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

Adjacent Partitioning Based MIMO-OFDM System with Partial Transmit Sequence for PAPR Reduction

The multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) transmission approach has been chosen to be a standard of fourth-generation (4G) wireless communication systems, but it has to cope with the main disadvantages and challenges of OFDM-based techniques, including the high peak-to-average power ratio (PAPR). Peak to average power ratio (PAPR) being a predictable random variable in multicarrier system and it can be minimized by different techniques. Complementary cumulative distribution function (CCDF) is used to describe the PAPR appropriately. Partial transmit sequence (PTS) is an attractive distortion less peak-to-average power ratio (PAPR) reduction technique for orthogonal frequency division multiplexing (OFDM) system. In this paper the performance of one of scrambling technique called partial transmit sequence (PTS) in MIMO-OFDM system and adjacent partitioning(one of the partitioning technique) in MIMO-OFDM system with PTS are analyzed based on the characteristics of CCDF DOI: 10.17762/ijritcc2321-8169.150514

Pembuatan Model Hybrid 2 Teknik Reduksi Peak-to-average Power Ratio Partial Transmit Sequence Dan Clipping Filtering Pada Sistem Mimo-ofdm

Sistem MIMO digunakan dalam sistem komunikasi nirkabel modern untuk memenuhi tuntutan kecepatan transmisi data yang tinggi untuk berbagai aplikasi dan layanan namun sistem MIMO-OFDM mempunyai kelemahan nilai PAPR (Peak to Average Power Ratio) yang tinggi dan membuat HPA (High Power Amplifier) bekerja pada daerah non-linier. Sehingga perlu dilakukan reduksi dengan teknik reduksi PAPR. dalam Penelitian ini dilakukan analisis reduksi PAPR pada sistem MIMO-OFDM menggunakan teknik hybrid Improved Partial Transmits Sequence dan Simplified Clipping Filtering. Analisis dilakukan dengan mengamati kinerja penggunaan teknik reduksi PAPR dan penggunaan tanpa teknik reduksi PAPR. Hasil simulasi menunjukkan pada probabilitas 1x10-5, hasil kinerja tanpa teknik reduksi dibutuhkan level threshold PAPR0 sebesar ± 12 dB, sedangkan ketika menggunakan teknik reduksi hybrid Improved PTS dan Simplified CF dibutuhkan level threshold PAPR0 rata-rata ± 6 dB dan membandingkan kinerja teknik reduksi Hybrid Improved PTS - Simplified CF dengan nilai Clipping ratio 1,4 dan 1,6. Maka kinerja reduksi PAPR terbaik adalah dengan menggunakan teknik reduksi hybrid Improved PTS dan Simplified CF dengan Clipping ratio 1,4 karena mampu menyuguhkan selisih nilai reduksi sebesar ± 5,7 dB daripada tanpa menggunakan teknik reduksi. dan penggunaan nilai Clipping Ratio yang semakin rendah menghasilkan nilai PAPR yang juga semakin rendah, karena Amplitudo maksimum semakin kecil

A hybrid-structure offset-QAM filter-bank multi-carrier MIMO system

Offset quadrature amplitude modulation (OQAM) filter-bank multi-carrier (FBMC), has great potential for boosting the spectral efficiency (SE) and energy efficiency (EE) of future communication systems. This is due to its superior spectral localization, CP-less transmission and relaxed synchronization requirements. Our research focuses on three main OQAM/FBMC research problems: the computational complexity reduction taking equalization into consideration, its integration with multiple-input multiple-output (MIMO) and its high peak-to-average power ratio (PAPR). OQAM/FBMC systems are mainly implemented either using frequency spreading (FS) or polyphase network (PPN) techniques. The PPN technique is generally less complex, but when using frequency domain equalization (FDE) to equalize multipath channel effects at the receiver, there is a computational complexity overhead when using PPN. A novel hybrid-structure OQAM/FBMC MIMO space-frequency block coding (SFBC) system is proposed, to achieve the lowest possible overall complexity in conjunction with FDE at the receiver in frequency selective Rayleigh fading channel. The Alamouti SFBC block coding is performed on the complex-orthogonal signal before OQAM processing, which resolves the problems of intrinsic interference when integrating OQAM/FBMC with MIMO. In better multipath channel conditions with a line-of-sight (LOS) path, a zero-forcing (ZF) time domain equalization (TDE) is exploited to further reduce the computational complexity with comparable performance bit-error-rate (BER). On the other hand, to tackle the high PAPR problem of the OQAM/FBMC system in the uplink, a novel single carrier (SC)-OQAM/FBMC MIMO system is proposed. The system uses DFT-spreading applied to the OQAM modulated signal, along with interleaved subcarrier mapping to significantly reduce the PAPR and enhance the BER performance over Rayleigh fading channels, with relatively low additional computational complexity compared to the original complexity of the FBMC system and compared to other FBMC PAPR reduction techniques.The proposed hybrid-structure system has shown significant BER performance in frequency-selective Rayleigh fading channels compared to OFDM, with significantly lower OOB emissions in addition to the enhanced SE due to the absence of CP. In mild multipath fading channels with a LOS component, the PPN OQAM/FBMC MIMO using TDE has a comparable BER performance with significantly less computational complexity. As for the uplink, the SC-OQAM/FBMC MIMO system significantly reduces the PAPR and enhances the BER performance, with relatively low additional computational complexity

A Low-Complexity SLM PAPR Reduction Scheme for OFDMA

In orthogonal frequency division multiplexing (OFDM) systems, selected mapping (SLM) techniques are widely used to minimize the peak to average power ratio (PAPR). The candidate signals are generated in the time domain by linearly mixing the original time-domain transmitted signal with numerous cyclic shift equivalents to reduce the amount of Inverse Fast Fourier Transform (IFFT) operations in typical SLM systems. The weighting factors and number of cyclic shifts, on the other hand, should be carefully chosen to guarantee that the elements of the appropriate frequency domain phase rotation vectors are of equal magnitude. A low-complexity expression is chosen from among these options to create the proposed low-complexity scheme, which only requires one IFFT. In comparison to the existing SLM technique, the new SLM scheme achieves equivalent PAPR reduction performance with significantly less computing complexity. MATLAB tool is used for simulating the proposed work