Abstract
Power control is an important issue for code division multiple access (CDMA) systems to achieve higher communication link quality. In this study, an adaptive two-loop power control scheme for CDMA systems is proposed. It includes an outer-loop controller and an inner-loop controller. A fuzzy logic controller (FLC) is designed to determine the target SINR for the required quality of service (QoS) in the outer loop to prevent vicious cycle, reduce target SINR tracking time, and lower outage probability. A shadow system with an H∞ filter (SS-H∞) is used to compensate round-trip delay and uncertainty in the inner loop via a multi-objective (MO) optimization method. Through MO optimization, the best compromise between target SINR tracking and the minimization of power consumption can be achieved. Combining these controllers in the outer loop and the inner loop, the proposed scheme can achieve a better performance in comparison with other existing schemes in CDMA communication systems.