Download or read book Modeling and Performance Analysis of the Orthogonal Frequency Division Multiplexing OFDM Scheme for Radio Over Fiber System written by Yoon Khang Wong and published by . This book was released on 2011 with total page 75 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book IMDC SDSP 2020 written by Raed Abd-Alhameed and published by European Alliance for Innovation. This book was released on 2020-09-09 with total page 1619 pages. Available in PDF, EPUB and Kindle. Book excerpt: IMDC-SDSP conference offers an exceptional platform and opportunity for practitioners, industry experts, technocrats, academics, information scientists, innovators, postgraduate students, and research scholars to share their experiences for the advancement of knowledge and obtain critical feedback on their work. The timing of this conference coincides with the rise of Big Data, Artificial Intelligence powered applications, Cognitive Communications, Green Energy, Adaptive Control and Mobile Robotics towards maintaining the Sustainable Development and Smart Planning and management of the future technologies. It is aimed at the knowledge generated from the integration of the different data sources related to a number of active real-time applications in supporting the smart planning and enhance and sustain a healthy environment. The conference also covers the rise of the digital health, well-being, home care, and patient-centred era for the benefit of patients and healthcare providers; in addition to how supporting the development of a platform of smart Dynamic Health Systems and self-management.

Download or read book The Orthogonal Frequency Division Multiplexing OFDM Introduction and explanation of five different types of techniques written by Dr. Lokesh Chikkananjaiah and published by GRIN Verlag. This book was released on 2021-02-25 with total page 124 pages. Available in PDF, EPUB and Kindle. Book excerpt: Thesis (M.A.) from the year 2019 in the subject Electrotechnology, grade: 9, , language: English, abstract: The Orthogonal Frequency Division Multiplexing (OFDM) is an important aspect of multicarrier digital data transmission system where a single data stream is transmitted into a several number of lower rates subcarrier signals. In this thesis, there are five different types of the techniques introduced to strengthen the communication quality and capacity. This kind of new standard of transmission of data is the first one to perform with OFDM in data packet based communication system. In wireless communication network, the abstraction of parallel transmission of data symbols is implemented to attain high throughput and effective transmission quality. The OFDM is a method to deal with parallel transmission.

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 Index Modulation for OFDM Communications Systems written by Miaowen Wen and published by Springer Nature. This book was released on 2021-01-04 with total page 182 pages. Available in PDF, EPUB and Kindle. Book excerpt: Thanks to their considerable advantages, index modulation and orthogonal frequency division multiplexing (OFDM) are considered to be promising candidates for future wireless communications. This book focuses on the index modulation techniques for OFDM communications systems, which allow information to be conveyed not only via constellation symbols, but also by the indices of various transmission entities in OFDM systems, such as signal constellations, spreading codes, and pilots. The book discusses representative transmitter and receiver designs, optimization and performance analysis of index modulation based on various transmission entities. It first introduces readers to constellation-based index modulation via a combinatorial approach, including the classical index modulation scheme and two embodiments of information-guided precoding for OFDM systems. It further discusses constellation-based index modulation via a permutational approach, including the basic, generalized, and diversity-enhancing forms. It then describes how the spreading code is used to design an index modulated spread spectrum for OFDM systems, and the extensions to multi-code and multi-user scenarios. In addition it explores information guided pilot insertion for OFDM systems, followed by applications to carrier phase tracking and channel estimation. Lastly, the book highlights a number of open problems and discusses future research directions in the general field of index modulation. Intended for professionals and researchers in the field of wireless communications, this book is also a valuable resource for advanced-level electrical engineering and computer science students.

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.

