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Approved for public release; distribution is unlimited. / Wireless communication is employed to connect mobile computers in a networked environment for information exchange. In a tactical space, sensors and computers typically need to operate on-the-move while transmitting data over both short and long distances in different terrain and conditions. The wireless communication is thus susceptible to effects of Doppler shift and channel fading. In addition, when security and anti jamming features are required, such as frequency-hopping techniques, then coherent signal detection is difficult and noncoherent modulation is used instead. Our study will focus on the bit error rate (BER) performance analysis of noncoherent orthogonal modulation, specifically M-ary frequency-shift keying (MFSK) and code-shift keying (CSK) modulation, in both additive white Gaussian noise (AWGN) and for a Rayleigh fading channel with Doppler shift. The potential applications include communications between mobile computer-sensor devices, such as a mobile ground control station maintaining a datalink with UAV. / Civilian

We propose a new approach to proving results regarding channel coding schemes based on construction-A lattices for the Additive White Gaussian Noise (AWGN) channel that yields new characterizations of the code construction parameters, i.e., the primes and dimensions of the codes, as functions of the block-length. The approach we take introduces an averaging argument that explicitly involves the considered parameters. This averaging argument is applied to a generalized Loeliger ensemble [1] to provide a more practical proof of the existence of AWGN-good lattices, and to characterize suitable parameters for the lattice Gaussian coding scheme proposed by Ling and Belfiore [3].

Στην παρούσα διπλωματική εργασία επιχειρείται η ανάλυση και η εκτίμηση της συχνότητας απλών ημιτονοειδών σημάτων υπό την παρουσία λευκού Γκαουσιανού θορύβου (AWGN).Η εκτίμηση παραμέτρων απλών ημιτονοειδών σημάτων υπό την παρουσία προσθετικού Γκαουσιανού θορύβου αποτελεί ένα κλασσικό πρόβλημα και σημαντικό αντικείμενο μελέτης εξαιτίας της πληθώρας των εφαρμογών που έχει στην θεωρία ελέγχου, στην επεξεργασία σημάτων, στις ψηφιακές επικοινωνίες, στην βιοϊατρική τεχνολογία κ.α.Η εκτίμηση της συχνότητας είναι συνήθως το θέμα ‘ζωτικής σημασίας’ του προβλήματος για δύο σημαντικούς λόγους. Αφ’ενός οι συχνότητες πρέπει να εκτιμηθούν διότι αποτελούν μη-γραμμικές συναρτήσεις στην ληφθείσα ακολουθία δεδομένων και αφ’ ετέρου έχοντας καθοριστεί οι συχνότητες, οι υπόλοιπες παράμετροι του σήματος όπως είναι το πλάτος και η φάση του, μπορούν να υπολογιστούν άμεσα. Αρχικά γίνεται μία σύντομη εισαγωγή στις βασικές έννοιες πάνω στις οποίες δομείται η εκτίμηση παραμέτρων ενός ημιτονοειδούς σήματος και έπειτα παρουσιάζονται μερικοί αλγόριθμοι εκτίμησης. Πιο συγκεκριμένα παρουσιάζεται η διαδικασία κατασκευής τους και αναλύονται οι επιδόσεις τους. Τέλος παραθέτουμε και προσομοιώσεις μέσω υπολογιστή για κάθε αλγόριθμο ξεχωριστά και συγκρίνουμε την επίδοση του καθενός με τους υπόλοιπους. Από την σύγκριση αυτή γίνεται εξαγωγή χρήσιμων συμπερασμάτων σχετικά με τον προσδιορισμό των παραμέτρων κάθε αλγόριθμου αλλά και με την καταλληλότητα κάθε αλγόριθμου για συγκεκριμένες συνθήκες θορύβου. / In this thesis attempts to analyze and estimate the frequency of single sinusoid signals in Additive White Gaussian Noise (AWGN). Parameter estimation of sinusoids has been a classical problem and it is still an important research topic because of its numerous applications in multiple disciplines such as control theory, signal processing, digital communications, biomedical engineering etc. Estimation of the frequencies is often the crucial step in the problem for two principally reasons. Firstly, frequencies should be estimated because they are nonlinear functions in the received data sequence and secondly, once frequencies have been determined, the remaining parameters, such as amplitude and phase, can then be computed straightforwardly. Primarily we introduce some basic concepts on parameters estimation of sinusoid signals and then several estimation algorithms. More specifically shows the fabrication process of these algorithms and analyze their performance. Finally, we quote computer simulations for each algorithm separately and compare their performance. From these comparisons we can draw conclusions on the determination of parameters for each algorithm and the appropriateness of algorithms for specific noise conditions.

