Postoji sve veći broj primena bežičnih senzorskih mreža (BSM) koje zahtevaju poznavanje lokacije senzorskih čvorova. Osim poznavanja lokacije senzorskih čvorova, nekada je veoma bitno utvrditi i ...lokaciju izvora neke pojave (događaja) koju ovi čvorovi detektuju. Predložen je veliki broj tehnika za procenu lokacije (lokalizaciju) događaja, ipak, i dalje postoje značajni izazovi u pogledu ostvarenja energetske efikasnosti mreže uz postizanje dovoljne tačnosti određivanja lokacije, uz dodatne zahteve u smislu male cene implementacije. U radu je data analiza mogućnosti primene postupka lokalizacije koji se zasniva na iterativnom Bajesovom probabilističkom algoritmu za lokalizaciju radio predajnika čija je lokacija nepoznata, uz dinamički izbor čvorova BSM koji se koriste za lokalizaciju. Osnovni rezultat analize predstavljaju zaključci o uspešnosti i primenjivosti postojećeg postupka lokalizacije u posmatranom scenariju primene u BSM, kao i predlozi za unapređenje i optimizaciju postupka za posmatrani scenario primene u BSM.
Bežični senzori i senzorske mreže postaju zamjena za tradicionalne sustave za praćenje ponašanja konstrukcija. Njihova je prednost u nižoj cijeni ugradnje jer nema potrebe za polaganjem dugih kabela ...između senzora i sustava za prikupljanje podataka. U radu se opisuju istraživanja provedena u svrhu ocjenjivanja učinkovitosti bežičnih senzora za mjerenje relativnih deformacija. Dan je primjer primjene bežičnog senzorskog sustava pri mjerenju ponašanja konstrukcije željezničkog mosta te je napravljena usporedba s primjenom klasičnih sustava.
Provider: - Institution: - Data provided by Europeana Collections- This thesis treats the problem of the network coverage in randomly deployed
wireless sensor networks. Placing the nodes ...quasi-randomly is often the only
way of deploying the network in geographically inaccessible regions. This way
of deployment is often present in military applications. In military
applications, high quality of the network coverage is usually a primary goal,
despite the fact that the nodes cannot be placed manually in the optimal
positions where they would all together provide the highest coverage, a
certain degree of robustness, and redundancy, by using the minimum number of
nodes. Bearing in mind that this kind of installation is usually realized by
using artillery or the aircrafts, before approaching the energy, security,
and reliability optimization, it is important for the application to meet the
basic functionality, i. e., it is important for the values of the basic
parameters that provide a certain degree of the network coverage and
connectivity for a given area of interest to be assessed. The area of
interest can be a region of any shape. In military applications, it is
usually the region of size 5-20km2. If the aim is for the whole area to be
covered, we deal with the area coverage. Another usual example of the
appliance of the wireless sensor networks in military applications is related
to the detection of intruders while attempting to cross the line between two
regions. In this case, we deal with the barrier coverage. This thesis covers
the modeling of the stochastic implementation of the wireless sensor
networks, the analysis of the area and the barrier coverage, as well as the
methods for improving the barrier coverage by using mobile nodes or robots.
Under the initial assumptions and approximations, the conditions for an
expected degree of the specific types of coverage are given for those types
of coverage whose quality can be expressed in terms of the expected detection
probability. But, regarding the strong barrier coverage, instead of assessing
the coverage quality, only the information on barrier coverage creation can
be derived, i.e., a strong barrier coverage can either be accomplished or not
accomplished. According to the theoretical results from literature, it can be
concluded that the full barrier coverage can be achieved almost always if the
very strict conditions are met. These conditions, however, are hard to be
provided. Therefore, in this thesis, two algorithms for creating the full
barrier coverage, by filling the network breaks with mobile nodes or by using
robots, in the situations where these conditions are not met, are proposed.
In order for the algorithms to be implemented, a simulator is developed.
According to the rules defined in algorithms, the simulator determines the
number of breaks, the position and the appropriate number of additionally
needed nodes for the strong barrier coverage to be provided. The simulator
functionality is verified by using the theoretically derived results for the
area coverage and the weak barrier coverage. Instead of using the fully
mobile network, in order to make the price of the network more flexible, the
hybrid networks are considered in this thesis. The proposed algorithms for
improving the strong barrier coverage can be executed in centralized or
distributed manner. To mend the barrier gaps, either mobile nodes (that fill
the gaps and become part of the network just as same as the other stationary
nodes) or mobile robots (that place the stationary nodes into the appropriate
positions) can be used. Algorithms for moving the mobile devices in hybrid
networks are also proposed. Bearing in mind some of the development trends in
system and software engineering, related to improving the efficiency of the
development process by using the appropriate methodologies and machine-based
identification of the data structures, in this thesis, the description of the
technical solution is given in the context of CMMI (Capability Maturity Model
Integration) while the most important aspects of the automatic identification
of the position and the sensing characteristics of the nodes are presented by
using the methodologies of the conceptual modeling.- U ovoj tezi se razmatra problem pokrivenosti bežičnim senzorskim mrežama u
slučaju stohastičkog razmeštaja čvorova u određenom regionu od interesa.
