The Group Research department in Tait Electronics has a reconfigurable platform for MIMO research. In particular, the platform has an adaptive multivariate DFE with the LMS algorithm currently implemented. The LMS algorithm has been simulated and optimised for implementation on the FPGA. The main objective of the research is to investigate an alternative, the RLS algorithm by comparing its performance to the LMS algorithm. The RLS algorithm is known to be more complex than the LMS algorithm but offers the potential for improved performance due to its fast-converging nature. This thesis provides a performance investigation of these adaptive filter algorithms on the MIMO system for the purpose of real-time implementation on the Tait platform. In addition to performance investigation, stability analysis and a feasibility study is shown for the RLS algorithm on the FPGA. The research is industry based and is supported by FRST.

Broadband wireless access systems can be used to deliver a variety of high data rate applications and services. Many of the channels being considered for such applications exhibit multipath propagation coupled with large delay spreads. Cur- rently, orthogonal frequency division multiplexing is employed in these channels to compensate the effect of dispersion. Single carrier (SC) modulation in conjunc- tion with frequency-domain equalization (FDE) at the receiver has been shown to be a practical alternate solution as it has lower peak to average power ratio and is less sensitive to frequency offsets and phase noise compared to OFDM. The effect of multipath propagation increases with increasing data rate for SC systems. This leads to larger inter-symbol-interference (ISI) spans. In addition the achievable ca- pacity of SC-broadband systems depends on their ability to accommodate multiple signal transmissions in the same frequency band, which results in co-channel inter- ference (CCI) when detecting the desired data stream. The effects of CCI and ISI are more pronounced at high data rates. The objective of this research is to investi- gate and a develop low-complexity frequency domain receiver architectures capable of suppressing both CCI and ISI and employing practical channel estimation. In this thesis, a linear and a non-linear receiver architecture are developed in the frequency domain for use in highly dispersive channels employing multiple input multiple output (MIMO) antennas. The linear receiver consists of parallel branches each corresponding to a transmit data stream and implements linear equalization and demodulation. Frequency domain joint CCI mitigation and ISI equalization is implemented based on estimated channel parameters and is called space-frequency Broadband wireless access systems can be used to deliver a variety of high data rate applications and services. Many of the channels being considered for such applications exhibit multipath propagation coupled with large delay spreads. Cur- rently, orthogonal frequency division multiplexing is employed in these channels to compensate the effect of dispersion. Single carrier (SC) modulation in conjunc- tion with frequency-domain equalization (FDE) at the receiver has been shown to be a practical alternate solution as it has lower peak to average power ratio and is less sensitive to frequency offsets and phase noise compared to OFDM. The effect of multipath propagation increases with increasing data rate for SC systems. This leads to larger inter-symbol-interference (ISI) spans. In addition the achievable ca- pacity of SC-broadband systems depends on their ability to accommodate multiple signal transmissions in the same frequency band, which results in co-channel inter- ference (CCI) when detecting the desired data stream. The effects of CCI and ISI are more pronounced at high data rates. The objective of this research is to investi- gate and a develop low-complexity frequency domain receiver architectures capable of suppressing both CCI and ISI and employing practical channel estimation. In this thesis, a linear and a non-linear receiver architecture are developed in the frequency domain for use in highly dispersive channels employing multiple input multiple output (MIMO) antennas. The linear receiver consists of parallel branches each corresponding to a transmit data stream and implements linear equalization and demodulation. Frequency domain joint CCI mitigation and ISI equalization is implemented based on estimated channel parameters and is called space-frequency

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.

les travaux portent sur la mise en oeuvre d'un système de communication sur une plate-forme SUNDANCE, comportnat DSP et fPGA.<br />Les techniques MIMO, OFDM et CDMA sont combinées afin de profiter de la diversité fréquentielle, spatiale<br />Un nouveau schéma de codage MIMO / OFDM est proposé

