Thesis (MSc)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: Supply-demand analysis (SDA) is a tool that allows for the control, regulation and behaviour of metabolic pathways to be understood. In this framework, reactions are grouped into reaction blocks that represent the supply and demand of a metabolic product. The elasticities of these supply and demand blocks can be used to determine the degree of control either block has over the flux in the pathway and the degree of homoeostasis of the metabolic product that links the blocks. Rate characteristic plots, on which the rates of supply and demand blocks are plotted as functions of the concentration of the linking metabolite, represent a powerful visual tool in this framework. Generalised supply-demand analysis (GSDA) allows for the analysis of metabolic models of arbitrary size and complexity without prior knowledge of the regulatory structure of the pathway. This is achieved by performing SDA on each variable metabolite in a pathway instead of choosing a single linking metabolite. GSDA also provides other benefits over SDA as it allows for potential sites of regulation and regulatory metabolites to be identified. Additionally it allows for the identification and quantification of the relative contribution of di erent routes of regulation from an intermediate to a reaction block. Moiety-conserved cycles present a challenge in performing in silico SDA or GSDA, as the total concentration of a moiety must remain constant, thereby limiting the range of possible concentrations of the metabolites between which it cycles. The first goal of this thesis was to develop methods to perform GSDA on two-membered and interlinked moiety-conserved cycles. We showed that by expressing the members of a moiety-conserved cycle as a ratio, rather than individual metabolite concentrations, we can freely vary the ratio without breaking moiety conservation in a GSDA. Furthermore, we showed that by linking the concentrations of the members of two interlinked two-membered moiety-conserved cycles to a “linking metabolite”, we could vary the concentration of this metabolite, within constraints, without breaking moiety conservation. The Python Simulator for Cellular Systems (PySCeS) is a software package developed within our group that provides a variety of tools for the analysis of cellular systems. The RateChar module for PySCeS was previously developed as a tool to perform GSDA on kinetic models of metabolic pathways by automatically generating rate characteristic plots for each variable metabolite in a pathway. The plots generated by RateChar, however, were at times unclear when the models analysed were too complex. Additionally, invalid results where steady-states could not be reached were not filtered out, and therefore appeared together with valid results on the rate characteristic plots generated by RateChar. We therefore set out to improve upon RateChar by building plotting interface that produces clear and error-free rate characteristics. The resulting RCFigure class allows users to interactively change the composition of a rate characteristic plot and it includes automatic error checking. It also provides clearer rate characteristics with e ective use of colour. Using these tools two case studies were undertaken. In the first, GSDA was used to investigate the regulation of aspartate-derived amino acid synthesis in Arabidopsis thaliana. A central result was that the direct interaction of aspartate-semialdehyde (ASA), a metabolite at a branch point in the pathway, with the enzyme that produces it only accounts for 7% of the total response in the flux of supply. Instead, 89% of the observed flux response was due to ASA interacting with of the downstream enzymes for which it is a substrate. This result was unexpected as the ASA producing enzyme had a high elasticity towards ASA. In a second case study moiety-conserved cycles in a model of the pyruvate branches in lactic acid bacteria were linearised using the above mentioned method. This served to illustrate how multiple reaction blocks are connected by these conserved moieties. By performing GSDA on this model, we demonstrated that the interactions of these conserved moieties with the various reaction blocks in the pathway, led to non-monotonic behaviour of the rate characteristics of the supply and demand for the moiety ratios. An example of this is that flux would increase in response to an increase in product for certain ranges. This