61 research outputs found

    A Simplified Scheme of Estimation and Cancellation of Companding Noise for Companded Multicarrier Transmission Systems

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    Nonlinear companding transform is an efficient method to reduce the high peak-to-average power ratio (PAPR) of multicarrier transmission systems. However, the introduced companding noise greatly degrades the bit-error-rate (BER) performance of the companded multicarrier systems. In this paper, a simplified but effective scheme of estimation and cancellation of companding noise for the companded multicarrier transmission system is proposed. By expressing the companded signals as the summation of original signals added with a companding noise component, and subtracting this estimated companding noise from the received signals, the BER performance of the overall system can be significantly improved. Simulation results well confirm the great advantages of the proposed scheme over other conventional decompanding or no decompanding schemes under various situations

    PAPR Reduction in OFDM System by using Nonlinear Companding Technique

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    Non linear companding technique is proposed to reduce the high peak to average power ratio (PAPR) of orthogonal frequency division multiplexing system. Use of companding for peak - to - average - power ratio (PAPR) control is explored for a link involving a non - linear transmit power amplifier with orthogonal frequency division multiplexing (OFDM). This paper analyses the improvement in bit error rate (BER) and overall system performance by employing non linear companding technique for PAPR reduction in digital video broadcasting (DVB - T) system

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

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    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

    Multicarrier modulation with variable peak‐to‐average power ratio using partial fast Fourier transform

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    Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/166180/1/cmu2bf01398.pd

    A Novel PAPR Reduction in Filter Bank Multi-Carrier (FBMC) with Offset Quadrature Amplitude Modulation (OQAM) Based VLC Systems

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    The peak to average power ratio (PAPR) is one of the major problem with multicarrier-based systems. Due to its improved spectral efficiency and decreased PAPR, Filter Bank Multicarrier (FBMC) has recently become an effective alternative to the orthogonal multiplexing division (OFDM). For filter bank multicarrier communication/offset quadrature amplitude modulation-Visible light communication (FBMC/OQAM-VLC) systems is proposed a PAPR reduction technique. The suggested approach overlaps the proposed FBMC/OQAM-based VLC data signal with the existing signals. Non-redundant signals and data signals do not overlap in the frequency domain because data signals are scattered on odd subcarriers whereas built signals use even subcarriers. To reduce the effects of large-amplitude signal reduction, the suggested technique converts negative signals into positive signals rather than clipping them off as in conventional FBMC-based VLC systems. The PAPR reduction and bit error rate (BER) are realized using a scaling factor in the transformed signals. Complementary cumulative distribution function(CCDF) and BER are used to calculate the performance of the proposed approach. The presented study found that FBMC/OQAM-VLC systems to achieve a good trade-off between PAPR reduction and BER

    Peak To Average Power Ratio Reduction In Wireless Orthogonal Frequency Division Multiplexing

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    Orthogonal Frequency Division Multiplexing (OFDM) offers an attractive multicarrier technique with high spectral efficiency, simple implementation and robustness against multipath fading. A trend of OFDM development is to increase the number of subcarriers to enhance efficiency. However, when the number of subcarriers increases, certain time domain OFDM coefficients are likely to acquire excessively large magnitudes. As such, the OFDM baseband waveform is susceptible to high PAPR value and may suffer from non linear distortion at subsequent power amplifier stage. This high PAPR can limit the transmitter power efficiency, cause spectral spreading and reduce the bit-error-rate (BER) performance. To alleviate these potential performance problems, two novel computationally efficient and low cost PAPR reduction methods are proposed. The first method, called DCT-OFDM Method, seeks to apply alternative structure for transmitting the high speed data in the OFDM system. The character of the DCT energy focused is made use of in the frequency domain and it helps to reduce the PAPR engendered by IFFT at the transmitter statistically, avoiding the nonlinear distortion in OFDM systems due to great change of PAPR. It is mathematically verified that this method is potent to reduce PAPR. Simulation results show that about 2.2 dB reduction in PAPR value is achieved by this technique. Statistical Redistribution Method (SRM) which makes use of a non linear companding operation is selected and applied on the OFDM outputs signals has been used as a combination with Selected Mapping Method (SLM). The proposed scheme utilizes Selected Mapping (SLM) followed by the companding SRM technique to further reduce the PAPR of the OFDM signal. Simulation results indicate that about 5 dB reduction in PAPR is achieved compared with the conventional SLM algorithm

    An Overview of PAPR Reduction Techniques for an MC-CDMA System

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    Abstract-MC-CDMA is the most promising technique for high bit rate and high capacity transmission in wireless communication. One of the challenging issues of MC-CDMA system is very high PAPR due to large number of sub-carriers which reduces the system efficiency. This paper describes the various PAPR reduction techniques for MC-CDMA system. Criterion for the selection of PAPR reduction technique and also the comparison between the reduction techniques has been discussed
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