267 research outputs found
Improvement of range-free localization technology by a novel DV-hop protocol in wireless sensor networks
International audienceLocalization is a fundamental issue for many applications in wireless sensor networks. Without the need of additional ranging devices, the range-free localization technology is a cost-effective solution for low-cost indoor and outdoor wireless sensor networks. Among range-free algorithms, DV-hop (Distance Vector - hop) has the advantage to localize the mobile nodes which has less than three neighbour anchors. Based on the original DV-hop algorithm, this paper presents two improved algorithms (Checkout DV-hop and Selective 3-Anchor DV-hop). Checkout DV-hop algorithm estimates the mobile node position by using the nearest anchor, while Selective 3-Anchor DV-hop algorithm chooses the best 3 anchors to improve localization accuracy. Then, in order to implement these DV-hop based algorithms in network scenarios, a novel DV-hop localization protocol is proposed. This new protocol is presented in detail in this paper, including the format of data payloads, the improved collision reduction method E-CSMA/CA, as well as parameters used in deciding the end of each DV-hop step. Finally, using our localization protocol, we investigate the performance of typical DV-hop based algorithms in terms of localization accuracy, mobility, synchronization and overhead. Simulation results prove that Selective 3-Anchor DV-hop algorithm offers the best performance compared to Checkout DV-hop and the original DV-hop algorithm
Multiple Offsets Multilateration : A New Paradigm for Sensor Network Calibration with Unsynchronized Reference Nodes
Positioning using wave signal measurements is used in several applications, such as GPS systems, structure from sound and Wifi based positioning. Mathematically, such problems require the computation of the positions of receivers and/or transmitters as well as time offsets if the devices are unsynchronized. In this paper, we expand the previous state-of-the-art on positioning formulations by introducing Multiple Offsets Multilateration (MOM), a new mathematical framework to compute the receivers positions with pseudoranges from unsynchronized reference transmitters at known positions. This could be applied in several scenarios, for example structure from sound and positioning with LEO satellites. We mathematically describe MOM, determining how many receivers and transmitters are needed for the network to be solvable, a study on the number of possible distinct solutions is presented and stable solvers based on homotopy continuation are derived. The solvers are shown to be efficient and robust to noise both for synthetic and real audio data.©2022 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.fi=vertaisarvioitu|en=peerReviewed
Simultaneous ranging and self-positioning in unsynchronized wireless acoustic sensor networks
Automatic ranging and self-positioning is a very
desirable property in wireless acoustic sensor networks (WASNs)
where nodes have at least one microphone and one loudspeaker.
However, due to environmental noise, interference and multipath
effects, audio-based ranging is a challenging task. This paper
presents a fast ranging and positioning strategy that makes use
of the correlation properties of pseudo-noise (PN) sequences for
estimating simultaneously relative time-of-arrivals (TOAs) from
multiple acoustic nodes. To this end, a proper test signal design
adapted to the acoustic node transducers is proposed. In addition,
a novel self-interference reduction method and a peak matching
algorithm are introduced, allowing for increased accuracy in
indoor environments. Synchronization issues are removed by
following a BeepBeep strategy, providing range estimates that
are converted to absolute node positions by means of multidimensional
scaling (MDS). The proposed approach is evaluated both
with simulated and real experiments under different acoustical
conditions. The results using a real network of smartphones and
laptops confirm the validity of the proposed approach, reaching
an average ranging accuracy below 1 centimeter.This work was supported by the Spanish Ministry of Economy and Competitiveness under Grant TIN2015-70202-P, TEC2012-37945-C02-02 and FEDER funds
TDOA based positioning in the presence of unknown clock skew
Cataloged from PDF version of article.This paper studies the positioning problem of a
single target node based on time-difference-of-arrival (TDOA)
measurements in the presence of clock imperfections. Employing
an affine model for the behaviour of a local clock, it is observed
that TDOA based approaches suffer from a parameter of the
model, called the clock skew. Modeling the clock skew as a
nuisance parameter, this paper investigates joint clock skew and
position estimation. The maximum likelihood estimator (MLE)
is derived for this problem, which is highly nonconvex and
difficult to solve. To avoid the difficulty in solving the MLE, we
employ suitable approximations and relaxations and propose two
suboptimal estimators based on semidefinite programming and
linear estimation. To further improve the estimation accuracy,
we also propose a refining step. In addition, the Cramer-Rao ÂŽ
lower bound (CRLB) is derived for this problem as a benchmark.
