Download or read book Carrier Frequency Offset Synchronization and Phase Noise Compensation in Optical OFDM Systems written by Muyiwa Blessing Balogun and published by . This book was released on 2018 with total page 248 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Investigation on High Spectral Efficiency Coherent Optical OFDM Transmission Systems written by Hussin Saleh Ibrahim Saied Saleh and published by . This book was released on 2015 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Orthogonal frequency division multiplexing (OFDM) belongs to multicarrier technology which is used in many broadband wired and wireless communication systems. It is used to combat multipath fading. Although, OFDM systems are complex compared to single carrier systems due to design of their transmitter and receiver and also the associated signal processing, significant benefits are achieved. Optical OFDM systems can be classified into three approaches according to the detection scheme. The approaches are direct detection optical OFDM (DDO-OFDM), coherent optical OFDM (CO-OFDM) and self coherent optical OFDM (SCO-OFDM). The most important drawbacks of CO-OFDM are the high peak-to-average power ratio (PAPR), high sensitivity to frequency offset and phase noise. The present dissertation introduces the performance of different pulse shaping techniques. Furthermore, it presents new algorithms to reduce the phase noise effects and compares the system performance with different existing algorithms. Moreover, the performance of a new system design is investigated. The provided dissertation includes four original contributions.Initially, the theoretical principles of OFDM are presented with detailing on the advantages and disadvantages of OFDM compared to the single carrier modulation technology. The theoretical fundamentals of optical OFDM and the differences between the three systems are followed. Furthermore, performance of the three existing optical OFDM systems are elaborated and compared. A square root raised-cosine pulse shaping of OFDM symbols is suggested to enhance the efficiency of CO-OFDM systems. Next, the different kinds of the phase noise effects on the OFDM signals are defined and the impact of the laser and nonlinear phase noise is reported. Different existing phase noise compensation algorithms are presented. Moreover, the modified and new phase noise compensation schemes are provided and compared. ; eng

Download or read book Investigation of Receiver Concepts for Coherent Optical Orthogonal Frequency Division Multiplexing Communication Systems written by Kidsanapong Puntsri and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book OFDM for Optical Communications written by William Shieh and published by Academic Press. This book was released on 2009-09-18 with total page 457 pages. Available in PDF, EPUB and Kindle. Book excerpt: The first book on optical OFDM by the leading pioneers in the field The only book to cover error correction codes for optical OFDM Gives applications of OFDM to free-space communications, optical access networks, and metro and log haul transports show optical OFDM can be implemented Contains introductions to signal processing for optical engineers and optical communication fundamentals for wireless engineers This book gives a coherent and comprehensive introduction to the fundamentals of OFDM signal processing, with a distinctive focus on its broad range of applications. It evaluates the architecture, design and performance of a number of OFDM variations, discusses coded OFDM, and gives a detailed study of error correction codes for access networks, 100 Gb/s Ethernet and future optical networks. The emerging applications of optical OFDM, including single-mode fiber transmission, multimode fiber transmission, free space optical systems, and optical access networks are examined, with particular attention paid to passive optical networks, radio-over-fiber, WiMAX and UWB communications. Written by two of the leading contributors to the field, this book will be a unique reference for optical communications engineers and scientists. Students, technical managers and telecom executives seeking to understand this new technology for future-generation optical networks will find the book invaluable. William Shieh is an associate professor and reader in the electrical and electronic engineering department, The University of Melbourne, Australia. He received his M.S. degree in electrical engineering and Ph.D. degree in physics both from University of Southern California. Ivan Djordjevic is an Assistant Professor of Electrical and Computer Engineering at the University of Arizona, Tucson, where he directs the Optical Communications Systems Laboratory (OCSL). His current research interests include optical networks, error control coding, constrained coding, coded modulation, turbo equalization, OFDM applications, and quantum error correction. "This wonderful book is the first one to address the rapidly emerging optical OFDM field. Written by two leading researchers in the field, the book is structured to comprehensively cover any optical OFDM aspect one could possibly think of, from the most fundamental to the most specialized. The book adopts a coherent line of presentation, while striking a thoughtful balance between the various topics, gradually developing the optical-physics and communication-theoretic concepts required for deep comprehension of the topic, eventually treating the multiple optical OFDM methods, variations and applications. In my view this book will remain relevant for many years to come, and will be increasingly accessed by graduate students, accomplished researchers as well as telecommunication engineers and managers keen to attain a perspective on the emerging role of OFDM in the evolution of photonic networks." -- Prof. Moshe Nazarathy, EE Dept., Technion, Israel Institute of Technology The first book on optical OFDM by the leading pioneers in the field The only book to cover error correction codes for optical OFDM Applications of OFDM to free-space communications, optical access networks, and metro and log haul transports show optical OFDM can be implemented An introduction to signal processing for optical communications An introduction to optical communication fundamentals for the wireless engineer

