PAPR

High PAPR is one of the major drawbacks of OFDM systems. It drives the transmitter's power amplifier into its nonlinear region, thus causing nonlinear distortions. Square rooting technique (SQRT) and µ-law companding technique are the simple techniques to reduce PAPR in OFDM systems. In this paper, we derive analytical CCDF for both the techniques. The comparisons of SQRT and µ-law companding techniques are carried out using theoretical and simulation results. It is verified that the µ-law companding technique is better than SQRT technique for PAPR reduction.

An OFDM system is combined with multiple-input multiple-output (MIMO)  in order to increase the diversity gain and system capacity over the time variant frequency-selective channels.  However, a major drawback of MIMO-OFDM system is that the transmitted signals on different antennas might exhibit high peak-to-average power ratio (PAPR).In this paper, we present a PAPR analysis reduction of space-time-block-coded (STBC) MIMO-OFDM system for 4G wireless networks. Several techniques have been used to reduce the PAPR of the (STBC) MIMOOFDM system: clipping and filtering, partial transmit sequence (PTS) and selected mapping (SLM). Simulation results show that clipping and filtering provides a better PAPR reduction than the others methods and only SLM technique conserve the PAPR reduction in reception part of signal.

3GPP LTE has utilized the OFDMA for the downlink which oversees assortment versatility, inborn impenetrability to Inter picture Interference (ISI) and several more unmistakable. At any rate, 3GPP LTE structures delight in the unwell impacts of a really standard trouble called height to normal power share. The general paper attempted to discuss the section and secluding fundamentally basically based approaches for unmarried individual OFDMA structures. We have attempted our generations for L=1-4 oversampling cost and 256 FFT system and 128 sporadic substances bits to diminish the PAPR with the guide of dismissing at the correlative blend scattering work. It's far found inside the reproduction that top to regular power share diminishes to the tune of 8db from the unique unmodified machine.

The high peak-to-average (PAPR) is one of the serious problems in the application of OFDM technology. The Companding transform approach is a very attractive technique to reduce PAPR in that high bit error rate will occurred.in this paper we can combined both companding and dct(discrete cosine transforms) the proposed scheme may obtain about 1 dB PAPR reduction compared with the conventional Companding algorithm.

Multiple inputs multiple output orthogonal frequency division multiplexing (MIMO-OFDM) is an attractive transmission technique for high bit-rate communication systems. MIMO-OFDM has become a promising candidate for high performance 4G broadband wireless communications. One main disadvantage of OFDM is the high peak-to-average power ratio (PAPR) of the transmitter's output signal. Selected-Mapping (SLM) scheme which does not require the transmission of side information and can reduce the peak to average power ratio (PAPR) in turbo coded orthogonal frequency division multiplexing (OFDM) system is proposed. Simulation results show that the system can achieve significant reduction in PAPR and satisfactory bit error rate performance over AWGN channels. KEYWORDS Orthogonal Frequency Division Multiplexing (OFDM), peak-to-average-power-ratio (PAPR), Selective Mapping (SLM), Complementary Cummulative Distribution Function (CCDF), Bit Error Rate (BER).

The Orthogonal Frequency Division Multiplexing is one of the modulation techniques widely used in the broadband wireless technology. One of the main problems of this technology is the high peak-to-average power ratio of transmission signal due to the superposition of many subcarriers. This paper presents a new hybrid peak-toaverage power ratio reduction technique, which combines a selective mapping method with the clipping method. The paper presents the performance and advantages of the new technique and compares it with other existing methods.

MIMO-OFDM system in Rayleigh Fading Channel is very popular technique for mobile communication now a day's for research. Here we want increase the capacity of MIMO-OFDM of system by using adaptive modulation, Algebraic Space-Time Codes (ASTC) encoder for MIMO Systems are based on quaternion algebras .we found that ergodic capacity has some limitation which reduce the system's performance to overcome this we use ASTC code . ASTC code are full rank, full rate and non vanishing constant minimum determinant for increasing spectral efficiency and reducing Peak to Average Power Ratio (PAPR) .

