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Multiple-input multiple-output (MIMO) wireless technology is an emerging cost- effective approach to offer multiple-fold capacity improvement relative to the conven- tional single-antenna systems. To achieve the capacities of MIMO channels, MIMO bit-interleaved-coded-modulation (BICM) systems with iterative detection and decod- ing (IDD) are studied in this thesis. The research for this dissertation is conducted based on the iterative receivers with convolutional codes and turbo codes. A variety of MIMO detectors, such as a maximum a posteriori probability (MAP) detector, a list sphere detector (LSD) and a parallel interference canceller (PIC) together with a decision statistic combiner (DSC), are studied. The performance of these iterative receivers is investigated via bounding techniques or Monte-Carlos simulations. Moreover, the computational complexities of the components are quantified and compared. The convergence behaviors of the iterative receivers are analyzed via variance trans- fer (VTR) functions and variance exchange graphs (VEGs). The analysis of conver- gence behavior facilitates the finding of components with good matching. For a fast fading channel, we show that the &quotwaterfall region&quot of an iterative receiver can be predicted by VEG. For a slow fading channel, it is shown that the performance of an iterative receiver is essentially limited by the early interception ratio (ECR) which is obtained via simulations. After the transfer properties of the detectors are unveiled, a detection switching (DSW) methodology is proposed and the switching criterion based on cross entropy (CE) is derived. By employing DSW, the performance of an iterative receiver with a list sphere detector (LSD) of a small list size is considerably improved. It is shown that the iterative receiver achieves a performance very close to that with a maximum a posteriori probability (MAP) detector but with a significantly reduced complexity. For an iterative receiver with more than two components, various iteration sched- ules are explored. The schedules are applied in an iterative receiver with PIC-DSC. It is shown that the iterative receiver with a periodic scheduling outperforms that with the conventional scheduling at the same level of complexity.

Doctor of Philosophy (PhD) / This thesis considers transmission techniques for current and future wireless and mobile communications systems. Many of the results are quite general, however there is a particular focus on code-division multiple-access (CDMA) and multi-input multi-output (MIMO) systems. The thesis provides analytical techniques and results for finding key performance metrics such as signal-to-interference and noise power ratios (SINR) and capacity. This thesis considers a large-system analysis of a general linear matrix-vector communications channel, in order to determine the asymptotic performance of linear fixed and adaptive receivers. Unlike many previous large-system analyses, these results cannot be derived directly from results in the literature. This thesis considers a first-principles analytical approach. The technique unifies the analysis of both the minimum-mean-squared-error (MMSE) receiver and the adaptive least-squares (ALS) receiver, and also uses a common approach for both random i.i.d. and random orthogonal precoding. The approach is also used to derive the distribution of sums and products of free random matrices. Expressions for the asymptotic SINR of the MMSE receiver are derived, along with the transient and steady-state SINR of the ALS receiver, trained using either i.i.d. data sequences or orthogonal training sequences. The results are in terms of key system parameters, and allow for arbitrary distributions of the power of each of the data streams and the eigenvalues of the channel correlation matrix. In the case of the ALS receiver, we allow a diagonal loading constant and an arbitrary data windowing function. For i.i.d. training sequences and no diagonal loading, we give a fundamental relationship between the transient/steady-state SINR of the ALS and the MMSE receivers. We demonstrate that for a particular ratio of receive to transmit dimensions and window shape, all channels which have the same MMSE SINR have an identical transient ALS SINR response. We demonstrate several applications of the results, including an optimization of information throughput with respect to training sequence length in coded block transmission.

