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We outline guiding principles for choosing the subband bandwidth of a multicarrier system with multiple antennas. Initially, we review considerations for the choice of bandwidth in fast-fading doubly dispersive channels. We append to these considerations those relevant to the use of multiple antennas for intereference rejection in the wideband regime. To weigh the benefits of narrow subbands, which...
Civil aviation is continuing to grow, and along with growth in numbers of flights and passengers comes growth in communications. In particular airport surface environments are one of the areas in which rapid development of communication systems is taking place. Several years ago the Federal Aviation Administration, EUROCONTROL, and the International Civil Aviation Organization proposed a communication...
We present an optimal frame timing estimator for OFDM signals that utilizes both cyclic prefix (CP) and pilot-carrier-aided channel estimation. Combining the periodic nature of the embedded pilot signal information with the correlation present in the cyclic prefix allows improved frame timing estimates relative to use of either one. Following a derivation of the ML estimator, a processor diagram is...
Edge windowing is a windowing technique for Orthogonal Frequency Division Multiplexing (OFDM) signals based on the idea of using shorter cyclic prefix (CP) and longer window lengths at the edge subcarriers while keeping the symbol length fixed. In this study, we investigate the performance of OFDM signals with edge windowing under non-linear power amplifier (PA) effects by observing out-of-band (OOB)...
The SSL protocol has been widely used for verifying digital identities and to secure Internet traffic since the early days of the web. Although X.509 certificates have been in existence for more than two decades, individual user uptake has been low due to the high cost of issuance and maintenance of such certs. This has led to a situation whereby users are able to verify the identity of an organization...
Over the years, system calls (syscalls) have become an increasingly popular data source for host intrusion detection systems (HIDS). This is partly due to their strong security semantic implications. As syscalls conform to a program's control-flow graph, a deviation in a syscall sequence may imply a deviation in a program's control-flow graph. This is useful for detecting the control-flow hijacking...
As the complexity and number of cybersecurity incidents are growing, the traditional security measures are not sufficient to defend against attackers. In this situation, cyber threat intelligence capability substantially improves the detection and prevention of the sophisticated attacks. Cybersecurity information sharing is a key factor of threat intelligence, allowing organizations to detect and...
This paper presents a novel approach to launch and defend against the causative and evasion attacks on machine learning classifiers. As the preliminary step, the adversary starts with an exploratory attack based on deep learning (DL) and builds a functionally equivalent classifier by polling the online target classifier with input data and observing the returned labels. Using this inferred classifier,...
Cyber-Physical Systems (CPS) such as Unmanned Aerial Systems (UAS) sense and actuate their environment in pursuit of a mission. The attack surface of these remotely located, sensing and communicating devices is both large, and exposed to adversarial actors, making mission assurance a challenging problem. While best-practice security policies should be followed, they are rarely enough to guarantee...
Covert/side channel attacks based on electromagnetic (EM) emanations are difficult to detect because they are practiced wirelessly. Hence, quantifying information leakage is crucial when designing secure hardware and software. To address this problem, this paper establishes a connection between the signal energy available to an attacker in electromagnetic side/covert channel and capacity of the covert/side...
Data assurance and resilience are crucial security issues in cloud-based IoT applications. With the widespread adoption of drones in IoT scenarios such as warfare, agriculture and delivery, effective solutions to protect data integrity and communications between drones and the control system have been in urgent demand to prevent potential vulnerabilities that may cause heavy losses. To secure drone...
The rapidly growing presence of Internet of Things (IoT) devices is becoming a continuously alluring playground for malicious actors who try to harness their vast numbers and diverse locations. One of their primary goals is to assemble botnets that can serve their nefarious purposes, ranging from Denial of Service (DoS) to spam and advertisement fraud. The most recent example that highlights the severity...
Range extension via the use of small aircraft with highly directional antennas that act as relays is a topic of interest in military network technology development. Antenna elements in such designs typically have limited field-of-view (FoV), potentially making interconnectedness among communication nodes dependent on the geometry of the physical network. This paper examines a generic sectorized pod...
Communications survivability of mobile wireless segments in tactical military networks is and will be an enormous challenge in the present and future defence forces, which is vital to fulfill military missions in a timely manner. We have previously presented an autonomous system named OPAL, which uses distributed cooperative management solutions for enhancing communications survivability in volatile...
Software Defined Networking (SDN) is rapidly gaining acceptance and use in terrestrial networks but little research has been done to apply it to aerial networks. This paper describes an investigation into five open-source controllers using a specific set of criteria based on the characteristics of these networks. A preliminary qualitative investigation compares the controllers based on their state...
The future of sensor systems is moving quickly to the realm of distributed multi-static RF Internet of Things (RIOTs). In this case, any single sensor is limited in its ability to generate useful information but the community of sensors, networked together, create the necessary information. Specifically, the ability to geolocate and track small Unmanned Aerial Systems (UASs) with a set of distributed...
Wireless communications networks are often modeled as graphs in which the vertices represent wireless devices and the edges represent the communication links between them. However, graphs fail to capture the time-varying nature of wireless networks. Temporal networks are graphs in which the sets of nodes or edges are time-varying. We consider the most common case, in which the set of nodes is fixed...
An online learning problem with side information is considered. The problem is formulated as a graph structured stochastic Multi-Armed Bandit (MAB). Each node in the graph represents an arm in the bandit problem and an edge between two arms indicates closeness in their mean rewards. It is shown that such side information induces a Unit Interval Graph and several graph properties can be leveraged to...
Coordination among workers within a collaborative team environment is a key factor to its success but it is challenging to come up with a general model for relative costs and benefits of coordination. In a typical work environment, teams with sufficient aggregate expertise are selected to work on an incoming sequence of tasks one by one; it is often the case that the cost of coordination among the...
A new synthesis scheme is proposed to effectively generate a random vector with prescribed joint density that induces a (latent) Gaussian tree structure. The quality of synthesis is measured by total variation distance between the synthesized and desired statistics. The proposed layered and successive encoding scheme relies on the learned structure of tree to use minimal number of common random variables...
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