Effect of Spectrum Sensing Errors on the Performance of OFDM-Based Cognitive Radio Transmission

The effect of spectrum sensing errors on the performance of cognitive radio transmission based on orthogonal frequency division multiplexing is evaluated by deriving analytical expressions for the average capacity and the average bit error rate as functions of different spectrum sensing parameters and data transmission parameters in the Rayleigh fading channels. Both the case with carrier frequency offset and the case without carrier frequency offset are considered. Numerical results are presented to show that spectrum sensing errors cause significant performance degradation and that the amount of performance degradation depends on the specific values of sensing and transmission parameters. In particular, the performance degradation caused by the primary user interference is more sensitive to the interfering amplitude and the number of subcarriers than to the probability of detection in spectrum sensing, the interfering frequency and the availability of the licensed band. Numerical results also show that the primary user interference caused by the sensing errors is dominant for small to medium values of the operating signal-to-noise ratio, while the inter-carrier interference caused by carrier frequency offset is dominant for large values of the operating signal-to-noise ratio.