Code division multiple access (CDMA) communication system

Claim 1

An automatic maintenance power control (MPC) system for a multiple access, spread-spectrum communication system which maintains an initial transmit power level of a subscriber unit, comprising a base station and a plurality of inactive subscriber units, wherein the base station transmits a plurality of forward inactive channel information signals to a plurality of subscriber units as a plurality of forward channel spread-spectrum signals, and each of the inactive subscriber units occasionally transmits to the base station at least one reverse spread-spectrum signal having a reverse transmit power level and including a reverse channel information signal; the base station comprising: a) a plurality of reverse signal measuring means, each reverse signal measuring means comprising: means for measuring a reverse signal-to-noise ratio of a respective reverse channel information signal; a plurality of reverse error generating means, each reverse error generating means for generating a respective reverse channel error signal representing a difference between a respective reverse channel signal-to-noise ratio and a respective pre-determined signal-to-noise ratio; b) system noise measuring means for measuring a system noise power level of the spread-spectrum system comprising: means for receiving a plurality of reverse spread-spectrum signals; means for combining the received spread spectrum signals with an uncorrelated despreading signal to produce a noise signal; and means for measuring a power level of the noise signal to produce a system noise power signal; c) means for multiplying a difference signal by the system noise power signal to generate the reverse channel error signal; and d) a plurality of transmitting means, each transmitting means for transmitting a respective reverse channel error signal as a part of a respective forward channel information signal; wherein each subscriber unit comprises an MPC receiving means for receiving a respective one of the forward channel information signals and for extracting the respective reverse error signal from the forward channel information signal, and a subscriber transmit power adjustment means for adjusting the reverse transmit power level of the respective reverse spread-spectrum signal responsive to the respective reverse error signal.