The interference on the available communication frequencies is measured during an idle time slot over a first period of time at a first rate. The available frequencies are prioritized based on the interference measurements, and a list is formed of the frequencies having the lowest interference measurements. Interference measurements are made at a second rate, greater than the first rate, for a second period of time less than the first period. When a call is assigned, the interference level requirements for the call are given, and the carrier power level of the call is measured. The carrier-to-interference ratio of each frequency in the list is determined using the second interference measurements and the measured carrier power. The frequencies in the list meeting the interference level requirements for the call are then selected, and frequency hopping while serving the call is performed using the selected frequencies.