A New Clustering Protocol for Hybrid Sensor Vehicular Networks (HSVNs)

As the UAE is classified among the highest countries in road accidents; it’s an urgent necessity to derive proper and effective solutions. One of the well-known solutions is to move to the Intelligent Transportation Systems (ITS). ITS is achieved by the implementation of advanced technologies to help the roads to be smarter, safer and more coordinated. There are different studies and researches published in this area. This thesis is mainly conducted to achieve the same goal, which is increasing the safety on our roads. The aim of this research is to build a new clustering protocol in the Hybrid Sensor Vehicular Networks (HSVN). HSVN is introduced as a new concept that integrates wireless sensor networks along with vehicular networks to increase the overall performance of both networks and the need of such new protocol in these networks is high. Although there are many published proposals, there is still a need to have a complete protocol that can reduce the shortcomings in the proposed solutions. The main features in the proposed protocol are creating a balance system by dividing the clustering process overheads between the vehicles in the network and the Road Side Unit (RSU), so instead of relying only on the vehicles’ resources, the RSU shares the process’s overhead by collecting data, calculating weighting factors, and electing suitable cluster heads. Moreover, the proposed protocol reduces the computational and the communication costs by electing two cluster heads for each cluster; one acts as the main cluster head and the other as a standby cluster head. By this feature, if a cluster head moves outside the cluster region, there is no need to run the clustering process again to elect a new cluster head as a standby cluster head exists. Also, one of the main characteristics of the new protocol is minimizing the collision in the system, and consequently increasing the throughput by defining the upper bound of the number of members in each cluster. The overall performance of the proposed protocol is very good and promises to solve many challenges in the existing protocols. In addition, the results show that this protocol outperforms one of the best existing mobility protocols in terms of the total number of clusters formed in the network, the number of single node clusters, and the saturation throughput of the clusters, the communication overheads and energy consumption reductions

Social internet of vehicles for smart cities

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SDNと車両クラスタリングを活用したV2I通信方式

電気通信大学202

Avaliação de estratégias de disseminação de mensagens de emergência em redes veiculares

Nas últimas décadas, a tecnologia e as telecomunicações têm sofrido uma evolução exponencial. Atualmente, cada vez mais as comunicações entre veículos assumem um papel importante no quotidiano de cada um de nós, quer seja pela necessidade de obter informações antecipadas acerca do percurso rodoviário que fazemos diariamente, ou até mesmo a distribuição de conteúdos urgentes e não urgentes. Deste modo, as redes veiculares surgem com algumas particularidades, tais como o tempo reduzido de contacto que leva à perda de ligações e conectividade, devido à mobilidade constante dos nós na rede, a sua dispersão geográfica e a densidade variável. Estas singularidades criam algumas fragilidades na rede e proporcionaram o aparecimento de um novo conceito denominado redes tolerantes a atrasos (Delay Tolerant Network (DTN)). Desta forma, o encaminhamento da informação é feita através de um mecanismo de Store-Carry-and-Forward (SCF), que resolve os desafios descritos anteriormente, permitindo que a informação chegue a todos os nós em situações onde não existe um caminho estabelecido extremo-a-extremo. O objetivo deste trabalho é o envio eficiente de mensagens de emergência entre veículos para informar sobre acidentes ou outros eventos, para que estas cheguem a todos os veículos (que se encontram numa área delimitada) no menor tempo possível e causando o menor overhead. De forma a tirar partido da localização, da direção, da velocidade ou do número de vizinhos que cada veículo tem num dado instante temporal, foram testadas e implementadas sete estratégias para disseminação de mensagens de emergência: Position-based Adaptative Broadcast (PAB), Position-based Adaptative Broadcast towards furthest neighbor Before Accident (PABBA), Speed-based Adaptative Broadcast to fastest Oncoming Neighbor Accident (SABONA), Most Active Connections based Adaptative Broadcast before Accident (MACABA), Position-based Adaptative Broadcast All Around (PAB2A), Speed-based Adaptative Broadcast All Around (SABAA) e Most Active Connections based Adaptative Broadcast All Around (MACAB2A). As estratégias PABBA, SABONA, MACABA têm como objetivo disseminar as mensagens de emergência apenas para trás do acidente, enquanto que as estratégias PAB, PAB2A, SABAA e MACAB2A têm como objetivo disseminar as mensagens de emergência nas várias direções. No caso das estratégias PAB, PABBA, SABONA, MACABA é escolhido um nó para retransmitir as mensagens a cada salto da mensagem; nas estratégias restantes é escolhido mais do que um nó para retransmitir as mensagens, sendo escolhido um nó para retransmitir a mensagem para cada uma das direções, sendo escolhidos no máximo 6 nós retransmissores por salto. Inicialmente, a mobilidade dos veículos com a ocorrência de um acidente foi gerada no SUMO. Posteriormente, foi estabelecida a conetividade entre os veículos e feita a compatibilidade entre o simulador de mobilidade (SUMO) e o emulador de Vehicular Ad hoc NETworks (VANETs) (mobile Opportunistic Vehicular Emulator for Real Scenarios (mOVERS)), no qual foram implementas as estratégias e avaliado a eficiência destas, por forma a escolher a melhor estratégia, tendo em conta, a taxa de entrega e o overhead causado. Conclui-se que a melhor estratégia é a SABAA, uma vez que permite ter taxas de entrega melhores na maioria dos cenários testados e um baixo . overhead na rede.In the last decades, the technology and telecommunications have suffered an exponential evolution. Nowadays, communications between vehicles have an important role in our daily life. Whether it is the need to know information in advance the vehicles route, or even the distribution of urgent or nonurgent content. In this way, vehicular networks have special characteristics, such as the reduced contact time that leads with loss of connections and connectivity, due to the node mobility in the network, geographic dispersion and variable density. Those singularities create a fragility in the network and have led to the emergence of a new concept called DTN. Thus, the forwarding of the information is done by a mechanism called SCF, which addresses the challenges described before, allowing information to reach all nodes in situations where there is no established end-to-end path. The objective of this work is the efficient transmission of emergency messages between vehicles to inform about accidents or other events, such that they can reach all vehicles (in a delimited area) in the shortest possible time and with reduced overhead. In order to take advantage of the location, direction, speed or number of neighbors that each vehicle has in a given time instant, seven strategies were tested and implemented: PAB, PABBA, SABONA, MACABA, PAB2A, SABAA and MACAB2A. The strategies PABBA, SABONA, MACABA aim to disseminate the emergency messages only behind the accident, whereas the strategies PAB, PAB2A, SABAA and MACAB2A aim to disseminate the emergency messages in the various directions. In the case of the strategies PAB, PABBA, SABONA, MACABA, a node is chosen to retransmit the message with each hop of the message; in the remaining strategies, it is chosen more than one node to retransmit the message, being chosen a node to retransmit the message to each of the directions, being chosen at maximum 6 nodes retransmitters per hop. A test platform was used, consisting of 3 tools. Initially, the mobility of vehicles with the occurrence of an accident was generated in SUMO. Afterwards, the connectivity between the vehicles was established and the compatibility between the mobility simulator (SUMO) and the emulator of VANETs (mOVERS) was established. The strategies were implemented in the emulator and their efficiency were evaluated, in order to choose the best strategy, given the delivery rate and overhead. It is concluded that the best strategy is SABAA, since it achieves better delivery rates in most of the tested scenarios with lower overhead in the network.Mestrado em Engenharia Eletrónica e Telecomunicaçõe

Fast propagation of messages in VANETs and the impact of vehicles as obstacles on signal propagation

Vehicular Ad hoc NETworks (VANETs), an emerging technology, use vehicles as nodes to form a mobile ad hoc network for the dissemination of safety and entertainment messages. The thesis provides a scheme for the fast propagation of messages in VANETs and evaluates the impact of vehicles as obstacles on signal propagation. An improved scheme for intermediate node selection in DBA-MAC (Dynamic Backbone Assisted MAC) is proposed, which consists of a CW (Contention Window) constraint scheme and an updated criterion of suitability. A performance comparison shows that messages in the proposed scheme propagate faster than in DBA-MAC. The CW constraint scheme is also applicable in VANET protocols which adapt the CW mechanism to communicate the suitability of vehicles for acting as intermediate nodes. Additionally, the mathematical models for DBAMAC and the proposal are established, which indicate the probability of candidates to be chosen over alternatives in the intermediate node selection. A novel metric - delay taking into account the effect of formation time(DEFT) - is proposed. DEFT combines the network formation time and propagation delay. It shows the impact of network formation on propagation latency. The configuration for optimal performance can be acquired using the proposed DEFT. In order to evaluate the proposals, a novel distribution of vehicle location is proposed. In the proposed distribution, the security distances between adjacent vehicles in the same lane are considered. The estimation of vehicles’ location can be more practical and accurate using the proposed distribution. In the wide body of the VANET literature, it is assumed that all the vehicles within the radio range of a transmitter are able to receive the signal. Yet, in practice, the vehicles as obstacles between the transmitter and the receiver affect the signal propagation significantly. This thesis presents the impact of these obstacles on the network connectivity and system performance of the protocols. The results and the analysis show that neglecting obstacles in practice leads to a significant degree of error in the estimation of system performance. In practice, tall vehicles forward messages in a more efficient way than do lower vehicles since they are free from the obstacle effect. An improved scheme is proposed, in which the height of vehicles is used as a factor to determine their suitability for message forwarding

Distributed clustering in vehicular networks

Clustering in vanets is of crucial importance in order to cope with the dynamic features of the vehicular topologies. Algorithms that give good results in Manets fail to create stable clusters since vehicular nodes are characterized by their high mobility and the different mobility patterns that even nodes in proximity may follow. In this paper, we propose a distributed clustering algorithm which forms stable clusters based on force directed algorithms. The simulation results show that our Spring-Clustering (Sp-Cl) scheme has stable performance in randomly generated scenarios on a highway. It forms lesser clusters than Lowest-ID and it is better in terms of Cluster stability compared to Lowest-ID and LPG algorithms in the same scenarios. © 2012 IEEE

Distributed clustering in vehicular networks

Clustering in vanets is of crucial importance in order to cope with the dynamic features of the vehicular topologies. Algorithms that give good results in Manets fail to create stable clusters since vehicular nodes are characterized by their high mobility and the different mobility patterns that even nodes in proximity may follow. In this paper, we propose a distributed clustering algorithm which forms stable clusters based on force directed algorithms. The simulation results show that our Spring-Clustering (Sp-Cl) scheme has stable performance in randomly generated scenarios on a highway. It forms lesser clusters than Lowest-ID and it is better in terms of Cluster stability compared to Lowest-ID and LPG algorithms in the same scenarios. © 2012 IEEE