The high PAPR is an OFDM system is arises because of IFFT operation, where data symbol across subcarrier can add up to produce a high peak value signal. In OFDM system, the peak deviation about average is significantly high, hence the signal level moves outside the dynamic range. Because in OFDM system we are loading the symbol in subcarrier and then take IFFT of this signal. This arises high PAPR, which limits use of OFDM in latest technological advancement such as 4G and 5G.This paper presents an idea to reduce PAPR in OFDM system using selected mapping (SLM) technique. When we want to convert a finite sequence of data points in terms of a sum of cosine functions oscillating at different frequencies we need to apply Discrete Cosine Transform(DCT), and it is easiest way to do so.

MC CDMA is a rising candidate for future generation broadband wireless communication and gained great attention from researchers. It provides benefits of both OFDM and CDMA. Main challenging problem of MC CDMA is high PAPR. It occurs in HPA and reduces system efficiency. There are many PAPR reduction techniques for MC CDMA. In this paper we proposed Ant colony optimization algorithm to reduce PAPR with different number of user using BPSK and QPSK modulation. ACO is a metaheuristic technique and based on the foraging behavior of real ants. It provides solution to many complex problems. Simulation result proves that ACO using BPSK modulation is effective for reducing PAPR in MC CDMA.

Orthogonal frequency division multiplexing (OFDM) is a peculiar case of multicarrier transmission technique for high speed data transmission over multipath fading channels. The high Peak to Average Power Ratio (PAPR) is one of the most detrimental aspects in the OFDM system, as it degrades the efficiency of the power amplifier in the transmitter. Discrete Cosine Transform-II (DCT-II) is a less complex and distortion less method used to mitigate the PAPR. In this paper, a combination of Discrete Cosine Transform-II and Partial Transmit Sequence (PTS) is used to reduce the PAPR of the transmitted OFDM signal and results are compared with DCT-II and normal OFDM signal. Simulation results show that the combination of DCT-II and PTS shows better PAPR reduction.

Orthogonal Frequency Division Multiplexing along with the multiple accesses is the modulation technique used in the fourth generation wireless communication. With the fast growing technology and the huge demand for the increase in the bandwidth has made OFDM as the best modulation technique for high speed transmission. The spectrum of the bandwidth is effectively utilized in an OFDM. This provides higher efficiency and improves the overall performance of the system. Though OFDM has all these advantages there are certain drawbacks which need to be addressed. The major ones include Inter carrier Interference and the ratio of the peak to the average power. The research idea was to consider the drawback and try to overcome it. Hence ratio of the peak to the average power was considered. The methodology is to generate the OFDM symbols with Offset QPSK as the modulation technique and analyze the peak power and peak to average power ratio of the generated symbols and apply the proposed method to reduce it. The lossy coding method falls under the category of the signal distortion. The simulation is performed in MATLAB. The simulation results of the proposed method and the amount of the reduction achieved in ratio of the peak to average power along with the amount of the bit error rate have been discussed in the paper.

The problem of peak-to-average power ratio (PAPR) reduction in orthogonal frequency-division multiplexing (OFDM) based massive multiple-input multiple-output (MIMO) downlink systems is considered. OFDM consist of large number of independent subcarriers, as a result of which the amplitude of such a signal can have high peak values. The peak to average power ratio of a transmitted signal is one of main challenges in OFDM or MIMO-OFDM. Understanding the effects of PAPR on OFDM and MIMO-OFDM systems is critical when determining what techniques to use improve system performance. Selective-Mapping (SLM) scheme which does not require the transmission of side information and can reduce the PAPR in OFDM system is proposed. SLM is a distortion less technique that can reduce PAPR efficiently without increase in power requirement and incurring data rate loss. Simulation results show that the system can achieve significant reduction in PAPR and satisfactory bit error rate performance over AWGN channels.

