Ofdm System Channel Estimation

Orthogonal Frequency Division Multiplexing (OFDM) is a parallel transmission scheme of Multi-Carrier's Modulation. It has a good capability of countering multi-path fading and high data transmission rate. So OFDM has been regarded as one of the dominating technologies of 4G wireless communications system. And channel estimation is an important part of the OFDM system.Channel estimation can be generally separated into two kinds: Pilot-aided channel estimation and blind channel estimation. The article analysis the theory of blind channel estimation based on subspace and does simulations.Then the article analysis the theory of pilot-aided channel estimation.At last, the article researched the way of channel estimation based on the wavelet transform.We finded that the way has a good performance.But it needs complicated calculations.Again the defects, the article has done improvement on it.When the signals has been done the LS transform, it came to the wavelet transform by setting up a threshold to reduce the noise.Then it uses the improved algorithm to do channel estimation by further.The improvement is that use the SVD algorithm to reduce the order of the matrix.It equals to use SVD algorithm to the related matri of the channel.The eigenvalues is divided into useful signal vector and noice vector. According to the orthogonality of the eigenvector, we can calculate channel parameters. The matlab simulation results show that this method can not only achieve better estimation performance, and greatly reduces the computational complexity. It has good practicality.