An intelligent transportation system aims to provide various traffic safety and navigation services, and mainly relies on local perception and vehicular communication technologies. However, the vehicular communication technologies can be a target of wide range of attacks including position falsification, Sybil and denial-of-service (DoS) attacks which can lead to disastrous traffic accidents and jams. As a viable solution, misbehavior detection systems can be used in vehicular networks. Different from other works, in this paper, we propose a misbehavior detection system that utilizes both local perception and basic safety messages (BSM). Our work shows the methodology for generating realistic vehicular network data sets that include both local perception and BSM. In addition, we compare and show that the propose scheme is better compared to the previous scheme utilizing only beacon information for accurately identifying misbehavior in intelligent transportation system.

ITS-G5 is a communication system for vehicle-to-everything communication for road safety and traffic efficiency applications. On the lower layers, it is based on IEEE 802.11 standard and uses a simple ad hoc mode with a random medium access control scheme. Ad hoc networking is realized by a geographical routing scheme that provides single- and multi-hop communication over ITS-G5 links for periodic and event-driven broadcast messages. Specifically, contention-based forwarding (CBF) allows for efficient and reliable multi-hop packet transport by overhearing and timer-based transmission control. To cope with the channel congestion, decentralized congestion control (DCC) adjusts the message rate and ensures that the network load keeps below a predefined threshold of the bandwidth. To enforce a node's message rate, a “ Gatekeeper” above the MAC and beneath CBF is added. Under high network load, this Gatekeeper introduces an additional queuing delay seen by CBF, which can cause its overhearing function to fail. This contribution studies multi-hop forwarding in the context of DCC with the Gatekeeper and LIMERIC as a rate adaptation algorithm. We propose a congestion-enabled forwarding scheme that, in comparison to existing approaches considering DCC and forwarding separately, restores the efficient operation of CBF, and improves the communication performance in terms of reliability and latency for mixed data traffic composed of single- and multi-hop packets with different priorities. The simulations show the performance improvements in a freeway scenario. An analysis assesses the boundary conditions for CBF and the Gatekeeper. Moreover, the analysis corroborates the simulation.

This paper proposes a stochastic model for the Global Positioning System (GPS) position errors on smartphones in urban canyons. The need to simulate such errors arises in pedestrian to vehicle communications, for example, which enable a new way to protect vulnerable road users. Studying this technology requires accurate modeling of the GPS precision on portable devices, e.g., smartphones since they share pedestrians' location information with vehicles for collision avoidance. The model is derived from and calibrated with pedestrian GPS traces collected from New York City. We show that the model produces GPS error samples with similar spatial and temporal correlation as in the collected field data.

Pedestrians are particularly vulnerable traffic participants with a very high fatality rate. An important component of Advanced Driver Assistant Systems is the accurate localization of pedestrians and other vulnerable traffic participants using various sensors and other technologies. Localization using radio frequency (RF) signals is commonly used, because of the widespread availability of wireless radios, ease of deployment, and the fact that RF-based ranging will work in all weather and light conditions. However, the accuracy of RF-based ranging in vehicular networks is easily affected by high device dynamics and mobility, leading to varying impacts of shadowing and multipath fading. In this paper, we introduce a new ranging algorithm that first uses a novel filtering scheme that reduces the impact of mutipath fading and shadowing. Then, we use an exhaustive search method to minimize an MSE function that represents the difference between the filtered RSSI values and the expected RSSI values (based on the channel model) to estimate the distance between transmitter and receiver. The performance of the proposed ranging algorithm is evaluated using real field measurements in terms of accuracy and convergence time.

Channel congestion is one of the major challenges for IEEE 802.11p-based vehicular ad hoc networks. To tackle the challenge, several algorithms have been proposed and some of them are being considered for standardization. Situations could arise where vehicles with different algorithms operate in the same network. Our previous work has investigated the performance of a mixed-algorithm vehicular network for the CAM-DCC and LIMERIC algorithms and identified that the CAM-DCC vehicles could potentially experience a performance degradation after introducing the LIMERIC vehicles into the network. In this work, we study whether it is possible to eliminate or bound this degradation. We propose a CBP target adjustment mechanism which controls the CBP target of LIMERIC vehicles according to vehicle density and mixing situation of the two algorithms in the network to limit the performance degradation of CAM-DCC vehicles to a desired level. The proposed mechanism is evaluated via both MATLAB and ns-2 simulations and the simulation results indicate that the performance degradation of the CAM-DCC vehicles is controlled as expected with only negligible impact on the performance of LIMERIC vehicles, which still perform similar or better than CAM-DCC vehicles.

