Multiband OFDM for Cognitive Radio – A Way for Cyclostationary Detection and Interference Cancellation

With the tremendous growth in wireless technology there has been a shortage in the spectrum utilized for certain applications while some spectrum remains idle. To overcome this problem and for the efficient utilization of the spectrum cognitive radio is the suitable solution.Multiband OFDM can be easily modeled as cognitive radio, a technology that is employed for utilizing the available spectrum in the most efficient way. Since sensing of the free spectrum for detecting the arrival of the primary users is the foremost job of cognitive, here cyclostationary based spectrum sensing is carried out. Its performance is investigated using universal software defined radio peripheral (USRP) kit which is the hardware test bed for the cognitive radio system. Results are shown using Labview software. Further to mitigate the interference between the primary and cognitive users a modified intrusion elimination (AIC) algorithm had been proposed which in turn ensures the coexistence of both the users in the same wireless environment

Communication Subsystems for Emerging Wireless Technologies

The paper describes a multi-disciplinary design of modern communication systems. The design starts with the analysis of a system in order to define requirements on its individual components. The design exploits proper models of communication channels to adapt the systems to expected transmission conditions. Input filtering of signals both in the frequency domain and in the spatial domain is ensured by a properly designed antenna. Further signal processing (amplification and further filtering) is done by electronics circuits. Finally, signal processing techniques are applied to yield information about current properties of frequency spectrum and to distribute the transmission over free subcarrier channels

Timing and Carrier Synchronization in Wireless Communication Systems: A Survey and Classification of Research in the Last 5 Years

Timing and carrier synchronization is a fundamental requirement for any wireless communication system to work properly. Timing synchronization is the process by which a receiver node determines the correct instants of time at which to sample the incoming signal. Carrier synchronization is the process by which a receiver adapts the frequency and phase of its local carrier oscillator with those of the received signal. In this paper, we survey the literature over the last 5 years (2010–2014) and present a comprehensive literature review and classification of the recent research progress in achieving timing and carrier synchronization in single-input single-output (SISO), multiple-input multiple-output (MIMO), cooperative relaying, and multiuser/multicell interference networks. Considering both single-carrier and multi-carrier communication systems, we survey and categorize the timing and carrier synchronization techniques proposed for the different communication systems focusing on the system model assumptions for synchronization, the synchronization challenges, and the state-of-the-art synchronization solutions and their limitations. Finally, we envision some future research directions

Technology Implications of UWB on Wireless Sensor Network-A detailed Survey

In today’s high tech “SMART” world sensor based networks are widely used. The main challenge with wireless-based sensor networks is the underneath physical layer. In this survey, we have identified core obstacles of wireless sensor network when UWB is used at PHY layer. This research was done using a systematic approach to assess UWB’s effectiveness (for WSN) based on information taken from various research papers, books, technical surveys and articles. Our aim is to measure the UWB’s effectiveness for WSN and analyze the different obstacles allied with its implementation. Starting from existing solutions to proposed theories. Here we have focused only on the core concerns, e.g. spectrum, interference, synchronization etc.Our research concludes that despite all the bottlenecks and challenges, UWB’s efficient capabilities makes it an attractive PHY layer scheme for the WSN, provided we can control interference and energy problems. This survey gives a fresh start to the researchers and prototype designers to understand the technological concerns associated with UWB’s implementatio

Reliable Cognitive Ultra Wideband Communication Systems Under Coexistence Constraints

