Modified Alternative-signal Technique for Sequential Optimisation for PAPR Reduction in OFDM-OQAM Systems

A modified alternative signal technique for reducing peak-to-average power ratio (PAPR) in orthogonal frequency division multiplexing systems employing offset quadrature amplitude modulation (OFDM-OQAM) is proposed. Lower PAPR reduces the complexity of digital to analog converters and results in increasing the efficiency of power amplifiers. The main objective of the algorithm is to decrease PAPR with low complexity. The alternative signal method involves the individual alternative signal (AS-I) and combined alternative signal (AS-C) algorithms. Both the algorithms decrease the peak to average power ratio of OFDM-OQAM signals and AS-C algorithm performs better in decreasing PAPR. However the complexity of AS-C algorithm is very high compared to that of AS-I. To achieve reduction in PAPR with low complexity, modified alternative signal technique with sequential optimisation (MAS-S) is proposed. The quantitative PAPR analysis and complexity analysis of the proposed algorithm are carried out. It is demonstrated that MAS-S algorithm simultaneously achieves PAPR reduction and low complexity

Numerical Simulation and Design of Low PAPR FBMC Communication System for 5G Applications

Unlike SC-FDMA (Single-Carrier Frequency Division Multiple Access), merging only DFT (Discrete Fourier Transform) addition with FBMC-OQAM (filter group multi-carrier with offset quadrature amplitude modulation) only cuts the marginal PAPR. (Peak-to-average power ratio). To take advantage of the single carrier effect of DFT extension, special conditions for the coefficients of the IQ (in-phase and quadrature phase) channels of every single subcarrier ought to be met. As a beginning point, we first originate this form, which we call the ITSM (Identical Time-Shifted Multi-Carrier) condition. Then, depending on this condition, we put forward a new FBMC for low PAPR. The foremost features of the offered way out are summarized as: First, to additionally raise the PAPR reduction, we created four candidate versions of the FBMC waveform for DFT spreading out and ITSM conditions and carefully chosen one with the least peak power. Even with various candidate generations, unlike the traditional SI (Side information) based PAPR reduction scheme, the focal computational fragments (such as DFT and IDFT) are shared and need only be executed one time. Therefore, matched to the prior DFT-expanded FBMC, the overhead in complexity is small, and the recommended pattern can realize a PAPR reduction comparable to SC-FDMA. Second, in the projected pattern each one pass on only two bits of SI from a block of FBMC-OQAM symbols. And so, the SI overhead is meaningfully lesser than a conventional SI-based scheme such as SLM (Selective Mapping) or PTS (Partial Transmission Sequence).The whole work is executed using MATLAB software. The PAPR of FBMC system has been significantly reduced after the application of proposed algorithm. PAPR was reduced by 25 % after the use of DFT spreading and ITSM conditioning

Peak Power Reduction in Multicarrier Waveforms

Modern wireless communication systems employ multicarrier waveforms, such as the widely-used Orthogonal Frequency Division Multiplexing (OFDM) and the recent OFDM with Offset-QAM (OFDM/OQAM) schemes. An inherent characteristic of these waveforms is the high Peak-to-Average Power Ratio (PAPR). One of the last stages of the transmitter is the power amplifier, which needs specific attention as a major source of power consumption. For acceptable levels of power efficiency, the high PAPR issue causes distortion to the signal due to the nonlinearity of the power amplifier. This is a major drawback of multicarrier systems and, if not addressed properly, could overcome their advantages. The PAPR reduction has been a topic of research for many years. By introduction of the new generations of the wireless systems, and perseverance of the more complicated multicarrier waveforms in finding their way into the proposed enabling technologies, this problem has gained interest again. Despite the relatively long history of research and the huge available literature, the problem is, to a great extent, still open. Among the disadvantages of the previously suggested PAPR reduction techniques, high computational complexity and complicated adaptation to the schemes such as OFDM/OQAM are standing out. In this thesis, in addition to an in-depth review of the multicarrier waveforms in question, the two aforementioned issues are tackled. The challenges in adaptation of the PTS technique to the OFDM/OQAM are investigated. Concerning the general issue of high computational complexity, the feasibility of using interpolation instead of direct oversampling in PAPR measurement is studied. Depending on the bandwidth configuration, the interpolation could be remarkably beneficial

Journal of Telecommunications and Information Technology, 2018, nr 3

kwartalni

Peak Regrowth Reduction Based on Segmental Approach for OFDM/OQAM signals

This paper proposes an Overlapped Segmental Deep Clipping (OS-DC) method to suppress the peak regrowth. OS-DC reduces Peak-to-Average Power Ratio (PAPR) in Orthogonal Frequency Division Multiplexing with Offset Quadrature Amplitude Modulation (OFDM/OQAM) signals without the need of multiple iterations. In OS-DC the clipping function is modified to deeply clip the high amplitude peaks and is applied to an OFDM/OQAM transmission system. This achieves up to four times reduction in peak regrowth in comparison to repeated iterative Overlapped Segmental Clipping and Filtering (OS-CF). Furthermore, it is also demonstrated that the proposed method improves signal quality compared to the normal clipping, for the same PAPR