On the Optimization of Iterative Clipping and Filtering for PAPR Reduction in OFDM Systems

Orthogonal frequency division multiplexing (OFDM) offers spectral efficiency advantage, however, it is limited by peak-to-average power (PAPR) problem. The PAPR can be reduced using iterative clipping and filtering (ICF) scheme but requires that the same signals are iteratively clipped with a fixed clipping threshold at different clipping iterations. This method warrants that fast-Fourier transform (FFT)/inverse FFT (IFFT) blocks must be driven in the order of iterations many times to attain a desired PAPR threshold which expends the system power and expands the processing time. Using a second-order cone program, the number of iterations required to attain the desired PAPR threshold was reduced. This optimized ICF (OICF) was later simplified using Lagrange multiplier (LM). In this paper, we apply an adaptive clipping threshold to the LM scheme to improve the performance of the simplified OICF (SOICF). Our results show significant reduction of the PAPR problem compared with the earlier SOICF scheme albeit with some degradation in the bit error ratio (BER) performance that can be under 1.0 dB depending on the chosen clipping threshold. In addition, we also illustrate the results of the performances and the theoretical relationships between the error vector magnitude (EVM) and PAPR, between clipping ratio (CR) and EVM, and lastly the inter-dependencies of EVM, PAPR, the number of OFDM subcarriers, and the CR

Evaluasi Penerapan Algoritma Neural Network Sebagai Teknik Reduksi PAPR Pada Sistem OFDM

Pada makalah ini dilakukan evaluasi kinerja algoritma Neural Network sebagai teknik reduksi sistem OFDM.  Hasil simulasi untuk sinyal OFDM dengan jumlah subcarrier sebanyak 64 dan modulasi 16 QAM menunjukkan penerapan algorima NN menghasilkan penurunan nilai PAPR sekitar 5,6 dB dari PAPR sinyal OFDM tanpa reduksi. Juga dibandingkan dengan teknik reduksi PAPR metode Iterative Clipping and Filtering, (ICF), Selective Mapping (SLM) dan Partial Transmit Sequence (PTS). Dari kurva CCDF juga ditunjukkan bahwa metode NN menghasilkan kinerja yang lebih baik dibanding metode digabungkan dengan teknik Iterative Clipping and Filtering, (ICF), Selective Mapping (SLM) dan Partial Transmit Sequence (PTS). Evaluasi di sisi penerima dengan pengamatan nilai bit error rate, penerapan algoritma NN memiliki kinerja yang terbai

Reducción del PAPR mediante técnicas de Clipping y Peak Windowing en sistemas multiportadoras FBMC

A comparison of the classical clipping technique with the peak window technique for hamming, hanning and kaiser windows to reduce PAPR in an FBMC signal over an AWGN channel is presented. The techniques are probabilistically analyzed by showing that the classic clipping technique reduces PAPR more than the kaiser peak windowing technique for a length of 4 which is the one that reduces the most among the peak window techniques. So, their performances through BER were evaluated over an AWGN channel. Showing the classic clipping technique has better performance than peak windowing techniques.Una comparación de la técnica de recorte clásico con la técnica de ventana pico para las ventanas de hamming, hanning y kaiser para reducir el PAPR en una señal FBMC sobre un canal AWGN es presentada. Las técnicas son analizadas probabilísticamente mostrando que la técnica de recorte clásico reduce el PAPR más que la técnica de ventana pico kaiser para una longitud de 4 que es la que más reduce de las técnicas de ventana pico. Entonces, sus desempeños mediante el BER fueron evaluados sobre un canal AWGN, mostrando la técnica de recorte clásico tiene un mejor desempeño que las técnicas de ventana pico

A Comparison of ICF and Companding for Impulsive Noise Mitigation in Powerline Communication Systems

In future smart cities, smart grid technologies which are usually enabled by Powerline Communication (PLC) techniques are required. However, data transmission over powerline channel traverses a non-Gaussian media due to the presence of Impulsive Noise (IN) operating at the frequencies of PLC system which can be deployed using the IEEE 1901, that uses Orthogonal Frequency Division Multiplexing (OFDM). These OFDM signals have asymmetric amplitude distribution, which makes it difficult to identify and mitigate the IN presence. Converting the amplitude distribution to a uniform distribution can enhance the ability to mitigate IN when nonlinear IN mitigation techniques such as blanking is applied. In this study, we apply Iterative Clipping and Filtering (ICF) and companding schemes which are Peak-to-Average Power Ratio (PAPR) reduction techniques to enable symmetric amplitude distribution of the OFDM signals. With an optimization search for the optimal blanking amplitude for the two PAPR reduction schemes. Results show that companding scheme achieves 4dB gain in terms of received signal-to-noise ratio better than ICF after the blanking was used to remove the IN