In this paper, a survey on different modulation schemes having lowest peak to average power ratio (PAPR) value for use in uplink communication has been studied. OFDM has become the popular modulation choice for high data rate wireless communication systems. It can provide multi-path delay spread tolerance and is robust to channel dispersions. But one of the major limitations of OFDM is the large variation in signal amplitude which gives it a high PAPR. OFDM signals with high PAPR will suffer from nonlinear distortion due to non-ideal behavior of High Power amplifiers as well as it is detrimental to battery powered devices like mobile phones which are power limited .SC-FDMA was found to have a better PAPR reduction than OFDMA and has become modulation choice for uplink communication in Long Term Evolution (LTE). Available @ http://www.ijret.org 58

In this paper, a survey on different modulation schemes having lowest peak to average power ratio (PAPR) value for use in uplink communication has been studied. OFDM has become the popular modulation choice for high data rate wireless communication systems. It can provide multi-path delay spread tolerance and is robust to channel dispersions. But one of the major limitations of OFDM is the large variation in signal amplitude which gives it a high PAPR. OFDM signals with high PAPR will suffer from nonlinear distortion due to non-ideal behavior of High Power amplifiers as well as it is detrimental to battery powered devices like mobile phones which are power limited .SC-FDMA was found to have a better PAPR reduction than OFDMA and has become modulation choice for uplink communication in Long Term Evolution (LTE).

Orthogonal Frequency Division Multiplexing (OFDM) is a special form of multicarrier modulation scheme, which divides the entire frequency selective fading channel into many orthogonal narrow band flat fading sub channels. Orthogonal Frequency Division Multiplexing (OFDM) is considered to be a promising technique against the multipath fading channel for wireless communications [1]. However, OFDM faces the Peak-to-Average Power Ratio (PAPR) problem that is a major drawback of multicarrier transmission system. We will be using Selected Mapping method (SLM) to reduce PAPR, improve BER while maintain high SNR. MATLAB® simulation is used to implement the proposed model.

High Peak-to-Average Power Ratio (PAPR) is one of the major drawback of Orthogonal Frequency Division Multiplexing (OFDM) based systems that can cause intermodulation among the subcarriers due to the nonlinearities of the fiber. The high PAPR increases the complexity of the Analog to Digital (A/D) and Digital to Analog (D/A) converters. In this paper, I present an analysis of Discrete Fourier Transform (DFT) precoded OFDM system for different FFT sizes (where FFT = 128, 256, 512). I compare the simulation results of DFT-precoded OFDM system with conventional OFDM system. Simulation results show that the PAPR of DFT-precoded OFDM system is lower than conventional OFDM system KEYWORDS: PAPR, OFDM, DFT precoder, Nonlinear effect.

The Long Term Evolution (LTE) standard requires an uplink transmission rate of up to 86 Mbps. In order to support such a high data rate and avoid the high Peak-to-Average Power Ratio (PAPR) disadvantage in Orthogonal-FDMA, Single Carrier Frequency Division Multiple Access(SC-FDMA) is used in the uplink communication in LTE cellular systems. In this paper an overview of LTE and the LTE uplink transmissions is given, especially the SC-FDMA technique. Additionally results from a PAPR analysis, comparing OFDMA and SC-FDMA using different subcarrier mapping schemes, are presented. Finally an adaptive hybrid subcarrier mapping scheme, a combination of localized and distributed mapping schemes, is proposed as a technique for reaching good transmission performance with low PAPR.

In this paper, a survey on different modulation schemes having lowest peak to average power ratio (PAPR) value for use in uplink communication has been studied. OFDM has become the popular modulation choice for high data rate wireless communication systems. It can provide multi-path delay spread tolerance and is robust to channel dispersions. But one of the major limitations of OFDM is the large variation in signal amplitude which gives it a high PAPR. OFDM signals with high PAPR will suffer from nonlinear distortion due to non-ideal behavior of High Power amplifiers as well as it is detrimental to battery powered devices like mobile phones which are power limited .SC-FDMA was found to have a better PAPR reduction than OFDMA and has become modulation choice for uplink communication in Long Term Evolution (LTE). Available @ http://www.ijret.org 58

3GPP LTE has utilized the OFDMA for the downlink which provides spectrum flexibility, inherent resistance to Inter symbol Interference (ISI) and many more. However 3GPP LTE systems suffer from a very common problem known as Peak to Average Power ratio. The present paper tried to discuss the clipping and filtering based techniques for single user OFDMA systems. We have tried our simulations for L=1-4 oversampling rate and 256 FFT matrix and 128 random data bits to decrease the PAPR by overlooking on the complementary cumulative distribution function. It is observed in the simulation that Peak to Average Power ratio reduces to the tune of 8db from the original unmodified system.

