Avec l'augmentation du trafic de données, la multiplication des objets connectés et la diversification des types de communication, la cinquième génération de réseaux cellulaires (5G) doit relever un grand nombre de défis. Dans ce contexte, les systèmes« massive MIMO » présentent de nombreux avantages en utilisant un grand nombre d'antennes combiné à des techniques de traitement de signal adaptées. De plus, l'utilisation de la modulation FBMC/OQAM au lieu de la modulation OFDM pourrait améliorer la performance des systèmes dans ce11aines situations. En premier lieu, cette thèse se centre sur des scénarios véhiculaires. En par1iculier, les systèmes« massive MIMO » sont proposés dans le but de combattre les interférences dues à l'effet Doppler pour la voie montante. Nous montrons ainsi de manière analytique que l'augmentation du nombre d'antennes implique une réduction drastique de l'impact de l'effet Doppler. De plus, les performances des modulations OFDM et FBMC/OQAM sont comparées dans ce contexte pour des environnements« Non-Line-Of-Sight » (NLOS) et« Line-Of-Sight » (LOS). Le second scéna1io étudié dans cette thèse considère les communications dans des zones mal desservies. Dans ce contexte, les systèmes« massive MIMO » permettent de créer un lien sans-fil longue-po11ée de type« backhaul » entre deux stations de base. Ainsi, le coût de déploiement des réseaux r cellulaires est réduit. Dans cette thèse, un nouveau précodeur « massive MIMO » est proposé dans le but d'utiliser la même bande de fréquence pour le liens accès et« backhaul ». De plus, l'impact d'une désynchronisation entre les liens d'accès et le lien « backhaul » est étudié et l'utilisation de la modulation FBMC/OQAM pour le lien« backhaul » est examinée. / ESUME DE LA THESE EN ANGLAIS With the increase of the global data tmffic, the multiplication of co1mected devices and the diversification of the communication types, the fifth generation of cellular networks (5G) has to overcome a se1ies of challenges. In this context, massive MlMO systems hold a wide range of benefits by using a large number of antennas combined with appropriate signal processing techniques. Additionally, the use of the FBMC/OQAM modulation instead of the classical OFDM modulation may enhance the performance of the systems in cer1ain situations. Firstly, this thesis focuses on vehicular scenarios. In par1icular, massive MIMO systems are proposed to overcome the interference due to the Doppler effect for the uplink. We thus analytically highlight that increasing the number of receive antermas induces a drastic reduction of the impact of the Doppler effect. Moreover, the perfonnance of the OFDM and the FBMC/OQAM modulations are compared in this context for Non-Line-Of-Sight (NLOS) and Line-Of-Sight (LOS) environments. The second scenario investigated in this thesis considers communications in wide underse1ved areas. In this context, massive MIMO systems allow to create a long-range wireless back.haul link between two base stations. Thereby, the cost of deployment of the cellular networks is reduced. In this thesis r a new massive MLMO precoding technique is proposed in order to use the same fequency band for the backhaul link and the access links. Moreover, the impact of a desynchronization between the back haul link and the access links is studied and the use of the FBMC/OQAM modulation for the backhaul link is discussed.

Recently, there are great interests in the location-based applications and the location-awareness of mobile wireless systems in indoor areas, which require accurate location estimation in indoor environments. The traditional geolocation systems such as the GPS are not designed for indoor applications, and cannot provide accurate location estimation in indoor environments. Therefore, there is a need for new location finding techniques and systems for indoor geolocation applications. In this thesis, a wide variety of technical aspects and challenging issues involved in the design and performance evaluation of indoor geolocation systems are presented first. Then the TOA estimation techniques are studied in details for use in indoor multipath channels, including the maximum-likelihood technique, the MUSIC super-resolution technique, and diversity techniques as well as various issues involved in the practical implementation. It is shown that due to the complexity of indoor radio propagation channels, dramatically large estimation errors may occur with the traditional techniques, and the super-resolution techniques can significantly improve the performance of the TOA estimation in indoor environments. Also, diversity techniques, especially the frequency-diversity with the CMDCS, can further improve the performance of the super-resolution techniques.

