Download or read book Improvement of Peak to average Power Ratio Reduction in Orthogonal Frequency Division Multiplexing Systems Using Free Side Information Selected Mapping Method written by Sara Razavi and published by . This book was released on 2014 with total page 148 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Selective Mapping technique for PAPR reduction in LTE OFDM Systems written by Neelam Dewangan and published by GRIN Verlag. This book was released on 2012-11-22 with total page 100 pages. Available in PDF, EPUB and Kindle. Book excerpt: Master's Thesis from the year 2012 in the subject Engineering - Communication Technology, grade: none, , course: M.Tech, language: English, abstract: As a promising technique, OFDM has been widely used in emerging broadband communication systems, such as digital audio broadcasting (DAB), high-definition television (HDTV), wireless local area network (IEEE 802.11a and HIPERLAN/2). However, as the OFDM signals are the sum of signals with random amplitude and phase, they are likely to have large PAPR that requires a linear high-power- amplifier (HPA) with an extremely high dynamic range, which is expensive and inefficient. Furthermore, any amplifier nonlinearity causes intermodulation products resulting in unwanted out-of-band power. A number of approaches have been proposed to deal with the PAPR problem, including clipping, clipping-and-filtering (CF), coding, companding transform, active constellation extension (ACE), selected mapping (SLM), partial transmit sequence (PTS), and so on. This thesis proposes an improvement in Selected Mapping technique and Simulation results are compared to existing techniques namely Exponential Companding Transform, Repeated Clipping and Filtering and Adaptive Active Constellation Extension. The improvements which are proposed in classical Selective Mapping technique satisfies the PAPR Reduction criteria with reducing the computational complexity. Also this new scheme has an important advantage of avoiding the extra bits along with the transmitted OFDM signal .This scheme can also be applied to the multiple transmitting antenna cases.

Download or read book Peak to Average Power Ratio Reduction in OFDM Systems written by Anusha Chacko and published by LAP Lambert Academic Publishing. This book was released on 2015-04-17 with total page 60 pages. Available in PDF, EPUB and Kindle. Book excerpt: Orthogonal Frequency Division Multiplexing (OFDM) is a promising technology in wireless communication. High Peak-to-Average Power Ratio (PAPR) is one of the challenging issues of OFDM systems. High PAPR forces the High Power Amplifier (HPA) to operate in its linear region with wide dynamic range, where the power efficiency is very poor. This book gives an overview of different PAPR reduction techniques. And deals in detail with the efficient use of Selected Mapping (SLM) and Partial Transmit Sequence (PTS)technique to reduce high PAPR in OFDM systems.

Download or read book Reducing Peak to Average Power Ratio of OFDM by Using Selected Mapping written by Wanis Mohamed and published by . This book was released on 2012 with total page 53 pages. Available in PDF, EPUB and Kindle. Book excerpt: Orthogonal frequency division multiplexing (OFDM) has become the most popular modulation technique for high speed data transmission. However, high peak to average power ratio (PAPR) is a major drawback of this modulation technique, because high peak reduces the power efficiency of the RF power amplifier at transmitter. This project gives an overview of the popular OFDM reduction techniques, and indicates that selected mapping (SLM) is a promising reduction technique.

