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Sensor array beamforming performance using independently mobile antennas connected through a wireless sensor network is analyzed where a performance metric is proposed enabling mitigation of the perturbation of array factor formation caused by dynamic node positions. Wireless networking has expanded array design possibilities to include wirelessly connected elements; however, static positioning of...
A method is proposed to determine reset timing for phase weight recalculation required in coherent beamforming using wirelessly connected independently mobile nodes to form an array aperture. Without the tether of a wired connection, elements in an array may be independently mobile. However, coherent beam formation requires position data at time of intercept to maintain target focus. Implementing...
A model is proposed to describe expected communications performance between two sensor network nodes where both are unsteady in physical orientation with respect to a specified reference. Model application enables determination of transmit power in terms of a preferred link performance probability. Increasing applications of wireless sensor networks has proportionally increased fielding ideas and...
We present the design of a randomly distributed radio frequency signal detection and reception array constructed of wireless sensor network nodes. The design stresses initial signal detection using the wireless network array. All other array operations depend on detecting a signal of interest prior to activating follow-on sequences of signal processing, potentially including emitter geolocation and...
We present the design of a remotely deployable distributed wireless antenna system formed from wireless sensor network nodes. Specifically, the focus is on enhancing the detection range of a distributed wireless antenna system. The primary objective is to create a methodology to steer the beam in the desired direction to enhance radio frequency (RF) direction finding and follow-on signal reception...
This effort investigated the use of wireless unattended sensor network motes in the surroundings of a freshwater lake. The network was required to organize, establish and maintain itself in or on the water. Commercial components developed by Crossbow Technologies were used in developing the experimental networks consisting of single and multiple nodes. Nodes were tested on a solid ground surface,...
We present an analysis of traffic collected from different topologies of wireless sensor networks. Specifically, over 2.1 million packets were analyzed from two different and commonly used network topologies, namely a direct connection to a base station and a daisy-chained connection to the base. The data traffic between the nodes was captured over a composite period of 180 hours. Using the captured...
We investigate the use of a wireless sensor network for identifying the direction of a radio frequency (RF) transmission. Specifically, we consider the combined use of time difference of arrival (TDOA) and beamforming techniques to steer a beam in the desired direction and enhance radio frequency (RF) direction finding and follow-on signal reception. The TDOA lines-of bearing are calculated using...
The RF characteristics of Mica-Z wireless unattended sensor motes were evaluated for military and commercial applications. The Mica-Z mote's propagation characteristics and network performance were measured under near free- space, indoor and outdoor environments to provide a comprehensive perspective of typical sensor network characteristics. Link break distance and re-association distance with their...
The evaluation of a routing protocol developed by Crossbow Technologies called XMesh is presented. The main components of the routing protocol are described and the routing algorithm explained. Experiments were conducted to determine the connectivity ranges of motes in different transmission power settings. The relationship of mote transmission power and network connectivity is presented. An energy...
Currently wireless multi-hop ad hoc networks utilize protocols that relay packets of data node-by-node along a path connecting the source node to the sink node. This paper describes a new cooperative diversity (CD) methodology for wireless network communications that leverages the fact that RF energy scatters and propagates to many users simultaneously. Specifically, we describe and evaluate a protocol...
This paper presents a model for real-time network monitoring and anomaly detection that provides a holistic view of network conversation exchanges. We argue that monitoring and anomaly detection are necessary mechanisms for ensuring secure and dependable network computing infrastructure. The model for network traffic exchange is based on a modified Ehrenfest urn model and combines statistical physics...
The problem of tracking left-ventricular (LV) endocardial motion from medical images is addressed. This approach accounts for information over two spatial dimensions and time in formulating a displacement flow field of the LV wall viewed as a deformable contour. A two-stage approach consisting of shape-based matching followed by smoothing of the resultant vectors over pairs of successive contours...
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