Cognitive radio spectrum sensing

Cognitive radio (CR) is a radio technique that aims to utilize radio spectrum more efficiently by intelligently exploiting licensed spectrum. In this paper first will detect presence of primary user in spectrum band all this is done by periodically frequency band sensing. Secondly role of CR is to perform spectrum sharing where it assigns unused spectrum to secondary user (SU). Technique used to find the presence of primary user (PU) is energy detection technique and here we compare the output of energy detector with a threshold which then depends on noise floor and signal is detected. Here we use power spectral density, which describes how the power of a signal is distributed over different frequencies. We make use of MATLAB software to detect the user's power spectral density (PSD) of received signal at different SNR values. The receiver is used to distinguish the empty slots for use of secondary users.