Download or read book Peak to average Power Ratio Reduction in Orthogonal Frequency Division Multiplexing written by Sidharth Khanna and published by . This book was released on 2007 with total page 154 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Peak to Average Power Ration Reduction and Bit Error Rate Improvement in Wireless Orthogonal Frequency Division Multiplexing Communication Systems written by Wisam Fahmi Al-Azzo and published by . This book was released on 2009 with total page 390 pages. Available in PDF, EPUB and Kindle. Book excerpt: Orthogonal frequency division multiplexing (OFDM) offers high data rate transmission with high spectral efficiency, immunity to multipath fading, and simple implementation using fast Fourier transform (FFT). OFDM is readily implemented by present day processors in many high speed networks. However, one of the major drawbacks of OFDM systems is the high peak-to-average power ratio (PAPR); this can result in poor power efficiency, degradation in bit-error-rate (BER) performance, and spectral spreading. The effective PAPR reduction of OFDM signals by simple processing has been challenge for the limited power and processing capability of portable OFDM applications. This thesis investigates the problem of high PAPR in OFDM systems and presents many simple implementation PAPR reduction techniques, and one error-resilient technique. The first part of this thesis presents two time-domain PAPR reduction techniques, viz, square-rooting the envelope of the OFDM output signals, and the smoothing technique. The square-rooting process changes the statistical distribution of the OFDM output signals from Rayleigh to Gaussian-like distribution and reduces the differences between the value of peak and average power, which consequently reduces the PAPR significantly. About 6 dB reduction in PAPR is achieved with moderate degradation in BER performance. For the smoothing process, which is derived from the image enhancement technique, the smoothing applied on the OFDM signals mitigates the PAPR due to its averaging effect. Up to 2.5 dB reduction is achieved by smoothing. Two new probabilistic based non-iterative frequency-domain PAPR reduction techniques are introduced in the second part of the thesis. These techniques reduce PAPR by changing the statistical distribution of the OFDM modulated symbols from uniform distribution to Gaussian-like distribution. This task is performed by two different methods in two different PAPR techniques. The first method of PAPR reduction is done by the addition of complex Gaussian random signals, while the second one is done by insertion of dummy Gaussian subcarriers. The two techniques provide PAPR reduction in the order of 5 dB for PSK-OFDM systems with no out-of-band radiation. The adaptive operation of these techniques enhances significantly both the BER performance and reduce the transmission power. The last part of this thesis presents a new modulation-based error resilient technique referred to as multi-dimensional modulation technique (MDM). In this technique concatenation of digital modulators of decreasing modulation orders are employed. The MDM technique improves the BER performance linearly with increased size of modulation order; up to 12 dB improvement in Eb/No is achieved relative to the conventional OFDM systems at high modulation orders, M≥1024. Also, the MDM technique offers both error resilience and PAPR reduction when it is combined with the conventional OFDM systems in time domain. As a conclusion, the proposed techniques described above offer new solutions to the problem of high PAPR in OFDM systems, and for one of them offer improvement of BER performance at the same time. Besides, they can be applied for different systems parameters and applications requirement. Moreover, the PAPR reduction techniques proposed in this thesis are data-independent and can be implemented in one-shot; while the MDM technique uses only digital modulation and dc-offset signal processing, which can be implemented by simple circuits and/or processors.

Download or read book An Investigation of Peak To Average Power Reduction written by Yi Wang and published by LAP Lambert Academic Publishing. This book was released on 2010-06 with total page 76 pages. Available in PDF, EPUB and Kindle. Book excerpt: Multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) technology is one of the most attractive candidates for fourth generation(4G)mobile radio communication. It effectively combats the multipath fading channel and improves the bandwidth efficiency. At the same time, it also increases system capacity so as to provide a reliable transmission. However, the main drawback of MIMO-OFDM system is high peak-to-average power ratio (PAPR) for large number of sub-carriers, which result in many restrictions for practical applications. Coding, phase rotation and clipping are among many PAPR reduction schemes that have been proposed to overcome this problem. In this thesis, we will mainly investigate the PAPR reduction performance with two different PAPR reduction methods: partial transmit sequence (PTS) and selective mapping(SLM). These two methods are sub- entities of phase rotation scheme. In addition, several corresponding modified algorithms are studied with respect to balanced performance and applicability.

