Auxiliary-vector filters and adaptive steering for DS/CDMA single-user detection

Single-user detectors for direct-sequence code-division multiple-access (DS /CDMA) systems are characterized by their architecture, the design optimali ty criterion, the optimization computational complexity, and ultimately by their average bit error rate (BER) performance. With a fixed tap-weight arc hitecture that implies zero optimization cost, the conventional signature-m atched correlator positions itself as the low-cost low-performance solution . This paper submits a proposal that maintains the same tap-weight architec ture and introduces the concept of maximum cross-correlation auxiliary vect or filtering associated with minimum BER adaptive steering. Calculation of the auxiliary vector taps involves standard sample average estimation of th e data autocorrelation matrix, and no matrix inversion operation is require d, The resulting scalar parametrized filter is optimized adaptively in the minimum BER sense by a fast stochastic approximation recursion on R. Simpli city and BER comparisons place the proposed receiver competitively on the c ost versus performance curve. Numerical results under realistic small sampl e support scenarios support the theoretical developments and indicate that performance-wise the receiver compares favorably not only to the convention al matched-filter correlator, but also to the minimum-output-energy (MOE) d etector [17], the LMS-implemented minimum-mean-square-error (MMSE) filter [ 9]-[13], and the multiuser decorrelating receiver [5], [6] that assumes per fectly known interfering user population.