thesis illustrates the power of GSDA as an entry point in studying metabolic pathways, as it can potentially reveal properties of the regulation and behaviour of metabolic pathways that were not previously known, even if these pathways were subjected to previous analysis and a kinetic model is available. In general it also demonstrates how e ective analysis tools and metabolic models are vital for the study of metabolism. / AFRIKAANSE OPSOMMING: Vraag-en-aanbod analise (VAA) is ’n analisemetode wat mens in staat stel om die beheer, regulering en gedrag van metaboliese paaie beter te verstaan. In hierdie raamwerk word reaksies gegroepeer as reaksieblokke wat die aanbod (produksiestappe) en die aanvraag (verbruik-stappe) van ’n metaboliese produk verteenwoordig. Vanaf die elastisiteite van hierdie aanbod- en aanvraag-blokke kan die graad van beheer van elkeen van die blokke oor die fluksie, asook die graad van homeostase van die metaboliese koppelingsintermediaat, bereken word. Snelheidskenmerk-grafieke, waarop die snelhede van die vraag- en aanbod-blokke as funksies van die konsentrasie van die koppelingsmetaboliet uiteengesit word, verteenwoordig ’n kragtige visuele hulpmiddel in hierdie raamwerk. Veralgemeende vraag-aanbod analise (VVAA), die veralgemeende vorm van VAA, maak dit moontlikommetaboliese modelle van arbitrêre grootte en kompleksiteit te analiseer sonder enige vooraf-kennis van die regulatoriese struktuur van die paaie. Die prosedure is om VAA op elk van die veranderlike metaboliete in die pad uit te voer, eerder as om ’n enkele koppelingsmetaboliet te kies. VVAA het ook ander voordele bo VAA aangesien dit potensiële setels van regulering en regulatoriese metaboliete kan identifiseer. Daarbenewens kan dit die relatiewe bydrae van verskillende regulerings-roetes van vanaf ’n intermediaat na ’n reaksieblok identifiseer en hulle kwantifiseer. Groep-gekonserveerde siklusse bied ’n uitdaging vir in silico VAA of VVAA, aangesien die totale konsentrasie van die gekonserveerde groep konstant moet bly. Dit beperk die waardes van moontlike konsentrasies van die metaboliete wat die siklus uitmaak. Die eerste doelstelling van hierdie tesis was dus om metodes te ontwikkel waarmee VVAA op tweeledige en saamgebonde groep-gekonserveerde siklusse uitgevoer kan word. Deur die lede van groep-gekonserveerde siklusse eerder as verhoudings uit te druk in plaas van as individuele metabolietkonsentrasies, het ons gewys dat ons hierdie verhouding vrylik kan varieer sonder om die groep-konservering te breek in ’n VVAA. Ons het ook gewys dat die konsentrasies van die lede van ’n saamgebonde groep-gekonserveerde siklus gekoppel kan word aan ’n “koppelingsmetaboliet”, waarvan die konsentrasie dan binne perke gevarieer kan word sonder om die groep-konservering te breek. Die “Python Simulator for Cellular Systems” (PySCeS) is ’n programmatuur-pakket wat binne ons navorsingsgroep ontwikkel is met die doel om sellulêre sisteme numeries te analiseer. Die RateChar module vir PySCeS was reeds voor die aanvang van hierdie projek ontwikkel om VVAAop kinetiese modelle van metaboliese paaie uit te voer deur outomaties snelheidskenmerke vir elke veranderlikke metaboliet te genereer. Die grafieke wat deur RateChar gegenereer is, was egter soms onduidelik wanneer die modelle te groot of kompleks geraak het. Daarbenewens is ongeldige resultate, waar ’n bestendige toestand nie bereik kon word nie, nie uitgefiltreer nie, en het dus saam met geldige resultate op die snelheidskenmerke verskyn. Een van die doelstellings was dus om RateChar te verbeter deur ’n koppelvlak vir grafieke te ontwikkel wat duidelike en foutlose snelheidskenmerke kon produseer. Dit het gelei tot die RCFigure klas wat outomatiese foutopsporing uitvoer en gebruikers in staat stel om op ’n interaktiewe wyse die samestelling van ’n snelheidskenmerkgrafiek te verander. Dit bied ook duideliker snelheidskenmerke deur e ektief van kleur gebruik te maak. Met hierdie ontwikkelde gereedskap is twee gevallestudies onderneem. In die eerste is VVAA gebruik om die regulering van aspartaat-afgeleide aminosuursintese in Arabidopsis thaliana te bestudeer. Die belangrikste resultaat was dat die direkte interaksie van aspartaat-semialdehied (ASA), ’n metaboliet by ’n vertakkingspunt in die pad, met die ensiem wat dit produseer, slegs vir 7% van die totale respons in die aanbod-fluksie verantwoordelik was. Daarteen was 89% van die waargenome fluksierespons die gevolg van die interaksie van ASA met drie van die