Peak-to-Average Power Ratio Reduction of DOCSIS 3.1 Downstream Signals

Tone reservation (TR) is an attractive and widely used method for peak-to-average power ratio (PAPR) reduction of orthogonal frequency division multiplexing (OFDM) signals, where both transmitter and receiver agree upon a number of subcarriers or tones to be reserved to generate a peak canceling signal that can reduce the peak power of the transmitted signals. The tones are selected to be mutually exclusive with the tones used for data transmission, which allows the receiver to extract the data symbols without distortions. This thesis presents two novel PAPR reduction algorithms for OFDM signals based on the TR principle, which do not distort the transmitted signals. The first proposed algorithm is performed in the time domain, whereas the second algorithm is a new clipping-and-filtering method. Both algorithms consist of two stages. The first stage, which is done off-line, creates a set of canceling signals based on the settings of the OFDM system. In particular, these signals are constructed to cancel signals at different levels of maximum instantaneous power that are above a predefined threshold. The second stage, which is online and iterative, reduces the signal peaks by using the canceling signals constructed in the first stage. The precalculated canceling signals can be updated when different tone sets are selected for data transmission, accommodating many practical applications. Simulation results show that the proposed algorithms achieve slightly better PAPR reduction performance than the conventional algorithms. Moreover, such performance is achieved with much lower computational complexity in terms of numbers of multiplications and additions per iteration. Among the two proposed algorithms, the time-domain algorithm gives the best peak reduction performance but the clipping-and-filtering algorithm requires considerably less number of multiplications per iteration and can be efficiently implemented using the fast Fourier transform (FFT)/inverse fast Fourier transform (IFFT) structure

Peak to average power ratio reduction and error control in MIMO-OFDM HARQ System

Currently, multiple-input multiple-output orthogonal frequency division multiplexing (MIMOOFDM) systems underlie crucial wireless communication systems such as commercial 4G and 5G networks, tactical communication, and interoperable Public Safety communications. However, one drawback arising from OFDM modulation is its resulting high peak-to-average power ratio (PAPR). This problem increases with an increase in the number of transmit antennas. In this work, a new hybrid PAPR reduction technique is proposed for space-time block coding (STBC) MIMO-OFDM systems that combine the coding capabilities to PAPR reduction methods, while leveraging the new degree of freedom provided by the presence of multiple transmit chairs (MIMO). In the first part, we presented an extensive literature review of PAPR reduction techniques for OFDM and MIMO-OFDM systems. The work developed a PAPR reduction technique taxonomy, and analyzed the motivations for reducing the PAPR in current communication systems, emphasizing two important motivations such as power savings and coverage gain. In the tax onomy presented here, we include a new category, namely, hybrid techniques. Additionally, we drew a conclusion regarding the importance of hybrid PAPR reduction techniques. In the second part, we studied the effect of forward error correction (FEC) codes on the PAPR for the coded OFDM (COFDM) system. We simulated and compared the CCDF of the PAPR and its relationship with the autocorrelation of the COFDM signal before the inverse fast Fourier transform (IFFT) block. This allows to conclude on the main characteristics of the codes that generate high peaks in the COFDM signal, and therefore, the optimal parameters in order to reduce PAPR. We emphasize our study in FEC codes as linear block codes, and convolutional codes. Finally, we proposed a new hybrid PAPR reduction technique for an STBC MIMO-OFDM system, in which the convolutional code is optimized to avoid PAPR degradation, which also combines successive suboptimal cross-antenna rotation and inversion (SS-CARI) and iterative modified companding and filtering schemes. The new method permits to obtain a significant net gain for the system, i.e., considerable PAPR reduction, bit error rate (BER) gain as compared to the basic MIMO-OFDM system, low complexity, and reduced spectral splatter. The new hybrid technique was extensively evaluated by simulation, and the complementary cumulative distribution function (CCDF), the BER, and the power spectral density (PSD) were compared to the original STBC MIMO-OFDM signal