Download or read book OFDM Systems for Wireless Communications written by Adarsh Narasimhamurthy and published by Morgan & Claypool Publishers. This book was released on 2010-02-02 with total page 78 pages. Available in PDF, EPUB and Kindle. Book excerpt: Orthogonal Frequency Division Multiplexing (OFDM) systems are widely used in the standards for digital audio/video broadcasting, WiFi and WiMax. Being a frequency-domain approach to communications, OFDM has important advantages in dealing with the frequency-selective nature of high data rate wireless communication channels. As the needs for operating with higher data rates become more pressing, OFDM systems have emerged as an effective physical-layer solution. This short monograph is intended as a tutorial which highlights the deleterious aspects of the wireless channel and presents why OFDM is a good choice as a modulation that can transmit at high data rates. The system-level approach we shall pursue will also point out the disadvantages of OFDM systems especially in the context of peak to average ratio, and carrier frequency synchronization. Finally, simulation of OFDM systems will be given due prominence. Simple MATLAB programs are provided for bit error rate simulation using a discrete-time OFDM representation. Software is also provided to simulate the effects of inter-block-interference, inter-carrier-interference and signal clipping on the error rate performance. Different components of the OFDM system are described, and detailed implementation notes are provided for the programs. The program can be downloaded here. Table of Contents: Introduction / Modeling Wireless Channels / Baseband OFDM System / Carrier Frequency Offset / Peak to Average Power Ratio / Simulation of the Performance of OFDM Systems / Conclusions

Download or read book Performance Analysis of Orthogonal Frequency Division Multiplexing OFDM and Bandwidth Extension Using Carrier Aggregation CA written by Sandesh Modhe and published by . This book was released on 2015 with total page 128 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis deals with the performance analysis of an Orthogonal Frequency Division Multiplexing (OFDM) system and the bandwidth extension achieved with carrier aggregation (CA). Data, when transmitted through any communications system, primarily faces three types of problems, errors, power management, and bandwidth. For the purpose of analyzing OFDM performance, we have taken a two-fold approach. Different types of modulation schemes such as QPSK and 16-QAM with OFDM are studied for their Bit Error Rate (BER). A noisy channel adversely affects data transmission. For this work, we study the modulation schemes with OFDM over two types of noise channels, Additive White Gaussian Noise (AWGN) and Rayleigh Fading. BER rates for both these channels are studied comparatively. One of the major drawbacks of using an OFDM communications system is its requirement for high power transmitters due to high Peak to Average Power (PAPR) ratios. In this thesis, we reduce the PAPR by using two distinct algorithms, the Partial Transmit Sequence (PTS) and Selective Mapping Technique (SLM). Performance of the OFDM signal by employing both these algorithms is studied. Furthermore, the last part of this work consists of bandwidth extension by using the technique of carrier aggregation. In this technique, we aggregate two sub-carriers to provide a greater bandwidth. CA is achieved by using two methods, contiguous CA and non-contiguous CA.

Download or read book Orthogonal Frequency Division Multiplexing in Optical Communication Systems written by Dr. Ashad Ullah Qureshi and published by Concepts Books Publication. This book was released on 2022-06-01 with total page 30 pages. Available in PDF, EPUB and Kindle. Book excerpt: Optical fiber communication has emerged as a high potential substitute for communication methods such as twisted pair and coaxial wire. The main advantage of optical fiber over previous methods is to have higher capacity of data rate transmission. The conventional types of modulation and demodulation technique, which have been used through optical fiber communication system are Wavelength Division Multiplexing (WDM) technique and Dense Wavelength Division Multiplexing (DWDM) technique so far.

Download or read book Performance Analysis of OFDM System Including PAPR Reduction written by SUBAHA. AHMED MAHMUDA (FEROZ.) and published by LAP Lambert Academic Publishing. This book was released on 2012-05-16 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book discusses the basics of an Orthogonal Frequency Division Multiplexing (OFDM) System and the several radio impairments effects to its Bit Error Rate (BER) performance. Graphical representation of Scatter plot and BER plot for different modulation Schemes, coding schemes and code rates are shown here to analyze the performance of OFDM system. The effects of different Cyclic Prefixes, Pilot channels and Inter-leaver on OFDM system are also observed. Peak-to-Average Power Ratio (PAPR) which is one of the major drawbacks of OFDM system is also discussed here along with the discussion of different PAPR reduction techniques. Finally, a new technique called "Double Companding" by means of multiple companding has been proposed to reduce the PAPR. The simulation results show that it has better performance in terms of PAPR reduction than the conventional companding scheme.