This master thesis investigates the jamming of Tactical Data Links (TDLs). The goal is to make a model that is capable of giving an overview of a communication system under jamming conditions, offering the user a suggestion for the best coding scheme and modulation to use in any given situation. Investigation is primarily focused on the High Frequency (HF) band and its accompanying Beyond Line Of Sight (BLOS) capabilities. With this model, time and resources can be saved by eliminating the need to test for these parameters. After this model is made, based on information found on jamming types, the question is asked whether Additive White Gaussian Noise (AWGN) jamming can be approximated in a simpler way, specifically by looking at the results of an un-jammed system with a higher noise floor. Results show that for fast switching pulsed jammers this is possible, but there is a dependency on the modulation used. For slow switching jammers, this is not possible. The model presented can later be used as a basis to answer more operational questions. / Denna mastersarbete undersöker störningen av Tactical Data Links (TDL). Målet är att göra en modell som kan ge en överblick över ett kommunikationssystem under störningsförhållanden, och erbjuda användaren ett förslag på det bästa kodningsschemat och moduleringen att använda i en given situation. Undersökningen är främst inriktad på High Frequency (HF)-bandet och dess medföljande Beyond Line Of Sight (BLOS)-funktioner. Med denna modell kan tid och resurser sparas genom att eliminera behovet av att testa för dessa parametrar. Efter att denna modell har gjorts, baserat på information som hittats om störningstyper, ställs frågan om Additive White Gaussian Noise (AWGN) störning kan approximeras på ett enklare sätt, specifikt genom att titta på resultaten av ett system som har ett högre brusgolv. Resultaten visar att detta är möjligt för snabbväxlande pulsade störsändare, men det finns ett beroende av den modulering som används. För långsamt växlande störsändare är detta inte möjligt. Den presenterade modellen kan senare användas som underlag för att svara på mer operativa frågor / Dit afstudeerverslag doet onderzoek naar het verstoren van Tactische Data Links (TDLs). Het doel is om een model te maken dat een overzicht geeft van een communicatiesysteem dat verstoord wordt, en vervolgens de gebruiker een suggestie doet over de beste combinatie voor codering en modulatie. Er wordt vooral gekeken naar communicatie in de HF band, die wordt gekenmerkt door zijn Beyond Line Of Sight (BLOS) capaciteiten. Met dit model worden tijd en andere middelen bespaard door het overbodig maken van testen op de juiste parameters. Met dit model, waarin relevante verstoringstechnieken zijn meegenomen, wordt de vraag gesteld of het mogelijk is om AWGN-verstoring op een simpelere manier te benaderen, namelijk door het te vergelijken met een systeem met een hogere ruis vloer. Uit de resultaten blijkt dat dit wel mogelijk is voor snel schakelende gepulseerde stoorzenders, maar dat er wel rekening gehouden moet worden met het type modulatie. Voor langzaam schakelende gepulseerde stoorzenders is dit niet mogelijk. Het model wat in dit verslag gepresenteerd wordt, kan gebruikt worden als basis voor het beantwoorden van operationele vraagstukken.

