1,207 research outputs found
Advances in Decentralized Single-Beacon Acoustic Navigation for Underwater Vehicles: Theory and Simulation
This paper reports the theory and implementation
of a decentralized navigation system that enables simultaneous
single-beacon navigation of multiple underwater vehicles. In
single-beacon navigation, each vehicle uses ranges from a single,
moving reference beacon in addition to its own inertial navigation
sensors to perform absolute localization and navigation. In this
implementation the vehicles perform simultaneous communication
and navigation using underwater acoustic modems, encoding
and decoding data within the acoustic broadcast. Vehicles calculate
range from the time of flight of asynchronous acoustic
broadcasts from the reference beacon. Synchronous clocks on
the reference beacon and the vehicles enable the measurement
of one-way travel-times, whereby the time of launch of the
acoustic signal at the reference beacon is encoded in the acoustic
broadcast and the time of arrival of the broadcast is measured
by each vehicle. The decentralized navigation algorithm, running
independently on each vehicle, is implemented using the
information form of the extended Kalman filter and has been
previously shown to yield results that are identical to a centralized
Kalman filter at the instant of each range measurement. We
summarize herein the architecture and design of the acoustic
communications (Acomms) system consisting of an underwater
acoustic modem, synchronous clock, and the software necessary
to run them, and salient results from the validation of the
decentralized information filter using a simulated data set.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/86057/1/swebster-4.pd
Nanosecond-precision Time-of-Arrival Estimation for Aircraft Signals with low-cost SDR Receivers
Precise Time-of-Arrival (TOA) estimations of aircraft and drone signals are
important for a wide set of applications including aircraft/drone tracking, air
traffic data verification, or self-localization. Our focus in this work is on
TOA estimation methods that can run on low-cost software-defined radio (SDR)
receivers, as widely deployed in Mode S / ADS-B crowdsourced sensor networks
such as the OpenSky Network. We evaluate experimentally classical TOA
estimation methods which are based on a cross-correlation with a reconstructed
message template and find that these methods are not optimal for such signals.
We propose two alternative methods that provide superior results for real-world
Mode S / ADS-B signals captured with low-cost SDR receivers. The best method
achieves a standard deviation error of 1.5 ns.Comment: IPSN 201
A Survey of Positioning Systems Using Visible LED Lights
© 2018 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.As Global Positioning System (GPS) cannot provide satisfying performance in indoor environments, indoor positioning technology, which utilizes indoor wireless signals instead of GPS signals, has grown rapidly in recent years. Meanwhile, visible light communication (VLC) using light devices such as light emitting diodes (LEDs) has been deemed to be a promising candidate in the heterogeneous wireless networks that may collaborate with radio frequencies (RF) wireless networks. In particular, light-fidelity has a great potential for deployment in future indoor environments because of its high throughput and security advantages. This paper provides a comprehensive study of a novel positioning technology based on visible white LED lights, which has attracted much attention from both academia and industry. The essential characteristics and principles of this system are deeply discussed, and relevant positioning algorithms and designs are classified and elaborated. This paper undertakes a thorough investigation into current LED-based indoor positioning systems and compares their performance through many aspects, such as test environment, accuracy, and cost. It presents indoor hybrid positioning systems among VLC and other systems (e.g., inertial sensors and RF systems). We also review and classify outdoor VLC positioning applications for the first time. Finally, this paper surveys major advances as well as open issues, challenges, and future research directions in VLC positioning systems.Peer reviewe
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Wireless indoor localisation within the 5G internet of radio light
This thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University LondonNumerous applications can be enhanced by accurate and efficient indoor localisation using wireless
sensor networks, however trade-offs often exist between these two parameters. In this thesis, realworld
and simulation data is used to examine the hybrid millimeter wave and Visible Light
Communications (VLC) architecture of the 5G Internet of Radio Light (IoRL) Horizon 2020 project.
Consequently, relevant localisation challenges within Visible Light Positioning (VLP) and asynchronous
sampling networks are identified, and more accurate and efficient solutions are developed.
Currently, VLP relies strongly on the assumed Lambertian properties of light sources.
However, in practice, not all lights are Lambertian. To support the widespread deployment of VLC
technology in numerous environments, measurements from non-Lambertian sources are analysed to
provide new insights into the limitations of existing VLP techniques. Subsequently, a novel VLP
calibration technique is proposed, and results indicate a 59% accuracy improvement against existing
methods. This solution enables high accuracy centimetre level VLP to be achieved with non-
Lambertian sources.