stroomafensieme, waarvoor dit ’n substraat is. Hierdie resultaat was onverwag aangesien die ensiem wat ASA produseer ’n hoë elastisiteit teenoor ASA toon. In ’n tweede gevallestudie is die groep-gekonserveerde siklusse in ’n model van die pirovaat-takke in melksuurbakterie-metabolisme gelineariseer deur gebruik te maak van die bo beskrewe metode. Dit illustreer hoe verskeie reaksieblokke verbind word deur hierdie gekonserveerde groepe. M.b.v. ’n VVAA van hierdie model het ons gedemonstreer dat die interaksies van die gekonserveerde groepe met die verskeie reaksieblokke in die pad kan lei tot nie-monotoniese gedrag van die snelheidskenmerke van die vraag- en aanbod-reaksies vir die verhouding van die gekonserveerde groep-komponente. ’n Voorbeeld hiervan is die onverwagte waarneming dat die fluksie toeneem met toenemende produk-konsentrasie oor sekere gebiede. Hierdie tesis illustreer die krag van VVAA as ’n beginpunt vir die studie van metaboliese paaie, aangesien dit onbekende regulatoriese eienskappe en gedragspatrone kan ontbloot, selfs al is die paaie vantevore m.b.v. kinetiese modelle geanaliseer. Oor die algemeen demonstreer dit die noodsaaklikheid van e ektiewe analisegereedskap en metaboliese modelle vir die bestudering van metabolisme. / National Research Foundation

Στην παρούσα εργασία παρουσιάζεται και αναλύεται διεξοδικά ο μηχανισμός μεταπομπής (handover) σε συστήματα κινητής επικοινωνίας. Οι μέθοδοι μεταπομπής βρίσκουν σημαντική εφαρμογή στα κυψελωτά συστήματα (cellular systems) και κατηγοριοποιούνται με βάση διάφορα χαρακτηριστικά τους, σε handovers σε σκληρά ή μαλακά, οριζόντια ή κάθετα, ελεγχόμενα από το Δίκτυο ή από την κινητή συσκευή, ή υποβοηθούμενα από την κινητή συσκευή. Σημαντικό ρόλο στις διαδικασίες handover παίζουν οι αλγόριθμοι απόφασης. Βασικές κατηγορίες αλγορίθμων απόφασης handover είναι αυτοί που στηρίζονται στη στάθμη της λαμβανόμενης ισχύος του σήματος, οι αλγόριθμοι που στηρίζονται σε fuzzy logic και οι αλγόριθμοι προτεραιότητας. Στην παρούσα εργασία προσομοιάζεται ένας αλγόριθμος προτεραιότητας γνωστός ως SJ-scheme με χρήση του λογισμικού Matlab και ειδικότερα των υποσυστημάτων του Simulink και Stateflow. Το προταθέν μοντέλο αποτελείται από έξι βασικά επιμέρους υποσυστήματα: το Υποσύστημα Εισόδου (Input Subsystem), το Υποσύστημα Καθορισμού της Χωρητικότητας των Καναλιών (Channels Size Subsystem), το Υποσύστημα Μνήμης (Memory Subsystem), το Υποσύστημα Ολοκλήρωσης Κλήσεων (Call Completion Subsystem), το Υποσύστημα των Αποτελεσμάτων (Scope Subsystem) και το Υποσύστημα Handover (Handover Subsystem) που αποτελεί την «καρδιά» του μοντέλου και περιλαμβάνει δύο βασικά blocks, ένα το οποίο υλοποιεί τη διαδικασία διαχείρισης νέων κλήσεων (New_calls_process) και ένα που υλοποιεί τη διαδικασία διαχείρισης των handovers (Handover_process). Πέραν της δημιουργίας μοντέλου προσομοίωσης, στην παρούσα εργασία παρουσιάζονται αναλυτικά και σχολιάζονται τα αποτελέσματα εκτέλεσης της προσομοίωσης και τα μετρούμενα μεγέθη. Μέσα από τις γραφικές αναπαραστάσεις που παράγονται και εξετάζονται, γίνεται αντιληπτός ο τρόπος λειτουργίας και οι ιδιαιτερότητες του προτεινόμενου μοντέλου. / In the current study the mechanism of switching between cells (handover) in mobile communication systems is presented and analyzed in detail. The handover methods are mainly applied in cellular systems and categorized according to various characteristics in hard or soft handovers, horizontal or vertical handovers, and handovers controlled by the network or the mobile device, or assisted by the mobile device. Handover decision algorithms play important role in the described processes. Main categories of handover decision algorithms are those based on the received signal strength, fuzzy logic and priority. In this study, a priority algorithm known as SJ-scheme is simulated, using Matlab software and, in particular subsystems Simulink and Stateflow. The proposed model consists of six major subsystems: Input Subsystem, Channels Size Subsystem, Memory Subsystem, Call Completion Subsystem, Scope Subsystem and Handover Subsystem which is the "heart" of the model and includes two main blocks, one that implements the new call management process and one that implements the procedure for managing handovers. Besides creating a simulation model, in this work results of running the simulation and measured data are presented and discussed. Matlab plots and graphical representations produced are examined to make clear the way that the proposed model works.

