Patent ID: 7492808

Claim:
A method for decoding received signals on communication channels between at least one transmit antenna and plural receive antennas in a space-time coded direct sequence (DS)-CDMA communication system, comprising steps of: (a) obtaining an error value between (i) a despread signal χ m p ({circumflex over (X)} k (i)) corresponding to {circumflex over (X)} k (i) determined as a received symbol in an i-th symbol time, and (ii) a despread signal γ k p (i) of a received signal r(i) in the i-th symbol time for a k-th user of a p-th path at a m-th receive antenna; (b) adjusting a step-size, which is an updating unit for a tap weight vector for despreading the received signals, using the error value obtained in the step (a); (c) updating the tap weight vector using the error value obtained in the step (a) and the step-size obtained in the step (b); and (d) despreading a received signal r(i+1) in an (i+1)-th symbol time using the tap weight vector obtained in the step (c), wherein, p={1, 2, 3, . . . , P}, P is the number of paths on the communication channels, m={1, ,2, 3, . . . , M}, M is the number of receive antennas of DS-CDMA communication system, k={1, 2, 3, . . . , K}, K is the number of users of DS-CDMA communication system; and i={1, 2, 3, . . . , F}, F is a frame length of DS-CDMA communication system, wherein a step size μ(i+1) applied to the (i+1)th symbol time is given by the following equation: μ( i +1)=μ( i )+α Re{e ( i ) r t ( i ) Y ( i )} [Equation 1] wherein, α denotes a learning rate of a LMS (Least Mean Square) algorithm, e(i) is the error value between χ m p ({circumflex over (X)} k (i))and γ k p (i), r(i) is the received signals of the i-the symbol time, T is a transpose operator, and Y(i) is a derivative ∂w(i,μ)/∂μ| μ=μ(i) of the tap weight vector in the i-th symbol time.