Selected Mapping Scheme Research Articles

A Selected Mapping Technique Using Interleavers for PAPR Reduction in OFDM Systems

In this article, we propose a new selected mapping (SLM) technique using interleavers for reducing high peak-to-average-power ratio (PAPR) in orthogonal frequency division multiplexing systems. The proposed technique can be considered as a modified version of the conventional SLM technique where a set of candidate symbol blocks can be generated from the original symbol block by inserting some pre-known block interleavers between the mapper and the phase rotation multipliers. One of the advantages of this approach is that with very low complex block interleavers the PAPR performance of the SLM scheme can be improved without increasing the number of IFFTs. Simulation results show that the proposed algorithm has better PAPR performance than the conventional SLM for a given number of IFFTs with no additional side information.

XMapDB-Sim: Performance Evalaution on Model-based XML to Relational Database Mapping Choices

<span>XML has emerged as the standard for information representation over the Internet. However, most enterprises today have long secured the use of relational databases. Thus, it is crucial to map XML data into relational data to provide seamless integration between these database infrastructures. Many mapping techniques have been proposed, yet, none has provides a unified view on these techniques. Ultimately, understanding how these techniques work is important especially if one needs to decide which technique to adopt in their organization. This paper (i) reviews on some existing model-based mapping schemes focusing on how the mapping technique works, the advantages and the disadvantages, (ii) present the simulation engine to evaluate the performance of selected mapping schemes, (iii) highlight the future direction of the related area.</span>

PAPR Reduction for Visible Light Communication Systems Without Side Information

It is well known that visible light communication (VLC) systems with the direct current-biased optical orthogonal frequency division multiplexing (DCO-OFDM) scheme suffers from high peak-to-average power ratio (PAPR), which leads to serve distortion and degradation of the output of light emitting diodes. Selected mapping (SLM) technique is an attractive PAPR reduction technique for radio frequency OFDM systems. However, conventional SLM (CSLM) techniques cannot be adopted directly in DCO-OFDM VLC systems because DCO-OFDM VLC signals are restricted to have positive real values. Moreover, CSLM requires transmission of side information (SI) to identify which candidate signal is selected. To avoid the transmission of SI, a novel phase sequence is proposed for the SLM scheme with blind SI detection in DCO-OFDM VLC systems. The proposed phase sequences consist of the magnitude extension and phase rotation factors, where the former factors enable the blind detection of SI, and the latter factors aim to decrease the PAPR. Particularly, the magnitude extension factors are designed to have the symmetry and periodicity. Compared with basic DCO-OFDM with no PAPR reduction scheme, the proposed scheme achieved significant PAPR reductions of 2.1 dB, 3.4 dB, 4 dB, and 4.2 dB for a complementary cumulative distribution function of $10^{-3}$ and $V=4$ , $V=8$ , $V=16$ , and $V=31$ , respectively. Simulation results show that the proposed schemes achieve comparable PAPR reduction performance with the CSLM scheme without the need for SI. Moreover, the proposed SI detection scheme achieves almost the identical bit error rate performance as the CSLM scheme with perfect SI detection with a slight increase in transmitted average power and lower computational complexity.

A novel improved SLM scheme of the PAPR reduction technology in CO-OFDM systems

The higher peak-to-average power ratio (PAPR) is a major shortcoming of coherent optical orthogonal frequency division multiplexing (CO-OFDM) systems. Selective mapping (SLM) technology can effectively reduce the probability of high PAPR, but it has higher computational complexity, and requires additional bandwidth to transmit the side information, which will affect the transmission efficiency of the system. In response to these shortcomings, a novel improved SLM (NI-SLM) scheme with low complexity and without side information is proposed. Simulation results show that the proposed scheme can exponentially reduce the computational complexity, and the bit error rate (BER) performance can greatly approach the original signal. What’s more, it shows the better PAPR reduction performance.