A evolução dos sistemas de comunicação sem fio ou wireless apresentam até agora três gerações em menos de duas décadas. Fazendo parte desta evolução estão os sistemas de telefonia celular e os emergentes Sistemas de Comunicação Pessoal ou PCS (Personal Communications Systems). Este trabalho visa apresentar duas questões importantes na evolução destes sistemas, primeiro a questão da segurança e segundo a questão da interconexão com redes heterogêneas. No trabalho, abordando a questão de segurança, são estudados, analisados e comparados os mecanismos de autenticação e privacidade implementados nos atuais padrões de telefonia celular digital e analógico, como sistemas AMPS (celular analógico americano), USCD (celular digital americano) e GSM (celular digital europeu). São identificadas a vulnerabilidade e os fraudes mais comuns nestes sistemas. Também são analisados as propostas das recentes pesquisas e o state of art em termos de segurança, para os sistemas PCS emergentes. Como conclusão apresentado um quadro comparativo resumindo as principais características de segurança adotados pelos sistemas abordados neste estudo. Uma vez apresentado os aspectos de segurança em forma isolada para cada um dos sistemas acima mencionados, é apresentado a questão segurança no contexto da interconexão com redes heterogêneas. A interconexão com redes heterogêneas é outro problema a ser resolvido na implementação da terceira geração de sistemas wireless, para fornecer o roaming automático e a mobilidade pessoal e de terminal. Neste trabalho são revisados os protocolos de sinalização SS7 (Signaling System Number 7) e MAP (Mobile Application Part), como requisitos importantes na solução da interconexão e interoperabilidade entre as redes fixas atuais com as futuras redes móveis. Como conclusão deste estudo é apresentado a proposta de uma arquitetura de protocolos de sinalização, representando a interconexão de um sistema PCS baseado no padrão J-STD-007, com a rede de telefonia celular IS-95. Esta interconexão é realizada através de uma interface de rede denominada IIF (Interworking and Interoperability Function) usando protocolos de sinalização por canal comum SS7 e MAP. Finalmente são apresentados as conclusões quanto aos objetivos alcançados, e é proposto um trabalho futuro, tomando como base o desenvolvido neste trabalho. / The evolution of wireless communications systems has developed into the third generation which is mainly represented by the Telephone Cellular Systems and PCS (Personal Communication systems). This work presents an overview about two importante issues in the evolution of the Wireless Communication Systems: Security and Interworking. Initially we carry out our study on the wireless communication security issue by analyzing and comparing some major authentication features and privacy characteristics implemented in the currently standardized cellular phone systems such as AMPS (American Analog Cellular), USCD (American Digital Cellular) and GSM (Euroupean Digital Cellular). For this end. we tentatively determine how vulnerable to the fraudulent attacks these systems are and what are those frauds commonly occurring in these systems. Also we analyze the state of art and some proposals for security problems in PCS systems found in the literature. We conclude our preliminary study with a table summarizing some principal systems' characteristics in the security issue. Next, we extend our discussion to the case of heterogeneous networks. In fact, the interconnection of heterogeneous networks is another important issue that needs to be deeply investigated in order to develop a rebust third generation of wireless communication systems, special those capable of providing automatic "roaming" and personal as well as terminal mobility. In this work we particularly discuss the protocols employed in the signaling system SS7 ( Signaling Systems Number 7) and MAP ( Mobile Application Part) which are important issues in terms of the interworking and interoperability of wireless and wireline networks. As a conclusion of this discussion, we propose a protocol architecture based on the RM-OSI model relating to the interconnection of a PCS system, J-STD-007, with the IS-95 cellular phone networks. Note that the proposed model uses the signaling systems SS7 and MAP. Finally we present some importante conclusion with respect to the objetives achieved in this work, and propose some future research activities based on this work.

