Juan A. Martinez

A survey on modeling and simulation of vehicular networks: Communications, mobility, and tools

Abstract Simulation is a key tool for the design and evaluation of Intelligent Transport Systems (ITS) that take advantage of communication-capable vehicles in order to provide valuable safety, traffic management, and infotainment services. It is widely recognized that simulation results are only significant when realistic models are considered within the simulation toolchain. However, quite often research works on the subject are based on simplistic models unable to capture the unique characteristics of vehicular communication networks. If the implications of the assumptions made by the chosen models are not well understood, incorrect interpretations of simulation results will follow. In this paper, we survey the most significant simulation models for wireless signal propagation, dedicated short-range communication technologies, and vehicular mobility. The support that different simulation tools offer for such models is discussed, as well as the steps that must be undertaken to fine-tune the model parameters in order to gather realistic results. Moreover, we provide handy hints and references to help determine the most appropriate tools and models. We hope this article to help prospective collaborative ITS researchers and promote best simulation practices in order to obtain accurate results.

BRAVE: Beacon-less routing algorithm for vehicular environments

We study the problem of multihop routing in vehicular ad hoc networks (VANET). IEEE 802.11p and other vehicular network standards advocate vehicles to issue periodic broadcast messages at regular intervals called beacons. Beacons include among other information geographic coordinates of the vehicle, heading, speed, etc. Thus, most VANET routing solutions in the literature use those beacons to know available neighbors and take position-based routing decisions. However, we argue that using that information to take routing decisions can result in inefficiencies such as temporal loops in the forwarding path, backward progress due to stale information and use of low-quality links. We propose a new protocol called BRAVE in which neighbor selection is done opportunistically in collaboration with neighbors. Our simulation results show that BRAVE is able to outperform existing solutions in a realistic urban scenario for a variety of network densities.

DNA methylation map in circulating leukocytes mirrors subcutaneous adipose tissue methylation pattern: a genome-wide analysis from non-obese and obese patients

The characterization of the epigenetic changes within the obesity-related adipose tissue will provide new insights to understand this metabolic disorder, but adipose tissue is not easy to sample in population-based studies. We aimed to evaluate the capacity of circulating leukocytes to reflect the adipose tissue-specific DNA methylation status of obesity susceptibility. DNA samples isolated from subcutaneous adipose tissue and circulating leukocytes were hybridized in the Infinium HumanMethylation 450 BeadChip. Data were compared between samples from obese (n = 45) and non-obese (n = 8–10) patients by Wilcoxon-rank test, unadjusted for cell type distributions. A global hypomethylation of the differentially methylated CpG sites (DMCpGs) was observed in the obese subcutaneous adipose tissue and leukocytes. The overlap analysis yielded a number of genes mapped by the common DMCpGs that were identified to reflect the obesity state in the leukocytes. Specifically, the methylation levels of FGFRL1, NCAPH2, PNKD and SMAD3 exhibited excellent and statistically significant efficiencies in the discrimination of obesity from non-obesity status (AUC > 0.80; p < 0.05) and a great correlation between both tissues. Therefore, the current study provided new and valuable DNA methylation biomarkers of obesity-related adipose tissue pathogenesis through peripheral blood analysis, an easily accessible and minimally invasive biological material instead of adipose tissue.

Efficient Certificate Revocation in Vehicular Networks Using NGN Capabilities

We address the problem of efficiently revoking certificates of malicious and compromised nodes in vehicular networks. As in previous work, our focus is making sure that vehicles receive the new list of revoked certificates (CRL) before they can be compromised. Unlike previous solutions, our work revolves around the idea of making use of existing capabilities offered by mobile network operators to improve the efficiency of the distribution of the CRL. Our proposed solution gathers positions and headings of vehicles using a location service enabler. Based on that information, the infrastructure can decide when and in which areas to broadcast the incremental CRL using any of the existing technologies such as the Multimedia Broadcast Multicast Service (MBMS). Our simulation results show that the proposed solution outperforms existing solutions based on the use of Road-side Units (RSUs) for disseminating CRLs. The improvement in terms of distribution delay and number of compromised nodes is noticeably better as the density of vehicles decreases.

Evaluation of the use of guard nodes for securing the routing in VANETs

We address the problem of effective vehicular routing in hostile scenarios where malicious nodes intend to jeopardize the delivery of messages. Compromised vehicles can severely affect the performance of the network by a number of attacks, such as selectively dropping messages, manipulating them on the fly, and the likes. One of the best performing solutions that has been used in static wireless sensor networks to deal with these attacks is based on the concept of watchdog nodes (also known as guard nodes) that collaborate to continue the forwarding of data packets in case a malicious behavior in a neighbor node is detected. In this work, we consider the beacon-less routing algorithm for vehicular environments routing protocol, which has been previously shown to perform very well in vehicular networks, and analyze whether a similar solution would be feasible for vehicular environments. Our simulation results in an urban scenario show that watchdog nodes are able to avoid up to a 50% of packet drops across different network densities and for different number of attackers, without introducing a significant increase in terms of control overhead. However, the overall performance of the routing protocol is still far from optimal. Thus, in the case of vehicular networks, watchdog nodes alone are not able to completely alleviate these security threats.

