Download or read book Performance Analysis of OFDM in Frequency Selective Slowly Fading Nakagami Channels written by Patrick A. Count and published by . This book was released on 2001-12-01 with total page 130 pages. Available in PDF, EPUB and Kindle. Book excerpt: In an effort to offer faster, more reliable wireless communications services to the public, many wireless standardization committees have, in recent years, adopted Orthogonal Frequency Division Multiplexing (OFDM) as the modulation technique of choice. Given the incredible growth in the industry as manifest by the seemingly infinite demand for wireless products and services and the accompanying need for superior performance of these systems in congested and electronically demanding environments, it is evident that OFDM will be at the core of many future high data rate communications systems. This thesis examines the performance of OFDM in frequency-selective slowly fading Nakagami channels. The Nakagami channel is used in this study as it probably best models the propagation characteristics of the environments in which OFDM based systems will be applied.

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 Performance Analysis of OFDM CDMA Systems in Rayleigh Fading Channels written by Jagadish Chandra Kalaga and published by . This book was released on 2003 with total page 136 pages. Available in PDF, EPUB and Kindle. Book excerpt:

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.

Download or read book Analysis of Coded OFDM System Over Frequency Selective Fading Channels written by Jun Zheng and published by . This book was released on 2003 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis considers the analysis of system performance and resource allocation for a coded OFDM system over frequency selective fading channels. Due to the inseparable role taken by channel coding in a coded OFDM system, an information theoretical analysis is carried out and taken as the basis for the system performance and throughput. Based on the results of the information theoretical analysis, the optimal system BER performance of a coded OFDM system is first shown to converge to the outage probability for large OFDM block lengths. Instead of evaluating the outage probability numerically, we provide in this thesis a simple analytical closed form approximation of the outage probability for a coded OFDM system over frequency selective quasi-static fading channels. Simulation results of the turbo-coded OFDM systems further confirm the approximation of the outage probability. By taking the instantaneous channel capacity as the analytical building block, system throughput of a coded OFDM system is then provided. With the aim to compare the performance difference between adaptive and uniform resource allocation strategies, the system throughput of different allocation schemes under various channel conditions is analyzed. First, it is demonstrated that adaptive power allocation over OFDM sub-carriers at the transmitter achieves very little gain in terms of throughput over a uniform power distribution scheme. Theoretical analysis is then provided of the throughput increase of adaptive-rate schemes compared with fixed-rate schemes under various situations. Two practical OFDM systems implementing rate-compatible-punctured-turbo-code-based (RCPT-based) hybrid automatic-repeat-request (Hybrid-ARQ) and redundancy incremental Hybrid-ARQ protocols are also provided to verify the analytical results.

Download or read book Performance Analysis of the IEEE 802 11A WLAN Standard Optimum and Sub Optimum Receiver in Frequency Selective Slowly Fading Nakagami Channels with AWGN and Pulsed Noise Jamming written by Christos Kalogrias and published by . This book was released on 2004-03-01 with total page 169 pages. Available in PDF, EPUB and Kindle. Book excerpt: The objective of this thesis is to investigate the performance of the orthogonal frequency division multiplexing (OFDM) based IEEE 802.11a wireless local area network (WLAN) standard receiver when the signal is transmitted over a frequency selective, slow fading Nakagami channel in a worst case, pulse-noise jamming environment. The different combinations of modulation type (both binary and non-binary modulation) and convolutional code rate specified by the WLAN standard are examined. Receiver performance with Viterbi soft decision decoding (SDD) is analyzed for additive white Gaussian noise (AWGN) alone as well as for AWGN plus pulse-noise jamming (PNJ). The performance of the IEEE 802.11a WLAN standard receiver is examined both for the scenario in which perfect side information is assumed (optimum receiver) and when it is not (sub-optimum receiver). For the sub-optimum receiver scenario, the receiver performance is examined both when noise-normalization is utilized and when only linear combining is utilized. The analysis indicates that the receiver performance is severely affected by the pulse-noise jamming environment for the linear combining scenario; however, the sub-optimum receiver performance is significantly improved when noise-normalization is implemented. (2 tables, 74 figures, 11 refs.)

Download or read book Performance Analysis of Coded OFDM on Fading Channels with Non ideal Interleaving and Channel Knowledge written by and published by . This book was released on 1996 with total page 27 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book OFDM Based Cooperative Communication Over Nakagami Fading Channel written by Saifur Rahman Sabuj and published by . This book was released on 2013-08-30 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:

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 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 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.

Download or read book Wireless Communication Systems written by Ke-Lin Du and published by Cambridge University Press. This book was released on 2010-04-15 with total page 1020 pages. Available in PDF, EPUB and Kindle. Book excerpt: This practically-oriented, all-inclusive guide covers all the major enabling techniques for current and next-generation cellular communications and wireless networking systems. Technologies covered include CDMA, OFDM, UWB, turbo and LDPC coding, smart antennas, wireless ad hoc and sensor networks, MIMO, and cognitive radios, providing readers with everything they need to master wireless systems design in a single volume. Uniquely, a detailed introduction to the properties, design, and selection of RF subsystems and antennas is provided, giving readers a clear overview of the whole wireless system. It is also the first textbook to include a complete introduction to speech coders and video coders used in wireless systems. Richly illustrated with over 400 figures, and with a unique emphasis on practical and state-of-the-art techniques in system design, rather than on the mathematical foundations, this book is ideal for graduate students and researchers in wireless communications, as well as for wireless and telecom engineers.