A evolução dos sistemas de comunicação sem fio ou wireless apresentam até agora três gerações em menos de duas décadas. Fazendo parte desta evolução estão os sistemas de telefonia celular e os emergentes Sistemas de Comunicação Pessoal ou PCS (Personal Communications Systems). Este trabalho visa apresentar duas questões importantes na evolução destes sistemas, primeiro a questão da segurança e segundo a questão da interconexão com redes heterogêneas. No trabalho, abordando a questão de segurança, são estudados, analisados e comparados os mecanismos de autenticação e privacidade implementados nos atuais padrões de telefonia celular digital e analógico, como sistemas AMPS (celular analógico americano), USCD (celular digital americano) e GSM (celular digital europeu). São identificadas a vulnerabilidade e os fraudes mais comuns nestes sistemas. Também são analisados as propostas das recentes pesquisas e o state of art em termos de segurança, para os sistemas PCS emergentes. Como conclusão apresentado um quadro comparativo resumindo as principais características de segurança adotados pelos sistemas abordados neste estudo. Uma vez apresentado os aspectos de segurança em forma isolada para cada um dos sistemas acima mencionados, é apresentado a questão segurança no contexto da interconexão com redes heterogêneas. A interconexão com redes heterogêneas é outro problema a ser resolvido na implementação da terceira geração de sistemas wireless, para fornecer o roaming automático e a mobilidade pessoal e de terminal. Neste trabalho são revisados os protocolos de sinalização SS7 (Signaling System Number 7) e MAP (Mobile Application Part), como requisitos importantes na solução da interconexão e interoperabilidade entre as redes fixas atuais com as futuras redes móveis. Como conclusão deste estudo é apresentado a proposta de uma arquitetura de protocolos de sinalização, representando a interconexão de um sistema PCS baseado no padrão J-STD-007, com a rede de telefonia celular IS-95. Esta interconexão é realizada através de uma interface de rede denominada IIF (Interworking and Interoperability Function) usando protocolos de sinalização por canal comum SS7 e MAP. Finalmente são apresentados as conclusões quanto aos objetivos alcançados, e é proposto um trabalho futuro, tomando como base o desenvolvido neste trabalho. / The evolution of wireless communications systems has developed into the third generation which is mainly represented by the Telephone Cellular Systems and PCS (Personal Communication systems). This work presents an overview about two importante issues in the evolution of the Wireless Communication Systems: Security and Interworking. Initially we carry out our study on the wireless communication security issue by analyzing and comparing some major authentication features and privacy characteristics implemented in the currently standardized cellular phone systems such as AMPS (American Analog Cellular), USCD (American Digital Cellular) and GSM (Euroupean Digital Cellular). For this end. we tentatively determine how vulnerable to the fraudulent attacks these systems are and what are those frauds commonly occurring in these systems. Also we analyze the state of art and some proposals for security problems in PCS systems found in the literature. We conclude our preliminary study with a table summarizing some principal systems' characteristics in the security issue. Next, we extend our discussion to the case of heterogeneous networks. In fact, the interconnection of heterogeneous networks is another important issue that needs to be deeply investigated in order to develop a rebust third generation of wireless communication systems, special those capable of providing automatic "roaming" and personal as well as terminal mobility. In this work we particularly discuss the protocols employed in the signaling system SS7 ( Signaling Systems Number 7) and MAP ( Mobile Application Part) which are important issues in terms of the interworking and interoperability of wireless and wireline networks. As a conclusion of this discussion, we propose a protocol architecture based on the RM-OSI model relating to the interconnection of a PCS system, J-STD-007, with the IS-95 cellular phone networks. Note that the proposed model uses the signaling systems SS7 and MAP. Finally we present some importante conclusion with respect to the objetives achieved in this work, and propose some future research activities based on this work.

