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Summary Underwater acoustic wireless communication is considered as one of the most challenging communication technologies due to low propagation speed, water salinity, water depth, PH degree, and water temperature. Equalization is one of the means to improve the system performance. Matched filter (MF), zero forcing (ZF), and minimum mean square error (MMSE) equalizers can be used for channel equalization. Unfortunately, the performance of the matched filter is destroyed in the Multiple‐Input Multiple‐Output (MIMO) configurations. In addition, the ZF equalizer suffers from noise enhancement and high complexity because of the direct matrix inversion. On the other hand, the MMSE equalizer requires estimating the operating signal‐to‐noise ratio (SNR) to work properly. In this paper, we present a joint low‐complexity regularized ZF equalizer and carrier frequency offset (CFO) compensation scheme to deal with these problems. The proposed equalization algorithm mitigates the noise enhancement problem using a constant regularization parameter, and it can be implemented with low complexity using the banded‐matrix approximation. Also, we test the performance of the proposed system at different channel conditions. Simulation results show that the proposed equalizer has the ability to enhance the system performance with lower complexity than those of the other equalization algorithms at different channel conditions.

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The universal filtered multicarrier (UFMC) system is one of the novel candidate waveforms for 5G systems. UFMC is expected to achieve low latency, robustness against frequency offset, and reduce out-of-band (OoB) radiation that leads to a higher spectral efficiency. Although, the UFMC system offers many advantages as mentioned before, but being a multicarrier transmission technology, it suffers from high peak-to-average power ratio (PAPR). In this paper, a modified selected mapping (SLM) approach with low-complexity is proposed for reducing PAPR in UFMC systems. The main idea of the proposed modified SLM (P-SLM) approach is to utilize the linearity property of the UFMC modulator. The P-SLM approach generates U w alternative UFMC waveforms using U m UFMC modulators, where U m is the square-root of U w. Therefore, the computational complexity of the P-SLM approach is reduced compared to the existing SLM based PAPR reduction approaches for UFMC systems. The P-SLM approach is compared to the other approaches found in the literature in terms of PAPR reduction ability, bit error rate (BER) performance, and the computational complexity.