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Author:Koskiahde, Joona
Title:Decentralized Detection in Realistic Sensor Networks
Hajautettu ilmaisu toteutettavissa langattomissa sensoriverkoissa
Publication type:Master's thesis
Publication year:2011
Pages:viii + 49 s. + liitt. 5      Language:   eng
Department/School:Signaalinkäsittelyn ja akustiikan laitos
Main subject:Signaalinkäsittelytekniikka   (S-88)
Supervisor:Richter, Andreas
Instructor:Eriksson, Jan
Electronic version URL: http://urn.fi/URN:NBN:fi:aalto-201209213110
OEVS:
Electronic archive copy is available via Aalto Thesis Database.
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Location:P1 Ark Aalto  897   | Archive
Keywords:decentralized detection
distributed detection
detection theory
sensor networks
acoustic sensors
maximum likelihood
hajautettu ilmaisu
ilmaisuteoria
sensoriverkot
akustiset sensorit
suurimman uskottavuuden menetelmä
Abstract (eng): This thesis discusses the detection of a target using a network of acoustic sensors.
The focus of the work is on considering what to do in a non-ideal situation, where many of the assumptions often made in decentralized detection literature are no longer valid.
The sensors and a fusion center are grouped in an arbitrary formation, and the object is to detect an approaching target which emits a sound signal.
Two different schemes are considered for processing the data at sensors and the fusion center.
One of the schemes is based on maximum likelihood estimation and the other one is a heuristic approach based on classical detection theory.

The performances of the two schemes are studied in simulations.
The heuristic scheme has a better detection performance for a given false alarm rate with all different sets of settings for the simulation.
In derivation of the schemes, the background acoustic noise is assumed to be normal distributed, but, according to the simulations, the schemes still work relatively well under a long tailed noise distribution.
In addition to better performance, the heuristic scheme offers easier setup of threshold values and approximation of false alarm rates for given thresholds using simple equations.
Abstract (fin): Tämä työ käsittelee kohteen ilmaisua sensoriverkolla, joka koostuu äänisensoreista.
Työn pääpaino on epäideaalisen tilanteen käsittelyllä, jossa monet hajautettua ilmaisua käsittelevät oletukset, joita alan kirjallisuudessa tehdään, eivät enää päde.
Sensoriverkko koostuu mielivaltaiseen verkkotopologiaan asetetuista sensoreista ja fuusiokeskuksesta, ja tavoite on ilmaista verkkoa lähestyvä kohde, joka tuottaa äänisignaalia.
Tiedon käsittelyyn sensoreilla ja fuusiokeskuksella esitetään kaksi erilaista algoritmia.
Toinen algoritmeista perustuu suurimman uskottavuuden menetelmään ja toinen on heuristinen, klassiseen ilmaisuteoriaan perustuva, lähestymistapa ongelmaan.

Algoritmien suorituskykyä tutkitaan simulaatioiden avulla.
Heuristisen algoritmin suorituskyky on huomattavasti parempi kaikissa simuloiduissa tilanteissa.
Algoritmien johdossa taustakohina oletettiin normaalijakautuneeksi, mutta simulaatioiden perusteella algoritmit toimivat kohtuullisen hyvin myös pidempihäntäisen taustakohinajakauman tapauksessa.
Heuristinen algoritmi tarjoaa paremman suorituskyvyn lisäksi myös helpomman tavan asettaa kynnysarvoparametrit niin, että sensoreilla ja fuusiokeskuksella on haluttu väärän hälytyksen todennäköisyys.
ED:2012-06-20
INSSI record number: 44697
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