Open-loop power control error on a frequency selective CDMA channel

Abstract

In order to combat shadowing and distance losses in a land mobile satellite system, an adaptive power control (APC) scheme is essential. Such a scheme, implemented on the uplink, ensures that all users' signals arrive at the base station with equal average power as they move within the satellite spot beam. Because of the lengthy round-trip delay on a satellite link, closed-loop power control systems are only of marginal benefit. Therefore, an open-loop APC scheme is proposed to counteract the effects of shadowing on a frequency-selective multipath fading channel. The power control scheme has been simulated. It has been found that the power control error can be approximated by a log-normally distributed random variable. To quantify the performance of the APC, the standard deviation of the power control error in decibels is presented as a function of the measurement time and vehicle velocity.