Real-time spectrum sensing with precise accuracy is the most important step to establish cognitive radio networks (CRNs). Detecting the presence of primary users (PUs) that use DS-CDMA (Direct sequence code division multiple access) technique is a challenge for the secondary users (SUs) in CRNs. DS-CDMA transmissions with very low signal to noise ratio (SNR) results in a signal hidden below the noise level, therefore, the existing classic detection methods are not effective enough to sense the signals. In this paper, a method is proposed to resolve this challenge. The proposed method based on fluctuation of correlation estimators searches on a specific frequency band and detects primary user's signals. Simulation results show that the sensing performance of the method is better than other conventional schemes for dealing with DS-CDMA users. Manuscript profile