MIMO systems are mainly used in application for wireless communication. Their principle is to use a large number of antennas for transmition and the reception of a signal. The core of these systems is to use space-time coding and either block or trellis space-time code. In the future, it is assumed enormous enlargement MIMO systems in many applications

International Telemetering Conference Proceedings / October 23-26, 2000 / Town & Country Hotel and Conference Center, San Diego, California / The Bit Error Rate (BER) performance of FQPSK modulated signals in the presence of the Co-Channel Interference (CCI) and Additive White Gaussian Noise (AWGN) is evaluated and improved. A Non- Linearly Amplified (NLA) FQPSK modulated signal with the data rate of 1Mb/s and carrier frequency of 70 MHz is interfered with a sinusoidal signal at different frequencies. As the relative distance of the center frequency of the Co-channel interference (CCI) changes, different BER are obtained. The effect of the CCI decreases as the CCI center frequency moves away from the center of the modulated signal. In order to improve the BER in the presence of the CCI, a hard limited filter is added at the receiver input. The hard limited filter has a different amplification factor for different signal strength. As a result, the amplification factor for the CCI, which is normally a weaker signal, is smaller than the actual signal. This means that the signal is amplified more than the interference and as a result the CCI is suppressed and the BER rate improves. The results of both simulations and measurements are obtained for different CCI center frequencies, before and after the improvements.

In this work wireless communication systems with multiple co-channel signals present at the receiver are considered. One of the major challenges in the development of such systems is the computational complexity required for the detection of the transmitted signals. This thesis addresses this problem and develops reduced complexity algorithms for the detection of multiple co-channel signals in receivers with multiple antennas. The signals are transmitted from either a single user employing multiple transmit antennas, from multiple users or in the most general case by a mixture of the two. The receiver is assumed to be overloaded in that the number of transmitted signals exceeds the number of receive antennas. Joint Maximum Likelihood (JML) is the optimum detection algorithm which has exponential complexity in the number of signals. As a result, detection of the signals of interest at the receiver is challenging and infeasible in most practical systems. The thesis presents a framework for the detection of multiple co-channel signals in overloaded receivers. It proposes receiver structures and two list-based signal detection algorithms that allow for complexity reduction compared to the optimum detector while being able to maintain near optimum performance. Complexity savings are achieved by first employing a linear preprocessor at the receiver to reduce the effect of Co-Channel Interference (CCI) and second, by using a detection algorithm that searches only over a subspace of the transmitted symbols. Both algorithms use iterative processing to extract ordered lists of the most likely transmit symbols. Soft information can be obtained from the detector output list and can then be used by error control decoders. The first algorithm named Parallel Detection with Interference Estimation (PD-IE) considers the Additive White Gaussian Noise (AWGN) channel. It relies on a spatially reduced search over subsets of the transmitted symbols in combination with CCI estimation. Computational complexity under overload is lower than that of JML. Performance results show that PD-IE achieves near optimum performance in receivers with Uniform Circular Array (UCA) and Uniform Linear Array (ULA) antenna geometries. The second algorithm is referred to as List Group Search (LGS) detection. It is applied to overloaded receivers that operate in frequency-flat multipath fading channels. The List Group Search (LGS) detection algorithm forms multiple groups of the transmitted symbols over which an exhaustive search is performed. Simulation results show that LGS detection provides good complexity-performance tradeoffs under overload. A union bound for group-wise and list-based group-wise symbol detectors is also derived. It provides an approximation to the error performance of such detectors without the need for simulation. Moreover, the bound can be used to determine some detection parameters and tradeoffs. Results show that the bound is tight in the high Signal to Interference and Noise Ratio (SINR) region.

