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 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 Conference Proceedings written by and published by . This book was released on 2004 with total page 754 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Computing Science Communication and Security written by Nirbhay Chaubey and published by Springer Nature. This book was released on 2023-08-07 with total page 294 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book constitutes the refereed proceedings of the 4th International Conference on Computing Science, Communication and Security, COMS2 2023, held in Gandhinagar, India, during February 6–7, 2023. The 20 full papers included in this book were carefully reviewed and selected from 190 submissions. They were organized in topical sections on artificial intelligence and machine learning; networking and communications.

Download or read book Orthogonal Frequency Division Multiplexing with Diversity for Future Wireless Systems written by Khoa N. Le and published by Bentham Science Publishers. This book was released on 2012 with total page 621 pages. Available in PDF, EPUB and Kindle. Book excerpt: "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"

Download or read book Conference Record written by and published by . This book was released on 2005 with total page 716 pages. Available in PDF, EPUB and Kindle. Book excerpt:

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 Differential STBC for OFDM Based Wireless Systems written by Benigno Rodríguez Díaz and published by Cuvillier Verlag. This book was released on 2007 with total page 181 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Multi Carrier and Spread Spectrum Systems written by Khaled Fazel and published by John Wiley & Sons. This book was released on 2008-09-15 with total page 384 pages. Available in PDF, EPUB and Kindle. Book excerpt: The technological progress in multi-carrier (MC) modulation led orthogonal frequency division multiplexing (OFDM) to become an important part of beyond 3G cellular mobile communication standards, including LTE and WiMAX. In addition, the flexibility offered by the spread spectrum (SS) and time division multiplexing (TDM) techniques motivated many researchers to investigate several MC combined multiple access schemes, such as MC-CDMA, OFDMA and MC-TDMA. These schemes benefit from the advantages of each sub-system and offer high flexibility, high spectral efficiency, simple detection strategies and narrow-band interference rejection capability. Multi-Carrier and Spread Spectrum Systems is one of the first books to describe and analyze the basic concepts of multi-carrier OFDM transmission and its combination with spread spectrum (MC-CDMA). The different architectures and detection strategies as well as baseband-related transceiver components are explained. This includes topics like FEC channel coding and decoding, modulation and demodulation (IFFT/FFT), digital I/Q-generation, time and frequency synchronisation, channel estimation, frequency domain equalization and RF aspects such as phase noise and non-linearity issues. Concrete examples of its applications for cellular mobile communication systems (B3G/4G) are given. Further derivatives of MC-SS (such as OFDMA, SS-MC-MA and DFT-spread OFDM) and their corresponding applications in the LTE, WiMAX, WLAN and DVB-RCT standards are detailed. Capacity and flexibility enhancements of multi-carrier OFDM systems by different MIMO diversity techniques such as space time/frequency coding (STC, SFC) and software defined radio concepts are also described. Written in a highly accessible manner this book provides a unique reference on the topics of multi-carrier and spread spectrum communications, assisting 4G engineers with their implementation. Fully updated new edition of successful text, including two new chapters on LTE and WiMAX Describes in detail new applications of OFDM in mobile communication standards Examines all multi-carrier spread spectrum schemes, with in-depth analysis, from theory to practice Introduces the essentials of important wireless standards based on multi-carrier/spread spectrum techniques.

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 On the Achievable Rate of Stationary Fading Channels written by Meik Dörpinghaus and published by Springer Science & Business Media. This book was released on 2011-08-14 with total page 317 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volumes discusses various aspects regarding the capacity/achievable data rate of stationary Rayleigh fading channels. First, it analyses bounds on the achievable data rate with zero-mean proper Gaussian input symbols, which are capacity achieving in the coherent case, i.e., in case of perfect channel knowledge at the receiver. These bounds are tight in the sense that the difference between the upper and the lower bound is bounded for all SNRs. The lower bound converges to the coherent capacity for asymptotically small channel dynamics. Furthermore, these bounds are extended to the case of multiple-input multiple-output (MIMO) channels and to the case of frequency selective channels. In a further part, the present work studies the achievable rate with receivers based on synchronized detection and a code-aided channel estimation. For a specific type of such a receiver an approximate upper bound on the achievable rate is derived. The comparison of this approximate upper bound and the achievable data rate with receivers using synchronized detection based on a solely pilot based channel estimation gives an approximate upper bound on the possible gain by using this kind of code-aided channel estimation in comparison to the conventional receiver using a solely pilot based channel estimation. In addition, the achievable data rate with an optimal joint processing of pilot and data symbols is studied and a lower bound on the achievable rate for this case is derived. In this context, it is also shown which part of the mutual information of the transmitter and the receiver is discarded when using the conventional receiver with synchronized detection based on a solely pilot based channel estimation.

Download or read book Block Transceivers written by Paulo Diniz and published by Morgan & Claypool Publishers. This book was released on 2012-06-01 with total page 208 pages. Available in PDF, EPUB and Kindle. Book excerpt: The demand for data traffic over mobile communication networks has substantially increased during the last decade. As a result, these mobile broadband devices spend the available spectrum fiercely, requiring the search for new technologies. In transmissions where the channel presents a frequency-selective behavior, multicarrier modulation (MCM) schemes have proven to be more efficient, in terms of spectral usage, than conventional modulations and spread spectrum techniques. The orthogonal frequency-division multiplexing (OFDM) is the most popular MCM method, since it not only increases spectral efficiency but also yields simple transceivers. All OFDM-based systems, including the single-carrier with frequency-division equalization (SC-FD), transmit redundancy in order to cope with the problem of interference among symbols. This book presents OFDM-inspired systems that are able to, at most, halve the amount of redundancy used by OFDM systems while keeping the computational complexity comparable. Such systems, herein called memoryless linear time-invariant (LTI) transceivers with reduced redundancy, require low-complexity arithmetical operations and fast algorithms. In addition, whenever the block transmitter and receiver have memory and/or are linear time-varying (LTV), it is possible to reduce the redundancy in the transmission even further, as also discussed in this book. For the transceivers with memory it is possible to eliminate the redundancy at the cost of making the channel equalization more difficult. Moreover, when time-varying block transceivers are also employed, then the amount of redundancy can be as low as a single symbol per block, regardless of the size of the channel memory. With the techniques presented in the book it is possible to address what lies beyond the use of OFDM-related solutions in broadband transmissions. Table of Contents: The Big Picture / Transmultiplexers / OFDM / Memoryless LTI Transceivers with Reduced Redundancy / FIR LTV Transceivers with Reduced Redundancy

Download or read book Space time Diversity for CDMA Systems Over Frequency selective Fading Channels written by Ayman M. Assra and published by . This book was released on 2010 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Supporting the expected high data rates required by wireless Internet and high-speed multimedia services is one of the basic requirements in broadband mobile wireless systems. However, the achievable capacity and data rate of wireless communication systems are limited by the time-varying nature of the channel. Efficient techniques for combating the time-varying effects of wireless channels can be achieved by utilizing different forms of diversity. In recent years, transmit diversity based on space-time coding (STC) has received more attention as an effective technique for combating fading. On the other hand, most existing space-time diversity techniques have been developed for flat-fading channels. Given the fact that wireless channels are generally frequency-selective, in this thesis, we aim to investigate the performance of space-time diversity schemes for wideband code-division multiple-access (WCDMA) systems over frequency-selective fading channels. The proposed receiver in this case is a rake-type receiver, which exploits the path diversity inherent to multipath propagation. Then, a decorrelator detector is used to mitigate the multiple access interference (MAI) and the known near-far problem. We derive the bit error rate (BER) expression over frequency-selective fading channels considering both the fast and slow fading cases. Finally, we show that our proposed receiver achieves the full system diversity through simulation and analytical results. Most of the work conducted in this area considers perfect knowledge of the channel at the receiver. Hence, channel identification brings significant challenges to multiple-input multiple-output (MIMO) CDMA systems. In light of this, we propose a channel estimation and data detection scheme based on the superimposed training-based approach. The proposed scheme enhances the performance by eliminating the MAI from both the channel and data estimates by employing two decorrelators; channel and data decorrelators. The performance of the proposed estimation technique is investigated over frequency-selective slow fading channels where we derived a closed-form expression for the BER as a function of the number of users, K, the number resolvable paths, L, and the number of receive antennas, V . Finally, our proposed scheme is shown to be more robust to channel estimation errors. Furthermore, both the analytical and simulation results indicate that the full system diversity is achieved. Considering that training estimation techniques suffer either from low spectral efficiency (i.e., conventional training approach) or from high pilot power consumption (i.e., superimposed training-based approach), in the last part of the thesis, we present an iterative joint detection and estimation (JDE) using the expectation-maximization (EM) algorithm for MIMO CDMA systems over frequency-selective fading channels. We also derive a closed-form expression for the optimized weight coefficients of the EM algorithm, which was shown to provide significant performance enhancement relative to the conventional equal-weight EM-based signal decomposition. Finally, our simulation results illustrate that the proposed receiver achieves near-optimum performance with modest complexity using very few training symbols.