It is our great pleasure to welcome you to the 3rd IEEE Workshop on Smart Vehicles: Connectivity Technologies and ITS Applications (SmartVehicles'16), which is held in conjunction with the 13th IEEE International Symposium on a World of Wireless Mobile and Multimedia Networks (WoWMoM'16). The aim of this workshop is to bring together academics, industry professionals, and application developers to presents recent developments, current research challenges, and future directions in the area of connected and smart transportation.

Channel congestion is one of the major challenges for IEEE 802.11p-based vehicular networks. Unless controlled, congestion increases with vehicle density, leading to high packet loss and degraded safety application performance. We study two classes of congestion control algorithms, i.e., reactive state-based and linear adaptive. In this paper, the reactive state-based approach is represented by the decentralized congestion control framework defined in the European Telecommunications Standards Institute. The linear adaptive approach is represented by the LInear MEssage Rate Integrated Control (LIMERIC) algorithm. Both approaches control safety message transmissions as a function of channel load [i.e., channel busy percentage (CBP)]. A reactive state-based approach uses CBP directly, defining an appropriate transmission behavior for each CBP value, e.g., via a table lookup. By contrast, a linear adaptive approach identifies the transmission behavior that drives CBP toward a target channel load. Little is known about the relative performance of these approaches and any existing comparison is limited by incomplete implementations or stability anomalies. To address this, this paper makes three main contributions. First, we study and compare the two aforementioned approaches in terms of channel stability and show that the reactive state-based approach can be subject to major oscillation. Second, we identify the root causes and introduce stable reactive algorithms. Finally, we compare the performance of the stable reactive approach with the linear adaptive approach and the legacy IEEE 802.11p. It is shown that the linear adaptive approach still achieves a higher message throughput for any given vehicle density for the defined performance metrics.

Channel congestion is one of the major challenges for IEEE 802.11p-based vehicular ad hoc networks. Facing the challenge, several algorithms have been proposed. Two good representatives are the Decentralized Congestion Control (DCC) framework defined by ETSI and LIMERIC, a linear control algorithm. Both algorithms control message transmission rate as a function of channel load (i.e., channel busy percentage, CBP). In this work, DCC is assumed to be deployed for day one applications and LIMERIC is introduced into the network afterwards. Given such a mixed vehicular network with vehicles running either DCC or LIMERIC, we evaluate the performance of the two algorithms in the mixed scenario and study the impact of such mixed network operation on the performance through ns-2 simulations. It is observed that converting some CAM-DCC vehicles to LIMERIC vehicles will not lead to any significant performance degradation of either CAM-DCC or LIMERIC vehicles. Any observed performance degradation is small enough so that we would expect typical DSRC applications to still be feasible. Performance differences between DCC and LIMERIC exist but they can be reduced through careful selection of the specific parameters of LIMERIC and DCC, respectively.

Emerging applications rely on wireless broadcast to disseminate time-critical information. For example, vehicular networks may exchange vehicle position and velocity information to enable safety applications. The number of nodes in one-hop communication range in such networks can be very large, leading to congestion and undesirable levels of packet collisions. Earlier work has examined such broadcasting protocols primarily from a MAC perspective and focused on selective aspects such as packet error rate. In this work, we propose a more comprehensive metric, the average system information age, which captures the requirement of such applications to maintain current state information from all other nearby nodes. We show that information age is minimized at an optimal operating point that lies between the extremes of maximum throughput and minimum delay. Further, while age can be minimized by saturating the MAC and setting the CW size to its throughput-optimal value, the same cannot be achieved without changes in existing hardware. Also, via simulations we show that simple contention window size adaptations like increasing or decreasing the window size are unsuitable for reducing age. This motivates our design of an application-layer broadcast rate adaptation algorithm. It uses local decisions at nodes in the network to adapt their messaging rate to keep the system age to a minimum. Our simulations and experiments with 300 ORBIT nodes show that the algorithm effectively adapts the messaging rates and minimizes the system age.

