This work deals with the design of MT transmit, MR receive antenna MIMO (Multiple Input Multiple Output) communication system where the transmitter performs a linear operation on data. This linear precoding model includes systems which involve signal shaping for achieving higher data rates, uncoded MIMO Multicarrier and Single-Carrier systems and, the more recent, MIMO-OFDM (Orthogonal Frequency Division Multiplexing) systems employing full diversity Space-Frequency codes. The objective of this work is to design diversity centric and rate centric linear precoded MIMO systems whose performance is better than the existing designs. In particular, we consider MIMO-OFDM systems, Zero Padded MIMO systems and MIMO systems with limited rate feedback. Design of full diversity MIMO-OFDM systems of rate symbol per channel use (1 s/ pcu) : In literature, MIMO-OFDM systems exploiting full diversity at a rate of 1 s/ pcu are based on a few specific Space-Frequency (SF)/ Space-Time-Frequency (STF) codes. In this work, we devise a general parameterized framework for the design of MIMO-OFDM systems employing full diversity STF codes of rate 1 s/ pcu. This framework unifies all existing designs and provides tools for the design of new systems with interesting properties and superior performance. Apart from rate and diversity, the parameters of the framework are designed for a low complexity receiver. The parameters of the framework usually depend on the channel characteristics (number of multipath, Delay Profile (DP)). When channel characteristics are available at the transmitter, a procedure to optimize the performance of STF codes is provided. The resulting codes are termed as DP optimized codes. Designs obtained using the optimization are illustrated and their performance is shown to be better than the existing ones. To cater to the scenarios where channel characteristics are not available at the transmitter, a complete characterization of a class of full diversity DP Independent (DPI) STF codes is provided. These codes exploit full diversity on channels with a given number of multipath irrespective of their characteristics. Design of DP optimized STF codes and DPI codes from the same framework highlights the flexibility of the framework. Design of Zero Padded (ZP) MIMO systems : While the MIMO-OFDM transmitter needs to precode data for exploiting channel induced multipath diversity, ZP MIMO systems with ML receivers are shown to exploit multipath diversity without any precoding. However, the receiver complexity of such systems is enormous and hence a study ZP MIMO system with linear receivers is undertaken. Central to this study involves devising low complexity receivers and deriving the diversity gain of linear receivers. Reduced complexity receiver implementations are presented for two classes of precoding schemes. An upper bound on the diversity gain of linear receivers is evaluated for certain precoding schemes. For uncoded systems operating on a channel of length L, this bound is shown to be MRL_MT +1 for uncoded transmissions, i.e, such systems tend to exploit receiver and multipath diversities. On the other hand, MIMO-OFDM systems designed earlier have to trade diversity with receiver complexity. These observations motivate us to use ZP MIMO systems with linear receivers for channels with large delay spread when receiver complexity is at a premium. Design examples highlighting the attractiveness of ZP systems when employed on channels with large delay spread are also presented. Efficient design of MIMO systems with limited feedback : Literature presents a number of works that consider the design of MIMO systems with partial feedback. The works that consider feedback of complete CSI, however, do not provide for an efficient system design. In this work, we consider two schemes, Correlation matrix feedback and Channel information feedback that convey complete CSI to the transmitter. This CSI is perturbed due to various impairments. A perturbation analysis is carried out to study the variations in mutual information for each of the proposed schemes. For ergodic channels, this analysis is used to design a MIMO system with a limited rate feedback. Using a codebook based approach, vector quantizers are designed to minimize the loss in ergodic capacity for each of the proposed schemes. The efficiency of the design stems from the ability to obtain closed-form expression for centroids during the iterative vector quantizer design. The performance of designed vector quantizers compare favorably with the existing designs. The vector quantizer design for channel information feedback is robust in the sense that the same codebook can be used across all operating SNR. Use of vector quantizers for improving the outage performance is also presented.

