Download or read book Analysis of Inter channel Interference Due to Multipath Fading Effect for ASK OFDM Systems written by Vishu Suvarna and published by . This book was released on 2003 with total page 200 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Analysis and Cancellation of Inter carrier Interference for OFDM Systems Over Time variant Multipath Fading Channels written by Yunjun Zhang and published by . This book was released on 2002 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The orthogonality among the subcarriers of OFDM systems may be impaired by the time-selectivity of the fading channels. The loss of the orthogonality results in ICI, and if it is not treated appropriately, the system performance may not be improved only by increasing the signal-to-noise ratio. In other words, ICI results in error floors. This research work concentrates on the ICI analysis and cancellation, and also on the effects of channel time-selectivity on the OFDM systems over frequency-selective time-variant mobile fading channels. In the first part of this study, a general time-variant frequency-selective WSSUS fading channel model is further characterized to support the OFDM ICI analysis, thus the obtained results are applicable for many specific channels. We then identify the cause of the ICI, i.e. how the orthogonality among the subcarriers of OFDM systems is impaired. The average ICI power and its distribution are obtained based on the general time-variant frequency-selective WSSUS fading channel model. To mitigate the ICI caused by the channel time-selectivity for OFDM systems, in the second part of this study, an efficient ICI cancellation scheme is designed based on the obtained ICI power distribution. The simulation results indicate that a significant performance improvement can be achieved. For OFDM systems, differential encoding can be performed not only between the information bits of the same subcarrier of the consecutive OFDM symbols (inter-frame differential encoding), but also between the information bits of the adjacent subcarriers of the same OFDM symbol (inter-carrier differential encoding). In the third part of this study, we compare the performance of inter-frame and inter-carrier differential detection for OFDM systems over multipath time-variant mobile fading channels. The objective is to identify which differential encoding scheme (inter-frame or inter-carrier) is more robust to the channel time-selectivity, when OFDM systems are experiencing both frequency-selective and time-selective fading. The conditions under which the inter-carrier differential encoding outperforms the inter-frame differential encoding and vice-versa are provided.

Download or read book Avoiding Effects of OFDM Adjacent Channel Interference by Using Combinations of Modulation Schemes written by Le Tien Anh and published by GRIN Verlag. This book was released on 2009-05 with total page 89 pages. Available in PDF, EPUB and Kindle. Book excerpt: Master's Thesis from the year 2008 in the subject Engineering - Communication Technology, grade: erfolgreich bestanden, Keio University (Graduate school of Science and Technology - School of Science for Open and Environmental Systems), language: English, abstract: Non-orthogonality among adjacent OFDM channels creates OFDM adjacent channel interference and it heavily affects the entire system's performance. Conventional methods to avoid OFDM adjacent channel interference are not only insufficient but also are wasting a lot of frequency resources. In this research, a method using combinations of modulation schemes is proposed to avoid effects of OFDM adjacent channel interference. It can be obtained by modulating the sub-carriers at the outer sides of an OFDM channel with lower order modulation schemes (such as BPSK or QPSK), while modulating the sub-carriers at the inner side of the OFDM channel with higher order modulation schemes (such as 16QAM or 64QAM). Intensive simulations have been carried out to evaluate the performance of the proposed method. The simulation results have shown an increase in the OFDM system's resistance against adjacent channel interference while still maintain the bandwidth efficiency.

Download or read book Intercarrier Interference Suppression for the OFDM Systems in Time varying Multipath Fading Channels written by Xiaozhou Huang and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Wireless Communications Systems Design written by Haesik Kim and published by John Wiley & Sons. This book was released on 2015-08-06 with total page 434 pages. Available in PDF, EPUB and Kindle. Book excerpt: em style="mso-bidi-font-style: normal;"Wireless Communications Systems Design provides the basic knowledge and methodology for wireless communications design. The book mainly focuses on a broadband wireless communication system based on OFDM/OFDMA system because it is widely used in the modern wireless communication system. It is divided into three parts: wireless communication theory (part I), wireless communication block design (part II), and wireless communication block integration (part III). Written by an expert with various experience in system design (standards, research and development)

Download or read book Mobile Fading Channels written by Matthias Pätzold and published by Wiley-Blackwell. This book was released on 2002-04 with total page 440 pages. Available in PDF, EPUB and Kindle. Book excerpt: Mobile channel fading is a loss in transmission intensity caused by changes in the transmission medium. By dealing with the modelling, analysis and simulation of mobile fading channels this text provides a fundamental understanding of many issues in the area of mobile fading channel modelling.; The main topics addressed in the volume are: fundamentals of stochastic and deterministic channel models and modelling and simulation of frequency-nonselective and frequency-selective fading channels. The guide also features methods for the design and realization of efficient channel simulators and fast channel simulators and MATLAB-programs for the evaluation and simulation of mobile fading channels.

