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Author: Mohamed Aljerjawi
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
The application of space-time coding in wireless communication systems has shown to improve the quality of the received signal at the mobile user by placing the spatial diversity at the base station. In this thesis, we propose a simple space-time spreading scheme for code-division multiple-access (CDMA) systems over fast-fading channels. The proposed transmit diversity scheme is based on two transmit and M receive antennas and is suitable for Rayleigh fast-fading channels. In this we employ orthogonal spreading codes to exploit the time diversity introduced by the channel, and hence a two-fold of the diversity order obtained using existing spacetime spreading schemes is achieved. Nevertheless, for slowly-fading channels, we show that the proposed coding scheme reduces to existing schemes introduced in the literature with no performance degradation. Then, we examine the effect of using nonorthogonal spreading codes on the receiver performance. Our results show that using a simple adaptive decoder, based on the minimum mean-squared error (MMSE) criterion, the diversity order is still maintained and only a small loss in the signal-to noise ratio (SNR) is incurred relative to the ideal case with orthogonal codes.
Author: Mohamed Aljerjawi
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
The application of space-time coding in wireless communication systems has shown to improve the quality of the received signal at the mobile user by placing the spatial diversity at the base station. In this thesis, we propose a simple space-time spreading scheme for code-division multiple-access (CDMA) systems over fast-fading channels. The proposed transmit diversity scheme is based on two transmit and M receive antennas and is suitable for Rayleigh fast-fading channels. In this we employ orthogonal spreading codes to exploit the time diversity introduced by the channel, and hence a two-fold of the diversity order obtained using existing spacetime spreading schemes is achieved. Nevertheless, for slowly-fading channels, we show that the proposed coding scheme reduces to existing schemes introduced in the literature with no performance degradation. Then, we examine the effect of using nonorthogonal spreading codes on the receiver performance. Our results show that using a simple adaptive decoder, based on the minimum mean-squared error (MMSE) criterion, the diversity order is still maintained and only a small loss in the signal-to noise ratio (SNR) is incurred relative to the ideal case with orthogonal codes.
Author: Ariel Sacramento
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
With applications such as video conferencing, extensive web browsing and live video streaming, future wireless systems become extremely demanding in terms of high data rates and improved signal quality. In this thesis the performance of a space-time spreading transmit diversity scheme is examined over a frequency-flat Nakagami- m fading channel. The Nakagami- m channel model is considered as it is well known for modeling signal fading conditions ranging from severe to moderate, to light fading or no fading, through its parameter m. We also propose in this thesis a coded transmit diversity scheme which is based on a combination of a convolutional code with a space-time transmit diversity scheme that uses direct-sequence code division multiple access (DS-CDMA) for multiuser access. Our focus will be on the uplink of the communication system. The space-time scheme employs N = 2 and N r antennas at the mobile station (MS) side and at the base station (BS) side respectively. DS-CDMA is used to support many users and a linear decorrelator detector is used to combat the effect of multiuser interference. We study the performance of both the uncoded and coded transmit diversity schemes over slow fading and fast fading channels. In all cases, the investigations start by determining the probability density function (PDF) of the signal to interference and noise ratio at the output of the space-time combiner at the BS receiver side. Using this PDF we derive a closed-form (or an approximation) expression for the bit error rate (BER) of the system under consideration. The accuracy of the PDF and BER expressions are verified when compared to simulation results for different values of the fading figure m and for different combinations of transmit and receive antennas. In the case of the coded space-time transmit diversity scheme, the pairwise error probability and the corresponding BER upper bounds are obtained for fast and slow fading channels. The derived error bounds, when compared to system simulations, are shown to be tight at high signal-to-noise ratios. Furthermore, our analytical results explicitly show the achieved system diversity in terms of the number of transmit and receive antennas and the fading figure m. When the coded space-time scheme is considered, its diversity is shown to be a function of the minimum free distance d free of the convolutional code used. Furthermore we show that the diversity of the different schemes considered is always independent of the system load.
Author: Ayman M. Assra
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
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.
Author: Norihito Aoki
Publisher:
ISBN:
Category :
Languages : en
Pages : 146
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Book Description
Author: Marvin K. Simon
Publisher: John Wiley & Sons
ISBN: 0471715239
Category : Science
Languages : en
Pages : 1872
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Book Description
The four short years since Digital Communication over Fading Channels became an instant classic have seen a virtual explosion of significant new work on the subject, both by the authors and by numerous researchers around the world. Foremost among these is a great deal of progress in the area of transmit diversity and space-time coding and the associated multiple input-multiple output (MIMO) channel. This new edition gathers these and other results, previously scattered throughout numerous publications, into a single convenient and informative volume. Like its predecessor, this Second Edition discusses in detail coherent and noncoherent communication systems as well as a large variety of fading channel models typical of communication links found in the real world. Coverage includes single- and multichannel reception and, in the case of the latter, a large variety of diversity types. The moment generating function (MGF)-based approach for performance analysis, introduced by the authors in the first edition and referred to in literally hundreds of publications, still represents the backbone of the book's presentation. Important features of this new edition include: * An all-new, comprehensive chapter on transmit diversity, space-time coding, and the MIMO channel, focusing on performance evaluation * Coverage of new and improved diversity schemes * Performance analyses of previously known schemes in new and different fading scenarios * A new chapter on the outage probability of cellular mobile radio systems * A new chapter on the capacity of fading channels * And much more Digital Communication over Fading Channels, Second Edition is an indispensable resource for graduate students, researchers investigating these systems, and practicing engineers responsible for evaluating their performance.
