A method and system for efficiently utilizing frequency spectrum resources is disclosed. The method comprises the steps of determining at least one spectrum opportunity (510), wherein the opportunity is identified by a frequency range and a time duration, determining a set of altered transmission characteristics (515, 517) to allow transmission of a desired signal in the identified frequency range, wherein the altered transmission characteristics avoid interference with signals expected in the frequency range, and transmitting said desired signal using the altered transmission characteristics when the transmission occurs during said time duration. In one aspect of the system, the step of determining at least one opportunity comprises the steps of receiving signals in known frequency ranges, and determining the characteristics of the received signals. The system comprises a receiving unit (1001) for receiving information items regarding at least one receivable signal, a processing unit (862) for determining characteristics of the at least one received signal, a managing unit (864) for altering transmission characteristics of a desired signal based on the determined received signal characteristics, wherein the altered transmission characteristics avoid interference with the received signals and a transmission unit (866) receiving said altered transmission characteristics to transmit said desired signal. In one aspect, the desired signal transmission characteristics are altered in a frequency range/time period to avoid interference with received signals in the frequency range.