Thesis (M.S. in Electrical Engineering)--Naval Postgraduate School, December 2008. / Thesis Advisor(s): Cristi, Roberto. "December 2008." Description based on title screen as viewed on January 30, 2009. Includes bibliographical references (p. 81-82). Also available in print.

Cette thèse présente une solution originale permettant d’extraire, à partir de signaux de communication OFDM, l’information liée à la différence de temps d’arrivée (TDOA) entre deux émetteurs très proches et un récepteur. Cette méthode, qui s’avère super-résolutive, permet d’extraire des TDOA en dessous de la limite de Rayleigh fixée par la bande passante utile. Dans ce travail, nous effectuons, à l'aide d'une sortie simple à entrées multiples, la caractérisation et la modélisation des canaux pour l’estimation TDOA. En gérant ces réponses ce canal de fréquence de canal de différentes manières, nous minimisons différentes fonctions de coût exprimées comme la différence entre la réponse de canal mesurée et un modèle direct prédéfini. Pour la validation, la simulation basée sur différentes topologies présente des résultats soulignant la propriété de super-résolution d'une telle approche. La performance de l’estimation TDOA proposée est comparée à la bande inférieure de Cramer-Rao. Les effets de la propagation par trajets multiples sont pris en compte et certaines solutions proposées sont discutées et simulées. De plus, la partie expérimentale de ce travail valide à la fois les modèles directs et inverses dans différentes configurations de canaux. / This thesis presents an original solution for extracting, from OFDM communication signals, the information related to the time difference of arrival (TDOA) between two closed transmitters and one receiver. This solution, which shows to be super-resolution, makes it possible to extract TDOA below the Rayleigh limit set by the useful bandwidth.Inthis work, we perform, using a Multiple Inputs Simple Output, channel characterization and modeling for TDOA estimation. By handling these channel frequency responses in different ways, xe minimize different cost functions expresses as the difference between measured channel response and a predefined direct model. For validation, the simulation based on different topologies exhibit results is compared to the Cramer Rao Lower Band. The effects of the multipath are taken into account and some proposed solutions are discussed ans simulated. Moreover, the experimental part of this work validates the direct and inverse models in different channel configurations.

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In this thesis, a maximum power point tracking (MPPT) for multiple input single output (MISO) converter is presented such that power generated from multiple individual energy sources can be combined to deliver the maximum amount of power to a common resistive load. Typically, MISO converters will employ techniques that yield equal current sharing from each energy source. However, this may not be desirable since each source may be rated at different power ratings and/or may experience different operating conditions, preventing the system MISO converter to acquire the most available total power from the sources. Utilizing MPPT control would therefore be beneficial in maximizing the output power of the MISO converter system. In this thesis, a proposed two-stage converter system is presented to incorporate the MPPT control in the MISO system. The initial stage implements the MPPT, drawing as much power from the corresponding source. The second stage regulates the output voltage of the MPPT. To evaluate the performance and efficiency of the proposed system, simulation with two solar panels as the sources was performed using Simulink with various test cases to fully explore the viability of the system. Simulation results were also used to compare with those obtained from a system without the MPPT. Results show that the proposed system with the MPPT stage is able to improve input regulation and increase the total amount of power acquired from the sources compared to the system without the MPPT. Further testing with hardware setup confirms the simulation results and demonstrates that even with large differences in input powers, the most total amount of power is achieved and utilized.

In this thesis, an approach is proposed for the design and implementation of a serial peripheral interface using Complex Programmable Logic Devices, (CPLD's). The focus of this research was to develop an effective Serial Peripheral Interface. The Serial Peripheral Interface, (SPI), created by Motorola is also known as Microwire, which is a trademark of National Semiconductor. The SPI is a full-duplex, synchronous, serial data link that enables communication between a host processor and peripherals. The Serial peripheral interface can be programmed in software or built strictly in hardware inside a microcontroller. However, Complex programmable logic devices offer a quicker and more customizable solution. This research investigated the Serial peripheral interface with respect to its implementation in a CPLD and the use of the Very High Speed Integrated Circuit Hardware Description language, (VHDL).