Association between diet-quality scores, adiposity, total cholesterol and markers of nutritional status in european adults: Findings from the Food4Me study

Diet-quality scores (DQS), which are developed across the globe, are used to define adherence to specific eating patterns and have been associated with risk of coronary heart disease and type-II diabetes. We explored the association between five diet-quality scores (Healthy Eating Index, HEI; Alternate Healthy Eating Index, AHEI; MedDietScore, MDS; PREDIMED Mediterranean Diet Score, P-MDS; Dutch Healthy Diet-Index, DHDI) and markers of metabolic health (anthropometry, objective physical activity levels (PAL), and dried blood spot total cholesterol (TC), total carotenoids, and omega-3 index) in the Food4Me cohort, using regression analysis. Dietary intake was assessed using a validated Food Frequency Questionnaire. Participants (n = 1480) were adults recruited from seven European Union (EU) countries. Overall, women had higher HEI and AHEI than men (p < 0.05), and scores varied significantly between countries. For all DQS, higher scores were associated with lower body mass index, lower waist-to-height ratio and waist circumference, and higher total carotenoids and omega-3-index (p trends < 0.05). Higher HEI, AHEI, DHDI, and P-MDS scores were associated with increased daily PAL, moderate and vigorous activity, and reduced sedentary behaviour (p trend < 0.05). We observed no association between DQS and TC. To conclude, higher DQS, which reflect better dietary patterns, were associated with markers of better nutritional status and metabolic health.

Impact of the Pre-Authentication Performance in Vehicular Networks

The possibility of connecting vehicles to fixed IP networks through roadside units (RSUs) or even access gateways is seen as a very interesting alternative to fully infrastructure-less VANETs. However, getting access to those fixed networks must be controlled and only authorized users should be able to use those RSUs or gateways. However, that authentication process incurs in a not-negligible delay which can result in packet losses and other issues during handoffs. In this paper we assess the performance benefit provided by pre-authentication schemes in which vehicles use the current gateway to authenticate with nearby gateways before they finally attach to them. Our simulation results show that pre- authentication offers important benefits in terms of packet delivery ratio and handoff delays both in urban and inter-urban scenarios.

Higher Protein Intake Is Not Associated with Decreased Kidney Function in Pre-Diabetic Older Adults Following a One-Year Intervention—A Preview Sub-Study

Concerns about detrimental renal effects of a high-protein intake have been raised due to an induced glomerular hyperfiltration, since this may accelerate the progression of kidney disease. The aim of this sub-study was to assess the effect of a higher intake of protein on kidney function in pre-diabetic men and women, aged 55 years and older. Analyses were based on baseline and one-year data in a sub-group of 310 participants included in the PREVIEW project (PREVention of diabetes through lifestyle Intervention and population studies in Europe and around the World). Protein intake was estimated from four-day dietary records and 24-hour urinary urea excretion. We used linear regression to assess the association between protein intake after one year of intervention and kidney function markers: creatinine clearance, estimated glomerular filtration rate (eGFR), urinary albumin/creatinine ratio (ACR), urinary urea/creatinine ratio (UCR), serum creatinine, and serum urea before and after adjustments for potential confounders. A higher protein intake was associated with a significant increase in UCR (p = 0.03) and serum urea (p = 0.05) after one year. There were no associations between increased protein intake and creatinine clearance, eGFR, ACR, or serum creatinine. We found no indication of impaired kidney function after one year with a higher protein intake in pre-diabetic older adults.

ARMOUR: Large-scale experiments for IoT security & trust

The IoT is composed of a global network of heterogeneous devices that exchange information with each other. In this kind of scenarios, the number of smart objects is increasingly high, which enhances the possibility of attacks that compromise security, privacy and trust of the exchanged information. Thus, the need to provide duly tested, benchmarked and certified security and trust solutions for large-scale IoT arises in order to solve these risks. In this direction, this paper presents ARMOUR, a research project in which a methodology to experiment, validate and certify different technological solutions in large-scale conditions is defined. Additionally, a set of bootstrapping, group sharing and software programming experiments is proposed, on which different tests will be executed with the purpose to verify their security and trust in IoT scenarios.

Design of a Cluster-Based Peer to Peer Architecture for MANETs

During the last years, peer to peer (P2P) networks are becoming more and more popular because of their inherent properties that allow users to exchange information and also to collaborate between them with a tremendous easiness.In parallel to this evolution, the use of MANETs has been increased due to the low effort needed to their deployment.Nowadays every user equipped with a mobile device like a laptop or a PDA could create an ad-hoc network just configuring their wireless device. Thus, users without any infrastructure can connect to others. Using P2P platforms upon these kind of network will allow users to collaborate and exchange information. However the mayor application area of these P2P platforms is still the fixed network.This paper presents a new architecture for a collaborative working environment especially designed for MANETs solving the main drawbacks of other P2P platforms designed for static wired networks with the requirement of a high bandwidth. Our approach is based on clustering MANETs allowing efficient communication among nearby nodes without impairment of distant peers connectivity.