Inter-vehicular communication using wireless ad-hoc networks.

This thesis proposes a new routing algorithm to allow communication in highly mobile, wireless ad-hoc networks, which in nature are wireless and infrastructureless. In motorway environments, the topology of the network changes frequently and unpredictable due to the mobility of the nodes. We investigate a new reactive routing algorithm based in location information in the context of inter-vehicular communication. In such a scenario, the originator of the communication does not know the position of its communication partner in advance. Rapid topology changes and scarce bandwidth prevent the nodes from exchanging positions regularly throughout the network. Therefore, we focus on reactive algorithms and explore several mechanisms limiting the flooding of discoveries location packets. The originator of a message uses scoped and controlled flooding to reach the destination. The receivers of the flooded message use their knowledge of the local environment to decide whether they can reach the intended destination of the message or retransmit the message to their neighbours. To evaluate our communication algorithm, we first validate it in a small scale network with the results o f a test bed. Then for large scale networks, our protocol is compared with the models of two prominent reactive routing algorithms: Ad-Hoc On-Demand Distance Vector (AODV) and Dynamic Source Routing (DSR) on a multi-lane rectangular and circular dual carriageway representative of city and motorway driving. Finally, our algorithm is analysed on a multi-lane circular carriageway representative of a six lane motorway driving with one location-based routing algorithm: Greedy Perimeter Stateless Routing (GPSR). The mobility of the vehicles on a Motorway using a Microscopic traffic model developed in OPNET has been used to evaluate the performance of each protocol in terms of: Route Discovery Time (RDT), End to End Delay (EED), Routing Overhead (RO), Overhead (O), Routing Load (RL) and Delivery Ratio (DR)

Performance Evaluation of Vehicular Ad Hoc Networks using simulation tools

Recent studies demonstrate that the routing protocol performances in vehicular networks can improve using dynamic information on the traffic conditions. WSNs (Wireless Sensor Networks) and VANETs (Vehicular Ad Hoc Networks) are exactly related with this statement and represent the trend of wireless networks research program in the last years. In this context, a new type of network has been developed: in fact, HSVN (Hybrid Sensor and Vehicular Network) let WSNs and VANETs cooperate through dynamic information data exchanges with the aim to improve road safety, and especially to warn the driver and the co-pilot of any event occurred in the road ahead, such as traffic jam, accidents or bad weather. The results will be immediate: less accidents means more saved lives, less traffic means a pollution decrease, and from the technological point of view, this communication protocol will open the door to attractive services, such as downloading of multimedia services or internet browsing, that means easier, safer and more comfortable trips. It is out of doubt that speaking about cars and road technology developments, the market and the interests about this field increase exponentially. Recent projects such as CVIS [1] and COMeSafety [2], focused on improving the road driving, and are the concrete demonstration that this entire context can get soon very close to reality. Owing to their peculiar characteristics, VANETs require the definition of specific networking techniques, whose feasibility and performance are usually tested by means of simulation. Starting from this point, this project will present a HSVN platform, and will also introduce and evaluate a communication protocol between VANETs and WSNs using the NCTUns 6.0 [3] simulator. We will particularly analyze the performances of 2 types of Scenarios developed during our project. Both of them are in an urban context, but we will extract different useful results analyzing the packet losses, the throughput and the end-to-end packet delay

Performance Evaluation of Vehicular Ad Hoc Networks using simulation tools

Recent studies demonstrate that the routing protocol performances in vehicular networks can improve using dynamic information on the traffic conditions. WSNs (Wireless Sensor Networks) and VANETs (Vehicular Ad Hoc Networks) are exactly related with this statement and represent the trend of wireless networks research program in the last years. In this context, a new type of network has been developed: in fact, HSVN (Hybrid Sensor and Vehicular Network) let WSNs and VANETs cooperate through dynamic information data exchanges with the aim to improve road safety, and especially to warn the driver and the co-pilot of any event occurred in the road ahead, such as traffic jam, accidents or bad weather. The results will be immediate: less accidents means more saved lives, less traffic means a pollution decrease, and from the technological point of view, this communication protocol will open the door to attractive services, such as downloading of multimedia services or internet browsing, that means easier, safer and more comfortable trips. It is out of doubt that speaking about cars and road technology developments, the market and the interests about this field increase exponentially. Recent projects such as CVIS [1] and COMeSafety [2], focused on improving the road driving, and are the concrete demonstration that this entire context can get soon very close to reality. Owing to their peculiar characteristics, VANETs require the definition of specific networking techniques, whose feasibility and performance are usually tested by means of simulation. Starting from this point, this project will present a HSVN platform, and will also introduce and evaluate a communication protocol between VANETs and WSNs using the NCTUns 6.0 [3] simulator. We will particularly analyze the performances of 2 types of Scenarios developed during our project. Both of them are in an urban context, but we will extract different useful results analyzing the packet losses, the throughput and the end-to-end packet delay

