Multiple antenna based sensing and recognition when primary user has multiple transmit power levels

In this paper, we consider the multiple antenna based spectrum sensing problem for a cognitive radio (CR) network. Different from conventional CR, we here consider a more practice-matching scenario when the primary user (PU) could work under more than one transmit power levels, depending on the communication environments. Consequently the spectrum sensing at the secondary user (SU), besides checking the on/off status of PU, could also identify PU's transmit power level if it is “detected”, making the overall sensing problem much more challenging. We design the optimal spectrum sensing algorithm when the channel information is known and partially known. New performance metrics under this new multiple primary transmit power (MPTP) scenario are defined to better evaluate the proposed algorithm, and quite a number of closed-form results are derived. Finally simulation results are presented to verify the proposed studies.