RÉSUMÉ La croissance rapide des systèmes de communication sans fil et la rareté du spectre ont motivé les industries et les fournisseurs ouvrant dans le domaine de communication sans fil de développer des stratégies et des technologies de communication qui peuvent utiliser efficacement les ressources spectrales. La réutilisation pacifique du spectre sous-licence et sous-utilisé peut être une solution prometteuse pour certaines initiatives en cours telles que la communication mobile à haut débit, la communication machine-à-machine, et la connectivité WiFi. Un des plus gros facteurs qui empêche l'approche de cette réutilisation de fréquences est l'effet d'environnements bruyants sur les dispositifs coexistent dans la même bande de fréquence. Par conséquent, la demande pour une stratégie de coexistence pacifique entre les utilisateurs du spectre, des défis et des questions techniques qu'elle engêndre, motive notre recherche. Il est à noter que dans cette thèse, nous considérons un système pratique appelé MB-OFDM UWB (en anglais multiband orthogonal frequency division multiplexing ultra wideband) pour donner un aperçu pratique de ce concept. Pour atteindre cet objectif, d'abord nous examinons le problème d'interférence des utilisateurs secondaires sur les utilisateurs principaux. A cet effet, tenant compte d'un système secondaire OFDM, nous proposons des méthodes de mise en forme du spectre pour les applications de transmission à antennes simples et multiples. Nous présentons une technique débit-efficace nommée “Enhanced active interference cancellation (E - AIC)qui est en effet capable de créer des encoches ayant des caractéristiques flexibles. Afin de résoudre le problème de dépassement du spectre causé pas la technique classique-AIC, nous utilisons une approche multi-contraintes qui à son tour cause un problème multi-contrainte de minimisation (en anglais multi-constraint minimization problem, MCMP). Cependant, un nouvel algorithme itératif basé sur la technique SVD (en anglais singular value decomposition) est proposé, permettant ainsi de réduire la complexité de la solution de MCMP. Les résultats de simulation obtenus montrent que la technique E-AIC proposée fournit de meilleures performances en termes de suppression des lobes latéraux avec 0 dB de dépassement, moins de complexité de calcul et moins de perte de débit par rapport aux méthodes AIC précédentes. Quant aux antennes multiples, nous proposons deux nouvelles techniques AIC, qui utilisent l'idée principale des approches de sélection d'antennes d'émission (en anglais transmit antenna selection, TAS). Bien que les résultats montrent que les deux techniques permettent la création d'encoche identique, la technique per-tone TAS-AIC a la plus grande efficacité spectrale. Après avoir obtenu une emission sans interférence pour le système MB-OFDM UWB, nous analysons, modélisons et atténuons le bruit impulsif au récepteur MB-OFDM UWB. Pour ce faire, d'abord, nous proposons un cadre analytique qui décrit les principales caractéristiques d'interférence d'un système à ultra large bande et saut temporel (en anglais time-hopping UWB, TH-UWB) niveau de ces paramètres de signalisation. Les résultats montrent que la distribution d'interférence dépend fortement aux paramètres de saut temporel du système TH-UWB.----------ABSTRACT The rapid growth of wireless communication systems along with the radio spectrum's scarcity and regulatory considerations have put the onus on the wireless industries and service providers to develop wireless communication strategies and technologies that can efficiently utilize the spectral resources. Hence, peaceful reuse of underutilized licensed radio frequencies (by secondary users) can be a promising solution for some ongoing initiatives such as mobile broadband, machine-to-machine applications and WiFi connectivity. One of the biggest factors that prevents the spectrum reusing approach to effectively address the spectrum scarcity, is noisy environments result from coexistence of different devices in the same frequency band. Therefore, the request for a peaceful coexistence strategy between spectrum users, which leads to various challenges, and technical issues, motivates our research. It is worth noting that, in this thesis, we consider a practical system called multiband orthogonal frequency division multiplexing ultra wideband (MB-OFDM UWB) as an underlay system to provide a practical insight into this concept. However, all the obtained results and contributions are applicable to other OFDM-based communication systems. Towards this goal, we first investigate the problem of the interference from secondary users to the primary users. For this purpose, considering an OFDM-based secondary communication system, we propose spectrum-shaping methods for single and multiple transmit antennas applications. For single antenna scenario, we present a throughput-efficient enhanced active interference cancellation (E-AIC) technique, which is indeed capable of creating notches with flexible characteristics. In order to address the spectrum overshoot problem of conventional-AIC techniques, we employed a multi-constraint approach, which leads to a multi-constraint minimization problem (MCMP). Hence, a novel iterative singular value decomposition (SVD) based algorithm is proposed to reduce the complexity of the MCMP's solution. The obtained simulation results show that the proposed enhanced-AIC technique provides higher performance in terms of sidelobes suppression with 0 dB overshoot, less computational complexity and less throughput-loss compared to previous constrained-AIC methods. For multiple transmit antennas, we propose two novel AIC techniques employing main ideas behind bulk and per-tone transmit antenna selection (TAS) approaches. Simulation results show that although both techniques provide identical notch creation, the per-tone TAS-AIC technique has higher spectral efficiency

