Channel Estimation Of OFDM Systems Based On Basis Expansion Rapidly Time-varying Channel

As the core technology of the new generation wireless communication system,the orthogonal frequency division multiplexing technology has been widely used in a variety of wire and wireless communication systems.However,with the increase of the terminal moving speed,such as the rapid development of high-speed railway in recent years,the time variation of the channel is significantly enhanced,the inter-carrier interference caused by the Doppler Effect weakened the accuracy of channel estimation.So,how to ensure the accuracy of channel estimation in rapidly time-varying channel environment is worth researching.Channel estimation is the key condition of coherent demodulation which determines the performance of the whole system,so,it is the key point to achieve the accurate channel estimation in rapidly time-varying environment.In this paper,we study the pilot-assisted rapidly time-varying channel estimation based on BEM for OFDM systems,which is mainly reflected in two aspects:(1)In order to reduce the effect of ICI in rapidly time-varying environment to the performance of the channel estimation,first of all,from the principle and the characteristics of the ICI of the time-varying channel based on the Basis Expansion Model(BEM),by the characteristic analysis of ICI coefficients,only using the second step of the classical method called ICI self-cancellation demodulation,the value of ICI interference coefficient in adjacent subcarriers are almost the same,so,considering performing the second step one more time,we could found that the effect of simulation experiment of using the ICI self-cancellation step for two times is the most ideal.(2)Most of the rapidly time-varying channel estimation are based on independent time block,however when the coherent time of the channel and the period of the transmitted symbols can be compared,in order to improve the performance,considering using multi OFDM symbols here.At the same time,considering the use of pilot symbols to estimate the parameters,ignoring the interference of adjacent pilot symbols,so,according to the second step of classical ICI self-cancellation method,put forward a multi OFDM symbols ICI self-cancellation method,at the same time,in order to adapt to the more complex and changeable channel environment,proposed an adaptive OFDM symbol number time-varying channel estimation method with ICI self-cancellation Simulations results show that the proposed estimation algorithm has better performances in fast time-varying or slow time-varying channel environment.