Performance Analysis for Direction of Arrival Estimating Algorithms

Smart antennas have emerged as one of the most promising directions in supporting maximum communication link throughput. In this paper, we have investigated the impact of smart antennas on a complex mobile network such as a railroad wireless communications system. The objective is to analyze the selection of a Direction-Of-Arrival (DOA) estimation algorithm which provides the maximum efficiency when deployed in our railroad testbeds for wireless vehicular communication. Our findings are discussed to provide an indepth understanding of how different algorithms should be selected to support efficient network operations

A Study On Energy Efficient Multi-Tier Multi-Hop Wireless Sensor Networks For Freight-Train Monitoring

The North American freight railroad industry is trying to leverage wireless sensor networks (WSN) onboard railcars for advanced monitoring and alerting. In railroad environments, freight train WSNs exhibit a linear chain-like topology of significant length. Thus, existing wireless technologies such as the IEEE 802.15.4 communication protocol, based on a star topology, are unable to provide reliable service. The end-to-end communication between nodes generally relies on individual nodes communicating with their respective neighbors to carry the information over multiple hops and deliver it to the preferred destination. The routing performance and reliability significantly degrades with increasing number of hops. We proposed a multitier multi-hop network which is designed to overcome these issues in large-scale multi-hop WSNs in railroad environments. This approach has significant advantages, such as more data bandwidth, higher reliability, and lower energy consumption. Our analytical results show that the proposed multi-tier communication approach spends energy more efficiently and utilizes less resource than the traditional chain topology on board freight trains

Priority Preemption for Real-time Application QoS Guarantees in Cooperative Vehicular Networks

Inter-vehicle and roadside-to-vehicle communications can contribute to a safer and more efficient driving experience by providing time-sensitive and location-aware information. However, its performance suffers from vehicle mobility, intermittent user connectivity, and wireless channel unreliability. In this paper, we propose a novel cross-layer optimization approach based on our Adaptive Distributed Cooperative Medium Access Control (ADC-MAC) protocol to guarantee the quality-of-service (QoS) of real-time applications. Markov chain based theoretical analysis show that our proposed priority preemption approach can improve the quality of a real-time application by guaranteeing its bandwidth and reducing its transmission latency

A Quantitative Performance Analysis of 2.5 GHz and 3.65 GHz Mobile WiMAX

Mobile WiMAX has emerged as a prime contender for the de-facto ITU’s 4G standard. It provides high data rate with large coverage and vehicular mobility support. It has been, and is being, widely deployed in diverse applications like video streaming, broadcasting and data service. The FCC (Federal Communications Commission) issues licenses to operate Mobile WiMAX services in several spectrums, among which 2.5 GHz and 3.65 GHz are the most common. Because the 2.5 GHz spectrum suffers the least propagation losses, it has been widely applied commercially. For this reason, academic and industrial researchers have given it particular attention. However, in some cases, the 3.65 GHz is often a better choice, in spite of having a lower coverage, particularly due to its favorable licensing requirements. Due to limited amount of work published in the 3.65 GHz spectrum, the concerned parties do not have sufficient data to reliably select the spectrum. In this research work, a thorough quantitative analysis of the two Mobile WiMAX spectrums, 2.5 GHz and 3.65 GHz, are presented and compared. Actual physical testing of commercial equipment in real-world settings has been done to provide a generic overview of the performance of the two spectrums. The results presented serve multiple purposes. First, they provide reliable technical data for decision-making. Second, they can be used for link budget analysis. Finally, they can be utilized as benchmarks for future testing and quality control of equipment production. It is shown that the maximum achievable downlink throughput for the 2.5 GHz and the 3.65 GHz systems is around 22 Mbps and 21 Mbps respectively. Assuming an average user bandwidth demand of Mbps, they can both reliably serve 40 to 45 users within a coverage radius of 12 km and 8 km respectively. Other than the lower coverage, opting for the 3.65 GHz spectrum over the 2.5 GHz spectrum will cause no significant performance loss and should be preferred if the loss of coverage can be tolerated. Advisor: Hamid R. Sharif-Kashan

An innovative approach to analyze and detect a broad class of timing-based covert communications

