Joint space-time auxiliary-vector filtering for DS/CDMA systems with antenna arrays

Direct-sequence/code-division multiple-access (DS/CDMA) communication syste ms equipped with adaptive antenna arrays offer the opportunity for jointly effective spatial and temporal (code) multiple-access interference (MAI) an d channel noise suppression. This work focuses on the development of fast j oint spate-time (S-T) adaptive optimization procedures that may keep up wit h the fluctuation rates of multipath fading channels. Along these lines, th e familiar S-T RAKE processor is equipped with a single orthogonal S-T auxi liary vector (AV) selected under a maximum magnitude cross-correlation crit erion. Then, blind joint spatial/temporal MAI and noise suppression with on e complex S-T degree of freedom can be performed, This approach is readily extended to cover blind processing with multiple AV's and any desired numbe r of complex degrees of freedom below the S-T product. A sequential procedu re for conditional AV weight optimization is shown to lead to superior bit- error-rate (BER) performance when rapid system adaptation with limited inpu t data is sought. Numerical studies for adaptive antenna array reception of multiuser multipath Rayleigh-faded DS/CDMA signals illustrate these theore tical developments, The studies show that the induced BER can be improved b y orders of magnitude, while at the same time significantly lower computati onal optimization complexity is required in comparison with joint S-T minim um-variance distortionless response or equivalent minimum mean-square-error conventional filtering means.