A technique (300) and apparatus for sharing frequency spectrum amongst cognitive radios, without the use of a centralized control, is provided. By determining open segments of available spectrum within a brokered spectrum (306), and determining costs associated with those available segments (307), a CR device can identify an optimal spectral portion (308) within which to transmit (314) and grow (342) a narrowband signal. The occupied bandwidth growth is monitored such that cost associated with the growth does not exceed a cost threshold (341).