Quality of service and security in future mobile technologies

Future networks will comprise a wide variety of wireless networks. Users will expect to be always connected from any location, and, as users move, connections will be switched to available networks using vertical handover techniques. The current approach of the operators is a centralized network, and the mobility management is done at the infrastructure level. The decentralized mobility management is another approach developed in many researches, however, not widely deployed. We are interested in this type of decentralized mobility management, especially in a highly dynamic environment when the network topology changes frequently. We choose a particular case study, Vehicular Ad-hoc Networks (VANETs), which are a new emerging network technology derived from ad-hoc networks and are an example of future networks. In the field of Intelligent Transportation Systems (ITS), communications without a wire between vehicles (V2V) appear as an accident prevention solution offering a wider vision than conventional sensors. By linking vehicles to telecommunications network (V2I), new perspectives are offered both passengers and driver with conventional communication applications such as access Internet, e-learning, games or chat. This means that future mobile networks like VANETs will have to integrate communications, mobility, Quality of Service (QoS) and security. We mainly interested in three issues: mobility, QoS and security. These three issues are intrinsic to vehicles on motorway networks. We need to simultaneously manage QoS and security while taking into account users mobility. In this thesis, we propose to contribute on how to improve security without degrading the quality of service QoS in a highly mobile environment as VANETs networks. To answer this research question, we use simulations and experiments. Simulation using Network Simulator 2 (NS2) will be used to show that security schemes have significant impacts on the throughput QoS, and our proposed schemes can substantially improve the effective secure throughput with cooperative communications

Previous hop routing: exploiting opportunism in VANETs

Routing in highly dynamic wireless networks such as Vehicular Ad-hoc Networks (VANETs) is a challenging task due to frequent topology changes. Sustaining a transmission path between peers in such network environment is difficult. In this thesis, Previous Hop Routing (PHR) is poposed; an opportunistic forwarding protocol exploiting previous hop information and distance to destination to make the forwarding decision on a packet-by-packet basis. It is intended for use in highly dynamic network where the life time of a hop-by-hop path between source and destination nodes is short. Exploiting the broadcast nature of wireless communication avoids the need to copy packets, and enables redundant paths to be formed. To save network resources, especially under high network loads, PHR employs probabilistic forwarding. The forwarding probability is calculated based on the perceived network load as measured by the arrival rate at the network interface. We evaluate PHR in an urban VANET environment using NS2 (for network traffic) and SUMO (for vehicular movement) simulators, with scenarios configured to re ect real-world conditions. The simulation scenarios are configured to use two velocity profiles i.e. Low and high velocity. The results show that the PHR networks able to achieve best performance as measured by Packet Delivery Ratio (PDR) and Drop Burst Length (DBL) compared to conventional routing protocols in high velocity scenarios

