A blind GLRT-based approach for OFDM spectrum sensing in the presence of I/Q imbalance

We investigate the problem of blind spectrum sensing at a secondary user of an orthogonal frequency-division multiplexing primary signal impaired by transmit I/Q imbalance. We derive a simple closed-form expression for the generalized likelihood ratio test as a function of the received signal only, i.e. without requiring any knowledge of the channel response, noise statistics, or I/Q imbalance parameters. Our results demonstrate that the primary signal´s correlation properties introduced by transmit I/Q imbalance can be exploited in a blind fashion at the secondary user to enhance the detection probability compared to the conventional energy detector.