Block synchronization algorithms for UWB-OFDM systems

Orthogonal Frequency-Division Multiplexing (OFDM) is a modulation known by its high spectral efficiency, high tolerance to multipath delay spread in frequency selective channels, and low cost of implementation. However, OFDM systems are extremely sensitive to synchronizations errors. In this paper, we propose an unbiased block synchronization algorithm that uses the structure of the cyclic prefix, the presence of pilot tones in the OFDM block, and an estimation of the channel time impulse response. This algorithm is able to achieve fast synchronization as required, for instance, on Ultra-Wide Band (UWB) multipath fading channels. To quantify the performance of the block synchronization algorithm, we use the start of frame mean square error. Through numerical simulations, we show that our algorithm outperforms previously published synchronization algorithms.Fil: Maya, Juan Augusto. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Electronica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Galarza, Cecilia Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Electronica; Argentin

Etude et évaluation d un multiplexage fréquentiel basé sur l OFDM/OQAM

Cette thèse est consacrée à l étude de la modulation OFDM/OQAM en tant qu alternative à la modulation OFDM. Nous traitons plus particulièrement le contexte multiusagers. De ce point de vue, les aspects de synchronisation sont déterminants. Les différentes options plus le choix de la forme d onde sont donc examinés de ce point de vue. Un autre objectif est de montrer de manière précise comment la modulation OFDM/OQAM peut s adapter à une transmission de type cellulaire, en prenant comme référence le système 3GPP/LTE. Les principales contributions que nous avons apportées sont : 1) Une analyse des phénomènes de désynchronisation : nous analysons l effet de la désynchronisation, suivant les axes temporel et fréquentiel, sur les performances de l OFDM/OQAM au récepteur. 2) Méthode de synchronisation : nous analysons une méthode de synchronisation temporelle définie dans un contexte de transmission OFDM/OQAM mono-usager et nous l adaptons à un scénario de type multi-usagers. 3) Proposition d un schéma d accès multiple : nous proposons un schéma d accès multiple basé sur la modulation OFDM/OQAM, alternatif aux techniques connues OFDMA et SC-FDMA, pour la transmission en liaison montante dans un contexte de type 3GPP/LTE.This thesis is dedicated to the study of the OFDM/OQAM modulation as an alternative to the OFDM modulation. We treat more especially the multi-user environment. In this respect, synchronization aspects are crucial. The different options plus the choice of the waveform are examined in this point of view. Another objective is to precisely show how the OFDM/OQAM can be adapted to a cellular transmission type, taking as reference the 3GPP/LTE system. The main contributions we have made are : 1) Analysis of the desynchronization phenomena : we analyze the effect of desynchronization, according to the time and frequency axes, on the performance of OFDM/OQAM at the receiver side. 2) Synchronization method : we analyze a method of temporal synchronization defined in a single user OFDM/OQAM transmission and we adapt it to a multi-user scenario type. 3) Proposing for a multiple access scheme : we propose a multiple access scheme based on theOFDM/OQAM modulation, alternative to the known techniques OFDMA and SC-FDMA, for the UL transmission in a 3GPP/LTE context.PARIS-CNAM (751032301) / SudocSudocFranceF

Digital Signal Processing for Front-end Non-idealities in Coherent Optical OFDM system

Ph.DDOCTOR OF PHILOSOPH

MIMO OFDM Radar-Communication System with Mutual Interference Cancellation

This work describes the OFDM-based MIMO Radar-Communication System, intended for operation in a multiple-user network, especially the automotive sector in the vehicle-to vehicle/infrastructure network. The OFDM signals however are weak towards frequency offsets causing subcarrier misalignment and corrupts the radar estimation and the demodulation of the communication signal. A simple yet effective interference cancellation algorithm is detailed here with real time measurement verification

On the cyclostationarity of orthogonal frequency division multiplexing and single carrier linear digital modulations: theoretical developments and applications