The architecture of cellular networks has been undergoing an extraordinarily fast evolution in the last years to keep up with the ever increasing user demands for wireless data and services. Motivated by a search for a breakthrough in network capacity, the paradigm of heterogeneous networks (HetNets) has become prominent in modern cellular systems, where carefully deployed macrocells coexist with layers of irregularly deployed cells of reduced coverage sizes. Users can thus be offloaded from the macrocell and the capacity of the network increases. However, universal frequency reuse is usually employed to maximize capacity gains, thereby introducing the fundamental problem of inter-cell interference (ICI) in the network caused by the sharing of the spectrum among the different tiers of the HetNet. The objective of this PhD thesis is to provide analysis and mitigation techniques for the fundamental problem of interference in heterogeneous cellular networks. First, the interference of a two-tier network is modeled and analyzed by making use of spatial statistics tools that allow the reconstruction of complete coverage maps. A correlation analysis is then performed by deriving a spatial coverage cross-tier correlation function. Second, a novel architecture design is proposed to minimize interference in HetNets whose base stations may be equipped with very large antenna arrays, another key technology of future wireless systems. Then, we present interference mitigation techniques for different types of small cells, namely picocells and femtocells. In the third contribution of this thesis, we analyze the case of clustered deployments by proposing and comparing techniques suitable for this scenario. Fourth, we tackle the case of femtocell deployments by analyzing the degrading effect of interference and proposing new mitigation methods. Fifth, we introduce femtorelays, a novel small cell access technology that combats interference in femtocell networks and provides higher backhaul capacity.

Lattice-Reduction has become a popular way of improving the performance of MIMO detectors. However, developing an efficient high-throughput VLSI implementation of LR has been a major challenge in the literature. This thesis proposes a hardware-optimized version of the popular LLL algorithm that reduces its complexity by 70% and achieves a fixed runtime while maintaining ML diversity. The proposed algorithm is implemented for 4x4 MIMO systems and uses a novel pipelined architecture that achieves a fixed low processing latency of 40 cycles, resulting in a fixed throughput that is independent of the channel correlation. The proposed LR core, fabricated in 0.13um CMOS, is the first fabricated and tested LR ASIC implementation in the literature. Test results show that the LR core achieves a maximum clock rate of 204 MHz, yielding a throughput of 510 Mbps, thus satisfying the aggressive throughput requirements of emerging 4G wireless standards, such as IEEE-802.16m and LTE-Advanced.

Lattice-Reduction has become a popular way of improving the performance of MIMO detectors. However, developing an efficient high-throughput VLSI implementation of LR has been a major challenge in the literature. This thesis proposes a hardware-optimized version of the popular LLL algorithm that reduces its complexity by 70% and achieves a fixed runtime while maintaining ML diversity. The proposed algorithm is implemented for 4x4 MIMO systems and uses a novel pipelined architecture that achieves a fixed low processing latency of 40 cycles, resulting in a fixed throughput that is independent of the channel correlation. The proposed LR core, fabricated in 0.13um CMOS, is the first fabricated and tested LR ASIC implementation in the literature. Test results show that the LR core achieves a maximum clock rate of 204 MHz, yielding a throughput of 510 Mbps, thus satisfying the aggressive throughput requirements of emerging 4G wireless standards, such as IEEE-802.16m and LTE-Advanced.

Resource management in wireless networks is one of the key factors in maximizing the overall throughput. Contrary to popular belief, dividing the resources in a dense network does not yield the best results. A method that has been developed recently shares the spectrum amongst all the users in such a way that each node can potentially utilize about half of all the available resources. This new technique is often referred to as Interference Alignment and excels based on the fact that the amount of the network resources assigned to a user does not go to zero as the number of users in the network increases. Unfortunately it is still very difficult to implement the interference alignment concepts in practice. This thesis investigates some of the low-complexity solutions to integrate interference alignment ideas into the existing wireless networks. In the third and fourth chapters of this thesis, it is shown that introducing relays to a quasi-static wireless network can be very beneficial in terms of achieving higher degrees of freedom. The relays store the signals being communicated in the network and then send a linear combination of those signals. Using the proposed scheme, it is shown that although the relays cannot decode the original information, they can transform the equivalent channel in such a way that performing interference alignment becomes much easier. Investigating the required output power of the relays shows that it can scale either slower or faster than the output power of the main transmitters. This opens new doors for the applications that have constraints on the accessible output powers in the network nodes. The results are valid for both $X$ Channel and Interference Channel network topologies. In Chapter Five, the similarities between full-duplex transmitters and relays are examined. The results suggest that the transmitters can play the relay roles for offering easier interference alignment. Similar to the relay-based alignment, in the presented scheme full-duplex transmitters listen to the signals from other transmitters and use this information during the subsequent transmission periods. Studying the functionality of the full-duplex transmitters from the receivers' side shows the benefits of having a minimal cooperation between transmitters without even being able to decode the signals. It is also proved that the degrees of freedom for the $N$-user Interference Channel with full-duplex transmitters can be $\sqrt{\frac{N}{2}}$. The results offer an easy way to recover a portion of degrees of freedom with manageable complexity suited for practical systems.

