Interference suppression capability of linear receivers for band-limited DS/SSMA communications

Interference suppression capabilities of linear receivers for band-limited direct-sequence spread-spectrum multiple-access (DS/SSMA) systems with aperiodic random spreading sequences are considered. First, bounds on the performance of systems with BPSK data symbols and QPSK spreading sequences are derived for fixed matched filter (MF) receivers and adaptive linear receivers. The bounds apply for the case in which the maximum conditional signal-to-interference ratio is obtained or, equivalently, for the case in which the linear minimum-mean-squared error (MMSE) criterion is used. The bounds are used to examine the dependence of the capability of the linear receivers to suppress multiple-access interference (MAI) on the system excess bandwidth and the profile of multiple-access users.