New SLM scheme to reduce the PAPR of OFDM signals using a genetic algorithm

Abstract Selected mapping (SLM) is a popular peak-to-average power ratio (PAPR) reduction technique suitable for use in orthogonal frequency division multiplexing (OFDM) systems as it achieves good PAPR reduction performance without signal distortion. However, SLM requires a bank of inverse fast Fourier transforms (IFFTs) to produce candidate signals, resulting in high computational complexity. In this paper, we introduce a novel SLM technique based on conversion matrices (CM) and a genetic algorithm (GA) that requires only one IFFT module. Simulation results indicate that the proposed method obtains desirable PAPR reduction performance with low computational complexity.

Evaluating and Reducing the Envelope Fluctuations of OFDM Signals Based on Distortion Prediction

Abstract Orthogonal frequency division multiplexing (OFDM) signals with large envelope fluctuations are prone to be affected by power amplifier (PA), resulting in degradation of system performance. Peak-to-average power ratio (PAPR) and cubic metric (CM) are commonly used as the reduction criteria of envelope fluctuations of OFDM signals. However, our analysis shows that minimizing the PAPR or CM does not necessarily mean the optimization of system performance, since both metrics are inadequate to quantify the distortion in nonlinear OFDM transmission. In this paper, we fully discuss the effects of PA nonlinearity on OFDM signals and propose a new metric called distortion component metric (DCM), which is closely related to the nonlinear distortion caused by the PA. We compare the system performance when several metrics are respectively used as the reduction criterion for the selective mapping scheme. It is shown that in the presence of memoryless or memory PA, the usage of DCM can provide better inband and out-of-band performance than PAPR and CM.

Analysis of Oversampling Effect on Selected Mapping Scheme Using CORR Metric

Analysis of Oversampling Effect on Selected Mapping Scheme Using CORR Metric

A Low-Complexity Architecture for PAPR Reduction in OFDM Systems With Near-Optimal Performance

Selected mapping (SLM) schemes are widely used to reduce the peak-to-average power ratio (PAPR) in orthogonal frequency-division multiplexing (OFDM) systems. Various time-domain approaches have been proposed for reducing the number of inverse fast Fourier transform (IFFT) operations required to generate the candidate signals in traditional SLM schemes. However, the resulting time-domain-generated signals are somewhat correlated, and thus, the PAPR reduction performance is seriously degraded. Accordingly, this paper proposes a novel PAPR reduction method in which frequency-domain phase rotation, cyclic shifting, complex conjugate, and subcarrier reversal operations are all employed to increase the diversity of the candidate signals. Furthermore, to circumvent the multiple-IFFT problem, all of the frequency-domain operations are converted into time-domain equivalents. It is shown that the subcarrier partitioning and reassembling processes are key to realizing low-complexity time-domain equivalent operations. Moreover, it is shown theoretically and numerically that the computational complexity of the proposed scheme is significantly lower than that of the traditional SLM method and that the PAPR reduction performance is within 0.001 dB of that of SLM. Overall, the results indicate that among all of the low-complexity architectures proposed in the literature, the method proposed in this paper most closely approximates the PAPR reduction performance of the traditional SLM scheme.

A Novel Parallel Artificial Bee Colony Algorithm and Its PAPR Reduction Performance Using SLM Scheme in OFDM and MIMO-OFDM Systems

In this letter, we propose a parallel artificial bee colony (P-ABC) algorithm based on a new search strategy. Performance of the P-ABC is tested for peak-to-average power ratio (PAPR) reduction problem using selected mapping (SLM) scheme in both orthogonal frequency division multiplexing (OFDM) and multiple-input multiple-output (MIMO)-OFDM systems. Moreover, standard ABC and two different modified ABC algorithms—ABC/best/1 and modified ABC/best/1—are proposed for the SLM scheme. Simulation results show that the proposed P-ABC provides good PAPR reduction and bit-error-rate performances with low computational complexity.