Thesis (Ph. D.)--University of Hawaii at Manoa, 2005. / Includes bibliographical references (leaves 84-89). / Also available by subscription via World Wide Web / xi, 89 leaves, bound ill. 29 cm

In the past two decades, wireless communication systems have grown with an unprecedented speed from radio paging and cellular telephony to multimedia platforms offering voice and video streaming . One undesired outcome of this expansion is a heavy utilization of the available frequency spectrum. Particular pressure comes from new multimedia applications, which require larger operational bandwidth for their implementations. Conventional coding, modulation and multiplexing techniques are unable to overcome the problem associated with the limited frequency spectrum, and therefore modern wireless systems are improved through the utilization of the space/angle domain. In order to improve capacity and reliability with the space/angular domain, wireless systems require the use of multiple element antennas (MEA) accompanied by appropriate signal processing algorithms. Typically multiple antennas are used to steer the beams of the line of sight (LOS) signal toward desired users and nulls in the direction of undesired users. However, in the case of indoor environments, the presence of reflections, scattering and refraction caused by the environment, it is better to make use of non-line of sight (NLOS) signal propagation. As these types of MEA antenna systems are a relatively new concept in wireless communications, their potential needs be tested experimentally in real world conditions. To achieve this goal, prototype systems capable to implement various modulation, coding and transmission schemes for MEA are required. This thesis investigates the benefits of MEA systems by building and testing such systems in indoor environments. The project area spans across many disciplines including wireless communications, antennas, embedded systems and RF hardware design, and therefore the thesis begins with essential background information. This concerns some fundamental concepts of a wireless communication channel and its information capacity. These are accompanied by ample considerations of signal propagation and adverse effects of reflection, scattering and diffraction. Also included are the signal modulation and coding. Following this background information, the main topic concerning diversity and multiple-input multiple output system that involves the use of multiple element antennas is introduced. This background material sets the reasons for investigating of two types wireless communication systems that include multiple element antennas: antenna diversity and MIMO. Following the literature review, the thesis reports on investigations that realize the thesis aims. The first part of the undertaken investigations concerns an indoor 2×2 MEA diversity system in which MEAs accompany conventional transceivers. In the experiments, Bluetooth transceivers aimed for a short range operation at 2.45 GHz are used, which are both connected to a 2-element antenna array. The connection is made via a switched beamforming network which involves 4-port hybrid circuits. Two ports of these hybrids are used for connecting antennas, while the one of the remaining two is connected to the Tx or Rx transceiver. By switching between these two input ports of the hybrid, two different radiation patterns can be formed, at both Tx and Rx. One Bluetooth transceiver is stationary while the other is made mobile by employing a purpose built mechanical sub-system covering the precise movement within a circle of 3 m. Both the movement and collection of the data as well as the display of the obtained results are accomplished with the in-house developed software run on a micro-controller and computer. Experimentally, it is shown that the proper Tx and Rx mode for a given position, improves the received signal strength. This leads to improved signal to noise ratio (SNR) and thus the quality of signal transmission. The implementation of this concept only requires a signal quality indicator, and simple feedback between the receiver and the transmitter. In the selected transceivers, "RSSI" was the quality indicator used, and is present in many modern wireless transceivers. Also, any signal quality indicator can be used. Although the experiments were performed with respect to the transmit/receive pattern diversity, they can also be easily extended to other forms of antenna diversity such as polarization or field diversity. The undertaken investigations are original in terms of the full proof of benefits of pattern diversity for indoor wireless systems. The second part of the undertaken investigations focuses on the design, development and testing of a full indoor multiple element antenna system. This demonstrator system includes two main modules: the baseband processor (based on a field programmable gate array) and the RF front end. The FPGA signal processing module is designed around the Altera Stratix II S260 chip, which is commercially available. Suitable hardware design is required to accomplish MIMO signal transmission. The RF front end module performing direct conversion between baseband and 2.45 GHz or 5 GHz radio frequency bands uses the commercially available MAX2829 chip. The interface between FPGA and RF front end is a set of analogue to digital (ADC) and digital to analogue (DAC) converters that operate on signals between the FPGA and the RF transmitter/receiver modules. They are capable of handling 12/14 bit signals at up to 125 MSmp/sec. The data rate chosen in these investigations is 3.125 Mbps. In addition to