In recent years, ultra-wideband (UWB) communications has gained tremendous popularity in both research community and industry. The large bandwidth of UWB systems raises new wireless channel effects and consequently unique advantages as well as challenges to be dealt with, compared to conventional wireless systems. One of these advantages is the ability to resolve dense multipath components and use Rake combining at the receiver in order to significantly reduce the negative effects of fading. However, implementing a Rake receiver with a sufficiently large number of fingers to make use of this advantage is an evident challenge for most UWB devices with limited signal processing capabilities. A possible approach to overcome this problem is to move computational complexity from the receiver to the more powerful transmitter, which is the main focus of the present work. In this thesis, we propose two novel pre-equalization schemes for multiple- input single-output (MISO) direct-sequence ultra-wideband (DS-UWB) systems with pre-Rake combining and symbol-by-symbol detection. The first pre-equalization filter (PEF) scheme employs one PEF per transmit antenna, whereas in the second, simplified PEF (S-PEF) scheme all transmit antennas share the same PEF. For both schemes the optimum finite impulse response (FIR) and infinite impulse response (IIR) PEFs are calculated based on the minimum mean squared error (MMSE) criterion. We show that in contrast to previously proposed schemes for DS-UWB, both our proposed PEF schemes efficiently exploit the channel shortening properties of the pre-Rake filter. In particular, our proposed PEF schemes operate at the symbol level. We also show that under certain conditions the S-PEF scheme achieves the same performance as the more complex PEF scheme. Finally, we demonstrate that a single-input multiple-output (SIMO) DS-UWB system with post-Rake combining and MMSE post-equalization is the dual system to the considered MISO DS–UWB system with pre-Rake combining and MMSE pre-equalization. This uplink-downlink duality can be exploited for efficient calculation of the PEFs and for complexity reduction. Our simulation results show that the proposed PEF schemes achieve significant performance gains over pre-Rake combining without equalization even if only short PEFs are employed, and this is the case even for long UWB channel impulse responses.

In this thesis, the problem of quantifying the Pareto optimal boundary of the achievable rate region is considered over multiple-input single-output(MISO)interference channels, where the problem boils down to solving a sequence of convex feasibility problems after certain transformations. The feasibility problem is solved by two new distributed optimal beam forming algorithms, where the first one is to parallelize the computation based on the method of alternating projections, and the second one is to localize the computation based on the method of cyclic projections. Convergence proofs are established for both algorithms.

I detta examensarbete undersöks möjligheten att kunna använda en positioneringsmetod som inte enbart förlitar sig på den uppmätta signalstyrkan. Istället används en metod som bestämmer från vilken vinkel en signal uppkommer ifrån. Den här tekniken kallas för direction-finding. När informationen om signalens vinkel fastställts används den i ett positioningsfilter som uppskattar positionen. Två tillvägagångssätt har använts i den här rapporten, ett där enbart vinkeln används och ett där både signalstyrka och vinkel används.

In recent years, ultra-wideband (UWB) communications has gained tremendous popularity in both research community and industry. The large bandwidth of UWB systems raises new wireless channel effects and consequently unique advantages as well as challenges to be dealt with, compared to conventional wireless systems. One of these advantages is the ability to resolve dense multipath components and use Rake combining at the receiver in order to significantly reduce the negative effects of fading. However, implementing a Rake receiver with a sufficiently large number of fingers to make use of this advantage is an evident challenge for most UWB devices with limited signal processing capabilities. A possible approach to overcome this problem is to move computational complexity from the receiver to the more powerful transmitter, which is the main focus of the present work. In this thesis, we propose two novel pre-equalization schemes for multiple- input single-output (MISO) direct-sequence ultra-wideband (DS-UWB) systems with pre-Rake combining and symbol-by-symbol detection. The first pre-equalization filter (PEF) scheme employs one PEF per transmit antenna, whereas in the second, simplified PEF (S-PEF) scheme all transmit antennas share the same PEF. For both schemes the optimum finite impulse response (FIR) and infinite impulse response (IIR) PEFs are calculated based on the minimum mean squared error (MMSE) criterion. We show that in contrast to previously proposed schemes for DS-UWB, both our proposed PEF schemes efficiently exploit the channel shortening properties of the pre-Rake filter. In particular, our proposed PEF schemes operate at the symbol level. We also show that under certain conditions the S-PEF scheme achieves the same performance as the more complex PEF scheme. Finally, we demonstrate that a single-input multiple-output (SIMO) DS-UWB system with post-Rake combining and MMSE post-equalization is the dual system to the considered MISO DS–UWB system with pre-Rake combining and MMSE pre-equalization. This uplink-downlink duality can be exploited for efficient calculation of the PEFs and for complexity reduction. Our simulation results show that the proposed PEF schemes achieve significant performance gains over pre-Rake combining without equalization even if only short PEFs are employed, and this is the case even for long UWB channel impulse responses.