Mecanismos de facturação segura em redes auto-organizadas

Mestrado em Engenharia Electrónica e TelecomunicaçõesAs redes ad-hoc e as redes auto-organizadas constituem uma área de investigação com grande interesse. Estas redes são uteis em cenários onde seja necessária uma rede de baixo custo, elevada adaptabilidade e reduzido tempo de criação. As redes infra-estruturadas, tendo uma gestão centralizada, estão agora a começar a adoptar os conceitos de redes autoorganizadas nas suas arquitecturas. Ao contrário dos sistemas centralizados, redes auto-organizadas requerem que todos os terminais participantes operem de acordo com o melhor interesse da rede. O facto de, em redes ad-hoc, os equipamentos possuírem recursos limitados, pôe em causa este requisito levando a comportamentos egoístas. Este comportamento é espectavel criando problemas nas redes auto-organizativas, ameaçando o funcionamento de uma rede inteira. Algumas propostas foram ja criadas de modo a motivar a sua utilização correcta. Destas, algumas são baseadas em trocas de credito entre utilizadores, outras preveêm a existência de entidades gestoras de creditos. Estas ultimas propostas, que irão ser o foco desta dissertação, permitem a facil integração de redes ad-hoc com redes infra-estruturadas e geridas por um operador. Este trabalho descreve o estado da arte actual e, com algum detalhe, os métodos utilizados e as solucões relevantes para esta area. São propostas duas novas soluções de taxação para estas redes. Ambas as soluções possibilitam a integração das redes com metodos de taxação habituais em redes geridas por operadores. Para além disto, a motivação à participaçãao é aumentada através de incentivos ao encaminhamento de pacotes. Todos os processos são criptograficamente seguros através da utilização de métodos standard como DSA sobre Curvas Elípticas e funções de síntese robustas. As soluções propostas são descritas analiticamente e analisadas, sendo os os resultados obtidos comparados com outra proposta do estado da arte. Um exaustivo trabalho de simulação é igualmente descrito de forma a avaliar as soluções em cenários mais complexos. Os resultados obtidos em simulação são avaliados tendo em conta a variação de várias métricas como mobilidade, carga na rede, protocolo de encaminhamento e protocolo de transporte. No final, a arquitectura, implementação e resultados obtidos com uma implementação real de uma das propostas e os seus resultados analisados.Self-organised and ad-hoc networks are an area with an existing large research community. These networks are much useful in scenarios requiring a rapidly deployed, low cost and highly adaptable network. Recently, infrastructure networks, which are managed in a much centralised form, are starting to introduce concepts of self-organised networks in its architecture. In opposition to centralised systems, self-organisation creates the necessity for all nodes to behave according to the best interest of the network. The fact that in many ad-hoc networks nodes have scarce resources poses some threats to this requirement. As resources decreases, such as battery or wireless bandwidth, nodes can start acting selfishly. This behaviour is known to bring damage to self-organised networks and threatens the entire network. Several proposals were made in order to promote the correct usage of the network. Some proposals are based on local information and direct credit exchange while others envision the existence of a central bank. The later solutions are further elaborated in this thesis, as they make possible integration of ad-hoc network with operator driven infrastructures. This work presents the current state-of-the-art on the area providing a detailed insight on the methods adopted by each solution presented. Two novel solutions are proposed providing charging support for integrated ad-hoc networks. Both solutions provide means of integration with standard management methods found in operator networks. Also, node´s motivation is increased through the reward of nodes forwarding data packets. The entire process is cryptographically secure, making use of standard methods such as Elliptic Curve DSA and strong digest functions. The solutions proposed are described and analysed analytically, comparing the results with other state-of-the-art proposals. Extensive simulation work is also presented which furthers evaluates the solutions in complex scenarios. Results are obtained from these scenarios and several metrics are evaluated taking in consideration mobility, network load, routing protocol and transport protocol. The architecture and results obtained with a real implementation are finally presented and analysed

Information collection algorithm for vehicular ad-hoc networks (application domain: Urban Traffic Wireless Vehicular Ad-Hoc Networks (VANETs))

Vehicle to vehicle communication (V2VC) is one of the modern approaches for exchanging and generating traffic information with (yet to be realized) potential to improve road safety, driving comfort and traffic control. In this research, we present a novel algorithm which is based on V2V communication, uses in-vehicle sensor information and in collaboration with the other vehicles' sensor information can detect road conditions and determine the geographical area where this road condition exists – e.g. geographical area where there is traffic density, unusual traffic behaviour, a range of weather conditions (raining), etc. The algorithms' built-in automatic geographical restriction of the data collection, aggregation and dissemination mechanisms allows warning messages to be received by any car, not necessarily sharing the identified road condition, which may then be used to identify the optimum route taken by the vehicle e.g. avoid bottlenecks or dangerous areas including accidents or congestions on their current routes. This research covers the middle ground between MANET [1] and collaborative data generation based on knowledge granularity (aggregation). It investigates the possibility of designing, implementing and modelling of the functionality of an algorithm (as part of the design of an intelligent node in an Intelligent Transportation System - ITS) that ensures active participation in the formation, routing and general network support of MANETs and also helps in-car traffic information and real-time control generation and distribution. The work is natural extension of the efforts of several large EU projects like DRIVE [2], GST [3] and SAFESPOT [4]

A pervasive prediction model for vehicular ad-hoc network (VANET)

