Abstract In this thesis, novel data and channel estimation methods are proposed and analyzed for low-complexity short-range communication (SRC) radios. Low complexity is challenging to achieve especially in very wideband or millimeter-wave SRC radios where phase recovery and energy capture from numerous multipaths easily become a bottleneck for system design. A specific type of transceiver is selected using pulse amplitude modulation (PAM) at the transmitter and energy detection (ED) at the receiver, and it is thus called an ED-PAM system. Nonnegative PAM alphabets allow using an ED structure which enables a phase-unaware detection method for avoiding complicated phase recovery at the receiver. Moreover, the ED-PAM approach results in a simple multipath energy capture, and only one real decision variable, whose dimension is independent of the symbol alphabet size, is needed. In comparison with optimal phase-aware detection, the appealing simplicity of suboptimal ED-PAM systems is achieved at the cost of the need for a higher transmitted signal energy or shorter link distance for obtaining a sufficient signal-to-noise ratio (SNR) at the receiver, as ED-PAM systems are more vulnerable to the effects of noise and interference. On the other hand, the consequences of requiring a higher SNR may not be severe in the type of SRC scenarios where a sufficient received SNR is readily available due to a short link distance. Furthermore, significant interference can be avoided by signal design. However, what has slowed down the development of ED-PAM systems is that efficient symbol decision threshold estimation and related error probability analysis in multipath fading channels have remained as unsolved problems. Based on the above observations, this thesis contributes to the state-of-the-art of the design and analysis for ED-PAM systems as follows. Firstly, a closed-form near-optimal decision threshold selection method, which adapts to a time-varying channel gain and enables an arbitrary choice of the PAM alphabet size and an integer time-bandwidth product of the receiver filters, is proposed. Secondly, two blind estimation schemes of the parameters for the threshold estimation are introduced. Thirdly, analytical error probability evaluation in frequency-selective multipath fading channels is addressed. Special attention is given to lognormal fading channels, which are typically used to model very wideband SRC multipath channels. Finally, analytical error probability evaluation with nonideal parameter estimation is presented. The results can be used in designing low-complexity transceivers for very wideband and millimeter-wave wireless SRC devices of the future. / Tiivistelmä Tässä työssä esitetään ja analysoidaan uusia data- ja kanavaestimointimenetelmiä, joiden tavoitteena on yksinkertaistaa lähikommunikaatiota (short-range communication, SRC) langattomien laitteiden välillä. SRC-radioiden yksinkertainen toteutus on poikkeuksellisen haasteellista silloin, kun käytetään erittäin suurta kaistanleveyttä tai millimetriaaltoalueen tiedonsiirtoa. Tällöin vastaanottimen yksinkertaisen toteutuksen voivat estää esimerkiksi kantoaallon vaiheen estimointi ja signaalienergian kerääminen lukuisilta kanavan monitiekomponenteilta. Näistä lähtökohdista valitaan SRC-radion järjestelmämalliksi positiiviseen pulssiamplitudimodulaatioon (pulse amplitude modulation, PAM) perustuva lähetin ja energiailmaisimeen (energy detection, ED) perustuva vastaanotin. ED-PAM-järjestelmän ei tarvitse tietää vastaanotetun signaalin vaihetta ja signaalienergian kerääminen tapahtuu yksinkertaisen diversiteettiyhdistelytekniikan avulla. Lisäksi ilmaisuun tarvitaan vain yksi reaalinen päätösmuuttuja, jonka dimensio on riippumaton PAM-tasojen määrästä. ED-PAM-tekniikan yksinkertaisuutta optimaaliseen vaihetietoiseen ilmaisuun verrattuna ei saavuteta ilmaiseksi. Yhtenä rajoituksena on alioptimaalisen ED-PAM-tekniikan luontainen taipumus vahvistaa kohinan ja häiriöiden vaikutusta symbolin päätöksenteossa. Kohinan vahvistus ei välttämättä ole suuri ongelma niissä SRC-radioissa, joissa pienen linkkietäisyyden johdosta riittävä signaali-kohinasuhde vastaanottimessa voidaan kohinan vahvistuksesta huolimatta