Patent ID: 6768713
Filing Date: 2004-07-27
Classification: H04B,H04L

Abstract:
An Orthogonal Frequency Division Multiplexing (OFDM) receiver for receiving a signal representing data symbols transmitted through a plurality of channels and for supplying an estimation (Ã‚) of the data symbols comprising:a plurality of branches of diversity processing blocks of digital symbols, each block comprising data and pilot symbols distributed within a bi-dimensional time-frequency block at Nt intervals of time and Nf intervals of frequency, each branch of diversity comprising a radio sensor supplying an output signal with N components comprising the components of a vector Rl where l designates a row of the branch of diversity, l ranging from 0 to (Lâˆ’1), a channel estimator configured to receive the output signals supplied by the branches of diversity to process the output signals, and to supply flexible estimations of the data symbols, a decision making device configured to receive the flexible estimations of the data symbols and to supply the estimation (Ã‚) of the data symbols, wherein: the channel estimator processes a vector Cl with N components characterizing an estimated channel for each bi-dimensional time-frequency block; said channel estimator configured to define a base of N vectors Bk which are N eigenvectors standardized from a time-frequency covariance matrix of the estimated channel; said channel estimator decomposing each vector Cl in this base giving N coefficients; the N coefficients from this decomposition being designated Gkl with k ranging from 0 to Nâˆ’1; the coefficients Gkl defining, for each branch of diversity l, a vector Gl, which is a representation of the estimated channel at an output from said branch of diversity, said channel estimator processes a finite number of iterations in accordance with an expectation-maximization (EM) algorithm based on a criterion of maximum probability a posterior; the estimator initially being implemented by taking into consideration the pilot symbols contained in the bi-dimensional time-frequency block being considered, which leads to a zero (0th) order estimation; the channel estimator then taking into consideration the pilot and precedent flexible data symbols estimated for a next iteration up to a final iteration, when the finite number of iterations is reached; the channel estimator supplying, after said final iteration, the optimum coefficients Gkl(D), k from 0 to Nâˆ’1, and l from 0 to Lâˆ’1, defining each branch of diversity; the vector Gl representing the estimated channel.