Download or read book New Peak to average Power Ratio Reduction Schemes for OFDM Systems written by Peng Liu and published by . This book was released on 2004 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: It is known that the orthogonal frequency division multiplexing (OFDM) modulation is very suitable for high-speed wireless transmission systems due to its bandwidth efficiency and ability in coping with multipath fading. However, the large peak-to-average power ratio (PAPR) of an OFDM signal limits the application of OFDM to a certain degree. The research focus of this thesis is on the study of some new PAPR reduction schemes for OFDM systems. In the first part of the thesis, we investigate the peak windowing method, the clipping method, and a combination of the two techniques with an emphasis on the performance assessment of the transmitted OFDM signal using the combination scheme. We start with the review of the two typical signal distortion techniques and point out their advantages and shortcomings. We then propose a combination scheme for the two techniques in order to overcome their drawbacks. In the proposed combination scheme, a weighting function is used to remove instantaneous signal peaks and then a hard-limiting is utilized for the reduction of the overall peak powers. A modified IDFT interpolation is developed and employed in the combination scheme to improve the interpolation precision of the time-domain OFDM signal. (Abstract shortened by UMI.).

Download or read book Minimizing Peak to average Power Ratio in an Orthogonal Frequency Division Multiplex System written by and published by . This book was released on 2014 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Orthogonal frequency division multiplexing (OFDM) is a popular standard in wireless communication for its enabling high throughput data transfer. However, the OFDM signal usually has a high peak-to-average power ratio (PAPR), which requires a wide-dynamic-range, powerconsuming amplifier. Whenever the signal peak is greater than the amplifier linear region, the signal is distorted. This distortion generates interference in both in-band and out-of-band spectrum. The effect of in-band interference becomes apparent at medium to high SNR levels and reduces system performance gains as the SNR increases. We endeavor to improve the system BER by minimizing the signal peak using signal scrambling techniques. These techniques effectively reduce the signal peak and enhance system performance when the receiver is able to correctly decode the scrambling information. This information is a weakness of existing techniques because a resource is needed to transport it, and its corruption dramatically undermines system performance. We propose a novel scheme that utilizes resources allotted for channel estimation and does not need to transmit explicit scrambling information. Therefore, our technique improves over the existing ones in the same category. In addition, we propose some procedures to alleviate scrambling information corruption and show discernible advancements. We study the trade-off between PAPR reduction and channel estimation when they have to compete for the same resource. We suggest doing PAPR reduction only when the receiver can obtain a good channel estimate to ensure favorable system performance.

Download or read book Peak to Average Power Ratio Reduction Using the Clipping Technique in Orthogonal Frequency Division Multiplexing System written by Wan Hafiza Wan Hassan and published by . This book was released on 2006 with total page 278 pages. Available in PDF, EPUB and Kindle. Book excerpt: The demand for high-speed mobile wireless communications is rapidly growing. The orthogonal frequency division multiplexing (OFDM) technology promises to be a key technique for achieving the high data capacity and spectral efficiency requirements for wireless communication systems of the near future. With its natural resistance to multipath fading and its capability to support extremely high data rates, OFDM is a major candidate for a fourth generation system. Despite many advantages of OFDM, it has two major drawbacks which are high peak to average power ratio (PAPR) and sychronization problem. A high PAPR causes saturation in power amplifiers, leading to intermodulation products among the sub carriers and disturbing out of band energy. Therefore, it is desirable to reduce the PAPR by means of PAPR reduction schemes. Clipping has been identified as the simplest yet effective technique of PAPR reduction. However, we have found out that clipping has resulted in the degradation of BER and enhanced the growth of out of band radiation leading to the degradation of the OFDM overall performance. As a solution, we have proposed an enhanced OFDM system with the objectives of reducing the high PAPR values while minimizing the effects of clipping. The convolutional coding scheme incorporated into the proposed system as a forward error control (FEC) scheme to improve the performance of BER in OFDM system. Besides, oversamples IFFT and digital filtering techniques are introduced into the system to minize the out of band radiation (OOBR). In this thesis, we have shown that the proposed system has significantly enhanced the BER performance and minimized the OOBR. However, there are a few trade-off which affected the overall performance. Hence, we have identified the optimum designed parameters which have resulted in a maximum PAPR reduction and OOBR suppression capability of 9 dB and 52 dB respectively at the cut-off BER of 10-4. In comparison to the existing proposed systems, our proposed system can be considered as one of the optimum system as it offers good PAPR reduction as well as OOBR suppression and comparable BER performance at the lowest value of SNR.