In this paper, a survey on different modulation schemes having lowest peak to average power ratio (PAPR) value for use in uplink communication has been studied. OFDM has become the popular modulation choice for high data rate wireless communication systems. It can provide multi-path delay spread tolerance and is robust to channel dispersions. But one of the major limitations of OFDM is the large variation in signal amplitude which gives it a high PAPR. OFDM signals with high PAPR will suffer from nonlinear distortion due to non-ideal behavior of High Power amplifiers as well as it is detrimental to battery powered devices like mobile phones which are power limited .SC-FDMA was found to have a better PAPR reduction than OFDMA and has become modulation choice for uplink communication in Long Term Evolution (LTE).

The purpose of this article is to propose a new configuration based on OCDMA and Fast-OFDM techniques for access network applications. A hybrid intensity modulation with direct detection, fast orthogonal frequency-division multiplexing-code division multiplexing access (IM/DD Fast-OFDM-CDMA) system is analytically and numerically evaluated for an amplifier-free access network. Therefore, system performance is analytically investigated in terms of bit error rate/Q-factor as a function of simultaneous users, fiber length and launched optical power. Firstly, the proposed analytical model includes the overlapping effect among OFDM subcarriers, the peak-to-average power ratio (PAPR), and multiple access interference (MAI). Secondly, a simulation setup is performed, allowing four simultaneous users operating at 40 Gb/s in a passive optical network (PON) context. Furthermore, a power budget analysis is made between IM/DD Fast-OFDM-CDMA, all-optical IM/DD OFDM-CDMA (IM/DD AO-OFDM-CDMA) and OCDMA wavelength division multiplexing (OCDMA-WDM) configurations. It is shown that at 40 Gb/s and by using 2D-hybrid coding (2D-HC), the maximum achievable transmission-reach of IM/DD Fast-OFDM-CDMA is 142 km, which is 34 km and 60 km higher than those provided by the IM/DD AO-OFDM-OCDMA and OCDMA-WDM PON configurations, respectively.

Abstract: Orthogonal frequency division multiplexing is an attractive technique for modern wireless communication and has recently been focused in high-data-rate wireless communication research. However, high peak-to-average power ratio (PAPR) of the ...

Orthogonal Frequency Division Multiplexing (OFDM) is one well-known scheme, which has recently become a preferred choice for parallel-data-transmission which reduces the influence of multipath fading and avoids the use of complex equalizers. However, an OFDM signal has a large peak-to-average power ratio (PAPR), which can result in significant distortion when transmitted through a nonlinear device, such as a transmitter power amplifier (PA). This paper describes and makes some remark on the selection criteria for selecting the PAPR reduction techniques that are based on signal distortion, probabilistic (scrambling) and coding. Comparison indicates that coding technique is best for PAPR reduction but suffers from bandwidth efficiency as the code rate is reduced. We have also developed Recursive Golay Complementary Codes (RGCC) with low PAPR, high code rate and high information rate.

Orthogonal Frequency Division Multiplexing along with the multiple accesses is the modulation technique used in the fourth generation wireless communication. With the fast growing technology and the huge demand for the increase in the bandwidth has made OFDM as the best modulation technique for high speed transmission. The spectrum of the bandwidth is effectively utilized in an OFDM. This provides higher efficiency and improves the overall performance of the system. Though OFDM has all these advantages there are certain drawbacks which need to be addressed. The major ones include Inter carrier Interference and the ratio of the peak to the average power. The research idea was to consider the drawback and try to overcome it. Hence ratio of the peak to the average power was considered. The methodology is to generate the OFDM symbols with Offset QPSK as the modulation technique and analyze the peak power and peak to average power ratio of the generated symbols and apply the proposed method to reduce it. The lossy coding method falls under the category of the signal distortion. The simulation is performed in MATLAB. The simulation results of the proposed method and the amount of the reduction achieved in ratio of the peak to average power along with the amount of the bit error rate have been discussed in the paper.

