SLM 기반의 OFDM 통신 시스템을 위한 계산 복잡도 저감 기법

There have been a set of conversion matrices proposed recently by Wang and Ouyang to simplify the inverse fast Fourier transform (IFFT) computation involved in the selected mapping (SLM) scheme for reduction of the peak-to-average power ratio (PAPR) in orthogonal frequency division multiplexing (OFDM) systems. As compared to the conventional SLM scheme, the modified approach achieves close PAPR reduction with much lower complexity but degraded bit error rate (BER) performance. In this paper, we propose a new set of conversion matrices for the SLM scheme such that the complexity can be reduced without sacrificing the BER performance. It is shown that the improved SLM method has better BER performance and lower complexity than the previous work by Wang and Ouyang, at the cost of a slight PAPR reduction loss.

High Peak to Average Power Ratio (PAPR) in the transmitted signal is still a very important challenge in Orthogonal Frequency Division Multiplexing (OFDM) systems. In this paper, we present a new Zadoff-Chu matrix Transform (ZCT) precoded Selected Mapping (SLM) based OFDM (SLM-OFDM) system for PAPR reduction. The proposed system is based on precoding the constellation symbols with ZCT precoder after the multiplication of phase rotation factor and before the Inverse Fast Fourier Transform (IFFT) in SLM-OFDM Systems. At the clipping probability of 10−3, simulation results show that our proposed system can reduce the PAPR up to 5.0 dB with N=64 (System subcarriers) and V=16 (Dissimilar phase sequences) for QPSK modulation. Additionally, ZCT based SLM-OFDM systems also take advantage of frequency variations of the communication channel and can also offer substantial performance gain in fading multipath channels.

Based on superposition of signals in the time domain, we propose a new low-complexity scheme for the reduction of the peak-to-average power ratio (PAPR) in orthogonal frequency division multiplexing (OFDM) systems. The proposed scheme first generates signal candidates by combining an OFDM signal and its cyclically delayed versions with different delays and phases, and then selects the candidate signal with minimum PAPR. It is shown that the complexity of the proposed scheme is significantly lower than that of the selective mapping (SLM) at the cost of some degradation in the bit error rate (BER) performance and, at similar PAPR and coded BER performance, is lower than that of the low-complexity SLM proposed recently.

Selected mapping (SLM) is an effective method for addressing high peak-to-average power ratio (PAPR) issues in orthogonal frequency division multiplexing (OFDM) systems. However, the standard SLM approach introduces additional data decoding challenges in the form of side information (SI) transmission and estimation. In general, SI transmission reduces data throughput and SI estimation normally involves computationally complex procedures, which increase design costs. To eliminate the need for both SI transmission and SI estimation, this paper presents an investigation into the PAPR reduction and BER performance of a new technique based on a modified SLM approach. It is shown that the proposed method simplifies data decoding through SI cancellation without SI transmission. Results show that the proposed method produces similar PAPR reduction performance and BER performance as standard SLM based OFDM system, which presumes perfect SI estimation, within a frequency non-selective (flat) fading channel.

Orthogonal Frequency Division Multiplexing (OFDM) is one of the attractive data transmission technologies in recent years because of its high data processing rate and its capable to combat inter-symbol interference (ISI) that come from multiple paths fading. Also, OFDM is the standard of new generation wireless communication systems. However, the high Peak-to-Average Power Ratio(PAPR) can influence the system performance through significantly degrading its signal quality in the nonlinear channel. Researchers propose several PAPR reduction algorithms, such as Clipping, Partial Transmit Sequences (PTS), selective mapping (SLM). In this paper we propose a novel turbo scheme combining PTS with adaptive tone reservation (TR) to reduce PAPR in OFDM systems. Conducted simulations show that the performance of PAPR with TR-enhanced Turbo PTS are superior to pervious works.

