Cooperative subcarrier sensing using antenna diversity based weighted virtual sub clustering

The idea of cooperation and the clustering amongst cognitive radios (CRs) has recently been focus of attention of research community, owing to its potential to improve performance of spectrum sensing (SS) schemes. This focus has led to the paradigm of cluster based cooperative spectrum sensing (CBCSS). In perspective of high date rate 4th generation wireless systems, which are characterized by orthogonal frequency division multiplexing (OFDM) and spatial diversity, there is a need to devise effective SS strategies. A novel CBCSS scheme is proposed for OFDM subcarrier detection in order to enable the non-contiguous OFDM (NC-OFDM) at the physical layer of CRs for efficient utilization of spectrum holes. Proposed scheme is based on the energy detection in MIMO CR network, using equal gain combiner as diversity combining technique, hard combining (AND, OR and Majority) rule as data fusion technique and antenna diversity based weighted clustering as virtual sub clustering algorithm. Results of proposed CBCSS are compared with conventional CBCSS scheme for AND, OR and Majority data fusion rules. Moreover the effects of antenna diversity, cooperation and cooperating clusters are also discussed

Three Decades of Deception Techniques in Active Cyber Defense -- Retrospect and Outlook

Deception techniques have been widely seen as a game changer in cyber defense. In this paper, we review representative techniques in honeypots, honeytokens, and moving target defense, spanning from the late 1980s to the year 2021. Techniques from these three domains complement with each other and may be leveraged to build a holistic deception based defense. However, to the best of our knowledge, there has not been a work that provides a systematic retrospect of these three domains all together and investigates their integrated usage for orchestrated deceptions. Our paper aims to fill this gap. By utilizing a tailored cyber kill chain model which can reflect the current threat landscape and a four-layer deception stack, a two-dimensional taxonomy is developed, based on which the deception techniques are classified. The taxonomy literally answers which phases of a cyber attack campaign the techniques can disrupt and which layers of the deception stack they belong to. Cyber defenders may use the taxonomy as a reference to design an organized and comprehensive deception plan, or to prioritize deception efforts for a budget conscious solution. We also discuss two important points for achieving active and resilient cyber defense, namely deception in depth and deception lifecycle, where several notable proposals are illustrated. Finally, some outlooks on future research directions are presented, including dynamic integration of different deception techniques, quantified deception effects and deception operation cost, hardware-supported deception techniques, as well as techniques developed based on better understanding of the human element.Comment: 19 page

Air Force Institute of Technology Research Report 2016

This Research Report presents the FY16 research statistics and contributions of the Graduate School of Engineering and Management (EN) at AFIT. AFIT research interests and faculty expertise cover a broad spectrum of technical areas related to USAF needs, as reflected by the range of topics addressed in the faculty and student publications listed in this report. In most cases, the research work reported herein is directly sponsored by one or more USAF or DOD agencies. AFIT welcomes the opportunity to conduct research on additional topics of interest to the USAF, DOD, and other federal organizations when adequate manpower and financial resources are available and/or provided by a sponsor. In addition, AFIT provides research collaboration and technology transfer benefits to the public through Cooperative Research and Development Agreements (CRADAs)

Fake Node Attacks on Graph Convolutional Networks

In this paper, we study the robustness of graph convolutional networks (GCNs). Previous works have shown that GCNs are vulnerable to adversarial perturbation on adjacency or feature matrices of existing nodes; however, such attacks are usually unrealistic in real applications. For instance, in social network applications, the attacker will need to hack into either the client or server to change existing links or features. In this paper, we propose a new type of “fake node attacks” to attack GCNs by adding malicious fake nodes. This is much more realistic than previous attacks; in social network applications, the attacker only needs to register a set of fake accounts and link to existing ones. To conduct fake node attacks, a greedy algorithm is proposed to generate edges of malicious nodes and their corresponding features aiming to minimize the classification accuracy on the target nodes. In addition, we introduce a discriminator to classify malicious nodes from real nodes and propose a Greedy-generative adversarial network attack to simultaneously update the discriminator and the attacker, to make malicious nodes indistinguishable from the real ones. Our non-targeted attack decreases the accuracy of GCN down to 0.03, and our targeted attack reaches a success rate of 78% on a group of 100 nodes and 90% on average for attacking a single target node

Evaluation Of Multicarrier Air Interfaces In The Presence Of Interference For L-Band And C-Band Air-Ground Communications

