Abstract:

We have obtaiend the “SNR Wall”, which is induced by noise uncertainty, of the energy detector over multipath fading channels in the cognitive radio. The robust detection model under noise uncertainty is built up. By finding the statistically averaged probability of robust detection over the fading distribution, the closed-form expression for detection probability is derived by making a proper approximation and transformation of the complex integral expression. Then, the SNR Wall is acquired by synthesizing the expressions for the detection and false alarm probability and eliminating the detection threshold. Analytical and simulation results show that the SNR Wall of energy detection over fading channels is related to the noise uncertainty, and increases dramatically with the rising of the target detection probability as well. Therefore, the SNR wall of the energy detector becomes very large when a high target probability of detection is required, and the energy detector is not applicable to the cognitive radio with a small received SNR.

Key words: cognitive radio, energy detection, multipath fading, SNR wall