Doctor of Philosophy(PhD) / In this thesis, we propose and investigate promising approaches for interference mitigation in multiple input multiple output (MIMO) and code division multiple access (CDMA) systems. Future wireless communication systems will have to achieve high spectral efficiencies in order to meet increasing demands for huge data rates in emerging Internet and multimedia services. Multiuser detection and space diversity techniques are the main principles, which enable efficient use of the available spectrum. The main limitation for the applicability of the techniques in these practical systems is the high complexity of the optimal receiver structures. The research emphasis in this thesis is on the design of a low complexity interference suppression/cancellation algorithm. The most important result of our research is the novel design of interference cancellation receivers which are adaptive and iterative and which are of low computational complexity. We propose various adaptive iterative receivers, based on a joint adaptive iterative detection and decoding algorithm. The proposed receiver can effectively suppress and cancel co-channel interference from the adjacent antennas in the MIMO system with a low computation complexity. The proposed adaptive detector, based on the adaptive least mean square (LMS) algorithm, is investigated and compared with the non-adaptive iterative receiver. Since the LMS algorithm has a slow convergence speed, a partially filtered gradient LMS (PFGLMS) algorithm, which has a faster convergence speed, is proposed to improve the convergence speed of the system. The performance and computational complexity of this receiver are also considered. To further reduce the computational complexity, we apply a frequency domain adaptation technique into the adaptive iterative receivers. The system performance and complexity are investigated. It shows that the computational complexity of the frequency domain based receiver is significantly lower than that of the time domain based receiver with the same system performance. We also consider applications of MIMO techniques in CDMA systems, called MIMO-CDMA. In the MIMO-CDMA, the presence of the co-channel interference (CCI) from the adjacent antennas and multiple access interference (MAI) from other users significantly degrades the system performance. We propose an adaptive iterative receiver, which provides the capability to effectively suppress the interference and cancel the CCI from the adjacent antennas and the MAI from other users so as to improve the system performance. The proposed receiver structure is also based on a joint adaptive detection and decoding scheme. The adaptive detection scheme employs an adaptive normalized LMS algorithm operating in the time and frequency domain. We have investigated and compared their system performance and complexity. Moreover, the system performance is evaluated by using a semi-analytical approach and compared with the simulation results. The results show that there is an excellent agreement between the two approaches.

Master of Engineering (Research) / The latest wireless communication techniques such as highspeed wireless internet application demand higher data rates and better quality of service (QoS). However, transmission reliability is still degraded by harsh propagation channels. Multiple-input multiple-output (MIMO) systems can increase the system capacity and improve transmission reliability. By transmitting multiple copies of data, a MIMO system can effectively combat the effects of fading. Due to the high hardware cost of a MIMO system, antenna selection techniques have been applied in MIMO system design to reduce the system complexity and cost. The Nakagami-m distribution has been considered for MIMO channel modeling since a wide range of fading channels, from severe to moderate, can be modeled by using Nakagami-m distribution. The Rayleigh distribution is a special case of the Nakagami-m distribution. In this thesis, we analyze the error performance of two MIMO schemes: maximal-ratio combining with transmit antenna selection (the TAS/MRC scheme) and space-time block codes with transmit antenna selection (the TAS/STBC scheme) over Nakagami-m fading channels. In the TAS/MRC scheme, one of multiple transmit antennas, which maximizes the total received signal-to-noise ratio (SNR), is selected for uncoded data transmission. First we use a moment generating function based (MGF-based) approach to derive the bit error rate (BER) expressions for binary phase shift keying (BPSK), the symbol error rate (SER) expressions for M-ray phase shift keying (MPSK) and M-ray quadrature amplitude modulation (MQAM) of the TAS/MRC scheme over Nakagami-m fading channels with arbitrary and integer fading parameters m. The asymptotic performance is also investigated. It is revealed that the asymptotic diversity order is equal to the product of the Nakagami fading parameter m, the number of transmit antenna Lt and the number of receive antenna Lr as if all transmit antenna were used. Then a Gaussian Q-functions approach is used to investigate the error performance of the TAS/STBC scheme over Nakagami-m fading channels. In the TAS/STBC scheme, two transmit antennas, which maximize the output SNR, are selected for transmission. The exact and asymptotic BER expressions for BPSK are obtained for the TAS/STBC schemes with three and four transmit antennas. It is shown that the TAS/STBC scheme can provide a full diversity order of mLtLr.

Multiple-Input Multiple-Output (MIMO) communications systems using multiantenna arrays simultaneously during transmission and reception have generated significant interest in recent years. Theoretical work in the mid 1990?s showed the potential for significant capacity increases in wireless channels via spatial multiplexing with sparse antenna arrays and rich scattering environments. However, in reality the capacity is significantly reduced when the antennas are placed close together, or the scattering environment is sparse, causing the signals received by different antennas to become correlated, corresponding to a reduction of the effective number of sub-channels between transmit and receive antennas. By introducing the previously ignored spatial aspects, namely the antenna array geometry and the scattering environment, into a novel channel model new bounds and fundamental limitations to MIMO capacity are derived for spatially constrained, or spatially selective, channels. A theoretically derived capacity saturation point is shown to exist for spatially selective MIMO channels, at which there is no capacity growth with increasing numbers of antennas. Furthermore, it is shown that this saturation point is dependent on the shape, size and orientation of the spatial volumes containing the antenna arrays along with the properties of the scattering environment. This result leads to the definition of an intrinsic capacity between separate spatial volumes in a continuous scattering environment, which is an upper limit to communication between the volumes that can not be increased with increasing numbers of antennas within. It is shown that there exists a fundamental limit to the information theoretic capacity between two continuous volumes in space, where using antenna arrays is simply one choice of implementation of a more general spatial signal processing underlying all wireless communication systems.

