A wireless broadband communications system that increases data throughput and link availability through more efficient use of the electromagnetic spectrum allocated to the system. In one mode of operation, the system periodically measures a noise or interference level associated with each one of a plurality of communications channels, and generates a histogram of the measurements associated with each channel. Next, the system determines a noise/interference level estimate for each channel as a predetermined percentile of the histogram associated with the respective channel. The system then selects a respective one of the channels having the lowest noise/interference level estimate for subsequent signal transmission.