Evaluating the Impact of Transmission Power on Selecting Tall Vehicles as Best Next Communication Hop

The relatively low height of antennas on communicating vehicles in Vehicular Ad Hoc Networks (VANETs) makes one hop and as well multi-hop Vehicle-to-Vehicle (V2V) communication susceptible to obstruction by other vehicles on the road. When the transmitter or receiver (or both) is a Tall vehi- cle, (i.e., truck), the V2V communication suffer less from these obstructions. The transmission power control is an important feature in the design of (multi- hop) VANET communication algorithms. However, the benefits of choosing a Tall vehicle when transmission power is varied are not yet extensively re- searched. Therefore, the main contribution of this paper is to evaluate the im- pact of transmission power control on the improved V2V communication capa- bilities of tall vehicles. Based on simulations, it is shown that significant bene- fits are observed when a Tall vehicle is selected rather than a Short vehicle as a next V2V communication hop to relay packets. Moreover, the simulation exper- iments show that as the transmission power is increasing, the rate of Tall vehi- cles that are selected as best next V2V communication hop is significantly growing

TDMA-Based MAC (CVTMAC) in Green Vehicular Networks

The growing need to reduce the carbon footprint and the operation expenditure (OPEX) in communication networks necessitates the deployment of wind powered base stations (BSs) and roadside units (RSUs) for vehicular communication networks in windy countries with limited solar irradiation. This system finds ready application in sparse areas like countryside and motorways that lack the supply from the national grid for economic reasons. The stringent performance requirement of vehicular communication systems owed to their critical services poses challenges to their greening efforts. In this paper, we design a robust time-division multiple access (TDMA) based MAC for an infrastructure based green vehicular network in a motorway scenario and investigate the network performance against the stringent quality of service (QoS) thresholds. We call the proposed Centralised Vehicular TDMA based MAC as CVTMAC for short. To obtain a realistic performance evaluation, we model and simulate the proposed MAC protocol with the real channel characteristics of the motorway environment fully incorporated. The off grid RSU is powered solely by an economical and easy to deploy small standalone wind energy conversion systems (SSWECS). Wind energy-based rate adaptation is deployed in the RSU to enhance the efficient utilization of available energy (considering the intermittent nature of wind energy). In this study the real vehicular traffic profiles and wind data for a specified motorway region have been utilised. Both analytic and simulation results reveal that with the introduction of small battery capacity (27 Ah), the green vehicular network is able to support QoS for data, audio and video-related applications at each hour of the day in a motorway vehicular environment

Motorway Vehicular Networks with Renewable Energy Powered Access Points

The goal of this work is to consider the potential of using renewable energy only to power roadside units (RSUs), which not only reduces CO2 footprint but also reduces the infrastructure needed in motorway vehicular communication. The thesis begins with collation and analysis of wind and motorway traffic data for the purpose of determining the energy demand of vehicular networks as well as the energy supply obtainable from wind. This is followed by the study of a standalone RSU powered by wind energy. Small size standalone wind energy systems which have benefits of low cost, easy and large scale deployments are implemented for the low power RSUs. The concept of wind energy based rate adaptation is introduced and implemented in the RSU through which RSU can vary transmission power according to the availability of wind energy. This reduces the outage and improves the overall service quality. Traditionally rate adaptation was employed to cater for wireless channel unavailability. A queuing model for the RSU is developed and verified through simulation to evaluate the performance in terms of delay, packet loss and utilisation. Channel fading is considered and the performance of the RSU is re-evaluated in terms of the same quality of service parameters, viz. delay, packet loss and utilisation to investigate the impact of fading in the network. Next, the reliability of the RSU is redefined in the context of unavailability of sufficient wind power. The transient nature of wind energy causes the RSUs to either transmit at full data rate or not transmit at all depending on the availability of sufficient energy. Thus, a failure occurs when the wind power is less than the load. Therefore, a framework has been developed for redefining a number of reliability parameters in the context of wind powered RSUs. A detailed wind data analysis was carried out based upon the hourly wind speed obtained from the UK air information resource (AIR) database for a period of five years, to determine the energy model of the deployed micro-turbine. An energy storage device (a small battery) is connected to the micro-wind turbine for improved service quality

