Effect of OFDM in Cognitive Radio: Advantages & Issues

Cognitive Radio technology allows the unlicensed users to access the free licensed frequency band opportunistically to address the problem of the scarcity of unlicensed radio spectrum and for better utilization of the licensed radio spectrum. There was some problem in the cognitive radio systems such as Inter Symbol Interference and low data rate. To achieve the higher data rate and reduce the problem of Inter Symbol Interference, the Orthogonal Frequency Division Multiplexing modulation scheme has been used in cognitive radio systems. Basically OFDM modulation scheme transfers the data over multiple low rate subcarriers which are orthogonal to each other rather than single high rate carrier in conventional cognitive radio networks. It proves advantageous as it reduces the Inter-Symbol Interference, helps in spectrum sensing and also provides the interoperability. However it causes Peak-to-Average Power Ratio and reduces the spectral efficiency of OFDM based CR systems. In this technical paper various advantage of OFDM based cognitive radio and two major issues are also discussed along with various techniques to handle the PAPR problem.