A Study of the Optimum Power Control Fixed Stepsize in the Presence of Power Control Loop Delay

Power control is one of the most important functions of wideband code division multiple access (WCDMA)-based system such as universal mobile telecommunication system (UMTS). A fixed stepsize power control algorithm is typically used in UMTS. The optimum fixed stepsize depends on the maximum Doppler frequency or user speed. This paper aims to study the optimum fixed stepsize within a range of user speeds. The simulation results show that a large fixed stepsize is optimal for a user moving fast when there is no additional loop-delay in the power control. In the presence of an additional loop-delay, a larger fixed stepsize is no longer suitable for a user moving at a high speed. In this particular scenario, power causes more fluctuations in received signal than no power control.