A received total wideband power in a wireless communications system is measured (202) a number of times during a time interval. A site communication throughput is determined (204) and processed (206) into a time averaged site communication throughput. A probability distribution for received total wideband power is estimated (210) from the measured received total wide-band power. An estimate of a noise floor measure is computed (214) based on the probability distribution for received total wideband power and a noise rise measure is calculated (218) based on the probability distribution for received total wideband power and the estimate of a noise floor measure. According to the present invention, an adjustment (208) of the noise rise measure is provided based on the averaged site communication throughput.