The growth of city traffic has contributed to severe traffic congestion and traffic accidents in the most of the cities in the world. Since people’s travel demand rise at a rate usually greater than the addition of road capacity to lead many other issues, such as environmental problems and the quality of life. Intelligent Transportation System (ITS) is committed to solving the worsening traffic problems. Wide deployment of such ITS can eventually provide more dynamic, real-time and efficient solutions to transportation problems. ITS uses a variety of high technologies, especially electronic information technology and data communications technology to improve road traffic efficiency, road traffic safety and environmental protection. A number of researchers have depended on the wireless mobile communication to improve data collection and utilisation. The data could be used for early warning and forecasting traffic conditions in real-time. The benefit of wireless mobile communication research, especially Car to Car (C2C) communication is to abandon the expensive wireline-deployed and central processing units. Through the interconnection of many personal mobile devices, a low- cost freely extended, high-performance and parallel system can be formed. Car to Car communication can make possible efficient and reliable data transmission by wireless links in a traffic area. It is based on principles of mobile ad-hoc network (MANET) and applies to the domain of vehicles, being Vehicular ad-hoc network (VANET) which is a key component of ITS. The C2C communication system has become essential for driving safety and comfort and also for improving road condition. Also, the traffic prediction system is also an important part of ITS, traffic condition prediction can be regarded as an extension application of VANET. It provides traffic condition in advance via a variety of prediction models and helps the people make better driving safety, travel decisions and route selections regarding departure or driving time. The challenge of wireless traffic prediction technology is the uncertainty of traffic and real-time traffic data collection. It is widely known that urban transport system is a participatory, time-varying and complex nonlinear system. This uncertainty comes not only from the natural causes, such as seasonal and weather factors, but also from human factors, such as traffic accidents, emergencies and driver’s behaviour. In particular, the short-term traffic prediction is more affected by random interference factors. Current wireless traffic prediction research is usually based on a combination of wireless technology and traditional prediction model. The predictable traffic conditions include travel speed, travel time, traffic density, traffic accident, congestion level. However, in a large network environment, as the number of nodes increases, the transmission performance degrades and the prediction accuracy decreases because the prediction model does not obtain enough data. In this thesis, a novel traffic prediction framework (PPM-C2C) is proposed – Pervasive Prediction Model (PPM) based on the C2C communication. The framework utilises ad-hoc data via C2C communications for a short time traffic prediction in each car. This project builds and investigates the behaviour of a pervasive traffic simulation model in Ad-hoc network, with a particular part of it embedded into each vehicle’s equipment. It includes the data collection, aggregation and application aim to be running in all individual cars so that cars have up to date information on the traffic at all times. Moreover, those cars could predict the traffic conditions of a road section in a short time through the proposed prediction framework, especially travel speed prediction. When the car receives the current traffic information about other vehicles, the prediction system will incorporate the information, analyse the data and predict the traffic conditions of this road section for a future time. The design does not depend on any roadside communications infrastructure. It is a simple and flexible car communication and processing technology to collect real-time traffic information. This process will be aided by car to car wireless communication technology available nowadays. To achieve this goal, a mobility model adapted to VANET needs to be generated that a realistic city scenario based on the actual traffic traces is carried out through simulation. Based on this, we investigate the necessary influencing factors for predicted results. The simulation results illustrate that the prediction model can be applied to wireless network environment for a short time prediction, and our results demonstrate the viability and effectiveness of the proposed prediction framework over Car to Car communications. Furthermore, the wireless environment and derived factors can result in decreased application performance

Improving Performance of IEEE 802.11p MAC Layer for Emergency Message Dissemination

Vehicular ad-hoc networking is the most promising subfield of mobile ad-hoc networks, which may become the ad-hoc networking technology in near future for vehicles communicating amongst themselves on road. It uses IEEE 802.11p MAC protocol as wireless networking technology. The IEEE 802.11p MAC protocol has inherent problems in wireless ad-hoc networking environment due its heterogeneous, infrastructureless and highly dynamic nature. The performance of IEEE 802.11p MAC layer for vehicular ad-hoc networking is based on performance of one-hop broadcasting. The performance of IEEE 802.11p one-hop broadcasting is of major concern regarding emergency message dissemination. The CSMA/CA protocol used in IEEE 802.11p is far from optimal solution for emergency message dissemination due to inherent properties of random access, higher delivery delays and retransmissions. Techniques to improve emergency message dissemination delivery rate and minimize time latency of message dissemination, such as, disabling backoff and synchronous transmission, have been mentioned in this thesis out of which one technique such as disabling backoff is being evaluated through simulation results. The goal of this thesis work is to evaluate a technique, modifying the IEEE 802.11p MAC layer protocol using Network Simulator 3 (NS3). The technique is based on introducing a separate EDCA queue and a separate EDCAF function for emergency messages in QoS EDCA priority queues, disabling backoff for emergency messages and giving highest priority to emergency messages in a station having different AC queues seeking for transmission opportunity. Disabling backoff for emergency messages may reduce time latency arising from exponential backoff algorithm. As the backoff is disabled, more than one station may start transmitting emergency message at the same time. So, it can be deduced that such technique could be beneficial for simple emergency applications. The simulation results show that this technique could be useful for emergency applications utilizing a buzz signal for hazardous warnings on road