This paper proposes an effective iterative clipping (IC) on a coded carrier interferometry OFDM (CI/OFDM) system for improving the system performances over the nonlinearity of a solid state power amplifier (SSPA). An additional filtering is not required to remove the out-of-band (OOB) spectrum radiation as required in the conventional clipping method. The IC is designed with a minimized computational complexity though the iteration is performed. The results confirm that the CI/OFDM with the proposed IC presents many advantages in terms of BER performance and OOB spectrum radiation. Based on the optimization on BER and OOB spectrum, it is found that 2 and 3 iterations is an effective number for the IC in OFDM and CI/OFDM systems, respectively. The total degradation (TD) improvement by the effective IC in CI/OFDM is about 0.32dB for QPSK and 2.1dB for 64QAM symbol on an SSPA with an output-back-off (OBO) 4dB and 8dB, respectively.

In this modern era, Orthogonal Frequency Division Multiplexing (OFDM) has been proved to be an explicit promising technique for wired and wireless systems because of its several advantages like high spectral efficiency, robustness against frequency selective fading, relatively simple receiver implementation etc. Besides having a number of advantages OFDM suffers from few disadvantages like high Peak to Average Power Ratio (PAPR), Intercarrier Interference (ICI), Intersymbol Interference (ISI) etc. These detrimental effects, if not compensated properly and timely, can result in system performance degradation. This paper mainly concentrates on reduction of PAPR.A comparisons have been made between various precoding techniques against conventional OFDM.

A new work based-wavelet transform is designed to overcome one of the main drawbacks that found in the present new technologies. Orthogonal Frequency Division Multiplexing (OFDM)is proposed in the
literature to enhance the multimedia resolution. However, the high peak power (PAPR) values will obstruct such achievements. Therefore, a new proposition is found in this work, making use of the wavelet
transforms methods, and it is divided into three main stages; de-noising stage, thresholding stage and then the replacement stage.
In order to check the system stages validity; a mathematical model has been built and its checked after using a MATLAB simulation. A simulated bit error rate (BER) achievement will be compared with our
previously published work, where an enhancement from 8×10-1 to be 5×10-1 is achieved. Moreover, these results will be compared to the work found in the literature, where we have accomplished around 27%
PAPR extra reduction. As a result, the BER performance has been improved for the same bandwidth occupancy. Moreover and
due to the de-noise stage, the verification rate has been improved to reach 81%. This is in addition to the noise immunity enhancement.

WiMAX is a highly sophisticated technology in the broadband wireless access communication system. Scalable Orthogonal Frequency Division Multiple Access (OFDMA) is a key technology behind mobile WiMAX and it is also expected to play a key role in 3GPP Long Term Evolution (LTE) standards. Designers and OEMs have to concentrate on flexibility, scalability and stability of the overall Orthogonal Frequency Division Multiplexing (OFDM) system along with its proper data processing and channeling process to achieve high performance and competitiveness. In this paper, the performance of a strictly band limited OFDM signal is examined using deliberate clipping method, one of the simplest signal distortion based way to reduce high Peak to Average Power Ratio (PAPR) and its effect on the resultant Bit Error Rate (BER) against Signal to Noise Ratio (SNR) performance. A simulation program using MATLAB software was developed to investigate performance of OFDM signal by optimization of different parameters such values of FFT size, Cyclic Prefix co-efficient (CPC) and The Voltage Clipping Ratio (VCR). The simulation results show that with the increment of VCR at optimized parameter values of FFT size and CP, the performance of BER vs SNR improves compared to the results found without clipping.

This paper proposes an effective iterative clipping (IC) on a coded carrier interferometry OFDM (CI/OFDM) system for improving the system performances over the nonlinearity of a solid state power amplifier (SSPA). An additional filtering is not required to remove the out-of-band (OOB) spectrum radiation as required in the conventional clipping method. The IC is designed with a minimized computational complexity though the iteration is performed. The results confirm that the CI/OFDM with the proposed IC presents many advantages in terms of BER performance and OOB spectrum radiation. Based on the optimization on BER and OOB spectrum, it is found that 2 and 3 iterations is an effective number for the IC in OFDM and CI/OFDM systems, respectively. The total degradation (TD) improvement by the effective IC in CI/OFDM is about 0.32dB for QPSK and 2.1dB for 64QAM symbol on an SSPA with an output-back-off (OBO) 4dB and 8dB, respectively.

In this paper, a new large spreading code set with a uniform low cross-correlation is proposed. The proposed code set is capable of (1) increasing the number of assigned user (capacity) in a multicarrier code division multiple access (MC-CDMA) system and (2) reducing the peak-to-average power ratio (PAPR) of an orthogonal frequency division multiplexing (OFDM) system. In this paper, we derive a new code set and present an example to demonstrate performance improvements of OFDM and MC-CDMA systems. Our proposed code set with code length of N has K = 2N + 1 number of codes for supporting up to (2N + 1) users and exhibits lower cross correlation properties compared to the existing spreading code sets. Our results with subcarrier N = 16 confirm that the proposed code set outperforms the current pseudo-orthogonal carrier interferometry (POCI) code set with gain of 5 dB at bit-error-rate (BER) level of 10 −4 in the additive white Gaussian noise (AWGN) channel and gain of more than 3.6 dB in a multipath fading channel.

Non orthogonal multiple access (NOMA) is one of the fundamental aspects of consideration for the upcoming fifth generation of cellular technology. The working principle of NOMA is based on sharing of the resource block with multiple users so as to have a better spectrum utility. This is different from the previous versions of multiple access techniques used where one resource block was allotted to only one user. Several studies have been made to combine NOMA with OFDM system so that the technical maturity of OFDM system can be used to improve the system performance, called as OFDM-NOMA systems. However, this also introduces a high Peak to Average Power Ratio (PAPR) in the system. This needs to be tackled as a high PAPR decreases the power efficiency of the system. This paper takes in consideration the reduction of PAPR by using a hybrid PAPR reduction using Hartley Transform precoding and Clipping and Filtering technique.

Orthogonal frequency division multiplexing (OFDM) is a multicarrier communication technique and it has capability to rise above the frequency-selective fading problem, which is common in wireless broadband communications. This has made it popular since last few years. The OFDM system suffers from a number of drawbacks such as the high peak-toaverage power ratio (PAPR). Many PAPR reduction techniques used either destroy the system performance, which is the clipping technique or increases the overall complexity of the system, such as the selective mapping (SLM). In this paper a unique approach has been proposed to obtain a new code from the existing codes in order to reduce the bit error rate (BER), to mitigate the gap between the performance and Shannon limit while the bounded peak average power ratio (PAPR) of OFDM symbol is guaranteed. A new code based on the BCH with a Barthannwin Wave Filter has been proposed to achieve the desired results.

In this paper, a new large spreading code set with a uniform low cross-correlation is proposed. The proposed code set is capable of (1) increasing the number of assigned user (capacity) in a multicarrier code division multiple access (MC-CDMA) system and (2) reducing the peak-to-average power ratio (PAPR) of an orthogonal frequency division multiplexing (OFDM) system. In this paper, we derive a new code set and present an example to demonstrate performance improvements of OFDM and MC-CDMA systems. Our proposed code set with code length of N has K = 2N + 1 number of codes for supporting up to (2N + 1) users and exhibits lower cross correlation properties compared to the existing spreading code sets. Our results with subcarrier N = 16 confirm that the proposed code set outperforms the current pseudo-orthogonal carrier interferometry (POCI) code set with gain of 5 dB at bit-error-rate (BER) level of 10 −4 in the additive white Gaussian noise (AWGN) channel and gain of more than 3.6 dB in a multipath fading channel.

A new work based-wavelet transform is designed to overcome one of the main drawbacks that found in the present new technologies. Orthogonal Frequency Division Multiplexing (OFDM)is proposed in the literature to enhance the multimedia resolution. However, the high peak power (PAPR) values will obstruct such achievements. Therefore, a new proposition is found in this work, making use of the wavelet transforms methods, and it is divided into three main stages; de-noising stage, thresholding stage and then the replacement stage. In order to check the system stages validity; a mathematical model has been built and its checked after using a MATLAB simulation. A simulated bit error rate (BER) achievement will be compared with our previously published work, where an enhancement from 8×10-1 to be 5×10-1 is achieved. Moreover, these results will be compared to the work found in the literature, where we have accomplished around 27% PAPR extra reduction. As a result, the BER performance has bee...