saavuttaa. Myös häiriöiden vahvistuksen vaikutusta voidaan tehokkaasti vähentää signaalisuunnittelulla. Joka tapauksessa ED-PAM-tekniikan käyttöönottoa on hidastanut tehokkaiden symbolipäätöskynnysten estimointi- ja analysointimenetelmien puuttuminen. Edellä mainitut havainnot ovat motivoineet löytämään uusia suunnittelu- ja analyysimenetelmiä ED-PAM-järjestelmille seuraavasti. Symbolipäätöskynnysten estimointiin johdetaan lähes optimaalinen suljetun muodon menetelmä, joka kykenee adaptoitumaan muuttuvassa kanavassa ja valitsemaan mielivaltaisen kokonaisluvun sekä PAM-tasojen määrälle että vastaanottimen aika-kaistanleveystulolle. Lisäksi esitetään kaksi sokeaa päätöskynnysten estimointimenetelmää, jotka eivät tarvitse redundanttista opetussignaalia. Työn toisessa osassa ED-PAM-järjestelmän symbolivirhesuhdetta analysoidaan taajuusselektiivisessä monitiekanavassa. Analyysissä keskitytään log-normaalijakauman mukaan häipyvään kanavaan. Seuraavaksi analyysia laajennetaan ottamalla mukaan epäideaalisten kynnysarvojen estimoinnin vaikutus. Saavutettuja tuloksia voidaan hyödyntää erittäin laajakaistaisten ja millimetriaaltoalueen SRC-laitteiden suunnittelussa.

Orientador: Celso de Almeida / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação / Made available in DSpace on 2018-08-26T13:51:01Z (GMT). No. of bitstreams: 1 OrozcoGarzon_NathalyVeronica_M.pdf: 2420238 bytes, checksum: 44b2e62e1f4262ea3a2a169999209c79 (MD5) Previous issue date: 2014 / Resumo: A principal contribuição desta tese é a proposta de um mecanismo com transmissão oportunista. Este método de transmissão é realizado apenas quando o desvanecimento no receptor estiver acima de um certo limiar. Neste sistema oportunista o transmissor e o receptor estão em constante comunicação através de um canal de realimentação e o receptor indica ao transmissor quando ele deve transmitir. Para a análise de desempenho do sistema oportunista vamos considerar um canal com ruído e desvanecimento plano e lento Rayleigh e também interferência de co-canal (CCI) vamos também considerar diferentes esquemas de modulação (BPSK, QPSK, 4-QAM, 16-QAM e 64-QAM). A análise de desempenho do sistema proposto baseia-se na probabilidade de erro de bit média (BER), para a qual expressões analíticas foram obtidas. Estas expressões foram verificadas usando o método de simulação de Monte Carlo, com excelente concordância entre os dois resultados. Além disso, foram consideradas a eficiência espectral e a potência de transmissão do sistema. Os resultados obtidos mostram que a transmissão oportunista pode combater o desvanecimento de forma eficiente, pois o sistema oportunista elimina os efeitos do desvanecimento quase em sua totalidade. Foi feita também uma comparação entre o sistema oportunista e um sistema ordinário para a comparação de desempenho. Além disso, a transmissão oportunista é menos sensível à interferência de co-canal. Várias curvas são apresentadas ilustrando a eficiência do mecanismo oportunista proposto em termos da probabilidade de erro de bit média / Abstract: This thesis proposes, as the main contribution, a new mechanism with an opportunistic transmission. This transmission method is realized just when the fading at receiver is above a threshold value. In this opportunistic system the transmitter and the receiver are in constant communication through a feedback link and the receiver indicates when the transmitter should transmit. To analyze the performance of the opportunistic system we consider a noise channel and a flat and slow Rayleigh fading channel in the presence of co-channel interference (ICC). We also consider different modulation schemes (BPSK, QPSK, 4-QAM, 16-QAM e 64-QAM). The performance analysis of the proposed system is based on the mean bit error probability (BER), for which analytical expressions are established. These expressions are verified using Monte-Carlo simulation method with excellent agreement between both results. Furthermore, we consider the spectral efficiency and the power transmission of this system. The opportunistic transmission can combat the fading efficiently. That is, once it eliminates the fading effects almost entirely. Moreover, it is made a comparison between the opportunistic system and the ordinary system performance. Furthermore, the opportunistic transmission is less sensitive to co-channel interference. Several figures are presented illustrating the efficiency of the proposed mechanism in terms of mean bit error probability / Mestrado / Telecomunicações e Telemática / Mestra em Engenharia Elétrica

