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Sensing of OFDM Signals in Cognitive Radio Systems with Time Domain Cross-Correlation
Weiyang Xu 한국전자통신연구원 2014 ETRI Journal Vol.36 No.4
This paper proposes an algorithm to sense orthogonalfrequency-division multiplexing (OFDM) signals incognitive radio (CR) systems. The basic idea behind thisstudy is when a primary user is occupying a wirelesschannel, the covariance matrix is non-diagonal because ofthe time domain cross-correlation of the cyclic prefix (CP). In light of this property, a new decision metric thatmeasures the power of the data found on two minordiagonals in the covariance matrix related to the CP isintroduced. The impact of synchronization errors on thesignal detection is analyzed. Besides this, a likelihood-ratiotest is proposed according to the Neyman–Pearsoncriterion after deriving probability distribution functionsof the decision metric under hypotheses of signal presenceand absence. A threshold, subject to the requirement ofprobability of false alarm, is derived; also the probabilitiesof detection and false alarm are computed accordingly. Finally, numerical simulations are conducted todemonstrate the effectiveness of the proposed algorithm.