Download or read book Synchronization Algorithms for OFDM Systems IEEE802 11a DVB T written by Charbel el Hajjar and published by . This book was released on 2008 with total page 166 pages. Available in PDF, EPUB and Kindle. Book excerpt: Orthogonal Frequency Division Multiplexing (OFDM) or Multi-carrier Modulation (MCM) is a digital modulation technique that supports high-rate data with sufficient robustness to radio channel impairments (especially multi-path propagation). Due to that, it is emerging as the modulation technique used for the new generation of wireless communication systems (IEEE802.11a and DVB-T). However, one of the arguments against OFDM is that it is highly sensitive to synchronization errors. This raises up the need for optimum synchronization algorithms for OFDM applications such as IEEE802.11a and DVB-T. In this thesis, several synchronization algorithms are presented. Those algorithms deal mainly with two important synchronization problems: Timing and frequency errors and their consequences. We focus on the implementation aspects of synchronization algorithms and propose optimizations which lead to well performing and robust fixed point implementations. In addition, complexity and cost needed for such a project are analyzed leading to a model for classifying different algorithms depending on cost, time-to-market, and performance.

Download or read book A Comparative Analysis to Remove CFO in OFDM System written by Santosh Gupta and published by LAP Lambert Academic Publishing. This book was released on 2012 with total page 72 pages. Available in PDF, EPUB and Kindle. Book excerpt: The most important aspect in an OFDM is frequency and time synchronization as this form the reason for orthogonality between the subcarriers. However OFDM is susceptible to synchronization errors between transmitter and receiver local oscillator frequencies. This error is known as the carrier frequency offset (CFO) and causes ICI and also destroys the orthogonality between the subcarriers. In this literature we study the effects that CFO can cause to the SNR in an OFDM system, estimate the amount of frequency offset. Also the performance of the estimate is studied in a multipath environment. This book discusses and investigates the estimation of carrier offset frequency in orthogonal frequency division multiplexing (OFDM) mobile systems. Although OFDM is resistant to multipath fading, it requires a high degree of synchronization to maintain sub-carrier orthogonality. Therefore the level of performance of the system depends first on the accuracy in estimating the carrier frequency offset and then the estimation of the channel.

Download or read book Analysis of the Effects of Phase Noise and Frequency Offset in Orthogonal Frequency Division Multiplexing OFDM Systems written by Ahmet Y. Erdogan and published by . This book was released on 2004-03-01 with total page 151 pages. Available in PDF, EPUB and Kindle. Book excerpt: Orthogonal frequency division multiplexing (OFDM) is being successfully used in numerous applications. It was chosen for IEEE 802.1 la wireless local area network (WLAN) standard, and it is being considered for the fourth- generation mobile communication systems. Along with its many attractive features, OFDM has some principal draw-backs. Sensitivity to frequency errors is the most dominant of these drawbacks. In this thesis, the frequency offset and phase noise effects on OFDM based communication systems are investigated under a variety of channel conditions covering both indoor and outdoor environments. The simulation performance results of the OFDM system for these channels are presented.