This thesis deals with the demonstration of bit error rate reduction techniques. In the theory section, different techniques of bit error rate reduction are presented, followed by the introduction of the communication channel and the communication system parameters. Each technique is simulated in Matlab Simulink environment using the additive white Gaussian noise channel model. The simulations are captured in waveform oscillograms of all the signal processing stages. The practical section of this thesis offers a functional laboratory solution demonstrating different ways of transmission: a direct-path signal, a path with a cross-correlation receiver and a path using matched filtering. The individual circuits are described in detail, including waveform oscillograms of the signal processing blocks for illustration. Furthermore, the practical section presents printed circuit boards designs, comprehensive documentation for production, measurement results and a sample laboratory protocol.

L’objectif principal de cette thèse est l’analyse des performances des réseaux LTE-A (Long Term Evolution- Advanced) au travers de la géométrie stochastique. L’analyse mathématique des réseaux cellulaires est un problème difficile, pour lesquels ils existent déjà un certain nombre de résultats mais qui demande encore des efforts et des contributions sur le long terme. L’utilisation de la géométrie aléatoire et des processus ponctuels de Poisson (PPP) s’est avérée être une approche permettant une modélisation pertinente des réseaux cellulaires et d’une complexité faible (tractable). Dans cette thèse, nous nous intéressons tout particulièrement à des modèles s’appuyant sur ces processus de Poisson : PPP-based abstraction. Nous développons un cadre mathématique qui permet le calcul de quantités reflétant les performances des réseaux LTE-A, tels que la probabilité d’erreur, la probabilité et le taux de couverture, pour plusieurs scénarios couvrant entre autres le sens montant et descendant. Nous considérons également des transmissions multi-antennes, des déploiements hétérogènes, et des systèmes de commande de puissance de la liaison montante. L’ensemble de ces propositions a été validé par un grand nombre de simulations. Le cadre mathématique développé dans cette thèse se veut général, et doit pouvoir s’appliquer à un nombre d’autres scénarios importants. L’intérêt de l’approche proposée est de permettre une évaluation des performances au travers de l’évaluation des formules, et permettent en conséquences d’éviter des simulations qui peuvent prendre énormément de temps en terme de développement ou d’exécution. / The main focus of this thesis is on performance analysis and system optimization of Long Term Evolution - Advanced (LTE-A) cellular networks by using stochastic geometry. Mathematical analysis of cellular networks is a long-lasting difficult problem. Modeling the network elements as points in a Poisson Point Process (PPP) has been proven to be a tractable yet accurate approach to the performance analysis in cellular networks, by leveraging the powerful mathematical tools such as stochastic geometry. In particular, relying on the PPP-based abstraction model, this thesis develops the mathematical frameworks to the computations of important performance measures such as error probability, coverage probability and average rate in several application scenarios in both uplink and downlink of LTE-A cellular networks, for example, multi-antenna transmissions, heterogeneous deployments, uplink power control schemes, etc. The mathematical frameworks developed in this thesis are general enough and the accuracy has been validated against extensive Monte Carlo simulations. Insights on performance trends and system optimization can be done by directly evaluating the formulas to avoid the time-consuming numerical simulations.

