Peak-to-average Power Ratio Of OFDM System Research Articles

Reducing Complexity in PTS Scheme using Optimization Techniques to reduce PAPR in OFDM Systems

OFDM is a technique used to combat Inter Symbol Interference (ISI) in wireless communication systems. OFDM offers high reliable data rate over frequency selective channels. But the drawback is high Peak to Average Power Ratio (PAPR) which will affect the power amplifier in the RF front end. Partial Transmit Sequence (PTS) has proven to be the efficient technique to minimize the PAPR in OFDM systems and it does not affect the Bit Error Rate (BER) much. But PTS in turn suffers from high search complexity. The optimization algorithms can offer a tradeoff between the search complexity and PAPR reduction. In this work the phase factor optimization in PTS scheme is converted into a one dimensional optimization problem. Genetic Algorithm (GA), Simulated Annealing (SA) and Particle Swarm Optimization (PSO) are applied to the problem defined. They are also compared in terms of PAPR reduction and complexity. The fitness functions are chosen according to the optimization technique.

Improved Selected Mapping Technique for Reduction of PAPR in OFDM Systems

High peak to average power ratio (PAPR) is a limiting factor towards the performance of an OFDM system. Selected Mapping (SLM) is a popular peak to average power ratio (PAPR) reduction scheme used with the OFDM systems. In this technique, U set of candidate sequences are generated that leads to improvement in the PAPR reduction ability of the OFDM systems. The major concern of the conventional SLM is that as the number of candidates is increased, there is a proportional rise in the inverse fast Fourier transforms (IFFT) computations of the systems. In our article we have proposed a scheme in which we increase the number of candidate sequence as (U+U2/4) that leads to improved PAPR performance of the OFDM systems without any equivalent rise in the IFFT computations. It has been demonstrated that both the simulation and analytical results are well-approximated in our proposed schemes. We also estimate the threshold value of PAPR at a fixed value of complementary cumulative distribution function (CCDF) for different number of subcarriers and candidate sequences. Results demonstrate that our proposed scheme outperforms in terms of PAPR reduction ability of the OFDM signal and obtains effective PAPR threshold values with negligible loss in BER performance of the system.

A Novel Signal Scrambling Technique for PAPR Reduction in OFDM Systems

OFDM forms the basis of the upcoming next generation technologies so as to achieve higher data rates within a given bandwidth effectively. One of the major issues associated with OFDM is Peak to Average Power Ratio (PAPR) which needs to be minimized to get an efficient performance. The random variation in the signal amplitude of the OFDM signal leads to additional interference in the system and hence affecting the performance of HPA in non-linear region. In this paper, we propose a technique for the reduction of PAPR in OFDM systems with some increased complexity which works for any modulation type and any number of subcarriers. The simulation results show performance improvement with respect to the existing signal scrambling techniques

PAPR Performance Analysis of low Complexity SLM for Various Phase Sequences in MIMO-OFDM System

Multiple Input Multiple Output Orthogonal Frequency Division Multiplexing (MIMO OFDM) is a key technology for contemporary communication systems due to its spectral efficiency, higher data rates, better diversity gain, good link reliability and both inter symbol interference (ISI) and multipath fading free transmission. However, due to the presence of OFDM, MIMO-OFDM suffers from high peak to average power ratio (PAPR). Even though, several schemes are available to mitigate PAPR, there is no standard solution. Selective Mapping (SLM) significantly reduces the PAPR in OFDM systems at the cost of computational complexity (CC). The CC of SLM can be reduced by proper design of SLM. This paper considers a low complexity SLM (LC SLM) scheme in which both the CC and length of the index of selected phase sequence are significantly reduced. The PAPR of an SLM-OFDM depends on the number of subcarriers in OFDM, the number of candidate blocks in SLM and selected phase sequence and this paper investigate various phase sequences and analyses their PAPR performance. Simulation results show the superior performance of Riemann sequence over the other phase sequences.

