Channel Estimation Algorithm For Wireless Ofdm Systems

This thesis mainly focuses on the algorithms for channel estimation in the wireless OFDM systems including pilot assisted channel estimation and channel blind estimation.At first, the properties of the wireless fading channel are introduced, Secondly the principles of the OFDM systems are discussed, in which the design for the OFDM systems receivers and influence on performance of systems resulted from parameter non-synchronization and error from channel estimation are investigated respectively. In addition, the synchronization algorithms are reviewed and summarized.In the section for channel estimation algorithms based on pilot assisted, the existing algorithms including Wiener filtering in the sense of MMSE and interpolation filtering in the sense of LS for different pilot arrangements are summarized systemically, and the performance, complexity and spectrum efficiency of different algorithms are analyzed and discussed. Besides, a new algorithm by using Wiener filtering combined with interpolation filtering is proposed. The novel algorithm reduces the complexity remarkably with performance slightly degraded.In the another section for channel blind estimation, an improved algorithm is proposed based on the conventional channel blind estimation algorithm which uses the autocorrelation matrix of the vector of received signal in the OFDM systems. The improved algorithm uses cross-correlation between cyclic prefix and a special sub-vector from vector of received signal to implement channel blind estimation. The improved algorithm not only reduces the complexity of the conventional algorithm, but also improves its performance in theory. In the end, two algorithms grounded on subspace and cyclostationarity for channel blind estimation are introduced briefly.