Pseudo-Decorrelating Multiuser Receivers for Asynchronous Code Division Multiple Access (CDMA) Systems in a Rayleigh Fading Environment

A new type of a linear decorrelating receiver, named Pseudo-Decorrelator, for asynchronous code division multiple access systems over a Rayleigh fading multipath channel is presented in this paper. Starting with the analyis of the multiple access components of the decision statistics, the outputs of a bank of matched filters, the (K × 3K) cross-correlation matrix for each bit is obtained. The non-square cross-correlation matrix is then inverted using the concept of Penrose’s generalized inverse of a matrix. In this receiver, the detection process can be started before the whole sequence is received at the receiver, and computing the inverse of a (KN × KN) cross-correlation matrix, generally required for linear decorrelating receivers, can be avoided because it is enough to compute only the generalized inverse of a (K × 3K) cross-correlation matrix for each data bit. Here, K is the number of users and N is the length of input data sequence. Simulation results are also presented for K-user systems over a Rayleigh fading multipath channel. key words: CDMA, decorrelating receiver, multiuser detection