Download or read book Interference Rejection and Management written by and published by . This book was released on 2009 with total page 35 pages. Available in PDF, EPUB and Kindle. Book excerpt: We consider interference suppression in several wireless communication systems. The first topic treated is self-interference encountered among cooperating systems, for example, the self-interference that is encountered in cognitive radio systems and ultra-wideband (UWB) communication systems. Both single-carrier, direct sequence signals and multicarrier signals are considered, and the effects of the interference on the performance of a direct sequence UWB system that employs channel state estimation in the presence of the interference is evaluated. The second topic that is treated is the mitigation of narrowband interference in block-modulated multicarrier systems. Two schemes, multicarrier code-division multiple access (MC-CDMA) and orthogonal frequency division multiplexing (OFDM), are investigated. The inherent frequency diversity of MC-CDMA through the use of spreading codes allows for robustness against interference. Conversely, OFDM must employ a signal processing technique to suppress the interference due to its lack of frequency diversity. The performance of OFDM is improved with the addition of forward error correction (FEC) coding in the frequency domain, thereby providing the system with frequency diversity. The third topic is the suppression of interference in multiple input, multiple output (MIMO) wireless communication systems that employ multiple-transmit and multiple-receive antennas to increase the data rate and achieve signal diversity in fading multipath channels. Interference in MIMO wireless communication systems usually consists of intersymbol interference (ISI) due to channel multipath dispersion and cross-talk, or interchannel interference, due to the simultaneous transmissions from the multiple-transmit antennas. The focus of the section is on point-to-multipoint (broadcast) MIMO systems in which the channel characteristics are assumed to be known at the transmitter, so that interference mitigation can be performed at the transmitter.

Download or read book Interference Modeling and Performance Analysis of Asynchronous OFDM and FBMC Wireless Communication Systems written by Yahia Medjahdi and published by . This book was released on 2012 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Multicarrier systems are widely used today due to their robustness to multipath effects and efficient implementation using FFT. Orthogonal Frequency Division Multiplexing (OFDM) system is a class of multicarrier modulation which consists of splitting up a wide-band signal at a high symbol rate into several lower rate signals, each one occupying a narrower band. System performance improves because subcarriers experience flat fading channels and are orthogonal to one another. Recently, a number of papers have focused on a new alternative called Filter bank based multicarrier system (FBMC) which can offer a number of advantages over CP-OFDM system such as the improved spectral efficiency by not using a redundant CP and by having much better control of the out-of-band emission due to the time-frequency localized shaping pulses.Furthermore, asynchronism inherently exists in several communication systems due to many factors e.g. the propagation delays and the spatial distribution of users. As one of the most challenging issue in design of communication systems, the asynchronism can harmfully affect the system performance by causing the so-called asynchronous interference.In this dissertation, we investigate the impact of asynchronism on the performance of OFDM FBMC systems. First, we present a unified framework for multicarrier interference characterization and analysis in asynchronous environments. We propose a new family of interference tables that model the correlation between a given interfering subcarrier and the victim one, not only as a function of the spectral distance separating both subcarriers but also with respect to the timing misalignment between the subcarriers holders. These tables are derived for CP-OFDM, PHYDYAS-FBMC and IOTA-FBMC systems. Furthermore, the impact of the asynchronous interference on the average error rate and the average spectral efficiency of OFDM and FBMC systems is addressed. Based on computing the moment generating functions of the asynchronous interference power, simple new expressions for the exact evaluation of the average error rate and the average spectral efficiency are derived considering the frequency correlation fading between adjacent interfering subcarriers. These expressions significantly reduce the computation complexity of the performance evaluation.For each technique two scenarios are examined: fully-loaded network and partially loaded ones. The accuracy of the obtained expressions has been validated through different simulation results. In contrast to OFDM, FBMC waveforms are demonstrated to be less sensitive to timing asynchronism, due to the better frequency localization of the used prototype filters.

