Argon ST

Fairfax, VA, United States
Fairfax, VA, United States
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Perloff M.,SSCI | Krishnan R.,Argon ST | Ramanathan R.,BBN | Gutierrez C.,SSCI | And 3 more authors.
Proceedings - IEEE Military Communications Conference MILCOM | Year: 2011

As evolving operational requirements compel forces to deploy sparsely there is a need to extend tactical network protocols to operate in the Disruption-Tolerant Networking (DTN) regime, in which frequent disconnections are the norm. In airborne networks 1, connectivity may be temporarily lost when aircraft use different paths to avoid terrain or other obstacles or to perform assigned tasks. In sensor networks, nodes may become disconnected due to environmental conditions or power management, but the set of proximal nodes may not change much over time, despite the intermittent connections. These scenarios challenge standard link-state approaches, both in terms of the protocol overhead and the ability to maintain awareness of all network nodes. Routing protocols designed for the DTN regime, however, cause extreme packet replication to cover the most general conditions conceivable, making them impractical in realistic scenarios. We propose modifications to a widely used link-state protocol, OSPF, to deal with significantly more disruptions to connectivity while retaining the efficiencies of the shortest path approach. We describe simple changes that enable OSPF to find routes through a stable set of neighbors that are only intermittently available. Our use of OSPF minimizes changes and implementation costs, and takes advantage of reliable, proven methods for network state information delivery. We have implemented DTN-extended OSPF within the quagga IP routing framework. Our simulation tests show that, with our modifications, OSPF maintains a global view of the entire network, including both reachable and unreachable nodes, so that messages can be held and routed to temporarily unavailable nodes. Using simulations as well as real packet traffic over an emulated network, we compare DTN-extended OSPF with standard OSPF, and we show that our methods permit messages to be delivered to remote nodes in cases where standard OSPF would discard most or all packets. We conclude by outlining additional methods to reduce DTN overhead traffic and increase DTN-extended OSPF's reliability. © 2011 IEEE.

Hawkinson W.,Honeywell | Samanant P.,Honeywell | McCroskey R.,Honeywell | Ingvalson R.,Honeywell | And 3 more authors.
Record - IEEE PLANS, Position Location and Navigation Symposium | Year: 2012

A system that provides accurate and reliable location of Emergency Responders (ERs) in all types of environments presents multifaceted technological challenges. The system is intended to provide indoor/outdoor precision navigation, robust communications and real-time position updates on remote command display devices. Operational requirements include rapid and nonintrusive deployment, scalability to 500 users and seamless integration with existing procedures. Additional challenges are imposed by the need for a device that minimizes size, weight, and power with the ability to operate in uncertain and potentially hazardous in-building environments. © 2012 IEEE.

Bailey M.C.,Applied EM Inc. | Campbell T.G.,Applied EM Inc. | Reddy C.J.,Applied EM Inc. | Kellogg R.L.,Argon ST | Nguyen P.,U.S. Navy
IEEE Antennas and Propagation Magazine | Year: 2012

In this paper, we describe a compact, wideband (70-3000 MHz), and high-gain antenna technology that can replace multiple types of antennas currently in use to cover the wide frequency band. The design eliminates the frequency-band breaks associated with the use of multiple arrays. The wideband direction-finding array (with a height of 5.5 in and a diameter of 15.5 in) is the result of end-to-end integration of the antenna array with the receivers presently used, or to be used, on platforms of interest. Development of the wide-bandwidth direction-finding antenna array is described, and computer simulations of its performance are presented. The wideband direction-finding antenna system has been verified on the receiver manufacturer's outdoor test range. © 2011 IEEE.

