Impact of primary user activity patterns on spatial spectrum reuse opportunities

Activity patterns of primary users have significant influence on the opportunities for secondary use of spectrum. In this paper we explore this impact in terms of spatial spectrum reuse opportunities. More specifically, we model the primary user activity as a Semi-Markov ON/OFF process with varying distributions of holding times of ON and OFF states. We have used realistic holding time distributions obtained from extensive measurement campaigns. These activity patterns are combined with a collection of primary user transmitter locations, based on a real deployed cellular network. Based on these, we study the impact of activity model parameters on opportunities of spatial spectrum reuse. The results indicate that for the scenarios studied here the overall duty cycle defined by the activity pattern plays the key role also in determining spatial spectrum opportunities. We also discuss applications of the obtained results, including development of lightweight models for occurrences of spectrum opportunities over both time and space.