Abstract
Typically, the filter bank multicarrier with offset quadrature amplitude modulation (FBMC-OQAM) bears some impressive properties that make it popular as one of the substitutes to orthogonal frequency division multiplexing (OFDM) for the upcoming technology of broadband wireless communication systems. Although FBMC-OQAM preserves the multicarrier modulation (MCM) features, its spectrum usually suffers from impairments when subjected to the nonlinear behavior of a power amplifier (PA) which results in spectral re-growth. Due to the spectrum limitation and low energy efficiency foreseen in the forthcoming 5G networks, it is vital to confine the spectrum of the FBMC-OQAM signal within the allocated band of interest. In this paper, the suppression of the spectral re-growth experienced on the FBMC-OQAM signal due to the nonlinear distortion effects introduced by the PA is investigated. The crest factor reduction (CFR) method in combination with an adaptive digital pre-distortion (DPD) are used. The peak windowing technique based on sequential asymmetric superposition windowing (SASW) algorithm is used in the CFR part while the least square estimation with QR-decomposition (LSE/QR) has been used as the coefficient’s estimator and adaptation algorithm in the DPD part. The performance of the two combined techniques has been evaluated on SystemVue2018 simulation platform. The adjacent channel leakage ratio (ACLR) and the error vector magnitude (EVM) have been considered as the performance merits. The simulation results show that the proposed techniques significantly improve the spectrum, first by reducing the PAPR of the FBMC-OQAM signal by about 1.5dB. Secondly, the spectral re-growth has been reduced by about -45.74dB adjacent channel leakage suppression and the error vector magnitude measure has been obtained to be about 7.12%. (-22.95dB). These values lead to better average input power of the FBMC-OQAM signal and improvement in the spectral efficiency and they are in accordance with the 3GPP standard for wideband signals in nonlinear systems.
Highlights
The dynamic growth in the number of users that have different demands for accessing information under wireless communication is leading to spectrum scarcity
The FBMC-OQAM scheme has been studied as an alternative waveform candidate to Orthogonal frequency division multiplexing (OFDM) and is becoming the leading contender among the multicarrier modulation schemes proposed for the upcoming wireless communication systems, because of its ability of minimizing the out-of-band emission (OOBE), cyclic prefix (CP) free transmission, and robustness to the asynchronous situation [4,5,6]
The FBMC-OQAM signal still suffers from high peak-to-average power ratio (PAPR) which is susceptive to the nonlinear behavior of the power amplifier (PA), and as a result, it suffers from spectral re-growth
Summary
The dynamic growth in the number of users that have different demands for accessing information under wireless communication is leading to spectrum scarcity. Such power amplifiers come with high cost and they compromise energy efficiency [7, 8] which may not be suitable to many telecommunication network providers, that is why nonlinear power amplifiers are still common in many wireless transmitters, due to the high cost and low energy efficiency of the linear power amplifiers, the use of nonlinear power amplifiers is preferred They cause signal distortion which requires compensation techniques for signals with high peak values. The peak windowing approach [9, 10] based on the Kaiser window together with sequential asymmetric superposition widowing (SASW) algorithm [12] is used to reduce the high peak values experienced on the FBMC-OQAM signal The reasons for this are that this algorithm is applicable to both single and multicarrier signals. To the best of our knowledge, no published study has used the combination of the two algorithms to concurrently minimize both the PAPR and the spectral re-growth of the FBMC-OQAM under the nonlinear effects of the PA
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