Stohastički razmeštaj čvorova je jedini način instalacije mreže u situacijama
kada je pristup terenu otežan ili nemoguć. Tipični primeri ovog načina
instalacije nalaze se u oblasti vojnih primena. U vojnim aplikacijama,
najčešće je potrebno obezbediti dobru pokrivenost regiona od interesa
senzorskim poljem, bez obzira na činjenicu što se senzori ne mogu manuelno
smestiti u optimalnim pozicijama gde je pokrivenost maksimalna pri minimalnom
broju senzorskih čvorova i pri određenom nivou robusnosti i redundatnosti
mreže. Štaviše, ovakav vid instalacije se može realizovati uglavnom samo
upotrebom artiljerije ili avijacije te je, u ovim uslovima, pre nego što se
pristupi optimizaciji mreže po pitanju potrošnje energije, sigurnosti i
pouzdanosti, potrebno odrediti fundamentalne parametre pri kojima se može
postići osnovna funkcionalnost mreže, odnosno određeni stepen pokrivenosti
područja od interesa i potrebna konektivnost. Područje od interesa može biti
region bilo kojeg oblika. U vojnim aplikacijama, to je najčešće geografsko
područje površine od 5 do 20 . Ako je cilj očitavanje veličina iz čitavog
regiona, govorimo o pokrivenosti regiona. Drugi čest slučaj primene
senzorskih mreža u vojnim aplikacijama, odnosi se na obezbeđivanje određene
linije između dva regiona po pitanju prelaska neprijateljskih vojnih trupa sa
jednog regiona na drugi. U ovom slučaju se govori o pokrivenosti barijere. U
ovoj tezi se vrši modeliranje i analiza stohastičke implementacije bežičnih
senzorskih mreža da bi se, u okviru modela, izvršila evaluacija pokrivenosti
regiona kao i evaluacija i poboljšanje pokrivenosti senzorskom barijerom
korišćenjem mobilnih čvorova ili robota. U ovom pravcu se, pod određenim
početnim pretpostavkama i aproksimacijama, daju uslovi za postizanje
očekivanog nivoa određenog tipa pokrivenosti kao i određivanje uticaja
fundamentalnih parametara mreže na kvalitet pokrivenosti za one tipove
pokrivenosti gde se kvalitet može izraziti u pogledu očekivane verovatnoće
detekcije objekata ili događaja. Međutim, kada je u pitanju sigurna senzorska
barijera, ona može postojati ili ne postojati. U tom smislu se ne može
govoriti o stepenu kvaliteta pokrivenosti već samo o verovatnoći postojanja
jakih (ili sigurnih) senzorskih barijera. Na osnovu teorijskih izvedbi iz
literature, može se zaključiti da je sigurno postojanje jake senzorske
barijere moguće ostvariti samo pod određenim strogim uslovima instalacije.
Međutim, kako su ti uslovi praktično teško ostvarivi, u ovom radu se predlažu
dva algoritma za dopunjavanje mreže koristeći mobilne čvorove ili robote u
uslovima kada nisu zadovoljeni strogi uslovi postojanja jakih senzorskih
barijera. Za implementaciju algoritma se razvija simulator kojim se određuje
pozicija i broj dodatnih mobilnih čvorova potrebnih da bi se u svakoj
situaciji sa velikom verovatnoćom formirala jaka senzorska barijera.
Funkcionalnost simulatora se verifikuje korišćenjem teorijski izvedenih
rezultata za pokrivenost regiona i pokrivenost slabom senzorskom barijerom.
Umesto korišćenja potpuno mobilnih mreža (koje su manje fleksibilne u pogledu
troškova realizacije mreže), ovde se koriste hibridne mreže, gde se
predloženi algoritmi za određivanje pozicija i broja dodatnih čvorova mogu
praktički realizovati na centralizovan ili distribuiran način. Za
dopunjavanje mreže se mogu koristiti mobilni čvorovi (koji se kreću do
određene tačke, a zatim izvršavaju istu funkciju kao i svi ostali statički
čvorovi) ili roboti (koji nose određeni broj fiksnih čvorova i pozicioniraju
ih u određenim tačkama mreže). U okviru teze se takođe predlažu algoritmi za
pomeranje ovih uređaja u cilju ostvarivanja sigurnih senzorskih barijera.
Uzevši u obzir neke trendove razvoja u sistemskom i softverskom inženjerstvu,
koji se odnose na povećanje efikasnosti razvoja rešenja koristeći
odgovarajuće modele unapređivanja procesa i na metodologiju mašinskog
prepoznavanja podatkovnih struktura, u ovoj tezi se daje opis razvoja rešenja
u kontekstu integracionog modela sazrevanja procesa a najvažniji aspekti
procesa automatskog prepoznavanja pozicija i osnovnih funkcionalnih
karakteristika čvorova u zavisnosti od okolnosti instalacije se opisuje kroz
metode konceptualnog modeliranja.- All metadata published by Europeana are available free of restriction under the Creative Commons CC0 1.0 Universal Public Domain Dedication. However, Europeana requests that you actively acknowledge and give attribution to all metadata sources including Europeana
Provider: - Institution: - Data provided by Europeana Collections- The application of diversity technique and majority packet combining is a
simple and attractive solution for error control in ...wireless telecommunication systems. These techniques are especially interesting in
packet-oriented multipath and cooperative networks with one or more
transmitting and receiving antennas. A typical example is wireless sensor
network which often operates in extremely harsh conditions, where
requirements for reliable packet transmission have a higher priority than
requirements for efficient usage of communication capacities. Theoretical and
approximate expressions of packet error probabilities in the case of an
arbitrary number of channels with distinct channel error probabilities are
key parameters for estimation of the energy efficiency of sensor nodes. Goal
of research: As part of this problem, the thesis sets the following
objectives: (i) to obtain theoretical expressions for packet error
probability in the case of application of selective and majority decision
when the number of parallel channels is arbitrary and channel error
probabilities are distinct; analytical expressions are very important in
determining the optimal number of paths in a sensor network in order to
achieve maximum saving of energy in sensor nodes, (ii) to analyze the
throughput efficiency of a hybrid ARQ scheme, considering various scenarios
of packet receiving in the destination node; namely, the presence of spatial
paths, with poor transmission conditions in certain paths, does not provide
guaranteed detection and transmission of frame copies via all paths, so that
the conditions for majority combining may be provided after one or more
retransmissions; therefore, the real scenario is a combination of space and
time diversity in favor of one or the other scenario, (iii) to examine the
possibility of implementation of majority combining, having in mind the known
standards and the usage of existing hardware and software solutions in sensor
networks; the particular focus was given to the modification of solutions
required for the implementation of error correction, based on majority packet
combining. Determining an expression for the retransmission probability is a
challenging problem, especially complex when the number of independent paths
is arbitrary. It was the main reason why almost all authors of published
research papers adopted an unrealistic assumption that channel error
probabilities in independent paths are numerically equal. Even under such
conditions, most authors have limited their research to only three paths. The
exceptions are papers by Carson Lam and co-authors, in which general
solutions for the arbitrary number of paths (channels) are given. In contrast
to this approach, our goal was to derive the general expression that takes
into account both the arbitrary number of paths and distinct values of
channel probabilities. The existence of independent transmission paths
enables the reception of more frame copies. Under normal circumstances,
despite the errors in certain bit positions, let us assume that the presence
of all frame copies will be properly detected. In that case, a complete set
of frame copies will be available at the receiving side, so that, if
necessary, majority combining can be applied. However, there is a real
possibility that it does not recognize the presence of any transmitted frame
copies. This will result in a “deficit” of frame copies, which must be
compensated for by subsequent retransmissions. Various scenarios of packet
collecting for majority decision are possible, such as the case of solving
the problem after the first retransmission, or the case of solving the
problem when the number of retransmissions must be equal or greater than the
number of independent paths. Furthermore, after certain retransmissions, a
“surplus” of frame copies can appear. In such circumstances, the surplus will
create the problem of choosing a suitable “candidate” for majority
decision-making. In any case, the need for retransmission will reduce the
efficiency of the applied method, and it is of interest to investigate this
problem further. In order to obtain an insight in the throughput, three
typical scenarios are selected. Two of them represent extreme cases: one
corresponds to pure space diversity, whereas the other one corresponds to
pure time diversity. The analysis was based on the modeling of the
retransmission process, by using appropriate Markov models to determine the
throughput efficiency based on the mean duration of retransmission cycles.
The attractiveness of applying hybrid ARQ with majority combining scheme lies
in higher simplicity of realization in comparison with other hybrid methods.