A evolução dos sistemas de comunicação sem fio ou wireless apresentam até agora três gerações em menos de duas décadas. Fazendo parte desta evolução estão os sistemas de telefonia celular e os emergentes Sistemas de Comunicação Pessoal ou PCS (Personal Communications Systems). Este trabalho visa apresentar duas questões importantes na evolução destes sistemas, primeiro a questão da segurança e segundo a questão da interconexão com redes heterogêneas. No trabalho, abordando a questão de segurança, são estudados, analisados e comparados os mecanismos de autenticação e privacidade implementados nos atuais padrões de telefonia celular digital e analógico, como sistemas AMPS (celular analógico americano), USCD (celular digital americano) e GSM (celular digital europeu). São identificadas a vulnerabilidade e os fraudes mais comuns nestes sistemas. Também são analisados as propostas das recentes pesquisas e o state of art em termos de segurança, para os sistemas PCS emergentes. Como conclusão apresentado um quadro comparativo resumindo as principais características de segurança adotados pelos sistemas abordados neste estudo. Uma vez apresentado os aspectos de segurança em forma isolada para cada um dos sistemas acima mencionados, é apresentado a questão segurança no contexto da interconexão com redes heterogêneas. A interconexão com redes heterogêneas é outro problema a ser resolvido na implementação da terceira geração de sistemas wireless, para fornecer o roaming automático e a mobilidade pessoal e de terminal. Neste trabalho são revisados os protocolos de sinalização SS7 (Signaling System Number 7) e MAP (Mobile Application Part), como requisitos importantes na solução da interconexão e interoperabilidade entre as redes fixas atuais com as futuras redes móveis. Como conclusão deste estudo é apresentado a proposta de uma arquitetura de protocolos de sinalização, representando a interconexão de um sistema PCS baseado no padrão J-STD-007, com a rede de telefonia celular IS-95. Esta interconexão é realizada através de uma interface de rede denominada IIF (Interworking and Interoperability Function) usando protocolos de sinalização por canal comum SS7 e MAP. Finalmente são apresentados as conclusões quanto aos objetivos alcançados, e é proposto um trabalho futuro, tomando como base o desenvolvido neste trabalho. / The evolution of wireless communications systems has developed into the third generation which is mainly represented by the Telephone Cellular Systems and PCS (Personal Communication systems). This work presents an overview about two importante issues in the evolution of the Wireless Communication Systems: Security and Interworking. Initially we carry out our study on the wireless communication security issue by analyzing and comparing some major authentication features and privacy characteristics implemented in the currently standardized cellular phone systems such as AMPS (American Analog Cellular), USCD (American Digital Cellular) and GSM (Euroupean Digital Cellular). For this end. we tentatively determine how vulnerable to the fraudulent attacks these systems are and what are those frauds commonly occurring in these systems. Also we analyze the state of art and some proposals for security problems in PCS systems found in the literature. We conclude our preliminary study with a table summarizing some principal systems' characteristics in the security issue. Next, we extend our discussion to the case of heterogeneous networks. In fact, the interconnection of heterogeneous networks is another important issue that needs to be deeply investigated in order to develop a rebust third generation of wireless communication systems, special those capable of providing automatic "roaming" and personal as well as terminal mobility. In this work we particularly discuss the protocols employed in the signaling system SS7 ( Signaling Systems Number 7) and MAP ( Mobile Application Part) which are important issues in terms of the interworking and interoperability of wireless and wireline networks. As a conclusion of this discussion, we propose a protocol architecture based on the RM-OSI model relating to the interconnection of a PCS system, J-STD-007, with the IS-95 cellular phone networks. Note that the proposed model uses the signaling systems SS7 and MAP. Finally we present some importante conclusion with respect to the objetives achieved in this work, and propose some future research activities based on this work.

Abstract Radio resource management techniques for broadband wireless systems beyond the existing cellular systems are developed while considering their special characteristics such as multi-carrier techniques, adaptive radio links and multiple-input multiple-output (MIMO) antenna techniques. Special focus is put on the design of linear transmission strategies in a cooperative cellular system where signal processing can be performed in a centralised manner across distributed base station (BS) antenna heads. A time-division duplex cellular system based on orthogonal frequency division multiplexing (OFDM) with adaptive MIMO transmission is considered in the case where the received signals are corrupted by non-reciprocal inter-cell interference. A bandwidth efficient closed-loop compensation algorithm combined with interference suppression at the receiver is proposed to compensate for the interference and to guarantee the desired Quality of Service (QoS) when the interference structure is known solely at the receiver. A greedy beam ordering and selection algorithm is proposed to maximise the sum rate of a multiuser MIMO downlink (DL) with a block zero forcing (ZF) transmission. The performance of the block-ZF transmission combined with the greedy scheduling is shown to approach the sum capacity as the number of users increases. The maximum sum rate is often found to be achieved by transmitting to a smaller number of users or beams than the spatial dimensions allow. In addition, a low complexity algorithm for joint user, bit and power allocation with a low signalling overhead is proposed. Different linear transmission schemes, including the ZF as a special case, are developed for the scenario where the cooperative processing of the transmitted signal is applied to users located within a soft handover (SHO) region. The considered optimisation criteria include minimum power beamformer design; balancing the weighted signal-to-interference-plus-noise ratio (SINR) values per data stream; weighted sum rate maximisation; and balancing the weighted rate per user with additional QoS constraints such as guaranteed bit rate per user. The method can accommodate supplementary constraints, e.g., per antenna or per BS power constraints, and upper/lower bounds for the SINR values of the data streams. The proposed iterative algorithms are shown to provide powerful solutions for difficult non-convex transceiver optimisation problems. System level evaluation is performed in order to assess the impact of a realistic multi-cell environment on the performance of a cellular MIMO-OFDM system. The users located in the SHO region are shown to benefit from greatly increased transmission rates. Consequently, significant overall system level gains result from cooperative SHO processing. The proposed SHO scheme can be used for providing a more evenly distributed service over the entire cellular network.

