Title Predviđanje jakosti elektromagnetskog polja u bežičnim lokalnim mrežama zasnovano na neuronskom modelu i optimizaciji rojem čestica
Title (english) Electromagnetic Field Strength Prediction in Wireless Local Area Networks Based on Neural Network Model and Particle Swarm Optimization
Author Ivan Vilović
Mentor Robert Nađ (mentor)
Committee member Zvonimir Šipuš (predsjednik povjerenstva)
Committee member Robert Nađ (član povjerenstva)
Committee member Nikša Burum (član povjerenstva)
Committee member Juraj Bartolić (član povjerenstva)
Committee member Lavoslav Čaklović (član povjerenstva)
Granter University of Zagreb Faculty of Electrical Engineering and Computing (Department of Communication and Space Technologies) Zagreb
Defense date and country 2008-12-05, Croatia
Scientific / art field, discipline and subdiscipline TECHNICAL SCIENCES Electrical Engineering
Universal decimal classification (UDC ) 621.3 - Electrical engineering
Abstract Ova disertacija se bavi problemom rasprostiranja elektromagnetskog polja u zatvorenom prostoru, gdje je vrlo teško dobiti toènu razdiobu polja. Kvalitetnu vezu s okosnicom komunikacijskog sustava omoguæuju pristupne toèke, koje trebaju biti pažljivo rasporeðene kako bi prostor bio pokriven odgovarajuæom snagom signala. Opæenito razlikujemo jednostavne i složene prostore. Složeni prostori imaju neparalelne i hrapave zidove s nepoznatom dielektrièkom konstantom u odnosu na geometrijski pravilne, jednostavne prostore. Razdioba polja kod jednostavnih prostora se može utvrditi nekom od empirijskih ili deterministièkih metoda. U našem sluèaju korištena je Motley-Keenan i metoda slijeðenja zrake u svrhu predviðanja snage polja u bilo kojoj toèki jednostavnog prostora. Bolji rezultati se postižu, ako se elektromagnetski parametri zidova dobiju mjerenjem. U tu svrhu razvijena je nedestruktivna mjerna metoda zasnovana na mjerenjima koeficijenata refleksije i prijenosa u slobodnom prostoru. Iz dobivenih rezultata izluèena je kompleksna dielektrièka konstanta. Navedene metode, praktièki, nije moguæe primijeniti na složeni prostor, pa je u našem sluèaju primijenjen neuronski model za predviðanje snage signala. Kao rezultat istraživanja upotrijebljen je višeslojni perceptron za konfiguraciju mreže. Ulazi u neuronsku mrežu su koordinate položaja pristupnih i prijamnih toèaka, a izlaz je odgovarajuæa snaga polja. Levenberg-Marquardt algoritam s Bayesovom regulacijom je odabran za uèenje neuronske mreže, kao rezultat istraživanja tri razlièita algoritma uèenja. Neuronski model je testiran na stvarnom složenom prostoru, èija geometrijska i konstrukcijska složenost onemoguæuje primjenu bilo koje druge metode. Neuronska mreža je obuèavana i testirana s izmjerenim snagama polja na raznim toèkama prijama. Dobiveni rezultati potvrðuju ispravnost pristupa. Osim za predviðanje razdiobe polja, neuronska mreža je upotrebljena i za odreðivanje optimalnog položaja pristupne toèke. Optimizacijski postupak je proveden algoritmom zasnovanim na roju èestica (PSO). Rezulati su usporeðeni s vrijednostima dobivenim algoritmom zasnovanim na mravljoj koloniji i genskim algoritmom. Algoritam zasnovan na roju èestica daje toènije rezultate i brže se izvodi na raèunalu od algoritma zasnovanog na mravljoj koloniji, a jednako je toèan kao i genski algoritam.
Abstract (english) This dissertation deals with an indoor propagation problem where it is difficult to rigorously obtain the field strength distribution. Access points need to provide good link to the communications backbone of the system. They need to be positioned carefully so that they cover the building with appropriate signal level. Commonly environments can be distinguished as simple or complex ones. The complex environments include non-parallel and non-smooth walls with unknown permittivity. The field strength distribution in the simple environments with parallel walls can be determined by some empirical or deterministic method. Motley-Keenan and ray tracing methods are used to predict field strength at any receiving point of the simple environment. The better results are obtained with ray tracing method when the values of electromagnetic parameters of the walls are obtained by measurements. A free space non-destructive method is introduced for measurement of reflection and transmission coefficients and complex dielectric constant extraction. Application of these methods to the complex environment is very difficult with not accurate results. Absence of real accurate method for the signal strength prediction in indoor environment enables usage of the neural network methods in this area. The neural modeling process includes theoretical and experimental investigations that result in the model based on multilayer perceptron. Inputs are the positions (coordinates) of the access points and of the receiving points, while the output has one neuron to obtain relevant signal strength level. As a training rule we have selected the algorithm that updates the weight and the bias values according to Levenberg-Marquardt optimization model with Bayes regularization. This choice is a result of extensive investigation where neural network architecture and three different learning algorithms have been analyzed. The selected model is tested at particular building environment, such that it's geometrical and construction complexity makes the application of any analytical method to be very difficult. The neural network is trained and tested with measured field strength at various receiving points. The results are very promising. Such trained neural network is used for predicting the field strength distribution as well as for prediction of the optimum access point position. The optimization process for optimal access point position is performed with the PSO algorithm which results are compared with results of Ant Colony Optimization (ACO) and Genetic algorithm. The results show PSO as faster and more accurate algorithm in comaprison with ACO algorithm, but equal accuarte as genetic algorithm.
Keywords
Jednostavni prostor
složeni prostor
bežièna lokalna mreža
rasprostiranje elektromagnetskog polja
pristupna toèka
slijeðenje zrake
koeficijent refleksije
koeficijent prijenosa
kompleksna dielektrièka konstanta
neuronska mreža
Levenberg-Marquardt algoritam s Bayesovom regulacijom
optimizacijski algoritam roja èestica
optimizacijski algoritam mravlje kolonije
genski algoritam
Keywords (english)
Simple environment
complex environment
Wireless Local Area Network (WLAN)
electromagnetic propagation
access point
ray tracing
reflection coefficient
transmission coefficient
complex dielectric constant
neural network
Levenberg-Marquardt algorithm with Bayes regularization
particle swarm optimization algorithm
ant colony optimization algorithm
genetic algorithm.
Language croatian
URN:NBN urn:nbn:hr:168:220972
Project Number: 036-0361566-1570 Title: Elektromagnetski učinci i strukture u komunikacijskim sustavima Leader: Zvonimir Šipuš Jurisdiction: Croatia Funder: MZOS Funding stream: ZP
Project Number: 275-0000000-3260 Title: Integralna kvaliteta usluge komunikacijskih i informacijskih sustava Leader: Vladimir Lipovac Jurisdiction: Croatia Funder: MZOS Funding stream: ZP
Project Number: 275-0361566-3136 Title: Radijske i optičke senzorske komunikacijske mreže Leader: Nikša Burum Jurisdiction: Croatia Funder: MZOS Funding stream: ZP
Study programme Title: Postgraduate master programme in electrical engineering Study programme type: university Study level: postgraduate Academic / professional title: Magistar znanosti elektrotehnike (Magistar znanosti elektrotehnike)
Catalog URL http://lib.fer.hr/cgi-bin/koha/opac-detail.pl?biblionumber=33064
Type of resource Text
Extent 158 str.
File origin Born digital
Access conditions Closed access
Terms of use
Created on 2020-03-19 11:07:53