Impact of Primary Users Duty Cycle on Optimum Secondary Users in Cognitive Radio Systems

Abstract

In a cognitive radio (CR) system, an achievable throughput of secondary users (SU) primarily depends on the activity level of primary users (PU) in the channels. More the PU are active in the channels, lesser the opportunity of SU transmission. Protecting the PU from a harmful interference introduced by SU is also a challenging task specifically when multiple PU and SU exist in the system. The trade-off between SU sum throughput and PU occupancy level has been thoroughly analysed considering a zero interference tolerance of an interweave CR system. PU activity level in the channel is measured in terms of duty cycle (DC). The interplay between DC of PU and throughput of SU is presented here for Poisson and binomial distribution based SU arrival processes. The results identify the opportunistic channels when SU aims a particular sum throughput and find the optimal numbers of SU in the channels for various DC.