Thesis (Ph. D.)--Brigham Young University. Dept. of Electrical and Computer Engineering, 2006. / Includes bibliographical references (p. 97-101).

Thesis (Ph.D.)--McMaster University, 2006. / Supervisor: Timothy N. Davidson. Includes bibliographical references (p. 163-172).

Zugl.: Hamburg, Helmut-Schmidt-Univ., Diss., 2007

La demande sans cesse croissante pour des services sans fil de plus en plus gourmandes en ressources et l'évolution de l'état du marché des communications sans fil, obligent les futurs systèmes (4G) à obéir à des contraintes d'efficacités spectrales plus importantes et à fournir une meilleure qualité de service, particulièrement pour les utilisateurs se trouvant en bordure de cellules. Afin de répondre à ces objectifs, les nouveaux systèmes de communication devront incorporer des technologies qui leur permettent d'augmenter l'efficacité spectrale dans la cellule. Une des techniques des plus prometteuses permettant d'atteindre ces objectifs est le MIMO Coopératif dans les Réseaux Multi-cellulaires (Multicell-MIMO en anglais) qui est capable de diminuer l'interférence intercellulaire et d'augmenter le débit. Cette technique nécessite qu'un certain nombre de stations de base (BSs) se regroupent et traitent les signaux conjointement. Cependant, le Multicell-MIMO coopératif nécessite l'introduction de charges supplémentaires non négligeables sur le réseau afin de permettre le bon fonctionnement de cette technologie. Le but de cette thèse est d'étudier ces charges afin de trouver les mécanismes de les réduire avec des pertes acceptables de performances. Dans un premier temps, partant du fait que les charges introduites sur le réseau par le Multicell-MIMO coopératif sont proportionnelles au nombre de BSs qui coopèrent, nous sommes concentrés sur le regroupement d'un faible nombre d'entre eux. Nous proposons pour cela une coopération entre les BSs qui génèrent beaucoup d'interférences l'une pour l'autre, au lieu de considérer une coopération entre les stations de bases qui sont géographiquement proches l'une de l'autre. Cette approche nous a permis d'apporter des gains significatifs au niveau de l'efficacité spectrale. Par ailleurs, la conception centralisée classique pour le MIMO coopératif nécessite que les BSs appartenant à un même groupe soient interconnectées par une unité de contrôle centrale, leur permettant l'échange d'informations entre autres sur l'état du canal (CSI: Channel State Information en anglais). Cette architecture rend difficile le déploiement de cette technologie dans les réseaux de communications mobiles vu qu'elle nécessite des investissements supplémentaires pour le rajout de l'infrastructure additionnelle. Dans cette thèse, on propose une nouvelle approche mettant en œuvre une architecture décentralisée. Ceci nous assure la simplicité d'intégration du principe de la coopération Multi-cellulaire dans les systèmes cellulaires conventionnels à travers de minimes changements sur leur architecture. En outre, dans les systèmes de communication FDD (Frequency Division Duplexing en anglais) la connaissance du canal de transmission est cruciale afin d'assurer une bonne communication sur le lien descendant. Pour cela, les différents utilisateurs doivent réaliser une estimation du canal et la renvoyer sur une voie de retour. Nous proposons dans cette thèse une approche permettant de diminuer le trafic généré par le processus de retour du CSI en ne sélectionnant que les coefficients du canal ayant un gain supérieur à un niveau préfixé. On montre que la réduction de cette charge sur la voie de retour peut être combinée avec la réduction de la charge sur le backhaul (échange des donnés entre les BSs qui coopèrent). Une autre technique prometteuse, qui permet d'améliorer l'efficacité spectrale, est l'utilisation des relais. Les relais dynamiques (utilisateurs qui relaient des signaux destinés aux autres utilisateurs) sont plus rentables que les relais statiques, car ils n'exigent pas de déploiement de nouvelle infrastructure coûteuse. Cependant, leur utilisation ajoute des charges supplémentaires et des complexités importantes. Dans cette thèse l'efficacité des relais dynamiques est évaluée dans des environnements différents. De plus quelques techniques originales qui exploitent les relais dynamiques tout en exigeant des charges générales minimales sont présentées.