The Research Of The Channel Estimation Of OFDM System Based On Pilot

OFDM(orthogonal frequency division multiplexing) is a parallel transmission scheme of Multi-Carriers Modulation. It transmits information through orthogonal multiple sub-carriers and has high utilization of frequency spectrum, good capability of countering multi-path interference. It is also adaptive to high-rate data transmission and multimedia data transmission. This technology has been regarded as the core technology of 4G wireless communications system in the future.Channel estimation is one of research hotspot, and many related algorithms are presented these years all over the world. These algorithms can be separated into two kinds: channel estimation based on pilot and blind channel estimation. Channel estimation based on pilot can obtains the channel impulse response for all sub-carriers by pilot sub-carrier. It can tracks the variety of channel, and obtain high accuracy with low complexity, so it's a practical channel estimation method.This paper mainly researches on the channel estimation based on pilot, summarizes multi-path and time-variety statistic properties of general wireless channel, analysis the properties of channel, especially multi-path fading and Doppler shift's influence to system. Based on these analysis, the paper investigates principles and performances of the existing channel estimation methods in block-type and comb-type pilot arrangements. To block-type pilots arrangement, the performances of channel estimation is discussed with least square criterion and minimum mean squared error estimation criterion. To comb-type pilots arrangement, the paper puts the pilots to the least square criterion to estimate the channel frequency domain response by using different interpolation methods. Then, the paper introduces time domain filter and transform domain filter methods to suppress the effects of noise to the channel estimation. Finally, this paper introduces a channel estimation algorithm based on frequency offset. Known from general algorithm, this algorithm takes the effect of residual frequency offset into account. It can estimates the length of channel impulse response effectively and suppresses the effect of frequency offset to the system.To validate the feasibilities of different OFDM system channel estimation...