2,100 research outputs found
Enhanced Position Verification for VANETs using Subjective Logic
The integrity of messages in vehicular ad-hoc networks has been extensively
studied by the research community, resulting in the IEEE~1609.2 standard, which
provides typical integrity guarantees. However, the correctness of message
contents is still one of the main challenges of applying dependable and secure
vehicular ad-hoc networks. One important use case is the validity of position
information contained in messages: position verification mechanisms have been
proposed in the literature to provide this functionality. A more general
approach to validate such information is by applying misbehavior detection
mechanisms. In this paper, we consider misbehavior detection by enhancing two
position verification mechanisms and fusing their results in a generalized
framework using subjective logic. We conduct extensive simulations using VEINS
to study the impact of traffic density, as well as several types of attackers
and fractions of attackers on our mechanisms. The obtained results show the
proposed framework can validate position information as effectively as existing
approaches in the literature, without tailoring the framework specifically for
this use case.Comment: 7 pages, 18 figures, corrected version of a paper submitted to 2016
IEEE 84th Vehicular Technology Conference (VTC2016-Fall): revised the way an
opinion is created with eART, and re-did the experiments (uploaded here as
correction in agreement with TPC Chairs
A realistic path loss model for real-time communication in the urban grid environment for Vehicular Ad hoc Networks
Wireless signal transmission is influenced by environmental effects. These effects have also been challenging for Vehicular Ad hoc Network (VANET) in real-time communication. More specifically, in an urban environment, with high mobility among vehicles, a vehicle’s status from the transmitter can instantly trigger from line of sight to non-line of sight, which may cause loss of real-time communication. In order to overcome this, a deterministic signal propagation model is required, which has less complexity and more feasibility of implementation. Hence, we propose a realistic path loss model which adopts ray tracing technique for VANET in a grid urban environment with less computational complexity. To evaluate the model, it is applied to a vehicular simulation scenario. The results obtained are compared with different path loss models in the same scenario based on path loss value and application layer performance analysis. The proposed path loss model provides higher loss value in dB compared to other models. Nevertheless, the performance of vehicle-vehicle communication, which is evaluated by the packet delivery ratio with different vehicle transmitter density verifies improvement in real-time vehicle-vehicle communication. In conclusion, we present a realistic path loss model that improves vehicle-vehicle wireless real-time communication in the grid urban environment
Emerging research directions in computer science : contributions from the young informatics faculty in Karlsruhe
In order to build better human-friendly human-computer interfaces,
such interfaces need to be enabled with capabilities to perceive
the user, his location, identity, activities and in particular his interaction
with others and the machine. Only with these perception capabilities
can smart systems ( for example human-friendly robots or smart environments) become posssible. In my research I\u27m thus focusing on the
development of novel techniques for the visual perception of humans and
their activities, in order to facilitate perceptive multimodal interfaces,
humanoid robots and smart environments. My work includes research
on person tracking, person identication, recognition of pointing gestures,
estimation of head orientation and focus of attention, as well as
audio-visual scene and activity analysis. Application areas are humanfriendly
humanoid robots, smart environments, content-based image and
video analysis, as well as safety- and security-related applications. This
article gives a brief overview of my ongoing research activities in these
areas
Modeling vanet deployment in urban settings
... (VANETs) has prompted greater research into simulation models that better reflect urban VANET deployments. Still, we lack a systematic understanding of the required level of simulation details in modeling various real-world urban constraints. In this work, we developed a series of simulation models that account for street layout, traffic rules, multilane roads, acceleration-deceleration, and RF attenuation due to obstacles. Using real and controlled synthetic maps, we evaluated the sensitivity of the simulation results toward these details. Our results indicate that the delivery ratio and packet delays in VANETs are more sensitive to the clustering effect of vehicles at intersections and their accelerationdeceleration. The VANET performance appears to be only marginally affected by the simulation of multiple lanes and careful synchronization at traffic signals. We also found that the performance in dense VANETs improves significantly when routing decisions are limited to a wireless backbone of mesh nodes, whereas in sparse VANETs, performance improves when vehicles also participate in ad hoc routing. Finally, through measurement and analysis of signal strengths around urban city blocks, we show that the effect of signal attenuation due to physical obstacles can potentially be parameterized in simulations. Our work provides a starting point for further understanding and development of more accurate VANET simulation models
Content Download in Vehicular Networks in Presence of Noisy Mobility Prediction
Bandwidth availability in the cellular backhaul is challenged by ever-increasing demand by mobile users. Vehicular users, in particular, are likely to retrieve large quantities of data, choking the cel- lular infrastructure along major thoroughfares and in urban areas. It is envisioned that alternative roadside network connectivity can play an important role in offloading the cellular infrastructure. We investigate the effectiveness of vehicular networks in this task, considering that roadside units can exploit mobility prediction to decide which data they should fetch from the Internet and to schedule transmissions to vehicles. Rather than adopting a specific prediction scheme, we propose a fog-of-war model that allows us to express and account for different degrees of prediction accuracy in a simple, yet effective, manner. We show that our fog-of-war model can closely reproduce the prediction accuracy of Markovian techniques. We then provide a probabilistic graph-based representation of the system that includes the prediction information and lets us optimize content prefetching and transmission scheduling. Analytical and simulation results show that our approach to content downloading through vehicular networks can achieve a 70% offload of the cellular networ
Coverage Protocols for Wireless Sensor Networks: Review and Future Directions
The coverage problem in wireless sensor networks (WSNs) can be generally
defined as a measure of how effectively a network field is monitored by its
sensor nodes. This problem has attracted a lot of interest over the years and
as a result, many coverage protocols were proposed. In this survey, we first
propose a taxonomy for classifying coverage protocols in WSNs. Then, we
classify the coverage protocols into three categories (i.e. coverage aware
deployment protocols, sleep scheduling protocols for flat networks, and
cluster-based sleep scheduling protocols) based on the network stage where the
coverage is optimized. For each category, relevant protocols are thoroughly
reviewed and classified based on the adopted coverage techniques. Finally, we
discuss open issues (and recommend future directions to resolve them)
associated with the design of realistic coverage protocols. Issues such as
realistic sensing models, realistic energy consumption models, realistic
connectivity models and sensor localization are covered
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