Variable Step Closed-Loop Power Control in Cellular Wireless CDMA Systems under Multipath Fading

The power control has been widely studied and shown to be crucial for the capacity and performance of direct-sequence code-division multiple-access (DS-CDMA) systems. Practical implementations typically employ fast closed-loop power control, where transmitters adjust their transmit powers according to commands received in a feedback channel. The loop delay resulting from the measurements, processing, and transmission of the power control commands can result in oscillations of the transmission powers and lead to degradation in the system performance. In this paper we present new variable step closed-loop power control algorithm (VSPC) and fixed-step closed loop power control with information feedback (FSPC-IF), that are able to increase speed of convergence and alleviate the effect of the loop delay. We carried out computational experiments on a DS-CDMA network using these algorithms. Fixed-step power control with decision feedback (FSPC-DF) is reference algorithm. New algorithms are compared with it. The numerical results indicate that new algorithms can significantly improve the radio network capacity without any increase in power control signaling, also increase speed of convergence and decrease loop delay.