Download or read book OFDM and MC CDMA for Broadband Multi User Communications WLANs and Broadcasting written by Lajos Hanzo and published by John Wiley & Sons. This book was released on 2005-01-28 with total page 1014 pages. Available in PDF, EPUB and Kindle. Book excerpt: Orthogonal frequency-division multiplexing (OFDM) is a method of digital modulation in which a signal is split into several narrowband channels at different frequencies. CDMA is a form of multiplexing, which allows numerous signals to occupy a single transmission channel, optimising the use of available bandwidth. Multiplexing is sending multiple signals or streams of information on a carrier at the same time in the form of a single, complex signal and then recovering the separate signals at the receiving end. Multi-Carrier (MC) CDMA is a combined technique of Direct Sequence (DS) CDMA (Code Division Multiple Access) and OFDM techniques. It applies spreading sequences in the frequency domain. Wireless communications has witnessed a tremendous growth during the past decade and further spectacular enabling technology advances are expected in an effort to render ubiquitous wireless connectivity a reality. This technical in-depth book is unique in its detailed exposure of OFDM, MIMO-OFDM and MC-CDMA. A further attraction of the joint treatment of these topics is that it allows the reader to view their design trade-offs in a comparative context. Divided into three main parts: Part I provides a detailed exposure of OFDM designed for employment in various applications Part II is another design alternative applicable in the context of OFDM systems where the channel quality fluctuations observed are averaged out with the aid of frequency-domain spreading codes, which leads to the concept of MC-CDMA Part III discusses how to employ multiple antennas at the base station for the sake of supporting multiple users in the uplink Portrays the entire body of knowledge currently available on OFDM Provides the first complete treatment of OFDM, MIMO(Multiple Input Multiple Output)-OFDM and MC-CDMA Considers the benefits of channel coding and space time coding in the context of various application examples and features numerous complete system design examples Converts the lessons of Shannon’s information theory into design principles applicable to practical wireless systems Combines the benefits of a textbook with a research monograph where the depth of discussions progressively increase throughout the book This all-encompassing self-contained treatment will appeal to researchers, postgraduate students and academics, practising research and development engineers working for wireless communications and computer networking companies and senior undergraduate students and technical managers.

Download or read book MMSE Based Algorithm for Joint Signal Detection Channel and Noise Variance Estimation for OFDM Systems written by Vincent Savaux and published by John Wiley & Sons. This book was released on 2014-09-25 with total page 129 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents an algorithm for the detection of an orthogonal frequency division multiplexing (OFDM) signal in a cognitive radio context by means of a joint and iterative channel and noise estimation technique. Based on the minimum mean square criterion, it performs an accurate detection of a user in a frequency band, by achieving a quasi-optimal channel and noise variance estimation if the signal is present, and by estimating the noise level in the band if the signal is absent. Organized into three chapters, the first chapter provides the background against which the system model is presented, as well as some basics concerning the channel statistics and the transmission of an OFDM signal over a multipath channel. In Chapter 2, the proposed iterative algorithm for the noise variance and the channel estimation is detailed, and in Chapter 3, an application of the algorithm for the free-band detection is proposed. In both Chapters 2 and 3, the principle of the algorithm is presented in a simple way, and more elaborate developments are also provided. The different assumptions and assertions in the developments and the performance of the proposed method are validated through simulations, and compared to methods of the scientific literature.

