| The limitation of bandwidth is becoming critical obviously with the development of wireless communications applied field and high skyrocketing data.In order to achieving faster speed transmission in this limited spectrum resources,faster than Nyquist(FTN).technology is proposed.Compared with orthogonal transmission scheme,FTN can increase the system capacity and spectral efficiency,thus getting a higher throughput.Nevertheless,this non-orthogonal pulses cause the transmission pulses to be overlapped partly or completely and hence inter symbol interference(ISI)exits in the transmission signals.This paper makes a research on transmitting FTN signal over frequency selective channel,the FTN shaping filter and ISI channel can both induced ISIs.To combat the composite ISIs problem,three types of transceiver structures are proposed in this paper.First of all,a FTN transceiver structure with concatenated frequency-domain equalization(FDE)is designed in this paper to combat these composite ISIs.Due to the FTN induced ISI is fixed and known at receiver without ISI estimation,thus the received signal is sent to the first equalizer deals with ISI caused by the FTN shaping filter directly after Faster Fourier Transform(FFT),the equalized signal after passing through the Invcrse Faster Fourier Transform operation and is sent back to the FFT block,then using the estimation channel information,the second FDE is applied on the signal to combat the remainder ISI induced by frequency selective channel.The simulation results show that the bit error rate(BER)performance can be improved with our proposed transceiver based on concatenated FDE than that with tradition FTN scheme with just one equalizer at the receiver.Then,the designed second FTN transceiver structure based on water-filling precoder is proposed in this paper.We derived the matrix operation of water-filling precoder by maximizing the decision signal-to-interference-plus-noise-ratio.At the transmitter,a water-filling precoder allocates the transmission power spectral density corresponding to the FTN shaping filter and the ISI channel,improving the system anti-interference performance.In addition,in order to achieve better BER performance,LDPC code is also investigated in this transmission.The simulation results show that the BER and throughput performance can be improved compared with the tradition FTN system without water-filling precoder.At last,the last proposed FTH transceiver structure is based on Tomlision-Harashima(TH)precoder.In this scheme the TH precoding is derived in the form of matrix operation to be applied at the transmitter to combat the composite ISI,induced by FTN and ISI channel.The simulation results demonstrate that the FTN can be reliable transmission in a lower system complexity with our proposed scheme.Moreover,the system spectral efficiency can be improved remarkable with TH precoded FTN transmission compared with orthogonal transmission. |