Today’s communication systems are in need of spectrally efficient and high throughput techniques more than ever because of high data rate applications and the scarcity and expense of bandwidth. To cope with increased data rate demands, more base stations are needed which is not cost and energy efficient in cellular networks. It has been shown that wireless relay networks can provide higher network throughput and increase power efficiency with low complexity and cost. Furthermore, network resources can be utilized more efficiently by using network coding in relay networks. A wireless relay network in which multiple nodes exchange information with the help of relay node(s) is called a multi-way relay channel (MWRC). MWRCs are expected to be an integral part of next generation wireless standards. The main focus of this dissertation is the investigation of transmission schemes in an MWRC to improve the throughput and error performance. An MWRC with full data exchange is assumed in which a half-duplex relay station (RS) is the enabler of communication. One of the challenges with signal demodulation in MWRCs is the existence of ambiguous points in the received constellation. The first part of this dissertation investigates a transmission scheme for full data exchange in MWRC that benefits from these points and improves its throughput by 33% compared to traditional relaying. Then an MWRC is considered where a RS assists multiple nodes to exchange messages. A different approach is taken to avoid ambiguous points in the superposition of user symbols at the relay. This can be achieved by employing complex field network coding (CFNC) which results in full data exchange in two communication phases. CFNC may lead to small Euclidean distances between constellation points, resulting in poor error performance. To improve this performance, the optimal user precoding values are derived such that the power efficiency of the relay constellation is highest when channel state information is available at the users. The error performance of each user is then analyzed and compared with other relaying schemes. Finally, focusing on the uplink of multi-way relay systems, the performance of an MWRC is studied in which users can employ arbitrary modulation schemes and the links between the users and the relay have different gains, e.g. Rayleigh fading. Analytical expressions for the exact average pairwise error probability of these MWRCs are derived. The probability density function (PDF) and the mean of the minimum Euclidean distance of the relay constellation are closely approximated, and a tight upper bound on the symbol error probability is developed. / Graduate

Dans les systèmes radio mobiles, la diversité représente une technique efficace pour lutter contre l’évanouissement dû aux multi-trajets. La pleine diversité spatiale est atteinte dans les systèmes multiple-input multiple-output (MIMO). Mais, souvent l’intégration d’antennes multiples au niveau de l’émetteur ou du récepteur est coûteuse. Comme alternative, dans les réseaux sans fil multi-hop, la diversité coopérative garantit des gains de diversité spatiale en exploitant les techniques MIMO traditionnelles sans avoir besoin d’antennes multiples. En outre, la diversité coopérative fournit au réseau : un débit important, une énergie réduite et une couverture d’accès améliorée.Dans ce contexte, l’objectif de cette thèse est de concevoir des schémas de codage pour le canal à relais afin de réaliser une meilleure performance en termes de gain de diversité et de gain de codage. D’abord, nous étudions un système de turbo-codage distribué à L-relais en mode soft-decode-and-forward. Ensuite, nous proposons un système de turbocodage coopératif distribué à L-relais en utilisant la concaténation en parallèle des codes convolutifs. Enfin, afin d’améliorer la fiabilité de détection au niveau du noeud relais, nous proposons la technique de sélection d’antenne/relayage-soft. Pour une modulation BPSK, nous dérivons des expressions de la borne supérieure de la probabilité d’erreurbinaire où les différents sous-canaux sont supposés à évanouissement de Rayleigh, indépendants et pleinement entrelacés avec une information instantanée d’état de canal idéal. Une validation des résultats théoriques est également menée par la simulation. / Diversity provides an efficient method for combating multipath fading in mobile radio systems. One of the most common forms of spatial diversity is multiple-input multipleoutput (MIMO), where full diversity is obtained. However, embedding multiple antennas at the transmitter or the receiver can sometimes be expensive. As an alternative to collocated antennas, cooperative diversity in wireless multi-hop networks confirms their ability to achieve spatial diversity gains by exploiting the spatial diversity of the traditional MIMO techniques, without each node necessarily having multiple antennas. In addition, cooperative diversity has been shown to provide the network with importantthroughput, reduced energy requirements and improved access coverage.In light of this, the objective of this thesis is to devise coding schemes suitable for relay channels that aim at showing the best compromise between performance of diversity and coding gains. Firstly, we investigate a distributed turbo coding scheme dedicated to L-relay channels operating in the soft-decode-and-forward mode. Then, we present a proposed distributed turbo coded cooperative (DTCC) scheme, called parallel concatenated convolutional-based distributed coded cooperation. Finally, we investigate antenna/soft-relaying selection for DTCC networks in order to improve their end-to-end performance. Assuming BPSK transmission for fully interleaved channels with ideal channel state information, we define the explicit upper bounds for error probability inRayleigh fading channels with independent fading. Both theoretical limits and simulation results are presented to demonstrate the performances.

