Adaptive Two-Loop Power Tracking Control in CDMA Systems with the Utility Optimization

An adaptive two-loop power tracking control scheme is proposed for direct sequence code-division multiple-access (DS-CDMA) cellular systems in a wireless network. The scheme includes an outer-loop controller and an inner-loop controller. An adaptive searching algorithm is designed for determining an optimal target signal to interference and noise ratio (SINR) for each user in the outer loop. The utility optimization can be achieved by using the adaptive algorithm through the net utility function based on the quality of service (QoS) for the purpose of resource management of wireless communication networks. A prediction control is designed to compensate for the effect of round-trip time-delay, channel fading, multiple access interference (MAI), and noise in the inner loop. The optimal target SINR tracking can be achieved by using the prediction control through a robust pole placement. Combining these two controllers in the outer loop and inner loop, utility optimization and target SINR tracking can be achieved at the same time. The stability and convergence of the proposed scheme are discussed. Several simulation results are given to confirm the performance of the proposed method.