## 1 Introduction
In terms of the pilot-aided channel estimation, the pilot-aided channel estimation schemes consist of two parts: (1) Channel estimation using orthogonal pilots: As the subcarrier interval of the FTN signal is the same as that of the OFDM system, the compatible channel estimation scheme can be adopted. However, compared with the FTN signal, the time duration of an orthogonal pilot symbol is longer than that of the FTN symbols due to the lower data rate in each subcarrier, resulting in a slight decrease in the spectral efficiency [23; 24; 25; 26; 27]. Furthermore, the pilot symbols and the data symbols are time division multiplexing and the longer symbol period will lead to the inapplicability of rapidly time-varying multipath fading channels. (2) Channel estimation using DBT-MC-FTN pilots: When the DBT-MC-FTN symbol is used as the pilot for channel estimation, the period of the symbol is the same as that of an orthogonal symbol while the subcarrier interval is compressed. As a result, there is no effect on the spectral efficiency, but the self-introduced ISI and ICI will affect the accuracy of channel estimation [28; 29; 30; 31; 32]. Moreover, to apply the above channel estimation and equalization scheme, some frame structures based on FTN transmission have been proposed in [9; 10; 15; 33; 34]. In this paper, a low complexity two-dimensional compression scheme called DFT based block transmission for multicarrier faster-Than-Nyquist (DBT-MC-FTN) signaling is proposed. The key idea of the proposed DBT-MC-FTN can be depicted as follows. By resorting to the circular convolution and DFT operation, an efficient transceiver architecture is derived. The proposed DBT-MC-FTN transmitter can be viewed as the concatenation of several smaller size DFTs, frequency domain window, and a larger size IDFT, and the receiver is the corresponding reverse process. As a result, flexible time- and frequency domain compression can be achieved in a unified manner. One difference between our scheme and the one proposed in [8] is that frequency domain compression cannot be achieved for the latter, thus full use may not be made of the scarce spectral resource. To combat the multipatheffect in the fading channel, a cyclic prefix (CP) is added to the DBT-MC-FTN symbol so that channel induced ISI can be eliminated through frequency domain equalization. Moreover, since the artificially introduced ISI and ICI in the DBT-MC-FTN system are known to us when the compression factor is determined, the ISI and ICI can be computed offline and canceled via the soft successive interference cancellation (SIC) detector at the receiver with an acceptable complexity. To sum up, the novel contributions of this paper are as follows:  
* We first propose a DFT based block transmission for multicarrier FTN signaling scheme, i.e., DBT-MC-FTN, where the two-dimensional compression in both time-domain and frequency-domain can be realized efficiently by adjusting the operation parameters. * CP-based channel frequency domain equalization and soft SIC detector are deployed respectively to eliminate the ISI and ICI introduced by the channel and the two-dimensional packing in the DBT-MC-FTN signaling. The effectiveness of the proposed detector is verified by the simulations. * Based on the special structure of the proposed DBT-MC-FTN scheme, two pilot transmission schemes for channel estimation have been proposed. The two schemes are time-division multiplexing (TDM) non-orthogonal pilots and multiplexing orthogonal pilots in the same time-frequency resource, respectively. We demonstrate that time-domain estimation using non-orthogonal pilots performs better while other schemes have error floors when the simple least square (LS) algorithm is implemented. The remainder of this paper is organized as follows. In Section 2, we present the system model of the proposed DBT-MC-FTN system and propose the corresponding receiver that takes consideration of the influence of a multipath fading channel.