Pooria Varahram

• Universiti Putra Malaysia

This paper proposes a new crest factor reduction scheme to reduce instantaneous-to-average power ratio (IAR) resulting decent peak reduction, and adjacent channel leakage ratio (ACLR) reduction, though the error vector magnitude (EVM) is significantly enhanced. In the conventional peak cancellation (CPC) technique, peak regrowth occurs as a result...

Because of its lack of feedback process and the simplicity of its searching algorithm, conventional selected mapping (CSLM) is an efficient peak-to-average power ratio (PAPR) reduction technique in orthogonal frequency division multiplexing systems compared to the present techniques such as partial transmit sequence and active constellation extensi...

This paper presents a novel low complexity technique for reducing the peak-to-average power ratio (PAPR) in orthogonal frequency division multiplexing systems followed by an efficient hardware co-simulation implementation of this technique by using a Xilinx system generator on field programmable gate array. Unlike the conventional scheme, the propo...

In this paper, we propose a novel technique to reduce the crest factor (CF) in orthogonal frequency division multiplexing systems. It consists of two inverse fast Fourier transform (IFFT) blocks, the input symbols of the first IFFT are the mapped symbols, whereas the input symbols of the second IFFT are the summations of the absolute value of the r...

This paper presents a novel low-complexity technique for reducing the peak-to-average power ratio (PAPR) in orthogonal frequency division multiplexing (OFDM) systems followed by an efficient hardware co-simulation implementation of this technique by using a Xilinx system generator on a field programmable gate array (FPGA). Through the comparison of...

This paper presents a novel low-complexity technique for reducing the Peak-to-Average Power Ratio (PAPR) in Orthogonal Frequency Division Multiplexing (OFDM) systems followed by an efficient hardware co-simulation implementation of this technique by using a Xilinx system generator on a Field Programmable Gate Array (FPGA). In this technique, each s...

The inherent character of the Power Amplifier (PA) on its non-linearity causes unwanted amplitude and phase distortions at the PA output signal. Faster information transmission speed together with the rapid changes in temperatures of electrical components incurs Memory Effects, the undesired spreading of the PA output signal. Digital Pre-distortion...

In this paper, we propose a novel technique to reduce the crest factor (CF) in orthogonal frequency division multiplexing systems. It consists of two inverse fast Fourier transform (IFFT) blocks, the input symbols of the first IFFT are the mapped symbols, whereas the input symbols of the second IFFT are the summations of the absolute value of the r...

In this paper, a nonlinear autoregressive with exogenous inputs (NARX) digital pre-distortion scheme to linearize power amplifiers is proposed. The proposed NARX digital pre-distortion gives better accuracy and spectral leakage suppression compared with other commonly used Volterra-based techniques. The stability criterion of the NARX digital pre-d...

In this paper, a low-complexity model is proposed for linearizing power amplifiers with memory effects using the digital predistortion (DPD) technique. In the proposed model, the linear, low-order nonlinear and high-order nonlinear memory effects are computed separately to provide flexibility in controlling the model parameters so that both high pe...

span lang="EN-US">In this paper, a low-complexity model is proposed for linearizing power amplifiers with memory effects using the digital predistortion (DPD) technique. In the proposed model, the linear, low-order nonlinear and high-order nonlinear memory effects are computed separately to provide flexibility in controlling the model parameters so...

A low-complexity peak-to-average power ratio (PAPR) reduction scheme in an orthogonal frequency division multiplexing system is proposed. The proposed scheme utilizes a new phase sequence based on a gray code structure and a similarity measurement block. Due to the ordered phase sequences, a noteworthy reduction capacity is obtained in terms of the...

In this letter, a new pre-distortion technique for power amplifiers in wideband applications is proposed. The proposed pre-distortion technique is based on Nonlinear Autoregressive with Exogenous inputs (NARX). The forward path of the proposed predictive method is based on the memory polynomial. Experimental validation is carried out with 4 carrier...

This study presents subblocks interleaving partial transmit sequence (SBI-PTS) technique having low complexity for reducing the peak-to-average power ratio in orthogonal frequency division multiplexing systems. In this technique, a new subblocks interleaver is proposed, in which each subblock is interleaved with the others. Moreover, a new optimisa...

Orthogonal frequency division multiplexing systems suffer from one main drawback which is a high peak-to-average power ratio (PAPR) that leads to power efficiency degradation and when feed to a power amplifier operating in the nonlinear region yields adjacent channel interference and inferior bit error rate performance. There are many methods to ov...

Peak to average power ratio (PAPR) is one of the main imperfections in the broadband communication systems with multiple carriers. In this paper, a new crest factor reduction (CFR) scheme based on interleaved phase sequence called Dummy Sequence Insertion Enhanced Partial Transmit Sequence (DSI-EPTS) is proposed which effectively reduces the PAPR w...

Due to no feedback process and simplicity in searching algorithm, conventional selected mapping (CSLM) is an efficient crest factor reduction (CFR) technique in orthogonal frequency division multiplexing (OFDM) systems. However high number of inverse fast Fourier transform (IFFT) block is required to achieve the desired PAPR reduction performance....

Due to no feedback process and simplicity in searching algorithm, conventional selected mapping (CSLM) is an efficient crest factor reduction (CFR) technique in orthogonal frequency division multiplexing (OFDM) systems. However high number of inverse fast Fourier transform (IFFT) block is required to achieve the desired PAPR reduction performance....

Due to the increasing demand of high data rate in recent years, orthogonal frequency division multiplexing (OFDM) and Direct up conversion transmitters (DCT) have gained significant interest. However such system’s efficiency can be compromised by front-end impairments such as In-phase Quadrature (I/Q) imperfections. In this paper the effects of IQ...

Enhanced partial transmit sequence (EPTS) and cross-correlation-PTS are two techniques for reducing peak-to-average power ratio (PAPR) in orthogonal frequency division multiplexing (OFDM) systems. EPTS is a low complexity technique compared to conventional partial transmit sequence (CPTS) and cross-correlation-PTS techniques which outperforms the c...

The present invention relates to method of reducing peak to average power ratio (PAPR).

Power Efficiency in Broadband Wireless Communications focuses on the improvement of power efficiency in wireless communication systems, especially of mobile devices. Reviewing cutting-edge techniques for conserving power and boosting power efficiency, the book examines various technologies and their impact on consumer devices. It considers each tec...

Nowadays, the OFDM support the growing request of higher data rate transportation in both wired and wireless communication. The SLM technique is recognized as one of the most capable methods which are applied in OFDM system in order to reduce the problem of high PAPR. However the major drawback of SLM is transmission of side information which has n...

One of the main imperfections in orthogonal frequency division multiplexing (OFDM) techniques is a peak-to-average power ratio (PAPR) or crest factor (CF). High crest factor signal forces a power amplifier in communication systems to back-off which leads to power efficiency degradation. Several techniques have been proposed in literature to mitigat...

In this paper, a comparison between the original and companded signal implemented in Coherent Optical OFDM (CO OFDM) is presented. The companded signal based on μ-law algorithm was applied at the transmitter to reduce the Peak to Average Power Ratio (PAPR) by enlarging small signals and compressing large signals. From the results, the companded sig...

Two of the most important techniques of Peak-to-average power ratio (PAPR) reduction in orthogonal frequency division multiplexing (OFDM) systems are Partial Transmit Sequence PAPR (PTS-PAPR) and Cross-Correlation-PTS. This paper investigates a complete analysis on these two techniques providing simulation and discussion of their performance on PAP...

One of the main imperfections in orthogonal frequency division multiplexing (OFDM) technique is a peak-to-average power ratio (PAPR) or crest factor (CF). High crest factor signal forces a power amplifier in communication systems to back-off which leads to power efficiency degradation. Several techniques have been proposed in literature to mitigate...

A method of peak to average power ratio (PAPR) reduction is provided, the method includes the steps of interleaving output of Inverse Fast Fourier Transform (IFFT) modulation and performing phase optimization, such that multiplication operations are eliminated without having to send side information to reduce bandwidth.

Power amplifiers are one of the costly devices in wireless communication systems and exhibit non-linearity. The problem of non-linearity in the power amplifier categorises in two disturbance impacts, output distortion and in-band distortion which lead to adjacent channel interference and constellation deviation, respectively. In order to gain maxim...

Orthogonal Frequency Division Multiplexing (OFDM) systems have a main drawback known as high Peak to Average Power Ratio (PAPR) or Crest Factor (CF). The main PAPR reduction techniques are Partial Transmit Sequence (PTS), Dummy Sequence Insertion (DSI), Selected Mapping (SLM), and the DSI-SLM. In this paper an innovative method known as Optimum Pha...

This paper presents a Digital Signal Processor (DSP) implementation of Digital Pre-distortion (DPD) targeting the 3rd Generation/4th Generation (3G/4G) wireless networks. The non-linearity of the Power Amplifier (PA) causes several issues such as Adjacent Channel Interference (ACI), power wastage, high energy consumption, and system inefficiency. T...

Peak-to-average power ratio (PAPR) is one of the main drawbacks in orthogonal frequency division multiplexing (OFDM) systems. High PAPR forces the power amplifier to back off in order to operate in its linear region, which degrades the power efficiency of the system. Several PAPR reduction techniques have been developed, but most of them have not c...

This article presents a novel peak-to-average power ratio (PAPR) reduction scheme based on the insertion of dummy random Gaussian (IDRG) subcarriers to the data constellation points in the frequency domain integrated with a partial transmit sequence (PTS) technique. The dummy signals are Gaussian random signals which have the same statistical distr...

One of the effective methods used for reducing peak-to-average power ratio (PAPR) in orthogonal frequency division multiplexing (OFDM) systems is selected mapping (SLM). In this paper, a new SLM scheme called DSI-SLM, which is a combination of dummy sequence insertion (DSI) and conventional selected mapping (C-SLM) is proposed. Previous techniques...

There is a major problem in orthogonal frequency division multiplexing (OFDM) systems that is known as high peak-to-average power ratio (PAPR), thus various PAPR reduction algorithms have been introduced. Selected mapping (SLM) and Partial transmit sequence (PTS) are two of the most attractive solutions because of their good performance without dis...

Orthogonal frequency division multiplexing (OFDM) is a robust transmission technique to combat the influence of wireless fading channels. However, OFDM suffers from high peak-to-average power ratio (PAPR) that significantly reduces the efficiency of the high power amplifier (HPA). This paper reviews the performance of few PAPR reduction techniques...

In this paper, the effects of peak-to-average power ratio reduction in nonlinear power amplifiers (PAs) by considering memory effects and of digital predistortion are investigated. A new predistortion technique is proposed, which is called the complex gain memory predistortion (CGMP) method. The CGMP is applied to compensate the dynamic memory effe...

Planning of energy-efficient protocols is critical for wireless sensor networks (WSNs) because of the constraints on sensor node's energy. Therefore, the routing protocol should be able to achieve uniform power dissipation during transmission to the sink node. In this paper, we present a self-optimization scheme for WSN which is able to utilize and...

In this paper the peak to average power ratio (PAPR) reduction and digital predistortion effects in orthogonal frequency division multiplexing (OFDM) systems are investigated. By applying a predistortion technique called complex gain memory predistortion (CGMP), power amplifier works at higher power efficiency. The proposed enhanced partial transmi...

High peak to average power ratio (PAPR) is the main drawback of orthogonal frequency division multiplexing (OFDM) systems. Some of the proposed PAPR reduction solutions are dummy insertion (DSI), selected mapping (SLM) and combined DSI-SLM scheme. This paper presents FPGA implementation of DSI-SLM scheme for OFDM signals. The results of the impleme...

The fast pace of development of telecommunications technology and the challenges presented with the increasing number of users for any service, anywhere, anytime, access creates new problems with on the base stations capability and the handover/handoff (HO) techniques. To face these challenges much research have been made to come out with algorithm...

In this paper a new partial transmit sequence (PTS) scheme called enhanced PTS (EPTS) is introduced to reduce the peak-to-average power ratio (PAPR) in orthogonal frequency division multiplexing (OFDM) systems. This is followed with the implementation procedure in field programmable gate array (FPGA). The new phase sequence reduces complexity signi...

Partial transmit sequence (PTS) is one of the most important techniques for reducing the peak to average power ratio (PAPR) in OFDM systems. This paper presents a low complexity PTS scheme by applying a new phase sequence. Unlike the conventional PTS which needs several inverse fast Fourier transform (IFFT) operations, the proposed scheme requires...

One of the effective methods used for reducing peak to average power ratio (PAPR) in OFDM systems is partial transmit sequence (PTS). In the conventional PTS (CPTS) several inverse fast Fourier transform (IFFT) operations and complicated calculation to obtain optimum phase sequence, increase the computational complexity of C-PTS. In this paper, we...

High PAPR is the main drawback of OFDM systems. DSI method, PTS method and SLM method are three of the most promising techniques to reduce PAPR. This Work studies these methods and there is a comparison between their performances.

High PAPR is the main drawback of OFDM systems. DSI method and SLM method are two of the most promising techniques to reduce PAPR.

In this paper a novel technique for reducing the peak to average power ratio (PAPR) reduction based on the addition of random signals with a complex Gaussian distribution (ADRG) and combining it with partial transmit sequence (PTS) is proposed. Unlike the conventional PTS (C-PTS) which needs several inverse fast Fourier transform (IFFT) operations,...

Power Amplifiers (PAs) are important parts of the transmitters. They amplify the signals that are going to be transmitted. With increasing the input power of the PA, it creates the nonlinearity at the output. The nonlinearity causes out of band distortion and in band distortion. To overcome these effects the power amplifier should be backed off but...

In this paper a novel technique for reducing the peak to average power ratio (PAPR) in OFDM systems by using the combination of the dummy sequence insertion (DSI) and partial transmit sequence (PTS) is proposed. In DSI increasing the number of dummy sequence decrease the transmission efficiency (TE) and in PTS the complexity increases when the numb...

Since division is not a standard operation for DSP processors and because it can be implemented in several different ways, there is no specific algorithm clearly to choose. It all depends on the requirements, such as accuracy, size and speed. A few suitable algorithms should be selected and implemented in VHDL for evaluation. The implementation is...

Power amplifiers are essential components in communication systems and are inherently nonlinear. The nonlinearity creates spectral growth beyond the signal bandwidth, which interferes with adjacent channels. It also causes distortions within the signal bandwidth, which decreases the bit error rate at the receiver. In digital predistortion system, a...

Efficient RF power amplifiers used in third generation systems require linearization in order to reduce adjacent channel inter-modulation distortion, without sacrificing efficiency. Digital baseband predistortion is a highly cost-effective way to linearize power amplifiers (PAs), but most existing architectures assume that the PA has a memoryless n...

In this paper the new digital predistortion technique is introduced. This technique is the combination of two techniques, complex gain predistortion and memory polynomial predistortion. By applying this technique all the memory contents of the power amplifier is suppressed. Simulations and results are examined with mini circuit power amplifier with...

The application of digital predistortion in base band signal is an extended method of amplifier linearization to reduce the Adjacent Channel Interference (ACI) in those systems in which a varying envelope modulation scheme like OFDM and MQAM is used. Digital baseband predistortion is a highly cost-effective way to linearize Power amplifiers (PAs),...

Digital predistortion of a baseband signal is a well-known method of power amplifier (PA) linearization used to reduce adjacent channel interference (ACI) in a non constant envelope modulation system. This paper discusses the application of adaptive digital baseband predistortion linearization to radio frequency (RF) power amplifiers (PAs) that exh...

Efficient RF power amplifiers used in third generation systems require linearization in order to reduce adjacent channel inter-modulation distortion, without sacrificing efficiency. Digital baseband predistortion is a highly cost-effective way to linearize Power amplifiers (PAs), but most existing architectures assume that the PA has a memoryless n...

Neural networks have gained a lot of important attention as fast and flexible tools for microwave modeling, simulation, optimization and design. In this paper new approach of neural networks is proposed to model the miniature X-band branch-line coupler. The obtained results are in excellent agreement with measured results available in the literatur...

The application of digital predistortion in base band signal is an extended method of amplifier linearization to reduce the adjacent channel interference (ACI) in those systems in which a varying envelope modulation scheme like OFDM and MQAM is used. Digital baseband predistortion is a highly cost-effective way to linearize power amplifiers (PAs),...