## 1 Introduction  
In the communications industry, wireless mobile communications are one of the most important innovations of our time due to its impact on the global economy and society. Expectations grow with the arrival and demands that the fifth generation of mobile telecommunications (5G) brings associated with reliable and quality for everywhere user access [1, 2]. In [3], the 3 rd Generation Partnership Project (3 GPP) cemented OFDM as the preferred signal waveform in 5G, as in the previous generation, for both uplink and downlink. This is due to well-known advantages of OFDM, such as low-complexity signal processing based discrete Fourier transform (DFT) approaches, and one-tap single-carrier equalization due to the employment of cyclic prefix (CP) on transmission. Furthermore, the orthogonality between subcarriers allows for robust transmission upon severe multipath propagation. However, several studies provided alternative waveforms that are capable of outperforming some key OFDM performance indicators, the most notable being low spectral efficiency due to the use of CP, high out-of-band radiation, and large peak-to-average power ratio (PAPR) [4, 5]. Among the most recently proposed hybrid modulation waveforms, one promising candidate for beyond-5G wireless communications systems is the time-interleaved block-windowed burst orthogonal frequency division multiplexing (TIBWB-OFDM) [5, 6, 7, 8]. Based on the BWB-OFDM [9] modulation scheme, this technique guarantees better spectral efficiency and low power efficiency in comparison with conventional OFDM systems. The great advantage of this approach is that it creates a diversity effect in the frequency-domain, making it possible to recover part of the lost information caused by frequency-selective channel deep fades [6]. Additionally, it can be easily implemented for multiple-input multiple-output (MIMO) and massive MIMO systems [10]. The authors in [6] proposed for the first time the TIBWB-OFDM technique, which showed considerable gains in BER performance between this new scheme and the conventional OFDM modulation. In [7], the use of nonlinear equalization was proposed at the TIBWB-OFDM receiver, namely, of the iterative block decision feedback equalization (IB-DFE) type, with considerable gains in performance. In [8], a modified version of the TIBWB-OFDM signal was proposed that included an additional overlapping operation between adjacent subsymbols, allowing for achieving even better spectral efficiency. In this paper, we focus on the deployment of this modulation system in a more realistic scenario by addressing channel estimation and symbol synchronization problems, considering the case of severe frequency-selective channels (i.e., highly time-dispersive channels). These are, in fact, two important challenges to deal in the practical deployment of any wireless system due to channel variability along time that corrupts the transmitted signal and limits system performance [11]. Nevertheless, if the receiver is able to first correctly detect the frame beginning and accurately estimate the channel characteristics, then it is possible to recover information reliable. At the same time, we also assessed the performance of the TIBWB-OFDM technique under imperfect channel-state information (CSI), which, to the best of our knowledge, has not been studied so far. In order to perform timing synchronization, it is important to first detect the presence of data by measuring the received signal power, and then estimate the beginning of preamble sequences [12]. This can be conducted by searching for periodic structures within the signal, i.e., applying correlation-signal techniques between the received frame and known markers. Therefore, the use of cross-correlation could provide appropriate frame detection [13]. For that, it is important to carefully choose optimal preamble sequences for the system-acquisition process.