Peak-to-average Power Ratio Reduction Techniques Research Articles

New SLM Technique with Low Complexity Based on Matrices Combined with DCT Transform for PAPR Reduction in OFDM Communication Systems

Abstract Orthogonal Frequency Division Multiplexing (OFDM) is an efficient method of data transmission for high speed communication systems. However, the main drawback of OFDM systems is that, it exhibits high Peak to Average Power Ratio (PAPR) of the transmitted signals which causes inefficient use of the High Power Amplifier (HPA) and could limit transmission efficiency. OFDM consist of large number of independent subcarriers, as a result of which the amplitude of such a signal can have a high peak values. Selected Mapping (SLM) technique is one of the promising PAPR reduction techniques for Orthogonal Frequency Division Multiplexing (OFDM). But this reduction technique results in a huge amount of computation complexity which is costly and time consuming. This technique however increases the computational and phase search complexity and PAPR reduction is performance largely dependent on the selection of random phase sequences. In this paper, one effective PAPR reduction scheme is proposed. These techniques combine the DCT with SLM techniques and we proposed the use of Hanowa, Riemann, and Hilbert matrices to obtain phase sequences for the SLM. The experimental results clearly prove that Hanowa matrix approach offers the best PAPR reduction in comparison with the SLM scheme using other matrices for phase sequence. This approach also avoids randomness in phase sequence selection, which makes it simpler to decode at the receiver. As added benefits, the matrix can be generated at the receiver end to obtain the data signal and hence it is not required to transmit Side Information (SI).

Performance Improvement of MIMO-OFDM Wireless Systems using PAPR Reduction Techniques

High Peak to Average Power Ratio (PAPR) for MIMOOFDM system is still a demanding area and difficult issue. The radio transmitter stations for covering and getting enough transmitted power in their desired area has to use High Power Amplifier (HPA). On the other hand, in order the HPA to have the most output power efficiency must be designed to work close to the saturation region, therefore due to the high PAPR of input signals, a factor which is called memory-less nonlinear distortion will affect the communication channels. We know the MIMO-OFDM receiver’s efficiency is sensitive to the HPA. If the high power amplifier doesn’t work in linear region, it can cause the out-of-band power to be kept under the specified limits. This condition can cause inefficient amplification and expensive transmitters, thus it is necessary to investigate PAPR reduction techniques for MIMO-OFDM system. By now, for reducing PAPR, numerous techniques have been recommended. In this paper the performance and the efficiency of two types of them will be discussed and simulated and then we will propose our suggested method for a conventional OFDM system. General Terms Orthogonal Frequency Division Multiplexing (OFDM), Peak– to-Average Power Ratio (PAPR), High Power Amplifier (HPA), Transmit sequence (PTS), Probability Distribution Function (PDF), Mat lab program simulation.

SER analysis of PTS based techniques for PAPR reduction in OFDM systems

A major drawback of orthogonal frequency division multiplexing (OFDM) is high peak-to-average power ratio (PAPR). An OFDM signal with high PAPR requires power amplifier@?s (PAs) with large linear operating ranges but such PAs are difficult to design and costly to manufacture. Therefore, to reduce PAPR various methods have been proposed. One of the existing technique to reduce PAPR is partial transmit sequences (PTS). The major drawback of this technique is that it requires transmission of side information (SI) with each OFDM symbol, which results in low bandwidth efficiency. It is hard to recover the side information from the OFDM signal received at the receiver. The two methods, which do not require SI to decode the OFDM symbol at the receiver, are multi-point square mapping combined with PTS (M-PTS) and concentric circle mapping based PTS (CCM-PTS). In this paper, the SER performance of PTS based methods namely CCM-PTS and M-PTS over AWGN channel is mathematically analyzed. The SER performance of CCM-PTS over AWGN is analyzed using two decoding techniques, namely minimum distance decoding and circular boundary decoding, whereas M-PTS is analyzed using minimum distance decoding. The simulation results for SER performance of CCM-PTS and M-PTS, over fading channel, have been presented using computer simulations and the SER performance of CCM-PTS by both the decoding techniques is compared with M-PTS. Also, a comparison of PAPR reduction capability and computational complexity of CCM-PTS and M-PTS has been presented. CCM-PTS method almost has the same PAPR reduction capability as M-PTS, but its SER performance is better than M-PTS and uses a simpler method to decode the data symbols.

Hadamard Transform Combined With Companding Transform Technique for PAPR Reduction in an Optical Direct-Detection OFDM System

In this paper, we propose a novel method to reduce the high peak-to-average power ratio (PAPR) of the optical orthogonal frequency division multiplexing (OFDM) signal. The method is based on the technique of the Hadamard transform combined with a companding transform. We experimentally demonstrate that, in an optical intensity-modulation direct-detection OFDM transmission system, the hybrid method has better performance in reducing the PAPR compared with the case of applying only the Hadamard transform or only a companding transform.