This definitely does not mean that the problem is trivial or extremely
simple. To ensure effective implementation, it requires extensive analysis of
available components and modification of available solutions used in wireless
sensor networks. In addition, the initial framework was: (i) to determine the
suitable topological and communication setup of the sensor network; (ii) to
consider and propose modifications to the functions of valid protocols
related to error control in the second layer of the reference model, (iii) to
consider the necessary modifications to transceivers available on the
commercial market; and (iv) to specify in detail the hardware and software
solutions that enable the implementation of majority combining. Research
methods: Each of these outstanding issues have been approached as a separate
topic, using special appropriate telecommunication models and making specific
assumptions to ensure the clarity and relevance of the entire consideration.
Theoretical and simulation methods have been combined. Mathematical analysis
has been performed based on theoretical models, taking into account certain
constrains that imply perfect bit and frame synchronization, slowly
time-varying channel in relation to frame duration, known frame length, etc.
As an aid in derivation of the general expression for packet error
probability in the case of diversity transmission with an arbitrary number of
paths, the principle of inclusion and exclusion from the combinatorics has
been used. Theoretical results have been verified by computer simulation of
realistic models. Results and conclusions: The thesis has included important
theoretical and practical research, which resulted in the following
contributions: (i) the close-form expression is derived for the packet error
probability for three and five channels with distinct channel error
probabilities, (ii) an expression is derived for the packet error probability
in the case of an arbitrary number of channels with distinct channel error
probabilities; a software package based on the general expression has been
created to calculate the packet error probability for arbitrary number of
paths, various frame lengths and distinct channel error probabilities; the
comparative analysis has shown that an additional application of majority
combining can significantly reduce the transmission error probability
compared to selective combining. (iii) suitable approximate expressions have
been developed, allowing for easier understanding of the effect of certain
parameters, such as the number of channels and frame length, on the
transmission error probability, (iv) the concept of equivalent channel
probability has been introduced, which can be used as a good representation
of channels with distinct error probabilities, whose importance is not only
in the simplification of a complex expression for the packet error
probability, but also in the one-dimensional graphics representation of a
function of several variables; it has been illustrated that packet error
probability changes a little irrespective of the relations between individual
channel error probabilities, (v) models of three typical scenarios of packet
transmission from a source to a destination node have been developed and
expressions for the throughput efficiency based on retransmission cycles have
been derived; the effect of key parameters, such as the number of channels,
packet length and normalized round trip delay have been analyzed, (vi) research results have been illustrated in a hypotetical sensor network; the
proposal for modification of the standard that regulates the exchange of data
in low rate wireless sensor networks has been given; it has been proposed
that a frame should contain two separate CRC fields which independently
control MAC header and data payload fields. Further development: The future
research is envisaged in two directions - theoretical and practical. In
theoretical research, the applied methodology could be extended to other
“hard” procedures, such as generalized packet combining and the adaptive
versions of various combining procedures. In practical research, there are
possibilities for more detailed elaboration of hardware and software
solutions, with a view to implementing individual modules and functions of
majority packet combining under appropriate standards. Finally, it is fair to
say that particularly interesting area of application are not only sensor
networks, but also other types of networks and telecommunication systems.- Primena diverziti tehnike i majoritetnog kombinovanja paketa predstavlja jednostavno i atraktivno rešenje za kontrolu grešaka u bežicnim telekomunikacionim sistemima. Ove tehnike su posebno interesantne u paketski orijentisanim mrežama sa višestrukim putanjama i kooperativnim mrežama sa jednom ili više predajnih i prijemnih antena. Tipican primer su bežicne senzorske mreže koje cesto rade u ekstremno otežanim uslovima prenosa, pri cemu zahtevi za pouzdanim prenosom imaju veci prioritet od zahteva za racionalnim korišcenjem komunikacionih kapaciteta. Teorijski i aproksimativni izrazi za verovatnocu pogrešnog prenosa paketa u slucaju proizvoljnog broja kanala sa razlicitim verovatnoca