Investigating seamless handover in VANET systems

Wireless communications have been extensively studied for several decades, which has led to various new advancements, including new technologies in the field of Intelligent Transport Systems. Vehicular Ad hoc Networks or VANETs are considered to be a long-term solution, contributing significantly towards Intelligent Transport Systems in providing access to critical life-safety applications and infotainment services. These services will require ubiquitous connectivity and hence there is a need to explore seamless handover mechanisms. Although VANETs are attracting greater commercial interest, current research has not adequately captured the realworld constraints in Vehicular Ad hoc Network handover techniques. Due to the high velocity of the vehicles and smaller coverage distances, there are serious challenges in providing seamless handover from one Road Side Unit (RSU) to another and this comes at the cost of overlapping signals of adjacent RSUs. Therefore, a framework is needed to be able to calculate the regions of overlap in adjacent RSU coverage ranges to guarantee ubiquitous connectivity. This thesis is about providing such a framework by analysing in detail the communication mechanisms in a VANET network, firstly by means of simulations using the VEINs framework via OMNeT++ and then using analytical analysis of the probability of successful packet reception. Some of the concepts of the Y-Comm architecture such as Network Dwell Time, Time Before Handover and Exit Times have been used to provide a framework to investigate handover issues and these parameters are also used in this thesis to explore handover in highly mobile environments such as VANETs. Initial investigation showed that seamless communication was dependant on the beacon frequency, length of the beacon and the velocity of the vehicle. The effects of each of these parameters are explored in detail and results are presented which show the need for a more probabilistic approach to handover based on cumulative probability of successful packet reception. In addition, this work shows how the length of the beacon affects the rate of change of the Signal-to-Noise ratio or SNR as the vehicle approaches the Road-Side Unit. However, the velocity of the vehicle affects both the cumulative probability as well as the Signal-to-Noise ratio as the vehicle approaches the Road-Side Unit. The results of this work will enable systems that can provide ubiquitous connectivity via seamless handover using proactive techniques because traditional models of handover are unable to cope with the high velocity of the vehicles and relatively small area of coverage in these environments. Finally, a testbed has been set-up at the Middlesex University, Hendon campus for the purpose of achieving a better understanding of VANET systems operating in an urban environment. Using the testbed, it was observed that environmental effects have to be taken into considerations in real-time deployment studies to see how these parameters can affect the performance of VANET systems under different scenarios. This work also highlights the fact that in order to build a practical system better propagation models are required in the urban context for highly mobile environments such as VANETs

Mobility and connectivity in highway vehicular networks: a case study in Madrid

The performance of protocols and architectures for upcoming vehicular networks is commonly investigated by means of computer simulations, due to the excessive cost and complexity of large-scale experiments. Dependable and reproducible simulations are thus paramount to a proper evaluation of vehicular networking solutions. Yet, we lack today a reference dataset of vehicular mobility scenarios that are realistic, publicly available, heterogeneous, and that can be used for networking simulations straightaway. In this paper, we contribute to the endeavor of developing such a reference dataset, and present original synthetic traces that are generated from high-resolution real-world traffic counts. They describe road traffic in quasi-stationary state on three highways near Madrid, Spain, for different time-spans of several working days. To assess the potential impact of the traces on networking studies, we carry out a comprehensive analysis of the vehicular network topology they yield. Our results highlight the significant variability of the vehicular connectivity over time and space, and its invariant correlation with the vehicular density. We also underpin the dramatic influence of the communication range on the network fragmentation, availability, and stability, in all of the scenarios we consider.The research leading to these results has received funding from the People Programme (Marie Curie Actions) of the European Unions Seventh Framework Programme (FP7/2007-2013) under REA grant agreement n.630211 ReFleX. This research was also funded by Spanish MICINN through the ADAS-ROAD Project (TRA2013-48314-C3-1-R). Funding for D. Naboulsi was provided by a grant from Rhône-Alpes Region. This work was carried out while Marco Gramaglia was at CNR-IEIIT.Publicad

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

Enhancing the Physical Layer in V2V Communication Using OFDM - MIMO Techniques

Vehicular Ad hoc network (VANET) has recently been attracting the attention of researchers as a new technology in the wireless communication system. Vehicle-to-vehicle V2V communication can be considered an important way to help the drivers to satisfy requirements such as less congestion, accident warning, road exploration, etc. The propagation issues such as multipath fading significantly affect the reliability of V2V communication. The goal of this work is to enhance the performance of the physical layer PHY in V2V communication. However, the cellular phone channel has been used to evaluate the possibility of apply it in the vehicular communication V2V. The simulation results observed that the transmitted signal is affected by a multipath fading channel. In order to overcome this problem two techniques are used: Orthogonal Frequency Division Multiplexing (OFDM) technique and Multiple-Input-MultipleOutput (MIMO) diversity technique. The simulation results showed that the OFDM technique overcomes the multipath fading with high transmission power. On the other hand, MIMO diversity technique called Alamouti Space-Time Code for two transmitters and two receivers (MIMO 2x2) is used to improve the error degradation with less transmission power