Peak Power Reduction Using Improved Selective Mapping Technique for OFDM

OFDM has Major disadvantage is that it leads to high Peak to Average Power Ratio (PAPR) which is consider to be as the main implementation drawback. In this paper we are discussing about PAPR which affects the performance and efficiency of Power Amplifier (PA) and its influence by utilizing the Selective Mapping (SLM) technique in OFDM system for reduction of PAPR. the idea for improved SLM produces several independent signals based on converting the original data lock into many independent signal and then the signal has lowest PAPR that specific signal is transmitted. Also data rate trade-off exist at the receiver end when side information is detected for the recovery of data block. which leads to the reduction of data rate. Improved SLM techniques for reducing the PAPR is the most promising reduction technique in its non-uniform phase factor for PAPR reduction in multicarrier OFDM system. Furthermore the estimate expression by using Complementary Cumulative Distribution Function (CCDF) for PAPR has been discussed. Simulated results demonstrate that OFDMA signals using improved SLM technique carried significant effects in reduction of PAPR in OFDM system.

A partial transmit sequence technique with error correction capability and low computation

SUMMARYOrthogonal frequency division multiplexing (OFDM) is a popular transmission technique in wireless communication. Although already widely addressed in many studies, OFDM still has flaws, one of which is the occurrence of high peak‐to‐average power ratio (PAPR) in the transmission signal. The partial transmit sequence (PTS) technique is one method adopted to reduce high PAPR in OFDM systems. However, as PTS utilizes phase factors to generate multiple candidate signals, large amounts of calculation and time are required to search the candidate signal with the minimal PAPR, which will then be adopted as the final transmission signal. This paper proposes a novel PAPR reduction method, which can be applied in OFDM systems with M‐ary phase‐shift keying modulation. It not only requires less computation but also possesses error correction capabilities. More precisely, the proposed method is to divide a block‐coded modulation code into the direct sum of a correcting subcode for encoding information bits and a scrambling subcode for generating phase factors. Our proposed method is a suboptimal technique with low computation, because it uses a genetic algorithm with a partheno‐crossover operator as the transmitted signal selection mechanism. Simulation results show our proposed method has better PAPR performance than the GA‐PTS scheme. Based on the simulation results in Figures 5 and 6, it is evident that our proposed method can be employed in any OFDM system by using M‐PSK modulation.Copyright © 2013 John Wiley & Sons, Ltd.

SLM Technique Combined with a Random-Like Codingfor Reducing PAPR in OFDM Systems with No ExplicitSide Information

OFDM is an attractive technique for high data rate and reliable communication over fading channels and high peak-to-average power ratio (PAPR) is a notable drawback of orthogonal frequency-division mu ltiplexing (OFDM) systems. The main implementation drawback of this system is the possibility of high Peak to Average Power Ratio (PAPR). The idea in Selective Mapping (SLM) consists of converting the original data lock into several independent signals, and then transmitting the signal that ha s the lowest PAPR. The selected signal index, called side info rmation index, must also be transmitted to allow for the recovery of the data block at the receiver side, which leads to a reduction in data rate. In this paper, we develop a novel SLM PAPR reduction technique. In the novel proposed scheme, the alternative symbol sequences are generated by module 2 additions of data with the rows of cyclic Hadamard matrix with the same size, inserting the selected row’s number to avoi d transmitting any side information and specially using a random-like Irregular Repeat Accumulate (IRA) encoder for both PAPR and Bit Error Rate (BER) better performance. Therefore our proposed scheme in this paper is based on a nove l SLM method combined with a random-like coding of the transmitted data that have no need to use side information for detecting transmitted data in the receiver.

Utilizing a novel root companding transform technique to reduce PAPR in OFDM systems

AbstractOne major defect in orthogonal frequency division multiplexing systems is the high peak‐to‐average power ratio (PAPR) at the transmitter. The linear nonsymmetrical transform (LNST) technique, one of the companding transform (CT) techniques for PAPR reduction, offers excellent performance, but requires additional side information. In this paper, a new ‘root CT’ technique without additional side information is proposed, and it can reach a good trade‐off between the PAPR reduction and the bit error rate (BER). The theoretical analysis of the proposed root technique is also derived. The simulation results show that the proposed root CT technique can achieve more efficient PAPR reduction and better power spectrum density than those of the LNST technique. The BER of the proposed CT technique without additional side information is close to that of the LNST technique with additional side information when the AWGN or multipath fading channels are considered. Furthermore, the simulation results also demonstrate that the proposed technique offers better performance than that of the µ‐law technique over the AWGN and multipath fading channels. Copyright © 2010 John Wiley & Sons, Ltd.