Ali J. Ghandour

Improving reliability of safety applications in vehicle ad hoc networks through the implementation of a cognitive network

Researchers have suggested Vehicular Ad hoc Networks as a way to enable car to car communications and to allow for the exchange of safety and other types of information among cars. The Wireless Access in Vehicular Environments (WAVE) protocol stack is standardized by the IEEE, and it allocates spectrum for vehicular communication. In our work we prove that it does not provide sufficient spectrum for reliable exchange of safety information. To alleviate this problem, we present a system that employs cognitive network principles to increase the spectrum allocated to the control channel (CCH) by the WAVE protocols, where all safety information is transmitted. To accomplish this objective, the proposed system relies on sensed data sent by the cars to road side units that in turn forward the aggregated data to a processing unit. The processing unit infers data contention locations and generates spectrum schedules to dispatch to the passing cars. Analysis and simulation results indicate the effectiveness of the system in improving data delivery in vehicular networks and thus increasing the reliability of safety applications.

Data delivery guarantees in congested Vehicular ad hoc networks using cognitive networks

The Wireless Access in Vehicular Environments (WAVE) protocol stack is one of the most important protocols used to allocate spectrum for vehicular communication. In a previous work, we proved that WAVE does not provide sufficient spectrum for reliable exchange of safety information. More specifically, safety message delay is not acceptable and exceeds application requirements. In this paper, we propose a system that provides Data delivery guarantees using Cognitive networks principles in congested Vehicular ad hoc networks. We will refer to our system as DCV. Our goal is to ensure that all safety packets get generated and transmitted during the same interval. The system monitors the contention delay experienced by cars on the control channel where all safety packets should be transmitted. If the sensed contention delay exceeds delay threshold γ, the Road Side Unit (RSU) needs to increase the spectrum allocated to the control channel using cognitive networks. The RSU employs a feedback control design where additional bandwidth is added to drive the contention delay below the delay threshold γ used as reference input for the controller. Analysis and simulations indicate the effectiveness of the system in providing data delivery guarantees in vehicular networks and thus increasing safety measures on the road.

Dissemination of Safety Messages in IEEE 802.11p/WAVE Vehicular Network: Analytical Study and Protocol Enhancements

Abstract Multi-channel IEEE WAVE 1609.4 protocol has been proposed to guarantee the co-existence of safety and non-safety applications over the same Vehicular Ad hoc NETwork (VANET) scenario. While the usage of multi-channel avoids the risk of collisions between applications allocated on different frequencies, its implementation on a single-radio transceiver poses some major concerns about the effective utilization of the channel resources. In this paper, we study the performance of safety applications over multi-channel single-radio VANETs, and we present three novel contributions in this regard. First, we propose an analytical analysis and a simulation study of IEEE 1609.4. We show the harmful impact of synchronous channel switching on the message delay and delivery ratio. Second, we investigate the problem of dissemination of safety broadcast messages over multi-channel VANETs, where the network is intermittently disconnected, due to the alternation of control and service intervals. Finally, we propose a WAVE-enhanced Safety message Delivery (WSD) scheme to enable fast dissemination of safety messages over multi-channel VANETs, while guaranteeing compatibility with the existing WAVE stack. To this aim, we formulate the dissemination problem as a multi-channel scheduling problem. We further introduce cooperation among vehicles to reduce the dissemination latency. Simulation study shows the ability of the WSD scheme to enhance the performance of IEEE 1609.4 in terms of message delay and delivery ratio under different topologies and various applications.