Author: Hsiao-Hwa Chen
Publisher: John Wiley & Sons
ISBN: 9780470022955
Category : Technology & Engineering
Languages : en
Pages : 476
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Book Description
Future wireless communication systems should be operating mainly, if not completely, on burst data services carrying multimedia traffic.The need to support high-speed burst traffic has already posed a great challenge to all currently available air-link technologies based either on TDMA or CDMA.The first generation CDMA technology has been used in both 2G and 3G mobile cellular standards and it has been suggested that it is not suitable for high-speed burst-type traffic. There are many problems with the first generation CDMA technology, such as its low spreading efficiency, interference-limited capacity and the need for precision power control, etc... 'The Next Generation Technologies' will offer first-hand information on how to make use of various innovative technologies to implement the next generation CDMA technology. As an all-in-one reference for telecommunications engineers, advanced R & D personnels, undergraduate and postgraduate students, this book is must-read material. Addresses various important issues about the next generation CDMA technologies as the major air-link technology for beyond 3G wireless applications. Covers topics from next generation CDMA system modelling to analytical methodology, starting with the basics and progressing to advanced research topics. Contains many new and previously unpublished research results. Introduces many innovative CDMA technologies such as DS/CC-CDMA, OS/CC-CDMA, space-time complementary coding CDMA, M-ary CDMA, optical complementary coded CDMA, etc.
Author:
Publisher:
ISBN:
Category : Spread spectrum communications
Languages : en
Pages : 128
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Book Description
Author: Pieter van Rooyen
Publisher: Springer Science & Business Media
ISBN: 0306473259
Category : Technology & Engineering
Languages : en
Pages : 320
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Book Description
Space-Time Processing for CDMA Mobile Communications is one of the first books to: bring together spatial/temporal channel models and analytic performance evaluation techniques; establish a link between smart antenna systems and advanced receiver design techniques; treat smart antennas specifically for UMTS-like communication systems, with applicable simulations and calculations; supply code with Matlab® GUI so readers can run or modify existing simulations or create new ones. The field of smart antenna technology or, more generally, space-time processing is rapidly becoming one of the most promising areas of mobile communications, especially regarding the development of the first practical third-generation mobile communication systems. The authors have addressed many of the most basic questions relating to the use of space-time processing in CDMA-based third-generation systems and have presented models for the integration of space-time processing, error correction coding, and multi-user detection techniques. Included is extensive background information on cellular systems, antenna array theory, smart antenna techniques, performance of basic space-time processors and advanced space-time processors. The book also includes an extensive simulation program written in Matlab®. The simulation code implements both the uplink and the downlink of a UMTS-like communication system. This provides multiple options for simulating system performance using a variety of channel models as well as receiver structures. Space-Time Processing for CDMA Mobile Communications will be an invaluable reference work for engineers and researchers, and a useful source for design engineers enabling them to understand the implications of adding space-time processing systems to CDMA-based communication systems.
Author: Khaled Fazel
Publisher: John Wiley & Sons
ISBN: 0470714239
Category : Technology & Engineering
Languages : en
Pages : 384
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Book Description
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.
Author: Lajos L. Hanzo
Publisher: Wiley-IEEE Press
ISBN: 9780470863091
Category : Technology & Engineering
Languages : en
Pages : 1104
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Book Description
This volume is dedicated to a range of CDMA and MC-CDMA transmission aspects of systems designed for communicating over fading wireless channels. Currently, a technical in-depth book on this subject, which has a similar detailed exposure of the recent advances in CDMA, M-ary CDMA and MC-CDMA, is unavailable. 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 five main parts: Part I: provides a detailed introduction to the subject of CDMA systems designed for employment in various application Part II: deals with the currently hot topic of genetic algorithm assisted multiuser detection Part III: gives a detailed account of new, reduced-complexity M-ary CDMA schemes Part IV: considers a range of novel MC-CDMA schemes which have the potential of supporting numerous design objectives Part V: provides an overview of the 3G wireless system proposals and characterises the expected network capacity gains attained with the aid of adaptive CDMA systems By providing an all-encompassing self-contained treatment this groundbreaking volume will have appeal to researchers, postgraduate students, academics practising research and development engineers working for wireless communications and computer networking companies, as well as senior undergraduate students and technical managers in the field.