O consumo de dados em dispositivos móveis cresce em taxas que dobram a cada ano. Tal crescimento demonstra como os dispositivos móveis ganham importância e como eles têm sido usados no dia a dia da população. Entretanto, o acesso à Internet ainda possui alto custo e nem sempre está disponível. Esse cenário apresenta o desafio de mantermos o uso dos dispositivos móveis acessível e viável, mesmo quando a Internet não esteja disponível. A comunicação direta entre os dispositivos é vista como alternativa para comunicação sem Internet e, consequentemente, para a redução do tráfego de dados nas redes de celulares. Além disso, ela pode ser útil para manter os dispositivos comunicando entre si mesmo desconectados da Internet. O protocolo Wi-Fi Direct (WD) é uma referência para esse tipo de comunicação, uma vez que seu protocolo não demanda infraestrutura de rede pré-estabelecida para que a comunicação aconteça e utiliza hardware padrão para comunicação Wi-Fi. Apesar dessas vantagens, seu uso é pouco difundido, o que o torna desconhecido pelos usuários, sendo uma das possíveis causas a complexidade de uso. De forma diferente, a conexão com a Internet, que acontece de forma quase espontânea, no WD as partes envolvidas precisam se envolver ativamente, na escolha e autorização, para que a conexão seja estabelecida. A complexidade da comunicação entre dispositivo pode ser constatada quando os usuários utilizam a Internet para enviar dados mesmo que o dispositivo alvo esteja ao lado da origem. Para superar esse obstáculo, a conexão entre os dispositivos deve ser tão ou mais simples do que a ação de enviar um e-mail ou uma mensagem instantânea usando a Internet. Para lidar com esse cenário, este trabalho propõe uma alternativa para comunicação entre dispositivos próximos que não demanda autorização manual prévia a cada conexão com um dispositivo, e que, ainda assim, permita que o usuário decida se quer ou não usar os dados transmitidos por uma conexão. Para isso definimos uma arquitetura que possibilite a conexão e transferência de dados entre os dispositivos próximos sem a necessidade de intervenção prévia do usuário e implementamos o conceito proposto no sistema operacional para dispositivos móveis Android / The consumption data on mobile devices is growing at rates double every year. This growth demonstrates how mobile devices gain importance and how they have been used in everyday life of the population. However, the internet also has high cost and is not always available. This scenario presents the challenge of maintaining the use of affordable and viable mobile devices even when the Internet is not available. Direct communication between the devices is regarded as no alternative for internet communication and, consequently, to reduce the data traffic in cellular networks. Furthermore, it can be useful to keep the devices communicating among themselves disconnected from the Internet. The Wi-Fi Direct (WD) protocol is a reference to this type of communication, since its protocol does not require pre-established network infrastructure for communication to happen and uses standard hardware for Wi-Fi communication. Despite these advantages, its use is not widespread, making it unknown to the users, one of the possible causes of the complexity of use. Differently, the connection to the Internet, which happens almost spontaneously, the WD parties need to engage actively in the selection and authorization for the connection to be established. The complexity of communication between device can be found when users use the Internet to send data even if the target device is adjacent to the source. To overcome this obstacle, the connection between the devices should be as or more simple than the action of sending an email or an instant message using the Internet. To handle this scenario, this paper proposes an alternative for communication between nearby devices that does not require prior manual authorization for each connection to a device, and that still allow the user to decide whether or not to use the data transmitted by a connection. For this we define an architecture that enables the connection and data transfer between nearby devices without the need for prior user intervention and implement the concept proposed in the Android operating system for mobile devices