Download or read book Multi Dimensional Channel Estimation for MIMO OFDM written by Christopher Knievel and published by . This book was released on 2014 with total page 217 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Pilot based Channel Estimation in OFDM System written by Fei Wang and published by . This book was released on 2011 with total page 81 pages. Available in PDF, EPUB and Kindle. Book excerpt: Orthogonal frequency division multiplexing (OFDM) is a multi-carrier transmission technology in wireless environment, and can also be seen as a multi-carrier digital modulation or multi-carrier digital multiplexing technology. A large number of orthogonal sub-carriers are used to transmit information. OFDM system has high utilization of frequency spectrum and satisfactory capability of reducing multi-path inference. So, OFDM has been considered as one of the core technologies of 4th generation (4G) wireless communication system in the future. Channel estimation plays a very important role in OFDM system. As a research hotpot, many related algorithms have been presented these years, which can be generally separated into two methods, pilot-based channel estimation and blind channel estimation. Pilot-based channel estimation estimates the channel information by obtaining the impulse response from all sub-carriers by pilot. Compared with blind channel estimation, which uses statistical information of the received signals, pilot-based channel estimation is a practical and an effective method. This thesis is on the pilot-based channel estimation of OFDM system. Firstly, it introduces the basic principle and realization of OFDM system, and describes the system construction and model with summary of some key technologies, such as fast Fourier transform (FFT) and cyclic prefix (CP). We also analyze OFDM modulation in the frequency domain, and discusses some advantages and disadvantages of OFDM system. Next, a summary of multi-path and time varying statistical properties of general wireless channel of OFDM system are presented. This thesis also investigates principles and performances of the channel estimation methods, block type pilot and comb type pilot. In the arrangement of block type pilot, the performance of channel estimation is analyzed with estimators based on three different algorithms, least square (LS) algorithm, linear minimum mean square error (LMMSE) algorithm and singular value decomposition (SVD) algorithm. To use comb-type pilot arrangement, the thesis introduces three methods of interpolation: linear interpolation, second order interpolation and cubic spline interpolation. Finally, simulation results using Matlab are used to compare bit error rate (BER) performance of different modulation schemes and types of pilot.

Download or read book OFDM Systems for Wireless Communications written by Adarsh Narasimhamurthy and published by Springer Nature. This book was released on 2022-06-01 with total page 68 pages. Available in PDF, EPUB and Kindle. Book excerpt: Orthogonal Frequency Division Multiplexing (OFDM) systems are widely used in the standards for digital audio/video broadcasting, WiFi and WiMax. Being a frequency-domain approach to communications, OFDM has important advantages in dealing with the frequency-selective nature of high data rate wireless communication channels. As the needs for operating with higher data rates become more pressing, OFDM systems have emerged as an effective physical-layer solution. This short monograph is intended as a tutorial which highlights the deleterious aspects of the wireless channel and presents why OFDM is a good choice as a modulation that can transmit at high data rates. The system-level approach we shall pursue will also point out the disadvantages of OFDM systems especially in the context of peak to average ratio, and carrier frequency synchronization. Finally, simulation of OFDM systems will be given due prominence. Simple MATLAB programs are provided for bit error rate simulation using a discrete-time OFDM representation. Software is also provided to simulate the effects of inter-block-interference, inter-carrier-interference and signal clipping on the error rate performance. Different components of the OFDM system are described, and detailed implementation notes are provided for the programs. The program can be downloaded here. Table of Contents: Introduction / Modeling Wireless Channels / Baseband OFDM System / Carrier Frequency Offset / Peak to Average Power Ratio / Simulation of the Performance of OFDM Systems / Conclusions

Download or read book Index Modulation for OFDM Communications Systems written by Miaowen Wen and published by Springer Nature. This book was released on 2021-01-04 with total page 182 pages. Available in PDF, EPUB and Kindle. Book excerpt: Thanks to their considerable advantages, index modulation and orthogonal frequency division multiplexing (OFDM) are considered to be promising candidates for future wireless communications. This book focuses on the index modulation techniques for OFDM communications systems, which allow information to be conveyed not only via constellation symbols, but also by the indices of various transmission entities in OFDM systems, such as signal constellations, spreading codes, and pilots. The book discusses representative transmitter and receiver designs, optimization and performance analysis of index modulation based on various transmission entities. It first introduces readers to constellation-based index modulation via a combinatorial approach, including the classical index modulation scheme and two embodiments of information-guided precoding for OFDM systems. It further discusses constellation-based index modulation via a permutational approach, including the basic, generalized, and diversity-enhancing forms. It then describes how the spreading code is used to design an index modulated spread spectrum for OFDM systems, and the extensions to multi-code and multi-user scenarios. In addition it explores information guided pilot insertion for OFDM systems, followed by applications to carrier phase tracking and channel estimation. Lastly, the book highlights a number of open problems and discusses future research directions in the general field of index modulation. Intended for professionals and researchers in the field of wireless communications, this book is also a valuable resource for advanced-level electrical engineering and computer science students.

