Apparatus for adaptive reverse power control for spread-spectrum communications

Abstract

A code-division-multiple-access (CDMA) system employing spread-spectrum modulation. The CDMA system has a base station (BS), and a plurality of subscriber units. The signals transmitted between the base station and subscriber unit use spread-spectrum modulation. The improvement method for adaptive reverse power control (APC) from a subscriber unit (SU) to a base station (BS), comprises the steps of sending from the subscriber unit, using spread-spectrum modulation, a SU-spreading code on a reverse channel. The base station despreads the SU-spreading code on the reverse channel as a despread signal, determines a first power level Pwhich includes power of the despread signal plus noise and a second power level P, which includes despread-noise power. The base station determines a first error signal e, from the first power level P, the second power level P, and a required signal-to-noise ratio SNRfor service type, and a second error signal e, from a measure of total received power Pat the base station, and an automatic gain control (AGC) set point P. The base station forms a combined error signal from the first error signal e, the second error signal e, a first weight a, and a second weight a, and hard limits the combined error signal to form a single APC bit. The APC bit is transmitted to the subscriber unit. In response to the APC bit, the subscriber adjusts transmitter power to the base station.