to a rebroadcast protocol found in the literature (namely the weighted p-persistent rebroadcast). The scenario is a highway stretch in which a platoon of vehicles brake down to a complete stop. Simulations are performed using the NS_3 network simulation in which two mobility models have been embedded. The first one, which is called Intelligent Driver Model (IDM) emulates the behavior of a driver trying to reach a desired speed and braking when approaching vehicles in front. The second one (Minimizing Overall Braking Induced by Lane change (MOBIL)), instead, decides when a vehicle has to change lane in order to perform an overtake or optimize its path. The original simulator has been modified by - introducing real physical limits to naturally reproduce real crashes; - implementing a CACC; - implementing the driver reaction when a warning is received; - implementing different network protocols. The tests are performed in different situations, such as different number of lanes (one to five), different average speeds, different network protocols and different market penetration rates and they show that: - the adoption of this technology considerably decreases car accidents since the overall average maximum deceleration is reduced; - network load depends on application-level details, such as the implementation of the CACC; - VANET safety application can improve safety even with a partial market penetration rate; - message repropagation is important to reduce the risk of accidents when not all vehicles are equipped; - benefits are gained not only by equipped vehicles but also by unequipped ones

Encounter gossip: a high coverage broadcast protocol for MANET

PhD ThesisMobile Ad-hoc Networks (MANETs) allow deployment of mobile wireless devices or nodes in a range of environments without any fixed infrastructure and hence at a minimal setup cost. Broadcast support that assures a high coverage (i.e., a large fraction of nodes receiving a broadcast) is essential for hosting user applications, and is also non-trivial to achieve due to the nature of devices and mobility. We propose Encounter Gossip, a novel broadcast protocol, which holds minimal state and is unaware of network topology. Coverage obtained can be made arbitrarily close to 1 at a moderate cost of extra message tra c, even in partition-prone networks. Under certain simplifying assumptions, it is shown that a high coverage is achieved by making a total of O(n ln n) broadcasts, where n is the number of nodes, and the time to propagate a message is O(ln n). The e ect of various network parameters on the protocol performance is examined. We then propose modifications to minimise the number of redundant transmissions without compromising the achieved coverage. Two approaches are pursued: timer based and history based. The e ectiveness of each of these approaches is assessed through an extensive set of simulation experiments in the context of two mobility models. Specifically, we introduce a new heuristic alpha policy which achieves significant reduction in redundancy with negligible reduction in coverage. A generalisation to multiple broadcasts proceeding in parallel is proposed and the protocol is refined to reduce problems that can occur due to the effects of high mobility when transmitting a large number of messages. Finally, we implement and validate Encounter Gossip in the context of a real-life mobile ad-hoc network. All these investigations suggest that the protocol, together with the proposed modifications and re nements, is suited to MANETs of varying degrees of node densities and speeds

Detecting Non-Line of Sight to Prevent Accidents in Vehicular Ad hoc Networks

There are still many challenges in the field of VANETs that encouraged researchers to conduct further investigation in this field to meet these challenges. The issue pertaining to routing protocols such as delivering the warning messages to the vehicles facing Non-Line of Sight (NLOS) situations without causing the storm problem and channel contention, is regarded as a serious dilemma which is required to be tackled in VANET, especially in congested environments. This requires the designing of an efficient mechanism of routing protocol that can broadcast the warning messages from the emergency vehicles to the vehicles under NLOS, reducing the overhead and increasing the packet delivery ratio with a reduced time delay and channel utilisation. The main aim of this work is to develop the novel routing protocol for a high-density environment in VANET through utilisation of its high mobility features, aid of the sensors such as Global Positioning System (GPS) and Navigation System (NS). In this work, the cooperative approach has been used to develop the routing protocol called the Co-operative Volunteer Protocol (CVP), which uses volunteer vehicles to disseminate the warning message from the source to the target vehicle under NLOS issue; this also increases the packet delivery ratio, detection of NLOS and resolution of NLOS by delivering the warning message successfully to the vehicle under NLOS, thereby causing a direct impact on the reduction of collisions between vehicles in normal mode and emergency mode on the road near intersections or on highways. The cooperative approach adopted for warning message dissemination reduced the rebroadcast rate of messages, thereby decreasing significantly the storm issue and the channel contention. A novel architecture has been developed by utilising the concept of a Context-Aware System (CAS), which clarifies the OBU components and their interaction with each other in order to collect data and take the decisions based on the sensed circumstances. The proposed architecture has been divided into three main phases: sensing, processing and acting. The results obtained from the validation of the proposed CVP protocol using the simulator EstiNet under specific conditions and parameters showed that performance of the proposed protocol is better than that of the GRANT protocol with regard to several metrics such as packet delivery ratio, neighbourhood awareness, channel utilisation, overhead and latency. It is also successfully shown that the proposed CVP could detect the NLOS situation and solves it effectively and efficiently for both the intersection scenario in urban areas and the highway scenario

