Measures of the spectrum utilization

In this paper, we summarize the known definitions of the spectrum utilization and discuss their applicability to existing radio services and their practical usefulness. An important parameter that limits the full utilization of the available radio spectrum is the non-uniformity of the user density. We illustrate that when users are clustered in small areas, the available spectrum resources in that area actually shrink. This leads to viewing the spectrum availability as a random process that changes with time and space. The randomness of the spectrum availability is rooted in the randomness in the topology and demography of the service area