PAPR reduction in blind MIMO OFDM systems based on independent component analysis

Independent component analysis for multiple-input multiple-output wireless communication systems

Orthogonal frequency division multiplexing (OFDM) signals have a generic problem of high peak to average power ratio (PAPR) which is defined as the ratio of the peak power to the average power of the OFDM signal. The drawback of the high PAPR is that the dynamic range of the power amplifiers (PA) & digital-to-analog (D/A) converters required during the transmission and reception of the signal is higher. As a result, the total cost of the transceiver increases, with reduced efficiency. This paper includes an idea of the PAPR constraint, along with the implementation and analysis of some specific algorithms for PAPR reduction of the OFDM signals. All the PAPR reduction algorithms are implemented and tested in the OFDM transceiver designed using Matlab. Analyzing some specific algorithms, we propose a novel algorithm by combining the subcarrier phase adjustment and linear combination of the time domain OFDM signals. Simulation results for a OFDM system employing Quadrature Amplitude Shift Keying (QASK) symbols and Quadrature Amplitude Modulation (QAM) can achieve a PAPR reduction of 5 dB.

In this paper, we propose a new PAPR reduction by using a partial transmit sequences (PTS) method with coded side information (SI) technique. These methods are used in an orthogonal frequency division multiplexing (OFDM) system. The OFDM employs orthogonal sub-carriers for data modulation. These sub-carriers unexpectedly present a large peak to average power ratio (PAPR) in some cases. In order to reduce PAPR, the sequence of input data is partitioned into disjoint sub-block of PTS. If number of sub-block increases, high efficiency of PAPR reduction can be obtained. However, a quite large calculation cost must be demanded and thus it is impossible to obtain the optimum PTS. In the proposed method, we introduce a coded side information technique assuming the pseudo-optimum condition into the PTS. The total calculation cost becomes drastically reduced and side information bits for recovering original data in demodulation. In simulation results, the proposed method demonstrated the improvement of PAPR and bit error rate (BER) performance.

The artificial bee colony-based SLM (ABC-SLM) scheme, which is a novel PAPR reduction scheme, has been proposed to reduce the peak to average power ratio (PAPR) in orthogonal frequency division multiplexing (OFDM) systems. High PAPR can degrade the efficiency of high-power amplifier and is one of the major disadvantages of OFDM systems. This paper proposes a modified ABC-SLM scheme to further improve the PAPR reduction performance of ABC-SLM scheme. The proposed method, called GA-ABC-SLM, is combined the gene algorithm (GA) with the artificial bee colony-based SLM scheme. The simulation results show that the GA-ABC-SLM scheme has better PAPR reduction performance than the ABC-SLM scheme.

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.

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.

In this paper, we propose a low-complexity peak-to-average power ratio (PAPR) reduction scheme that combines both multi-band (MB)-Hadamard precoding and clipping for the optical orthogonal frequency division multiplexing (OFDM) systems. Approximations of PAPR distribution for baseband OFDM signals are analyzed and the effective signal-to-noise ratio (SNR) of the whole transmission link considering both the clipping and quantization noise are presented. After that, the MB-Hadamard precoding is adopted to compresses the peak signals, minimizing the contaminating influence of signal distortions in subsequent clipping operations. In addition, the received SNRs and bit error rate (BER) are calculated theoretically for each split sub-band. The 50-m step-index polymer optical fiber (POF) transmission is adopted as a special case to both evaluate the system performance and then compare the proposed scheme with other well-known PAPR reduction techniques. With this scheme, the PAPR is reduced effectively and the system’s BER performance is improved significantly. The results show that the proposed scheme with appropriate number of sub-bands precoding provides favorable trade-offs among PAPR reduction, power spectral density, transmission rate, BER, and computational complexity, which demonstrates its feasibility and validity.

Partial transmit sequence (PTS) scheme is one of the efficacious tool for lessening peak-to-average power ratio (PAPR) in orthogonal frequency division multiplexing (OFDM) system. However, computational cost for the optimum phase factors searches of PTS scheme entails huge computational requirements and limits its applicability to practical applications especially for high-speed data transmissions. This study proposes a PAPR reduction method with a low computational complexity based on a combination of cuckoo search optimization algorithm with PTS scheme in OFDM system. In terms of PAPR and computational cost reductions, the performance of the cuckoo-PTS scheme is comparatively investigated by performing a set of simulations with different PTS schemes.

In this paper, a peak-to-average power ratio (PAPR) reduction scheme without side information (SI) is propossed. Cyclic-selective mapping (cyclic-SLM) has been applied to reduce the PAPR of a transmit orthogonal frequency division multiplexing (OFDM) signal. The cyclic-SLM generates a signal candidate by combining an original signal and its cyclic shifted signal. The Cyclic SLM requires side information regarding the cyclic shift to recover the signal while it will reduce the throughput of a wireless OFDM system. The propossed scheme applies delayed correlation based estimation to omit the transmision of the SI. In the receiver side, the amount of the cyclic shift is estimated with exploiting the correlation between a guard interval sequence and a received signal. Numerical results show that the cyclic-SLM with the delayed correlation (DC) provides significant PAPR reduction while it realizes the accuracy of the shift estimation close to 100% at E_b/N_0 of 8 dB. It also achieves the PAPR that is equivalent to the conventional SLM and the bit error rate degradation is slightly different from that with perfect shift estimation.

