Date Added: Dec 2010
Cognitive Radio (CR) technology has been considered promising to enhance spectrum efficiency via opportunistic transmission at link level. Several existing works focus on either spectrum sensing or dynamic spectrum sharing. But CR protocols allow in general a secondary user to transmit only when a licensed channel is not occupied by primary user. However waiting for idle timeslot may include large packet delay and high energy consumption for sensing. To overcome this, the authors consider an opportunistic spectrum access in cognitive radio taking into account packet delay and energy consumption. In particular, a secondary user decides to sense or not one primary channel based on partial observation of the primary channel occupancy and the age of his file.