Iterative rake receiver and corresponding reception process

Abstract

A CDMA radiocommunication signals receiver for receiving signals obtained from spectrum symbols spread using pseudo-random sequences and having been propagated along a number of paths. The receiver includes a filter configured to restore L unspread signals for each symbol, corresponding to L different paths, a calculating circuit configured to calculate L estimates of the L different paths, and a demodulator configured to process each of the L unspread signals using the corresponding L estimates to obtain L path contributions. Also included is an adder configured to form a sum of the L path contributions and for outputting an estimate of a received symbol, and a decision circuit configured to make a decision about a value of the received symbol based on a value of the estimate of the received symbol output by the adder. Further, the receiver processes blocks of N symbols, each block having data symbols and control symbols, each symbol being identified by a rank k that it occupies in the block, where k varies from 0 to N−1. Also, for each path identified by an index l, where l varies from 0 to L−1, and for each block, the receiver considers a vector C with N components that characterizes the path during the block, and the receiver defines a vector base B , vectors of the vector base B being N eigenvectors of the matrix E [C C ], each vector C being decomposed in the vector base, where decomposition coefficients denoted G form independent random Gaussian variables. In addition, coefficients G , define a vector G with N components for each path l, and the calculating circuit estimates each vector G , using an iterative process based on EM estimation-maximization algorithm based on a maximum a posteriori probability criterion.