Download or read book New Signal Processing Approaches to Peak to average Power Ratio Reduction in Multicarrier Systems written by Ki-taek Bae and published by . This book was released on 2010 with total page 294 pages. Available in PDF, EPUB and Kindle. Book excerpt: Multi-carrier systems based on orthogonal frequency division multiplexing (OFDM) are efficient technologies for the implementation of broadband wireless communication systems. OFDM is widely used and has been adopted for current mobile broadband wireless communication systems such as IEEE 802.a/g wireless LANs, WiMAX, 3GPP LTE, and DVB-T/H digital video broadcasting systems. Despite their many advantages, however, OFDM-based systems suffer from potentially high peak-to-average power ratio (PAR). Since communication systems typically include nonlinear devices such as RF power amplifiers (PA) and digital-to-analog converters (DAC), high PAR results in increased symbol error rates and spectral radiation. To mitigate these nonlinear effects and to avoid nonlinear saturation effects of the PA, the operating point of a signal with high peak power must be backed off into the linear region of the PA. This so-called output backoff (OBO) results in a reduced power conversion efficiency which limits the battery life for mobile applications, reduces the coverage range, and increases both the cost of the PA and power consumption in the cellular base station. With the increasing demand for high energy efficiency, low power consumption, and greenhouse gas emission reduction, PAR reduction is a key technique in the design of practical OFDM systems. Motivated by the PAR reduction problem associated with multi-carrier systems, such as OFDM, this research explores the state of the art of PAR reduction techniques and develops new signal processing techniques that can achieve a minimum PAR for given system parameters and that are compatible with the appropriate standards. The following are the three principal contributions of this dissertation research. First, we present and derive the semi-analytical results for the output of asymptotic iterative clipping and filtering. This work provides expressions and analytical techniques for estimating the attenuation factor, error vector magnitude, and bit-error-rate (BER), using a noise enhancement factor that is obtained by simulation. With these semi-analytical results, we obtain a relationship between the BER and the target clipping level for asymptotic iterative clipping and filtering. These results serve as a performance benchmark for designing PAR reduction techniques using iterative clipping and filtering in OFDM systems. Second, we analyze the impact of the selected mapping (SLM) technique on BER performance of OFDM systems in an additive white Gaussian noise channel in the presence of nonlinearity. We first derive a closed-form expression for the envelope power distribution in an OFDM system with SLM. Then, using this derived envelope power distribution, we investigate the BER performance and the total degradation (TD) of OFDM systems with SLM under the existence of nonlinearity. As a result, we obtain the TD-minimizing peak backoff (PBO) and clipping ratio as functions of the number of candidate signals in SLM. Third, we propose an adaptive clipping control algorithm and pilot-aided algorithm to address a fundamental issue associated with two low-complexity PAR reduction techniques, namely, tone reservation (TR) and active constellation extension (ACE). Specifically, we discovered that the existing low-complexity algorithms have a low clipping ratio problem in that they can not achieve the minimum PAR when the target clipping level is set below the initially unknown optimum value. Using our proposed algorithms, we overcome this problem and demonstrate that additional PAR reduction is obtained for any low value of the initial target clipping ratio.