Download or read book Orthogonal Frequency division Multiplexing for Optical Communications written by Daniel Jose Fernandes Barros and published by Stanford University. This book was released on 2011 with total page 160 pages. Available in PDF, EPUB and Kindle. Book excerpt: The drive towards higher spectral efficiency and maximum power efficiency in optical systems has generated renewed interest in the optimization of optical transceivers. In this work, we study the different optical applications: Wide Area Networks (WANs), Metropolitan Area Networks (MANs), Local Area Networks (LANs) and Personal Area Networks (PANs). In WANs or long-haul systems, orthogonal frequency-division multiplexing (OFDM) can compensate for linear distortions, such as group-velocity dispersion (GVD) and polarization-mode dispersion (PMD), provided the cyclic prefix is sufficiently long. Typically, GVD is dominant, as it requires a longer cyclic prefix. Assuming coherent detection, we show how to analytically compute the minimum number of subcarriers and cyclic prefix length required to achieve a specified power penalty, trading off power penalties from the cyclic prefix and from residual inter-symbol interference (ISI) and inter-carrier interference (ICI). We derive an analytical expression for the power penalty from residual ISI and ICI. We also show that when nonlinear effects are present in the fiber, single-carrier with digital equalization outperforms OFDM for various dispersion maps. We also study the impairments of electrical to optical conversion when using Mach-Zehnder (MZ) modulators. OFDM has a high peak-to-average ratio (PAR), which can result in low optical power efficiency when modulated through a Mach-Zehnder (MZ) modulator. In addition, the nonlinear characteristic of the MZ can cause significant distortion on the OFDM signal, leading to in-band intermodulation products between subcarriers. We show that a quadrature MZ with digital pre-distortion and hard clipping is able to overcome the previous impairments. We consider quantization noise and compute the minimum number of bits required in the digital-to-analog converter (D/A). Finally, we discuss a dual-drive MZ as a simpler alternative for the OFDM modulator, but our results show that it requires a higher oversampling ratio to achieve the same performance as the quadrature MZ. In MANs, we discuss the use OFDM for combating GVD effects in amplified direct-detection (DD) systems using single-mode fiber. We review known direct-detection OFDM techniques, including asymmetrically clipped optical OFDM (ACO-OFDM), DC-clipped OFDM (DC-OFDM) and single-sideband OFDM (SSB-OFDM), and derive a linearized channel model for each technique. We present an iterative procedure to achieve optimum power allocation for each OFDM technique, since there is no closed-form solution for amplified DD systems. For each technique, we minimize the optical power required to transmit at a given bit rate and normalized GVD by iteratively adjusting the bias and optimizing the power allocation among the subcarriers. We verify that SSB-OFDM has the best optical power efficiency among the different OFDM techniques. We compare these OFDM techniques to on-off keying (OOK) with maximum-likelihood sequence detection (MLSD) and show that SSB-OFDM can achieve the same optical power efficiency as OOK with MLSD, but at the cost of requiring twice the electrical bandwidth and also a complex quadrature modulator. We compare the computational complexity of the different techniques and show that SSB-OFDM requires fewer operations per bit than OOK with MLSD. In LANs, we compare the performance of several OFDM schemes to that of OOK in combating modal dispersion in multimode fiber links. We review known OFDM techniques using intensity modulation with direct detection (IM/DD), including DC-OFDM, ACO-OFDM and pulse-amplitude modulated discrete multitone (PAM-DMT). We describe an iterative procedure to achieve optimal power allocation for DC-OFDM, and compare analytically the performance of ACO-OFDM and PAM-DMT. We also consider unipolar M-ary pulse-amplitude modulation (M-PAM) with minimum mean-square error decision-feedback equalization (MMSE-DFE). For each technique, we quantify the optical power required to transmit at a given bit rate in a variety of multimode fibers. For a given symbol rate, we find that unipolar M-PAM with MMSE-DFE has a better power performance than all OFDM formats. Furthermore, we observe that the difference in performance between M-PAM and OFDM increases as the spectral efficiency increases. We also find that at a spectral efficiency of 1 bit/symbol, OOK performs better than ACO-OFDM using a symbol rate twice that of OOK. At higher spectral efficiencies, M-PAM performs only slightly better than ACO-OFDM using twice the symbol rate, but requires less electrical bandwidth and can employ analog-to-digital converters at a speed only 81% of that required for ACO-OFDM. In PANs, we evaluate the performance of the three IM/DD OFDM schemes in combating multipath distortion in indoor optical wireless links, comparing them to unipolar M-PAM with MMSE-DFE. For each modulation method, we quantify the received electrical SNR required at a given bit rate on a given channel, considering an ensemble of 170 indoor wireless channels. When using the same symbol rate for all modulation methods, M-PAM with MMSE-DFE has better performance than any OFDM format over a range of spectral efficiencies, with the advantage of M-PAM increasing at high spectral efficiency. ACO-OFDM and PAM-DMT have practically identical performance at any spectral efficiency. They are the best OFDM formats at low spectral efficiency, whereas DC-OFDM is best at high spectral efficiency. When ACO-OFDM or PAM-DMT are allowed to use twice the symbol rate of M-PAM, these OFDM formats have better performance than M-PAM. When channel state information is unavailable at the transmitter, however, M-PAM significantly outperforms all OFDM formats. When using the same symbol rate for all modulation methods, M-PAM requires approximately three times more computational complexity per processor than all OFDM formats and 63% faster analog-to-digital converters, assuming oversampling ratios of 1.23 and 2 for ACO-OFDM and M-PAM, respectively. When OFDM uses twice the symbol rate of M-PAM, OFDM requires 23% faster analog-to-digital converters than M-PAM but OFDM requires approximately 40% less computational complexity than M-PAM per processor.