In recent years, new technologies for wireless communications have emerged. The wireless industry has shown great interest in orthogonal frequency division multiplexing (OFDM) technology, due to the efficiency of OFDM schemes to convey information in a frequency selective fading channel without requiring complex equalizers. On the other hand, the emerging OFDM wireless communication technology raises new challenges for the designers of intelligent radios, such as discriminating between OFDM and single-carrier modulations. To achieve this objective we study the cyclostationarity of OFDM and single carrier linear digital (SCLD) modulated signals. -- In this thesis, we first investigate the nth-order cyclostationarity of OFDM and SCLD modulated signals embedded in additive white Gaussian noise (AWGN) and subject to phase, frequency and timing offsets. We derive the analytical closed-form expressions for the nth-order (q-conjugate) cyclic cumulants (CCs) and cycle frequencies (CFs), and the nth-order (q-conjugate) cyclic cumulant polyspectra (CCPs) of OFDM signal, and obtain a necessary and sufficient condition on the oversampling factor (per subcarrier) to avoid cycle aliasing. An algorithm based on a second-order CC is proposed to recognize OFDM against SCLD modulations in AWGN channel, as an application of signal cyclostationarity to modulation recognition problem. -- We further study the nth-order cyclostationarity of OFDM and SCLD modulated signals, affected by a time dispersive channel, AWGN, carrier phase, and frequency and timing offsets. The analytical closed-form expressions for the nth-order (q-conjugate) CCs and CFs, the nth-order (q-conjugate) CCPs of such signals are derived, and a necessary and sufficient condition on the oversampling factor (per subcarrier) is obtained to eliminate cycle aliasing for both OFDM and SCLD signals. We extend the applicability of the proposed algorithm in AWGN channel to time dispersive channels to recognize OFDM against SCLD modulations. The proposed algorithm obviates the preprocessing tasks; such as symbol timing, carrier and waveform recovery, and signal and noise power estimation. This is of practical significance, as algorithms that rely less on preprocessing are of crucial interest for receivers that operate with no prior information in a non-cooperative environment. It is shown that the recognition performance of the proposed algorithm in time dispersive channel is close to that in AWGN channel. In addition, we have noticed that the performance of recognizing both OFDM and SCLD signals does not depend on the modulation format used on each subcarrier for OFDM and for SCLD signals respectively

Recent advances in the hardware architecture of flat display devices

Thesis (Master)--Izmir Institute of Technology, Electronics and Communication Engineering, Izmir, 2007Includes bibliographical References (leaves: 115-117)Text in English; Abstract: Turkish and Englishxiii, 133 leavesThesis will describe processing board hardware design for flat panel displays with integrated digital reception, the design challenges in flat panel displays with integrated digital reception explained with details. Thesis also includes brief explanation of flat panel technology and processing blocks. Explanations of building blocks of TV and flat panel displays are given before design stage for better understanding of design stage. Hardware design stage of processing board is investigated in two major steps, schematic design and layout design. First step of the schematic design is system level block diagram design. Schematic diagram is the detailed application level hardware design and layout is the implementation level of the design. System level, application level and implementation level hardware design of the TV processing board is described with details in thesis. Design challenges, considerations and solutions are defined in advance for flat panel displays

MAC layer assisted localization in wireless environments with multiple sensors and multiple emitters

Extreme emitter density (EED) RF environments, defined as 10k-100k emitters within a footprint of less than 1 km squared, are becoming increasingly common with the proliferation of personal devices containing myriad communication standards (e.g. WLAN, Bluetooth, 4G, etc). Attendees at concerts, sporting events, and other such large-scale events desire to be connected at all times, creating tremendous spectrum management challenges, especially in unlicensed frequencies such as 2.4 GHz, 5 GHz, or 900 MHz Industrial, Scientific, and Medical (ISM) bands. In licensed bands, there are often critical communication systems such as two-way radios for emergency personnel which must be free from interference. Identification and localization of a non-conforming or interfering Emitter of Interest (EoI) is important for these critical systems. In this dissertation, research is conducted to improve localization for these EED RF environments by exploiting side information available at the Medium Access Control (MAC) layer. The primary contributions of this research are: (1) A testbed in Bobby Dodd football stadium consisting of three spatially distributed, time-synchronized RF Sensor Nodes (RFSN) collecting and archiving complex baseband samples for algorithm development and validation. (2) A modeling framework and analytical results on the benefits of exploiting the structure of the MAC layer for associating physical layer measurements, such as Time Difference of Arrivals (TDoA), to emitters. (3) A three stage localization algorithm exploiting time between packets and a constrained geometry to shrink the error ellipse of the emitter position estimate. The results are expected to improve localization accuracy in wireless environments when multiple sensors observe multiple emitters using a known communications protocol within a constrained geometry.Ph.D