Interference and Deployment Issues for Cognitive Radio Systems in Shadowing Environments

摘要

n this paper we describe a model for calculatingthe aggregate interference encountered by primary receivers inthe presence of randomly placed cognitive radios (CRs). We showthat incorporating the impact of distance attenuation and lognormalfading on each constituent interferer in the aggregate, leadsto a composite interference that cannot be satisfactorily modeledby a lognormal. Using the interference statistics we determine anumber of key parameters needed for the deployment of CRs.Examples of these are the exclusion zone radius, needed to protectthe primary receiver under different types of fading environmentsand acceptable interference levels, and the numbers of CRs thatcan be deployed. We further show that if the CRs have aprioriknowledge of the radio environment map (REM), then a muchlarger number of CRs can be deployed especially in a high densityenvironment. Given REM information, we also look at the CRnumbers achieved by two different types of techniques to processthe scheduling information.