The concept of cable television, originally called community antenna television (CATV), began in the 1940's. The information and services provided by cable operators have changed drastically since the early days. Cable service providers are no longer simply providing their customers with broadcast television but are providing a multi-purpose, two-way link to the digital world. Custom programming, telephone service, radio, and high-speed internet access are just a few of the services offered by cable service providers in the 21st century. At the dawn of the internet the dominant mode of access was through telephone lines. Despite advances in dial-up modem technology, the telephone system was unable to keep pace with the demand for data throughput. In the late 1990's an industry consortium known as Cable Television Laboratories, Inc. developed a standard protocol for providing high-speed internet access through the existing CATV infrastructure. This protocol is known as Data Over Cable Service Interface Specification (DOCSIS) and it helped to usher in the era of the information superhighway. CATV systems use different parts of the radio frequency (RF) spectrum for communication to and from the user. The downstream portion (data destined for the user) consumes the bulk of the spectrum and is located at relatively high frequencies. The upstream portion (data destined to the network from the user) of the spectrum is smaller and located at the low end of the spectrum. This lower frequency region of the RF spectrum is particularly prone to impairments such as micro-reflections, which can be viewed as a type of multipath interference. Upstream data transfer in the presence of these impairments is therefore problematic and requires complex signal correction algorithms to be employed in the receiver. The quality of a receiver is largely determined by how well it mitigates the signal impairments introduced by the channel. For this reason, engineers developing a receiver require a piece of equipment that can emulate the channel impairments in any permutation in order to test their receiver. The conventional test methodology uses a hardware RF channel emulator connected between the transmitter and the receiver under test. This method not only requires an expensive RF channel emulator, but a functioning analog front-end as well. Of these two problems, the expense of the hardware emulator is likely less important than the delay in development caused by waiting for a functional analog front-end. Receiver design is an iterative, time consuming process that requires the receiver's digital signal processing (DSP) algorithms be tested as early as possible to reduce the time-to-market. This thesis presents a digital implementation of a DOCSIS-compliant channel emulator whereby cable micro-reflections and thermal noise at the analog front-end of the receiver are modelled digitally at baseband. The channel emulator and the modulator are integrated into a single hardware structure to produce a compact circuit that, during receiver testing, resides inside the same field programmable gate array (FPGA) as the receiver. This approach removes the dependence on the analog front-end allowing it to be developed concurrently with the receiver's DSP circuits, thus reducing the time-to-market. The approach taken in this thesis produces a fully programmable channel emulator that can be loaded onto FPGAs as needed by engineers working independently on different receiver designs. The channel emulator uses 3 independent data streams to produce a 3-channel signal, whereby a main channel with micro-reflections is flanked on either side by adjacent channels. Thermal noise normally generated by the receiver's analog front-end is emulated and injected into the signal. The resulting structure utilizes 43 dedicated multipliers and 401.125 KB of RAM, and achieves a modulation error ratio (MER) of 55.29 dB.

En esta tesis doctoral se han diseñado arquitecturas hardware de algunos subsistemas digitales característicos de los sistemas de comunicaciones de elevadas prestaciones, buscando implementaciones optimizadas para dichos sistemas. El trabajo realizado se ha centrado en dos áreas: la aproximación de funciones elementales, concretamente el logaritmo y la arcotangente, y el diseño de un emulador de canal de ruido Gaussiano aditivo. Las arquitecturas se han diseñado en todo momento teniendo como objetivo lograr una implementación eficiente en dispositivos Field Programmable Gate Arrays (FPGAs), debido a su uso creciente en los sistemas de comunicaciones digitales de elevadas prestaciones. Para la aproximación del logaritmo hemos propuesto dos arquitecturas, una basada en la utilización de tablas multipartidas y la otra basada en el método de Mitchell sobre el que añadimos dos etapas de corrección: una interpolación lineal por rectas con pendientes potencias de dos y mantisa truncada, y una tabla para la compensación del error cometido en la interpolación por rectas. Una primera arquitectura para la aproximación de la atan(y/x) está basada en el cómputo del recíproco de x y en el cálculo de la arcotangente, utilizando básicamente tablas Look-up (LUT) multipartidas. Esta propuesta ya permite reducir el consumo de potencia con respecto a las mejores técnicas recogidas en la bibliografía, como las basadas en CORDIC. Una segunda estrategia para la aproximación de la atan(y/x) está basada en transformaciones logarítmicas, que convierten el cálculo de la división de las dos entradas en una sencilla resta y que hacen necesario el cómputo de atan(2w). Esta segunda estrategia se ha materializado en dos arquitecturas, una primera en la que tanto el logaritmo como el cálculo de atan(2w) se han implementado con tablas multipartidas, combinado además con el uso de segmentación no-uniforme en el cálculo de atan(2w), y una segunda arquitectura que emplea interpolación lineal por tramos con pendientes potencias de dos y tablas de corrección. / Gutiérrez Mazón, R. (2011). Implementaciones de Funciones Elementales en Dispositivos FPGA [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/11519 / Palancia