Mobile Ad-Hoc Networks

Being infrastructure-less and without central administration control, wireless ad-hoc networking is playing a more and more important role in extending the coverage of traditional wireless infrastructure (cellular networks, wireless LAN, etc). This book includes state-of the-art techniques and solutions for wireless ad-hoc networks. It focuses on the following topics in ad-hoc networks: vehicular ad-hoc networks, security and caching, TCP in ad-hoc networks and emerging applications. It is targeted to provide network engineers and researchers with design guidelines for large scale wireless ad hoc networks

Design and evaluation of protocols for wireless networks taking into account the interaction between transport and network layers.

We recognized two important shortcomings of the current TCP protocol: misinterpretation of delayed acknowledgments and competition among different TCP flows. In this dissertation, we propose to address these two issues by a use of novel protocol that uses immediate and delayed acknowledgment schemes and provides a coordination mechanism among independent TCP flows. We also address certain important issues that are related to the implementation of our proposed protocol: can we maintain the end-to-end semantics of TCP? Are there additional benefits that can be harvested if intermediate nodes with TCP protocol can be used? (Abstract shortened by UMI.)The Transmission Control Protocol (TCP) provides end-to-end data reliability and is the primary transport layer protocol for many applications such as email, web access, and file transfer. There has been a plethora of research activity that aims to improve the performance of TCP both in wired and wireless networks. Protocols for the computer networks have been very structured and layered to allow for easier upgrades and maintenance. The network layer protocol (e.g. IP) is independent and below the transport layer protocol (e.g. TCP). Our main goal in this dissertation is to examine the interaction and dynamics between the network layer protocols and TCP in the wireless environment.Towards this goal, we examined the network layer protocols in one-hop wireless (e.g. cellular networks) and multi-hop wireless, e.g. distributed Wi-Fi (Wireless Fidelity) networks. For each of these networks we, for the first time, propose transport layer protocols that take into account the interaction between the network layer and transport layer. For the one-hop wireless networks we have investigated analytical methods to determine the buffer requirements at base stations and estimate disruption time which is the time between two packet arrivals at the mobile host. We will show that the estimation of buffer requirements and disruption time is not only dependent on the wireless TCP scheme used, but also its interaction with the underlying network protocol. We also propose a comprehensive study of the effectiveness of wireless TCP and network protocols taking into account different networking environments that is decided on many factors such as mobility of senders and receivers, simplex and duplex communication among communicating peers, connection oriented and connection less communication at the network layer, rerouting schemes used after movement, and with and without hint handoff schemes

Analyzing the Performances of WSNs Routing Protocols in Grid-Based Clustering

Nowadays wireless sensor networks (WSNs) became a modern research theme owing to the various applications range in assorted fields. Clustering considered from the more efficient techniques for solving the WSN drawbacks of energy consumption. The grid-based cluster has definitely done its effectiveness, especially for networks with high dynamic, all nodes in the clusters represented and the values of data are collected from sensor nodes by the cluster head (CH). For balancing the energy consumption with network traffic, the (CH) must be exchanged between all sensor nodes and the cluster size ought to be closely determined at different network parts. The most important issues for WSN is developing an energy-efficient algorithm by Grid-based clustering for improving the network lifetime, reduced cost, and increasing the network reliability. The equipment of the sensor nodes attached with limited power sources, the Grid-Based Clustering algorithm (GBC), therefore efficiently employing the energy of the sensor nodes can preserve a prolongation of the network lifetime. The network Performances of the sensor node are largely based on the application of the routing protocols, three routing protocols OLSR, AODV, and DSR in grid-based cluster WSN are evaluated by using Qualnet simulator. The results show DSR outperforms in the range of throughput, and end to end delay, while the AODV can be considered as the best in the package delivery ratio PDR with compared to others