Asynchronous sampling of range-based measurements is known to impact localisation
performance negatively. Various Asynchronous Sampling Localisation Techniques (ASLT) exist to
mitigate these effects. While effective at improving positioning performance, the exact suitability of
such solutions is not evident due to their additional processes, subsequent complexity, and increased
costs. As such, extensive simulations are conducted to study the effectiveness of ASLT under variable
sampling latencies, sensor measurement noise, and target trajectories. Findings highlight the
computational demand of existing ASLT and motivate the development of a novel solution. The
proposed Kalman Extrapolated Least Squares (KELS) method achieves optimal localisation
performance with a significant energy reduction of over 50% when compared to current leading ASLT.
The work in this thesis demonstrates both the capability for high performance VLP from non-
Lambertian sources as well as the potential for energy efficient localisation for sequentially sampled
range measurements.Horizon 202
Resilient Peer-to-Peer Ranging using Narrowband High-Performance Software-Defined Radios for Mission-Critical Applications
There has been a growing need for resilient positioning for numerous
applications of the military and emergency services that routinely
conduct operations that require an uninterrupted positioning service.
However, the level of resilience required for these applications is difficult
to achieve using the popular navigation and positioning systems available
at the time of this writing. Most of these systems are dependent on
existing infrastructure to function or have certain vulnerabilities that can
be too easily exploited by hostile forces. Mobile ad-hoc networks can
bypass some of these prevalent issues making them an auspicious topic for
positioning and navigation research and development. Such networks
consist of portable devices that collaborate to form wireless
communication links with one another and collectively carry out vital
network functions independent of any fixed centralized infrastructure.
The purpose of the research presented in this thesis is to adapt the
protocols of an existing narrowband mobile ad-hoc communications
system provided by Terrafix to enable range measuring for positioning.
This is done by extracting transmission and reception timestamps of
signals exchanged between neighbouring radios in the network with the
highest precision possible. However, many aspects of the radios forming
this network are generally not conducive to precise ranging, so the
ranging protocols implemented need to either maneuver around these
shortcomings or compensate for loss of precision caused. In particular,
the narrow bandwidth of the signals that drastically reduces the
resolution of symbol timing. The objective is to determine what level of
accuracy and precision is possible using this radio network and whether
one can justify investment for further development. Early experiments
have provided a simple ranging demonstration in a benign environment,
using the existing synchronization protocols, by extracting time data.
The experiments have then advanced to the radioâs signal processing to
adjust the synchronization protocols for maximize symbol timing
precision and correct for clock drift.
By implementing innovative synchronization techniques to the radio
network, ranging data collected under benign conditions can exhibit a
standard deviation of less than 3m. The lowest standard deviation
achieved using only the existing methods of synchronization was over two
orders of magnitude greater. All this is achieved in spite of the very
narrow 10â20kHz bandwidth of the radio signals, which makes producing
range estimates with an error less than 10â100m much more challenging
compared to wider bandwidth systems. However, this figure is beholden
to the relative motion of neighbouring radios in the network and how
frequently range estimates need to be made. This thesis demonstrates
how such a precision may be obtained and how this figure is likely to hold
up when applied in conditions that are not ideal
An Acoustic Network Navigation System
This work describes a system for acousticâbased navigation that relies on the addition of localization services to underwater networks. The localization capability has been added on top of an existing network, without imposing constraints on its structure/operation. The approach is based on the inclusion of timing information within acoustic messages through which it is possible to know the time of an acoustic transmission in relation to its reception. Exploiting such information at the network application level makes it possible to create an interrogation scheme similar to that of a long baseline. The advantage is that the nodes/autonomous underwater vehicles (AUVs) themselves become the transponders of a network baseline, and hence there is no need for dedicated instrumentation. The paper reports at sea results obtained from the COLLABâNGAS14 experimental campaign. During the sea trial, the approach was implemented within an operational network in different configurations to support the navigation of the two Centre for Maritime Research and Experimentation Ocean Explorer (CMRE OEX) vehicles. The obtained results demonstrate that it is possible to support AUV navigation without constraining the network design and with a minimum communication overhead. Alternative solutions (e.g., synchronized clocks or twoâwayâtravelâtime interrogations) might provide higher precision or accuracy, but they come at the cost of impacting on the network design and/or on the interrogation strategies. Results are discussed, and the performance achieved at sea demonstrates the viability to use the system in real, largeâscale operations involving multiple AUVs. These results represent a step toward locationâaware underwater networks that are able to provide node localization as a service
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