Two-mode fast power control for WCDMA systems

Power control is needed in WCDMA systems to mitigate a so-called near-far effect, which is caused by the large variations of signal strength due to the Rayleigh fading radio propagation channel. This paper proposes an improved fast power control scheme for WCDMA systems, suitable for real implementation. Realistic constraints for the power control command length and step size are taken into account. The scheme consists of an adaptive generalized minimum-variance self-tuning controller and a simple bang-bang controller, which is used as a backup for the adaptive controller. The adaptive controller takes advantage of both the current and previous signal-to-interference ratio (SIR) measurements and power control commands. The proposed algorithm (called STGMV-PC for self-tuning generalized minimum-variance power control) is used in the uplink, while only a bang-bang controller is used in the downlink. Computer simulations indicated that better performance can be achieved with the proposed algorithm in comparison with either bang-bang or pure minimum variance controller