Efficient utilization of the limited wireless spectrum while satisfying applications’ quality of service requirements is an essential design goal of forthcoming wireless networks and a key to their successful deployment. The need for spectrally efficient systems has motivated the development of adaptive transmission techniques. Enabling this adaptation requires protocols for information exchange as well as mathematical tools to optimize the controllable parameters. In this dissertation, we provide insights into such protocols and mathematical tools that target efficient utilization of the wireless spectrum. First, we propose a distributed CDMA-based medium access protocol for mobile ad hoc networks (MANETs). Our approach accounts for multiple access interference at the protocol level, thereby addressing the notorious near-far problem that undermines the throughput performance in MANETs. Second, we present a novel power-controlled MAC protocol, called POWMAC, which enjoys the same single-channel, single-transceiver design of the IEEE 802.11 Ad Hoc MAC protocol, but which achieves a significant throughput improvement over the 802.11 protocol. Third, we consider joint power/rate optimization in the context of orthogonal modulation (OM) and investigate the performance gains achieved through adaptation of the OM order using recently developed optimization techniques. We show that such adaptation can significantly increase network throughput while simultaneously reducing the per-bit energy consumption relative to fixed-order modulation systems. Finally, we determine the maximum achievable “performance” of a wireless CDMA network that employs a conventional matched filter receiver and that operates under optimal link-layer adaptation where each user individually achieves the Shannon capacity. The derived bounds serve as benchmarks against which adaptive CDMA systems can be compared.

No description available.

The research reported in this thesis investigates the performance of the transport layer Stream Control Transfer Protocol (SCTP) for streaming video over CDMA2000 cellphone and data wireless networks. The main measure of performance was quality of the received video at a given buffer size, as cellphones have memory of limited capacity. The hypothesis was that SCTP would be able to improve the quality of streamed video over UDP under the same memory requirements. Our study involved two series of simulation experiments and measurements in a testbed on the Telecom NZ CDMA2000 network, to test the performance of video streaming under SCTP and under UDP. It was found that SCTP did not improve the quality in streamed video with up to 5 second buffers. While other scenarios that have been tested by other people with high packet loss or congestion have shown that SCTP can improve the quality, the CDMA2000 network does not suffer from the impairments that SCTP could neutralise, and because of that, in this scenario, the quality of video streaming under SCTP and UDP are similar. The complexity that SCTP adds does not correspond to an increase in quality.

Les densités d'intégration actuelles des circuits intégrés permettent de disposer de SoC (systèmes sur puce) de plus en plus complexes, intégrant de plus en plus de standards. Par conséquent, le problème des interconnexions entre tous les blocs IP (Intellectual Property) constituant le SoC devient un point critique que les structures de communications actuelles ne parviennent plus à solutionner.<br />Ces problèmes sont notamment liés aux besoins de plus en plus forts en mobilité et en débit dans les architectures de communication actuelles et futures. Ainsi, les solutions à base de NoC (Network on Chip) offrent de bonnes perspectives en terme de bande passante et de flexibilité pour pallier notamment aux limites actuelles des topologies bus. Les travaux de thèse présentés ici portent sur la méthodologie de modélisation et d'exploration d'architectures de réseaux sur puce appliquée aux télécommunications.<br />Le contexte radio-télécommunications étudié est celui proposé dans le cadre du projet Européen 4MORE pour lequel nous avons contribué. Une des contraintes de ce projet était d'intégrer dans un SoC la technique MC-CDMA (Multiple Carrier Code Division Multiple Access) combinant la technique MIMO en utilisant un média de communication innovant.<br />Ainsi, nous avons contribué à cette intégration en proposant une méthodologie de conception permettant d'aider le concepteur dans le choix des différents paramètres caractérisant le NoC pour satisfaire les contraintes temps réel de l'application spécifiées dans le cahier des charges.<br />Ces travaux de thèse ont porté sur la modélisation et l'interconnexion des composants IP constituant la chaîne algorithmique du projet 4MORE afin de les intégrer dans un modèle SystemC du NoC. Par ailleurs, les choix de dimensionnement du réseau et des contraintes de placement des blocs IP sur celui-ci ont un impact important sur les performances globales de l'application. Nous avons mis en place un outil AAA (Adéquation Algorithme Architecture) permettant de réaliser l'adéquation des contraintes de l'application sur l'architecture en minimisant les chemins de communication tout en veillant à ne pas violer les bandes passantes théoriques des liens de communication entre routeurs.<br />Le flot de conception mis en œuvre permet au concepteur de générer le modèle SystemC du NoC et permettra à cours terme de générer le code VHDL associé du modèle SystemC simulé afin d'accélérer les phases de simulation et de donner la possibilité de valider logiciellement et matériellement (cible FPGA) l'architecture avec son application.

