A PSAM Channel Estimation Algorithm Based On DFT And DCT For OFDM System

Because of the existence of time-varying characteristics of the wireless channel,the signal is easily affected in the propagation process,resulting in amplitude changes and phase shift,the occurrence of inter-symbol interference and so on.OFDM technology is used as advanced communication technology indicators,because it can ues limited spectrum resources better and resist excellently narrowband.The channel estimation is a part of the OFDM system,the main function of it is to recovery probably the data of the transmitting by using the received signal of the receiver after obtaining the impulse response or transfer function of the channel.So the channel estimation which is accurate and efficient has become the first condition which can improve the performance of communication systems.The main contents and main work of this paper are as follows:(1)The paper elaborates the history of wireless communication,the development and application of OFDM technology and its own advantages and disadvantages in detail;then the paper deeply analyzes large and small scale propagation characteristics of the wireless channel,and introduces two basic channel models of the wireless channel.Meanwhile,the basic principles and the core technology of OFDM,the insertion mode of the pilot and various interpolation methods are analyzed.The classical estimation criteria based on PSAM are compared and studied.(2)The paper discusses the principle of channel estimation in deeply.In order to alleviate the problem that the algorithm is not ideal for de-noising and the energy of the shock response is leakaged in the non-sampling interval channel,the original algorithm is optimized in the paper.Firstly,the kaiser window function is used for filtering for the result of the LS estimation in frequency domain,to reduce the energy leakage of the impulse response,and then selecting the appropriate threshold in the time domain to deal with the noise.Finally,the performance of the algorithm is verified by experiment,which indicates that the new algorithm can improve the transmission performance of OFDM system and have good use value.(3)At the same time,this paper also analyzes the DCT channel estimation algorithm.In order to further improve the system performance,a new method of OFDM channel estimation based on DWT and DCT interpolation is proposed.The new method first improves the accuracy of the response of the LS estimation by the wavelet transform.Then,after the Npoint IDCT,the average of the energy at each sampling point in the CP length is obtained as the decision threshold and it is compared with the energy at each sampling point.And according to the characteristic that the energy within the CP mainly is concentrated in a small number of sampling points to perform threshold filtering processing.The simulation results show that the new algorithm makes the noise in the cyclic prefix be effectively controlled,and the accuracy of the channel estimation is improved.