In this paper, a linear moving average recursive filtering technique is proposed to reduce the peak-to-average power ratio (PAR) of orthogonal frequency division multiplexing (OFDM) signals. The proposed low complexity technique is analyzed in an oversampled OFDM system and a simple distribution approximation of the oversampled and linearly filtered OFDM signals is also proposed. Corresponding time domain linear equalizers are developed to recover originally transmitted data symbols. Through extensive computer simulations, effects of the new filtering technique on the oversampled OFDM peak-to-average power ratio (PAR), power spectral density (PSD) and corresponding linear equalizers on the frequency selective Rayleigh fading channel transmission symbol-error-rate (SER) performance are investigated. The newly proposed recursive filtering scheme results in attractive PAR reduction, requires no extra fast Fourier transform/inverse fast Fourier transform (FFT/IFFT) operations, refrains from transmitting any side information, and reduces out-of-band radiation. Also, corresponding linear receivers are shown to perform very close to their frequency domain counterparts.

Orthogonal frequency division multiplexing (OFDM) system has high spectral efficiency and immunity to frequency selective fading channel. So, it has been widely used in modern wireless communication systems. However, the major drawback of OFDM system is the high peak-to-average power ratio (PAPR) of the transmitted signal for large number of subcarriers. Selected mapping (SLM) is one of the most well-known technique to reduce the PAPR in OFDM system, since it can achieve a good PAPR reduction without signal distortion. Moreover, SLM technique can be used with wavelet-OFDM (WOFDM) system to enhance the PAPR performance, while maintaining most of the advantages of the conventional OFDM system. In this paper, an effective PAPR reduction technique using SLM-WOFDM based on particle swarm optimization (PSO) algorithm is proposed. PSO is applied to SLM-OFDM and SLM-WOFDM systems for searching the optimum phase rotation factors. The systems evaluation shows that the proposed PSO based SLM-WOFDM system provides better PAPR reduction compared to PSO based SLM-OFDM, SLM-WOFDM, and conventional SLM-OFDM systems.

One of the widely adopted multicarrier modulation technique in wireless communication system is Orthogonal Frequency Division Multiplexing (OFDM), because of its enhanced robustness against channel dispersion. However, Inter Carrier Interference (ICI) caused by time varying wireless channel and Peak to Average Power Ratio (PAPR) due to the presence of a large number of subcarriers with varying amplitude are the critical issues faced in OFDM. One of the efficient ICI self-cancellation scheme is correlative precoder but it introduces increased PAPR. To overcome this shortcoming a new form of circulantly precoded OFDM system is implemented to enhance ICI reduce and also employed with Selective Mapping (SLM) which is effective in PAPR reduction and uncomplicated. BER performance of correlative and circulantly precoded OFDM system is evaluated for LMMSE and OLMMSE equalizers. Simulation results show that circulantly precoded OFDM with SLM can achieve jointly better ICI self cancellation and PAPR reduction than correlative precoding technique over time varying channel.

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 distribution as that of the output signals of the conventional orthogonal frequency division multiplexing (OFDM) system. The integration of IDRG with PTS technique reduces the overall complexity of the OFDM system. Compared to the conventional PTS which requires several inverse fast Fourier transform (IFFT) operations, the proposed IDRG–PTS scheme requires only half as many IFFT operations with comparable PAPR performance. Simulation results have been examined with 16 quadrate amplitude modulation OFDM signals.

Orthogonal Frequency Division Multiplexing (OFDM) is an encoding method that are hugely utilized in wireless communication due to its high number of advantages such as tolerance for multipath delay spread, frequency selective fading channels immune and also power efficiency. The bad side of this method is it has high Peak Average Power Ratio (PAPR) that will generate nonlinear distortions and severe power penalty. In this research, Selective Mapping (SLM) method is proposed to solve the problem of high PAPR but from previous researches, it could be seen that in SLM, the search complexity increases as the number of phase sequence increase. To solve this issue, Firefly Algorithm (FA) is applied to optimize the function of SLM. The modulation method used is Quadrature Phase Shift Keying (QPSK). By the end of the process, CCDF and BER plots are computed. The performance of PAPR reduction in OFDM system are analyzed by different number of subcarriers, phase sequences, randomization parameters and iterations using CCDF graphs. The performance of OFDM channel through AWGN channel is studied with different number of subcarriers. By using SLM method only, the PAPR values manage to be reduced by 0.4–3 dB but with FA-SLM algorithm, the PAPR values can be reduced by 5–9.5 dB. With these results, it is concluded that the combination of SLM with FA can help to improve computational complexity in SLM and eventually reduce PAPR value in OFDM system.

