We propose to use IEEE 802.11e in conjunction with retransmission mechanisms for priority-based Intervehicle Communication (IVC) for highway safety messaging in both vehicular infrastructure and ad hoc networks. Each IVC message, which is assigned a priority based on the safety event urgency, requires different quality of service in terms of communication reliability and average delay. To increase the communication reliability in a broadcast-based IVC, we apply retransmission mechanisms that can provide proportional reliability differentiation for each prioritized message. We evaluate the performance of our proposed protocol using OPNET Modeler, in terms of percentage of successful transmissions and average delay. The protocol performance is evaluated for (1) different system parameters such as the packet size, number of vehicles, and percentage of priority 1 vehicles, and (2) priority-based protocol parameters, such as contention window, interframe spacing and retransmission parameters. The results show that proper protocol parameter settings per priority message result in an efficient solution for priority based broadcast IVC. Moreover, the proposed protocol is fully compatible with both IEEE 802.11 and IEEE 802.11e standards.

Chakkaphong Suthaputchakun

Priority-Based Inter-Vehicle Communication for Highway Safety Messaging Using IEEE 802.11e

Physical carrier sensing has to date mainly been exploited for improving medium access control in wireless networks. Recently, a parallel algorithm striving to extensively exploit physical carrier sensing
for constructing and maintaining a connected dominating set (CDS), which is also known as spanner,
backbone, or overlay network in wireless ad hoc networks with interference ranges larger than transmission
ranges has been proposed. Existing evaluations of this algorithm are limited to theoretical asymptotic
bounds and simulations of <i>static</i> networks. In this paper, we evaluate the physical carrier sensing-based
CDS maintenance for <i>mobile</i> ad hoc networks through discrete event simulations. For a wide range of
node speeds and node densities, we evaluate the CDS characteristics and message exchanges required for
maintaining the CDS. We find that the algorithm maintains a stable leader set dominating all nodes in the
network for a wide range of mobility levels but struggles to maintain connectivity at high mobility levels.
We also quantify the portions of the control messages for CDS maintenance that are exchanged through
physical carrier sensing. We find that the parallel algorithm manages to greatly reduce the reliance on
intact message receptions.

Sapna Deval

Luke Ritchie

Martin Reisslein

Andrea W. Richa

Evaluation of Physical Carrier Sense Based Backbone Maintenance in Mobile Ad Hoc Networks

Choosing various injection strategies and intake conditions are potentially effective techniques to reduce exhaust emission from diesel engines. The purpose of this study is to investigate the effect of different spray incoming angles, different spray cone angles, different injection timing, and different intake temperatures together with emission characteristics on a heavy duty diesel engine via three dimensional computational fluid dynamics (CFD) procedures. Furthermore the effect of multiple injector combustion chamber and its benefits in pollutant reduction is studied. The principal results show the significant differences in soot and <svg style="vertical-align:-0.13794pt;width:25.174999px;" id="M1" height="10.75" version="1.1" viewBox="0 0 25.174999 10.75" width="25.174999"  xmlns="http://www.w3.org/2000/svg">
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			</text>

		</g>
	</g>
</svg> generation during combustion between above different strategies.

M. Gorji-Bandpy

S. Soleimani

D. D. Ganji

The Effect of Different Injection Strategies and Intake Conditions on the Emissions Characteristics in a Diesel Engine

The numerous benefits of real-time 3D awareness for autonomous vehicles have motivated the incorporation of stereo cameras to the perception units of intelligent vehicles. The availability of the distance between camera and objects is essential for such applications as automatic guidance and safeguarding; however, a poor estimation of the position of the objects in front of the vehicle can result in dangerous actions. There is an emphasis, therefore, in the design of perception engines that can make available a rich and reliable interval of ranges in front of the camera. The objective of this research is to develop a stereo head that is capable of capturing 3D information from two cameras simultaneously, sensing different, but complementary, fields of view. In order to do so, the concept of <i>bifocal perception</i> was defined and physically materialized in an experimental bifocal stereo camera. The assembled system was validated through field tests, and results showed that each stereo pair of the head excelled at a singular range interval. The fusion of both intervals led to a more faithful representation of reality.

Francisco Rovira-Más

Qi Wang

Qin Zhang

Bifocal Stereoscopic Vision for Intelligent Vehicles

Wireless local loop (WLL) provides reliable, flexible, and economical access to the local telephone service using radio technology in the place of traditional wireline. In this paper, an analytical model is derived to evaluate the effect of both imperfect power control and imperfect sectorization on the performance of code division multiple access (CDMA) WLL systems. The results show that the capacity degradation, due to imperfect power control, is about 25.8&#x25; and 11.5&#x25; for single cell and multiple cell systems, respectively. Increasing the overlapping angle from 
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				<tspan style="font-size: 12.50px; " x="0" y="0">0</tspan>
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				<tspan style="font-size: 8.75px; " x="0" y="0">∘</tspan>
			</text>

		</g>
	</g>
</svg> to <svg style="vertical-align:-0.17555pt;width:12.3875px;" id="M2" height="11.225" version="1.1" viewBox="0 0 12.3875 11.225" width="12.3875"  xmlns="http://www.w3.org/2000/svg">
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					 causes the capacity gain to decrease from 6 to 5.53, while the corresponding sectorization efficiency drops from 100&#x25; to 92.3&#x25;.

Sami A. El-Dolil

Performance Analysis of CDMA WLL Systems with Imperfect Power Control and Imperfect 
Sectorization

A deterministic simulation model for the calculation
of sojourn time statistics is proposed. The model is designed for
urban cells taking into account city movement in street pattern,
traffic lights, and crossings. Sojourn time and remaining sojourn
time are assumed to be random variables that follow a gamma
distribution. The parameters of gamma are found for a range of
the chosen cell parameters (road length, probability of stopping
at a crossing and cell radius) using Monte Carlo simulation.
Then, the values are fitted to the empirical model using genetic
algorithms with grammatical evolution. The model can be used
to calculate sojourn time statistical parameters for any urban
circular cell with square street pattern.

Georgios S. Paschos

Ioannis G. Tsoulos

Efstathios D. Vagenas

Stavros A. Kotsopoulos

George K. Karagiannidis

A Deterministic Simulation Model for Sojourn Time in Urban Cells with Square Street Geometry

Vehicular networks are sets of surface transportation systems that have the ability to communicate with each other. There are several possible network architectures to organize their in-vehicle computing systems. Potential schemes may include vehicle-to-vehicle ad hoc networks, wired backbone with wireless last hops, or hybrid architectures using vehicle-to-vehicle communications to augment roadside communication infrastructures. Some special properties of      
these networks, such as high mobility, network partitioning, and constrained topology, differentiate them from other types of wireless networks. We provide an in-depth discussion on the important studies related to architectural design and routing for such networks. Moreover, we discuss the major security concerns appearing in vehicular networks.

Ioannis Broustis

Michalis Faloutsos

Routing in Vehicular Networks: Feasibility, Modeling, and Security

This paper describes a fault-tolerant steer-by-wire road wheel control system. With dual motor and dual microcontroller architecture, this system has the capability to tolerate single-point failures without degrading the control system performance. The arbitration bus, mechanical arrangement of motors, and the developed control algorithm allow the system to reconfigure itself automatically in the event of a single-point fault, and assure a smooth reconfiguration process. Both simulation and experimental results illustrate the effectiveness of the proposed fault-tolerant control system.

Bing Zheng

Sohel Anwar

Fault-Tolerant Control of the Road Wheel Subsystem in a Steer-By-Wire System

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International Journal of Vehicular Technology