U radu je razmatrana mogućnost primene ad hoc mobilnih komunikacionih mreža za povezivanje senzorskih sistema, kao čvornih izvora informacija i kao čvornih elemenata komunikacione mrežne ...infrastrukture u okviru komandno-informacionog sistema. Korak u evoluciji bežičnih komunikacija predstavljaju ad hoc mreže koje se javljaju u obliku grupa prenosnih računara, mobilnih telefonskih uređaja, personalnih digitalnih asistenta i sličnih korisničkih uređaja, kao i u obliku mreže autonomnih elektronskih senzorskih uređaja. Osnovnu karakteristiku svake ad hoc mreže predstavlja uspostavljanje komunikacije između mrežnih čvorova bez unapred postavljene fiksne mrežne infrastrukture. Umesto mreže fiksnih čvorova i baznih stanica karakterističnih za postojeću bežičnu mrežnu infrastrukturu, nosilac komunikacije postaje mreža čvornih sofisticiranih senzorskih uređaja - stanica. Mogućnost eliminisanja potrebe fiksne komunikacione infrastrukture u sistemima obezbeđenja i kontrole teritorije od izuzetnog je značaja u vojnim primenama, posebno sa aspekta pripreme i vođenja savremenih operacija. Praćenje situacije u vazdušnom prostoru na osnovu vizuelnih osmatračkih i zvukometrijskih stanica, senzorska zaštita objekata i prostora i prikupljanje relevantnih informacionih podataka predstavljaju samo neke od primera praktične primene ad hoc mreža. / The application possibility of ad hoc mobile communication network for connecting sensor systems, as node sources of information and as node elements of communication network's infrastructure, in command information system is presented in this paper. The next step in wireless communication evolution is ad hoc networks, which appear in the form of groups of mobile computers, mobile phone devices, personal digital assistants and in the form of a network of autonomy electronically sensors devices. The basic characteristic of every ad hoc network is establishing communication between network nodes without fixed network infrastructure, established in advance. Instead of fix network nodes and basic stations, that are typical of available wireless networks infrastructure, network of nodes of sophisticated sensors devices (stations) became most important for communication. Possibility of eliminating the need for fixed communication infrastructure in security systems and systems for territory control, is very important in military, especially for the preparation and leading of modern operations. Some of the examples for practical application of ad hoc networks are: air surveillance system based on visual surveillance and acoustic-metric stations, sensor systems for protection of objects and space and collection of relevant information data.
In this paper, TOA localization model is presented for passive source localization. Localization problem is formulated as an optimization problem with the sum of squared errors as the objective ...function. Gauss-Newton optimization method is applied in order to determine optimal transmitter location. We considered radio channel in the presence of Gaussian noise. Computer numerical simulation results in MATLAB are presented for linear and nonlinear TOA localization methods, as well as their mutual correlation.
U radu se predlaže novi algoritam, ACORS-ANNDPF za WSNs (bežične senzorske mreže), u svrhu povećanja stope uporabe WSNs i produženja životnog ciklusa Iot-a (Interneta stvari). Razvijen na temelju ...algoritma kolonije mrava, ovaj se poboljšani algoritam može primijeniti na izbor optimalne putanje i prepoznavanje optimalnog čvora za usmjeravanje u slučaju gubljenja čvora usmjeravanja. Kako bi se smanjilo vrijeme utrošeno na premiještanje skupine mreža, algoritam neuronske mreže odabire pokazatelje u skladu s aktualnim aplikacijskim okruženjem i podešava ih u svrhu optimiziranja podataka skupine. Nakon toga, autor provodi nekoliko simulacijskih eksperimenata i uspoređuje predloženi algoritam s drugim algoritmima. Rezultati pokazuju da se predloženim algoritmom osigurava visoka učinkovitost energije i balansirana potrošnja energije. Prema tome, zaključeno je da se predloženim algoritmom može poboljšati brzina uporabe mreže i povećati prijenosna funkcija mreže.
U bežičnim senzorsim mrežama, uspješna komunikacija je glavni cilj protokola za kontrolu pristupa bežičnom mediju za prijenos podataka (MAC). Istovremeni prijenos je jedan od glavnih načina ...rješavanja pitanja tradicionalnih MAC protokola s malom propusnošću i akumuliranim zastojem u bežičnim senzorskim mrežama s visokim opterećenjem i intenzivnim čvorovima. U ovom se radu predlaže novi MAC protokol s istovremenim prijenosom koji koristi zahvat kanala omogućujući uspješni istovremeni prijenos da bi se osigurala učinkovita komunikacija. Koristimo algoritam kontrole snage temeljen na ne-kooperativnoj teoriji igre s nepoptpunim informacijama u svrhu postizanja istovremenog prijenosa višestruke veze na istom kanalu. Uz to, uvodi se Bayesian-Nashov poučak ekvilibrija za dobivanje dokaza o njegovom postojanju i jedinstvenosti. Rezultati simulacije pokazuju da protokol koji predlažemo može dobro funkcionirati u okruženju interferencije za istovremeni prijenos podataka. Značajno je da je poboljšan protok mreže i da su smanjeni zastoji u širenju podataka te je tako došlo i do uštede energije. Također, budući da efikasno koristimo resurse kanala, učinkovitost ponovne uporabe prostora značajno je poboljšana.
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