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 OFDM Based RF and Optical Wireless Systems written by Bilal Ranjha and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Orthogonal frequency division multiplexing (OFDM) is currently being used predominantly in radio frequency (RF) mobile broadband communication systems because of its ability to combat inter-symbol interference (ISI) and robustness against frequency selective fading caused by multipath wireless channel. Wireless mobile standards like 3G and 4G long term evolution (LTE) use orthogonal frequency division multiple access (OFDMA) as a multiplexing/modulation scheme. Despite its many advantages like single tap frequency domain equalization and fast discrete time implementation, OFDM suffers from certain disadvantages like high peak-to-average power ratio (PAPR) and high sensitivity to carrier frequency offset (CFO). Although OFDM has solved problems like multipath fading but it cannot solve the emerging problems like scarcity of RF spectrum for mobile wireless broadband applications. Optical wireless (OW) communication has recently gained a lot of attention as a candidate to complement RF communication. It offers advantages like virtually infinite bandwidth, data security and use of low cost transmitters and receivers like solid state light emitting diodes (LEDs) and optical detectors. OFDM is also being considered as a candidate for visible light communication (VLC) as it offers robustness against multipath caused by diffuse indoor OW channel. One way to realize VLC is intensity modulation direct detection (IM/DD). Although the major difference between RF and OW based OFDM lies in the front end of transmitter and receiver, but due to the unipolar nature of optical intensity in IM/DD system, methods of generating baseband OFDM signal, techniques to reduce PAPR and timing synchronization schemes for RF cannot be directly applied to optical OFDM systems and therefore must be revisited. Therefore, in this thesis, we will first look into the interference caused by CFO in RF based OFDMA system and will analyze the characteristics of this interference for two mapping subcarrier strategies. We will explicitly calculate SINR expression for OFDMA based systems and analyze two types of symbol mapping strategies and characterize interferences due to CFO for each scheme. We will also develop some techniques to reduce high PAPR in OFDM based OW systems since the non-linear characteristics of LED transmitters can severely affect system performance. We will look into various precoding based PAPR reduction techniques. We will then analyze performance of various OFDM based OW schemes in multipath diffuse indoor wireless channel. We will compare performance of conventional schemes with a precoded version. We will then describe in detail our newly proposed power and spectrally efficient hybrid asymmetrically clipped optical orthogonal frequency division multiplexing (HACO-OFDM) system and compare its performance with previously proposed schemes. Finally, we will present details of our newly proposed timing synchronization scheme for power efficient asymmetrically clipped (AC) OW OFDM systems. Detailed performance analysis will be presented and a comparison will be developed. Simulation results show that our proposed scheme outperforms all other timing synchronization techniques and exhibits perfect accuracy even at very low signal-to-noise ratio (SNR). Besides performance, our scheme works perfectly for multiple AC OW which proves its high versatility.

Download or read book Performance Evaluation of Orthogonal Frequency Division Multiplixing Systems Over Indoor Multipath Fading Channels written by Mohammed Abdo Saeed and published by . This book was released on 2003 with total page 184 pages. Available in PDF, EPUB and Kindle. Book excerpt: High-data-rate communications are limited not only by noise but often more significantly by the intersymbol interference (ISI) which arises due to the memory of the dispersive multi path fading channels.The aim of this thesis is to investigate the performance of the Orthogonal Frequency Division Multiplexing (OFDM) scheme over wideband multipath fading channels. OFDM is a technique that can be used for transmitting data at extremely high rates by means of splitting up the serial data stream into several parallel streams which are transmitted simultaneously on different subcarriers, each occupying a small fraction of the available bandwidth. By inserting guard interval that is longer than the delay spread of the channel between the OFDM symbols, the ISI can be mitigated or totally eliminated. In this thesis, the theoretical description and modeling of dispersive multipath fading channels is presented. A proposed channel model based on Saleh and Valenzuela model is introduced and implemented by computer simulation. The bit-error-rate (BER) performance of the uncoded OFDM system, in terms of energy per bit-to noise ratio (EBNR), is investigated by simulations for different modulation schemes with both coherent and differential detection. The influence of the number of carriers as well as the guard interval duration on the performance is also investigated. We observed that the EBNR required to achieve a certain BER is significantly increased by 8 - 10 dB for dense multipath fading channels over that required in additive white Gaussian noise (A WGN) channels due to the decrease of the signal power as a result of increasing the number of paths. In addition, differential modulation improves performance in environments where rapid changes in phase are possible. OFDM can be implemented equally well with coherent (non-differential) modulation and demodulation to maximize the signal-to-noise ratio performance of the system. These performance measures are useful for the design and assessment of high speed indoor wireless communication systems.

