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Channel Estimation For Ofdm In Fast Fading Channels
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Book Synopsis Channel Estimation for OFDM in Fast Fading Channels by : Ping Wan
Download or read book Channel Estimation for OFDM in Fast Fading Channels written by Ping Wan and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The increasing demand for high data rate transmission over broadband radio channels has imposed significant challenges in wireless communications. Accurate channel estimation has a major impact onthe whole system performance. Specifically, reliable estimate of the channel state information (CSI) is more challenging for orthogonal frequency division multiplexing (OFDM) systems in doubly selective fading channels than for the slower fading channels over which OFDM has been deployed traditionally. With the help of a basis expansion model (BEM), a novel multivariate autoregressive (AR) process is developed to model the time evolution of the fast fading channel. Relying on pilot symbol aided modulation (PSAM), a novel Kalman smoothing algorithm based on a second-order dynamic model is exploited, where the mean square error (MSE) of the channel estimator is near to that of the optimal Wiener filter. To further improve the performance of channel estimation, a novellow-complexity iterative joint channel estimation and symbol detection procedure is developed for fast fading channels with a small number of pilots and low pilot power to achieve the bit errorrate (BER) performance close to when the CSI is known perfectly. The new channel estimation symbol detection technique is robust to variations of the radio channel from the design values and applicable to multiple modulation and coding types. By use of the extrinsic information transfer (EXIT) chart, we investigate the convergence behavior of the new algorithm and analyze the modulation, pilot density, and error correction code selection for good system performance for a given power level. The algorithms developed in this thesis improve the performance of the whole system requiring only low ratios of pilot to data for excellent performance in fast fading channels.
Book Synopsis Code Assisted Iterative Channel Estimation for OFDM Systems Over Multipath Fast-fading Channels by : 陳薏如
Download or read book Code Assisted Iterative Channel Estimation for OFDM Systems Over Multipath Fast-fading Channels written by 陳薏如 and published by . This book was released on 2020 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Channel Estimation for OFDM in Fast Fading Channels by : Ping Wan
Download or read book Channel Estimation for OFDM in Fast Fading Channels written by Ping Wan and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Signal Detection and Channel Estimation for HDS-OFDM Systems Over Multipath Fast-fading Channels by : 陳俊宇
Download or read book Signal Detection and Channel Estimation for HDS-OFDM Systems Over Multipath Fast-fading Channels written by 陳俊宇 and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Performance Analysis of DFT Based Channel Estimation in OFDM System by : Md. Muktar Hossain
Download or read book Performance Analysis of DFT Based Channel Estimation in OFDM System written by Md. Muktar Hossain and published by LAP Lambert Academic Publishing. This book was released on 2014-08-26 with total page 60 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this book the channel estimation techniques for OFDM systems based on Block Type Pilot arrangement are investigated. Finally, the DFT based channel estimation technique is performed which gives better performance over LS and MMSE based channel estimation.With same SNR, the BER of DFT based channel estimation is less than the BER of LS and MMSE based channel estimation. The MMSE estimator has good performance but high complexity. The LS estimator has low complexity, but its performance is not as good as that MMSE estimator basically at low SNR. Block Type Pilot arrangement is suitable for frequency-selective channels. For the fast-fading channels, however, it might incur too much overhead to track the channel variation by reducing the pilot symbol period.As the use of pilot symbols for channel estimation decrease the spectrum efficiency of the wireless communication systems, it will be beneficial if we can adaptively change the number of pilot tones depending on the channel condition through some feedback information.
Book Synopsis Wireless Communications Over Rapidly Time-Varying Channels by : Franz Hlawatsch
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
Book Synopsis Improved Channel Estimation Techniques for OFDM Systems in Frequency Selective Fading Channels by : Wichai Pongwilai
Download or read book Improved Channel Estimation Techniques for OFDM Systems in Frequency Selective Fading Channels written by Wichai Pongwilai and published by . This book was released on 2004 with total page 306 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Simplified Channel Estimation Techniques for OFDM Systems with Realistic Indoor Fading Channels by : Jake Hwang
Download or read book Simplified Channel Estimation Techniques for OFDM Systems with Realistic Indoor Fading Channels written by Jake Hwang and published by . This book was released on 2009 with total page 65 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation deals with the channel estimation techniques for orthogonal frequency division multiplexing (OFDM) systems such as in IEEE 802.11. Although there has been a great amount of research in this area, characterization of typical wireless indoor environments and design of channel estimation schemes that are both robust and practical for such channel conditions have not been thoroughly investigated. It is well known that the minimum mean-square-error (MMSE) estimator provides the best mean-square-error (MSE) performance given a priori knowledge of channel statistics and operating signal-to-noise ratio (SNR). However, the channel statistics are usually unknown and the MMSE estimator has too much computational complexity to be realized in practical systems. In this work, we propose two simple channel estimation techniques: one that is based on modifying the channel correlation matrix from the MMSE estimator and the other one with averaging window based on the LS estimates. We also study the characteristics of several realistic indoor channel models that are of potential use for wireless local area networks (LANs). The first method, namely MMSE-exponential-Rhh, does not depend heavily on the channel statistics and yet offer performance improvement compared to that of the LS estimator. The simulation results also show that the second method, namely averaging window (AW) estimator, provides the best performance at moderate SNR range.
Book Synopsis Introduction to OFDM Receiver Design and Simulation by : Y.J. Liu
Download or read book Introduction to OFDM Receiver Design and Simulation written by Y.J. Liu and published by Artech House. This book was released on 2019-11-30 with total page 273 pages. Available in PDF, EPUB and Kindle. Book excerpt: This practical book is an accessible introduction to Orthogonal frequency-division multiplexing (OFDM) receiver design, a technology that allows digitized data to be carried by multiple carriers. It offers a detailed simulation study of an OFDM algorithm for Wi-Fi and 4G cellular that can be used to understand other OFDM waveforms. Extensive simulation studies are included using the transmissionwaveform given by the IEEE 802.11 standard. Scrambler, error-correcting codes, interleaver and radio-wave propagation model are included. OFDM waveform characteristics, signal acquisition, synchronization issues, channel estimation and tracking, hard and soft decision decoding are all covered. Detailed derivations leading to the final formula for any algorithm are given, which allows the reader to clearly understand the approximations and conditions behind the formulas and apply them appropriately. The algorithms are selected not just for the best performance from simulation study but also for easy implementation. An example is a unique algorithm for signal acquisition using the principle of maximum likelihood detection.
Book Synopsis Intelligent Multi-Modal Data Processing by : Soham Sarkar
Download or read book Intelligent Multi-Modal Data Processing written by Soham Sarkar and published by John Wiley & Sons. This book was released on 2021-04-06 with total page 288 pages. Available in PDF, EPUB and Kindle. Book excerpt: A comprehensive review of the most recent applications of intelligent multi-modal data processing Intelligent Multi-Modal Data Processing contains a review of the most recent applications of data processing. The Editors and contributors – noted experts on the topic – offer a review of the new and challenging areas of multimedia data processing as well as state-of-the-art algorithms to solve the problems in an intelligent manner. The text provides a clear understanding of the real-life implementation of different statistical theories and explains how to implement various statistical theories. Intelligent Multi-Modal Data Processing is an authoritative guide for developing innovative research ideas for interdisciplinary research practices. Designed as a practical resource, the book contains tables to compare statistical analysis results of a novel technique to that of the state-of-the-art techniques and illustrations in the form of algorithms to establish a pre-processing and/or post-processing technique for model building. The book also contains images that show the efficiency of the algorithm on standard data set. This important book: Includes an in-depth analysis of the state-of-the-art applications of signal and data processing Contains contributions from noted experts in the field Offers information on hybrid differential evolution for optimal multilevel image thresholding Presents a fuzzy decision based multi-objective evolutionary method for video summarisation Written for students of technology and management, computer scientists and professionals in information technology, Intelligent Multi-Modal Data Processing brings together in one volume the range of multi-modal data processing.
Book Synopsis Iterative Estimation and Decoding for OFDM Systems in Fast-fading Channels by : Taehyuk Kang
Download or read book Iterative Estimation and Decoding for OFDM Systems in Fast-fading Channels written by Taehyuk Kang and published by . This book was released on 2009 with total page 308 pages. Available in PDF, EPUB and Kindle. Book excerpt: The proposed receivers in this dissertation leverage iterative processing. The architecture of iterative processing based on the Turbo principle can be summarized as separate estimation/detection and decoding blocks exchanging information for mutual performance improvement. Within the iterative structure, we first develop sequential and joint estimators for CFO and multipath channel coefficients. More efficient estimators are then developed for sparse channels. Finally, the optimal power allocation between pilots and data for the OFDM iterative receiver is investigated using the EXIT chart. We show that the optimal power allocation strategy can be quite different for the iterative versus non-iterative receiver. The proposed system is implemented in hardware and underwater field tests are conducted. The successful underwater test results show the effectiveness of the proposed receiver.
Book Synopsis Channel Estimation and Equalization Techniques by : Vijay Nomula
Download or read book Channel Estimation and Equalization Techniques written by Vijay Nomula and published by . This book was released on 2006 with total page 292 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis MIMO-OFDM Wireless Communications with MATLAB by : Yong Soo Cho
Download or read book MIMO-OFDM Wireless Communications with MATLAB written by Yong Soo Cho and published by John Wiley & Sons. This book was released on 2010-08-20 with total page 458 pages. Available in PDF, EPUB and Kindle. Book excerpt: MIMO-OFDM is a key technology for next-generation cellular communications (3GPP-LTE, Mobile WiMAX, IMT-Advanced) as well as wireless LAN (IEEE 802.11a, IEEE 802.11n), wireless PAN (MB-OFDM), and broadcasting (DAB, DVB, DMB). In MIMO-OFDM Wireless Communications with MATLAB®, the authors provide a comprehensive introduction to the theory and practice of wireless channel modeling, OFDM, and MIMO, using MATLAB® programs to simulate the various techniques on MIMO-OFDM systems. One of the only books in the area dedicated to explaining simulation aspects Covers implementation to help cement the key concepts Uses materials that have been classroom-tested in numerous universities Provides the analytic solutions and practical examples with downloadable MATLAB® codes Simulation examples based on actual industry and research projects Presentation slides with key equations and figures for instructor use MIMO-OFDM Wireless Communications with MATLAB® is a key text for graduate students in wireless communications. Professionals and technicians in wireless communication fields, graduate students in signal processing, as well as senior undergraduates majoring in wireless communications will find this book a practical introduction to the MIMO-OFDM techniques. Instructor materials and MATLAB® code examples available for download at www.wiley.com/go/chomimo
Book Synopsis Design of Channel Estimation and Equalization for OFDM Systems by : Ali Salah Mahdi
Download or read book Design of Channel Estimation and Equalization for OFDM Systems written by Ali Salah Mahdi and published by LAP Lambert Academic Publishing. This book was released on 2015-01-20 with total page 84 pages. Available in PDF, EPUB and Kindle. Book excerpt: Orthogonal Frequency Division Multiplexing (OFDM) system is one of the multicarrier techniques which is robust against Inter-symbol-Interference, multipath fading and very easy to apply in transmitters by using inverse fast Fourier transform IFFT and at the receivers by using fast Fourier transform FFT. In a communication system, channel estimation is very important issue for the data detection. In coherent detection, one of the popular techniques is to use pilot tones as a reference signal in OFDM symbols. In the comb-type pilot tones insertion, pilot tones are inserted into each OFDM symbols, but inserting a large number of pilot tones will lead to channel capacity reduction or bandwidth expansion [1-2]. In this work, to overcome this transmission loss, a modified least square (ModLS) algorithm for fast time varying wireless channel at comb-type pilot arrangement in QAM signals for OFDM system is proposed. The simulation results obtained from the proposed algorithm showed a good performance in noisy wireless channels. In addition, it has been compared with least square (LS) algorithm in different signal to noise ratios and different channel tabs.
Book Synopsis Channel Estimation in Multicarrier Communication Systems by :
Download or read book Channel Estimation in Multicarrier Communication Systems written by and published by . This book was released on with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The data rate and spectrum efficiency of wireless mobile communications have been significantly improved over the last decade or so. Recently, the advanced systems such as 3GPP LTE and terrestrial digital TV broadcasting have been sophisticatedly developed using OFDM and CDMA technology. In general, most mobile communication systems transmit bits of information in the radio space to the receiver. The radio channels in mobile radio systems are usually multipath fading channels, which cause inter-symbol interference (ISI) in the received signal. To remove ISI from the signal, there is a need of strong equalizer which requires knowledge on the channel impulse response (CIR). This is primarily provided by a separate channel estimator. Usually the channel estimation is based on the known sequence of bits, which is unique for a certain transmitter and which is repeated in every transmission burst. Thus, the channel estimator is able to estimate CIR for each burst separately by exploiting the known transmitted bits and the corresponding received samples. In this thesis we investigate and compare various efficient channel estimation schemes for OFDM systems which can also be extended to MC DS-CDMA systems. The channel estimation can be performed by either inserting pilot tones into all subcarriers of OFDM symbols with a specific period or inserting pilot tones into each OFDM symbol. Two major types of pilot arrangement such as block type and comb type pilot have been focused employing Least Square Error (LSE) and Minimum Mean Square Error (MMSE) channel estimators. Block type pilot sub-carriers is especially suitable for slow-fading radio channels whereas comb type pilots provide better resistance to fast fading channels. Also comb type pilot arrangement is sensitive to frequency selectivity when comparing to block type arrangement. However, there is another supervised technique called Implicit Training (IT) based channel estimation which exploits the first order statistics i.
Download or read book LDPC-OFDM written by Basel Nabulsi and published by . This book was released on 2013 with total page 282 pages. Available in PDF, EPUB and Kindle. Book excerpt: Small cells are low-powered radio access nodes that operate in licensed and unlicensed spectrum that have a range of 10 meters to 200 meters, compared to a mobile macrocell which might have a range of a few kilometres. This dissertation proposes algorithms for the enhancement of small cells installed in high speed rails. The thesis addresses two main points: the link between the small cell and the base station, and the link between the end-users and the small cell. The channel between the small cell and the base station is a fast fading channel due to the mobility of the high speed rail. The first part of the thesis proposes methods to enhance the link between the small cell and the base station using Low-Density Parity-Check codes (LDPC) for fast fading channels. The proposed uses nonuniform reconstruction methods based on the soft output log-likelihood ratio (LLR) provided by the LDPC decoder. The LLRs provide information about the location of the symbols with high probability of being correct. The grid formed under the assumption of a correlated Rayleigh channel affecting the transmitted data is highly nonuniform. Reconstruction of the channel under such assumptions is highly unstable. A signal-to-noise- ratio dependent regularization method is implemented to enhance the performance under imperfect Doppler spread estimation. The second part of the thesis proposes algorithms for the link between the end-user and the small cell. Since power efficiency is a major factor for end-users employing battery powered devices, we propose a Linear Programming (LP) algorithm for signal shaping to minimize the average transmitted power. The other problem the thesis addresses is the minimization of Peak-to-Average Power-Ratio (PAPR) of Orthogonal Frequency Division Multiplexing (OFDM) signals. The PAPR is minimized using a set of phase shifts for the constituting subcarriers of the OFDM signal. The set of phase shifts is determined using a LP approach that minimizes the complexity when the block length is high. A real-time implementation of some of the algorithms is carried out using the TMS320C6713 Texas Instruments board. The results for fixed-point versus floating-point implementation is shown for a different number of precision bits.
Book Synopsis Multi-Carrier Digital Communications by : Ahmad R.S. Bahai
Download or read book Multi-Carrier Digital Communications written by Ahmad R.S. Bahai and published by Springer Science & Business Media. This book was released on 2006-04-11 with total page 224 pages. Available in PDF, EPUB and Kindle. Book excerpt: Multi-carrier modulation, in particular orthogonal frequency division multiplexing (OFDM), has been successfully applied to a wide variety of digital communications applications for several years. Although OFDM has been chosen as the physical layer standard for a diversity of important systems, the theory, algorithms, and implementation techniques remain subjects of current interest. This book is intended to be a concise summary of the present state of the art of the theory and practice of OFDM technology. This book offers a unified presentation of OFDM theory and high speed and wireless applications. In particular, ADSL, wireless LAN, and digital broadcasting technologies are explained. It is hoped that this book will prove valuable both to developers of such systems, and to researchers and graduate students involved in analysis of digital communications, and will remain a valuable summary of the technology, providing an understanding of new advances as well as the present core technology.