Digital communication systems which use Orthogonal Frequency Division Multiplexing (OFDM) are now widely used and have many advantages. The main disadvantage is the requirement for highly linear analogue electronics including the high power amplifier (HPA). This requirement cannot be met in all circumstances because of the occurrence of symbols with high peak to average power ratio (PAPR). Such symbols may be non-linearly distorted by limiting. Approaches to solve this problem have been either to reduce the PAPR at the transmitter or to try to mitigate the effect of the non-linearity at the receiver. Soft-limiting, i.e. applying limiting in software prior to the HPA is a simple way to reduce the PAPR. It produces non-linear distortion which will cause an increase in the bit-error-rate (BER) at the receiver. This thesis surveys existing alternatives ways of reducing the effect of non-linearity and proposes some new ones. Two iterative receiver techniques, based on statistical analysis of the nature of the non-linearity, have been implemented and investigated. These are the ‘Bussgang Noise Cancellation’ (BNC) technique and the ‘Decision Aided Reconstruction’ (DAR) techniques. As these techniques are valid for any memory-less nonlinearity, an alternative form of limiting, named as Inverted-Wraparound (IWRAP) has been included in the BNC investigation. A new method is proposed which is capable of correcting the received time-domain samples that are clipped, once they have been identified. This is named the ‘Equation-Method’ and it works by identifying constellation symbols that are likely to be correct at the receiver. If there are a sufficient number of these and they are correctly identified, the FFT may be partitioned to produce a set of equations that may be solved for the clipped time-domain samples. The thesis proposes four enhancements to this new method which improve its effectiveness. It is shown that the best form of this method outperforms conventional techniques especially for severe clipping levels. The performance of these four enhancements is evaluated over channels with additive white Gaussian noise (AWGN) in addition to clipping distortion. A technique based on a ‘margin factor’ is designed to make these methods work more effectively in the presence of AWGN noise. A new combining algorithm referred as ‘HARQ for Clipping’ is presented where soft bit decisions are combined from multiple transmissions. ‘HARQ for Clipping’ has been combined with the best version of the Equation-Method, and the performance of this approach is evaluated in terms of the BER with different levels of AWGN. It has been compared to other approaches from the literature and was found to out-perform the BNC iterative receiver by 3dB at signal to noise ratios around 10dB. Without HARQ, the best version of the Equation-Method performs better than the BNC receiver, at signal-to-nose ratios above about 17dB.

Die extrem große Bandbreite, die UWB-Systeme zur Übertragung von Daten nutzen können, ermöglicht theoretisch eine sehr hohe Datenrate. Eine mögliche Umsetzung der UWB-Technologie ist die sogenannte Multiband-Impuls-Radio-Architektur (MIRA). Dieses UWB-System basiert auf der Übertragung von Daten mittels kurzer Impulse parallel in mehreren Frequenzbändern. Als Empfänger kommen einfache Energiedetektoren zum Einsatz. Diese Komponenten haben entscheidenden Einfluss auf die Leistungsfähigkeit des gesamten Systems. Deshalb liegt der Schwerpunkt dieser Arbeit auf der Untersuchung der Leistungsfähigkeit und im speziellen der Herleitung der Bitfehlerwahrscheinlichkeiten für Energiedetektoren in unterschiedlichen UWB-Kanälen. Aufgrund des sehr einfachen Aufbaus eines Energiedetektors wird dieser auch in vielen anderen Bereichen eingesetzt. So werden Energiedetektoren zur Detektion von freien Bereichen im Übertragungsspektrum bei Cognitive Radio und für weitere unterschiedliche Übertragungssysteme wie z.B. Sensorsysteme mit geringer Datenrate und Übertragungssysteme die zusätzlich Ortung ermöglichen, genutzt.

