A constrained adaptive diversity combiner for interference suppression in CDMA systems

A multisensor interference cancellation scheme for CDMA communication systems is presented. The algorithm consists of constrained output power minimization at each sensor followed by optimal combining of the sensor outputs. Knowledge of the desired user´s code is used to specify the constraint for minimizing the output power at each sensor of the array. If the codes (and timing) of other users (i.e., interferers) are known, they may be incorporated as additional constraints to improve receiver performance. Optimal combining of the individual sensor outputs is achieved by employing the LMS algorithm in tracking mode for the adaptation. The receiver is blind in the sense that only knowledge of the desired user´s code (not the actual transmitted bit sequence) and associated timing is necessary. Algorithm performance results for Rayleigh fading channels are presented in the form of signal to interference-plus-noise ratios and bit error rate curves