A proxy-based architecture for dynamic discovery and invocation of web services from mobile devices

Mobile devices are getting more pervasive, and it is becoming increasingly necessary to integrate web services into applications that run on these devices. We introduce a novel approach for dynamic...Mobile devices are getting more pervasive, and it is becoming increasingly necessary to integrate web services into applications that run on these devices. We introduce a novel approach for dynamically invoking web service methods from mobile devices with minimal user intervention that only involves entering a search phrase and values for the method parameters. The architecture overcomes technical challenges that involve consuming discovered services dynamically by introducing a man-in-the-middle (MIM) server that provides a web service whose responsibility is to discover needed services and build the client-side proxies at runtime. The architecture moves to the MIM server energy-consuming tasks that would otherwise run on the mobile device. Such tasks involve communication with servers over the Internet, XML-parsing of files, and on-the-fly compilation of source code. We perform extensive evaluations of the system performance to measure scalability as it relates to the capacity of the MIM server in handling mobile client requests, and device battery power savings resulting from delegating the service discovery tasks to the server.

Enhancing the performance of safety applications in IEEE 802.11p/WAVE Vehicular Networks

Recently, the IEEE 1609.4 WAVE protocol has been proposed to enable multi-channel communication in Vehicular Ad Hoc Networks (VANETs). While the usage of multi-channel technology can favor the co-existence of safety and non-safety vehicular applications, its implementation on single-radio transceivers poses some major concerns about the effective utilization of the channel resources. In this paper, we investigate the performance of safety-related applications on multi-channel VANETs. We demonstrate that the synchronous channel switching operations enforced by the IEEE 1609.4 protocol introduce additional delays to the delivery of safety messages, that might compromise the viability of such applications. To cope with this problem, we propose a WAVE-enhanced Safety message Delivery scheme (WSD) that minimizes the delivery delay of safety messages in multi-channel VANETs, while preserving compatibility with the IEEE 1609.4/802.11p standards. WSD attempts to transmit high priority safety message during SCH intervals while guaranteeing reception by all neighbors. We formulate the broadcast problem in multi-channel VANETs as a scheduling problem over the different DSRC channels. We extend the problem formulation to cooperative scenarios, in which multiple vehicles contribute to disseminate the safety message over the different channels. We evaluate our proposed WSD scheme through a simulation study. We show that our proposed solution can provide effective reduction of the delivery delay in multi-channel VANETs, when compared to the legacy IEEE 1609.4/802.11p protocols.

Slow port scanning detection

Port scanning is the most popular reconnaissance technique attackers use to discover services they can break into. Port scanning detection has received a lot of attention by researchers. However a slow port scan attack can deceive most of the existing Intrusion Detection Systems (IDS). In this paper, we present a new, simple, and efficient method for detecting slow port scans. Our proposed method is mainly composed of two phases: (1) a feature collection phase that analyzes network traffic and extracts the features needed to classify a certain IP as malicious or not. (2) A classification phase that divides the IPs, based on the collected features, into three groups: normal IPs, suspicious IPs and scanner IPs. The IPs our approach classify as suspicious are kept for the next (K) time windows for further examination to decide whether they represent scanners or legitimate users. Hence, this approach is different than the traditional approach used by IDSs that classifies IPs as either legitimate or scanners, and thus producing a high number of false positives and false negatives. A small Local Area Network was put together to test our proposed method. The experiments show the effectiveness of our proposed method in correctly identifying malicious scanners when both normal and slow port scan were performed using the three most common TCP port scanning techniques. Moreover, our method detects malicious scanners that are otherwise not detected using well known IDSs such as Snort.

Improving vehicular safety message delivery through the implementation of a cognitive vehicular network

The Wireless Access in Vehicular Environments (WAVE) protocol stack has been recently defined to enable vehicular communication on the Dedicated Short Range Communication (DSRC) frequencies. Some recent studies have demonstrated that the WAVE technology might not provide sufficient spectrum for reliable exchange of safety information over congested urban scenarios. In this paper, we address this issue, and present a novel cognitive network architecture in order to dynamically extend the Control Channel (CCH) used by vehicles to transmit safety-related information. To this aim, we propose a cooperative spectrum sensing scheme, through which vehicles can detect available spectrum resources on the 5.8GHz ISM band along their path, and forward the data to a fixed infrastructure known as Road Side Units (RSUs). We design a novel Fuzzy-Logic based spectrum allocation algorithm, through which the RSUs infer the actual CCH contention conditions, and dynamically extend the CCH bandwidth in network congestion scenarios, by using the vacant frequencies detected by the sensing module. The simulation results reveal the effectiveness of our architecture in providing dynamic and scalable allocation of spectrum resources, and in increasing the performance of safety-related applications.