Download or read book Phase Noise in OFDM written by Kamayani Shrivastav and published by . This book was released on 2018 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Orthogonal frequency division multiplexing (OFDM) technique provides high data rate with high spectral efficiency for operating close to the Shanon capacity bounds. With the advantages of simple channel equalization, robustness against frequency selectivity of the channel, and efficient implementation, this is a widely deployed technique. Orthogonal frequency division multiplexing access (OFDMA), the multiple access technique using OFDM, has the great potential for providing high spectral efficiency due to its integrated space-frequency and multiuser diversity. Besides all the advantages, OFDM/A is very susceptible to transceiver,Äôs impairments such as phase noise (PHN), carrier frequency offset, and in-quadrature phase imbalance effect. Phase noise is the random fluctuation in phase of the sinusoidal waveform used for frequency up/down conversion of baseband signals to/from RF (radio frequency). This occurs due to the inherent imperfections of oscillators used for this purpose. This chapter addresses the orthogonal frequency division multiplexing/multiple access system performance under the impact of transceiver oscillator phase noise.

Download or read book Phase Noise Compensation for Long haul Coherent Optical Communication Systems Using OFDM written by Jingwen Zhu and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Long-haul optical transmission systems employing coherent optical orthogonal frequency division multiplexing (CO-OFDM) are sensitive to laser phase noise. This causes a common phase rotation and inter-carrier interference. An effective method to compensate for the phase noise is to insert an RF-pilot tone in the middle of the OFDM signal. This RF-pilot is used to reverse the phase distortion at the receiver. This thesis presents a detailed performance analysis of the RF-pilot phase noise compensation scheme in a simulated 64 Gbit/s CO-OFDM system. The effects of various parameters including laser linewidth, Mach-Zehnder modulator drive power, pilot-tosignal ratio, and fiber launch power are investigated. A comparison with the pilot-aided common phase error compensation method is provided to show the differences in the BER performance with respect to the required overhead.