the MAX2829 IC chip, amplifiers, switches and antennas are included in the RF module. The development of this wireless communication system has been accomplished through a number of design, development and testing stages. Most of the research effort concerned FPGA based signal processing because this part of the system is where the information processing takes place. For the MIMO system, the transmitted signal has to be modulated and coded, with efficient utilization of the multiple element antennas in both these processes. The prerequisite to signal demodulation is signal synchronization. In turn, the decoding requires the knowledge of characteristics of the channels that are formed between transmitting and receiving antennas. For an efficient FPGA hardware design, all the numerical operations must occur in fixed point arithmetic. To accomplish all of these functions, suitable baseband signal processing algorithms were developed as part of the thesis work. First, they were written in MATLAB and then transferred to C++ which is closer to the FPGA implementation. Having confirmed their validity, they were hardware deployed. In the investigated MIMO demonstrator, QPSK modulation and the Alamouti coding scheme were selected for modulating and coding of the transmitted signal. The implementation of the hardware baseband module was validated using a purpose developed channel emulator. This emulator was capable of implementing the channel properties from actual measurements and from theoretical models. The applied theoretical models concern the single and double bounce scattering models, as well as a full EM model and include full EM interactions within array antennas formed by wire dipoles. These models produce random characteristics of the complex channel matrix which describes the channel properties for narrow or wideband case. With this channel emulator, investigations were performed with respect to channel estimation. The training and semi-blind channel estimation methods were tested using the developed emulator. To schedule signal transmission as well as to obtain suitable insight into individual processes, two extra modules were developed as part of the thesis project. These are the scheduler and visualisation modules. The scheduling hardware controls data packets for at the transmitter, and oversees the packets being decoded at the receiver module. For the visualization module, specialized hardware buffers and analysis modules are created for data storage. The signals resulting from the encoding and decoding processes are stored in these buffers, synchronized to each other, which allows for synchronous visualization of the signals. The data from these buffers is streamed to a PC via a 100 Mbit Ethernet connection and a soft-core processor (running uClinux) in the baseband board. Using a web browser on the PC, a graphical interface using scalable vector graphics (SVG) is used for interaction with the embedded web server to display and control what the hardware is sending and receiving. Due to latency, only a quasi-real time display on PC is possible, as 10 ms of time domain data takes 60 ms to display. The FPGA hardware performs real-time continuous data transmission and decoding, and the latency is only in the visualization system. Using the developed baseband system it was shown that the proposed semi-blind channel estimation was advantageous over the classical training approach when the channel properties change during packets transmissions. The developed channel emulator, semi-blind channel estimation algorithm and the visualisation software are the original contributions of this thesis. Having established the proper functioning of the FPGA baseband processor, the remaining investigations concerned the development of the RF transceiver module. This task was accomplished using guidelines offered by the MAX chip manufacturer. The challenge concerned its manufacturing in 4-layer board format. This part of the project required the outsourcing of the PCB manufacturing and component assembly to obtain successful production of the RF front-end board. The RF tests undertaken as part of the project verified the operation of this RF hardware. With the successful development of individual baseband and RF modules, the last part of project concerned the integration of them. Because most of the benefits of the 2×2 MIMO system were demonstrated via the use of a channel emulator, this part of the thesis consisted of the results of a number of experiments. Considerable effort was spent for the full integration of the RF and baseband modules to make them ready for real-time operation. Some of the undertaken tasks were new, as they were not required for experiments using only the baseband system and channel emulator. One of the new challenges concerned proper symbol synchronization. Two novel algorithms were proposed and verified. One of these were based on a simple comparison between "I" and "Q" components of the received signal and the other one involving a correlation of the signal to a known training sequence. The last experiment involved the experimental measurements of signals transmitted over air using the testbed. As the number of interfaces was limited only one transmitting and one receiving antenna was connected to the 2×2 baseband system. However, the Alamouti scheme is able to function when only one of the two antenna is connected, and therefore real-time performance in an indoor environment was successfully tested. The presented designs, algorithms and visualisation form a strong platform for other researchers to continue and expand the work done in this project.