A new spectrum sensing strategy when primary user has multiple power levels

In this paper, we study a more practical cognitive radio (CR) scenario where the primary user (PU) operates under more than one transmit power levels. Different from the existing research where PU is assumed to have only one constant transmit power, the new consideration well matches the existing and ongoing standards, i.e., IEEE 802.11 Series, GSM, LTE, LTE-A, etc. The primary target in this new consideration is still to detect the presence of PU, while a secondary target to identify the PU\´s transmit power level could also be achieved. By doing this, the secondary user (SU) could realize more "cognition" compared to the conventional strategy where only the `on-off" status of PU is detected. To make the study complete, we derive closedform results for multiple thresholds as well as the performance analysis. Numerical examples are provided to corroborate the proposed studies.