In the last ten years, we have been witnessing the vast growth in wireless communications due to the popularity of many wireless devices, mobiles, smart phones etc. As a result, the demand for high data rates, bandwidth, and spectrum utilization has increased. From a survey, it has been shown that limited spectrum is a crucial factor to the continued growth in wireless services. To fulfill this demand, the designers are having many difficulties with radio spectrum, multipath fading, interference etc. To meet the problem, they introduce multiple-input multiple-output (MIMO), where multiple antennas are used in transceivers to increase the diversity and multiplexing gains over single antenna systems. But, it seems impractical to implement in wireless devices. Thus, to overcome this drawback, cooperative communications has been proposed for single antennas to gain same benefits from MIMO, which helps to maintain the spatial diversity gain. The concept of cooperative communication is to enhance the wireless network by adding a relay as a third terminal to assist the direct communication. The use of relay as an intermediate terminal helps to increase the probability of detection. In this report, we analyze the detection probability in cognitive radio networks (CRNs) over correlated Nakagami-m fading channel assisted by amplify-and-forward (AF) cooperative networks using orthogonal space-time block codes (OSTBCs). We evaluate the impact of correlation in channel on the spectrum sensing performance in CRNs. We calculate the closed-form expressions of the detection probability, false alarm probability and probability of miss detection in correlated non-identical Nakagami-m fading channels. Moreover, we present a set of complementary receiver operating characteristics (ROC) curves for different scenarios to describe the effect of antenna correlation on the spectrum sensing performance of CRNs.