Architectures and Novel Functionalities for Optical Access OFDM Networks "Arquitecturas y Nuevas Funcionalidades para Redes OFDM de Acceso Óptico"

En los últimos años ha habido un gran aumento en el despliegue de redes de acceso ópticas de fibra hasta el hogar (FTTH, del inglés fibre-to-the home). FTTH es una solución flexible, una tecnología de acceso de futuro que permite proporcionar tasas de datos del orden de Gbit/s por ususario. Diversos estudios indican que FTTH se convertirá en la diferencia clave entre los operadores más importantes. Además, FTTH es la única tecnolotgía capaz de crear nuevas fuentes de ingresos de aplicaciones de alta velocidad, como por ejemple entretenimiento de alta definición (vído y juegos de alta definición...) Dede el punto de vista del operador, una de las vientajas importantes que proporciona FTTH es que permite una mayor eficiencia operativa en coparción con otras tecnologías de acceso, principalmente por la reducción de costes de mantenimiento y de operación. Además, FTTH reduce los requisitos de los equipos de las centrales. Esta tesis doctoral tiene como ojetivo extender estas ventajas más allá del concepto FTTH mediante la integración de la red óptica de distribución desplegada dentro del hogar así como el enlace radio final de corto o medio alcance inalámbrico. Esto proporciona una arquitctura de red FFTH integrada de extremo a extremo. De este modo, los beneficios de la reducción de costes operativos y mayor eficiencia se extienden hasta el usuario final de la red. En esta tesis doctoral, se propone una arqutectura de acceso integrada óptica-radio basada en la multiplexación por división ortogonal de fecuencia (OFDM, del inglés orthogonal frequency división multiplexing) para proporcionar diferentes servicios al usuario como Internet, teléfono/voz, televisión de lata definición, conexión inalámbrica y seguridad en el hogar. Las señales OFDM se utilizan en muchos estándares inalámbricos como las señales de banda ultraancha (UWB, del inglés ultra-wide band), WiMAX, LTE, WLAN, DVB-T o DAB. Estos formatos aprovechan las características intrínsecas de la modulación OFDM como su mayor inmunidad ante desvanecimiento multi-camino. Esta tesis incluye la propuesta y la demostración experimental de la transmisión simultánea y bi-direccional de señales OFDM multi-estándar en radio-sobre-fibra proporcionando servicios triple-play basados en OFDM como UWB para televisión de alta definición, WiMAX para datos de Internet, y LTE para el servicio telefónico.Morant Perez, M. (2012). Architectures and Novel Functionalities for Optical Access OFDM Networks "Arquitecturas y Nuevas Funcionalidades para Redes OFDM de Acceso Óptico" [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/15076Palanci

A Unified Multi-Functional Dynamic Spectrum Access Framework: Tutorial, Theory and Multi-GHz Wideband Testbed

Dynamic spectrum access is a must-have ingredient for future sensors that are ideally cognitive. The goal of this paper is a tutorial treatment of wideband cognitive radio and radar—a convergence of (1) algorithms survey, (2) hardware platforms survey, (3) challenges for multi-function (radar/communications) multi-GHz front end, (4) compressed sensing for multi-GHz waveforms—revolutionary A/D, (5) machine learning for cognitive radio/radar, (6) quickest detection, and (7) overlay/underlay cognitive radio waveforms. One focus of this paper is to address the multi-GHz front end, which is the challenge for the next-generation cognitive sensors. The unifying theme of this paper is to spell out the convergence for cognitive radio, radar, and anti-jamming. Moore’s law drives the system functions into digital parts. From a system viewpoint, this paper gives the first comprehensive treatment for the functions and the challenges of this multi-function (wideband) system. This paper brings together the inter-disciplinary knowledge