PSEUDO-DECORRELATING MULTIUSER RECEIVERS FOR ASYNCHRONOUS CODE-DIVISION MULTIPLE-ACCESS (CDMA) SYSTEMS

A new type of a linear decorrelating receiver, named Pseudo-Decorrelat or. for asynchronous code division multiple access systems over an add itive white Gaussian noise channel is presented in this paper. Startin g with the analyis of the multiple access components of the decision s tatistics, the outputs of a bank of matched filters, the (K x 3K) cros s-correlation matrix for each bit is obtained. The non-square cross-co rrelation matrix is then inverted using the concept of Penrose's gener alized inverse of a matrix. In this receiver, the detection process ca n be started before the whole sequence is received at the receiver, an d computing the inverse of a (KN x KN) cross-correlation matrix, gener ally required for linear decorrelating receivers, can be avoided becau se it is enough to compute only the generalized inverse of a (K x 3K) cross-correlation matrix for each data bit. Here, K is the number of u sers and N is the length of input data sequence. Simulation results ar e also presented for K-user systems over an additive white Gaussian no ise channel.