No description available.

Multicarrier code division multiple access (MC-CDMA) is a very promising candidate for the multiple access scheme in fourth generation wireless communi- cation systems. During asynchronous transmission, multiple access interference (MAI) is a major challenge for MC-CDMA systems and significantly affects their performance. The main objectives of this thesis are to analyze the MAI in asyn- chronous MC-CDMA, and to develop robust techniques to reduce the MAI effect. Focus is first on the statistical analysis of MAI in asynchronous MC-CDMA. A new statistical model of MAI is developed. In the new model, the derivation of MAI can be applied to different distributions of timing offset, and the MAI power is modelled as a Gamma distributed random variable. By applying the new statistical model of MAI, a new computer simulation model is proposed. This model is based on the modelling of a multiuser system as a single user system followed by an additive noise component representing the MAI, which enables the new simulation model to significantly reduce the computation load during computer simulations. MAI reduction using slow frequency hopping (SFH) technique is the topic of the second part of the thesis. Two subsystems are considered. The first sub- system involves subcarrier frequency hopping as a group, which is referred to as GSFH/MC-CDMA. In the second subsystem, the condition of group hopping is dropped, resulting in a more general system, namely individual subcarrier frequency hopping MC-CDMA (ISFH/MC-CDMA). This research found that with the introduction of SFH, both of GSFH/MC-CDMA and ISFH/MC-CDMA sys- tems generate less MAI power than the basic MC-CDMA system during asyn- chronous transmission. Because of this, both SFH systems are shown to outper- form MC-CDMA in terms of BER. This improvement, however, is at the expense of spectral widening. In the third part of this thesis, base station polarization diversity, as another MAI reduction technique, is introduced to asynchronous MC-CDMA. The com- bined system is referred to as Pol/MC-CDMA. In this part a new optimum com- bining technique namely maximal signal-to-MAI ratio combining (MSMAIRC) is proposed to combine the signals in two base station antennas. With the applica- tion of MSMAIRC and in the absents of additive white Gaussian noise (AWGN), the resulting signal-to-MAI ratio (SMAIR) is not only maximized but also in- dependent of cross polarization discrimination (XPD) and antenna angle. In the case when AWGN is present, the performance of MSMAIRC is still affected by the XPD and antenna angle, but to a much lesser degree than the traditional maximal ratio combining (MRC). Furthermore, this research found that the BER performance for Pol/MC-CDMA can be further improved by changing the angle between the two receiving antennas. Hence the optimum antenna angles for both MSMAIRC and MRC are derived and their effects on the BER performance are compared. With the derived optimum antenna angle, the Pol/MC-CDMA system is able to obtain the lowest BER for a given XPD.