The use of aeronautical vehicles and systems is continuously growing, and this means current aeronautical communication systems, particularly those operating in the very high frequency (VHF) aviation band, will suffer from severe congestion in some regions of the world. For example, it is estimated that air-to-ground (AG) communication traffic density will at least double by 2035 over that in 2012, based on the most-likely growth scenario for Europe. This traffic growth (worldwide) has led civil aviation authorities such as the FAA in the USA, and EuroControl in Europe, to jointly explore development of future communication infrastructures (FCI). According to international aviation systems policies, both current and future AG communication systems will be deployed in L-band (960-1164 MHz), and possibly in C-band (5030-5091 GHz) because of the favorable AG radio propagation characteristics in these bands. During the same time period as the FCI studies, the use of multicarrier communication technologies has become very mature for terrestrial communication systems, but for AG systems it is still being studied and tested. Aiming toward future demands, EuroControl and FAA sponsored work to define several new candidate AG radio systems with high data rate and high reliability. Dominant among these is now an L-Band Digital Aeronautical Communication Systems (L-DACS): L-DACS1. L-DACS1 is a multicarrier communication system based on the popular orthogonal frequency division multiplexing (OFDM) modulation technique. For airport surface area communication systems used in C-band, EuroControl and FAA also proposed another OFDM communication system based on the IEEE 802.16e standard, termed aeronautical mobile airport communication system (AeroMACS). This system has been proposed to provide the growing need of communication traffic in airport environments. In this dissertation, first we review existing and proposed aviation communication systems in VHF-band, L-band and C-band. We then focus our study on the use of multicarrier techniques in these aviation bands. We compare the popular and dominant multicarrier technique OFDM (which is used in cellular networks such long-term evolution (LTE) and wireless local area networks such as Wi-Fi) with the filterbank multicarrier (FBMC) technique. As far as we are aware, we are the first to propose and evaluate FBMC for aviation communication systems. We show, using analysis and computer simulations, along with measurement based (NASA) air-ground and airport surface channel models, that FBMC offers advantages in performance over the OFDM schemes. Via use of sharp filters in the frequency domain, FBMC reduces out of band interference. Specifically, it is more robust to high-power distance measurement equipment (DME) interference, and via replacement of guard bands with data-bearing subcarriers, FBMC can offer higher throughput than the contending L-DACS1 scheme, by up to 23%. Similar advantages over AeroMACS pertain in the airport surface channel. Our FBMC bit error ratio performance is comparable to that of the OFDM schemes, and is even better for our “spectrally-shaped” version of FBMC. For these improvements, FBMC requires a modest complexity increase. Our final contribution in this dissertation is the presentation of spectrally shaped FBMC (SS-FBMC). This idea allocates unequal power to subcarriers to contend with non-white noise or non-white interference. Our adaptive algorithm selects a minimum number of guard subcarriers and then allocates power accordingly to remaining subcarriers based on a “water-filling-like” approach. We are the first to propose such a cognitive radio technique with FBMC for aviation applications. Results show that SSFBMC improves over FBMC in both performance and throughput

