An adaptive direct-sequence code-division multiple-access receiver for multiuser interference rejection

An adaptive receiver is considered for use in combating the near-far problem in direct-sequence code-division multiple-access (CDMA) communication networks. The focus of the paper is on the multiuser interference rejecting capability of the receiver. The receiver uses a chip matched filter followed by an adaptive equalizer structure to perform the despreading operation. This adaptive structure allows the receiver to adjust to the prevailing interference and noise environment. An analysis of the receiver giving the form of the equalizer coefficients and the mean squared error in steady state is given. From these results the capacity of a CDMA network using this receiver structure is obtained and compared with a system using conventional receivers. The receiver is shown to be immune to the near-far problem in the sense that the performance without any power control is nearly identical to the performance with perfect power control. The receiver is also shown to offer a two-fold increase in capacity relative to a conventional receiver with perfect power control.<>