An efficient designed prototype technique for OFDM PAPR reduction using FPGA

SUMMARYIn this paper, a proposed designed technique to reduce OFDM peak‐to‐average power ratio (PAPR) value is performed. This designed technique contains a new block, which is inserted in the OFDM system. This proposed block is applied to the WiMAX system as an example of the OFDM technology. Afterwards, several MATLAB programs are executed to discuss the behavior and the characteristics of this proposed block. In addition, the effect of its insertion on the original system is studied. Because of this insertion, 0‐dB OFDM PAPR value can be achieved. Furthermore, it can be synthesized practically. This proposed system is implemented over a field‐programmable gate array (FPGA). The designed circuit is characterized by both its low complexity and its high speed. Moreover, it is a portable circuit. This means that it can be implemented over any FPGA kit regardless of its technology. Copyright © 2012 John Wiley & Sons, Ltd.

A Novel Technique for PAR Reduction in DRM

PAR (Peak-to-Average Power Ratio) is one of significant issues in a DRM transmitter. To reduce the PAR of DRM signals, an iterative pre-distortion technique is proposed in this paper. This technique improves the RMS (Root Mean Square) power of transmitter while the effect on DRM signal quality is negligible. Research has been done on the impact that the processing parameters caused to DRM signal quality. Simulation and test indicate that in the case that the quality requirements for the RF signal in the DRM specification is satisfied, DRM output power is increased to 9kw from 5kw (RMS power) based on a 10kw (carrier power) DX transmitter, thereby improving the capability of the transmitter greatly.

A Novel SLM based PAPR reduction Technique in OFDM-MIMO System

Orthogonal Frequency Division Multiplexing (OFDM) is annew method for fourth generation wireless communication.MIMO-OFDM has become a promising candidate for highperformance 4G broadband wireless communications.However, one main disadvantage of MIMO-OFDM is thehigh peak-to-average power ratio (PAPR) of the transmitter’soutput signal on different antennas. In this paper, we present anew noble SLM PAPR reduction techniques such asselective mapping technique and Partial transmit sequencetechniques and shows which of these PAPR reductiontechniques are more effective to reduce PAPR in OFDMMIMO.

An Efficient Adaptive Technique with Low Complexity for Reducing PAPR in OFDM-Based Cognitive Radio

Cognitive radio (CR) is considered nowadays as a strong candidate solution for the spectrum scarcity problem. On standards level, many cognitive radio standards have chosen Non-Contiguous Orthogonal Frequency Division Multiplexing (NC-OFDM) as their modulation scheme. Similar to OFDM, NC-OFDM suffers from the problem of having a high Peak to Average Power Ratio (PAPR). If not solved, either the transmitted signal will be distorted, which will cause interference to primary (licensed) users, or the effeciency of the power amplifier will be seriously degraded. The effect of the PAPR problem in NC-OFDM based cognitive radio networks is worse than normal OFDM systems. In this paper, we propose enhanced techniques to reduce the PAPR in NC-OFDM systems. We start by showing that combining two standard PAPR reduction techniques (interleaver-based and selective mapping) results in a lower PAPR than using them individually. Then, an “adaptive number of interleavers” will be proposed that achieves the same performance of conventional interleaver-based PAPR reduction while reducing the CPU time by 41.3%. Finally, adaptive joint interleaver with selective mapping is presented, and we show that it gives the same performance as conventional interleaver-based technique, with reduction in CPU time by a factor of 50.1%.

Combined channel estimation and PAPR reduction technique for MIMO–OFDM systems with null subcarriers

In this article, we address the challenges regarding the provision of channel state information as well as reducing peak-to-average power ratio (PAPR) of a multiple input multiple output orthogonal frequency multiplexing (MIMO–OFDM) system. The mean squared error (MSE) of the channel estimate is adopted as the optimization criterion to design pilot symbols for channel estimation in MIMO–OFDM systems with null subcarriers. We design the placement and power distribution to the pilot symbols for multiple transmit antennas to minimize the MSE of the least square (LS) channel estimates. To reduce interference of the pilot symbols transmitted from different antennas, an algorithm to guarantee that pilot symbols are disjoint from any other transmitter pilot set is proposed. To efficiently reduce the PAPR of the MIMO–OFDM signals, a method that mixes dummy symbols and phase information of the pilot symbols is presented. Simulation results based on IEEE 802.16e are presented to illustrate the superior performance of our proposed channel estimation method over the existing standard and the partially equi-spaced pilot symbols. We also demonstrate that, by mixing the dummy symbols and phase information of the pilot symbols, the PAPR of the MIMO–OFDM signals can significantly be reduced.

Low-complexity PAPR reduction technique for OFDM systems using modified widely linear SLM scheme

In this paper, a modified widely linear selective mapping (MWL-SLM) scheme is proposed to reduce the peak-to-average power ratio (PAPR) of the orthogonal frequency-division multiplexing (OFDM) systems. In the proposed MWL-SLM scheme, through partition one complex signals into two real signals and combining the linear properties of the Fourier Transform, at most 4M2 candidate signals can be obtained but only require M inverse fast Fourier transform (IFFT) operations. As a result, the proposed SLM scheme has the ability to generate more candidates when compared with conventional SLM (C-SLM) and widely linear SLM (WL-SLM). Therefore, MWL-SLM outperforms C-SLM and WL-SLM for the same computational cost of IFFT operations. Alternatively, for a given number of candidates, MWL-SLM has slightly inferior PAPR reduction performance to C-SLM and WL-SLM but requires less IFFT operations to be implemented, thus resulting in a lower computational complexity. Simulation results demonstrate the effectiveness of the proposed scheme.

Performance enhancement of OFDM signals using PAPR reduction Techniques and the Comparison of their Performance

Orthogonal frequency division multiplexing(OFDM) is a prominent technique for providing high Quality of service(QOS) to the users by mitigating the fading of signals and also for providing high data rates in multimedia services. But Peak to Average power ratio(PAPR) is a major technical challenge in OFDM which reduces the efficiency of RF Power amplifiers. In this paper, we describe the PAPR reduction techniques in OFDM signals and compare their performance.

Overview Of MC CDMA Papr Reduction Techniques

High Peak to Average Power Ratio (PAPR) of the transmitted signal is a critical problem in multicarrier modulation systems (MCM) such as Orthogonal Frequency Division Multiplexing (OFDM), and Multi-Carrier Code Division Multiple Access (MC CDMA) systems, due to large number of subcarriers. High PAPR leads to reduced resolution, and battery life. It also deteriorates system performance. This paper focuses on review of different PAPR reduction techniques with attendant technical issues as well as criteria for selection of PAPR reduction technique. To reduce PAPR the constraints are low power consumption, and low Bit Error Rate (BER). Spectral bandwidth is improved by better spectral characteristics, and low complexity/cost.

PEAK-TO-AVERAGE POWER RATIO REDUCTION OF OFDM SIGANLS

Orthogonal frequency division multiplexing (OFDM) is a form of multicarrier modulation technique with high spectral efficiency and immunity to interference. Despite of many advantages the main disadvantage of OFDM is that the time domain of OFDM signal which is a sum of subcarrier sinusoids leads to high Peak-to-Average power ratio (PAPR). A simple technique used to reduce the PAPR of OFDM signals is to clip the signal to a maximum allowed value, at the cost of bit error rate(BER) degradation and out-ofband radiation. The other method is Selective mapping method(SLM) technique which is a probabilistic technique for PAPR reduction with aim of reducing the occurrence of peaks in a signal. In this project partial transmit (PTS) scheme along with the threshold technique has been simulated using Matlab and the simulation results shows that the technique performs better. To compare the results SLM and clipping methods are also simulated.

Techniques for PAPR Reduction in OFDM Systems

Orthogonal Frequency Division Multiplexing (OFDM) has been focused on in high-data-rate wireless communication research. But the high Peak-to-Average Power Ratio (PAPR) is one of the main obstacles to limit wide applications of OFDM. In this paper, based on the definition of the PAPR in OFDM systems, these techniques on PAPR reduction are presented, including signal distortion, signal scrambling, and block coding. The advantages and disadvantages of these techniques are discussed in detail and some performances are achieved by Monte Carlo simulations.

A Parallel Combinatory OFDM System with Weighted Phase Subcarriers

Orthogonal Frequency Division Multiplexing (OFDM) is usually regarded as a spectral efficient multicarrier modulation technique, yet it suffers from a high peak-to-average power ratio (PAPR) problem. Among all the existing PAPR reduction techniques in OFDM systems, side information based PAPR reduction techniques such as partial transmit sequence (PTS) and selective mapping (SLM) schemes, have attracted the most attention. However, the transmission of side information results in somewhat spectral loss and this does not significantly improve the bit error rate (BER) performance. Parallel combinatory (PC) OFDM yields higher spectral efficiency (SE) and better BER performance on Gaussian channels,while is a little but not obvious PAPR improvement over the ordinary OFDM system. This investigation aimed to design a ?perfect? OFDM system. We introduce the side information to rotate the subcarrier phases of our novel PC-OFDM system structure, and call this new system the SIPC(Side information based Parallel Combinatory)-OFDM system. The proposed system achieves better PAPR and SE performance. In addition, considering the tradeoff of system parameters, the proposed system also has the properties of a higher BER.

Companding Technique for Reducing Peak-to-Average Power Ratio in OFDM Linear Coded Systems

Orthogonal Frequency division multiplexing (OFDM) is a very attractive technique in wireless communications which provides robustness to channel fading and immunity to impulse interference. Despite of its advantages, one of the major drawbacks of OFDM system is very high peak-to-average power ratio (PAPR). Among the various PAPR reduction techniques, companding appears attractive for its simplicity and effectiveness. In this paper novel Low density parity check (LDPC) encoded new companding technique is proposed which offers improved bit error rate, minimizes out-of-band interference and reduce PAPR effectively. Simulation results illustrates the performance of the system under Additive White Gaussian Noise (AWGN) and further evaluation is done for comparing the proposed companding technique with previous techniques.

Low-Complexity Distortionless Techniques for Peak Power Reduction in OFDM Communication Systems

A high peak-to-average power ratio (PAPR) is one of the major drawbacks to using orthogonal frequency division multiplexing (OFDM) modulation. The three most effective distortionless techniques for PAPR reduction are partial transmit sequence (PTS), selective mapping (SLM), and tone reservation (TR). However, the high computational complexity due to the inverse discrete Fourier transform (IDFT) is a problem with these approaches. Implementation of these techniques typically employ direct computation of the IDFT, which is not the most efficient solution. In this paper, we consider the development and performance analysis of these distortionless techniques in conjunction with low-complexity IFFT algorithms to reduce the PAPR of the OFDM signal. Recently, proposed IFFT-based techniques are shown to substantially reduce the computational complexity and improve PAPR performance.

Peak-To–Average Power Ratio Reduction of Ofdm Siganls

Orthogonal frequency division multiplexing (OFDM) is a form of multicarrier modulation technique with high spectral efficiency and immunity to interference. Despite of many advantages the main disadvantage of OFDM is that the time domain of OFDM signal which is a sum of subcarrier sinusoids leads to high Peak-to-Average power ratio (PAPR). A simple technique used to reduce the PAPR of OFDM signals is to clip the signal to a maximum allowed value, at the cost of bit error rate(BER) degradation and out-ofband radiation. The other method is Selective mapping method(SLM) technique which is a probabilistic technique for PAPR reduction with aim of reducing the occurrence of peaks in a signal. In this project partial transmit (PTS) scheme along with the threshold technique has been simulated using Matlab and the simulation results shows that the technique performs better. To compare the results SLM and clipping methods are also simulated.

Reducing Peak-to-Average Power Ratio of a Turbo Coded OFDM

Peak to Average Power Ratio (PAPR) is defined as the instantaneous power (maximum value) to the average power ratio. PAPR is considered to be a major problem in OFDM systems. This problem can cause radical unexpected behavior of the signal fluctuation. This fluctuation is constituted by a large number of power states. The enormous number of these states leads to an additional complexity of ADCs and DACs. This research addresses the previous problem in OFDM systems utilizing Turbo Codes. μLaCP technique is employed for the purpose of decreasing PAPR. Moreover, our OFDM system was simulated in the presence of an AWGN channel with four types of codes (without the presence of ADCs and DACs). These were constituted of PCCC (typical and new), SCCC, and Convolutional Codes. Our Turbo Coded OFDM exhibited unchanged BER performance before and after the use of μLaCP technique. This was accomplished by modifying our previous PAPR reduction technique without sacrificing greatly its attributes.

A New Peak Clipping Algorithm for PAPR Reduction in OFDM

The peak-to-average-power ratio (PAPR) is one of the major problems of Orthogonal Frequency Division Multiplexing (OFDM) systems. Various PAPR reduction techniques have been given in the past. Among these techniques, the clipping technique has been widely adopted as a practical scheme because of its low computational complexity and simplicity in implementation, while the pre-coding technique is known to provide good PAPR reduction with improved bit error rate (BER) performance. In this paper, a combination of clipping and pre-coding is proposed to reduce PAPR with almost same BER performance as given by individual pre-coding technique. The proposed technique gives good result because the clipping noise of combined scheme would be less than that of single clipping. Also the clipping used in this paper is not hard as used in conventional clipping. A new clipping algorithm is proposed which is based on averaging of high amplitude samples. In addition, an another pulse shape called modified Bartlett Hanning (MBH) is proposed to generate pre-coding matrix and its performance is compared with square root raised cosine (SQRC) pulse shape.dB.