Download or read book Software Implementation of Orthogonal Frequency Division Multiplexing OFDM Scheme for Mobile Radio Channel written by and published by . This book was released on with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Orthogonal Frequency Division Multiplexing (OFDM) is a transmission technique which ensures efficient utilization of the spectrum by allowing overlap of carriers. OFDM is a combination of modulation and multiplexing that is used in the transmission of information and data. Compared with the other wireless transmission techniques like Frequency Division Multiple Access (FDMA), Code Division Multiple Access (CDMA), OFDM has numerous advantages like high spectral density, its robustness to channel fading, its ability to overcome several radio impairment factors such as effect of AWGN, impulse noise, multipath fading, etc. Due to this it finds wide application in Digital Audio Broadcasting (DAB), Digital Video Broadcasting (DVB), and Wireless LAN. Most of the wireless LAN standards like IEEE 802.11a or IEEE 802.11g use the OFDM as the main multiplexing scheme for better use of spectrum. In fact in the 4G telecommunication system OFDMA is the backbone of it. This project deals with the software simulation of this OFDM system in a mobile radio channel using the software tools of MATLAB® and SIMULINK®. From this simulation the performance of OFDM system in mobile radio channel is studied. Apart from this we also compare the OFDM system performance with the performance of the DS-CDMA system in the mobile radio channel.

Download or read book Multi Carrier Digital Communications written by Ahmad R.S. Bahai and published by Springer Science & Business Media. This book was released on 2006-04-11 with total page 224 pages. Available in PDF, EPUB and Kindle. Book excerpt: Multi-carrier modulation, in particular orthogonal frequency division multiplexing (OFDM), has been successfully applied to a wide variety of digital communications applications for several years. Although OFDM has been chosen as the physical layer standard for a diversity of important systems, the theory, algorithms, and implementation techniques remain subjects of current interest. This book is intended to be a concise summary of the present state of the art of the theory and practice of OFDM technology. This book offers a unified presentation of OFDM theory and high speed and wireless applications. In particular, ADSL, wireless LAN, and digital broadcasting technologies are explained. It is hoped that this book will prove valuable both to developers of such systems, and to researchers and graduate students involved in analysis of digital communications, and will remain a valuable summary of the technology, providing an understanding of new advances as well as the present core technology.

Download or read book Modeling Performance Analysis of QAM based COFDM System written by Xu Zhang and published by . This book was released on 2011 with total page 137 pages. Available in PDF, EPUB and Kindle. Book excerpt: With the rapid increase in the utility of data and voice services, there is a demand for higher data rates and reliability in wireless communications. A wireless communication channel is prone to regrading effects such as shadow fading, multi-path fading, and inters symbol interference (ISI) etc. Orthogonal Frequency Division Multiplexing (OFDM), a candidate for the 4th generation wireless systems, mitigates these effects and supports higher data rates. The performance analysis of a complex system like COFDM, is a challenging task where analytical methods become cumbersome to be used. Simulation based approaches provide a fair estimate of the performance in such cases. In this thesis, the performance of an OFDM system on Additive White Gaussian(AWGN), Rayleigh fading channels and Clarke/Jake's [11] fading Channels have been analyzed with different coding schemes. Reed-Solomon (RS) codes, convolutional codes, TCM codes and LDPC codes have been analyzed in detail. Some of the modern wireless communication channel models have been studied and remodeled, the performances and characteristics have been showed clearly by the simulation result of these models. The effect of inter-carrier interference (ICI) and inter-symbol interference (ISI) on OFDM systems for different channel conditions has been studied and the performances of few techniques to mitigate the degradation due to ISI, ICI have been investigated, such as Cyclic Prefix (CP) or Zero Padding (ZP).

Download or read book Performance Analysis of Orthogonal Frequency Division Multiplexing OFDM written by Hong Giap Ooi and published by . This book was released on 2006 with total page 268 pages. Available in PDF, EPUB and Kindle. Book excerpt: