Date Added: Apr 2012
The Cognitive Radio (CR) nodes in a Cognitive Radio Network (CRN) do not have license to use specific spectrum band. Instead, they use the spectrum bands of the licensed Primary Users (PU) without interfering with the PU. When the PU becomes active, interfering CRs should leave to another available spectrum band within the PU's Tolerable Interference Delay (TID). Therefore, CRN operates over wide spectrum bands which span many channels. Since each channel is typically licensed to one PU, this requires that channels be sensed separately. This adds monitoring overhead, where the CR should monitor (sense) the channel every TID, which reduces the throughput. For this reason, the node cannot monitor the whole set of channels.