SummaryIn wireless telecommunication, one of the modulation approaches used is the orthogonal frequency division multiplexing (OFDM). Moreover, the high peak‐to‐average power ratio (PAPR) is the one notorious demerit in OFDM systems. Hence, the high power amplifier (HPA) is used in its linear region. Otherwise, the bit error rate (BER) will be increased. Several approaches are proposed in the wireless communications for reducing the PAPR issue. In this paper, we propose a hybrid Discrete Hartley Matrix Transform (DHMT) precoding using both selected mapping (SLM) and partial transmit sequence (PTS) PAPR reduction strategies. For the multicarrier modulation process, instead of Inverse Fast Fourier transform (IFFT) operation, the DHMT operation is used because of its low computational complexity. Based on multi‐chaotic, the time‐frequency domain encryption (TFDE) approach is adopted for physical layer security to confirm the security in data transmission. For enhancing the physical layer security, the proposed encryption system generates chaotic sequences based on Logistic maps and Lozi in the frequency and time domains together. In this study, the implementation of the DHMT‐based OFDM system is processed to reduce the maximum PAPR. Implementation is performed on the MATLAB platform, and the performances are calculated using complementary cumulative distribution function (CCDF), BER regards to signal‐to‐noise ratio (SNR), and the outputs are compared based on the computation time. However, compared with the existing models, the proposed model produced better PAPR minimization regarding SNR.

This paper introduces a peak-to-average power ratio (PAPR) reduction scheme adopting a single high-order adaptive all-pass filter (AAPF). The phase rotation of time-domain orthogonal frequency-division multiplexing (OFDM) symbol, corresponding to reduced PAPR, is obtained by the single AAPF. Comparison of computational complexity and PAPR reduction performance with the selected mapping (SLM) scheme, the static all-pass filter bank scheme, and the low-complexity (LC) SLM scheme suggests that the computational complexity of the AAPF scheme is comparable with that of the LC-SLM scheme and that the PAPR reduction performance is competitive to the SLM scheme. Simulation results for bit error rate (BER) performance show that the smooth phase transition caused by the AAPF enables data recovery without side information.

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.

The major issue in orthogonal frequency division multiplexing (OFDM) system is a high peak-to-average power ratio (PAPR) of transmitting signal. Selective mapping (SLM) is the promising technique to reduce PAPR in OFDM system. However, it suffers from high computational complexity. In our proposed method, to achieve low computational complexity, the input data sequences are partitioned into two sub blocks in such a way that the candidate signals are generated by performing circular convolution for the first sub block and by conventional SLM in the second sub block. The candidate signals of modified SLM are obtained by combining two sub block candidate signals. The proposed method reduces PAPR marginally along with reduction in computational complexity. To further reduce PAPR, different phase sequences namely Riemann, New Riemann and chaotic sequences are used in C-SLM. The Matlab simulation shows that, the modified SLM with new Riemann sequence results in high PAPR reduction than other phase sequences. In addition, it provides significant reduction computational complexity compared to C-SLM.

Selected mapping (SLM) is a well-known technique to reduce the peak-to-average power ratio (PAPR) in orthogonal frequency division multiplexing (OFDM). SLM generally requires the side information for each OFDM symbol, which leads to decrease the transmitting efficiency. In addition, false side information detection degrades the bit error rate performance significantly. In this paper, we propose a novel SLM scheme without any side information by devising a phase rotation and simple scrambler detection in the receiver. Computer simulation results show that the proposed scheme achieves excellent performances in terms of both PAPR reduction and BER.