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Author: Bulent Karaoglu Publisher: ISBN: 9781423586876 Category : Languages : en Pages : 65
Book Description
OFDM is a modulation technique that achieves high data rates, increased bandwidth efficiency and robustness in multipath environments. However, OFDM has some disadvantages, such as sensitivity to channel fading, large peak to average ratio and sensitivity to frequency offset. The latter causes intercarrier interference (ICI) and a reduction in the amplitude of the desired subcarrier which results in loss of orthogonality. In this thesis, the effects of frequency offset are studied in terms of loss of orthogonality. A number of techniques for frequency offset estimation are presented and tested in computer simulations.
Author: Bulent Karaoglu Publisher: ISBN: 9781423586876 Category : Languages : en Pages : 65
Book Description
OFDM is a modulation technique that achieves high data rates, increased bandwidth efficiency and robustness in multipath environments. However, OFDM has some disadvantages, such as sensitivity to channel fading, large peak to average ratio and sensitivity to frequency offset. The latter causes intercarrier interference (ICI) and a reduction in the amplitude of the desired subcarrier which results in loss of orthogonality. In this thesis, the effects of frequency offset are studied in terms of loss of orthogonality. A number of techniques for frequency offset estimation are presented and tested in computer simulations.
Author: Yufei Jiang Publisher: Springer ISBN: 3319249843 Category : Computers Languages : en Pages : 96
Book Description
This SpringerBrief investigates the performance of semi-blind independent component analysis (ICA) based equalization and carrier frequency offset estimation approaches (CFO) for a number of orthogonal frequency division multiplexing (OFDM) based wireless communication systems. It provides a comprehensive overview of the challenges of channel equalization and frequency synchronization for different wireless systems. The authors present the wireless communication channel and system models. Key existing CFO estimation methods are reviewed, along with a number of the training based and non-training based (blind) channel estimation methods. This is followed by a study of ICA and its applications to OFDM-based wireless communication systems. Later chapters provide a detailed description of recent research on semi-blind CFO estimation and ICA based equalization approaches for various wireless communication systems including multiple-input multiple-output (MIMO) OFDM and coordinated multipoint (CoMP) systems. Semi-blind CFO estimation and equalization structures provide a spectrum-efficient and high-performance solution for high speed wireless communications. This book is suitable for postgraduate students, researchers or professionals in the area of wireless communications.
Author: Santosh Gupta Publisher: LAP Lambert Academic Publishing ISBN: 9783659235856 Category : Languages : en Pages : 72
Book Description
The most important aspect in an OFDM is frequency and time synchronization as this form the reason for orthogonality between the subcarriers. However OFDM is susceptible to synchronization errors between transmitter and receiver local oscillator frequencies. This error is known as the carrier frequency offset (CFO) and causes ICI and also destroys the orthogonality between the subcarriers. In this literature we study the effects that CFO can cause to the SNR in an OFDM system, estimate the amount of frequency offset. Also the performance of the estimate is studied in a multipath environment. This book discusses and investigates the estimation of carrier offset frequency in orthogonal frequency division multiplexing (OFDM) mobile systems. Although OFDM is resistant to multipath fading, it requires a high degree of synchronization to maintain sub-carrier orthogonality. Therefore the level of performance of the system depends first on the accuracy in estimating the carrier frequency offset and then the estimation of the channel.
Author: Ye Geoffrey Li Publisher: Springer Science & Business Media ISBN: 0387302352 Category : Technology & Engineering Languages : en Pages : 314
Book Description
Orthogonal Frequency Division Multiplexing for Wireless Communications is an edited volume with contributions by leading authorities in the subject of OFDM. Its coverage consists of principles, important wireless topics (e.g. Synchronization, channel estimation, etc.) and techniques. Included is information for advancing wireless communication in a multipath environment with an emphasis on implementation of OFDM in base stations. Orthogonal Frequency Division Multiplexing for Wireless Communications provides a comprehensive introduction of the theory and practice of OFDM. To facilitate the readers, extensive subject indices and references are given at the end of the book. Even though each chapter is written by different experts, symbols and notations in all chapters of the book are consistent.
Author: Jennifer S. Raj Publisher: Springer Nature ISBN: 3030380408 Category : Computers Languages : en Pages : 852
Book Description
This book presents emerging concepts in data mining, big data analysis, communication, and networking technologies, and discusses the state-of-the-art in data engineering practices to tackle massive data distributions in smart networked environments. It also provides insights into potential data distribution challenges in ubiquitous data-driven networks, highlighting research on the theoretical and systematic framework for analyzing, testing and designing intelligent data analysis models for evolving communication frameworks. Further, the book showcases the latest developments in wireless sensor networks, cloud computing, mobile network, autonomous systems, cryptography, automation, and other communication and networking technologies. In addition, it addresses data security, privacy and trust, wireless networks, data classification, data prediction, performance analysis, data validation and verification models, machine learning, sentiment analysis, and various data analysis techniques.