[pt] O problema de localização de estações móveis pessoais em sistemas celulares de comunicações vem recebendo grande atenção nos últimos anos, tanto por questões ligadas à segurança como por suas amplas aplicações comerciais no desenvolvimento de novos serviços e aplicações. Nesta dissertação foi desenvolvido um ambiente de simulação de localização de estações móveis em ambiente micro celulares empregando um programa de traçado de raios pelo método da força bruta (lançamento de raios), já disponível, para estimar os comprimentos de percursos e tempos de chegada entre diversas estações rádio base e a estação móvel em cenários urbanos modelados por sólidos multifacetados. Os perfis de retardo gerados por este programa são usados como dados de entrada para um programa desenvolvido nesta dissertação que estima a localização dos móveis utilizando os métodos de Taylor e de Chan. O processo desenvolvido foi testado em ambientes de geometria simples fornecendo resultados bastante consistentes e mostrando que a técnica de traçado de raios é uma ferramenta útil para a simulação e desenvolvimento de algoritmos de localização, cujo teste em situações reais exige grande volume de medidas de alta complexidade cujos exemplos na literatura técnica são escassos. Com base nas simulações foi investigadas a influência do número de estações rádio base na precisão das estimativas de localização e realizada uma comparação do desempenho dos métodos em situações com visibilidade (LOS) e sem visibilidade (NLOS). Foi analisado ainda o efeito da altura das estações na precisão dos resultados de localização. / [en] The location of mobile terminals in mobile cellular systems has been receiving increasing attention in the last few years. This interest in focused not only in security aspects but also in the development of new services for commercial application. In this Dissertation a simulation environment for mobile stations location in microcellular systems was developed. The simulation tools include a ray tracing software, previously implemented using the ray launching technique, to estimate the path lengths and time of arrival of signals from the mobile station to several radio base stations, and new software implementing terminal location methods using the Taylor linearization and the Chan methods. The simulation tools were tested in scenarios of simple geometry producing consistent results and showing that ray tracing can be a useful tool for simulation and development of location algorithms. The simulations allowed the investigation of location precision dependence on the number of radio bases employed and the evaluation of the estimation methods in visibility (LOS) and non- visibility (NLOS) conditions. The influence of base station antennas heights was also investigated.

This thesis deals with the problem of estimating the velocity of a mobile station (MS)in a mobile communication system using the instantaneous frequency (IF) of the received signal at the MS antenna. This estimate is essential for satisfactory handover performance, effective dynamic channel assignment, and optimisation of adaptive multiple access wireless receivers. Conventional methods for estimating the MS velocity are based either on the statistics of the envelope or quadrature components of the received signal. In chapter 4 of the thesis, we show that their performance deteriorates in the presence of shadowing. Other velocity estimators have also been proposed which require prior estimation of the channel or the average received power. These are generally difficult to obtain due to the non-stationary nature of the received signal. An appropriate window which depends on the unknown MS velocity must first be applied in order to accurately estimate the required quantities. Using the statistics of the IF of the received signal at the MS antenna given in chapter 3, new velocity estimators are proposed in chapter 4 of this thesis. The proposed estimators are based on the moments, zero-crossing rate, and covariance of the received IF. Since the IF of the received signal is not affected by any amplitude distortion, the proposed IF-based estimators are robust to shadowing and propagation path-loss. The estimators for the MS velocity in a macro- and micro-cellular system are presented separately. A macro-cell system can be considered as a special case of a micro-cell in which there is no line-of-sight component at the receiver antenna. It follows that those estimators which are derived for micro-cells can be used in a macro-cell as well. In chapter 