A method (300) and cognitive radio (CR) wireless device (102) are provided for dynamically accessing spectrum in an opportunistic spectrum access wireless communication system (100). The method includes: transmitting, from a CR wireless device, a signal (216) having a first bandwidth within an unoccupied portion of spectrum (206), and after a time interval (T3) following the transmitting, and upon determining that an adjacent spectral quantum is occupied, transmitting from the CR wireless device a signal (216) having a second bandwidth, the second bandwidth being less than the first bandwidth. The method doubles a rate of growth of bandwidth of a transmitted signal when a spectral quantum adjacent to one side of the signal is unoccupied and a spectral quantum adjacent to the other side of the signal is occupied. The method utilizes knowledge of location of the CR wireless device and of band-edges to intelligently use spectral fence quanta.