The placement of base stations is an important issue in planning wireless systems because it has a significant influence on overall system performance. In order to achieve good performance in an interference limited CDMA system, a large number of variables must be considered simultaneously during the planning stage. A traditional manual planning approach that involves an iterative application of analysis may not produce satisfactory results since it can only consider a small number of variables simultaneously. This thesis proposes the use of automatic optimisation that allows more variables to be considered and more solutions to be examined within the same time period. This thesis aims to produce a unique framework for creating an automatic optimisation tool for solving the CDMA base station placement problem. This framework contains a number of mathematical models that describe various deployment scenarios and a number of customised optimisation algorithms that solve these models. Although the work presented in this thesis does not result in a complete design tool, the findings are expected to provide a solid foundation for the development of such a tool. During the course of study, a number of issues associated with the proposed planning approach have been discussed and some future research directions have been identified. The results from the example problems have shown that automatic optimisation has the potential to reduce the planning time significantly, assess system performance accurately and utilise limited resources efficiently. These benefits certainly confirm the need for such a tool and reinforce the importance of the work documented in this thesis. / Industrial Research Limited and Telecom NZ Limited

The placement of base stations is an important issue in planning wireless systems because it has a significant influence on overall system performance. In order to achieve good performance in an interference limited CDMA system, a large number of variables must be considered simultaneously during the planning stage. A traditional manual planning approach that involves an iterative application of analysis may not produce satisfactory results since it can only consider a small number of variables simultaneously. This thesis proposes the use of automatic optimisation that allows more variables to be considered and more solutions to be examined within the same time period. This thesis aims to produce a unique framework for creating an automatic optimisation tool for solving the CDMA base station placement problem. This framework contains a number of mathematical models that describe various deployment scenarios and a number of customised optimisation algorithms that solve these models. Although the work presented in this thesis does not result in a complete design tool, the findings are expected to provide a solid foundation for the development of such a tool. During the course of study, a number of issues associated with the proposed planning approach have been discussed and some future research directions have been identified. The results from the example problems have shown that automatic optimisation has the potential to reduce the planning time significantly, assess system performance accurately and utilise limited resources efficiently. These benefits certainly confirm the need for such a tool and reinforce the importance of the work documented in this thesis. / Industrial Research Limited and Telecom NZ Limited

The placement of base stations is an important issue in planning wireless systems because it has a significant influence on overall system performance. In order to achieve good performance in an interference limited CDMA system, a large number of variables must be considered simultaneously during the planning stage. A traditional manual planning approach that involves an iterative application of analysis may not produce satisfactory results since it can only consider a small number of variables simultaneously. This thesis proposes the use of automatic optimisation that allows more variables to be considered and more solutions to be examined within the same time period. This thesis aims to produce a unique framework for creating an automatic optimisation tool for solving the CDMA base station placement problem. This framework contains a number of mathematical models that describe various deployment scenarios and a number of customised optimisation algorithms that solve these models. Although the work presented in this thesis does not result in a complete design tool, the findings are expected to provide a solid foundation for the development of such a tool. During the course of study, a number of issues associated with the proposed planning approach have been discussed and some future research directions have been identified. The results from the example problems have shown that automatic optimisation has the potential to reduce the planning time significantly, assess system performance accurately and utilise limited resources efficiently. These benefits certainly confirm the need for such a tool and reinforce the importance of the work documented in this thesis. / Industrial Research Limited and Telecom NZ Limited

The placement of base stations is an important issue in planning wireless systems because it has a significant influence on overall system performance. In order to achieve good performance in an interference limited CDMA system, a large number of variables must be considered simultaneously during the planning stage. A traditional manual planning approach that involves an iterative application of analysis may not produce satisfactory results since it can only consider a small number of variables simultaneously. This thesis proposes the use of automatic optimisation that allows more variables to be considered and more solutions to be examined within the same time period. This thesis aims to produce a unique framework for creating an automatic optimisation tool for solving the CDMA base station placement problem. This framework contains a number of mathematical models that describe various deployment scenarios and a number of customised optimisation algorithms that solve these models. Although the work presented in this thesis does not result in a complete design tool, the findings are expected to provide a solid foundation for the development of such a tool. During the course of study, a number of issues associated with the proposed planning approach have been discussed and some future research directions have been identified. The results from the example problems have shown that automatic optimisation has the potential to reduce the planning time significantly, assess system performance accurately and utilise limited resources efficiently. These benefits certainly confirm the need for such a tool and reinforce the importance of the work documented in this thesis. / Industrial Research Limited and Telecom NZ Limited