Download or read book Performance Analysis of Decorrelating Detectors for Dual rate Synchronous DS CDMA Systems Over Frequency selective Rayleigh Fading Channels written by Xiangtao Li and published by . This book was released on 2002 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In this thesis, the performance of a decorrelating-based multiuser detector for frequency-selective channels is discussed. The users transmit data at two different rates are instead of one single rate. According to their transmission rates, the users are classified into two groups, a group of high rate users and a group of low rate users. It is assumed that over the time interval [0, T o], the low rate users transmit one bit, while the high rate users transmit M bits of information. At the receiving end, two types of decorrelators are examined to decode the signals: a low rate decorrelator (LRD) and a high rate decorrelator (HRD). The LRD makes a decoding decision for every T o seconds and views one high rate user as M effective low rate users. The HRD makes a decision for every T 1 = T o / M seconds and detects a bit from a low rate user M times during the time interval[0, T o]. The signals from the two groups are transmitted over frequency-selective multipath Rayleigh fading channels. The maximal ratio combining (MRC) technique is used in two parts of the receivers. First, the multipath diversity and MRC diversity reception method are utilized in the receivers to combat against the multipath fading. Secondly, in HRD, MRC is employed to implement a soft decoding rule for the low rate users. The error probability and asymptotic multiuser efficiency for both types of decorrelators will be evaluated and the simulation results given. It can be seen in the simulation results that the LRD is superior to the HRD in the performance for both low rate and high rate users.

Download or read book Relay Diversity Techniques of Orthogonal Frequency division Multiplexing and Multi carrier Code Division Multiple Access written by Nur I. Abdul Razak and published by . This book was released on 2012 with total page 280 pages. Available in PDF, EPUB and Kindle. Book excerpt: The future of mobile and personal communications requires a system that can support a large number of users and has the ability to provide high-speed services. Meeting this demand is challenging since wireless communications are subject to these four major constraints: complex fading channels, a scarce usable radio spectrum, and limitations on the power and size of the mobile terminals. Space-time codes, such as the Alamouti/space-time block coding (STBC) and cyclic delay diversity (CDD) can provide diversity and coding gains in multiple-input multiple-output (MIMO) systems over fading channels. However in an ad-hoc network, nodes are often constrained in hard-ware complexity and size, which makes MIMO systems impractical for certain applications. Cooperative relay diversity schemes have been introduced in an effort to overcome these limitations. Cooperative techniques allow a collection of communication nodes to cooperate with to relay signals amongst each other, effectively creating a virtual antenna array, which combat multipath fading in wireless channels. This thesis investigates relay diversity techniques in cooperative com-munications, namely the distributed space-time block coding (DSTBC) and relay cyclic delay diversity (RCDD) for OFDM and MC-CDMA systems. The performance analysis of the wireless relay networks un¬der different protocols and fading channels are investigated. We de¬rived the formulas for the symbol error rate (SER) of the investigated schemes in fading channels. Finally, a novel hybrid relay diversity (HRD) is presented for OFDM-based system. This new relay structure addresses the issue of achiev¬ing a full spatial and multipath diversity by developing a hybrid for CDD and STBC. Simulation on the system performance of HRD shows the superiority of the technique compared to standalone DSTBC and RCDD.

Download or read book Block Turbo Code and Its Application to OFDM for Wireless Local Area Network written by and published by . This book was released on with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: To overcome multipath fading and Inter symbol Interference (ISI), in convolutional single carrier systems equalizers are used. But it increases the system complexity. Another approach is to use a multicarrier modulation technique such as OFDM, where the data stream to be transmitted is divided into several lower rate data streams each being modulated on a subcarrier. To avoid ISI, a small interval, known as the guard time interval, is inserted into OFDM symbols. The length of the guard time interval is chosen to exceed the channel delay spread. Therefore, OFDM can combat the multipath fading and eliminate ISI almost completely. The another problem is the reduction of the error rate in transmitting digital data. For that we use error correcting Codes in the design of digital transmission systems. Turbo Codes have been widely considered to be the most powerful error control code of practical importance. Turbo codes can be achieved by serial or parallel concatenation of two (or more) codes called the constituent codes. The constituent codes can be either block codes or convolutional codes. Currently, most of the work on turbo codes have essentially focused on Convolutional Turbo Code (CTC)s and Block Turbo Code (BTC)s have been partially neglected. Yet, the BTC solution is more attractive for a wide range of applications. In this paper, Block Turbo Codes or Turbo Product Codes are used which is similar to the IEEE 802.11a WLAN standard. In this thesis work simple explanation of BTCOFDM theory is given. The BER performance is evaluated for the Block Turbo coded BPSK and QPSK OFDM system, under both AWGN channel and Rayleigh fading channel. It also compares the BER performance of Block Turbo coded OFDM with the uncoded OFDM. It is verified in the present work that the BTCOFDM system with 4 iterations is sufficient to provide a good BER performance. Additional number of iterations does not show noticeable difference. The simulation results shows that the BTCOFDM system ac.

Download or read book Orthogonal Frequency Division Multiplexing for Wireless Communications written by Ye Geoffrey Li and published by Springer Science & Business Media. This book was released on 2006-05-31 with total page 314 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.