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.

OFDM (Orthogonal Frequency Division Multiplexing) 시스템에서 SLM (Selected Mapping)은 전송신호의 왜곡 없이 PAPR (Peak-to-Average Power Ratio)을 효율적으로 줄일 수 있는 기법이다. 하지만, 충분한 후보 OFDM 신호를 생성하기 위해서는 많은 양의 IFFT (Inverse Fast Fourier Transform) 연산을 필요로 하고, 이는 SLM 기법을 매우 복잡하게 만든다. 따라서 본 논문에서는 첫 번째 후보 OFDM 신호를 변환하여 나머지 IFFT 연산들을 대체하는 새로운 SLM 기법을 제안한다. 제안된 기법은 기존의 SLM 기법과 비교하여 거의 같은 PAPR 저감 성능을 보임과 동시에 계산 복잡도는 크게 감소 시킬 수 있다. SLM (Selected Mapping) is an efficient PAPR (Peak-to-Average Power Ratio) reduction scheme without transmitted signal distortion in OFDM (Orthogonal Frequency Division Multiplexing) systems. However, enormous IFFTs (Inverse Fast Fourier Transforms) are needed to generate sufficient candidate OFDM signals, which cause the SLM to become quite complex. In this paper, we propose a new SLM scheme that replaces the IFFT operations with a conversion of the first candidate OFDM signal. The proposed scheme significantly reduces computational complexity, while it shows almost the same PAPR performance as the conventional SLM scheme.

This paper proposes a partial transmit sequence (PTS) scheme with applying a stochastic optimization technique for peak-to-average power ratio (PAPR) reduction in the orthogonal frequency division multiplexing (OFDM) system. PTS technique combining can improve the PAPR statistics of an OFDM signals, but the considerable computational complexity for the required search through a high-dimensional vector space is a potential problem for implementation in the practical systems. Differential evolution (DE) is an efficient and powerful population-based stochastic search technique for solving optimization problems over continuous space, which has been widely applied in many scientific and engineering fields. Thus, to reduce the complexity for searching phase weight vector and to improve the PAPR statistics, we introduce the DE, an effective algorithm that solves various combinatorial optimization problems, to search the optimal phase weight factors. The simulation results show that the proposed DE-based PTS obtains the excellent PAPR performance with a low computational complexity.

High peak-to-average power ratio (PAPR) is one of the major drawbacks of orthogonal frequency division multiplexing (OFDM). In [8] a low-complexity probabilistic scheme to reduce PAPR in OFDM, called erasure pattern selection (EPS), was proposed. The EPS scheme described in [8] requires the transmission of side information with proper coding. In this paper we address waveform design for OFDM transmission and investigate a method that avoids transmission of side information. Simulation results show that the probability of incorrect detection of the selected erasure pattern is smaller than 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> for SNR larger than 6 dB. This means that only 1 in 1000 symbols have to be retransmitted. Also, EPS provide a reduction in PAPR of about 1.5 dB.

This paper proposes an enhancement to a previously reported adaptive peak-to-average power ratio (PAPR) reduction method based on clipping and filtering (CF) for eigenmode multiple-input multiple-output (MIMO) - orthogonal frequency division multiplexing (OFDM) signals. We enhance the method to accommodate the case with adaptive modulation and channel coding (AMC). Since the PAPR reduction process degrades the signal-to-interference and noise power ratio (SINR), the AMC should take into account this degradation before PAPR reduction to select accurately the modulation scheme and coding rate (MCS) for each spatial stream. We use a lookup-table-based prediction of SINR after PAPR reduction, in which the interference caused by the PAPR reduction is obtained as a function of the stream index, frequency block index, clipping threshold for PAPR reduction, and input backoff (IBO) of the power amplifier. Simulation results show that the proposed PAPR reduction method increases the average throughput compared to the conventional CF method for a given adjacent channel leakage power ratio (ACLR) even when we assume AMC.

High peak to average power ratio (PAPR) of the transmitted signal is a major drawback of multicarrier transmission such as orthogonal frequency division multiplexing (OFDM). This work considers the problem of PAPR reduction in a multi-symbol encapsulated OFDM (MSE-OFDM) system. This paper employs the discrete cosine transform (DCT) to the data sequence. Not only can this method have the same bandwidth efficiency as that of the CP-reduced MSE-OFDM system, but also reduce the PAPR in the MSE-OFDM. Simulation shows that the proposed scheme can significantly reduce the PAPR in MSE OFDM system without increasing the symbol error rate.