Coded performance of dual-rate decorrelators combined with an array of antennas for synchronous multiuser DS/CDMA systems

Two types of decorrelating detectors proposed for a dual rate synchronous DS/CDMA channel are extended to incorporate an array of antennas. The resulting detectors are termed as the array low-rate decorrelator (ALRD) and the array high-rate decorrelator (AHRD). In AHRD, maximal ratio combining on N consecutive decorrelated outputs is applied for the low-rate users. Asymptotic performance is compared numerically in the context of channel coding with two different types of spreading code assignments. In the worst-case random assignment, both detectors are sensitive to the interferers´ directions of arrivals. Especially, performance degradation of the low-rate user is noticeable. In the cyclic assignment of the maximal-length shift register code for the low-rate users, ALRD is less sensitive to the spatial distributions of the interferers, whereas AHRD is sensitive to the distributions of the low-rate users and less sensitive to the distributions of the high-rate users. We confirm that both detectors show the near-far resistant property and good asymptotic performance depending on the spatial distributions of the interferers and spreading code assignments.