Performance Evaluation of a Low Complexity Row-Column Transform Approach for SLM Based OFDM Transmission System

Selected mapping (SLM) technique is commonly employed for reducing peak to average power ratio (PAPR) in orthogonal frequency division multiplexing (OFDM) systems. Conventional SLM scheme has better spectral efficiency, but requires a bank of inverse fast Fourier transforms (IFFTs) to produce candidate signals, resulting in a dramatic increase in computational complexity. To reduce the computational complexity of the SLM technique, this paper proposes a new PAPR reduction scheme of OFDM system, called a modified fast T-transform based SLM OFDM scheme, which considerably reduces the computational complexity with better PAPR reduction performance compared to the conventional T-SLM OFDM scheme. The proposed scheme is analytically and numerically evaluated for the OFDM system specified in the IEEE 802.16d standard. For the OFDM system with 256 subcarriers, the proposed scheme can reduce the complex multiplications by 68.7 % with the lower PAPR by range of 7 dB which is about 1 dB less than the conventional SLM based OFDM.

Chaos‐based selected mapping scheme for physical layer security in OFDM‐PON

A novel chaos-based selected mapping (SLM) scheme is proposed for physical layer security in OFDM-PONs, where a Hénon chaos map is employed to create a large key space for OFDM data encryption. The transmission performance is significantly improved due to the peak-to-average power ratio reduction in the SLM scheme. High quality 8.9 Gbit/s 16-QAM OFDM encrypted data transmission is demonstrated over a 20 km single-mode fibre.

PAPR Analysis of Class-III SLM Scheme Based on Variance of Correlation of Alternative OFDM Signal Sequences

Selected mapping (SLM) is a well-known peak-to-average power ratio (PAPR) reduction technique for orthogonal frequency division multiplexing (OFDM) systems. Recently, a low-complexity SLM scheme, called Class-III SLM scheme, was proposed, which performs only one inverse fast Fourier transform (IFFT) to generate alternative OFDM signal sequences. By randomly selecting the cyclic shift and rotation values, Class-III SLM scheme can generate up to $N^{3}$ alternative OFDM signal sequences, where $N$ is the IFFT size. However, all $N^{3} $ alternative OFDM signal sequences do not achieve good PAPR reduction performances. Therefore, an efficient selection method of good rotation and cyclic shift values is needed, which results in good PAPR reduction performance.

PAPR and ICI Reduction of OFDM Signals Using New Weighting Factors from Riemann Matrix

Orthogonal frequency division multiplexing (OFDM) systems are significantly affected by peak-to-average-power ratio (PAPR). One of the straightforward methods to solve this problem is to use selected mapping (SLM) algorithm. The main idea of SLM scheme is to select the phase factors that minimize the PAPR and transmit these factors as side information (SI). In this paper, a new phase factors based on the diagonal elements of Riemann matrix is proposed. The results indicates that the introduced scheme has better PAPR reduction and power spectral density (PSD) performance compared to several SLM-based methods. Further, it does not need SI transmission. Also bit error rate (BER) of the proposed phase factor does not degrade with respect to conventional SLM.

SLM and Clipping Joint Algorithm for PAPR Reduction in OFDM System

As one of the most appealing techniques, selective mapping (SLM) provides an efiective solution for Peakto-average Power Ratio (PAPR) reduction in Orthogonal Frequency Division Multiplexing (OFDM) systems, however, results in large computational complexity simultaneously. As compared to SLM, clipping provides a more simple way towards a better PAPR performance, whereas results in degradation of the Bit Error Rate (BER) performance. In this paper, we proposed a joint algorithm called SLM and Quantization Clipping (SLM-QC) scheme, which combined the conventional SLM technology with a modifled quantization clipping scheme. The proposed scheme achieves a better exploitation of advantages brought about by each technique alone, with the tradeofi between the PAPR performance and the BER performance being well balanced.

Swapped SLM scheme for reducing PAPR of OFDM systems

The selected mapping (SLM) scheme is a competent method for reducing the high peak-to-average power ratio (PAPR) of orthogonal frequency division multiplexing (OFDM) signals. One drawback of the conventional SLM (C-SLM) scheme is the high computational complexity. To reduce the complexity of C-SLM, the real and imaginary parts of the OFDM signals are treated separately. The even and odd sequences of the real and imaginary parts are obtained using the Fourier transform properties. More candidates are generated by the different combination of all the sub-sequences. The proposed scheme has a lower computational complexity using only M inverse fast Fourier transform (IFFT) operations to generate M4 candidates. The simulation results show that the proposed scheme achieves good PAPR reduction performance and also reduces the computational complexity significantly compared with the C-SLM scheme.