Download or read book Wireless Communications Over Rapidly Time Varying Channels written by Franz Hlawatsch and published by Academic Press. This book was released on 2011-05-04 with total page 457 pages. Available in PDF, EPUB and Kindle. Book excerpt: As a result of higher frequencies and increased user mobility, researchers and systems designers are shifting their focus from time-invariant models to channels that vary within a block. Wireless Communications Over Rapidly Time-Varying Channels explains the latest theoretical advances and practical methods to give an understanding of rapidly time varying channels, together with performance trade-offs and potential performance gains, providing the expertise to develop future wireless systems technology. As well as an overview of the issues of developing wireless systems using time-varying channels, the book gives extensive coverage to methods for estimating and equalizing rapidly time-varying channels, including a discussion of training data optimization, as well as providing models and transceiver methods for time-varying ultra-wideband channels. An introduction to time-varying channel models gives in a nutshell the important issues of developing wireless systems technology using time-varying channels Extensive coverage of methods for estimating and equalizing rapidly time-varying channels, including a discussion of training data optimization, enables development of high performance wireless systems Chapters on transceiver design for OFDM and receiver algorithms for MIMO communication channels over time-varying channels, with an emphasis on modern iterative turbo-style architectures, demonstrates how these important technologies can optimize future wireless systems

Download or read book RF Imperfections in High rate Wireless Systems written by Tim Schenk and published by Springer Science & Business Media. This book was released on 2008-01-29 with total page 323 pages. Available in PDF, EPUB and Kindle. Book excerpt: This is one of the first books on the emerging research topic of digital compensation of RF imperfections. The book presents a new multidisciplinary vision on the design of wireless communication systems. In this approach the imperfections of the RF front-ends are accepted and digital signal processing algorithms are designed to suppress their impact on system performance. The book focuses on multiple-antenna orthogonal frequency division multiplexing (MIMO OFDM).

Download or read book A Performance Analysis of MIMO OFDM TDM in a Peak limited Multipath Fading Channel written by Amir Ligata and published by . This book was released on 2012 with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Analysis of Wideband Interference in Spread Spectrum Communication Systems written by Giridhar Venkat and published by . This book was released on 2010 with total page 100 pages. Available in PDF, EPUB and Kindle. Book excerpt: With the increasing density of communications systems in the wireless spectrum, the ability for two communications systems to share the same frequency space will become critical. To accommodate this, it becomes necessary to understand the nature of impairments introduced when two systems share the same spectrum. Traditionally, the performance of a communication system is analyzed in the presence of random interfering noise (Gaussian, Rayleigh, etc.), specific channel impairments like multipath or fading, or narrowband interferers. This work will focus solely on the wideband interference of one communication system on another. Wireless communications systems are increasingly bifurcating along two primary paths: OFDM and Spread Spectrum. This thesis will analyze three parameters of an OFDM system to understand their impact on a forward-path, single-transmitter DSSS system, both analytically and empirically. Ultimately, the effect of these parameters on probability of error and a method to reject the interference of each system on the other will be presented.

Download or read book Fundamentals of Wireless Communication written by David Tse and published by Cambridge University Press. This book was released on 2005-05-26 with total page 598 pages. Available in PDF, EPUB and Kindle. Book excerpt: This textbook takes a unified view of the fundamentals of wireless communication and explains cutting-edge concepts in a simple and intuitive way. An abundant supply of exercises make it ideal for graduate courses in electrical and computer engineering and it will also be of great interest to practising engineers.

Download or read book Performance Analysis of Two branch Transmit Diversity Block Coded OFDM Systems in Time varying Multipath Rayleigh Fading Channels written by Ding-bing Lin and published by . This book was released on 2005 with total page 26 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Analysis of Multipath Fading Effects written by Ronald N. Isaac and published by . This book was released on 1999 with total page 138 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Analysis of Intersymbol Interference in Fading Channels written by Jorge Valerdi and published by . This book was released on 1972 with total page 274 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Estimation of Multipath Fading Channels for Carrier Aggregation OFDM Systems Based on Parametric Channel Modeling written by 鄭舜文 and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: