<p>In the high-end research process of wireless systems and in the race for the development of the new technologies, MIMO (Multiple Input, Multiple Output) is getting more attention now days. It has a high potential usage in the 3G and 4G communications and beyond. The MIMO based system has got the ability to increase the data throughput in spectrum-limited conditions. With the increase and complexity of wireless applications, the spectrum efficiency improvement in the physical layer will be saturated. MIMO is predicted to be one of the major features for the next generation wireless networking. This thesis work is a part of an ongoing project of the Generic MIMO decoder design carried out at the research laboratory, LESTER at Lorient, France. I was involved in the study of MIMO concepts, orthogonal and Space-time codes and later involved in the design and optimization of the architecture for the core operator for the ML decoder used in the reception of the MIMO system,which is presented in this report work.</p>

Thesis (M.Sc.)--York University, 2008. Graduate Programme in Computer Science. / Typescript. Includes bibliographical references (leaves 75-77). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:MR45953

Thesis (M.Sc.)--York University, 2008. Graduate Programme in Computer Science and Engineering. / Typescript. Includes bibliographical references (leaves 80-85). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:MR38816

This paper considers the combination of interference alignment and distributed antenna systems to improve the rate performance of cell-edge users in the cellular downlink. Because the power resources of each antenna in distributed antenna systems are geographically separated, practical implementations of distributed antenna systems require consideration of per-antenna power constraints on the transmit antennas. For this reason, we consider interference alignment with two types of power constraints: per-antenna power inequality constraints and per-antenna power equality constraints. On one hand, we show that interference alignment with per-antenna power inequality constraints is arbitrarily feasible using a technique of antenna power back-off but suffers from a loss of performance that we quantify in the case of Rayleigh-fading. On the other hand, we show that interference alignment with per-antenna power equality constraints does not suffer from a systematic loss of performance but yet requires more antennas to be feasible. We develop algorithms for implementing interference alignment with both types of constraints and numerically validate the results of our analysis. Finally, we demonstrate using the 3rd Generation Partnership Project spatial channel model in a cellular setting that interference alignment with distributed antenna systems has better rate performance than interference alignment with centralized antenna systems throughout the entire cell, especially near the cell boundary. / text

The objective of this thesis is to determine a method for computing the amount of capacitance in a power electronic converter required to melt a fuse in the event of a line to ground fault. DC micro-grids rely on power electronic converters to change voltage levels. All converters rely on semiconductor switches that must be protected from surges of fault current. This limits the power that a converter can supply to a fuse. In many cases, sufficient power may be achieved by appropriately sizing the converters’ output capacitor. / text

This thesis evaluates the benefits of Multiple Input Multiple Output (MIMO) techniques on the capacity of Multimode Fiber (MMF) links. Optical MMF MIMO systems take advantage of the spatial diversity present in the multiple propagating paths in multimode fibers. By using multiple lasers at the input facet of the fiber and multiple photodetectors at the output, we show that the capacity of the link is improved from the single device link, hence demonstrating the usefulness of MIMO in such optical systems. An initial simulation of butt-coupling a Vertical Cavity Surface Emitting Laser (VCSEL) to multimode fiber reveals that the placement position of the laser axis with respect to the fiber axis is critical in exciting a large number of modes. More specifically, we show that there exists a tradeoff between total power coupled into the fiber and the number of modes launched. We then consider a mathematical description of the fiber channel and use it to simulate the capacity of a 1x1, 2x2, and 3x3 MIMO links over a statistical ensemble of channel realizations. This simulation reveals that a 2x2 system is capable of approximately a 50% increase in capacity over the 1x1 case while the 3x3 system is capable of approximately an 80% increase. Moreover, we show that the choice of the placement positions on the facets of the fiber affects the channel capacity, thereby implying that an optimal device position exists. We find the optimal device geometry by an exhaustive search and compare the capacities for the optimal geometry and that of a suboptimal one. A capacity tolerance study is then developed that considers perturbations about the optimal device locations and shows that the capacity of a rotated laser plane is over 90% of the capacity of the original device locations. A second perturbation study considers lateral offsets and shows that systems with a higher number of devices show good tolerance with poorer lateral tolerances for systems with less devices. When small lasers and a large grid of possible device locations are used, an exhaustive search for the optimal device location becomes computationally infeasible. We show that the problem of searching for the optimal detector locations while holding the laser positions fixed is submodular. This property allows a greedy algorithm to select the device positions at a small fraction of the computational complexity, however, only guaranteeing that the capacity of the resulting configuration is greater than a (1 - e^-1) fraction of the optimal configuration. We use this technique to compare the exhaustive search and the greedy search for coarse grids, and then exclusively use the greedy algorithm to select a device configuration for a fine grid whereby an exhaustive search is computationally infeasible. / text

This paper presents the investigations into the performance of a multiple-input multiple-output (MIMO) system with its transmitters on a spinning vehicle and no available channel state information (CSI) at the transmitter or the receiver. The linear least squares approach is used to estimate the channel and the estimation error is measured. Spinning gives rise to a periodic component in the channel which can be estimated based on the spin rate relative to the data rate of the system. It is also determined that spinning causes the bit error rate of the system to degrade by a few dB.

In this paper, an idea of using space-time block coding (STBC) in multi-user cooperative diversity has been exploited to improve the performance of the transmission in wireless local area networks. The theoretical and simulation results show that, using STBC approaches can always achieve the better performance than existing techniques without introducing the space-time coding. By analyzing the throughput and frame error ratio (FER) of the two different STBC cooperative schemes, we find the trade-off between throughput and reliability. The location of the relay is crucial to the performance, which supposes a rule for future crosslayer design.

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