Dans cette thèse, les réseaux coopératifs sont étudiés sous cette hypothèse que la source est incertain par rapport le canal en opération. Dans le premier chapitre, des stratégies coopératives sont développées pour les canaux à relais simultanés (SRC) lesquelles se composent d'un ensemble de deux canaux à relais parmi lesquels le canal en opération est choisi. Cela est équivalent au canal de diffusion à relais (BRC). Les bornes sur la région de capacité de BRC général sont dérivées. Les résultats de capacité sont obtenus pour les cas particuliers du canal à relais simultané semi-dégradé et dégradé Gaussien. Dans le deuxième chapitre, le canal à relais composite est considéré où le canal est tiré aléatoirement d'un ensemble de la distribution conditionnelle. Le débit est fixé en dépit du canal actuel et la probabilité d'erreur (EP) asymptotique est caractérisée. Une nouvelle stratégie de codage sélectif (SCS) est introduit permettant aux relais de choisir -selon leur mesurage du canal – la meilleur schéma de codage entre Décoder-et-Transmettre (DF) et Comprimer-et-Transmettre (CF). Les théorèmes de codage de réseau bruit généralisées sont démontrés pour le cas de réseau unicast général où les relais utilisent soit DF soit CF. Dans le troisième chapitre, le spectre asymptotique de EP est introduit en tant que nouvelle mesure de performance pour réseaux composites. Il est démontré que chaque code avec le débit hors de la borne cut-set, abouti à EP égal à un et le spectre asymptotique de EP coïncide avec la probabilité d'outage pour les réseaux satisfaisant la converse forte. / In this thesis, cooperative networks are studied under the assumption that the source is uncertain about the channel in operation. In the first chapter, cooperative strategies are developed for simultaneous relay channels (SRC) which consist of a set of two single relay channels out of which the channel in operation is chosen. This is equivalent to the broadcast relay channel (BRC). Bounds on the capacity region of the general BRC with two helper relays are derived. Capacity results are obtained for specific cases of semi-degraded and degraded Gaussian simultaneous relay channels. In the second chapter, the composite relay channel is considered where the channel is randomly drawn from a set of conditional distributions according to a given distribution. The transmission rate is fixed regardless of the current channel and the asymptotic error probability (EP) is characterized. A novel selective coding strategy (SCS) is introduced which enables relays to select –based on their channel measurement– the best coding scheme between Compress-and-Forward (CF) and Decode-and-Forward (DF). Generalized Noisy Network Coding theorems are shown for the case of unicast general networks where the relays use either DF or CF scheme. In the third chapter, the asymptotic behavior of EP is studied for composite multiterminal networks. The asymptotic spectrum of EP is introduced as a novel performance measure for composite networks. It is shown that every code with rate outside cut-set bound, yields EP equal to one and for the networks satisfying strong converse condition, the asymptotic spectrum of EP coincides with the outage probability.

Although it has been well established that abnormal group delay is a real physical phenomenon and is not in violation of Einstein causality, there has been little investigation into whether or not such abnormal behaviour can be used to reduce signal latency in practical communication systems in the presence of noise. In this thesis, we use time-varying probability of error to determine if abnormal group delay “channels” can offer reduced signal latency. Since the detection system plays a critical role in the analysis, three important detection systems are considered: the correlation, matched filter and envelope detection systems. Our analysis shows that for both spatially negligible microelectronic systems and spatially extended microwave systems, negative group delay “channels” offer reduced signal latency as compared to conventional “channels”. The results presented in the thesis can be used to design a new generation of electronic and microwave interconnects with reduced or eliminated signal latency.