Khaled Fazel

Bio: Khaled Fazel is an academic researcher from German Aerospace Center. The author has contributed to research in topics: Orthogonal frequency-division multiplexing & Transmission (telecommunications). The author has an hindex of 10, co-authored 20 publications receiving 1385 citations.

Multi-Carrier and Spread Spectrum Systems

Abstract: From the Publisher: Frequency spectrum is a limited and valuable resource for wireless communications. A good example can be observed among network operators in Europe for the prices to pay for UMTS-frequency bands. Therefore, the first goal when designing future wireless communication systems (e.g. 4G - fourth generation) has to be the increase in spectral efficiency. The development in digital communications in the past years has enabled efficient modulation and coding techniques for robust and spectral efficient data, speech, audio and video transmission. These are the multi-carrier modulation (e.g. OFDM) and the spread spectrum technique (e.g. DS-CDMA), where OFDM was chosen for broadcast applications (DVB, DAB) as well as for broadband wireless indoor standards (ETSI HIPERLAN-II, IEEE-802.11) and the DS-CDMA was selected in mobile communications (IS-95, third generation mobile radio systems world wide, UMTS/IMT 2000). Since 1993 various combinations of multi-carrier (MC) modulation and the spread spectrum (SS) technique have been introduced and the field of MC-SS communications has become an independent and important research topic with increasing activities. New application fields have been proposed such as high rate cellular mobile, high rate wireless indoor and LMDS. It has been shown that MC-SS offers the high spectral efficiency, robustness and flexibility that is required for the next generation systems. Meanwhile, different alternative hybrid schemes such as OFDM/OFDMA, MC-TDMA, etc. have been deeply analysed and adopted in different international standards (ETSI-BRAN, IEEE-802 & MMAC). Multi-Carrier & Spread-Spectrum: Analysis of Hybrid Air Interfaces draws together all ofthe above mentioned hybrid schemes therefore providing a greatly needed resource for system engineers, telecommunication designers and researchers in order to enable them to develop, build and deploy several schemes based on MC-transmission for the next generation systems (which will be an integration of broadband multimedia services covering both 4G mobile and fixed wireless systems). Offers a complete treatment of multi-carrier, spread-spectrum (SS) and time division multiplexing (TDM) techniquesProvides an in-depth insight into hybrid multiple access techniques based on multi-carrier (MC) transmissionPresents numerous hybrid multiple access and air interface architectures including OFDM/CDMA, MC-CDMA, MC-DS-CDMA and MT-CDMACovers new techniques such as space-time coding and software radio Telecommunications engineers, hardware & software system designers and researchers as well as students, lecturers and technicians will all find this an invaluable addition to their bookshelf.

A flexible and high performance cellular mobile communications system based on Orthogonal Multi-Carrier SSMA

Abstract: The conventional Direct-Sequence Spread-Spectrum-Multiple-Access (DS-SSMA) system with RAKE-receiver is an interesting approach in mobile communications in order to combat the frequency selectivity of the channel. The main advantages of DS-SSMA are well known, but its capacity is limited by other-user interference. Another interesting SSMA technique that combats the frequency selectivity of the channel and achieves high spectral efficiency is based on Orthogonal-Frequency-Division-Multiplexing (OFDM). This new SSMA technique combines the principles of DS-SSMA with OFDM and is called Multi-Carrier Spread-Spectrum-Multiple-Access (MC-SSMA). By providing high frequency diversity, this combination enables the possibility to perform a maximum-likelihood detection (MLD) resulting in high performance/capacity, to use the spectrum in an efficient way and to retain many advantages of the conventional DS-SSMA system. In addition, it allows both simple cell-separation by using frequency hopping and simple hardware realization. An example for the downlink of a mobile communications system, i.e. the transmission from the base station to a mobile station, using MC-SSMA with Walsh-Hadamard code spreading is studied. Different coherent detection algorithms such as conventional detection, MLD, and iterative detection are analyzed. The analytical performance of MLD is evaluated. It is also shown analytically, and by simulations that the MC-SSMA system with MLD outperforms the DS-SSMA system with RAKE-receiver. Up to 64 active users can be transmitted in a 1.25 MHz bandwidth. Each user has a rate of 16.0 kbit/s by using BPSK modulation. At a signal to noise ratio (SNR) of 13 dB a bit error probability ofP b =10−3 can be guaranteed without channel coding. This results in a spectral efficiency of about 0.8 bit/s/Hz. Under the same conditions the conventional DS-SSMA system results in a spectral efficiency of about 0.15 bit/s/Hz. Hence, using MC-SSMA for the downlink of a cellular mobile communications system is a promising approach.

Multi-carrier spread-spectrum

Abstract: I. General Issues of Multi-Carrier Spread-Spectrum. Multi-Carrier Spread-Spectrum: An Attractive Special Case of General Multiuser/Multisubchannel Transmission Methods J. Lindner Overview of the Results About Multi-Tone CDMA Detection L. Vandendorpe. Comparison of Multiple Access Schemes for an OFDM Downlink System H. Rohling, et al. Link/System Level Performance of an OFDM/CDMA Downlink Configuration J.P. Castro, et al. II. Applications of Multi-Carrier Spread-Spectrum. Performance Analysis of a New Multi-Code and Multi-Carrier Hybrid Transmission Scheme for Future Broadband Mobile Communication Systems H. Harada, R. Prasad. A Spread-Spectrum Multi-Carrier Multiple-Access System for Mobile Communications S. Kaiser, K. Fazel. Orthogonal Frequency-Division Multiple-Access with Frequency Hopping and Diversity H. Sari. M-ary Orthogonal Modulation for MC-CDMA Systems in Indoor Wireless Radio Networks A. Dekorsy, K.-D. Kammeyer. Comparison of WLAN Multi-Carrier DS-SS Physical Layer Configurations Measured Indoor Environment P. Banelli, et al. III. Coding and Detection for MC-SS. Multi-Carrier CDMA Using Convolutional Coding and Interference Cancellation over Fading Channels J.J. Maxey, R.F. Ormondroyd. An Approach for a Multi-Carrier Spread-Spectrum System with RAKE Receiver A. Nahler, G.P. Fettweis. Multi-Carrier Modulated Orthogonal Code-Division Multiple-Access: D.Th. Magill. Interleaved FDMA - A New Spread-Spectrum Multiple-Access Scheme U. Sorger, et al. Aspects on Wideband Multi-Carrier Communication J.E.M. Nilsson. Equalization and Coding for Extended MC-CDMA over Time and Frequency Selective Channels J. Egle, et al. Detection Method for MC-CDMA Based on a Recurrent Neural Network Structure W.G. Teich, et al. IV. Synchronisation and Channel Estimation. Sensitivity of OFDM/CDMA to Carrier Phase Jitter H. Steendam, M. Moeneclaey. Time Domain Uplink Channel Estimation in Multi-Carrier CDMA Mobile Radio System Concepts B. Steiner. Subspace-Based Joint Time-Delay and Frequency-Shift Estimation in Multi-Tone Code Division Multiple Access (MT-CDMA) Systems M. Eric, et al. Pilot-Symbol-Aided Channel Estimation in Time and Frequency P. Hoeher, et al. A Family of Extended Gaussian Functions with a Nearly Optimal Localization Property Ch. Roche, P. Siohan. On the Duality of Multi-Carrier Spread-Spectrum and Single-Carrier Transmission K. Brueninghaus, H. Rohling. Mismatched Multi-Carrier Complementary Spread-Spectrum Radar and Sonar Systems I.S. Simic, et al. V. MC-SS for the Uplink of a Cellular System. An OFDM/SFH-CDMA Transmission Scheme for the Uplink L. Tomba, W. Krzymien. Uplink Spectral Efficiency of Multi-Carrier Joint Detection Code-Division Multiple-Access Based Cellular Radio Systems F. Berens, et al. Simulation of a DSSS/MCM System in a Doppler Spread Channel T.B. Welch, R.E. Ziemer. On the Performance of Asynchronous Multi-Carrier CDMA H. Ochiai, H. Imai. Performance Comparison B.

Radio transmission method for digital multimedia data signals between subscriber stations in a local network

Abstract: In the radio transmission method according to the invention, which operates with a mixed frequency and time division multiplex method FDMA/TDMA, in which a relatively broad frequency band is divided according to the FDMA method into a plurality of carrier frequency ranges, namely the so-called main channels, and a plurality of time slots, namely the so-called sub-channels, distributed in a frame structure, are formed on each carrier frequency level according to the TDMA method, a grouping, that is to say a so-called cluster, of subscriber stations is assigned a limited number of main channels. A main channel signal is divided into one or more sub-channel signals which are associated with a cluster and which are transmitted using the TDMA method. Each transmitter of an activated subscriber station transmits a detectable check signal, so that, on the basis of detection of a check signal in the respective receiver, other, newly activated subscriber stations can determine the presence of transmit signals which are present within a specific, spatially limited range, namely their own respective transmission range. The method according to the invention can be used for transmitting information between terminals in indoor networks in a wireless manner without a central station.

Method for digital transmission of hierarchical HDTV, EDTV and SDTV television signals

Abstract: For digital transmission of hierarchical HDTV, EDTV and SDTV television signals, on the transmission side after an analog/digital conversion of video and audio input signals and a subsequent removal of redundancy in a source coder, the signal bits are protected in a UEP coder in accordance with their significance. Thereafter, the hierarchically built up television signals (HDTV, EDTV and SDTV) are subjected to a multilevel coding and, combined to form symbols, to a multiresolution modulation and an OFD multiplexing and transmitted after digital/analog conversion. On the receiving side the transmitted signals, after analog/digital reconversion and inverse OED multiplexing (OFDM), are demodulated in a multiresolution demodulator and then decoded in a multistage decoder. Thereupon the data are processed by digital/analog conversion to HDTV, EDTV and SDTV signals in a UEP decoder specific to the respective receiver and a following source decoder.

OFDM and Its Wireless Applications: A Survey

Abstract: Orthogonal frequency-division multiplexing (OFDM) effectively mitigates intersymbol interference (ISI) caused by the delay spread of wireless channels. Therefore, it has been used in many wireless systems and adopted by various standards. In this paper, we present a comprehensive survey on OFDM for wireless communications. We address basic OFDM and related modulations, as well as techniques to improve the performance of OFDM for wireless communications, including channel estimation and signal detection, time- and frequency-offset estimation and correction, peak-to-average power ratio reduction, and multiple-input-multiple-output (MIMO) techniques. We also describe the applications of OFDM in current systems and standards.

Multi-Carrier and Spread Spectrum Systems

Abstract: From the Publisher: Frequency spectrum is a limited and valuable resource for wireless communications. A good example can be observed among network operators in Europe for the prices to pay for UMTS-frequency bands. Therefore, the first goal when designing future wireless communication systems (e.g. 4G - fourth generation) has to be the increase in spectral efficiency. The development in digital communications in the past years has enabled efficient modulation and coding techniques for robust and spectral efficient data, speech, audio and video transmission. These are the multi-carrier modulation (e.g. OFDM) and the spread spectrum technique (e.g. DS-CDMA), where OFDM was chosen for broadcast applications (DVB, DAB) as well as for broadband wireless indoor standards (ETSI HIPERLAN-II, IEEE-802.11) and the DS-CDMA was selected in mobile communications (IS-95, third generation mobile radio systems world wide, UMTS/IMT 2000). Since 1993 various combinations of multi-carrier (MC) modulation and the spread spectrum (SS) technique have been introduced and the field of MC-SS communications has become an independent and important research topic with increasing activities. New application fields have been proposed such as high rate cellular mobile, high rate wireless indoor and LMDS. It has been shown that MC-SS offers the high spectral efficiency, robustness and flexibility that is required for the next generation systems. Meanwhile, different alternative hybrid schemes such as OFDM/OFDMA, MC-TDMA, etc. have been deeply analysed and adopted in different international standards (ETSI-BRAN, IEEE-802 & MMAC). Multi-Carrier & Spread-Spectrum: Analysis of Hybrid Air Interfaces draws together all ofthe above mentioned hybrid schemes therefore providing a greatly needed resource for system engineers, telecommunication designers and researchers in order to enable them to develop, build and deploy several schemes based on MC-transmission for the next generation systems (which will be an integration of broadband multimedia services covering both 4G mobile and fixed wireless systems). Offers a complete treatment of multi-carrier, spread-spectrum (SS) and time division multiplexing (TDM) techniquesProvides an in-depth insight into hybrid multiple access techniques based on multi-carrier (MC) transmissionPresents numerous hybrid multiple access and air interface architectures including OFDM/CDMA, MC-CDMA, MC-DS-CDMA and MT-CDMACovers new techniques such as space-time coding and software radio Telecommunications engineers, hardware & software system designers and researchers as well as students, lecturers and technicians will all find this an invaluable addition to their bookshelf.

OFDM and MC-CDMA for Broadband Multi-User Communications, WLANs and Broadcasting

Abstract: From the Publisher: 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 theentire body of knowledge currently available on OFDMProvides the first complete treatment of OFDM, MIMO(Multiple Input Multiple Output)-OFDM and MC-CDMAConsiders the benefits of channel coding and space time coding in the context of various application examples and features numerous complete system design examplesConverts the lessons of Shannon's information theory into design principles applicable to practical wireless systemsCombines 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.

Prolog to adaptive multicarrier modulation: a convenient framework for time-frequency processing in wireless communications

Abstract: A historical perspective of orthogonal frequency-division multiplexing (OFDM) is given with reference to its literature. Its advantages and disadvantages are reviewed, and its performance is characterized over highly dispersive channels. The effects of both time- and frequency-domain synchronization errors are quantified, and a range of solutions proposed in the recent literature are reviewed. One of the main objectives of this review is to highlight the recent thinking behind adaptive bit allocation and turbo coding in the context of OFDM. This paper concludes with a wide-ranging throughput comparison of the schemes discussed herein under the unified constraint of a fixed target bit error rate of 10/sup -4/.

Design and performance of multicarrier CDMA system in frequency-selective Rayleigh fading channels

Abstract: This paper presents the advantages and disadvantages of a multicarrier code-division multiple-access (MC-CDMA) system. The transmitter/receiver structure and, the bandwidth of transmitted signal spectrum are compared with those of a conventional direct-sequence (DS) CDMA system, and an MC-CDMA design method, how to determine the number of subcarriers and the length of guard interval is discussed. The bit error rate (BER) lower bounds for DS-CDMA and MC-CDMA systems are derived and their equivalence is theoretically demonstrated. Finally, the BER performance in downlink and uplink channels with frequency-selective Rayleigh fading is shown by computer simulation.