Level crossing rates of interference in cognitive radio networks

The future deployment of cognitive radios (CRs) is critically dependent on the fact that the incumbent primary user (PU) system must remain as oblivious as possible to their presence. This in turn heavily relies on the fluctuations of the interfering CR signals. In this letter we compute the level crossing rates (LCRs) of the cumulative interference created by the CRs. We derive analytical formulae for the LCRs in Rayleigh and Rician fast fading conditions. We approximate Rayleigh and Rician LCRs using fluctuation rates of gamma and scaled noncentral x² processes respectively. The analytical results and the approximations used in their derivations are verified by Monte Carlo simulations and the analysis is applied to a particular CR allocation strategy.