Traffic locality oriented route discovery algorithms for mobile ad hoc networks

There has been a growing interest in Mobile Ad hoc Networks (MANETs) motivated by the advances in wireless technology and the range of potential applications that might be realised with such technology. Due to the lack of an infrastructure and their dynamic nature, MANETs demand a new set of networking protocols to harness the full benefits of these versatile communication systems. Great deals of research activities have been devoted to develop on-demand routing algorithms for MANETs. The route discovery processes used in most on-demand routing algorithms, such as the Dynamic Source Routing (DSR) and Ad hoc On-demand Distance Vector (AODV), rely on simple flooding as a broadcasting technique for route discovery. Although simple flooding is simple to implement, it dominates the routing overhead, leading to the well-known broadcast storm problem that results in packet congestion and excessive collisions. A number of routing techniques have been proposed to alleviate this problem, some of which aim to improve the route discovery process by restricting the broadcast of route request packets to only the essential part of the network. Ideally, a route discovery should stop when a receiving node reports a route to the required destination. However, this cannot be achieved efficiently without the use of external resources; such as GPS location devices. In this thesis, a new locality-oriented route discovery approach is proposed and exploited to develop three new algorithms to improve the route discovery process in on-demand routing protocols. The proposal of our algorithms is motivated by the fact that various patterns of traffic locality occur quite naturally in MANETs since groups of nodes communicate frequently with each other to accomplish common tasks. Some of these algorithms manage to reduce end-to-end delay while incurring lower routing overhead compared to some of the existing algorithms such as simple flooding used in AODV. The three algorithms are based on a revised concept of traffic locality in MANETs which relies on identifying a dynamic zone around a source node where the zone radius depends on the distribution of the nodes with which that the source is “mostly” communicating. The traffic locality concept developed in this research form the basis of our Traffic Locality Route Discovery Approach (TLRDA) that aims to improve the routing discovery process in on-demand routing protocols. A neighbourhood region is generated for each active source node, containing “most” of its destinations, thus the whole network being divided into two non-overlapping regions, neighbourhood and beyond-neighbourhood, centred at the source node from that source node prospective. Route requests are processed normally in the neighbourhood region according to the routing algorithm used. However, outside this region various measures are taken to impede such broadcasts and, ultimately, stop them when they have outlived their usefulness. The approach is adaptive where the boundary of each source node’s neighbourhood is continuously updated to reflect the communication behaviour of the source node. TLRDA is the basis for the new three route discovery algorithms; notably: Traffic Locality Route Discovery Algorithm with Delay (TLRDA D), Traffic Locality Route Discovery Algorithm with Chase (TLRDA-C), and Traffic Locality Expanding Ring Search (TL-ERS). In TLRDA-D, any route request that is currently travelling in its source node’s beyond-neighbourhood region is deliberately delayed to give priority to unfulfilled route requests. In TLRDA-C, this approach is augmented by using chase packets to target the route requests associated with them after the requested route has been discovered. In TL-ERS, the search is conducted by covering three successive rings. The first ring covers the source node neighbourhood region and unsatisfied route requests in this ring trigger the generation of the second ring which is double that of the first. Otherwise, the third ring covers the whole network and the algorithm finally resorts to flooding. Detailed performance evaluations are provided using both mathematical and simulation modelling to investigate the performance behaviour of the TLRDA D, TLRDA-C, and TL-ERS algorithms and demonstrate their relative effectiveness against the existing approaches. Our results reveal that TLRDA D and TLRDA C manage to minimize end-to-end packet delays while TLRDA-C and TL-ERS exhibit low routing overhead. Moreover, the results indicate that equipping AODV with our new route discovery algorithms greatly enhance the performance of AODV in terms of end to end delay, routing overhead, and packet loss

A survey on probabilistic broadcast schemes for wireless ad hoc networks

Broadcast or flooding is a dissemination technique of paramount importance in wireless ad hoc networks. The broadcast scheme is widely used within routing protocols by a wide range of wireless ad hoc networks such as mobile ad hoc networks, vehicular ad hoc networks, and wireless sensor networks, and used to spread emergency messages in critical scenarios after a disaster scenario and/or an accidents. As the type broadcast scheme used plays an important role in the performance of the network, it has to be selected carefully. Though several types of broadcast schemes have been proposed, probabilistic broadcast schemes have been demonstrated to be suitable schemes for wireless ad hoc networks due to a range of benefits offered by them such as low overhead, balanced energy consumption, and robustness against failures and mobility of nodes. In the last decade, many probabilistic broadcast schemes have been proposed by researchers. In addition to reviewing the main features of the probabilistic schemes found in the literature, we also present a classification of the probabilistic schemes, an exhaustive review of the evaluation methodology including their performance metrics, types of network simulators, their comparisons, and present some examples of real implementations, in this paper