Simulation results show that the proposed suboptimal estimators
can attain the CRLB for sufficiently high signal-to-noise ratios
PASSIVE TIME SYNCHRONIZATION IN SENSOR NETWORKS USING OPPORTUNISTIC FM RADIO SIGNALS
ABSTRACT
Time synchronization is a critical piece of infrastructure for any wireless sensor network. It is necessary for applications such as audio localization, beam-forming, velocity calculation, and duplicate event detection. All of which require the coordination of multiple nodes.
Recent advances in low-cost, low-power wireless sensors have led to an increased interest in large-scale networks of small, wireless, low-power sensor nodes. Because of the more stringent power and cost requirements that this technology is driving, current time synchronization techniques must be updated to capitalize on these advances.
One time synchronization method developed specifically for wireless sensor networks is Reference Broadcast Synchronization. In RBS, a reference broadcast is transmitted to sensor nodes that require synchronization. Be recording the time of arrival, nodes can then use those time stamps to synchronize with each other.
This project aimed to make the RBS system even more robust, energy efficient, and cost effective by replacing the reference broadcast with an ambient RF signal (FM, TV, AM, or satellite signals) already prevalent in the environment. The purpose of this project was to demonstrate the viability of using Opportunistic RF synchronization by 1.) quantifying error, 2.) applying this synchronization method in a real world application, and 3.), implementing a wireless sensor network using Android smart phones as sensor nodes.
Many of the objectives for the project were successfully completed. For convenience and economic reasons, an FM signal was chosen as the reference broadcast. FM Radio Synchronization error was then quantified using local FM Radio stations. The results of this experiment were very favorable. Using 5 second segments for correlation, total error was found to be 0.208±4.499Όs. Using 3 second segments, average error was 2.33 ± 6.784Όs. Using 400ms segments, synchronization error was calculated to be 4.76 ± 8.835Όs. These results were comparable to sync errors of methods currently in widespread use.
It was also shown that Opportunistic RF Synchronization could be used in real world applications as well. Again FM was the RF signal of choice. FM Radio Synchronization was tested in an Audio Localization experiment with favorable results.
Implementation of an Android Wireless Sensor Network according to our specifications, however, could not be achieved. HTC EVO 4Gâs were programmed to communicate through TCP / IP network connections, record audio with a microphone, and to record FM Radio streams from the EVOâs internal FM radio. Although recording these two sources separately as different data tracks was successful, simultaneous recording of these streams could not be accomplished (simultaneous recording is essential for Opportunistic RF Synchronization).
Although the Android smart phone implementation was not a total success, this project still provided data that supported the practical use of Opportunistic RF Synchronization.AFRLNo embarg
TDOA Based Positioning in the Presence of Unknown Clock Skew
This paper studies the positioning problem of a single target node based on time-difference-of-arrival (TDOA) measurements in the presence of clock imperfections. Employing an affine model for the behaviour of a local clock, it is observed that TDOA based approaches suffer from a parameter of the model, called the clock skew. Modeling the clock skew as a nuisance parameter, this paper investigates joint clock skew and position estimation. The maximum likelihood estimator (MLE) is derived for this problem, which is highly nonconvex and difficult to solve. To avoid the difficulty in solving the MLE, we employ suitable approximations and relaxations and propose two suboptimal estimators based on semidefinite programming and linear estimation. To further improve the estimation accuracy, we also propose a refining step. In addition, the CrameÌr-Rao lower bound (CRLB) is derived for this problem as a benchmark. Simulation results show that the proposed suboptimal estimators can attain the CRLB for sufficiently high signal-to-noise ratios
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