Haas L.,Argon ST | Harlacher M.,Argon ST
Record - IEEE PLANS, Position Location and Navigation Symposium | Year: 2010

The Synthetic Aperture Navigation (SAN) signal processing algorithm identifies the desired line of sight (LOS) signal component by exploiting user motion. As implied by the name, it forms a synthetic aperture along the user trajectory by taking multiple snapshots of signal correlation with the replica waveform over some period of time as the user moves. The synthetic aperture serves as an array, which enables beamforming with a single-element antenna. Fundamentally, this method discriminates between different signal components (e.g., line of sight and multipath) by their directions of arrival. SAN places the antenna array gain on the desired signal component and places nulls on all other components. This operation is applied to data from all correlators in the receiver, thus effectively providing the receiver discriminator with nearly multipath-free measurements. SAN is even able to produce a quality line of sight (LOS) measurement when the LOS component is much weaker than multipath. ©2010 IEEE.

Connor J.,Argon ST | Green T.,Argon ST | Jovancevic A.,Argon ST | Koss J.,Argon ST | And 4 more authors.
Proceedings - IEEE Military Communications Conference MILCOM | Year: 2012

Herein, a solution is presented to address the problem of providing scalable dynamic spectrum awareness for military (and commercial) applications opportunistically using RF devices that are deployed for tasks other than spectrum mapping. We consider challenging urban environments with a large heterogeneous mix of devices and signals. Additional challenges we address include sparsely distributed receivers and the requirement for a system that can be scaled based on the mission and the number of users that must be supported. In order to address these challenges in a scalable distributed fashion, we put forward a solution that uses the following three techniques we have developed: (1) Sparse signal reconstruction techniques to fill in the spatial gaps from limited receiver measurements; (2) Kanerva Sparse Distributed Memory (SDM) to store and retrieve large amounts of data and perform anomaly detection; (3) Feature extraction algorithms to allow for the use of different radio devices that are able to provide varying levels of information. © 2012 IEEE.

Draganov S.,Argon ST | Harlacher M.,Argon ST | Haas L.,Argon ST | Wenske M.,Argon ST | Schneider C.,Argon ST
IEEE Wireless Communications | Year: 2011

Multipath propagation is one of the major error sources for radio navigation systems. While many new applications require ever more precise user positioning in urban and indoor settings, existing receivers are especially vulnerable to severe multipath, which is often present in such environments. This article reviews recent advances in the concept of synthetic aperture navigation, which enables the user to separate co-channel navigation signals, including combating the adverse effects of multipath. A deeply integrated RF receiver and an inertial measurement unit produce an estimate of the user trajectory, which makes it possible to form a synthetic aperture from the user"s motion using a single-element antenna. In turn, using the synthetic aperture opens the door to applying modern direction finding and beamforming methods. These signal processing schemes are able to differentiate between the line of sight and multipath signals (or between different signals in the band in general), as they often arrive from different directions. The desired signal can be extracted in the presence of strong multipath, and its delay can be accurately estimated. © 2011 IEEE.

Draganov A.,Argon ST
26th International Technical Meeting of the Satellite Division of the Institute of Navigation, ION GNSS 2013 | Year: 2013

The Predictor-Corrector Unscented Kalman filter is designed to compute the measurement update for linear or nonlinear measurements. It is backward-compatible with other Kalman filter formulations (e.g., EKF or UKF) in a sense that the filter state is described by the mean and covariance only. At a small additional cost in computational load, this filter delivers a better (sometimes, much better) accuracy than alternatives.

Leong W.,Argon ST | Patel K.,Argon ST | Weinfield J.,Argon ST | Karnick D.,Argon ST
Record - IEEE PLANS, Position Location and Navigation Symposium | Year: 2012

The accuracy of radio frequency based navigation systems is dependent on the precision of ranging measurements, which are greatly limited by multipath propagation in severe environments. Synthetic aperture techniques have been proposed to mitigate the effects of multipath, leveraging user motion with array processing and beamforming techniques to isolate the line of sight component, thus reducing the impacts of propagation. This concept has several advantages, including the ability to obtain accurate line of sight measurements even in the presence of stronger multipath using a single element antenna, and reduced reliance on signal bandwidth to mitigate multipath. To test the algorithm, we designed an experiment in which RF data was collected by a driving user from two beacons, one serving as a control and the other testing synthetic aperture techniques. Here, we quantify Doppler estimation performance of the synthetic aperture techniques for the direction of arrival of the line of sight signal and of multipath in real-world environments. © 2012 IEEE.

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