Sidelobe Suppression for Non-systematic Coded UW-OFDM in Cognitive Radio Networks

Abstract

In this paper, a novel non-contiguous non-systematic<br><br>coded unique word (UW)-OFDM system is proposed to opportunistically<br><br>transmit data on the spectrum holes available in a<br><br>cognitive radio network. In such a system, the spectral sidelobes<br><br>of the active subcarriers interfere with the adjacent spectral band<br><br>used by the primary system. In the proposed scheme, the code<br><br>generator matrix of the UW-OFDM is designed to suppress the<br><br>sidelobes. So, there is no need to add any extra processing to the<br><br>transmitter for suppressing sidelobes. The derived code generator<br><br>matrix is optimum in the sense of being matched to the best linear<br><br>unbiased estimator and to the linear minimum mean square error<br><br>data estimators. The achieved sidelobe suppression is a function<br><br>of the number of transmitted data symbols. Simulation results<br><br>show that by a slight decrease in the number of transmitted data<br><br>symbols, the sidelobes power can be suppressed to zero.