Channel Estimation On The Wireless OFDM Systems

Channel Estimation technique is one of the key techniques in OFDM systems. Communication systems can enhance their BER performance by using coherence detection only when they could make precise and real-time estimation of fading coefficients of multipath channel. Recently, more and more researches are focused on channel estimation techniques of OFDM systems. According to the characteristics of various algorithms, we can classify them into three types: pilot-assisted channel estimation, blind and semi-blind estimation. In this paper, we study the production of the current estimation algorithms based on the introduction of the principle of wireless OFDM system. Finally two new algorithms for OFDM channel estimation are proposed.1. A new algorithm based on diagonal pilot structure is proposed for OFDM systems channel estimation. This method fully uses the pilot message of the time axis, the sequence axis and the proximate Euclidian distance, which is not only suitable to slow time varying channel but to fast one.2. Based on the Maximum Likelihood, a new channel blind estimation algorithm is given, which uses the auto correlation matrix of the vector of received signal in the OFDM systems. It estimates the influence of the OFDM channel before DFT transmit.