Study On The Applycation Of GDFT In OFDM Wireless Communication System

Generalized discrete Fourier transform (GDFT) can obtain the approximate optimum phase by introducing the nonlinear phase function to the traditional discrete Fourier transform (DFT) to achieve the flexible design of the phase function. Compared with the traditional discrete Fourier transform, GDFT have better correlation performance and flexibility. At present, it has been verified that the application of GDFT is valid only in the field of CDMA and MIMO Radar. Therefore, this article focuses on how to reduce the peak-to-average power ratio and accurately estimate the channel in OFDM system. Specific innovative research work are as follows:Firstly, optimal design process of GDFT is proposed by analyzing and summarizing the design methods of GDFT. The design process is not only suitable for the proposed channel estimation, but also for the future study.Secondly, the GDFT is introduced to selected mapping (SLM) algorithm because SLM algorithm is unable to suppress the high peak to average power ratio and it is necessary to sacrifice the bandwidth to send the side information in SLM algorithm. First of all, the possibility of GDFT applied to OFDM is examed by testifying the orthogonality of GDFT. Then, the GDFT which meets the minimum peak to average power ratio is regarded as the approximate optimal GDFT in GDFT-based peak to average power ratio reduction techniques. Finally, the approximate optimal GDFT is applied to reduce the high peak to average power ratio. The effectiveness of the proposed algorithm is verified by simulation. In addition, the bandwidth is kept due to the lack of side information and, to a certain extent, the amount of calculation is reduced because of the lack of M multiplications.Finally, GDFT is introduced to the channel estimation to overcome the weekness of DFT-based channel estimation that it is easy to cause the secondary ISI and ICI due to the correlation among the DFT algorithm First of all, the approximate optimal GDFT can be obtained by the proposed design process of GDFT. Then, the GDFT-based channel estimation can be executed by the optimal GDFT. Finally, Simulation results show that GDFT improves the correlation performance dramatically over DFT and channel estimation based on GDFT has better bit-error-rate (BER) performance than that based on DFT.