Download or read book Recent Trends in Intelligent and Emerging Systems written by Kandarpa Kumar Sarma and published by Springer. This book was released on 2015-06-09 with total page 223 pages. Available in PDF, EPUB and Kindle. Book excerpt: It is a compilation of research works related to intelligent and emerging system design using a range of tools including soft-computation. The book includes reviews, actual designs, research works, discussion and experimental results related to works in the areas of communication, computation, vision sciences, bio-inspired system design, social dynamic, related process design, etc. The audience of this book is expected to be researchers who deal with intelligent and emerging system design through mathematical and computational modeling and experimental designs. Specifically, audiences that are broadly involved in the domains of electronics and communication, electrical engineering, mathematics, computer science, other applied informatics domains and related areas will find the book interesting. The works included in the book broadly covers all areas of Electronics and Communication Engineering and Technology, Soft-computational Applications, Human Computer Interactive Designs and Social and Economic Dynamics. The works included in the volume have been grouped into Communication, Biomedical and Social Science, HCI and Bio-inspired System Design, Speech Processing and Review totaling sixteen contributions.

Download or read book Coded Non Ideal OFDM Systems Analysis and Receiver Designs written by Fei Peng and published by . This book was released on 2007 with total page 374 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation presents four technical contributions in the theory and practice of low-density parity-check (LDPC) codes and orthogonal frequency division multiplexing (OFDM) systems withtransmission non-linearity and with interference due to high mobility. We first explore the universality of LDPC codes for the binary erasure channel (BEC), the AWGN channel, and the flat Rayleigh fading channel. Using excess mutual information as a performance measure, we demonstrate that an LDPC code designed on a singlechannel can be universally good across the three channels. Thus, a channel for which LDPC code design is simple may be used as a surrogate for channels that are more challenging. Due to fast channel variations, OFDM systems suffer from inter-carrier interference (ICI) in frequency-selective fast fading channels. We propose a novel iterative receiver design that achieves near-optimal performance while maintaining a complexity that grows only linearly with the number of OFDM carriers. Weprove that the matched filter bound for such a channel is also the maximum-likelihood sequence detection (MLSD) bound. Because of the presence of high peaks at OFDM modulator output, amplitude clipping due to amplifier saturation causes performance degradation. We show that existing analyses underestimate the capacity of OFDM systems with clipping, and we analyze thecapacity of clipped OFDM systems with AWGN and frequency-selective Rayleigh fading. We prove that for frequency-selective Rayleigh fading channels, under certain conditions, there exists an SNR threshold, above which the capacity of a clipped system is higherthan that of an unclipped system. We provide upper and lower boundson the channel capacity and closed-form approximations of discrete-input capacities with and without clipping. We also derive tight MLSD lower bounds and propose near-optimal receivers for OFDM systems with clipping. We show that over frequency-selective Rayleigh fading channels, under certain conditions, a clipped system with MLSD can achieve better performance than an unclipped system. We show that the MLSD boundscan be achieved or closely approached by the proposed low complexity receivers in various channel types.

Download or read book A Digital Phase Locked Loop based Signal and Symbol Recovery System for Wireless Channel written by Basab Bijoy Purkayastha and published by Springer. This book was released on 2015-01-29 with total page 254 pages. Available in PDF, EPUB and Kindle. Book excerpt: The book reports two approaches of implementation of the essential components of a Digital Phase Locked Loop based system for dealing with wireless channels showing Nakagami-m fading. It is mostly observed in mobile communication. In the first approach, the structure of a Digital phase locked loop (DPLL) based on Zero Crossing (ZC) algorithm is proposed. In a modified form, the structure of a DPLL based systems for dealing with Nakagami-m fading based on Least Square Polynomial Fitting Filter is proposed, which operates at moderate sampling frequencies. A sixth order Least Square Polynomial Fitting (LSPF) block and Roots Approximator (RA) for better phase-frequency detection has been implemented as a replacement of Phase Frequency Detector (PFD) and Loop Filter (LF) of a traditional DPLL, which has helped to attain optimum performance of DPLL. The results of simulation of the proposed DPLL with Nakagami-m fading and QPSK modulation is discussed in detail which shows that the proposed method provides better performance than existing systems of similar type.

Download or read book Wireless Networks and Computational Intelligence written by K. R. Venugopal and published by Springer. This book was released on 2012-07-11 with total page 671 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book constitutes the refereed proceedings of the 6th International Conference on Information Processing, ICIP 2012, held in Bangalore, India, in August 2012. The 75 revised full papers presented were carefully reviewed and selected from 380 submissions. The papers are organized in topical sections on wireless networks; image processing; pattern recognition and classification; computer architecture and distributed computing; software engineering, information technology and optimization techniques; data mining techniques; computer networks and network security.

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.