Download or read book Timing and Frequency Synchronization in Practical OFDM Systems written by Ming Ruan and published by . This book was released on 2009 with total page 221 pages. Available in PDF, EPUB and Kindle. Book excerpt: Orthogonal frequency-division multiplexing (OFDM) has been adopted by many broadband wireless communication systems for the simplicity of the receiver technique to support high data rates and user mobility. However, studies also show that the advantage of OFDM over the single-carrier modulation schemes could be substantially compromised by timing or frequency estimation errors at the receiver. In this thesis we investigate the synchronization problem for practical OFDM systems using a system model generalized from the IEEE 802.11 and IEEE 802.16 standards. For preamble based synchronization schemes, which are most common in the downlink of wireless communication systems, we propose a novel timing acquisition algorithm which minimizes false alarm probability and indirectly improves correct detection probability. We then introduce a universal fractional carrier frequency offset (CFO) estimator that outperforms conventional methods at low signal to noise ratio with lower complexity. More accurate timing and frequency estimates can be obtained by our proposed frequency-domain algorithms incorporating channel knowledge. We derive four joint frequency, timing, and channel estimators with different approximations, and then propose a hybrid integer CFO estimation scheme to provide flexible performance and complexity tradeoffs. When the exact channel delay profile is unknown at the receiver, we present a successive timing estimation algorithm to solve the timing ambiguity. Both analytical and simulation results are presented to confirm the performance of the proposed methods in various realistic channel conditions. ...

Download or read book Adaptive Decision directed Channel Equalization and Laser Phase Noise Induced Inter carrier inteference Mitigation for Coherent Optical Orthogonal Frequency Division Multiplexing Transport Systems written by Mohammad Mousa Pasandi and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: "The explosive growth of global Internet traffic has placed tremendous strain on both op-tical networks and optical transmission systems, underscoring the need for not only high-capacity transmission links but also for flexible, reconfigurable, and adaptive networks. Recent progress in complementary metal-oxide-semiconductor (CMOS) technology has facilitated the use of digital signal processing (DSP) in optical communication systems. Blessed with the revival of coherent optical transmission systems, over the past few years, DSP-enabled, software-defined optical transmission (SDOT) systems have led the funda-mental paradigm shift from inflexible optical networks to robust, reconfigurable, plug-and-play optical networks.Recently, coherent optical orthogonal frequency division multiplexing (CO-OFDM) has been intensively investigated as a promising modulation format for realizing coherent transmission systems. Although CO-OFDM has attracted significant interest in the research community, it has yet to leave a tangible impact on the commercial front due to implemen-tation shortcomings, such as excessive overhead, and susceptibility to fibre nonlinearities and frequency/phase noise.This thesis explores DSP-based solutions for CO-OFDM transmission systems, including two key original contributions. The first contribution is a novel adaptive decision-directed channel equalizer (ADDCE) that aims to reduce the required overhead in CO-OFDM transmission systems. ADDCE retrieves an estimation of the phase noise value after an initial decision making stage, by extracting and averaging the phase drift of all OFDM sub-channels, demonstrating zero-overhead phase noise compensation. Moreover, it updates the channel transfer matrix on a symbol-by-symbol basis, thus enabling a reduction in the associated overhead with pilot symbols. The second original contribution of this thesis focuses on the mitigation of the effect of the laser phase noise induced inter-carrier interfer-ence (ICI) in CO-OFDM systems. This interpolation-based ICI compensator estimates the time-domain phase noise samples using linear interpolation between the common-phase-error (CPE) estimates of consecutive OFDM symbols.The performances of the aforementioned DSP equalization schemes are numerically and experimentally studied in reduced-guard-interval dual-polarization CO-OFDM (RGI-DP-CO-OFDM) transmission systems, and are found to demonstrate superior performance over conventional equalizers (CEs). In addition, a computational complexity analysis of the pro-posed equalizers is provided, which confirms a low implementation complexity." --

Download or read book Decision aided Baseband Compensation for Phase Noise in Wireless OFDM Systems written by Aditya Awasthi and published by . This book was released on 2008 with total page 150 pages. Available in PDF, EPUB and Kindle. Book excerpt: Performance of orthogonal frequency division multiplexing (OFDM)-based wireless communication system is severely degraded by the presence of phase noise. Phase noise can reduce the effective signal-to-noise ratio (SNR) at the receiver, and consequently, limit the bit error rate (BER) and data rate of the wireless system.