Η έρευνα στις ασύρματες τηλεπικοινωνίες κινείται προς την κατεύθυνση της επίτευξης υψηλής κινητικότητας και ταυτόχρονα προς τη μεγιστοποίηση των δυνατοτήτων του ραδιοδιαύλου, όσον αφορά τη χωρητικότητα της γραμμής και την ταυτόχρονη εξυπηρέτηση μεγάλου αριθμού χρηστών. Στόχος είναι η υποστήριξη IMT-Advanced (4G) ταχυτήτων της τάξης των 100 Μbps στην κάτω ζεύξη και 50 Μbps στη άνω με τη μέση φασματική απόδοση να είναι 3 με 4 φορές καλύτερη από την αντίστοιχη του HSPA. Για να επιτευχθούν τόσο οι υψηλές ταχύτητες όσο και η φασματική αποδοτικότητα σε συνδυασμό με την καλή κινητικότητα, πρέπει όπως δείχνει η έρευνα σήμερα, στο φυσικό στρώμα μετάδοσης να εφαρμοστούν τεχνικές OFDMA (Orthogonal Frequency Division Multiple Access - Πολλαπλή Πρόσβαση με Ορθογωνική Διαίρεση Συχνότητας) σε MIMO ή MISO συστήματα, όπως αντίστοιχα συμβαίνει στο WiMAX. Για αυτόν το λόγο στην παρούσα διπλωματική προτείνονται 3 αλγόριθμοι κατανομής των ραδιοπόρων για την κάτερχόμενη ζεύξη των MISO OFDMA. Οι δυο πρώτοι αλγόριθμοι σκοπεύουν τη μεγιστοποίηση του συνολικού ρυθμού μετάδοσης δεδομένων των χρηστών κάτω από τους περιορισμούς στη συνολική διαθέσιμη ισχύ του σταθμού βάσης και την αναλογική δικαιοσύνη μεταξύ των ρυθμών μεταδόσεως δεδομένων των χρηστών. Ο τρίτος αλγόριθμος αντί για τον περιορισμό της αναλογικής δικαιοσύνης εφαρμόζει τον περιορισμό στον ελάχιστο ρυθμό μετάδοσης των δεδομένων κάθε χρήστη. Οι προτεινόμενοι αλγόριθμοι βασίζονται στο σχηματισμό δέσμης ZF ενώ στο δεύτερο αλγόριθμο χρησιμοποιείται και η χωρική συσχέτιση. Παρ’όλο που και οι τρεις αλγόριθμοι είναι υποβέλτιστοι, η απώλεια σε συνολικό ρυθμό μετάδοσης δεδομένων είναι λογική εφόσον πρωταρχικός σκοπός αποτελεί η εξασφάλιση της δικαιοσύνης. Και οι τρεις προτεινόμενοι αλγόριθμοι εν τέλει παρουσιάζουν ικανοποιητική πολυπλοκότητα ώστε η υλοποίηση να είναι δυνατή με χαμηλό κόστος επεξεργασίας. Μπορούν λοιπόν κάλλιστα οι αλγόριθμοι που μελετήθηκαν να χρησιμοποιηθούν στα σύγχρονα ασύρματα συστήματα όπως το πρότυπο WiMAX. Οι προτεινόμενοι αλγόριθμοι εξομοιώθηκαν χρησιμοποιώντας το λογισμικό MATLAB®. Πιο συγκεκριμένα το κεφάλαιο ένα αποτελεί την εισαγωγή της διπλωματικής εργασίας. Αναφέρεται στο σκοπό της όσο και στις μεθόδους που χρησιμοποιήθηκαν για την επίτευξή του. Στο κεφάλαιο δύο γίνεται αναφορά στα ασύρματα συστήματα πολλαπλής πρόσβασης, τα οποία διαχωρίζονται σε σταθερά και κινητά συστήματα επικοινωνιών. Περιγράφονται συστήματα όπως τa 3G και Wi-Fi ενώ στη συνέχεια γίνεται ιστορική αναφορά στην εξέλιξη του WiMAX και μια μικρή παρουσίασή του. Τέλος, γίνεται μια μικρή αναφορά στον ασύρματο ευρυζωνικό δίαυλο. Στο κεφάλαιο τρία παρουσιάζονται θεωρητικά στοιχεία για τα OFDM και OFDMA και παρουσιάζονται οι μαθηματικές εκφράσεις του προβλήματος διαχείρισης των ραδιοπόρων σε αυτά. Επιπλέον, γίνεται αναφορά στους αλγόριθμους διαχείρισης ραδιοπόρων και μια εισαγωγή στο μαθηματικό μοντέλο που χρησιμοποιήθηκε. Το κεφάλαιο τέσσερα περιέχει εκτενή αναφορά στα ασύρματα κανάλια και ιδιαίτερα στα MIMO