4, we analyse the performance of the proposed velocity estimators in the presence of additive noise, non-isotropic scattering, and shadowing. We also prove analytically that the proposed velocity estimators outperform the existing methods in the presence of shadowing and additive noise. The proposed IF-based estimators need prior estimation of both the IF of the received signal and Ricean K-factor. The IF estimation in a typical wireless environment, can be considered as a special case of a general problem of IF estimation in the presence of multiplicative and additive noise. In chapter 5, we show that current time-frequency approaches to this problem which are based on the peak of a time-frequency distribution (TFD) of the signal, fail because of the special shape of the power spectral density of the multiplicative noise in a wireless environment. To overcome this drawback, the use of the first-order moment of a TFD is studied in chapter 5. Theoretical analysis and simulations show that the IF estimator based on the first-order moment of a TFD exhibits negligible bias when the signal-to-additive noise ratio is more than 10 dB. The Ricean K-factor is not only necessary for velocity estimation in micro-cells, but also is a measure of the severity of fading and a good indicator of the channel quality. Two new methods for estimating the Ricean K-factor based on the first two moments of the envelope of the received signal, are proposed in chapter 6. Performance analysis presented in chapter 6, prove that the proposed K estimators are robust to non-isotropic scattering. Theoretical analysis and simulations which are presented in chapters 4 and 7 of this thesis, prove that the proposed velocity and K estimators outperform existing estimators in the presence of shadowing and additive noise.

Předkládaná disertační práce je zaměřena na „Výzkum spolehlivé komunikace pro IoT aplikace v bezdrátových sítích využívajících technologie Multi-RAT LPWAN“. Navzdory značnému pokroku v oblasti vývoje LPWA technologií umožňující masivní komunikace mezi zařízeními (mMTC), nemusí tyto technologie výkonnostně dostačovat pro nově vznikající aplikace internetu věcí. Hlavním cílem této disertační práce je proto nalezení a vyhodnocení limitů současných LPWA technologií. Na základě těchto dat jsou nevrženy nové mechanismy umožňující snazší plánování a vyhodnocování síťového pokrytí. Navržené nástroje jsou vyladěny a validovány s využitím dat získaných z rozsáhlých měřících kampaních provedených v zákaznických LPWA sítích. Tato disertační práce dále obsahuje návrh LPWA zařízení vybavených více komunikačními rozhraními (multi-RAT) které mohou umožnit překonání výkonnostních limitů jednotlivých LPWA technologií. Současná implementace se zaměřuje zejména na snížení spotřeby zařízení s více rádiovými rozhraními, což je jejich největší nevýhodou. K tomuto účelu je využito algoritmů strojového učení, které jsou schopné dynamicky vybírat nejvhodnější rozhraní k přenosu.

Předkládaná disertační práce je zaměřena na "heterogenní propojení mobilních zařízení v bezdrátových systémech 5. generace". Navzdory nepochybnému pokroku v rámci navržených komunikačních řešení postrádají mobilní sítě nastupující generace dostatečnou šířku pásma a to hlavně kvůli neefektivnímu využívání rádiového spektra. Tato situace tedy v současné době představuje řadu otázek v oblasti výzkumu. Hlavním cílem této disertační práce je proto návrh nových komunikačních mechanismů pro komunikaci mezi zařízeními v bezprostřední blízkosti s asistencí mobilní sítě a dále pak návrh a implementace algoritmů pro dynamické přidělování frekvenčního spektra v nastupujících mobilních sítích 5G. Navrhnuté komunikační mechanismy a algoritmy jsou následně komplexně vyhodnoceny pomocí nově vyvinutých simulačních nástrojů (kalibrovaných s využitím 3GPP trénovacích dat) a zejména pak v experimentální mobilní síti LTE-A, která se nachází v prostorách Vysokého učení technického v Brně, Česká Republika. Získané praktické výsledky, které jsou podpořeny zcela novou matematickou analýzou ve speciálně navržených charakteristických scénářích, představují řešení pro vlastníka spektra v případě požadavků na jeho dynamické sdílení. Tato metoda tedy představuje možnost pro efektivnější využití spektra v rámci mobilních sítí 5G bez degradace kvality služeb (QoS) a kvality zážitků (QoE) pro koncové uživatele. Vědecký přínos dosažených výsledků dokazuje fakt, že některé z principů představených v této disertační práci byly zahrnuty do celosvětově uznávaného standardu (specifikace) 3GPP Release 12.