Robust Two-Loop Power Control for CDMA Systems via Multiobjective Optimization

A robust two-loop power control scheme for code-division multiple-access (CDMA) systems is proposed in this study. It includes an outer-loop controller and an inner-loop controller. A fuzzy logic controller (FLC) is designed in the outer loop to adjust the target signal-to-interference-plus-noise ratio (SINR) for the required quality of service (QoS). It can prevent a vicious cycle and reduce the outage probability. In the inner loop, a shadow system with an
H
_∞
filter (SS-
H
_∞
) is used for the power controller to compensate for round-trip delay and uncertainty via a multiobjective (MO) optimization method. Through MO optimization, the best compromise between optimal target-SINR tracking and minimization of power consumption can be achieved. By combining these controllers in the outer loop and the inner loop, the proposed scheme can achieve better performance in comparison with other existing power control schemes in CDMA communication systems.