TIME AND FREQUENCY CHANNEL ESTIMATION IN AN OFDM SYSTEM

摘要

A radio channel estimation technique is described for use in a OFDM-based radio communications system. A block of OFDM symbols is transmitted from multiple antennas over multiple sub-carrier frequencies. The block of OFDM symbols includes known pilot symbols as well as data symbols to be determined by a receiver. The pilot symbols are transmitted in a predetermined pattern at periodic times on periodic sub-carriers. A pilot channel estimate is determined for each pilot symbol in the received block of OFDM symbols. An NxM matrix of points corresponding to the received OFDM symbol block is formed, N is the number of sub-carriers and M is the number of OFDM symbols in the OFDM symbol block. The matrix is formed by inserting pilot channel estimates at predetermined positions in the Nx M matrix according to the predetermined pilot pattern and inserting zeros in remaining positions in the NxM matrix. A two dimensional inverse Fourier transform of the N x M matrix is calculated resulting in multiple copies of a channel estimate in the time domain. One is selected, and a two dimensional Fourier transform of the selected channel estimate is calculated to obtain a channel estimate at each point in the OFDM block.