A method of operating a cognitive radio, CR, device to avoid interference with an incumbent receiver, comprising: determining a maximum allowed transmit power level of the CR device based on at least one estimated incumbent signal level in a local environment, at least one corresponding estimated transmitter out-of-band splatter level of the CR device, and at least one co-channel incumbent receiver protection requirement: and transmitting with no more than the maximum allowed transmit power level thereby avoiding interference with the incumbent receiver while maximizing a transmit power level of the CR device, characterized in that the determining a maximum allowed transmit power level comprises: selecting a first transmit power level that is a minimum of the at least one estimated incumbent signal level by applying a first offset from the at least one estimated incumbent signal level, said offset determined by the at least one co-channel incumbent receiver interference protection requirement; determining the at least one corresponding estimated out-of-band splatter level; and selecting a second transmit power level that is a minimum as determined by the at least one corresponding estimated out-of-band splatter level by applying a second offset from the at least one estimated incumbent signal level based on the least one corresponding estimated transmitter splatter level and the at least one incumbent receiver co-channel interference protection requirement. determining a maximum allowed transmit power level of the CR device based on at least one estimated incumbent signal level in a local environment, at least one corresponding estimated transmitter out-of-band splatter level of the CR device, and at least one co-channel incumbent receiver protection requirement: and transmitting with no more than the maximum allowed transmit power level thereby avoiding interference with the incumbent receiver while maximizing a transmit power level of the CR device, characterized in that the determining a maximum allowed transmit power level comprises: selecting a first transmit power level that is a minimum of the at least one estimated incumbent signal level by applying a first offset from the at least one estimated incumbent signal level, said offset determined by the at least one co-channel incumbent receiver interference protection requirement; determining the at least one corresponding estimated out-of-band splatter level; and selecting a second transmit power level that is a minimum as determined by the at least one corresponding estimated out-of-band splatter level by applying a second offset from the at least one estimated incumbent signal level based on the least one corresponding estimated transmitter splatter level and the at least one incumbent receiver co-channel interference protection requirement. selecting a first transmit power level that is a minimum of the at least one estimated incumbent signal level by applying a first offset from the at least one estimated incumbent signal level, said offset determined by the at least one co-channel incumbent receiver interference protection requirement; determining the at least one corresponding estimated out-of-band splatter level; and selecting a second transmit power level that is a minimum as determined by the at least one corresponding estimated out-of-band splatter level by applying a second offset from the at least one estimated incumbent signal level based on the least one corresponding estimated transmitter splatter level and the at least one incumbent receiver co-channel interference protection requirement.