One of the most important challenges for DSRC deployment is maintaining high performance under heavy channel load. The study of congestion control mechanisms will be impractical if it requires hundreds of physical radios deployed on vehicles. In this paper we demonstrate two important results that together suggest a strategy for investigating congestion control. First, we show that the NS-2 simulator accurately models the MAC and PHY associated with an IEEE 802.11 hardware implementation. This opens the door to using simulation as the primary investigative tool. Second, we show that a technique in which one radio emulates N vehicles can produce results quite similar to the case in which a larger number of distinct vehicles exist. This will allow selective validation tests with tens of physical radios emulating hundreds of vehicles. The means by which we demonstrate these results is a cross-validation technique. We show that three test approaches produce consistently similar results: physical radios with emulation, NS-2 with emulation, and NS-2 without emulation. The close agreement among these results validates both the radio emulation technique and the NS-2 implementation of the 802.11 MAC and PHY protocols. We use this cross-validation technique to compare results for a wide variety of transmit power, message rate, data rate, channel bandwidth, message size and EDCA settings.

Wireless vehicular communication has the potential to enable a host of new applications, the most important of which are a class of safety applications that can prevent collisions and save thousands of lives. The automotive industry is working to develop the dedicated short-range communication (DSRC) technology, for use in vehicle-to-vehicle and vehicle-to-roadside communication. The effectiveness of this technology is highly dependent on cooperative standards for interoperability. This paper explains the content and status of the DSRC standards being developed for deployment in the United States. Included in the discussion are the IEEE 802.11p amendment for wireless access in vehicular environments (WAVE), the IEEE 1609.2, 1609.3, and 1609.4 standards for Security, Network Services and Multi-Channel Operation, the SAE J2735 Message Set Dictionary, and the emerging SAE J2945.1 Communication Minimum Performance Requirements standard. The paper shows how these standards fit together to provide a comprehensive solution for DSRC. Most of the key standards are either recently published or expected to be completed in the coming year. A reader will gain a thorough understanding of DSRC technology for vehicular communication, including insights into why specific technical solutions are being adopted, and key challenges remaining for successful DSRC deployment. The U.S. Department of Transportation is planning to decide in 2013 whether to require DSRC equipment in new vehicles.

In the US, the Dedicated Short Range Communications (DSRC) spectrum is organized into several channels. IEEE 1609.4 [2] defines an alternating-access channel switching scheme to enable a DSRC device to support applications concurrently on different channels. The default channel for Vehicle-to-Vehicle (V2V) safety messages is the Control Channel (CCH), but previous research has identified performance issues with this safety communication model. This paper proposes three alternative approaches for DSRC V2V safety communication in a multi-channel environment, all of which improve performance compared to the basic IEEE 1609.4 approach, while requiring only minor changes to the standards. The alternative approaches and the basic IEEE 1609.4 approach are evaluated via ns-2 simulations.

This paper proposes an approach to Traffic Engineering that uses differentiated services (diffserv) and multi-protocol label switching (MPLS) to provide quantitative QoS guarantees over an IP network. An algorithm that determines QoS-constrained routes is proposed and a framework that uses such an algorithm is outlined. This framework removes the responsibility of QoS guarantees from the core nodes, thereby reducing their complexity.

An examination is made of the mean-square-error performance of an IIR (infinite impulse response) adaptive filter. The principal goal is to determine if IIR adaptive filters have an advantage over FIR (finite impulse response) adaptive filters in terms of either greater performance or less restrictive processing constraints. A stochastic analysis of the IIR algorithm, which results in a steady-state mean square error expression, is presented and that result is used as a tool to investigate performance in the echo canceller application. Simulations are used to verify the analytical result. The echo canceller study shows that the IIR algorithm offers approximately a 2:1 reduction in processing requirements compared to the FIR approach, without loss of performance.>

An analysis is presented of the bias produced in the composite regressor algorithm. This study contains what the authors believe is the first analytical demonstration that there is bias in the output error algorithm when the algorithm is used with a small but nonvanishing adaptation step size. The analysis provides insight into general bias properties of infinite-impulse-response adaptive filtering algorithms.>

A relation between equation error and output-error adaptive algorithms is presented. It leads to a clarified view of output-error bias and stability. It is shown that a tradeoff between desirable stability and bias characteristics can be achieved in output error by manipulation of the adaptive gain. The composite regressor algorithm (CRA) is introduced as a means of affecting this tradeoff, independent of the gain. Output error is shown to a special case of CRA. A stability constraint for CRA is developed in a theorem, and the bias properties of this algorithm are discussed.>