A holistic framework to improve message delivery in vehicular ad-hoc networks

Vehicular Ad-hoc Networks (VANETs) are wireless communication networks for vehicles that do not require any fixed or central infrastructure. It forms an important part of the intelligent transport system (ITS) which is the convergence of telecommunications, computing and wireless systems with the aim of improving transportation regarding efficiency, safety and management. In addition to the uses of ITS, VANETs will contribute in service access, cooperative driving, entertainment and navigation for cars of the future. Due to the varied use of VANETs, it becomes slightly cumbersome having a "one-fits-all" solution to challenges facing message dissemination in VANETs. While some applications might require a fast and reliable way of disseminating messages amongst members of the network, other applications might be more delay-tolerant without adding extra risks to the dependents of such application. Data dissemination methods are therefore important aspects of VANET that ensure messages are delivered to areas beyond the scope of the originating node. However, several types of research have shown that message propagation for each geographical route is unique to that route, owing to the number of network participants, their speed, and distribution of objects on that route. Many research designs do not consider the vehicles and their traffic characteristics and as such vehicular ad-hoc networks are under-utilised. One of the problems present in the emerging field of vehicular communications is that of optimally disseminating messages within the network to support services such as collision warnings, traffic management, and driverless vehicles amongst others. This problem is a unique research area which involves the entire network and its ability to support the efficient propagation of data. Message dissemination in VANETs could be viewed as routing on much higher macroscopic level, however, the techniques usually applied to data routing on a microscopic level does not utilise available data to efficiently disseminate messages within a vehicular ad-hoc network. Some work done in literature addresses a few constraints at a time; for example a focus on junctions, thereby ignoring vast areas of the wireless network which could have been otherwise used to improve the overall ability to efficiently deliver messages within the road network. For this reason, this thesis investigates the effects of several vehicular factors, how these factors affect the quality of the wireless network on each road, and how this knowledge is advantageous in improving the delivery of messages from a source to its destination within a vehicular ad-hoc network. In proposing a solution that uses otherwise largely ignored road traffic data to improving efficient message delivery, a holistic framework that utilises road traffic information in a unique way is presented. The quality of a wireless network for each road in terms of packets delivered is seen to be influenced by the number of vehicles and their speed which is seen to be unique for each road segment; therefore, allowing the generation of a wireless packet delivery map offline (wireless network map) based on varying number of vehicles and speeds. Current road traffic data can then be compared against the wireless map in order to determine which routes have good network quality and hence the ability to support better message dissemination. This framework is also aimed at helping to fully utilise the VANET bandwidth available by reducing network noise caused by multiple retransmissions of nodes in the network by picking the right path and using only the furthest node on each path. It aims to reduce messages delivery failure, reduce delays in the message delivery where possible and improve the utilisation of vehicles as communication nodes and relays. The Framework for Improving Message Delivery in VANETs (FIMDEV) proposed in this thesis shows the benefit of using the wireless communication database information processed by each vehicle to support message delivery from source to destination within the VANET. Experiments show improved overall packet delivery ratio when compared to standalone routing protocols as FIMDEV uses the wireless network database along with a set of rules for propagating messages within the network

A Simple and Robust Dissemination Protocol for VANETs

Several promising applications for Vehicular Ad-hoc Networks (VANETs) exist. For most of these applications, the communication among vehicles is envisioned to be based on the broadcasting of messages. This is due to the inherent highly mobile environment and importance of these messages to vehicles nearby. To deal with broadcast communication, dissemination protocols must be defined in such a way as to (i) prevent the so-called broadcast storm problem in dense networks and (ii) deal with disconnected networks in sparse topologies. In this paper, we present a Simple and Robust Dissemination (SRD) protocol that deals with these requirements in both sparse and dense networks. Its novelty lies in its simplicity and robustness. Simplicity is achieved by considering only two states (cluster tail and non- tail) for a vehicle. Robustness is achieved by assigning message delivery responsibility to multiple vehicles in sparse networks. Our simulation results show that SRD achieves high delivery ratio and low end-to-end delay under diverse traffic conditions

Routing And Communication Path Mapping In VANETS

Vehicular ad-hoc network (VANET) has quickly become an important aspect of the intelligent transport system (ITS), which is a combination of information technology, and transport works to improve efficiency and safety through data gathering and dissemination. However, transmitting data over an ad-hoc network comes with several issues such as broadcast storms, hidden terminal problems and unreliability; these greatly reduce the efficiency of the network and hence the purpose for which it was developed. We therefore propose a system of utilising information gathered externally from the node or through the various layers of the network into the access layer of the ETSI communication stack for routing to improve the overall efficiency of data delivery, reduce hidden terminals and increase reliability. We divide route into segments and design a set of metric system to select a controlling node as well as procedure for data transfer. Furthermore we propose a system for faster data delivery based on priority of data and density of nodes from route information while developing a map to show the communication situation of an area. These metrics and algorithms will be simulated in further research using the NS-3 environment to demonstrate the effectiveness

Routing in a many-to-one communication scenario in a realistic VDTN

In this paper, we evaluate and compare the performance of different routing protocols in a many-to-one communication within a Vehicular Delay Tolerant Network (VDTN). Seven groups with three stationary sensor nodes sense the temperature, humidity and wind speed and send these data to a stationary destination node that collect them for statistical and data analysis purposes. Vehicles moving in Tirana city roads in Albania during the opportunistic contacts will exchange the sensed data to destination node. The simulations are conducted with the Opportunistic Network Environment (ONE) simulator. For the simulations we considered two different scenarios where the distance of the source nodes from the destination is short and long. For both scenarios the effect of node density, ttl and node movement model is evaluated. The performance is analyzed using delivery probability, overhead ratio, average latency, average number of hops and average buffer time metrics. The simulation results show that the increase of node density increases the delivery probability for all protocols and both scenarios, and better results are achieved when shortest-path map-based movement model is used. The increase of ttl slightly affects the performance of all protocols. By increasing the distance between source nodes and destination node, delivery probability is decreased almost 10% for all protocols, the overhead for sprayandwait protocol does not change, but for other protocols is slightly increased and the average number of hops and average latency is increased.Peer ReviewedPostprint (author's final draft