Thesis (MSc)--University of Stellenbosch, 2007. / ENGLISH ABSTRACT: We use Evolutionary Multi-Objective Optimisation (EMOO) algorithms to optimise objective
functions that reflect situations in communication networks. These include functions
that optimise Network Engineering (NE) objective functions in core, metro and wireless
sensor networks. The main contributions of this thesis are threefold.
Routing and Wavelength Assignment (RWA) for IP backbone networks.
Routing and Wavelength Assignment (RWA) is a problem that has been widely addressed
by the optical research community. A recent interest in this problem has been raised by the
need to achieve routing optimisation in the emerging generation multilayer networks where
data networks are layered above a Dense Wavelength Division Multiplexing (DWDM) network.
We formulate the RWA as both a single and a multi-objective optimisation problem
which are solved using a two-step solution where (1) a set of paths are found using genetic
optimisation and (2) a graph coloring approach is implemented to assign wavelengths to
these paths. The experimental results from both optimisation scenarios reveal the impact
of (1) the cost metric used which equivalently defines the fitness function (2) the algorithmic
solution adopted and (3) the topology of the network on the performance achieved by
the RWA procedure in terms of path quality and wavelength assignment.
Optimisation of Arrayed Waveguide Grating (AWG) Metro Networks.
An Arrayed Waveguide Grating (AWG) is a device that can be used as a multiplexer or
demultiplexer in WDM systems. It can also be used as a drop-and-insert element or even
a wavelength router. We take a closer look at how the hardware and software parameters
of an AWG can be fine tuned in order to maximise throughput and minimise the delay.
We adopt a multi-objective optimisation approach for multi-service AWG-based single hop metro WDM networks. Using a previously proposed multi-objective optimisation model
as a benchmark, we propose several EMOO solutions and compare their efficiency by
evaluating their impact on the performance achieved by the AWG optimisation process.
Simulation reveals that (1) different EMOO algorithms can exhibit different performance
patterns and (2) good network planning and operation solutions for a wide range of traffic
scenarios can result from a well selected EMOO algorithm.
Wireless Sensor Networks (WSNs) Topology (layout) Optimisation.
WSNs have been used in a number of application areas to achieve vital functions in situations
where humans cannot constantly be available for certain tasks such as in hostile areas
like war zones, seismic sensing where continuous inspection and detection are needed, and
many other applications such as environment monitoring, military operations and surveillance.
Research and practice have shown that there is a need to optimise the topology
(layout) of such sensors on the ground because the position on which they land may affect
the sensing efficiency. We formulate the problem of layout optimisation as a multi-objective
optimisation problem consisting of maximising both the coverage (area) and the lifetime of
the wireless sensor network. We propose different algorithmic evolutionary multi-objective
methods and compare their performance in terms of Pareto solutions. Simulations reveal
that the Pareto solutions found lead to different performance patterns and types of layouts. / AFRIKAANSE OPSOMMING: Ons gebruik ”Evolutionary Multi-Objective Optimisation (EMOO)” algoritmes om teiken
funksies, wat egte situasies in kommunikasie netwerke voorstel, te optimiseer. Hierdie sluit
funksies in wat ”Network Engineering” teiken funksies in kern, metro en wireless sensor
netwerke optimiseer. Die hoof doelwitte van hierdie tesis is dus drievuldig.
RWA vir IP backbone netwerke
”Routing and Wavelength Assignment (RWA)” is ’n probleem wat al menigte kere in
die optiese navorsings kringe aangespreek is. Belangstelling in hierdie veld het onlangs
ontstaan a.g.v. die aanvraag na die optimisering van routering in die opkomende generasie
van veelvuldige vlak netwerke waar data netwerke in ’n vlak ho¨er as ’n ”Dense Wavelength
Division Multiplexing (DWDM)” netwerk gele is. Ons formuleer die RWA as beide ’n enkele
and veelvuldige teiken optimiserings probleem wat opgelos word deur ’n 2-stap oplossing
waar (1) ’n stel roetes gevind word deur genetiese optimisering te gebruik en (2) ’n grafiek
kleuring benadering geimplementeer word om golflengtes aan hierdie roetes toe te ken.
Die eksperimentele resultate van beide optimiserings gevalle vertoon die impak van (1) die
koste on wat gebruik word wat die ekwalente fitness funksie definieer , (2) die algoritmiese
oplossing wat gebruik word en (3) die topologie van die netwerk op die werkverrigting van
die RWA prosedure i.t.v. roete kwaliteit en golflengte toekenning.
Optimisering van AWG Metro netwerk
’n ”Arrayed Waveguide Grating (AWG)” is ’n toestel wat gebruik kan word as ’n multipleksor
of demultipleksor in WDM sisteme. Dit kan ook gebruik word as ’n val-en-inplaas
element of selfs ’n golflengte router. Kennis word ingestel na hoe die hardeware en sagteware
parameters van ’n AWG ingestel kan word om die deurset tempo te maksimeer en vertragings te minimiseer. Ons neem ’n multi-teiken optimiserings benadering vir multi diens,
AWG gebaseerde, enkel skakel, metro WDM netwerke aan. Deur ’n vooraf voorgestelde
multi teiken optimiserings model as ”benchmark” te gebruik, stel ons ’n aantal EMOO
oplossings voor en vergelyk ons hul effektiwiteit deur hul impak op die werkverrigting wat
deur die AWG optimiserings proses bereik kan word, te vergelyk. Simulasie modelle wys
dat (1) verskillende EMOO algoritmes verskillende werkverrigtings patrone kan vertoon
en (2) dat goeie netwerk beplanning en werking oplossings vir ’n wye verskeidenheid van
verkeer gevalle kan plaasvind a.g.v ’n EMOO algoritme wat reg gekies word.
”Wireless Sensor Network” Topologie Optimisering
WSNs is al gebruik om belangrike funksies te verrig in ’n aantal toepassings waar menslike
beheer nie konstant beskikbaar is nie, of kan wees nie. Voorbeelde van sulke gevalle is oorlog
gebiede, seismiese metings waar aaneenlopende inspeksie en meting nodig is, omgewings
meting, militˆere operasies en bewaking. Navorsing en praktiese toepassing het getoon dat
daar ’n aanvraag na die optimisering van die topologie van sulke sensors is, gebaseer op
gronde van die feit dat die posisie waar die sensor beland, die effektiwiteit van die sensor
kan affekteer. Ons formuleer die probleem van uitleg optimisering as ’n veelvuldige
vlak optimiserings probleem wat bestaan uit die maksimering van beide die bedekkings
area en die leeftyd van die wireless sensor netwerk. Ons stel verskillende algoritmiese,
evolutionˆere, veelvuldige vlak oplossings voor en vergelyk hul werkverrigting i.t.v Pareto
oplossings. Simulasie modelle wys dat die Pareto oplossings wat gevind word lei na verskillende
werkverrigtings patrone en uitleg tipes.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/21548 |
| Date | 12 1900 |
| Creators | Baruani, Atumbe Jules |
| Contributors | Bagula, Antoine B., Stellenbosch University. Faculty of Science. Dept. of Mathematical Sciences. Institute for Applied Computer Science. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | Unknown |
| Type | Thesis |
| Format | xvi, 104 leaves : ill. |
| Rights | Stellenbosch University |
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