On the Impact of Multi-Channel Technology on Safety-Message Delivery in IEEE 802.11p/1609.4 Vehicular Networks

The IEEE 1609.4-Multi-Channel Operation protocol has been proposed to support the co-existence of safety and non-safety (infotainments) applications over the Dedicated Short Range Communication (DSRC) channels at the 5.9 GHz band. However, the multi- channel approach over a single-radio transceiver might result in several performance degradations that have not been thoroughly investigated yet. In this paper, we analyze the performance of safety- related applications over multi-channel vehicular networks. We demonstrate through a simulation study that the synchronous channel switching enforced by the IEEE 1609.4 protocol might easily compromise the performance of safety applications that rely on the periodic exchange of short lived broadcasts. Thus, we propose in this work the WAVE-enhanced Adaptive Broadcast (WAB) scheme. WAB provides a novel MAC contention control mechanism intended to reduce the impact of packet collisions caused by the synchronous channel switching, and to increase the packet delivery rate of broadcast messages in congested vehicular scenarios. The WAB scheme dynamically adapts to the channel conditions through a distributed load estimator metric, and implements priority mechanisms to ensure fairness among vehicles. Simulation results reveal that the proposed WAB scheme can significantly increase the packet delivery rate of broadcast messages when compared to the existing IEEE 802.11p/1609.4 scheme.

An infrastructure-aided cooperative spectrum sensing scheme for vehicular ad hoc networks

The Wireless Access in Vehicular Environments (WAVE) protocol stack has been recently defined to enable vehicular communication on the Dedicated Short Range Communication (DSRC) frequencies. Recent studies have demonstrated that the Control Channel (CCH) of the DSRC protocol on which all vehicular safety messages are sent might not provide sufficient spectrum for reliable exchange of safety information over congested urban scenarios. In this paper, we develop a scheme that calls for collecting spectrum sensing measurements by cars and then aggregating these measurements by Road Side Units (RSUs) to assess the state of the spectrum on road segments. We propose to opportunistically use the white spaces in the spectrum as an extension of the crowded Control Channel (CCH) for the next passing cars. A blind detector is applied and tested on the cars level, which takes advantage of their mobility to span a large area of the roads and deliver more accurate decisions in dynamic vehicular environments. To ensure homogeneity in the sensing samples among cars, we make the sensing rate of the cars dependent on their traveling speed. A fusion and decision algorithm is employed by Road Side Units (RSUs) to aggregate the individual sensing data and decide on the vacancy of the sensed frequency bands. The performance of the sensing and decision algorithms are evaluated and tested in various vehicular scenarios using the network simulator ns2. The obtained results prove the effectiveness of the system in detecting available ISM channels.

Transient Current Testing of Gate-Oxide Shorts in CMOS

We propose a method for testing gate-oxide shorts due to pinhole defects in the gate oxide of CMOS circuits using the transient power supply current, iDDT. The method is based on switching the CMOS gate, monitoring the peak value of the transient current and comparing it to that of the defect-free gate. If the magnitude of the peak current is higher than a predetermined threshold, a defect is inferred. The MOS transistor is modeled using the nonlinear split model. We take into consideration the different locations and sizes of the short. Simulation results show a high rate of detection for gate-oxide shorts that cannot be otherwise detected using traditional testing techniques. We also show that by using a normalization procedure, the defects can be detected with a single threshold setup in the presence of leakage and process variations that normally hinder the detection capability of current-based testing techniques.