Este trabalho apresenta uma ferramenta de simulação computacional de canal de propagação para ambiente macro-celular baseada em modelos geométricos e no modelo estatístico apresentado no relatório COST 259 DCM. Para a implementação desta ferramenta é realizada, inicialmente, uma abordagem dos principais modelos de predição de perda por propagação, utilizados atualmente, assim como, um estudo dos modelos geométricos que fornecem as informações de distribuição de potência temporal e angular para diferentes tipos de distribuições estatísticas de espalhadores. A modelagem geométrica utiliza grupos independentes no qual os espalhadores são distribuídos com uma densidade Gaussiana. A utilização desta distribuição Gaussiana leva a distribuições de atraso e ângulo de chegada mais próximas dos resultados de medições do que o usando distribuição uniforme. A base geométrica define o conceito direcional e temporal. A base estatística define o número de grupo de espalhadores adicionais e suas localizações, quando estes existiram. Efeitos como: direção e potência de chegada de cada grupo de espalhadores, a presença ou não de visada direta entre transmissor e receptor a medida que a estação móvel percorre uma célula e a variação da polarização cruzada foram implementados nesse simulador. Desta forma, essa ferramenta computacional simula tanto a dispersão temporal, presente nos modelos de banda larga, como a dispersão angular, utilizadas em sistemas de comunicação móveis que exploram a diversidade espacial. / This work present a simulation tool for macro cell environment based on geometrical and statistical representation of the scatterers and on the COST 259 Directional Channel Model (DCM). A comprehensive review of the propagation prediction models for terrestrial wireless communication systems and geometric channel models, that provide, times of arrival (TOA) and the angle of arrival (AOA) for diferents statistics scatterers distribution is realized. This tool uses gaussianly distributed scatterers for each cluster. This distribution is naturally more realistic than the uniform distribution leading closer to experimental results. This geometrically based model simulates the TOA dispersion present in wide band channel models and the AOA dispersion necessary for systems that explore spatial diversity. This tool also incorporates the concept of line-of-sight and non-line-of-sight and its birth and death as the mobile station moves in a cell, as well as the appearance and disappearance of additional clusters of scatterers. The output provided by this simulation tool is comprised of all the complex amplitudes, delays and angles of arrival of all multipath components associated with each cluster of scatterers. Mean attenuation and slow fading effects are also incorporated to the model and fast fading appears as a consequence of the multipath interference.

The objective of the thesis is concerned on the problem of detecting superpositional signals in a wireless channel. In many wireless systems, an observed signal is commonly represented as a linear combination of the transmitted signal with the interfering signals dispersed in space and time. These systems are generally known as the interference-limited systems. The mathematical model of these systems is generally referred as a superpositional model. A distinguished characteristic of signal transmission in a time-varying wireless channel is that the channel process is not known a priori. Reliable signal reception inherently requires exploiting the structure of the interfering signals under channel uncertainty. Our goal is to design computational efficient receivers for various interference-limited systems by using advanced statistical signal processing techniques. The thesis consists of four main parts. Firstly, we have proposed a novel Multi-Input Multi-Output (MIMO) signal detector, known as the neighbourhood exploring detector (NED). According to the maximum likelihood principle, the space time MIMO detection problem is equivalent to a NP-hard combinatorial optimization problem. The proposed detector is a sub-optimal maximum likelihood detector which eliminates exhaustive multidimensional searches. Secondly, we address the problem of signal synchronization for Global Positioning System (GPS) in a multipath environment. The problem of multipath mitigation constitutes a joint estimation of the unknown amplitudes, phases and time delays of the linearly combined signals. The complexity of the nonlinear joint estimation problem increases exponentially with the number of signals. We have proposed two robust GPS code acquisition systems with low complexities. Thirdly, we deal with the problem of multipath mitigation in the spatial domain. A GPS receiver integrated with the Inertial Navigation System (INS) and a multiple antenna array is considered. We have designed a software based GPS receiver which effectively estimates the directions of arrival and the time of arrival of the linearly combined signals. Finally, the problem of communications with unknown channel state information is investigated. Conventionally, the information theoretical communication problem and the channel estimation problem are decoupled. However the training sequence, which facilitates the estimation of the channel, reduces the throughput of the channel. We have analytically derived the optimal length of the training sequence which maximizes the mutual information in a block fading channel.