Annual Report, 2013-2014

Beginning in 2004/2005- issued in online format onl

Dual-Band Non-Stationary Channel Modeling for the Air-Ground Channel

Multiple air-to-ground (AG) radio propagation channels are experimentally characterized for two frequency bands, C-band and L-band. These characterizations are aimed to support the specification of the control and non-payload communication (CNPC) links being designed for civil unmanned aircraft systems (UAS). The use of UAS is expected to grow dramatically in the coming decades. In the United States, UAS will be monitored and guided in their operation within the national airspace system (NAS) via the CNPC link. The specifications of the CNPC link are being designed by government, industries, academia and standards bodies such as the Radio Technical Commission for Aeronautics (RTCA). Two bands have been allocated for the CNPC applications: from 5030 to 5091 MHz in C-band and a portion of the aeronautical L-band from 960 to 1215 MHz. The project under which this work was conducted is entitled “Unmanned Aircraft Systems Research: The AG Channel, Robust Waveforms, and Aeronautical Network Simulations”, and this is a sub-project of a NASA project entitled “Unmanned Aircraft Systems Integration in the National Airspace System.” Measurements and modeling for radio propagation channels play an essential role in wireless communication system design and performance evaluation; such models estimate attenuation, delay dispersion, and antenna diversity in wireless channels. The AG channel differs significantly from classic cellular, ground-to-satellite, and other terrestrial wireless channels, particularly in terms of antenna heights and velocity. The previous studies about the AG channels are reviewed and the significant gaps are indicated. NASA Glenn Research Center has conducted an AG channel measurement campaign for multiple ground station local environments, including over sea, over freshwater, desert, suburban, near urban, hilly and mountainous settings. In this campaign, over 316 million power delay profiles (PDPs) or channel impulse responses (CIRs), over 82 flight tracks, have been collected. The measurement equipment was a dual-band single-input multiple-output (SIMO) wideband channel sounding system with bandwidth of 50 MHz in C-band and 5 MHz in L-band. Given the dynamic nature of the AG environments, the channels are statistically non-stationary, meaning that the channel’s statistical parameters change over time/space. We have estimated, via two distinct methods, that the stationarity distance is approximately 15 m—this is the distance over which the channel characteristics can be assumed to be wide sense stationary. The AG channel attenuation is considered as a combination of large scale path loss, small scale fading, and airframe shadowing. The large scale path loss is modeled by both the log-distance model and two-ray models. The theoretical flat earth and curved earth two-ray models are presented, along with their limitations, boundaries and some enhancements. Numerous propagation effects in the AG channels are discussed, and this includes earth spherical divergence, atmospheric refraction, atmospheric gas and hydrometeor attenuations, and ducting. The small scale fading is described by the Ricean distribution, which for unit-energy normalizations are completely characterized by Ricean K-factors; these K-factors are approximately 28.7 dB in C-band and 13.1 dB in L-band. The line-of-sight (LOS) signal can be obstructed by the airplane itself in some specific maneuvers, and this is termed airframe shadowing. For the specific flights and NASA aircraft used in our measurements, the shadowing duration was found to be on average 30 seconds, and the shadowing loss can be as large as 40 dB. The statistics, models and simulation algorithm for the airframe shadowing are provided. The wideband characteristics of the AG channel are quantified using root-mean-square delay spread (RMS-DS), and illustrated by sequences of PDPs. Tapped delay line (TDL) models are also provided. Doppler effects for over water channels are also addressed. Given the sparsity of the diffuse multipath components (MPCs) in the AG channels and generally short lifetime of these MPCs, the CIRs are modeled by the two-ray model plus intermittent 3rd, 4th or 5th “rays.” Models for intermittent ray probability of occurrence, duration, relative power, phase, and excess delay are provided. The channels at C-band and L-band were found to be essentially uncorrelated; this conclusion holds for the specific antenna locations used in our experiments (the aircraft underside), but is not expected to change for arbitrary antenna locations. For the aircraft antenna locations employed, intra-band signals are highly correlated, and this is as expected for channels with a dominant LOS component; analytical correlation computations show interesting two-ray effects that also appear in measurements. Multiple aircraft antennas and carefully selected locations are recommended for mitigating airframe shadowing for the CNPC link. Future work for AG channel modeling includes characterization of L-band delay dispersion and L-band TDL models, estimation of building and/or tree shadowing for small UAS that fly at very low altitudes, evaluation of multiple ground site(s) antenna diversity, and AG channel modeling via geometric techniques, e.g., ray-tracing

On-device Security and Privacy Mechanisms for Resource-limited Devices: A Bottom-up Approach

This doctoral dissertation introduces novel mechanisms to provide on-device security and privacy for resource-limited smart devices and their applications. These mechanisms aim to cover five fundamental contributions in the emerging Cyber-Physical Systems (CPS), Internet of Things (IoT), and Industrial IoT (IIoT) fields. First, we present a host-based fingerprinting solution for device identification that is complementary to other security services like device authentication and access control. Then, we design a kernel- and user-level detection framework that aims to discover compromised resource-limited devices based on behavioral analysis. Further we apply dynamic analysis of smart devices’ applications to uncover security and privacy risks in real-time. Then, we describe a solution to enable digital forensics analysis on data extracted from interconnected resource-limited devices that form a smart environment. Finally, we offer to researchers from industry and academia a collection of benchmark solutions for the evaluation of the discussed security mechanisms on different smart domains. For each contribution, this dissertation comprises specific novel tools and techniques that can be applied either independently or combined to enable a broader security services for the CPS, IoT, and IIoT domains