Statistical analysis of secondary users throughput for OFDMA cognitive radio networks

Cognitive radio systems are a smart approach to solve the problem of under-utilized spectrum of the licensed primary users (PUs). In order to gain a better quantitative insight of such systems, having a precise and comprehensive mathematical model of system throughput is vital. In this paper, we consider a set of PUs that are distributed in space based on Poisson point process (PPP) and demand for available spectrum. We determine the effect of these demands on the throughput of a single sensing secondary user (SU) under various channel requesting distributions and fading environment. In this context, we analytically derived the SU throughput in the presence of mutual interference due to imperfect detection of the SU in an OFDMA-based cognitive radio system. Moreover, the asymptotic behavior of the primary network is analytically studied under the asymptotic conditions such as higher traffic load and increasing transmit power. The results are critically investigated, formulated as theorems and compared with simulations. It is observed that analytical and simulation results are in perfect agreement. Furthermore, it is shown that with the increase in primary network transmit power, the average throughput of the SU increases and converges to a limit point. It is also proved that with the increase in primary network traffic load, the SU throughput decreases and converges to a limit point. Numerical results verify the validity of our model in capturing the effects of system specifications such as the channel requesting distributions and the traffic load on the SU throughput.