Transmitting information by hiding it in order to evade detection has been practiced since ancient times. In the modern age of computing, digital objects and resources—such as images, video and text files—are used as carriers of hidden information. Recently, an entirely different method of information hiding that leverages existing network resources as side channels for transmitting secret messages has received considerable attention. Since these network resources were not even designed for the purpose of communication, traditional network security elements such as firewalls cannot detect them. These side channels are called covert channels. Covert channels can be used for leaking information and exchanging messages between maligned parties without being detected. This makes covert channels a serious security concern and hence it is imperative to prevent, detect and disrupt them. Due to the sheer number of covert channel algorithms, it is impossible to deal with them on a case-by-case basis. In this research, an analytical framework that can broadly define all covert timing channels through a mathematical model has been proposed and investigated. From this model, equations have been derived to characterize covert communications in terms of bit error rate under different channel conditions for four popular and diverse covert timing channels. The model was verified by implementing the same algorithms in MATLAB and on a test-bed of real network traffic. A machine learning-based generic detection mechanism has also been proposed. Statistical fingerprints were derived from the traffic under investigation, which served as feature points for training a Support Vector Machine-based framework. Four types of fingerprints—Kolmorov-Smirnov test score, Regularity score, Entropy and Corrected Conditional Entropy—were used for this purpose. The presented model was then tested against an independent set of feature points derived from an arbitrary traffic under investigation. Results show that the mechanism is very efficient in blind and generalized detection of covert channels. The presented approach and results have been published in national and international conferences and journals

Assessment of durability performance of "Early-Opening-to-Traffic" Portland Cement Concrete pavement and patches

Due to the character of the original source materials and the nature of batch digitization, quality control issues may be present in this document. Please report any quality issues you encounter to [email protected], referencing the URI of the item.Includes bibliographical references (leaves 112-128).Issued also on microfiche from Lange Micrographics.This study relates the assessment of durability to ''early-opening-to-traffic'' (EOT) portland cement concrete (PCC). Several factors were identified relative to the performance of EOT PCC. Each of these factors was considered in terms of freeze-thaw, shrinkage, chemical attack, abrasion resistance, fatigue life, volumetric expansion, practicality, and concrete costs. The assessment discusses material combinations, mixture designs, and construction practices on performance. A computer program using utility decision theory was applied in evaluating the parameters. Promising combinations of the above factors were determined based on the existing knowledge of material combinations used for EOT PCC, coupled with our understanding of the potentials of high performance concrete (HPC) for this type of application

Geography

Class 8 (Nepali Date: 2053); Language: Nepal

Geography

Class 8 (Nepali Date: 2053); Language: Nepal

A General Attack Method for Steganography Removal Using Pseudo-CFA Re-interpolation

Watermarking and steganography are two of the most researched topics in multimedia forensics. However, easy availability of tools and technology has made their misuse a serious concern. To counteract this development some effective tools are necessary to remove malicious steganography. In this work, we introduce a novel watermark attack method which can destroy hidden information embedded in images based on the principle of re-interpolation of Color Filter Array (CFA) artifacts. In digital cameras and scanners, CFA filters are used to acquire low-resolution physical color channel information and produce a high-quality image by subsequent interpolation. We propose to emulate a similar scheme in which image information is removed and reconstructed through interpolation and thereby destroy any hidden information without impairing the visual quality. Most importantly, our presented method is general and does not assume any knowledge of the used watermarking methods, the hidden message or the host image

Achieving Robustness and Capacity Gains in Covert Timing Channels

In this paper, we introduce a covert timing channel (CTC) algorithm and compare it to one of the most prevailing CTC algorithms, originally proposed by Cabuk et al. CTC is a form of covert channels – methods that exploit network activities to transmit secret data over packet-based networks – by modifying packet timing. This algorithm is a seminal work, one of the most widely cited CTCs, and the foundation for many CTC research activities. In order to overcome some of the disadvantages of this algorithm we introduce a covert timing channel technique that leverages timeout thresholds. The proposed algorithm is compared to the original algorithm in terms of channel capacity, impact on overt traffic, bit error rates, and latency. Based on our simulation results the proposed algorithm outperforms the work from Cabuk et al., especially in terms of its higher covert data transmission rate with lower latency and fewer bit errors. In our work we also address the desynchronization problem found in Cabuk et al.’s algorithm in our simulation results and show that even in the case of the synchronization-corrected Cabuk et al. algorithm our proposed method provides better results in terms of capacity and latency