A method of controller design for multiple input multiple output (MIMO) system is needed that will not give the high order controllers of modern control theory but will be more systematic than the “ad hoc” method. The objective of this method of design for multiple input multiple output systems is to find a controller of fixed order with performance specifications taken into consideration. An inner approximation of the stabilizing set is found through the algorithm discussed in Keel and Bhattacharyya’s "Fixed order multivariable controller synthesis: A new algorithm." The set satisfying the performance is then approximated through one of two algorithms; a hybrid of two optimization algorithms or the grid algorithm found in Lampton’s "Reinforcement Learning of a Morphing Airfoil-Policy and Discrete Learning Analysis." The method is then applied to five models of four aircraft; Commander 700, X-29, X-38, and F-5A using controllers of first and second orders.

Orthogonal Frequency Division Multiple Access (OFDMA) uplink systems have been adopted generally in wireless communication in recent years. By combining Orthogonal Frequency Division Multiplexing (OFDM) with Frequency Division Multiple Access (FDMA), OFDMA systems divide all subcarriers in frequency domain into several mutually exclusive subbands, and assign the subbands to different user, transmitting different kinds of data by the orthogonality between subcarriers. The users¡¦ Carrier Frequency Offsets (CFO) caused by Doppler effects and/or misadjusted local oscillators may destroy the orthogonality between subcarriers, then lead to Multiple Access Interference (MAI) for all users, the MAI may degrade the performance of bit error rate. Several MAI suppression or cancellation schemes have been investigated to mitigate the effect of MAI, however, these schemes work on the hypothesis of known CFOs. As the result, it is the crucial issue for the multiuser CFOs estimation in OFDMA uplink systems. In this paper, we propose the Minimum Mean Square Error Criterion (MMSEC) estimation scheme to achieve multiuser CFOs estimation in Additive White Gaussian Noise (AWGN) environment. By modifying the MAI suppression weighting in [9], the MMSEC scheme search desired user¡¦s true CFO with CFO trial parameter, while the CFO trial parameter is equal to true CFO, the modified MAI suppression weighting will suppress the MAI ideally and then separate the desired user¡¦s estimated signal from received signal. Thus the distribution of estimated signal is highly concentrated in each of quadrant in the signal constellation, and it will have the minimum mean square error in each of quadrant. Compare with the MUtiple SIgnal Classification (MUSIC) scheme [12] and the Estimation of Signal Parameter via Rotational Invariance Technique (ESPRIT) scheme [13], they deal with the fully loaded problem by extending cyclic prefix, that may cause the redundant power consumption or degrade data throughput, the advantage of the MMSEC scheme is that it can works on fully load without extending cyclic prefix. Because despite fully loaded, the CFO trial parameter search desired user¡¦s true CFO in reasonable range until it causes minimum mean square error. The simulation result shows that the non-fully loaded system mean square error (MSE) performance is superior to the MUSIC and ESPRIT schees at high signal to noise ratio, while system is fully loaded, the system MSE performance is also acceptable.

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.

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.

Zweite Studienarbeit Hochschule für Angewandte Psychologie Zürich, 2006.

Zweite Studienarbeit Hochschule für Angewandte Psychologie Zürich, 2006.

Thesis (M.S.)--Ball State University, 2009. / Title from PDF t.p. (viewed on Apr. 16, 2010). Includes bibliographical references (p. 36-37).

Thesis (M.S.)--University of Wisconsin-Madison, 1992. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 55-63).