Waveform Design In Doubly Dispersive Channel Based On Weighted Fractional Fourier Transform

With the rapid development of wireless technology and the increasing demand for wireless communication quality, it should meet the requirements of quality of communication in the environment of"two high": high data rate and high moving speed between terminal and base station. But in the background of high moving speed and high data rate, channel displays the features of doubly dispersive, including time dispersive caused by multipath delay and frequency dispersive caused by Doppler shift. Against doubly dispersive channel, a proper waveform design is given in this passage by use of Weighted-type Fractional Fourier Transform (WFRFT) to resist time-frequency interference.Firstly, the characteristics of doubly dispersive channel are introduced. Respectively, the characteristics and models of time dispersive channel and frequency dispersive channel are given. For doubly dispersive channel, Basis Expansion Model (BEM) is an efficiency way of channel estimation, which lows complexity.Secondly, the theory of WFRFT is summarized. WFRFT is widely used in the field of signal processing as a time-frequency tool. The research process of WFRFT is introduced in this chapter, then mathematical definition of WFRFT and transform matrix of discrete sequence are given.Finally, a waveform design is proposed to anti time-frequency fading in doubly dispersive channel. For doubly dispersive channel model established by using of a simplified selective fading channel modeling, channel matrix is generated by use of WFRFT. Taking advantage of that conjugate transposed row vectors of 4-WFRFT are eigenvectors of channel matrix, waveform design is proposed in BPSK modulation and QPSK modulation. Then Monte Carlo simulation is given to validate the theory. The results of simulation show that the waveform design proposed has ability of resisting time-frequency interference.