In this thesis, we focus on interference cancelling (IC) detectors for advanced communication systems. The contents of this thesis is divided into the following four parts: 1. Multiuser interference (MUI) cancellation in uplink orthogonal frequency division multiple access (OFDMA). 2. Inter-carrier interference (ICI) and inter-symbol interference (ISI) cancellation in space-frequency block coded OFDM (SFBC-OFDM). 3. Single-symbol decodability (SSD) of distributed space-time block codes (DSTBC) in partially-coherent cooperative networks with amplify-and-forward protocol at the relays 4. Interference cancellation in cooperative SFBC-OFDM networks with amplify-and-forward (AF) and decode-and-forward (DF) protocols at the relays. In uplink OFDMA systems, MUI occurs due to different carrier frequency offsets of different users at the receiver. In the first part of the thesis, we present a weighted multistage linear parallel interference cancellation approach to mitigate the effect of this MUI in uplink OFDMA. We also present a minimum mean square error (MMSE) based approach to MUI cancellation in uplink OFDMA. We present a recursion to approach the MMSE solution and show structure-wise and performance-wise comparison with other detectors in the literature. Use of SFBC-OFDM signals is advantageous in high-mobility broadband wireless access, where the channel is highly time- as well as frequency-selective because of which the receiver experiences both ISI as well as ICI. In the second part of the thesis, we are concerned with the detection of SFBC-OFDM signals on time- and frequency-selective MIMO channels. Specifically, we propose and evaluate the performance of an interference cancelling receiver for SFBC-OFDM, which alleviates the effects of ISI and ICI in highly time- and frequency-selective channels The benefits of MIMO techniques can be made possible to user nodes having a single transmit antenna through cooperation among different nodes. In the third part of the thesis, we derive a new set of conditions for a distributed DSTBC to be SSD for a partially-coherent relay channel (PCRC), where the relays have only the phase information of the source-to-relay channels. We also establish several properties of SSD codes for PCRC. In the last part of the thesis, we consider cooperative SFBC-OFDM networks with AF and DF protocols at the relays. In cooperative SFBC-OFDM networks that employ DF protocol, i) ISI occurs at the destination due to violation of the `quasi-static' assumption because of the frequency selectivity of the relay-to-destination channels, and ii) ICI occurs due to imperfect carrier synchronization between the relay nodes and the destination, both of which result in error-floors in the bit error performance at the destination. We propose an interference cancellation algorithm for this system at the destination node, and show that the proposed algorithm effectively mitigates the ISI and ICI effects.

Fixed Broadband Wireless Access (FBWA) is a technology aimed at providing high-speed wireless Internet access, over a wide area, from devices such as personal computers and laptops. FBWA channels are defined in the range of 1-20 MHz which makes the RF front end (RFE) design extremely challenging. In its pursuit to standardize the Broadband Wireless Access (BWA) technologies, IEEE working group 802.16 for Broadband Wireless Access has released the fixed BWA standard IEEE 802.16 – 2004 in 2004. This standard is further backed by a consortium, of leading wireless vendors, chip manufacturers and service providers, officially known as Wireless Interoperability for Microwave Access (WiMAX). In general, any wireless base station (BS), supporting a number of contiguous Frequency Division Multiplexed (FDM) channels has to incorporate an RF front end (RFE) for each RF channel. The precise job of the RFE is to filter the desired channel from a group of RF channels, digitize it and present it to the subsequent baseband system at the proper sampling rate. The system essentially has a bandpass filter (BPF) tuned to the channel of interest followed by a multiplier which brings the channel to a suitable intermediate frequency (IF). The IF output is digitized by an ADC and then brought to the baseband by an appropriate digital multiplier. The baseband samples, thus generated, are at the ADC sampling rate which is significantly higher than the target sampling rate, which is defined by the wireless protocol in use. As a result a sampling rate conversion (SRC) is performed on these baseband samples to bring the channel back to the target sampling rate. Since the input sampling rate need not be an integer multiple of the target sampling rate, Fractional SRC (FSRC) is required in most of the cases. Instead of using a separate ADC and IF section for each individual channels, most systems use a common IF section, followed by a wideband ADC, which operates over a wide frequency band containing a group of contiguous FDM channels. In this case a channelizer is employed to digitally extract the individual