The exploitation of the theoretically enormous capacity achieved by the multiple transmit and receive antennas systems (MIMO) in a rich scattering communication channel has been the subject of vast body of research on the field of MIMO. In particular, the Vertically-layered Bell Laboratories Layered Space-Time (V-BLAST) is a well known MIMO architecture which has demonstrated the enormous capacity of 20-40 bit/s/Hz in an indoor propagation environment with realistic SNR and error rates. However, due to the intensive computation involved, it would be difficult to implement this architecture for high data rate communication systems. Some works have been done to improve the receiver complexity and performance by coding techniques, by different detection architectures. In this thesis, we have focused on QR-based decoders for V-BLAST MIMO. For a suitable V-BLAST detection implementation, we need to carefully consider the problem from algorithmic, arithmetic and architectural aspects. At the algorithmic level, the numerical stability and robustness should be considered. At the arithmetic level, signal quantization is important, and, at the architectural level, parallelism and pipelining require attention. We have performed the above mentioned optimization on the 1-pass QR factorization with back substitution SIC (Symbol Interference Cancellation) decoder in chapter 3. At first optimizations are made on the proposed algorithm and architecture using MATLAB simulations. Then a new architecture for the QR-factorizer as the core processor of the V-BLAST decoder is developed in chapter 4. This architecture uses only two low complexity CORDIC (Coordinate rotation digital computer) processors. The parameterized feature of the controller and address generator blocks of this architecture has provided a scalable architecture for the implementation of QR factorization for square matrix of any dimension. The reduced hardware complexity of the processors and its simple parameterized controller are two outstanding features of the architecture, resulting in a more suitable alternative architecture for QR factorization than traditional triangular systolic arrays. In the next phase of the research, new hardware architectures of the back substitution SIC decoder was developed for a 4 X 4 MIMO system with 16-QAM constellation scheme in chapter 5. The division operation for back substitution needs a complex hardware, and results in the numerical instability. In the proposed hardware the elimination of division and modification of multiplier has reduced the hardware complexity and led to numerical stability. In addition the pre decoding block was designed and optimized in terms of number of the pipeline registers and CORDIC rotator processors. The developed hardware is capable of processing 20 vectors data burst and results in a throughput of 149 Mb/s. The FPGA (Field Programmable Gate Array) and ASIC (Application specific Integrated Circuit) implementations of the proposed optimized architecture are presented in Chapter 5. We found that the equivalent gates and the core area in our design is less than 30% of other designs and the maximum clock frequency and the throughput is higher (175 %) than other works. Finally the improvements of the BER performance using the branching method and parallel architectures are presented in chapter 6. In this supplementary part to back substitution OSIC decoder, the final symbol vector is selected from 2 or 8 potential candidates based on the minimum Euclidean norm, which improves the BER between 3 to 7 db and gives a very close match to the original V-BLAST performance.

Spread spectrum techniques have a number of different applications, including range finding, synchronisation, anti-jamming systems and multiple access communication systems. In each of these applications the properties of the resulting systems depend heavily on the family of spreading sequences employed. As such, the design of spreading sequences is an important area of research. Two areas of spreading sequence design are of particular interest in this work, combination techniques and Interference Free Window (IFW) sequences. Combination techniques allow a new sequence family to be constructed by combining two or more existing families. Such an approach allows some of the desirable properties of the components to be maintained, whilst mitigating the components' disadvantages. In addition, it can facilitate the construction of large families at a greatly reduced computational cost. Combination families are considered through the construction of two new classes of sequences, modified Unified Complex Hadamard Transform (UCHT) sequences, and combination Oppermann sequences, respectively based on UCHT sequences and periodic Oppermann sequences. Numerical optimisation techniques are employed to demonstrate the favourable performance of sequences from these classes compared to conventional families. Second, IFW sequences are considered. In systems where approximate, but not perfect, synchronisation between different users can be maintained, IFW sequences can be employed to greatly reduce both interference between users and interference resulting from multipath spread of each user's signal. Large Area Synchronous (LAS) sequences are a class of sequences which both result from combination techniques and exhibit an IFW. LAS sequences are produced by combining Large Area (LA) sequences and LS sequences. They have been demonstrated to be applicable to multiple access communication systems, particularly through their use in LAS2000, which was proposed for third generation mobile telephony. Work to date has been restricted to only a very small range of examples of these families. In order to examine a wider range of LAS sequences, the construction and resulting properties of LA and LS families are considered. The conditions an LA family must satisfy are codified here, and algorithms which can be used to construct LA families with given parameters are presented. The construction of LS sequences is considered, and relationship between each of the parameters used in this construction and the properties of the final family is examined. Using this expanded understanding of both these sequence families, a far wider range of LAS families, potentially applicable to a wider range of applications, can be considered. Initially, the merits of proposed sequences are considered primarily through their correlation properties. Both maximum and mean squared correlation values are considered, depending on the context. In order to demonstrate their practical applicability, combination Oppermann, modified UCHT and LAS sequences are employed in a simulated communications system, and the resulting bit error rates are examined.

