Wireless Sensor Networks (WSNs) are a significant technology attracting considerable research interest. Recent advances in wireless communications and electronics have enabled the development of low-cost, low-power and multi-functional sensors that are small in size and communicate over short distances. Most WSN applications require knowing or measuring locations of thousands of sensors accurately. For example, sensing data without knowing the sensor location is often meaningless. Locations of sensor nodes are fundamental to providing location stamps, locating and tracking objects, forming clusters, and facilitating routing. This research focused on the modeling and implementation of distributed, mobile radar sensor networks. In particular, we worked on the problem of Position-Adaptive Direction Finding (PADF), to determine the location of a non- collaborative transmitter, possibly hidden within a structure, by using a team of cooperative intelligent sensor networks. Position-Adaptive radar concepts have been formulated and investigated at the Air Force Research Laboratory (AFRL) within the past few years. In this paper, we present the simulation performance analysis on the application aspect. We apply Extremum Seeking Control (ESC) schemes by using the swarm seeking problem, where the goal is to design a control law for each individual sensor that can minimize the error metric by adapting the sensor positions in real-time, thereby minimizing the unknown estimation error. As a result we achieved source seeking and collision avoidance of the entire group of the sensor positions.
In recent years there has been growing interest in Ad-hoc and Wireless Sensor Networks (WSNs) for a variety
of indoor applications. Thus, recent developments in communications and RF technology have enabled system
concept formulations and designs for low-cost radar systems using state-of-the-art software radio modules.
Position-Adaptive radar concepts have been formulated and investigated at the Air Force Research Laboratory
(AFRL) within the past few years. Adopting a position-adaptive approach to the design of distributed radar
systems shows potential for the development of future radar systems that function under new and challenging environments
that contain large clutter discretes and require co-functionality within multi-signal RF environments.
In this paper, we present the simulation performance analysis on the application aspect. We apply Extremum
Seeking Control (ESC) schemes by using the swarm seeking problem, where the goal is to design a control law
for each individual sensor that can minimize the error metric by adapting the sensor positions in real-time based
on cross-path loss exponents estimates between sensors, thereby minimizing the unknown estimation error. As
a result we achieved source seeking and collision avoidance of the entire group of the sensor positions.
In recent years, position based services has increase. Thus, recent developments in communications and RF technology
have enabled system concept formulations and designs for low-cost radar systems using state-of-the-art
software radio modules. This research is done to investigate a novel multi-platform RF emitter localization technique
denoted as Position-Adaptive RF Direction Finding (PADF). The formulation is based on the investigation
of iterative path-loss (i.e., Path Loss Exponent, or PLE) metrics estimates that are measured across multiple
platforms in order to autonomously adapt (i.e. self-adjust) of the location of each distributed/cooperative platform.
Experiments conducted at the Air-Force Research laboratory (AFRL) indicate that this position-adaptive
approach exhibits potential for accurate emitter localization in challenging embedded multipath environments
such as in urban environments. The focus of this paper is on the robustness of the distributed approach to
RF-based location tracking. In order to localize the transmitter, we use the Received Signal Strength Indicator
(RSSI) data to approximate distance from the transmitter to the revolving receivers. We provide an algorithm
for on-line estimation of the Path Loss Exponent (PLE) that is used in modeling the distance based on Received
Signal Strength (RSS) measurements. The emitter position estimation is calculated based on surrounding
sensors RSS values using Least-Square Estimation (LSE). The PADF has been tested on a number of different
configurations in the laboratory via the design and implementation of four IRIS wireless sensor nodes as receivers
and one hidden sensor as a transmitter during the localization phase. The robustness of detecting the
transmitters position is initiated by getting the RSSI data through experiments and then data manipulation in
MATLAB will determine the robustness of each node and ultimately that of each configuration. The parameters
that are used in the functions are the median values of RSSI and rms values. From the result it is determined
which configurations possess high robustness. High values obtained from the robustness function indicate high
robustness, while low values indicate lower robustness.
This paper provides a summary of recent results on a novel multi-platform RF emitter localization technique denoted as
Position-Adaptive RF Direction Finding (PADF). This basic PADF formulation is based on the investigation of iterative
path-loss based (i.e. path loss exponent) metrics estimates that are measured across multiple platforms in order to
robotically/intelligently adapt (i.e. self-adjust) the location of each distributed/cooperative platform. Recent results at the
AFRL indicate that this position-adaptive approach shows potential for accurate emitter localization in challenging
embedded multipath environments (i.e., urban environments). As part of a general introductory discussion on PADF
techniques, this paper provides a summary of our recent results on PADF and includes a discussion on the underlying
and enabling concepts that provide potential enhancements in RF localization accuracy in challenging environments.
Also, an outline of recent results that incorporate sample approaches to real-time multi-platform data pruning is included
as part of a discussion on potential approaches to refining a basic PADF technique in order to integrate and perform
distributed self-sensitivity and self-consistency analysis as part of a PADF technique with distributed robotic/intelligent
features. The focus of this paper is on the experimental performance analysis of hardware-simulated PADF
environments that generate multiple simultaneous mode-adaptive scattering trends. We cite approaches to addressing
PADF localization performance challenges in these multi-modal complex laboratory simulated environments via
providing analysis of our multimodal experiment design together with analysis of the resulting hardware-simulated
PADF data.
This paper provides a summary of preliminary RF direction finding results generated within an AFOSR funded testbed
facility recently developed at Louisiana Tech University. This facility, denoted as the Louisiana Tech University Micro-
Aerial Vehicle/Wireless Sensor Network (MAVSeN) Laboratory, has recently acquired a number of state-of-the-art
MAV platforms that enable us to analyze, design, and test some of our recent results in the area of multiplatform
position-adaptive direction finding (PADF) [1] [2] for localization of RF emitters in challenging embedded multipath
environments. Discussions within the segmented sections of this paper include a description of the MAVSeN Laboratory
and the preliminary results from the implementation of mobile platforms with the PADF algorithm. This novel approach
to multi-platform RF direction finding is based on the investigation of iterative path-loss based (i.e. path loss exponent)
metrics estimates that are measured across multiple platforms in order to develop a control law that
robotically/intelligently positionally adapt (i.e. self-adjust) the location of each distributed/cooperative platform. The
body of this paper provides a summary of our recent results on PADF and includes a discussion on state-of-the-art
Sensor Mote Technologies as applied towards the development of sensor-integrated caged-MAV platform for PADF
applications. Also, a discussion of recent experimental results that incorporate sample approaches to real-time singleplatform
data pruning is included as part of a discussion on potential approaches to refining a basic PADF technique in
order to integrate and perform distributed self-sensitivity and self-consistency analysis as part of a PADF technique with
distributed robotic/intelligent features. These techniques are extracted in analytical form from a parallel study denoted as
"PADF RF Localization Criteria for Multi-Model Scattering Environments". The focus here is on developing and
reporting specific approaches to self-sensitivity and self-consistency within this experimental PADF framework via the
exploitation of specific single-agent caged-MAV trajectories that are unique to this experiment set.
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