Download or read book A New Scheme for Reduction of Peak to average Power Ratio in Orthogonal Frequency Division Multiplexing written by Ahmed Mustafa H. Melad and published by . This book was released on 2003 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Orthogonal Frequency Division Multiplexing (OFDM) is an attractive modulation method ror channels with a non-flat frequency response. as it saves the need for complex equalizers. However. its main disadvantage is the high peak-to-average power ratio (PAPR) of the output signal, which may take values within a range that is proportional to the number of carriers in the system. As a result, a linear behavior of the system over a large dynamic range is needed and therefore the efficiency of the output amplifier is reduced. Many methods have been proposed to reduce the PAPR of the OFDM signal. among them a clipping technique which has been focused and investigated. OFDM signal, among them a clipping technique which has been focused and investigated. This thesis proposes a new scheme to reduce the PAPR. We name it Off technique. Further the effects of clipping scheme as well as the new scheme on the OFDM system performance in terms of Bit Error Rate (BER) and PAPR reduction is investigated. The results obtained indicate that both parameters, i.e. the reduction in PAPR and BER of this scheme were worse than those of the Clipping Scheme. In conclusion, results indicate that Off Technique does not offer a better solution to P APR reduction in the OFDM system.

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 Bit Loading and Peak Average Power Reduction Techniques for Adaptive Orthogonal Frequency Division Multiplexing Systems written by and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In a frequency-selective channel a large number of resolvable multipaths are present which lead to the fading of the signal. Orthogonal frequency division multiplexing (OFDM) is well-known to be effective against multipath distortion. It is a multicarrier communication scheme, in which the bandwidth of the channel is divided into subcarriers and data symbols are modulated and transmitted on each subcarrier simultaneously. By inserting guard time that is longer than the delay spread of the channel, an OFDM system is able to mitigate intersymbol interference (ISI). Significant improvement in performance is achieved by adaptively loading the bits on the subcarriers based on the channel state information from the receiver. Imperfect channel state information (CSI) arises from noise at the receiver and also due to the time delay in providing the information to the transmitter for the next data transmission. This thesis presents an investigation into the different adaptive techniques for loading the data bits on the subcarriers. The choice of the loading technique is application specific. The spectral efficiency and the bit error rate (BER) performance of adaptive OFDM as well as the implementation complexity of the different loading algorithms is studied by varying any one of the parameters, data rate or BER or total transmit power subject to the constraints on the other two. A novel bit loading algorithm based on comparing the SNR with the threshold in order to minimize the BER is proposed and its performance for different data rates is plotted. Finally, this thesis presents a method for reducing the large peak to average power ratio (PAPR) problem with OFDM which arises when the sinusoidal signals of the subcarriers add constructively. The clipping and the probabilistic approaches were studied. The probabilistic technique shows comparatively better BER performance as well as reduced PAPR ratio but is more complex to implement.

Download or read book Intelligent Manufacturing and Mechatronics written by Roshaliza Hamidon and published by Springer Nature. This book was released on with total page 864 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book A Simple and Effective Peak to average Power Ratio Reduction Approach Based on Iterative Companding Transform and Filtering Framework of Orthogonal Frequency Division Multiplexing Signal written by Thenappan T. Thiagarajan and published by . This book was released on 2017 with total page 38 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: The peak-to-average power ratio (PAPR) reduction in OFDM is an unresolved issue. Intense research has been carried out to solve the issue of peak power and to reduce the impact on overall system performance. PAPR can negatively affect system performance by inducing spectral regrowth and degrading detection efficiency. The purpose of this study is to show how the iterative companding transform and filtering (ICTF) framework can solve the PAPR issue in a redefined way. ICTF is able to obtain low out-of-band interference (OBI) and improved bit error rate (BER) while reducing PAPR significantly. Simulation results show good performance, low complexity, and reliable efficiency over traditional state of methods such as the iterative clipping and filtering technique.

Download or read book Peak to Average Power Ratio PAPR Reduction in Orthogonal Frequency Division Multiplexing OFDM Communication Systems written by Xuefu Zhou and published by . This book was released on 2002 with total page 154 pages. Available in PDF, EPUB and Kindle. Book excerpt: