Distributed power control performance in DS-CDMA systems with adaptive quantization

One practical constraint imposed on closed-loop power control algorithms for a direct-sequence code-division multiple-access communication (DS-CDMA) system is the limited amount of feedback information. This paper proposes a closed-loop power control scheme with adaptive quantization on the basis of the number of power command bits. Adaptive quantization is used on the hypothesis that the quantization sensitivity can be defined as a function of the standard deviation of the reference error signal, while maintaining the feedback number of bits constant. Simulation results are presented to illustrate the performance of a distributed power control (DPC) scheme with adaptive quantization, using a classic proportional integral derivative (PID) power update. Moreover, the performance of the DPC algorithm with fixed quantization is also presented. Finally, both schemes are compared with the standard single-step power correction scheme.