The Internet Engineering Task Force (IETF) has recently released network mobility standards that allow deployment of TCP/IP networks onboard a vehicle and maintain permanent network connectivity to the Internet via a vehicular mobile router. This recent development opens up new opportunities for providing efficient mobile computing for users on the move, especially for commuters traveling on public transports. Moreover, central and coordinated management of mobility in a single router, rather than by each user device individually, has numerous advantages. In this architecture, however, it becomes challenging to guarantee network performance due to the mobility of the network and inherently vulnerable nature of wireless links. In this thesis, a detailed performance study of onboard networks is conducted. It has been shown that disruptions in the mobile router connectivity can significantly degrade network throughput. Moreover, factors such as the limited wireless bandwidth of the access link, variations in the bandwidth due to technology switching, and the communication diversity of onboard users all contribute to the problem of unfair sharing of wireless bandwidth. By leveraging the fact that all onboard communications go through the mobile router, performance enhancing solutions are proposed that can be deployed in the mobile router to transparently address the throughput and fairness problems. In this architecture, when the route is known in advance and repetitive (e.g. for public transport or a regularly commuting private vehicle), a certain degree of prediction of impending link disruptions is possible. An anticipatory state freezing mechanism is proposed that relies on the prediction of link disruptions to freeze and unfreeze the state machine of TCP, the widely used transport protocol in the Internet. Simulation study shows that TCP throughput has a non-linear relationship with the prediction accuracy. As prediction accuracy increases, throughput problem diminishes quickly. An adaptive mobile router based fairness control mechanism is proposed to address the unfair sharing of wireless bandwidth in highly dynamic scenarios. The fairness is controlled by dynamically estimating the round-trip-times of all onboard TCP connections and transparently adjusting the protocol control parameters at the router. The thesis also discusses implementation issues for the proposed solutions.

The Internet Engineering Task Force (IETF) has recently released routing standards that allow deployment of TCP/IP local area networks (LANs) onboard a moving vehicle and yet maintain permanent connectivity of the onboard LAN to the Internet via a vehicular mobile router. This recent development opens up new opportunities for providing efficient mobile computing for users on the move, especially for commuters traveling on public transports. Supporting real-time communications, e.g. IP Telephony, on-line video on demand, etc., over such onboard mobile networks is the main motivation of this thesis. Due to the volatility of the wireless bandwidth available to connect the moving LAN to the Internet at different locations of the trip, supporting on-line services that require bandwidth guarantees becomes a challenging task. The main problem investigated is how to provide bandwidth guarantee efficiently, effectively, and in a scalable manner in the context of moving onboard networks. To achieve the goal, a systematic approach is taken that involves (i) designing a signalling protocol that allows transparent bandwidth reservation for the aggregate demand of all onboard users in the vehicle, and (ii) proposing effective aggregation and bandwidth reservation policies that aim to maximize the chances of successful reservation and minimize the bandwidth and processing overhead in critical network elements. Mathematical models are derived to evaluate the performance of proposed solutions. These models are validated using discrete event simulation. One important conclusion reached is that onboard mobile communication provides significant aggregation and centralized management opportunities that must be exploited to provide a scalable solution to the bandwidth guarantee problem in mobile communications. The techniques proposed and analyzed in this thesis to exploit such aggregation opportunities constitute the original contribution to knowledge.

In the first part of this thesis, the information capacity of time-varying fading channels is analysed using finite-state Markov channel (FSMC) models. Both fading channel amplitude and fading channel phase are modelled as finite-state Markov processes. The effect of the number of fading channel gain partitions on the capacity is studied (from 2 to 128 partitions). It is observed that the FSMC capacity is saturated when the number of fading channel gain partitions is larger than 4 to 8 times the number of channel input levels. The rapid FSMC capacity saturation with a small number of fading channel gain partitions can be used for the design of computationally simple receivers, with a negligible loss in the capacity. Furthermore, the effect of fading channel memory order on the capacity is studied (from first- to fourth-order). It is observed that low-order FSMC models can provide higher capacity estimates for fading channels than high-order FSMC models, especially when channel states are poorly observable in the presence of channel noise. To explain the effect of memory order on the FSMC capacity, the capacities of high-order and low-order FSMC models are analytically compared. It is shown that the capacity difference is caused by two factors: 1) the channel entropy difference, and 2) the channel observability difference between the high-order and low-order FSMC models. Due to the existence of the second factor, the capacity of high-order FSMC models can be lower than the capacity of low-order FSMC models. Two sufficient conditions are proven to predict when the low-order FSMC capacity is higher or lower than the high-order FSMC capacity. In the second part of this thesis, a new implicit (blind) channel estimation method in time- varying fading channels is proposed. The information source emits bits ???0??? and ???1??? with unequal probabilities. The unbalanced source distribution is used as a priori known signal structure at the receiver for channel estimation. Compared to pilot-symbol-assisted channel estimation, the proposed channel estimation technique can achieve a superior receiver bit error rate performance, especially at low signal to noise ratio conditions.