Download or read book Channel Estimation Techniques for OFDM Systems in Dispersive Time varying Channels written by and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Coherent modulation is more effective than differential modulation for orthogonal frequency division multiplexing (OFDM) systems requiring high data rate and spectral efficiency. Channel estimation is therefore an integral part of the receiver design. In this thesis, two iterative maximum likelihood based channel estimation algorithms are proposed for an OFDM system in dispersive time-varying channels. A multipath channel model is proposed for OFDM uplink transmission in macrocellular systems. The multipath fading channel is modeled such that the channel state can be determined by estimating the unknown channel parameters. A second-order Taylor series expansion is adopted to simplify the channel estimation problem. Based on the system model, an iterative maximum likelihood based algorithm is first proposed to estimate the discrete-time channel parameters. The mean square error performance of the proposed algorithm is analyzed using a small perturbation technique. Based on a convergence rate analysis, an improved iterative maximum likelihood based channel estimation algorithm is presented using a successive overrelaxation method. Numerical experiments are performed to confirm the theoretical analyses and show the improvement in convergence rate of the improved algorithm.

Download or read book Implementation of Channel Estimation Algorithms in OFDM written by Navdeep Bansal and published by LAP Lambert Academic Publishing. This book was released on 2014-11-01 with total page 80 pages. Available in PDF, EPUB and Kindle. Book excerpt: Orthogonal Frequency Division Multiplexing (OFDM) is a very potential technique for transmitting high bit rate data over indoor and outdoor wireless communication channels with high bandwidth efficiency and robustness to multipath delay. OFDM is a multichannel modulation that divides a given channel into many parallel sub-channels or subcarriers, so that multiple symbols are sent in parallel. The first multichannel modulation systems appeared in the 1950's as military radio links, best characterized as frequency-division multiplexed systems. The first OFDM schemes were presented by Chang and Saltsburg, in which actual use/ practicability of OFDM was limited. However, later on the OFDM was made more practical through work describe in the article uses Discrete Fourier transform (DFT) with a cyclic prefix. The DFT implemented with a Fast Fourier Transform (FFT)) and the cyclic prefix have made OFDM both practical and attractive to the radio link designer. A similar multichannel modulation scheme, Discrete Multi-Tone (DMT) modulation, has been developed for static channels such as the digital subscriber loop.

Download or read book Channel Estimation written by Shazib Naveed and published by LAP Lambert Academic Publishing. This book was released on 2013 with total page 68 pages. Available in PDF, EPUB and Kindle. Book excerpt: With rapid growth of digital communication in recent years, the need for high speed data transmission is increased. Moreover, future wireless systems are expected to support a wide range of services which includes video, data and voice. OFDM is a promising candidate for achieving high data rates in mobile environment, due to its resistance to ISI, which is a common problem found in high speed data communication. In OFDM, modulation may be differential or coherent. When using differential modulation there is no need for a channel estimate but its performance is inferior to the coherent system. Coherent modulation requires the channel estimation which gives better performance but with relatively more complex receiver structure. Training Symbol Assisted Modulation is used to achieve reliable channel estimates by transmitting Training along with data symbols. In this thesis, Shazib Naveed has analyzed different channel estimation patterns in terms of BER and propose a new scheme for transmitting Training symbols in wireless OFDM systems. Author has also proposed an adaptive scheme of channel estimation in wireless OFDM systems, which track the multi-path fading channel.