channels from the digital IF samples. We formally call this system a receiver channelizer. Such an implementation presents considerable challenge in terms of the computational requirement and of course the cost of the BS. The computational complexity further goes up for FBWA system where channel bandwidth is in the order of several MHz. Though such a system has been analyzed for narrow band wireless systems like GSM, to the best of our knowledge no analysis seems to have been carried out for a wideband system such as WiMAX. In this work, we focus on design of a receiver channelizer for WiMAX BS, which can simultaneously extract a group of contiguous FDM RF channels supported by the BS. The main goal is to obtain a simple, low cost channelizer architecture, which can be implemented in an FPGA. There are a number of techniques available in the literature, from Direct Digital Conversion to Polyphase FFT Filter Banks (PFFB), which can do the job of channelization. But each of them operates with certain constraints and, as a result, suits best to a particular application. Further all of these techniques are generic in nature, in the sense that their structure is independent of any particular standard. With regard to computational requirement of these techniques, PFFB is the best, with respect to the number of complex multiplications required for its implementation. But it needs two very stringent conditions to be satisfied, viz. the number of channels to be extracted is equal to the decimation factor and the sampling rate is a power of 2 times baseband bandwidth. Clearly these conditions may not be satisfied by different wireless communication standards, and in fact, this is not satisfied by the WiMAX standard. This gives us the motivation to analyze the receiver channelizer for WiMAX BS and to find an efficient and low cost architecture of the same. We demonstrate that even though the conditions required by PFFB are not satisfied by the WiMAX standard, we can modify the overall architecture to include the PFFB structure. This is achieved by dividing the receiver channelizer into two blocks. The first block uses the PFFB structure to separate the desired number of channels from the input samples. This process also achieves an integer SRC by a factor that is equal to the number of channels being extracted. This block generates baseband outputs whose sampling rates are related to their target sampling rate by a fractional multiplication factor. In order to bring the channels to their target sampling rate, each output from the PFFB block is fed to a FSRC block, whose job is to use an efficient FSRC algorithm to generate the samples at the target sampling rate. We show that the computational complexity, as compared to the direct implementation, is reduced by a factor, which is approximately equal to the square of the number of channels. After mathematically formulating the receiver channelizer for WiMAX BS, we perform the simulation of the system using a software tool. There are two basic motives behind the simulation of the system which has a mathematical model. Firstly, the software simulation will give an idea whether the designed system is physically realizable. Secondly, this will help in designing the logic for different blocks of the system. Once these individual blocks are simulated and tested, they can be smoothly ported onto an FPGA. For simulation purpose, we parameterize the receiver channelizer in such a way that it can be reconfigured for different ADC sampling rates and IF frequencies, by changing the input clock rate. The system is also reconfigurable in terms of the supported channel bandwidth. This is achieved by storing all the filter coefficients pertaining to each channel type, and loading the required coefficients into the computational engine. Using this methodology we simulate the system for three different IF frequencies (and the corresponding ADC sampling rates) and three different channel types, thus leading to nine different system configurations. The simulation results are in agreement with the mathematical model of the system. Further, we also discuss some important implementation issues for the reconfigurable receiver channelizer. We estimate the memory requirement for implementing the system in an FPGA. The implementation delay is estimated in terms of number of samples. The thesis is organized in five chapters. Chapter 1 gives a brief introduction about the WiMAX system and different existing channelization architecture followed by the outline of the proposed receiver channelizer. In chapter 2, we analyze the proposed receiver channelizer for WiMAX BS and evaluate its computational requirements. Chapter 3 outlines the procedure to generate the WiMAX test signal and specification of the all the filters used in the system. It also lists the simulation parameters and records the results of the simulation. Chapter 4 presents the details of a possible FPGA implementation. We present the concluding remarks and future research directions in the final chapter.

Thesis submitted in fulfillment of the requirements for the degree Master of Technology:Electrical Engineering in the Faculty ofEngineering at the Cape Peninsula University of Technology Supervisor:Prof MTE KAHN Bellville December 2013 / The work presented in this thesis consists of the simulation of a cooling plant for a future mobile satellite ground station in order to minimize the effects of the thermal noise and to maintain comfort temperatures onboard the same station. Thermal problems encountered in mobile satellite ground stations are a source of poor quality signals and also of the premature destruction of the front end microwave amplifiers. In addition, they cause extreme discomfort to the mission operators aboard the mobile station especially in hot seasons. The main concerns of effective satellite system are the quality of the received signal and the lifespan of the front end low noise amplifier (LNA). Although the quality of the signal is affected by different sources of noise observed at various stages of a telecommunication system, thermal noise resulting from thermal agitation of electrons generated within the LNA is the predominant type. This thermal noise is the one that affects the sensitivity of the LNA and can lead to its destruction. Research indicated that this thermal noise can be minimized by using a suitable cooling system. A moveable truck was proposed as the equipment vehicle for a mobile ground station. In the process of the cooling system development, a detailed quantitative study on the effects of thermal noise on the LNA was conducted. To cool the LNA and the truck, a 2 kW solar electric vapor compression system was found the best for its compliance to the IEA standards: clean, human and environment friendly. The principal difficulty in the development of the cooling system was to design a photovoltaic topology that would ensure the solar panels were always exposed to the sun, regardless the situation of the truck. Simulation result suggested that a 3.3 kW three sided pyramid photovoltaic topology would be the most effective to supply the power to the cooling system. A battery system rated 48 V, 41.6 Ah was suggested to be charged by the PV system and then supply the power to the vapor compression system. The project was a success as the objective of this project has been met and the research questions were answered.

This International Workshop is a high quality seminar providing a forum for the exchange of scientific achievements between research communities of different universities and research institutes in the area of innovation information technologies. It is a continuation of the Russian-German Workshops that have been organized by the universities in Dresden, Karlsruhe and Ufa before. The workshop was arranged in 9 sessions covering the major topics: Modern Trends in Information Technology, Knowledge Based Systems and Semantic Modelling, Software Technology and High Performance Computing, Geo-Information Systems and Virtual Reality, System and Process Engineering, Process Control and Management and Corporate Information Systems.

<p dir="ltr">This work will introduce a channel conceptualization and possible coding scheme for Graph-and-Symbol (GS) Communication. While Claude Shannon’s mathematical model for communication employed graphs to describe relationships and confusability among traditional time-sequenced signals, little work as been done to describe non-linear communication <i>with</i> graphs where we transmit and receive physical structures of information. The principal contribution of this work is to introduce a mathematical framework for communication with graphs which have symbols assigned to vertices. This looks like a molecule, and so we may think of these messages as coded forms of molecular communication.</p><p dir="ltr">At this time, many problems in this area will (and may remain) computationally intractable, but as the field of graph theory continues to develop, new tools and techniques may emerge to solve standing problems in this new subfield of communication.</p><p dir="ltr">Graphs present two difficulties: first, they contain ambiguities among their vertices and do not have an <i>a priori</i> canonical ordering, and second, the relationships among graphs lack structural regularities which we see in traditional error control coding lattices. There are no Galois fields to exploit over graph-based codes as we have with cyclic codes, for example. Furthermore, the shear number of graphs of order n grows so rapidly that it is difficult to account for the neighborhoods around codewords and effectively reduce communication errors which may occur. The more asymmetric a graph is, the more orderings on symbols it can support. However, asymmetries complicate the computation of channel transition probabilities, which are the cornerstone of all communication theory.</p><p dir="ltr">In the prologue, the reader will be introduced to a new educational tool for designing traditional binary cyclic codes.</p><p dir="ltr">1 through 10 will detail the development of Graph-and-Symbol (GS) Commu- nication to date followed by two example codes which demonstrate the power of structuring information on graphs.</p><p dir="ltr">Chapter 13 onward will review the preliminary work in another area of research, disjoint from the main body. It is included here for posterity and special interests in applying graphs to solving other problems in signal processing. It begins with an introduction of spacetime raythic graphs. We propose a new chamfering paradigm for connecting neighboring pixels which approximates solutions to the eikonal equation. We show that some raythic graphs possess structures with multiple, differing solutions to eikonal wavefront propagation which are essential to the construction of the Umbral Transform. This umbral transform emulates ray casting effects, such as shadows and diffraction within an image space, from a network-flow algorithm.</p><p dir="ltr">This work may be duplicated in whole or in part for educational purposes only. All other rights of this work are reserved by the author, Timothy Arthur Terlep Jr., of Rose-Hulman Institute of Technology, Terre Haute, IN (effective August 2024), and subject to the rules and regulations of the Graduate School of Purdue University.</p><p dir="ltr">Readers may contact the author with any comments and questions at <b>taterlep@gmail.com</b></p>