Patent ID: 6377610
Filing Date: 2002-04-23
Classification: H03M,H04B,H04L

Abstract:
A decoding method for demodulating a received signal available in serial code concatenation in a code-division multiple access transmission system, a two-step coding being carried out at the transmitting end of the transmission system, a first step of the two-step coding including a Hadamard orthogonal multi-step inner code, a second step of the two-step coding including an outer error-correcting code of a predefined rate, the method comprising:providing a soft-in/soft-out decoder in a receiver of the transmission system, a first decoder step of the soft-in/soft-out decoder including an inner decoder, a second decoder step of the soft-in/soft-out decoder including an outer decoder; and processing soft values as reliability information at an output and an input of the soft-in/soft-out decoder, a soft output of the inner decoder being a soft input for the outer decoder, a channel reliability information output from a preceding demodulation being an input for the inner decoder, wherein the first decoder step of the soft-in/soft-out decoder and the second decoder step of the soft-in/soft-out decoder are configured to decode the received signal coded in the two-step coding, wherein the receiver includes an incoherent receiver structure including a RAKE receiver, wherein a soft input of the inner decoder includes a-priori information for systematic bits of Walsh functions of the inner code, the inner Hadamard code being decoded by entering an a-priori information vector L(u) into an instruction of the inner decoder, the instruction being such that for each bit decision, in a summing of a numerator and a denominator of a term to be expressed logarithmically of each considered element of a square-law-combining fast Hadamard transform resultant decision vector w, three terms are multiplied, a first term of the three terms being a-priori probabilities P(xj), a second term of the three terms being an exponentiated vector element, a third term of the three terms being a modified Bessel function of the first type of power (L-1) with argument, L being a number of fingers of the RAKE receiver, x being a Walsh function.