και στη χωρητικότητά τους. Το κεφάλαιο πέντε περιλαμβάνει τους αλγόριθμους που προτάθηκαν και μελετήθηκαν και ολοκληρώνεται με τα συμπεράσματα από τη διαδικασία εξομοίωσης. Στο κεφάλαιο έξι περιλαμβάνονται τα επιμέρους συμπεράσματα που έχουν εξαχθεί από κάθε κεφάλαιο. / Present research in wireless telecommunications is targeted on achieving high mobility and maximizing the potentials of the radio bus in the same time, concerning line’s capacity and simultaneusly serving a major number of users. The aim is supporting IMT-Advanced (4G) speeds; 100 Μbps download and 50 Μbps upload, with an average spectrum performance three to four times better than HSPA’s. In order to achieve such high speeds, as well as spectrum efficiency, in combination with a fair mobility, it is almost essential as shown in present global research, to apply OFDMA (Orthogonal Frequency Division Multiple Access) technics in the physical layer of MIMO or MISO systems, as applied in WiMAX. Thus, in this dissertation, three algorithms for the radio resource allocation problem of the downlink of MISO-OFDMA are proposed. The first two algorithms are aiming at maximizing the sum user’s data rate under restrictions in total available base station’s power and proportional fairness data rate constraints among users. The third algorithm applies constraints of the minimum data rate of each user instead of proportional rate constraints. The proposed algorithms are based on forming a ZF beam, while in the second algorithm space correlation is used. Although all three algorithms are suboptimal, the loss in total data rate is reasonable, since the primary target is maintaining fair justice among users. All three proposed algorithms have fairly low complexity so they could be applied easily with low calculation cost. Therefore, the investigated algorithms could be applied in modern wireless systems such as WiMAX. These algorithms are assessed by simulation using MATLAB® software. Specifically, chapter one includes the introduction of this dissertation. It is referred to its purpose as well as to the methods applied in. In chapter two there is a brief description in modern wireless telecommunication systems. Systems like 3G and Wi-Fi are presented along with a brief history of WiMAX and its characteristics. In the end of this chapter problems concerning wireless broadband bus are presented. In chapter three theoretical elements on OFDM and OFDMA are analysed along with the mathematical expression of the radio resource allocation problem in OFDMA. Moreover an introduction of a mathematical model is included. Chapter four focuses on detail on the mathematical description of the MIMO-MISO line capacity. In chapter five the three proposed algorithms on the downlink of MISO - OFDMA are presented. It concludes with the simulation results accompanied with some comments and conclusions. In chapter six all the conclusions of this dissertation, chapter by chapter are included in brief.