Author: Hamed Abdzadeh Ziabari Publisher: ISBN: Category : Languages : en Pages : 176
Book Description
Orthogonal frequency division multiplexing (OFDM) due to its appealing features, such as robustness against frequency selective fading and simple channel equalization, is adopted in communications systems such as WLAN, WiMAX and DVB. However, OFDM systems are sensitive to synchronization errors caused by timing and frequency offsets. Besides, the OFDM receiver has to perform channel estimation for coherent detection. The goal of this thesis is to investigate new methods for timing and frequency synchronization and channel estimation in OFDM-based systems. First, we investigate new methods for preamble-aided coarse timing estimation in OFDM systems. Two novel timing metrics using high order statistics-based correlation and differential normalization functions are proposed. The performance of the new timing metrics is evaluated using different criteria including class-separability, robustness to the carrier frequency offset, and computational complexity. It is shown that the new timing metrics can considerably increase the class-separability due to their more distinct values at correct and wrong timing instants, and thus give a significantly better detection performance than the existing timing metrics do. Furthermore, a new method for coarse estimation of the start of the frame is proposed, which remarkably reduces the probability of inter-symbol interference (ISI). The improved performances of the new schemes in multipath fading channels are shown by the probabilities of false alarm, missed-detection and ISI obtained through computer simulations. Second, a novel pilot-aided algorithm is proposed for the detection of integer frequency offset (IFO) in OFDM systems. By transforming the IFO into two new integer parameters, the proposed method can largely reduce the number of trial values for the true IFO. The two new integer parameters are detected using two different pilot sequences, a periodic pilot sequence and an aperiodic pilot sequence. It is shown that the new scheme can significantly reduce the computational complexity while achieving almost the same performance as the previous methods do. Third, we propose a method for joint timing and frequency synchronization and channel estimation for OFDM systems that operate in doubly selective channels. Basis expansion modeling (BEM) that captures the time variations of the channel is used to reduce the number of unknown channel parameters. The BEM coefficients along with the timing and frequency offsets are estimated by using a maximum likelihood (ML) approach. An efficient algorithm is then proposed for reducing the computational complexity of the joint estimation. The complexity of the new method is assessed in terms of the number of multiplications. The mean square estimation error of the proposed method is evaluated in comparison with previous methods, indicating a remarkable performance improvement by the new method. Fourth, we present a new scheme for joint estimation of CFO and doubly selective channel in orthogonal frequency division multiplexing systems. In the proposed preamble-aided method, the time-varying channel is represented using BEM. CFO and BEM coefficients are estimated using the principles of particle and Kalman filtering. The performance of the new method in multipath time-varying channels is investigated in comparison with previous schemes. The simulation results indicate a remarkable performance improvement in terms of the mean square errors of CFO and channel estimates. Fifth, a novel algorithm is proposed for timing and frequency synchronization and channel estimation in the uplink of orthogonal frequency division multiple access (OFDMA) systems by considering high-mobility situations and the generalized subcarrier assignment. By using BEM to represent a doubly selective channel, a maximum likelihood (ML) approach is proposed to jointly estimate the timing and frequency offsets of different users as well as the BEM coefficients of the time-varying channels. A space-alternating generalized expectation-maximization algorithm is then employed to transform the maximization problem for all users into several simpler maximization problems for each user. The computational complexity of the new timing and frequency offset estimator is analyzed and its performance in comparison with that of existing methods using the mean square error is evaluated . Finally, two novel approaches for joint CFO and doubly selective channel estimation in the uplink of multiple-input multiple-output orthogonal frequency division multiple access (MIMO-OFDMA) systems are presented. Considering high-mobility situations, where channels change within an OFDMA symbol interval, and the time varying nature of CFOs, BEM is employed to represent the time variations of the channel. Two new approaches are then proposed based on Schmidt Kalman filtering (SKF). The first approach utilizes Schmidt extended Kalman filtering for each user to estimate the CFO and BEM coefficients. The second approach uses Gaussian particle filter along with SKF to estimate the CFO and BEM coefficients of each user. The Bayesian Cramer Rao bound is derived, and performance of the new schemes are evaluated using mean square error. It is demonstrated that the new schemes can significantly improve the mean square error performance in comparison with that of the existing methods.
Author: Khoa N. Le Publisher: Bentham Science Publishers ISBN: 1608051889 Category : Computers Languages : en Pages : 621
Book Description
"The book examines several aspects of Orthogonal Frequency Division Multiplexing (OFDM) employing linear diversity techniques such as inter-carrier interference, bit error rate, peak to average power and inter-block interference. It should be a useful refe"
Author: Javad Hoseyni Publisher: LAP Lambert Academic Publishing ISBN: 9783659376023 Category : Languages : en Pages : 96
Book Description
Orthogonal Frequency Division Multiplexing (OFDM) is a popular multicarrier modulation technique with the ability to provide high data rates over echo-ladened channels. It has excellent robustness to impairments caused by multipath, which includes frequency selective fading. Unfortunately, OFDM is very sensitive to the carrier frequency o set (CFO) that is introduced by the down conversion process. The objective of this book is to develop and analyze an algorithm for blind CFO recovery suitable for use with a practical zero-Intermediate Frequency (zero-IF) OFDM telecommunications system. A blind CFO recovery algorithm based upon characteristics of the received signal power spectrum is proposed. The algorithm's error performance is mathematically analyzed and the theoretical results are veri ed with simulations. The simulation shows that the performance of the proposed algorithm agrees with the mathematical analysis. The proposed algorithm performs well in comparison and does not su er from many of the disadvantages of existing blind CFO recovery techniques. Most notably, its performance is not signi cantly degraded by noisy, frequency selective channels."
Author: Bulent Karaoglu
Author: Bulent Karaoglu
Author: Xiangnian Zeng
Author: Yufei Jiang
Author: Santosh Gupta
Author: Ye Geoffrey Li
Author: Jennifer S. Raj
Author: Hamed Abdzadeh Ziabari
Author: Khoa N. Le
Author: Javad Hoseyni
Author: 黃紀霖