Post-IFFT-Modified Selected Mapping to Reduce the PAPR of an OFDM System

Orthogonal frequency-division multiplexing is now one of the most important modulation techniques due to its advantages. Despite its ability to overcome the equalization problem, multipath fading channels, and other issues, this system has a serious problem concerning the high output peaks with respect to the average power, which is called the peak-to-average power ratio (PAPR). Selected mapping (SLM), partial transmitted sequence, and amplitude clipping and filtering are some efficient methods to reduce the PAPR. In a previous work, we slid a single-phase rotation vector on the data sequence in the frequency domain to reduce the PAPR and the complexity compared to the conventional SLM. In this paper, we present a novel method that utilizes the same approach of our previous work, but it processes the data after the inverse fast Fourier transform block (time-domain operations) using a modified version of the SLM scheme, which has less computational complexity than the conventional one. The mathematical derivations and the simulation results show that the PAPR, the computational complexity, and the side information were reduced significantly by the proposed method.

Peak-to-Average Power Ratio Reduction of OFDM Signals by Applying Low Complexity SLM and Clipping Hybrid Scheme

This paper presents performance analysis of Peak to Average Power Ratio (PAPR) Reduction techniques in Orthogonal Frequency Division Multiplexing (OFDM) System such as Clipping, Partial Transmit Sequence (PTS), Selective Mapping (SLM) and SLM with Clipping (Hybrid Scheme) .Complementary Cumulative Distribution Function (CCDF) is calculated for each technique with different number of sub carriers in order to analyze PAPR reduction performance and also compared with pure OFDM signal. According to our simulation results, SLM with clipping (Hybrid) technique has good PAPR reduction performance than other conventional methods, with less computational complexity.

A New Modified SLM Scheme for Wireless OFDM Systems Without Side Information

To avoid the transmission of side information and decrease the computational complexity in the conventional selected mapping (SLM) scheme, a novel set of conversion matrices (CMs) is proposed for the modified SLM scheme, and the signal processing scheme to remove the weighted factors on each subcarrier is also derived for wireless orthogonal frequency-division multiplexing (OFDM) systems. Computer simulations show that, without side information, the new scheme can achieve similar peak-to-average power ratio (PAPR) reduction and bit error rate (BER) performance with even lower computational complexity as compared with the available modified SLM schemes with the CMs.

A Novel Approach for SLM based PAPR Reduction using Genetic Algorithm

An SLM (Selected Mapping) is an effective algorithm to reduce PAPR (Peak to Average Power Ratio) in OFDM (orthogonal frequency division multiplexing) signal without distortion. However the SLM scheme needs to dispose U paths of IFFT (Inverse Fourier Transform), which increases the computational burden and reduces the signal transmission rate. This paper offers an improved algorithm that based on Genetic Algorithm. The proposed algorithm executes the selection before the IFFT module and only selects one sequence with the highest randomness to be transmitted. Because only one path of signal is transmitted in IFFT modules, the proposed algorithm has lower complexity compares with SLM. Moreover, it has advantages in enhancing the signal transmission rate and decreasing the PAPR of OFDM signals.

SLM‐based data position permutation method for PAPR reduction in OFDM systems

ABSTRACTThe high peak‐to‐average power ratio (PAPR) in orthogonal frequency division multiplexing (OFDM) systems not only increases the complexity of the analog‐to‐digital (A/D) and digital‐to‐analog (D/A) converters but also reduces the efficiency of the radio frequency (RF) power amplifier. In this paper, we present a data position permutation (DPP) method, which is based on a selected mapping (SLM) scheme, for reducing the PAPR in OFDM systems. The candidate signal on each branch of the SLM scheme is generated by permuting the position and rotating the phase of the original data. In addition, a modified DPP method with lower bit error rate (BER) is proposed. The simulation results show that the proposed method provides better performance with regard to complexity, spectrum efficiency, and BER as compared to that of the SLM‐based dummy sequence insertion (SLM‐DSI) method. Copyright © 2008 John Wiley & Sons, Ltd.