Download or read book Synchronization Algorithms and Architectures for Wireless OFDM Systems written by Sedki Bakir Thanoon Younis and published by . This book was released on 2012 with total page 197 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Effects and Performance Analysis of Non linear Phase Noise in All Optical OFDM Systems written by Iraj Sadegh Amiri and published by . This book was released on 2018 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Due to the limitation of the electrical OFDM signal and electrical Fast Fourier Transform (FFT), all-optical OFDMs have recently received much attention. Accordingly, this research study was conducted to investigate the effect of phase noise in the performance of an all-optical OFDM transmission system with 4-point FFT single mode fiber (SMF) links by considering the effects of fiber length, input laser power and a number of channels. In all optical systems, the transmitter side consists of a comb power generator, wavelength selected switch and an optical QAM generator. A comb power generator generates channels with a frequency separation of ∆f=25 GHz. Subsequently, a Wavelength Selected Switch (WSS) was used to split subcarriers and then the subcarriers were modulated individually with Optical QAM modulators. As the results show, a higher number of channels led more phase noise in terms of XPM and FWM nonlinearities, and signal power was the main factor in nonlinear fiber optics. As a consequence, there is more phase noise distortion at a higher signal power for a higher number of channels rather than the lower number of channels.

Download or read book A Double Dwell Frequency Synchronization Scheme for OFDM Systems written by Nour Ali Kousa and published by . This book was released on 2015 with total page 95 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Orthogonal Frequency Division Multiplexing (OFDM) is being used in many recent communication systems to cope with the demand for high data rate applications. It provides a significant improvement in the bandwidth efficiency with simple equalization at the receiver. ODFM systems provide high immunity against multipath fading and inter symbol interference (ISI) since the high data rate stream is divided among narrow overlapping but orthogonal subcarriers. However, OFDM requires accurate timing and frequency synchronization to preserve the orthogonality between subcarriers and maintain acceptable performance. Achieving accurate synchronization is a challenging task in multicarrier systems such as OFDM. It is noticed that frequency synchronization is more critical in OFDM than timing synchronization since a small frequency offset can destroy the orthogonality among the subcarriers causing inter-carrier interference (ICI), which results in serious performance degradation. In this thesis, the effect of frequency offset on OFDM system performance is investigated and a new synchronization scheme based on the Double Dwell System (DDS) is proposed. In DDS, the frequency offset estimation is carried over two stages: a coarse estimate is obtained over the first stage followed by a fine estimate in the second stage. The system performance is evaluated in terms of the mean square error (MSE) and symbol error rate (SER) and is compared to the conventional Single Dwell System (SDS). Simulation results show a significant performance improvement in the proposed method over SDS. Other results are presented in this thesis such as interference impact, pilot symbol design, optimization of search window and step size, and mitigation of fading effects."--Abstract.

Download or read book Information Technology and Intelligent Transportation Systems written by Valentina Emilia Balas and published by Springer. This book was released on 2016-11-08 with total page 702 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume includes the proceedings of the 2015 International Conference on Information Technology and Intelligent Transportation Systems (ITITS 2015) which was held in Xi’an on December 12-13, 2015. The conference provided a platform for all professionals and researchers from industry and academia to present and discuss recent advances in the field of Information Technology and Intelligent Transportation Systems. The presented information technologies are connected to intelligent transportation systems including wireless communication, computational technologies, floating car data/floating cellular data, sensing technologies, and video vehicle detection. The articles focusing on intelligent transport systems vary in the technologies applied, from basic management systems to more application systems including topics such as emergency vehicle notification systems, automatic road enforcement, collision avoidance systems and some cooperative systems. The conference hosted 12 invited speakers and over 200 participants. Each paper was under double peer reviewed by at least 3 reviewers. This proceedings are sponsored by Shaanxi Computer Society and co-sponsored by Chang’an University, Xi’an University of Technology, Northwestern Poly-technical University, CAS, Shaanxi Sirui Industries Co., LTD.