Patent ID: 7184465
Filing Date: 2007-02-27
Classification: H04B,H04J

Abstract:
1. A signal processing method for a base station of a code-division multiple access radio communication system, comprising the steps of: feeding a first signal received by the base station to a set of filters matched to spreading codes allotted to pilot channels originating from respective radio terminals; and processing output vectors from the matched filters to estimate parameters representing said channels, whereby the estimated parameters for a channel originating from a radio terminal comprise eigenvectors representing propagation paths between said radio terminal and the base station, respectively associated with amplitudes of reception along said paths, wherein the processing of the output vectors from the matched filters comprises: estimating parameters for at least one first channel on the basis of the output vector from a first filter matched to the spreading code allocated to said first channel; modifying the output vector from a second filter matched to the spreading code allocated to at least one second channel, the output vector from the second matched filter having less energy than the output vector from the first matched filter; and estimating parameters for said second channel on the basis of the modified output vector of the second matched filter, and wherein the modification of the output vector from the second matched filter comprises at least one subtraction of a vector proportional to a projection of said output vector from the second matched filter parallel to a vector of the form M H ,M 1 , v 1,i , where M 1 and M are matrices determined by the spreading codes respectively allocated to said first and second channels, v 1,i is one of the estimated eigenvectors for the first channel, and (.) H designates the conjugate transpose, wherein each of said pilot channels is formed jointly with a quadrature data channel emanating from the same radio terminal, the method further comprising the steps of feeding a second signal, received by the base station in phase quadrature with respect to said first signal, to a second set of filters matched to spreading codes respectively allocated to the data channels originating from the radio terminals; modifying some at least of the output vectors from the matched filters of the second set; and estimating information symbols transmitted on a data channel originating from a radio terminal by feeding the modified output vector from the second filter matched to the spreading code allocated to said data channel to a rake receiver defined by the parameters estimated for the pilot channel originating from said radio terminal, and wherein the modification of the output vector from said matched filter of the second set comprises at least one subtraction of a vector proportional to a projection of said output vector parallel to a vector of the form M′ H .M 1, .v 1,i , where M′ is a matrix determined by the spreading code allocated to said data channel.