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:

Download or read book Channel Estimation Performance for Zero Overhead Channel Access in Mobile Sensor Networks written by and published by . This book was released on 2004 with total page 9 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this work we study the effects of channel estimation/ equalization on the BER performance of RF carrier frequency hopped OFDM (FH-OFDM) when using synchronization information that is embedded directly into the OFDM baseband symbol stream. In sensor networks using CSMA, the acquisition preambles can require a large overhead percentage of the overall message. Embedding synchronization information into the data information stream eliminates this channel access overhead, thus providing potential for zero-time overhead channel access. Superposition (embedding) of the sync information, however, causes interference onto the data information, which must be removed for satisfactory BER performance. Consequently, embedded synchronization interference cancellation (EIC) is utilized, which requires accurate channel state estimation. Using coherent 4QAM- and 16QAM-OFDM modulation, channel estimation and BER performance is evaluated using the COST207 multipath fading channel model. Less than a 1 dB performance difference is found between a preamble and embedded system for short message bursts (

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 Channel Estimation Techniques for Single and Multiple Transmit Antenna Orthogonal Frequency Division Multiplexing OFDM Systems written by and published by . This book was released on 2005 with total page 73 pages. Available in PDF, EPUB and Kindle. Book excerpt: Orthogonal frequency division multiplexing (OFDM) is an efficient multi-carrier modulation technique which can be combined with transmitter and receiver diversity communication systems. Maximal ratio combining (MRC) and space-time block coding (STBC) can be used in conjunction with receiver and transmitter diversity in order to increase the communication system's performance. For these systems, channel estimation and tracking must be performed since the receiver requires channel state information for decoding. In this thesis, block-type and comb-type channel estimation algorithms for OFDM systems over multipath fading channels are studied and simulated. Performance results using simulated frequency-selective channels are presented.

Download or read book OFDM and MC CDMA written by Lajos Hanzo and published by John Wiley & Sons. This book was released on 2007-01-11 with total page 430 pages. Available in PDF, EPUB and Kindle. Book excerpt: Wireless communications has witnessed a tremendous growth during the past decade and further spectacular enabling technology advances are expected in an effort to render ubiquitous wireless connectivity a reality. Currently, a technical in-depth book on this subject is unavailable, which has a similar detailed exposure of OFDM, MIMO-OFDM and MC-CDMA. A further attraction of the joint treatment of these topics is that it allows the reader to view their design trade-offs in a comparative context. Divided into three main parts: Part I provides a detailed exposure of OFDM designed for employment in various applications Part II is another design alternative applicable in the context of OFDM systems where the channel quality fluctuations observed are averaged out with the aid of frequency-domain spreading codes, which leads to the concept of MC-CDMA Part III discusses how to employ multiple antennas at the base station for the sake of supporting multiple users in the uplink By providing an all-encompassing self-contained treatment this volume will appeal to a wide readership, as it is both an easy-reading textbook and a high-level research monograph.

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:

Download or read book Advanced Hybrid Information Processing written by Lin Yun and published by Springer Nature. This book was released on with total page 487 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Orthogonal Frequency Division Multiplexing OFDM Channel Estimation Using Pilot Based Parametric Scheme written by Sowmya Rajanna and published by . This book was released on 2016 with total page 26 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: This paper is aimed at parametric Multiple Input Multiple Output (MIMO) - Orthogonal Frequency Division Multiplexing (OFDM) channel estimation that increases the spectrum efficiency of the wireless communication systems. OFDM technology has been widely used due to its high data rate and low multipath distortion. The estimation of channel for OFDM is required in vehicular environments and many other cutting-edge technology applications. To develop such reliable vehicular wireless communication systems, it is necessary to set up the standards and models of propagation channel with respect to the environment and scenarios. The proposed parametric scheme can accomplish super resolution by assessing the delays in arbitrary paths, making this scheme more suitable for wireless channels. The channel estimation precision is increased by using the spatial and temporal correlations in the wireless MIMO channel. The average pilot overhead for each antenna is reduced because of the temporal correlation of MIMO channels. Thus, the parametric scheme is promising for future wireless technologies as it accomplishes better spectral efficiency and better robustness for the multipath fading channels.